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FGS Bulletin 68 : Main Report

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Title:
FGS Bulletin 68 : Main Report
Creator:
Arthur, J. D.
Publication Date:
Copyright Date:
2008
Language:
English

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Subjects / Keywords:
Town of Suwannee ( local )
City of Ocala ( local )
City of Tampa ( local )
City of Brooksville ( local )
Charlotte County ( local )
Gulf of Mexico ( local )
Aquifers ( jstor )
Limestones ( jstor )
Geological surveys ( jstor )
Sediments ( jstor )
Geology ( jstor )

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Source Institution:
University of Florida
Holding Location:
University of Florida
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The author dedicated the work to the public domain by waiving all of his or her rights to the work worldwide under copyright law and all related or neighboring legal rights he or she had in the work, to the extent allowable by law.

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FLRD WATE MANAGMN DISRIC







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FLOIDA DEARTEN OF ENIRNMNAL PROECIO
FORIDA GOGIAL SUVYBLETNN.6

Prprdi oprto ihteSuhws lrd ae aaeetDsrc











FLORIDA DEPARTMENT OF ENVIRONMENTAL PROTECTION
Michael W. Sole, Secretary



LAND AND RECREATION
Bob G. Ballard, Deputy Secretary



OFFICE OF THE FLORIDA GEOLOGICAL SURVEY
Walter Schmidt, State Geologist and Director



ADMINISTRATIVE AND GEOLOGICAL DATA MANAGEMENT SECTION
Jacqueline M. Lloyd, Assistant State Geologist


David Arthur, Computer Programmer Analyst
Traci Billingsley, Administrative Assistant
Paulette Bond, Professional Geologist
Doug Calman, Librarian
Brian Clark, Environmental Specialist
Jeff Erb, Systems Programmer
Jessie Hawkins, Custodian


Leslie Knight, Administrative Assistant
Anthony Miller, Environmental Specialist
Sarah Ramdeen, Computer Program Analyst
Ginger Rinkel, Secretary Specialist
Frank Rupert, Professional Geologist
Carolyn Stringer, Management Analyst


GEOLOGICAL INVESTIGATIONS SECTION
Thomas M. Scott, Assistant State Geologist


Ken Campbell, Professional Geologist
Brie Coane, Geologist
Rick Green, Professional Geologist
Eric Harrington, Engineering Technician
Laura Hester, Laboratory Technician
Ron Hoenstine, Professional Geologist Supervisor
Jessie Hurd, Laboratory Technician
Michelle Ladle, Laboratory Technician


Patrick Madden, Laboratory Technician
Harley Means, Professional Geologist
Mike Nash, Laboratory Technician
David Paul, Professional Geologist
Dan Phelps, Professional Geologist
Guy Richardson, Engineering Technician
Wade Stringer, Engineering Specialist
David Wagner, Laboratory Technician
Christopher Williams, Geologist


HYDROGEOLOGY SECTION
Jonathan D. Arthur, Assistant State Geologist (Acting Director)


Rick Copeland, Professional Geologist
Adel Dabous, Environmental Specialist
Rodney DeHan, Senior Research Scientist
Scott Barrett Dyer, Environmental Specialist
Cindy Fischler, Professional Geologist


Lisa Fulton, Environmental Specialist
Tom Greenhalgh, Professional Geologist
Nick John, Geologist
Clint Kromhout, Professional Geologist
Amber Rainsford, Environmental Specialist









STATE OF FLORIDA
DEPARTMENT OF ENVIRONMENTAL PROTECTION
Michael W. Sole, Secretary



LAND AND RECREATION
Bob G. Ballard, Deputy Secretary



FLORIDA GEOLOGICAL SURVEY
Walter Schmidt, State Geologist andDirector



BULLETIN NO. 68



HYDROGEOLOGIC FRAMEWORK OF THE SOUTHWEST FLORIDA
WATER MANAGEMENT DISTRICT


By



Jonathan D. Arthur, Cindy Fischler, Clint Kromhout,
James M. Clayton, G. Michael Kelley, Richard A. Lee, Li Li,
Mike O'Sullivan, Richard C. Green, and Christopher L. Werner


Published for the

FLORIDA GEOLOGICAL SURVEY

Tallahassee, Florida

in cooperation with the

SOUTHWEST FLORIDA WATER MANAGEMENT DISTRICT


2008

























*4i~~ic


Water Management District












Printed for the
Florida Geological Survey
Tallahassee
2008

ISSN 0271-7832

















In memory of the spirited life and geoscience
contributions of Rick Lee (1956 2007)






































































































Lv







PREFACE


A


The Florida Geological Survey/Florida Department of Environmental Protection is publishing
as its Bulletin 68, the Hydrogeologic Framework of the .Sinhi' e\t Florida Water Management
District. The report summarizes a multi-year study of the three-dimensional framework of
southwestern Florida's hydrogeology, with a focus on the subsurface distribution of aquifer
systems and geologic units comprising these systems. As groundwater resources in Florida
experience increased stress due to rapid population growth, an understanding of the aquifer
systems is invaluable to environmental managers, scientists, planners and the public as decisions
are made regarding use, protection and conservation of these vulnerable resources. The FDEP-
FGS is pleased to have had the opportunity to partner with the Southwest Florida Water
Management District to complete this report.



State Geologist and Director
Florida Geological Survey
Florida Department of Environmental Protection






































































































vi










TABLE OF CONTENTS



A abbreviations, acronym s and conversions......................................................................... ....................xi
A ck n ow ledg em ents ..................................................................................... ............................. ............ x ii
In tro d u ctio n .. ...........................................1.... ............ .... ............ .... ............ .... ............ .... ... ........ ....... 1
B background ...................... .......................................... .. ... ........... ..... .... ............... 1
Purpose and scope ..... ................ .. ....... ....... ... .. ............ ..... .................. .. ........... .... ... 1
Stu d y area ....................... ................................................................ ........... ...................... 2
Previous investigations ................................................................ 2
Physical setting ............... ................................................................... 5
Geology ...... ...... ..... ........... ........................... ................. 5
S tru ctu re ........................... .. .................................... .................. .......................... ....... ........... .. 7
G eom orphology ........................................................................... ........................ ........ .. ....... 11
Physiographic provinces and features............................................. ..... ................. .... .................. 11
Sinkholes ................ ........ ............ ..................................................... .... ........... 15
Springs ......................... .................... 15
Hydrogeology .......... .. .............................................................. 17
Methods ....................................... 20
Sam ple description ................ ............................................ ..................................... ...... ..................... 20
D elineation of boundaries .................................. ..................................................................... .......... 2 1
Form ations/M em bers ............................................... ............... ............. .. ............... ..... 21
A quifer system s ............... ..................................................................2 1
Cross-section construction ................................... ..................................................................... ........22
Topography ............... .......... ............................ ......... 22
L ith ology ...................................................................................... ................. ................... . .. ... 24
G am m a-ray logs .......................................................... ... ......... ............................ 24
A quifer sy stem s ..................................................................................................................... 24
M ap develop ent and data m anagem ent .......................................................................... ...................24
Map interpolation and spatial accuracy ................................................... .................... 27
C ontour interval selection ....................................................... .................. ...................... 30
Stratigraphy ............... ........ .......................................... 30
L ith ostratig raphy ................................................................................................................... ........... 30
Introduction ................................................................................................................................... 30
Eocene Series ..................................................................................... ...................................... 30
Oldsm ar Form action ............. .... .......................... ................ ............ ..... ................ 30
A v on P ark F orm action ................................................................................................ ... 3 1
O cala L im stone ................................................... ......................... ................................. 34
Oligocene Series ........................................ 37
Suw annee L im stone ............................................................... 37
O ligocene-Pliocene Series ..................................................................................... .......................40
H aw thorn G group ................................................... .................................................................... 40
A rcadia Form action ................................ ................................................................................ 40
N ocatee M em b er ....................................................................................................................... 4 3
Tam pa M em ber ........................................................................ ............ .......................... 43
"V enice C lay" ..................... ...... ......... ................................. ................................. 45
Peace River Formation .................... ................ ......................................... 45
Bone Valley Member ............................................. .......... ...... .................... 48









TABLE OF CONTENTS (CONTINUED)

H aw thorn G roup (undifferentiated) ........................................................................ ................ 48
Pliocene and younger Series .................................................. .................................. .................... 49
Post-H aw thorn G group sedim ents .......................... ..... ........ .... ...... ................... ... ................49
Tamiami Formation................................. ......... 50
C yp ressh ead F orm action ................................................................................ ......................... 50
C aloosahatchee Form action ......................................................................................................... 50
Fort Thompson Formation ................. ........... ....... .......... .............................. 51
H ydrostratigraphy ............................................... ...................................................... .................... 52
Introduction ....................... ................................................................................ ...................... 52
H ydrogeological properties ...................................................................................... ..... ................ 52
Surficial aquifer system ................. ............. .... ................ 53
Intermediate aquifer system/intermediate confining unit ...................................... ................ 57
F loridan aqu ifer sy stem ....................................................................................................................... 66
M iddle Floridan confining unit........................ ......................... ............................................. 75
Su m m ary ................... ........ .................. ......... ............................................... ......... . ..... 7 9
R eferen ce s ........... .... .... ..... ....................................... ................................ ........... ................. 8 1



FIGURES

Figure 1. Study area. .................................... .. .. .................. ................ ...... .................... ... 4
Figure 2. G eologic m ap of study area ................................................................................................ 6
Figure 3. Structural features within the study area. .......................................... ............................. 8
Figure 4. Environmental geology of the study area ..... ............. ......... ..................... 9
Figure 5. Shaded relief topography of the study area................................. ............... 12
Figure 6. G eom orphology of the study area .......................................................................................... 13
Figure 7. Shaded topographic relief of the southern extent of the Lake Wales Ridge. .......................... 16
Figure 8. Generalized correlation between lithostratigraphic units and the surface of the FAS.............23
Figure 9. Explanation (legend for cross sections).................................... ............................................ 25
Figure 10. Characteristic gam m a-ray log responses. ........................................................... ................. 26
Figure 11. Helicostegina gyralis, a foraminifer common within the Oldsmar Formation. .................... 32
Figure 12. Selected diagnostic fossils common within the Avon Park Formation................................ 33
Figure 13. Selected diagnostic fossils within the Ocala Limestone.................... .................... 35
Figure 14. Selected diagnostic Suwannee Limestone fossils........................................ ................ 38
Figure 15. Diagnostic foraminifera in Hawthorn Group units........ ..................................................41
Figure 16. Assemblage of typical Bone Valley Member fossils ....................... .. ... ... ............. 46
Figure 17. Characteristic Ft. Thompson Formation fossils.................................................................51
Figure 18. Soil perm ability of study area ......................................................... ................. ..................... 56
Figure 19. Statistical summary of SAS transmissivity data................................................................58
Figure 20. Statistical summary of SAS specific yield data................................... .............. 58
Figure 21. Statistical summary of SAS horizontal hydraulic conductivity data................................... 59
Figure 22. Statistical summary of SAS vertical hydraulic conductivity data..................................... 59
Figure 23. Approximate extent of IAS/ICU permeable zones........ ...................................................60
Figure 24. Statistical summary of IAS/ICU transmissivity data......................................................63
Figure 25. Statistical summary of IAS/ICU storativity data.................................................................. 63
Figure 26. Statistical summary of IAS/ICU leakance data........................................... ................ 64









FIGURES (CONTINUED)


Figure 27. Statistical summary of IAS/ICU horizontal hydraulic conductivity data................................ 64
Figure 28. Statistical summary of IAS/ICU vertical hydraulic conductivity data................................ 65
Figure 29. Statistical summary of IAS/ICU total porosity data............................................... 65
Figure 30. Potentiometric surface of the Floridan aquifer system, September, 2005............................... 68
Figure 31. Floridan aquifer system overburden thickness................................................ .....................70
Figure 32. Thickness of the Upper Floridan aquifer (includes non-potable) .......................................... 71
Figure 33. Statistical summary of UFA transmissivity data.................................................................. 72
Figure 34. Statistical summ ary of UFA storativity data........................................................................... 73
Figure 35. Statistical summary of UFA leakance data ................................... ................... 73
Figure 36. Statistical summary of UFA horizontal hydraulic conductivity data.................................. 74
Figure 37. Statistical summary of UFA vertical hydraulic conductivity data .................................. 74
Figure 38. Statistical summary of UFA total porosity data.............. .......................................75
Figure 39. Interpretations of the MFCU in the study area. ..................................................76
Figure 40. Statistical summary of MFCU vertical hydraulic conductivity data........................... .. 78
Figure 41. Statistical summary of MFCU total porosity data..................... .............. .............. 78


TABLES

Table 1. Units mapped in this study. Map types are structure contour (surface) and isopach (thickness) .. 3
Table 2. Generalized correlation chart for units mapped within study area ............................................ 19
Table 3. Summary ofkrige interpolation statistics for each map ......... ..................................................29


APPENDICES

Appendix 1. Commentary on Florida hydrostratigraphic nomenclature.....................................................99
Appendix 2. Explanation of revisions to FDEP-FGS Special Publication 28 aquifer definitions ......... 101


PLATES
1. Cross section locations
2. Wells used in this study
3. Closed topographic depressions in the study area
4. Cross section: A-A' Levy and Marion Counties
5. Cross section: B-B' Levy and Marion Counties
6. Cross section: C-C' Citrus and Sumter Counties
7. Cross section: D-D' Citrus and Sumter Counties
8. Cross section: E-E' Hemando, Sumter, and Lake Counties
9. Cross section: F-F' Hernando, Pasco, Sumter and Lake Counties
10. Cross section: G-G' Pasco, Sumter, and Polk Counties
11. Cross section: H-H' Pasco and Polk Counties
12. Cross section: I-I' Pinellas and Hillsborough Counties
13. Cross section: J-J' Pinellas and Hillsborough Counties
14. Cross section: K-K' Pinellas and Hillsborough Counties









PLATES (CONTINUED)


15. Cross section: L-L' Manatee, Hillsborough, and Polk Counties
16. Cross section: M-M' Manatee County
17. Cross section: N-N' Sarasota and Manatee Counties
18. Cross section: 0-0' Sarasota County
19. Cross section: P-P' Charlotte County
20. Cross section: Q-Q' Polk and Osceola Counties
21. Cross section: R-R' Hillsborough and Polk Counties
22. Cross section: S-S' Hillsborough and Polk Counties
23. Cross section: T-T' Manatee, Hardee, and Highlands Counties
24. Cross section: U-U' Manatee, Hardee, and Highlands Counties
25. Cross section: V-V' Manatee, DeSoto, Hardee, and Highlands Counties
26. Cross section: W-W' Sarasota, DeSoto, and Highlands Counties
27. Cross section: X-X' Sarasota, DeSoto, Highlands, and Glades Counties
28. Cross section: Y-Y' Charlotte and Glades Counties
29. Cross section: Z-Z' Levy, Citrus, Pasco, and Hernando Counties
30. Cross section: AA-AA' Marion, Sumter, Hernando, and Pasco Counties
31. Cross section: BB-BB' Pinellas County
32. Cross section: CC-CC' Hillsborough and Manatee Counties
33. Cross section: DD-DD' Hillsborough and Manatee Counties
34. Cross section: EE-EE' Lake, Polk, Hardee, DeSoto, and Charlotte Counties
35. Cross section: FF-FF' Polk, Highlands, and Glades Counties
36. Cross section: GG-GG' Manatee, Sarasota, and Charlotte Counties
37. Cross section: HH-HH' Manatee, Sarasota, and Charlotte Counties
38. Avon Park Formation surface
39. Ocala Limestone surface
40. Ocala Limestone thickness
41. Suwannee Limestone surface
42. Suwannee Limestone thickness
43. Hawthorn Group surface
44. Hawthorn Group thickness
45. Arcadia Formation surface
46. Arcadia Formation thickness
47. Nocatee Member of the Arcadia Formation surface
48. Nocatee Member of the Arcadia Formation thickness
49. Tampa Member of the Arcadia Formation surface
50. Tampa Member of the Arcadia Formation thickness
51. Peace River Formation surface
52. Peace River Formation thickness
53. Bone Valley Member of the Peace River Formation surface
54. Bone Valley Member of the Peace River Formation thickness
55. Surficial aquifer system thickness
56. Intermediate aquifer system/intermediate confining unit surface
57. Intermediate aquifer system/intermediate confining unit thickness
58. Floridan aquifer system surface
59. Middle Floridan confining unit surface













ASE
BLS
CFHUD II
CTD
DEM
District
FAS
FDCA
FDEP
FGS
IAS/ICU
IDW
IP/FMNH
Kh
Kv
L
LFA
LIDAR
MFCU
MSL
RMS
ROMP
S
SAS
SWFWMD
SY
T
UFA
USGS

Y


ABBREVIATIONS, ACRONYMS AND CONVERSIONS

average standard error
below land surface
Second Ad Hoc Committee on Florida Hydrostratigraphic Unit Definitions
closed topographic depression
digital elevation model
Southwest Florida Water Management District
Floridan aquifer system
Florida Department of Community Affairs
Florida Department of Environmental Protection
Florida Geological Survey
intermediate aquifer system/intermediate confining unit
inverse distance weighted
Invertebrate Paleontology, Florida Museum of Natural History
horizontal hydraulic conductivity
vertical hydraulic conductivity
leakance
Lower Floridan aquifer
light detection and ranging
Middle Floridan confining unit
mean sea level
root mean squared
Regional Observation and Monitor Well Program
storativity
surficial aquifer system
Southwest Florida Water Management District
specific yield
transmissivity
Upper Floridan aquifer
United States Geological Survey
approximately
gamma


Multiply By To obtain
cubic foot (ft3) 0.0283 cubic meter (m3)
foot (ft) 0.305 meter (m)
foot per day (ft/d) 3.53x10-4 centimeter/second (cm/s)
foot squared per day (fl2/d) 0.0929 meter squared per day (m2/d)

gallon (gal) 3.79x10-3 cubic meter (m3)
gallon (gal) 113.79 liter (L)
gallon per minute (gal/min) 6.32x10-5 cubic meter per second (m3/s)
inch (in) 25.4 millimeter (mm)
mile (mi) 1.609 kilometer (km)









ACKNOWLEDGEMENTS


This research was a cooperative effort between the Florida Department of Environmental Protection
(FDEP) Florida Geological Survey (FGS) and the Southwest Florida Water Management District
(SWFWMD). Special thanks are extended to David L. Moore, SWFWMD Executive Director and Dr.
Walter Schmidt, FDEP-FGS Director and State Geologist for administrative and financial support.
Essential geology and hydrogeology data-collection programs in the SWFWMD, FDEP-FGS and the U.S.
Geological Survey (USGS) have made the development of this comprehensive report possible. Numerous
individuals and countless hours of well drilling and logging, aquifer and laboratory testing, database
development and management, lithologic descriptions, formation boundary determinations, surface
modeling, and map/cross section production have contributed to the development of this report.

The authors express their appreciation to the numerous individuals for their insightful review of the
manuscript and plates. From the FDEP-FGS, these individuals include Carol Armstrong, Ken Campbell,
Jackie Lloyd, Frank Rupert, Dr. Walter Schmidt, Dr. Tom Scott; from SWFWMD, Ron Basso, Michael
Beach, Marty Clausen, Michael Gates, Tony Gilboy, Jason LaRoche, John Parker, Robert Peterson and
Donald Thompson. Ken Campbell and Dr. Tom Scott are thanked for their contributions and discussions
regarding the lithostratigraphy and hydrostratigraphy of the study area. Discussions with John J. Hickey,
Rick Spechler, Dr. Tom Scott and Dr. Sam Upchurch helped refine our understanding of the
hydrostratigraphy of the region. Doug Rapphun also contributed to our knowledge of the hydrogeology
in the region.

The authors also gratefully acknowledge those staff of the FDEP-FGS who participated in this project.
Lance Johnson and Paula Polson provided assistance with cross-section development. Surface
interpolations during early phases of the project were completed by Bill Pollock, Amy Graves, John
Marquez and Andrew Rudin. Developers of the database for this project included Mark Groszos, Marco
Cristofari and Rob Stoner. Data management support included the assistance of Jackie Bone, Patricia
Casey, Lance Johnson, Natalie Sudman, and Holly Tulpin. Lithologic descriptions of numerous borehole
samples were completed by Alan Baker, Jim Cichon, Erin Dor, Kris Esterson, Mabry Gaboardi, Diedre
Lloyd, Matt Mayo, Sarah Ramdeen and Holly Williams. Many of the photos and photomicrographs of
fossils presented in this report are provided courtesy of Roger Portell and Sean Roberts (Invertebrate
Paleontology, Florida Museum of Natural History), Dr. Jonathan Bryan (Okaloosa-Walton Community
College) and Frank Rupert. Dr. Rick Copeland was helpful with regard to discussions of quality
assurance of hydrogeologic data and presentation of descriptive statistics.






BULLETIN NO. 68


HYDROGEOLOGIC FRAMEWORK OF THE SOUTHWEST
FLORIDA WATER MANAGEMENT DISTRICT


By Jonathan D. Arthur, (P.G. #1149), Cindy Fischler (P.G. #2512), Clint Kromhout (P.G. #2522),
James M. Clayton, (P.G. #381), G. Michael Kelley (P.G. #249), Richard A. Lee (P.G. #956), Li Li,
Mike O'Sullivan (P.G. #2468), Richard C. Green (P.G. #1776), and Christopher L. Werner (P.G. #2366)


INTRODUCTION

Background

Groundwater comprises approximately 85
percent of the total water-resource supply in the
Southwest Florida Water Management District
(SWFWMD), where existing water demands are
on the order of 435 billion gallons per year
(Southwest Florida Water Management District,
2006a). By 2025, the population of the region is
expected to increase more than 30 percent,
placing further demands on water resources.
Development of alternative water supplies and
continued water-resource management and
conservation are critically important toward the
sustainability of groundwater resources within
the aquifer systems of southwest Florida. These
practices, however, require the accumulation,
management and interpretation of
hydrogeological data.

In the mid-1990's, the SWFWMD and the
Florida Department of Environmental Protection
- Florida Geological Survey (FDEP-FGS)
entered into a cooperative project to develop a
series of geologic and hydrogeologic cross
sections throughout the 16-county SWFWMD
region. The project was designed to characterize
the relation and extent of lithostratigraphic1 and


hydrostratigraphic2 units within the region with
an emphasis on use of hydrogeologic data
collected by the District's Regional Observation
and Monitor-well Program (ROMP). This project
was later expanded to include production of
surface and thickness maps of the units
represented in the cross sections.

To accomplish the goal of the regional cross
section project, the District was divided into four
study areas (three project phases): Phase IA
includes Pinellas and Hillsborough Counties;
Phase IB includes Manatee, Sarasota, Hardee,
DeSoto and Charlotte Counties; Phase II includes
the northern part of the District, from Levy,
Marion and Lake to Pasco Counties; and Phase
III includes the southeastern part of the District,
encompassing all areas not covered in Phases IA,
IB and II. Interim reports were published for
Phase IA and II (Green et al., 1995 and Arthur et
al., 2001a, respectively). Rather than separately
publishing reports for the remaining phases, the
cross sections are incorporated in this report.

Purpose and Scope

The purpose of this study is to refine the
hydrogeological framework of the region to
facilitate science-based decision making with
regard to the protection, conservation and
management of southwest Florida's water


1 Lithostratigraphic units are laterally extensive
sequences of rocks and sediments reflecting unique
lithologic characteristics; each unit was deposited
within a generally similar paleo-environment during
a given period of time in Earth's history.


2 Hydrostratigraphic units include laterally extensive
sequences of rocks and sediments that are related by
hydrogeologic characteristics. Hydrostratigraphic
units may or may not correlate with lithostratigraphic
units.






FLORIDA GEOLOGICAL SURVEY


resources. Thirty-four cross sections have been
produced for this study (Plate 1). Each of the
cross sections illustrates regional
lithostratigraphy of Eocene through Pliocene
formations, lithology, mineralogy, gamma-ray
logs, topographic profiles and hydrostratigraphic
delineations. Although most of the data used to
construct the cross sections was taken from
wells drilled as part of ROMP (Gomberg, 1975),
borehole data (e.g., from cores, cuttings and
geophysical logs) from the FDEP-FGS and the
U.S. Geological Survey (USGS) were utilized to
fill in as many gaps as possible.

The mapping phase of the study facilitated
development of a new geologic and
hydrogeologic database, FGS Wells. Structure
contour (surface elevations) and isopach
(thickness) maps for all regionally extensive
lithostratigraphic and hydrostratigraphic units
within the District were then developed. The
maps include all units between land surface and
the top of the Middle Floridan confining unit
(Table 1).

Data from more than 1050 wells (including
offshore boreholes) serve as control for these
maps (Plate 2). In addition, synthetic wells were
used to provide lateral (edge) control during map
surface interpolation. These wells represent an
artificial stratigraphic record for a given location
based on interpolated elevations from existing
maps or cross sections. The new surface and
thickness maps presented herein were developed
using the ESRI geographic information system
(GIS) program ArcMAP (see Map Development
and Data Management, p. 24) for details on map
production. Each map includes the lateral extent
of each unit and locations of wells within the
study area that were used to interpolate surfaces
and thicknesses.

Study Area

Maps and cross sections produced for this
study cover the entire SWFWMD region (Figure
1). To facilitate present and future hydrologic
modeling and comparison of these maps to
adjacent Water Management Districts, a 10 mi
(16.1 km) wide buffer extending beyond the
District boundary was included in the study area


(Figure 1, Plate 2). Surface interpolation
techniques, such as kriging, can produce non-
representative contours along the margins of
mapped units. To address these undesirable
"edge effects," data from within a second 10 mi
(16.1 km) wide buffer zone was utilized. The
additional data helped stabilize surface
interpolations and contours, and allowed for a
more accurate delineation of the vertical and
lateral extents of certain mapped units. The
project study area, which covers approximately
14,340 mi2 (37,141 km2), does not include
wells within the second (outermost) buffer.

Previous Investigations

Numerous researchers have focused on the
regional geology and hydrogeology of southwest
Florida. Sub-Floridan aquifer system geology,
with an emphasis on pre-Cenozoic basement
geology, is presented in several papers including
Applin (1951), Applin and Applin (1965), Bass
(1969), Barnett (1975), Smith (1982) and
Chowns and Williams (1983). Arthur (1988)
and Heatherington and Mueller (1997) focus on
geochemistry of basement terrains, while Smith
and Lord (1997) summarize the tectonic and
geophysical aspects of the Florida basement.
Gohn (1988) and Randazzo (1997) provide
comprehensive overviews of Mesozoic and
Cenozoic geology of the Atlantic Coastal Plain,
including peninsular Florida. Mesozoic and
Cenozoic paleoceanographic and structural
evolution along the margin of the Florida
peninsula is presented in Hine (1997).

Selected early studies of Cenozoic and
younger formations include Applin and Applin
(1944), Cooke (1945), Puri and Vernon, (1964)
and Chen (1965). More recent stratigraphic
research on units in south and southwest Florida
has been completed by Miller (1986), Scott
(1988), McCarten et al. (1995), Brewster-
Wingard et al. (1997) and Cunningham et al.
(1998). Missimer (2002) focused on Oligocene
through Pliocene stratigraphic relationships in
the southernmost part of the present study area
(Charlotte County), as well as Lee and western
Collier Counties. Pliocene and younger
stratigraphy has been the focus of several studies






BULLETIN NO. 68


Table 1. Units mapped in this study. Map types are structure contour (SC) and isopach (I).

Lithostratigraphic Units Map types Hydrostratigraphic Units Map types

Hawthorn Group SC, I surficial aquifer system I
intermediate aquifer system /c,
Peace River Formation SC, I intermediateSC, I
intermediate confining unit
Bone Valley .
Bone Valley SC, I Floridan aquifer system overburden I
Member
Arcadia Formation SC, I Floridan aquifer system SC

Tampa Member SC, I Upper-Floridan aquifer system I

Nocatee Member SC, I Middle Floridan confining unit SC

Suwannee Limestone SC, I

Ocala Limestone SC, I
Avon Park Formation
SC


(e.g.,Evans and Hine, 1991; Scott,
Missimer, 2001).

Hydrogeologic framework studies that
the southwestern Florida region include


1997;


include
Gilboy


(1985), Johnston and Bush (1988), Miller (1986),
Ryder (1985) and Reese and Richardson (2008).
Maps depicting the thickness and extent of the
Floridan aquifer system (FAS), the "intermediate
aquifer" and intermediate "confining beds" include
Buono and Rutledge (1978), Wolansky et al.
(1979a), Wolansky et al. (1979b), Wolansky and
Garbode (1981), Corral and Wolansky (1984) and
Miller (1986). Allison et al. (1995) present a map
of the top of rock of the FAS in the Suwannee
River region, located along the northeast part of
the SWFWMD study area. Meyer (1989) provides
a comprehensive characterization of the
hydrogeologic framework of southern Florida.
Spechler and Kroening (2007) present a
comprehensive study of Polk County hydrology.
Reese (2000) and Missimer and Martin (2001)
present the hydrogeology and water quality of the
FAS in Lee, Hendry and Collier Counties.

Statewide hydrochemical characterizations of
the upper FAS have focused on aquifer-system
mineralogy and processes that led to observed
native groundwater chemistry (e.g., Plummer,


1977; Sprinkle, 1989), and hydrochemical facies
(Katz, 1992). Upchurch (1992) characterized not
only hydrochemical facies, but also naturally
occurring and anthropogenic constituents in the
FAS. Other studies that focused on regional
aspects of FAS hydrochemistry (i.e., salinity,
solute transport and dolomitization) include Back
and Hanshaw (1970), Cander (1994, 1995),
Hanshaw and Back (1972), Jones et al. (1993),
Maliva et al. (2002), Randazzo and Zachos
(1984), Sacks (1996), Sacks and Tihansky
(1996), Steinkampf (1982), Swancar and
Hutchinson (1995), Trommer (1993), and Wicks
and Herman (1994, 1996). Budd et al. (1993),
Budd (2001, 2002) and Budd and Vacher (2004)
have studied in detail the role of permeability,
compaction and cementation in FAS carbonates
of southwest Florida. An overview of surface-
water and groundwater hydrology is provided by
Wheeler et al. (1998). In contrast to these regional
characterizations, Tihansky (2005) identified the
complex relation between water quality,
groundwater flow patterns and structural
heterogeneity within the FAS in northeastern
Pinellas County by employing diverse
hydrogeological and geophysical analyses.

Hydrochemical studies of the intermediate
aquifer system/intermediate confining unit







FLORIDA GEOLOGICAL SURVEY


Explanation

SStudy Area US Interstate
Cities
Cities FL Turnpike
-- Rivers
Lakes US Highway
- Water Management Districts


Figure 1. Study area.


Study Area
0 5 10 20 30 40
Miles
0 5 10 20 30 40
== == Kilometers
Scale 1 1,750,000
Projection: Custom FDEP Albers

-J LDaytona Beach
i VDavtona Beach


Gulf
of
Mexico






BULLETIN NO. 68


include Joyner and Sutcliff (1976), Upchurch
(1992), Kauffman and Herman (1993), Broska
and Knochenmus (1996) and Torres et al.
(2001). Knochenmus (2006) characterizes the
water quality and hydraulic heterogeneity of the
intermediate aquifer system in the southern part
of the District. The study underscores that
previously defined "permeable zones" of this
aquifer system are hydraulically similar to
"semi-confining units" in the upper Floridan
Aquifer System. A statewide hydrochemical
assessment of the surficial aquifer system was
completed by Upchurch (1992).

Several groundwater flow models of the
SWFWMD region have been published (e.g.,
Ryder, 1985; Barcelo and Basso, 1993; Yobbi,
1996), most of which are discussed in the
comprehensive work of Sepulveda (2002),
wherein he developed a groundwater flow model
for peninsular Florida that includes the
Intermediate and Floridan aquifer systems.
Selected compilations of aquifer parameters on
which many of these models are based are
presented in Hydrogeological Properties, p. 52.


Physical Setting
Geology

Development of the Florida carbonate
platform primarily occurred during the Late
Cretaceous through middle Cenozoic and was
generally free of intermixed sands and clays.
Strong currents across northern Florida in a
feature broadly referred to as the Georgia
Channel System (Huddlestun, 1993) effectively
precluded transport and deposition of these
siliciclastics to the platform. During this period,
deposition of the Cedar Keys Formation,
Oldsmar Formation, Avon Park Formation,
Ocala Limestone, and the Suwannee Limestone
occurred. Huddleston (1993) proposed the
Georgia Channel System recognizing spatially
and temporally overlapping features (e.g.,
Suwannee Strait and Gulf Trough) proposed in
the literature that described paleotopography
(paleobathymetry) and associated paleocurrents.
Randazzo (1997) provides an overview of this


dynamic system and feature names.

During the Oligocene, the southern
Appalachians experienced uplift and erosion
(Scott, 1988). Southward transport and
deposition of ensuing siliciclastic sediments
began to fill the channel system, which allowed
ocean currents to transport sediments southward
across the well-developed carbonate platform.
As a result, some of the first siliciclastic
sediments in southern Florida carbonates appear
as sand lenses in the Lower Oligocene
Suwannee Limestone south of Charlotte County
(Missimer, 2002). The influx of siliciclastic
sediments, mixing with locally-formed
carbonates led to Late Oligocene through the
Early Pliocene deposition of the Hawthorn
Group (Scott, 1988; Missimer et al., 1994)
throughout most of Florida. In much of
peninsular Florida phosphate deposition
occurred yielding many economic phosphorite
deposits. This period of phosphogenesis is
described by Riggs (1979a, 1979b) and
Compton et al. (1993); [see Bone Valley
Member, p. 48, for more detail]. During the
Late Pliocene to Recent, sediment deposition
became even more siliciclastic dominant. Shell
beds were deposited along coastal areas and
migrated in response to sea-level fluctuations.
The geology and depositional environment of
lithostratigraphic units in the region are the
subject of numerous studies in southwestern
Florida; results of which are presented in the
lii~ai,,,,,i, ,,llihy section, p. 30, of this report.
From deposition of the Cedar Keys Formation
through Pliocene-Pleistocene shell beds, a
dynamic transition from carbonate to
siliciclastic-dominated depositional environments
is reflected.

The surface distribution of lithostratigraphic
units (Figure 2) in the study area is a function of
post-depositional influences ranging from
tectonic activity, platform stability, sea-level
changes and karst processes. For example, the
Avon Park Formation is the oldest exposed
lithostratigraphic unit in the study area (Figure
2). This Eocene unit gently dips southward
toward Charlotte County to depths exceeding
1500 ft (457.2 m) below land surface (BLS). In








FLORIDA GEOLOGICAL SURVEY


Geologic Map
0 5 10 20 30 40
i i Miles
0 5 10 20 30 Kilometers

Scale 1:1,750,000
Projection: Custom FDEP Albers

,i TQd,
Tod





I ''
* t1 '" ".*.^ s


Explanation u iQ.Q'-
D Study Area 6
- Water Management Districts I "
Stratigraphic Units r
Qbd Beach Ridge and Dune ,
Qh Holocene Sediments
SQu Undifferentiated Sediments\ .Ts,
STQd Dunes u "Q "
STQsu Shelly Pio-Pleistocene Sediments
TQu Undifferentiated Sediments
STQuc Reworked Cypresshead Sediments Qh
STap Avon Park Formation
STc Cypresshead Formation
STh Hawthorn Group (undifferentiated)
Tha Hawthorn Group, Arcadia Formation
Ti I Hawthorn Group, Arcadia Formation, Tampa Member Qh
The Hawthorn Group, Coosawhatchie Formation
Thp Hawthorn Group, Peace River Formation
SThpb Hawthorn Group, Peace River Formation, Bone Valley Member
STo Ocala Limestone
Ts Suwannee Limestone
STt Tamlaml Formation


Tc
Thpb'.-


Qu



Qu

':-Qu~~;


Gulf
of
Mexico


II
xx hi


Figure 2. Geologic map of study area (from Scott et al., 2001) depicting the uppermost mappable
units within 20 ft (6.1 m) of land surface.






BULLETIN NO. 68


general, the younger formations follow this
pattern, however, many are not observed
throughout the full extent of the study area (i.e.,
absence of the Peace River Formation
[Hawthorn Group] in the northern third of the
District). In the sections that follow, details of
the features and processes affecting the overall
geologic framework are discussed.

Structure

Numerous structural features affect the
thickness and extent of geologic units in the
study area (Figure 3). The oldest known
"basement" feature in the region is the Bahamas
Fracture Zone (Klitgord et al., 1983), which is
also referred to as the Jay Fault (Pindell, 1985).
This zone bisects the Florida peninsula basement
from Tampa Bay southeast to the Lake Worth
area on the east coast. Lithologic and
geophysical data suggest that this basement
feature represents an Early Mesozoic transform
fault that was important to the development of
the Gulf of Mexico. Christenson (1990),
however, suggests that based on assessment of
more recently acquired borehole geology and
magnetic anomaly data, the feature represents a
Triassic-Jurassic extensional rift margin with
little to no lateral offset. He proposes the name
"Florida Lineament" to describe this feature,
which coincides with the Jay Fault and the
Bahamas Fracture Zone across peninsular
Florida (Christenson, 1990; see feature "A" in
Figure 3).

The South Florida Basin (Applin and Applin,
1965; Winston, 1971) is a stratigraphic basin
that contributed to southward thickening of
Mesozoic and Early Cenozoic lithostratigraphic
units in the southern Florida peninsula (Figure
3). A possible successor basin, the younger
Okeechobee Basin (Riggs, 1979a) may have
contributed to south southeastward dipping of
Oligocene and older lithostratigraphic units
along the eastern margin of the study area
(Highlands and Glades Counties).

The influence of "basement" structures on
Cenozoic and younger stratigraphic units is
poorly understood. For example, an apparent
southeast plunging syncline ("B" in Figure 3)


trends from Sarasota to Hendry Counties in the
"sub-Zuni" (i.e., pre-Middle Jurassic) map
presented in Barnett (1975). Shallower
northwest-striking faults reported by Winston
(1996) occur in the same region. Maps of the
structural surface of Eocene rocks (Miller, 1986)
indicate a generally south-plunging trough
extending from central Charlotte County.
Deepening and thickening of units in the
Charlotte County region are observed in the
present study (see I l thiti,,,, Ii,,l'y, p. 30). The
Early Cretaceous "Broward Syncline" (Applin
and Appin, 1965; "C" in Figure 3) is located
approximately 20 mi (32 km) to the east of
feature "B" and has a generally parallel strike.
These inferred faults and basement relationships
warrant further study, especially given their
potential role in water quality and distribution of
permeable zones. Knowledge of the distribution
of low-permeability sediments beneath the FAS
is also important as potential sites for CO2
sequestration are explored.

The Ocala Platform ("D" in Figure 3) is the
most dominant feature in the central peninsular
region. Evidence of this platform is apparent in
the geologic map (Figure 2) where the Eocene
Avon Park Formation (Tap) and Ocala
Limestone (To) are exposed at or near land
surface. This feature is also evident in the
Environmental Geology composite map (Figure
4), which reflects lithologic and sediment types
within 10 ft (3.1 m) of land surface. Shallow or
exposed carbonate rocks in Levy, Marion, Citrus
and Sumter Counties reflect the influence of the
platform. This structure is not thought to be an
uplift (Winston, 1976) but rather a tectonically
stable area on which disconformable marine
sedimentation and differential subsidence has
occurred (Scott, 2001). It is also a major
controlling factor in the thickness and extent of
lithostratigraphic units in central and
southwestern Florida. As a result, this feature
also has a very significant effect on the
distribution of regional aquifer systems.

Remaining structural features are discussed
in this section from north to south. Several
northwest-trending faults, as well as orthogonal
fracture traces (or lineaments), have been
proposed within the Levy and Citrus County
area by Vernon (1951). It is possible that some







FLORIDA GEOLOGICAL SURVEY


Structural Features
0 5 10 20 30 40
0 5 10 20 30 40
Kilometers
r 1,. 1 FDEP Albers
Pr.:1..-:I,:.r, Cu~Ii:.m FDEP Albers


Gulf
of
Mexico


E


Explanation

I Study Area FG-2
SFault Groups

Plunging anticline *

SPlunging syncline "

Proposed Faults I \
--- Present Study (inferred) I
Sproul etal., 1972
Winston, 1996
Hutchinson, 1991 B Okeechobee
===. Christenson, 1990 Basin
Miller, 1986
Pride et al., 1966
Carr and Alverson, 1959
Vernon, 1951 C

Figure 3. Structural features within the study area. A Florida Lineament; B pre-middle
Jurassic plunging syncline inferred from Barnett's (1975) "sub-Zuni" map; C "Broward
Syncline;" D Ocala Platform; E Kissimmee Faulted Flexure; FG-1 fault group along strike
with fault inferred in present study; FG-2 group of reported faults possibly affecting subcrop
extent of the Ocala Limestone. U/D upthrown/downthrown block.









BULLETIN NO. 68


Gulf
of
Mexico


Explanation

I IStucl -,-
- Wat- I I,,5,.,,,,,r n,, -

Environmental Geology
Rock/Sediment Type
Clayey Sand
Dolostone
' Limestone
Limestone/Dolostone
::Med Fine Sand and Silt
Peat
Sandy Clay and Clay
Shelly Sand and Clay
Lake Okeechobee


I
iI'


S Environmental

Geology
0 5 10 2) j0 40
".,. iMiles

..:". ". 1':0 -10



CL.,."n Fu :.EP i. -,.,


)I
;:J


Figure 4. Environmental Geology of the study area (after Knapp, 1978; Scott, 1978; Scott, 1979;
Lane, 1980; Lane et al., 1980; Knapp, 1980; Deuerling, 1981). Lithotypes depicted in this map are

reported to occur less than or equal to 10 ft (3.0 m) from land surface.


~
:~:

~ ':~'=:

:.it

~~::: : ':'
:... ~"'::.': :1.--;


-I"''
-.. i'f
:.:.
r

~: .:

..: ':I?'"'':
':'
:
a .......
a
:. :
9\ _r; I... ;r.

:




~.~ .~~. i'


:


:
~: ::::.~
'

.:: ; 3-


'''

; :

ci ..
(; i
.i
;

~j..~,



: :.:~
;. .:.
:: .:::
::I


.:i ':':::j ::::i::
i :.)~:i' ~ ~






FLORIDA GEOLOGICAL SURVEY


of the inferred "offsets" in his study are due to
wells having encountered buried karst pinnacles
and paleo-sinks. Carr and Alverson (1959),
Pride et al. (1966), and Vernon (1951) report a
northwest trending normal fault(s) in
northwestern Polk County (fault group "FG-1",
Figure 3). Pride et al. (1966) suggest that the
fault affects not only the Avon Park Formation,
but also juxtaposes the Suwannee Limestone and
Ocala Limestone. Carr and Alverson (1959)
indicate that the fault penetrates Hawthorn
Group sediments as well. Both studies report
the northeast block of the inferred fault as the
upthrown side. In the present study, evidence
supports two possible northwest-trending faults
along the northeastern extent of the Suwannee
Limestone (Figure 3; see also Suwannee
Limestone, p. 37). Both faults are similar in
strike and offset direction (polarity) to fault
group "FG-1" in Figure 3. One of the offsets
proposed herein is a northwestern extension of a
fault proposed by Carr and Alverson (1959).

Faults affecting Middle and Upper Eocene
(e.g., Avon Park Formation and Ocala
Limestone) strata are proposed along the Polk-
Osceola County boundary (Pride et al., 1966;
Miller, 1986). The Kissimmee Faulted Flexure
(Vernon, 1951; "E" in Figure 3) occurs in the
same area and was originally considered a
wedge-shaped, fault-bounded block that had
been tilted and rotated, with beds containing
small folds and structural irregularities. Wells
that penetrate the feature contain variably thick
Pliocene-Miocene sediments that overly the
Avon Park Formation. Scott (1988) and Davis
et al., (2001) consider the Kissimmee Faulted
Flexure to be an Avon Park Formation
stratigraphic high with the Ocala Limestone and
Hawthorn Group sediments locally absent due to
erosion. Additional faults ("FG-2" in Figure 3)
affecting the subcrop extent of the Ocala
Limestone along the western margin of the
Flexure have also been proposed. Data
presented in this study support the
interpretations of Scott (1988) and Davis et al.,
(2001).

Further to the south in the vicinity of
Charlotte Harbor, a west-northwest trending
reverse fault penetrating a dolostone layer in the
Suwannee Limestone is proposed (Hutchinson,


1991). Maps presented herein do not lend
support to the inferred reverse fault. In the same
area, a series of northeast-trending lineaments
along the northern margin of Charlotte Harbor
(Michael Fies, personal communication, 2007)
coincide with anomalously high groundwater
temperatures in the upper FAS (Smith and
Griffin, 1977) suggesting a potential line of
further investigation (E. Richardson, written
communication, May, 2006). The "North Port
Fault" (Winston, 1996) strikes nearly coast-
parallel (northwest) across North Port and Punta
Gorda. Winston (1996) suggests that the
downthrown side may occur on the southwest
block, which more or less coincides with
thickening and deepening of several units
mapped in the present study (see
Ilig, ip,,,,b,,,!hy, p. 30, for further discussion).
South of the study area, west-northwest trending
normal and reverse faults offsetting Miocene
Hawthorn Group sediments on the order of 50 to
100 ft (15 to 30.5 m; vertical) are reported
(Sproul et al., 1972).

Evidence of some degree of vertical offset is
present within cores in the study area; however,
there is insufficient proximal well control to
delineate faulting. Core from W-16913 (ROMP
5), for example, contains abundant high-angle
fractures and slickensides that make some
lithostratigraphic unit surfaces obscure.
Regarding hydrostratigraphic units, brecciated
and fractured zones in core from W-17392
(ROMP 13) contribute to difficulties correlating
the Middle Floridan confining unit. These are
only two of many examples of fractured
intervals encountered during data collection that
warrant further structural study.

Small irregular surfaces in Miocene and older
lithostratigraphic units in the southern part of the
study area raise many questions regarding the
prevalence of structural deformation within
Florida's relatively young carbonate platform.
Missimer and Maliva (2004) suggest that
observed disturbances in lithostratigraphic
surfaces throughout Florida are due to
"differential subsidence by tensional basement
displacement." Their conclusions are based on
seismic surveys and borehole data attained from
areas of variable formation depths. Charlotte
and Lee Counties are among the most widely






BULLETIN NO. 68


studied of these areas. Seismic surveys reveal
variations in depth to formations (i.e., relief of
unit surface) between -130 to -230 ft (39.6 m to
70.1 m) (Missimer and Gardner, 1976). Other
seismic profiles in the region also suggest
deformation (Evans and Hine, 1991; Lewelling
et al., 1998). Missimer and Maliva (2004)
propose that these deformed surfaces, some of
which extend more than a mile across, are
tectonically induced folds. On the other hand,
Wolansky et al. (1983), Evans and Hine (1991),
Lewelling et al. (1998) and Cunningham et al.
(2001) prefer the hypothesis that observed
perturbations in seismic reflectors are the result
of karstic processes rather than structurally or
tectonically related deformation.

Geomorphology

The topography (Figure 5) and
geomorphology (Figure 6) of Florida have been
influenced by interactions of sea-level changes,
karst processes and subtle tectonic forces
(Rupert and Arthur, 1990; Schmidt, 1997). The
rate of Florida's carbonate platform deposition
was controlled by sea-level cycles and stand
durations, which produced different
physiographic features (e.g., Healy, 1975;
Randazzo, 1997).

Prominent ridges formed in shallow-water
marine environments during sea-level high
stands. Paleo- water bodies, embayments,
swales, relict coastal features and streams
control where many present-day streams and
lakes are located (White, 1970, Randazzo.,
1997). Orthogonal patterns in modem drainage
systems within the southern part of the study
area may have been influenced by fractures
(Lewelling et al., 1998) formed in response to
peripheral Miocene-Pliocene stress fields
associated with Caribbean tectonics (Missimer
and Maliva, 2004).

Physiographic Provinces and Features

Aerially extensive and distinctive
physiographic provinces in the study area are
summarized in this section, starting with the
coastal zone and working inland (Figure 6). The


coastline along the SWFWMD has been
classified into two zones (Tanner, 1960a,
1960b): 1) north of Pasco County the coastal
zone is dominated by swamps, salt marshes,
oyster reefs and drowned karst topography and
2) south of Pasco County, depositional marine
environments contributed to the formation of
barrier beaches, barrier islands, barrier spits and
over-wash fans.

The Gulf Coastal Lowlands (White, 1970)
include the western extent of the SWFWMD,
ranging in width from less than 2 mi to
approximately 45 mi (3.2 km to -72 km).
Elevations range from sea-level to
approximately 100 ft (30.5 m) above mean sea
level (MSL). Diverse ecosystems are present
within the Gulf Coastal Lowlands including pine
flatwoods, dry prairies and to a lesser extent,
swamps, scrub and high pine and salt marshes
(Crumpacker, 1992). The Gulf Coastal
Lowlands do not coincide with any mappable
marine terrace and are generally characterized
by wide, flat marine karstic plains, including
paleo-dunes (White, 1970). Significant updates
and revisions to Florida's geomorphic
nomenclature are ongoing, with an emphasis on
geologic processes and framework geology
(Scott, 2004). Re-classification of the Gulf
Coastal Lowlands into the Chiefland Karst Plain,
Crystal River Karst Plain, and the Land O'
Lakes Karst Plain is proposed (Scott, 2004).

The Brooksville Ridge is a prominent upland
east of the Gulf Coastal Lowlands, striking
north-northwest discontinuously from Pasco to
Levy Counties. The total length is
approximately 110 mi (177 km) including the
inter-ridge Dunellon Gap (Figure 6). The Ridge
varies in width from approximately 4 to 10 mi
(6.4 to 16.1 km) (White, 1970). Elevations
along this upland range from approximately 70
to -300 ft (21.3 to 91.4 m) above MSL. Fine-
grained, low-permeability sediments within the
Brooksville Ridge, particularly Hawthorn Group
clays, reduce relative infiltration rates and
provide a chemical buffer that inhibits carbonate
dissolution. Areas without thick clay-rich
siliciclastic deposits, through geologic time, are
more vulnerable to a reduction in land surface
elevation. This process, known as topographic







FLORIDA GEOLOGICAL SURVEY


Topography

0 -, III 0 I, 4ii


c al i 7 *. 1 1:11:11:1
Pro:cliio: n CuLIoni F)DEP -I.. rE
"-


Gulf
of
Mexico


Explanation

| 1 | ,S uI, -re,3
- VV.?Itr rM.an.a.gement Distri:ts

Elevation
310 ft

S155 t

Oft


Figure 5. Shaded relief topography of the study area based on 15 m (49 ft) resolution digital
elevation model DEM (digital elevation model) (Arthur et al., in review).







BULLETIN NO. 68


Geomorphology
0 5 10 20 30 40
31 I Miles
0 5 10 20 30 40
Kilometers
Scale 1 1,750,000
Projection: Custom FDEP Albers


Silver Glen

0
g Alexander


Y A
^ .


0


r
oS
S0
0.


- C-


Zep C
Zephyrhill3 Gap


0
'8


0Polk Upland



Polk Upland 1|.


S Volusia Blue








SM i

Mount Dora Ridge


*1
I
I

I

II


IJ

I


0


0



Explanation

I I Study Area \
- Water Management Districts

Springs (1st Magnitude)

o Springs

W Geomorphology


Desoto Plain




d

Caloosahatchee Inch


C -aIooslatchee V
- Caoosa~atchee Valle


: '.


Figure 6. Geomorphology of the study area (from White, 1970 and Puri and Vernon 1964). Spring
locations from Scott et al. (2004).


O O0
~' O


Gulf
of
Mexico






FLORIDA GEOLOGICAL SURVEY


inversion, is thought to have been an important
factor in the origin of the Brooksville Ridge
(White, 1970; Knapp, 1977). Karst features are
abundant along the axis of the Brooksville
Ridge. These features are generally internally
drained and locally breach the low-permeability
sediments in the subsurface and serve as focal
points of aquifer recharge. Ecosystems present
within the Brooksville Ridge area include scrub
and high pine, temperate hardwood forests (with
less extensive swamps), pine flatwoods, and dry
prairies (Crumpacker, 1992).

The Western Valley is located east of the
Brooksville Ridge and Tsala Apopka Plain and
west of the Sumter and Lake Uplands (Figure 6).
It is also bound to the north by the Northern
Highlands and the Polk Upland to the south. The
Western Valley is approximately 140 mi (225
km) long and between 5 and 15 mi (8.0 to 24.1
km) wide; elevations average approximately 40
ft (12.2 m) MSL and range up to 100 ft (30.5 m)
MSL. Ecosystems present in the Western
Valley include temperate hardwood forest (to
the north), scrub and high pine, minor swamps,
pine flatwoods and dry prairies (Crumpacker,
1992). The Western Valley is characterized by
its gently rolling limestone karst plains
containing a veneer of Pleistocene sediments
overlying Eocene carbonates (Rupert and
Arthur, 1990). The Tsala Apopka Plain is
believed to be a relict feature of a larger paleo-
lake (White, 1970). Scott (2004) proposes
reclassification of the Western Valley into the
Williston Karst Plain and Green Swamp Karst
Plain.

The Polk and Lake Uplands, located between
the Gulf Coastal Lowlands and the Lake Wales
Ridge are approximately 100 mi (161 km) in
length and range in elevation from 80 ft (24.4 m)
MSL to 130 ft (39.6 m) MSL. Pine flatwoods
and dry prairies with lesser amounts of
temperate hardwood forest, scrub and high pine
comprise the ecosystems in these uplands
(Crumpacker, 1992). A scarp with relief of
approximately 25 ft (7.6 m) separates the Polk
and Lake Uplands from the Gulf Coastal
Lowlands and Western Valley (Arthur and
Rupert, 1989). These two uplands contain three
minor ridges: the Winter Haven Ridge, the Lake
Henry Ridge and the Lakeland Ridge (White,


1970). The land surface is comprised mostly of
mild to gently rolling hills gradually increasing
in elevation eastward. Miocene-Pliocene clays in
this region overlying older carbonates create a
hydrogeologic environment conducive to the
rapid formation of large cover-collapse
sinkholes. Scott (2004) proposes to rename the
Polk Uplands in combination with the DeSoto
Plain: the Polk-DeSoto Plain. The part of the
Lake Upland in the present study area is
proposed to be renamed the Green Swamp Karst
Plain (Scott, 2004).

The DeSoto Plain is a broad, gently sloping
area south of the Polk Upland, east of the Gulf
Coastal Lowlands and west of the Lake Wales
Ridge. Elevations vary between 30 and 100 ft
(9.1 to 30.5 m) MSL (Wilson, 1977). The
DeSoto Plain varies from 10 to 40 mi (16.1 to
64.4 km) in length from north to south and 10 to
50 mi (16.1 to 80.5 km) in width from west to
east. Ecosystems present within the area include
pine flatwoods and dry prairie with minor
swamp, scrub and high pine (Crumpacker,
1992). The lithology consists of thick sandy
clays over Pliocene and Miocene limestones of
poor induration.

The most prominent geomorphic feature in
the study area is the Lake Wales Ridge. This
large elongate upland extends from Lake County
south to Highlands County, where it is flanked
by paleodune fields on the eastern margin (Scott
et al., 2001). Ecosystems on the Ridge include
freshwater marsh, pine flatwoods and dry
prairies (Crumpacker, 1992). A belt of lakes
dominate the Intraridge Valley in the southern
part of the Lake Wales Ridge. Geophysical
investigations of lakes within the Intraridge
Valley confirm a karst-related origin: irregular,
discontinuous seismic reflectors underneath
some lakes reveal breaches through confining
beds overlying the FAS (Evans et al., 1994;
Tihansky et al., 1996), thus indicating that the
large collapse features occurred prior to or
during Pliocene siliciclastic deposition (Arthur
et al., 1995).

Elevations on the Lake Wales Ridge range
from approximately 70 to 312 ft (21 to 95.1 m)
MSL, the latter forming a hilltop feature known
as Sugarloaf Mountain in Lake County. Unlike
the geology of the Brooksville Ridge, the Lake






BULLETIN NO. 68


Wales Ridge contains a very thick sequence of
permeable Pliocene-Pleistocene sediments (as
much as 350 ft [107 m]; see also Surficial
aquifer system, p. 53) overlying variably thick
clays of the Peace River Formation. In the
southern part of the Ridge, depth to carbonate
rocks exceeds 325 ft (99.1 m) BLS.

Morphology of the eastern flank of the Lake
Wales Ridge was likely controlled by high-
energy shoreline currents throughout the
Pleistocene (and perhaps the late Pliocene) as
indicated by the sharp topographic relief on the
eastern side of the Ridge. The presence of
discoid quartz pebbles in these sediments
(Cypresshead Formation) also indicates a high
energy depositional environment (Tom Scott,
personal communication, 2004). In contrast, the
western side of the southern part of the Ridge is
flanked by less pronounced topographic relief on
the Polk Upland and DeSoto Plain.

The general topographic relief of the
southern part of the Lake Wales Ridge mimics
that of the emergent part of the Florida Platform
with a steep shelf slope along the east and a
broad gentle slope to the west. Along the
southern margin of the Ridge (Figure 7), subtle
topographic ridges that trend toward the west
bear remarkable resemblance to the southern
Florida peninsula and the Florida Keys
suggesting that paleo-longshore and ocean
currents (e.g., loop current) that existed during
the Plio-Pleistocene are similar to those of
present day. Petuch (1994) referred to this area
as the Caloosahatchee Strait.

Sinkholes

In addition to paleo-sea levels and ocean
currents, karst processes have sculpted the
landscape of southwest Florida. Sinclair et al.
(1985) mapped four types of sinkholes in the
SWFWMD: 1) limestone dissolution: slow-
developing, funnel-shaped with a growth rate
similar to the rate at which the carbonate rocks
dissolve, overburden is thin; 2) limestone
collapse: forms abruptly and overburden is thin
3) cover- subsidence sinkholes: gradual
formation and generally small diameter, where
overlying sands infill limestone dissolution
cavities, overburden is greater than 30 ft (9.1 m)
thick; and 4) cover-collapse sinkholes: sudden
formation and relatively large in diameter,


forming upon a breach of clayey material
overlying a cavity, overburden is greater than 30
ft (9.1 m) thick. These sinkholes significantly
contribute to interaction between surface and
groundwater, intra-aquifer and inter-aquifer
communication (e.g., Tihansky, 1999) and the
vulnerability of aquifers to surface sources of
contamination (Arthur et al., 2007).

Plate 3 reflects the distribution of closed
topographic depressions (CTD) throughout the
SWFWMD region. This map is based on a 15 m
(49.2 ft) resolution digital elevation model
(DEM) produced by the FDEP-FGS in
cooperation with other FDEP programs and
Florida's water management districts. While not
all CTDs reflect karst features (i.e., paleodunes,
etc. may also be included), this depression
coverage provides a good approximation of
sinkhole distribution patterns within the study
area. The coverage, however, does not reflect
the tens of thousands (if not more) of buried
sinkholes detectable by means of surface
geophysical surveys (e.g., Wilson and Beck,
1988; Moore and Stewart, 1983), nor does it
include small karst features detectable by
LIDAR or sinkholes that formed since the USGS
topographic maps were last updated.

Springs

Springs predominantly occur in the northern
two-thirds of the study area (Figure 6).
Submarine springs occur offshore of Lee County
and between Pinellas County and Citrus County
(Ryder, 1985; DeWitt, 2003). Five of Florida's
thirty-three first magnitude springs (>100 ft3/sec;
>2.83 m3/sec) occur within the study area: Kings
Bay Springs Group, Homosassa Springs Group,
Chassahowitzka Springs Group (all in Citrus
County), Weeki Wachee Springs Group
(Hernando County) and the Rainbow Springs
Group (Marion County) (Champion and Starks,
2001). The Coastal Springs Groundwater Basin
(Knochenmus and Yobbi, 2001) encompasses
parts of Citrus, Hernando and Pasco Counties
and includes three of the five first magnitude
springs. The Coastal Springs Groundwater
Basin is made up of four sub-basins: Aripeka,
Weeki Wachee, Chassahowitzka and Homosassa
Springs. These groundwater sub-basins
comprise part of the total recharge area for these
springs. Surface water basins comprise the other
component. As defined and described in DeHan







FLORIDA GEOLOGICAL SURVEY


Topography
of South-Central
Florida
0 o10 M lOI-

o0 10 K .-:.-eer,

Prleir: t:bn Cu i ;:n-, FDE P -lbjer


Explanation

I Counties
Lake Wales Ridge
310ft
155 ft
Oft


Area
of -
Interest


Figure 7. Shaded topographic relief of the southern extent of the Lake Wales Ridge.


T.L i






BULLETIN NO. 68


(2004), "those parts of surface-water and
groundwater basins that contribute to the flow of
a spring" are called springsheds. Given the
proximity and hydraulic interrelationships
among the springsheds of the Coastal Springs
Groundwater Basin, the term "Springshed
Group," (analogous to a "Group" in
lithostratigraphic nomenclature) is herein
introduced to characterize this and similar
regions of coalescing springsheds (e.g., Coastal
Springs Springshed Group). Copeland (2003a)
compiled a Florida springs classification system
and glossary to facilitate standardized use of
springs-related nomenclature among Florida's
various technical (i.e. cave divers), scientific and
regulatory/planning communities.

The Coastal Springs Springshed Group and
the many other springs and springsheds in the
study area support unique ecosystems that
harbor diverse flora and fauna (Scott et al.,
2004; Champion and Starks, 2001). When water
quality and quantity decline, these ecosystems
are adversely affected. The magnitude and
nature of the threats varies within each
springshed based on land use and geology
(Hartnett, 2000; Florida Department of
Community Affairs and Florida Department of
Environmental Protection, 2002). It is
noteworthy that springshed boundaries are time-
dependent; they migrate in response to
anthropogenic activity (e.g.,
pumping/withdrawal) and seasonal/climatic
effects on the potentiometric surface (DeHan,
2004; Greenhalgh, 2004; Scott et al., 2004).

Since the 1970's scientists have documented
a decline in water quality in most of Florida's
springs especially with regard to nutrients (Jones
et al., 1998; Hartnett, 2000; Copeland, 2003b).
Nitrate is of particular concern as high amounts
may lead to excessive growth and eventual
eutrophication of surface water bodies. Nuisance
and exotic plants can cause reduction of water
flow, reduction of dissolved oxygen and habitat
changes (Hartnett, 2000). Nitrate has been a
concern in SWFWMD for many years as
increased levels of nitrates are being detected at
many springs (Jones et al., 1997). Natural
background concentration of nitrates in the FAS
is less than 0.01 mg/L (Champion and Starks,


2001). Florida government agencies have
recently proposed best management practices
(BMPs) to protect and conserve Florida's
springs (Florida Department of Community
Affairs and Florida Department of
Environmental Protection, 2002).

Spring-water quantity is another issue
associated with development and population
growth. Under redevelopment conditions
springs accounted for about 84 percent of water
discharged from the FAS (Ryder, 1985). As
development increases and more well fields are
used, the potentiometric surface of the FAS is
lowered. This results in lower spring discharge,
which can then result in changes in water quality
(Lee, 1998). Spring flows become dramatically
reduced or eliminated by over-pumping water
from the aquifer. Near coastal zones, changes in
aquifer conditions can also affect the location of
the transition zone between fresh and salt water
(Scott et al., 2004). As spring discharge rates
decrease, calcium and magnesium have been
observed to increase possibly owing to upcoming
or the removal of water from intergranular
storage (Rick Copeland, personal
communication, 2006). Although not fully
established at the current time, preliminary
evidence suggests that the upcoming of sulfates
and other constituents (i.e., micronutrients) may
be contributing to algal development in springs
(Sam Upchurch, personal communication,
2006). Corresponding increases in chlorides
may also be observed in the spring water as
discharge rates decrease. These conditions also
allow migration of saltwater further inland (Lee,
1998).

Hydrogeology

Three major hydrostratigraphic units occur in
west-central Florida: the surficial aquifer system
(SAS), the intermediate aquifer
system/intermediate confining unit (IAS/ICU)
and the Floridan aquifer system (FAS). Miller
(1986) divides the FAS into two zones of higher
permeability: the Upper Floridan aquifer (UFA)
and the Lower Floridan aquifer (LFA), which
are separated by one or more regional confining
units (Middle Floridan confining unit; MFCU).






FLORIDA GEOLOGICAL SURVEY


In this report, nomenclature and definitions
of units are primarily based on that proposed by
the "Ad Hoc Committee on Florida
Hydrostratigraphic Unit Definitions"
Southeastern Geological Society, 1986). A 2nd
Ad Hoc Committee on Florida
Hydrostratigraphic Unit Definitions (CFHUD II)
is presently convened to address identified
concerns regarding existing nomenclature and
definitions (Copeland et al., in review). The
CFHUD II is comprised of representatives from
the FDEP-FGS, USGS, water management
districts and consulting firms. Appendix 1
includes a commentary on nomenclatural issues
with regard to Florida's hydrostratigraphy.

The present study adopts the following
aquifer-system names and definitions, which are
minor revisions of the widely accepted, yet
dated Southeastern Geological Society (1986)
proposal. These definitions are revised in the
context of statewide application, and not limited
to the study area. Appendix 2 provides
explanation of changes from original
Southeastern Geological Society (1986)
definitions.

surficial aquifer system the permeable
hydrogeologic unit contiguous with land
surface that is comprised principally of
unconsolidated to poorly indurated
siliciclastic deposits. It also includes
carbonate rocks and sediments, other than
those of the FAS where the Floridan is at
or near land surface. Rocks and sediments
making up the SAS belong to all or part of
the Miocene to Holocene Series. The SAS
contains the water table and water within it
is under mainly unconfined conditions;
however, beds of low permeability may
cause semi-confined or locally confined
conditions to prevail in its deeper parts.
Locally perched water-table conditions
occur as well. The lower limit of the SAS
coincides with the top of laterally
extensive and vertically persistent beds of
much lower permeability.

intermediate aquifer system/
intermediate confining unit includes all
rocks that lie between and collectively
retard the exchange of water between the


overlying SAS (or land surface) and the
underlying FAS. These rocks in general
consist of coarse-to-fine-grained
siliciclastic deposits interlayered with
carbonate strata belonging to parts of the
Oligocene and younger series. The
aquifers within this system contain water
under semi-confined to confined
conditions. The top of the IAS/ICU
coincides with the base of the SAS and on
a local scale with land surface. The base
of the IAS/ICU is hydraulically separated
to a significant degree from the top of the
FAS.

Floridan aquifer system a thick,
predominantly carbonate sequence that
includes all or part of the Paleocene to
Lower Miocene Series and functions
regionally as a water-yielding hydraulic
unit. Where overlain by the IAS/ICU, the
FAS contains water under confined
conditions. When overlain directly by the
SAS, the FAS may or may not contain
water under confined conditions
depending on the extent of low
permeability material within the base of
the SAS. Where the carbonate rocks crop
out or are covered by a veneer of
permeable siliciclastics, the FAS generally
contains water under unconfined
conditions near the top of the aquifer
system, but because of vertical variations
in permeability, deeper zones may contain
water under confined conditions. The
FAS is present throughout the State and is
the deepest part of the active groundwater
flow system on mainland Florida. The top
of the FAS generally coincides with the
absence of significant thicknesses of
siliciclastics from the section and with the
top of the vertically persistent permeable
carbonate section.

Generalized correlations between
hydrostratigraphic units and lithostratigraphic
units mapped in this study are presented in Table
2. The HilJiiu,,, ,,g,,' section, p. 52, of this
report provides a more detailed discussion of
these aquifer systems. Delineation of aquifer-
system boundaries is described in Methods, p.
20.











Table 2. Generalized correlation chart for units mapped within study area (ages compiled from Covington, 1993, Missimer et al., 1994,
Scott et al., 1994, and Wingard et al., 1994). Numbers are million years before present. Ages are included for reference only and are not


scaled to correlate with all columns in the table. MFCU is Middle Floridan confining unit;
and Caloosahatchee Formations.


- ~ S II


Holocene
P- .01 -
Pleistocene
1.8

Pliocene

- 5.3



Miocene


--- 23.03-


Oligocene

-- 33.9 -




Eocene


Undifferentiated
sand, shell, and clay
(UDSC)


Bone
Valley Mbr.
3 Peace River Fm.
0
S Arcadia
Formation

r Tampa
c Member
Nocatee
Member


ISuwannee Limestone


Ocala Limestone


Avon Park
Formation


Hydrostratigraphic
unit


Quat-
ernary






0J

z
Zr


UDSC includes the Tamiami, Ft. Thompson


Erathem ISystem


Series


Lithostratigraphic
unit


Generalized lithology

Highly variable lithology ranging from
unconsolidated sands to clay beds with trace
amounts of shell fragments
Peace River Formation contains interbedded
sands, clays and carbonates with siliciclastic
component being dominant;variable
phosphate sand content

Arcadia Formation is a fine-grained carbonate
with low to moderate phosphate and quartz
sand, variably dolomitic

Suwannee Limestone is a fine-to medium-
grained packstone to grainstone with trace
organic and variable dolomite and clay
content
Ocala Limestone is a chalky, very fine-to
fine-grained wackestone/packstone varying
with depth to a biogenic medium- to
coarse-grained packstone grainstone; trace
amounts of organic material, clay and
variable amounts of dolomite

Avon Park is a fine-grained packstone with
variable amounts of organic-rich laminations
near top; limestone with dolostone interbeds
typical in upper part, deeper beds are
continuous dolostone with gypsum near base


surficial aquifer
system (SAS)




intermediate
aquifer
system or
intermediate
confining unit
(IAS/ICU)





71

E Upper
Floridan
S aquifer
S(UFA)

Cr
0I

M UMFCU


_ __


--






FLORIDA GEOLOGICAL SURVEY


Sediments comprising the SAS are
predominately post-Hawthorn in age and
generally consist of some combination of sands
shells and clays. In parts of the northern District
where the IAS/ICU is not laterally extensive,
discontinuous clay lenses serve as basal SAS
confinement, locally separating the SAS from
the FAS. Some of these basal clays may be
erosional remnants of (and correlative with)
lithostratigraphic units comprising the IAS/ICU.
In areas where Pliocene clayey sediments (see
clayeyy sand," Figure 4) are exposed at or near
land surface, such as west-central Polk County,
the SAS or water-table aquifer may not be
present; instead, the setting reflects IAS/ICU
overlying the FAS. Where hydraulic continuity
exists between uppermost Hawthorn Group
sands and younger sediments, the SAS includes
those sands, which are generally less than 20 ft
(6.1 meters) thick. In the southernmost part of
the study area, the Ft. Thompson and
Caloosahatchee Formations and upper
permeable sediments of the Tamiami Formation
comprise the SAS. Although mapping of these
complex "post-Hawthorn" units is beyond the
scope of this study, research did focus on the
depth and extent of clays within the Pliocene
Tamiami Formation, which are significant as
they comprise the base of the SAS in the region
(e.g., Reese, 2000; Weinberg and Cowart, 2001).

The IAS/ICU occurs throughout most of
Florida (Scott, 1992a) and correlates with
aquifer systems in parts of Georgia and
Alabama. In the study area, it is comprised of
mid- to upper Oligocene Pliocene sediments
and is generally continuous south of Pasco
County. As this hydrostratigraphic unit thickens
southward, interlayered permeable carbonates
become important water-producing zones,
especially south of Manatee County where the
FAS water becomes less potable. In this area,
three permeable zones are present; however,
correlation and mapping of these zones is
difficult, even with the use of hydrochemical
parameters (Knochenmus and Bowman, 1998;
Torres et al., 2001; Knochenmus, 2006). North
of Hillsborough County, the IAS/ICU
predominantly occurs within the uplands and
ridges, where it functions hydrologically as a
semi-confining to confining unit.


The FAS is one of the most productive
aquifers in the world. It underlies all of Florida,
southern Georgia and small parts of Alabama
and South Carolina for a total area of about
100,000 mi2 (-259,000 km2) (Johnston and
Bush, 1988). In parts of southwest Florida,
south from Sarasota, Charlotte, Glades and Lee
Counties, the FAS contains mineralized, non-
potable water. As a result, relatively permeable
zones within the IAS/ICU comprise the main
source of water supply (Miller, 1986; Torres et
al., 2001) in this region. The FAS is confined
except in parts of the northern third of the study
area where it occurs at or just below land surface
(Ryder, 1985). Throughout the study area, the
FAS predominately consists of carbonate rocks
(Southeastern Geological Society, 1986) ranging
in age from Paleocene to Miocene.

METHODS

Sample Description

More than 250 detailed lithologic de-
scriptions of borehole cores and cuttings were
completed for this study. These descriptions
record standard rock, mineral, fossil and textural
features. Selected parameters include color,
induration, grain size and range, sorting,
roundness, mineral percentages and special
descriptive, depositional or sedimentary
features. Descriptions of carbonate material
were based on the Dunham (1962) classification
system, which focuses on depositional texture
and whether the rock is mud-supported or grain-
supported: 1) mudstone muddy carbonate rock
containing less than 10 percent grains, 2)
wackestone mud supported rock containing
more than 10 percent grains, 3) packstone grain
supported muddy carbonate, 4) grainstone -
mud-free carbonate rock which is grain
supported and 5) boundstone carbonate rock
showing signs of being bound (e.g. cementation)
during deposition and reflecting original position
of growth. It should be noted that the Dunham
(1962) classification considers a "grain" as
having a diameter greater than 20 microns, while
"mud" is less than 20 microns. As a result, a
very fine grained grainstone may appear as a
mudstone even under a low-power binocular
microscope (David Budd, 2004, personal






BULLETIN NO. 68


communication). It is likely that this factor has
biased identification of mudstones in lithologic
descriptions that may technically be fine-grained
grainstones.

During archiving of borehole cuttings,
samples are gently washed in a 63 micron sieve
to remove any drilling mud (e.g., silt and clay-
sized material). When describing lithologic
characteristics of borehole cuttings, care was
taken to inspect the washed and unwashed
archival fractions of the samples. In many
cases, especially for older wells, the washed
sample fraction may under-represent the clay
fraction of the sample. For example, cuttings
representing the sandy clayey Nocatee Member
(Arcadia Formation) may have been washed to
the degree that only sand remains in the archived
sample. In such cases, the unwashed sets of
samples provide a better representation of the
original clay-rich lithology.

The descriptions are coded within the
aforementioned Microsoft AccessT" database -
FGS Wells. This database is undergoing
continued enhancements including migration to
a more robust enterprise-level platform. These
and other lithologic descriptions are available
from the Florida Geological Survey web site:
http://www.dep.statefl.us/geology/.


Delineation of Boundaries


Formations/Members

Formation and member boundaries were
determined for all described samples and for
cores, cuttings and geophysical logs from an
additional -600 wells. Florida Geological
Survey published and unpublished data (e.g.,
Stewart, 1966; Hickey, 1982, 1990; Johnson,
1986; Miller, 1988; Scott, 1988; Campbell,
1989; DeWitt, 1990; Campbell et al., 1993,
1995; Clayton, 1994, 1999; Green et al., 1995,
1999; Sacks, 1996; Arthur et al., 2001a; Gates,
2001; Missimer, 2002; and O'Reilly et al., 2002)
provided lithostratigraphic and hydrostratigraphic
boundary information on an additional -200
wells. Gamma-ray logs and fossil assemblages
are used only to supplement the lithologic data


in the determination of the boundaries. Where
uncertainty exists regarding the exact position of
the formation boundary, or where the boundary
is inferred within an interval of poor or no
sample recovery, a dashed rather than solid line
is shown on the cross sections. Dashed contacts
are also drawn where only a gamma-ray log was
used and no samples were available for
inspection. In cases where sample quality is
poor, as is often true with cuttings, the gamma-
ray logs become more important in the
determination of formation boundaries.

Uncertainties in lithostratigraphic unit
boundaries were recorded in a database of
elevations and thicknesses. These uncertainties
exist for several reasons. In the case of
inspecting cores, it is not uncommon for two
experienced geologists to disagree on a
formation boundary, especially when it is subtle
or gradational. Moreover, the core may have
poor recovery, resulting in missing intervals.
Regarding cuttings, samples often contain
borehole cavings, whereby the sampled interval
contains sediment or rock fragments from
overlying units. For example, in an extreme
case, dolostone cuttings from the Avon Park
Formation may contain phosphatic sands from
the upper Hawthorn Group. As a result, it is not
uncommon for a formation boundary estimation
based on cuttings to include an uncertainty range
on the order of 20 ft (6.1 m) based solely on
sample quality. Other uncertainties with respect
to mapped unit elevations also exist (see Map
Development and Data Management, p. 24).

Table 2 summarizes the lithostratigraphic
units shown on the maps. The same units are
also shown on the cross sections. For the
purposes of this study, post-Hawthorn units are
depicted as Pliocene-Pleistocene sediments
(undifferentiated) and Pleistocene Holocene
undifferentiated sand and shell or sand and clay
(UDSS or UDSC, respectively).

Aquifer Systems

Delineations of hydrostratigraphic units in
this report are based on the following: 1)
available hydrogeologic data collected during
drilling, 2) borehole geophysical logs,






FLORIDA GEOLOGICAL SURVEY


3) hydrogeologic characteristics of the samples
(e.g., estimated porosity and permeability,
hydraulic continuity between lithostratigraphic
units), 4) potentiometric data from nested
monitor wells, and 5) in the absence of other
data, correlation to lithostratigraphic units.
Application of the first four methods is highly
preferred; the majority of this data originates
from ROMP wells.

Contacts between aquifer systems can be
very subtle or abrupt depending on the
hydrogeologic properties of the rocks and
sediments. When only lithologic material from
a borehole is available on which to base an
aquifer-system boundary, further complications
arise. Preferential removal of clay-sized
particles, either during drilling or sample
archiving (e.g., sorting during material transfer
or washing of cuttings), tend to bias toward
interpretations of higher sample permeability.

Delineation of the basal contact of the SAS is
perhaps the most susceptible to the
aforementioned bias. If the contact is based
solely on estimates of hydrogeologic properties
of lithologic data, misrepresentation of clay
content, especially in borehole cuttings may
result in the interpretation of a preferentially
deep base of the SAS. This issue may become a
factor where the SAS may include sediments as
old as the upper Hawthorn Group. On the other
hand, permeable sands along the top of the upper
Peace River Formation in Manatee County (Tom
Scott, personal communication, 2006) comprise
the lower part of the SAS. If there is reason to
believe that the two units (Hawthorn and post-
Hawthorn Group sediments) are hydraulically
connected, both would be considered part of the
SAS. Alternatively, sandy clays overlying clay-
rich Hawthorn Group sediments would be
considered part of the IAS/ICU (assuming
sufficient lateral extent). Further south, the
Tamiami Formation is included within both the
SAS and IAS/ICU.

Noting the above exceptions, the lateral
extent of the IAS/ICU broadly corresponds to
the extent of Hawthorn Group sediments, except
where those sediments are part of the FAS (e.g.,
the Tampa Member [Arcadia Formation] along
the upper reaches of the Hillsborough River).
For consistency, in areas where the IAS/ICU is


mapped owing to sufficient lateral continuity,
the SAS is mapped over the same extent. In
areas where the SAS and IAS/ICU are
discontinuous, the FAS is generally
characterized as unconfined to semi-confined
(see Hy ,,,I,,i g ph y', p. 52, for more detail).

Figure 8 represents a compilation of
hydrogeological data to provide correlation
between hydrostratigraphic units and
lithostratigraphic units. In most areas, the
correlation is readily apparent, such as the
relation between the top of the Suwannee
Limestone in Sarasota County with the top of the
FAS. In another example, the Tampa Member
(Arcadia Formation) is hydraulically connected to
the FAS in Pinellas County and therefore
comprises the uppermost part of the FAS. The
correlations, however, are not always
straightforward, such as the area denoted as
"variable" (Suwannee Limestone and Nocatee
Member, Arcadia Formation) in DeSoto County
(Figure 8).
Cross-Section Construction

Detailed lithologic descriptions, gamma-ray
logs and hydrologic data comprise the bulk of the
information used to develop the cross sections.
The dominant sources of information for cross-
section control are SWFWMD ROMP wells;
FDEP-FGS wells were included to fill out
appropriate data-point coverage for the cross
sections. Where no lithologic data was available,
borehole geophysical logs were used. Of these
geophysical logs, gamma-ray logs were the most
readily available and generally useful for
correlative purposes within the study area.
Gamma-ray logs were included in the cross
sections to allow comparison of the gamma-ray
signatures relative to each stratigraphic unit. The
following discussion outlines the methods used
for construction of the cross sections for this
study.

Topography

Topographic profiles were included on each
cross section to facilitate comparison of surface
morphologies with subsurface stratigraphy. Data
used to construct these profiles was taken from U.S.
Geological Survey 1:24,000 (7.5 minute) quadrangle
maps. The profiles include selected anthropogenic
features, cultural boundaries and landforms.







BULLETIN NO. 68


Generalized Correlation
Between Lithostratigraphy and
Top of Ihe Floridan aquifer system
.. :. ,.. ,.1 40
SMiles
I ,. ,..ters
S.Pr:o 1 1 l.i: m FC11 1' EAl
Pr,:lec:i:,n Cusl.,m FDEP Albers


Gulf
of
Mexico





















Explanation
I Study Area
Contours (75N inler all
Correlated FAS Units
Avon Park Formall:on
Ocala Limestone
Ocala Ls. & Avon Park Fm.
Suwannee Limestone
Suwannee Ls. & Tampa Mbr.
Tampa Member
~ Variable


Figure 8. Generalized correlation between lithostratigraphic units and the surface of the FAS. The
area labeled "Variable" includes parts of the Nocatee Member (Arcadia Formation, Hawthorn
Group) and the Suwannee Limestone.






FLORIDA GEOLOGICAL SURVEY


Lithology

For each well in a cross section, a
stratigraphic column was developed to represent
borehole lithology. The columns were based on
either existing descriptions or new descriptions
generated for this report. Hatch patterns depict
primary lithologies in the columns, with
accessory minerals shown on the right of the
columns as text codes. Where space is
available, the cross sections contain an
explanatory legend that defines mineralogic and
lithologic codes and patterns. For those cross-
sections without sufficient space to include the
"Explanation," it is also provided for reference
in Figure 9. Accessory-mineral codes are
generally the same as those used in the FDEP-
FGS lithologic database (FGS Wells). If the
volume of reported accessory sand-sized
minerals exceeds 5 percent, the content is
represented by a stippled sand pattern. If the
amount of accessory sand-sized minerals is less
than 5 percent, or if the amount is not known
based on existing descriptions, the accessories
are listed in the text codes. The mineral text
codes are listed in decreasing order of
abundance if the relative mineral abundance has
been reported.

The degree of detail within each lithologic
column generally reflects the type of material
available for description as well as the degree of
detail in the description. In most cases, more
detailed lithology exists for the cores. The
minimum bed thickness represented on the
stratigraphic columns is 5 ft (1.5 m) due to
graphical constraints. There are several
examples where lithologies and accessory
minerals have been averaged over a 5 to 10 foot
(1.5 to 3.0 m) interval to accommodate this
graphical limitation.

Gamma-ray Logs

Selected gamma-ray logs are plotted to the
right of stratigraphic columns on the cross
sections. These logs are used as a supplement to
delineate formation boundaries and allow
comparison of gamma-ray activity between the
various lithostratigraphic and hydrostratigraphic
units (e.g. Gilboy, 1983; Green et al., 1995;


Scott, 1988 and Davis et al., 2001). Gamma-ray
intensity units, when known, are shown on the
logs (horizontal axis) in counts per second (CPS)
or in American Petroleum Institute (API) units.
Inconsistencies between logs exist due to
different log settings (e.g., time constant, range)
and borehole characteristics (e.g., depth of
casing and lack of caliper logs to determine
sediment wash-out or cavities), making
quantitative comparison difficult. To allow
assessment of the high degree of variability in
the logs and to represent their natural response,
the intensity scales have not been normalized.
The logs are very useful in the identification of
correlative "packages" of gamma-ray peaks and
for comparison of the overall gamma-ray
signature within formational units. Relatively
high gamma-ray activity is generally correlative
with phosphate, organic materials, heavy
minerals and high-potassium clays. More subtle
changes may reflect dolomite and accessory
mineral content. Figure 10 summarizes general
relationships between gamma-ray activity and
mineralogy, the details of which are included in
the discussion of each lithostratigraphic unit (see
I i,ih, i, ogi,, O h', p. 30).

Aquifer Systems

Aquifer systems on the cross sections appear
as hachured brackets on the left of each
lithologic column. Patterns used in the
hydrostratigraphic columns identify the three
major aquifer systems present in the study area,
as well as the MFCU.


Map Development and Data
Management

For wells used in this study, elevations of
lithostratigraphic and hydrostratigraphic units
were recorded in a database that also included
the corresponding FDEP-FGS well accession
number (W-number), well name, comments
about the well, the geologist(s) who made the
determinations and well location (elevation,
latitude and longitude). The unit elevations on
which the maps are based are recorded in feet
BLS; a separate column calculates the elevation







BULLETIN NO. 68


CROSS SECTIONS EXPLANATION


HATCH PATTERNS
LIMESTONE-



FINE MEDIUM COARSE

t --DOLOSTONE



FINE MEDIUM COARSE

INTERBEDDED
LIMESTONE & DOLOSTONE


FINE MEDIUM COARSE
FINE MEDIUM COARSE


CLAY


SURFICIAL
AQUIFER
SYSTEM


INTERMEDIATE
AQUIFER SYSTEM /
CONFINING UNIT


FLORIDAN
AQUIFER
SYSTEM


MID-FLORIDAN
CONFINING UNIT


AAAAAAAAAAA
hA LA AAA A A
IAA A LAAAA haAl
AAAAAAAAAAI
AAAAAAAAAAA
CHERT


COMMENTS


M MICRITE
S SAND
P PHOSPHATE GRAVEL
D PHOSPHATE SAND


O ORGANIC
R SPAR
I IRON STAIN
Q QUARTZ
A ANHYDRITE
Ch CHERT


T SILT
C CLAY
Sh SHELL
D DOLOSTONE


L HEAVY MINERALS
No Spl NO SAMPLE
G GYPSUM
Py PYRITE


THIN MANTLE OF IAS/ICU SEDIMENTS
' SEMI-CONFINED TO UNCONFINED
FLORIDAN AQUIFER SYSTEM
* CUTTINGS EXAMINED IN THIS INTERVAL
INDICATE FORMATION PICKS SHOWN


Figure 9. Explanation (legend for cross sections).


GRAVEL


SAND


SHELLED GYPSUM


t









FLORIDA GEOLOGICAL SURVEY


u Quanz
A Anhydrite
Ch Chert


IP
Py


Gypsum
Pyrite


ROMP 17
W-15303

S -- IJDSC

i0;T ? .. Pf.ACE I.ER
FORMATION

ARCADIA
55 FORMATION

it -


ROMP 31
W-13514


i L UDSC

PEACE RIVER
.._ ... FORMATION
IO



.. -- R Typical higher count rate
S RCADIA* fortheArcadia Formation
--- FORMATION due tohigherphosphate
: and dolostone content



N!Co .-" TAMPAMEMBERssociated
-iL7 / -raypeaksassociated
i "----- with variable amounts of
S. .-... NOCATEE MEMBER phosphate.


,. /The Tampa and Nocaee
Members have higher
count rates than hat
of the underlying .
S IESUWANNEE (Suwannee Limestone.



- -- - -






l-- OCALA Ocala Limestone response
LIMESTONE with a very low /-ray activity
with few peaks.

r

/-ray peaks due to
-" o-- r ganics commonly found
at or near the top of the r
"- :: \ Avon Park Formation.
i-2'1 \ AVON PARK
,- FORMATION

.I: .0-_- -B"S ,.a..





Comments
Micrite T Silt
Sand C Clay suritcial aquifer system
Phosphate Gravel Sh Shell
Phosphate Sand D Dolostonea a
Organics L Umestone nt meial 'el n o ng uniT"
Spar H Heavy Minerals
Iron Stain NO SPL No Sample


k Flondan aquifer system


Phosphatic lag observed at the
base of the Peace River
Formation with associated 7-ray
peak. The lag may also occur at
the top of the formation.


___ -ray peaks associated
' TAMP.--E--- withe variable amounts
-- TMP, MEMBER of phosphate.

/ The Tampa and Nocatee
SMembers exhibit lower


O CATEE MEMBER \. Arcadia Formation.
S- -__ Peak due to clay beds
.-.. commonly found in the
SNocatee Member.


I.



1.-S



-,


'1,




I.


/-ray response for the
Suwannee Limestone may
exhibit a low count rate for
SLrWANNEE the upper half, and a higher
LIMESTONE for the lower half. The higher
count rate is generally
associated with dolostone
where present (not shown).










OCALA Ocala Limestone response
LIMESTONE with a very low 7-ray activity
with few peaks.










The Avon Park Fm. generally
AVON PARK exhibits a higher background
FORMATION count rate with more
variability than that of the
Ocala Limestone.


Figure 10. Characteristic gamma-ray (y) log responses.


M
S
P
p
0
R
I


F- P














1 -


entateu






BULLETIN NO. 68


relative to MSL. The database also records
uncertainty in the unit elevations. Synthetic
wells were added to the database to serve as
contour control along the margins of the study
area in order to facilitate a more accurate
interpolated surface. Quality assurance of all
well-head elevations was accomplished by
comparing the reported elevation with a 15 m
(49 ft) DEM. The data on which the maps and
cross sections are based is available from
http://ww.uflib.ufl.edu/ufdc/?b UF00087428&
v=00001

Map Interpolation and
Spatial Accuracy

As the GIS database was developed,
preliminary contour maps were generated to
allow identification of anomalous elevations and
data gaps. ArcView with the Spatial Analyst
extension was used to generate the initial
contour maps. For each map, a grid surface
model was calculated using a surface
interpolation method. Contours were then
generated from the surface model. The inverse
distance weighted (IDW) interpolator was found
to provide a very useful surface model for
identifying problem areas and outliers that
required additional research. As these issues
were identified, borehole cuttings were retrieved
from the FDEP-FGS core repository and re-
evaluated in context of: 1) proximal stratigraphy,
2) sample quality, and 3) stratigraphic boundary
uncertainty. This process of generating and
reviewing maps and re-examining samples was
repeated numerous times through the course of
this study. Arthur and Pollock (1998) suggested
that the IDW interpolation method is not suitable
for geologic mapping of stratigraphic data. The
IDW method was used only as an iterative
review tool. Interim maps for the initial phases
of this project were generated using the spline
interpolator. Arthur and Pollock (1998) found
the spline-tension method preferable to IDW
because spline yielded surface models that were
more accurate and geologically characteristic.

Upon review of subsequent interim maps
generated for this project, several shortcomings
in application of the spline interpolator were
recognized. These include false highs and lows


in the model surface that do not reflect any well
control and loss of contour accuracy along the
margins of the maps. Moreover, as the
interpolator was adjusted to yield smoother
contours, the interpolated surface became less
accurate. With the exception of accuracy at a
given well location, it was also difficult to assess
the error associated with the maps in data-poor
areas. Due to the "overshooting contour" effect
(e.g., false topographic highs), shallow map
units may exceed land surface elevations in
certain areas, especially along areas of high
topographic relief.

Prior to generation of the final maps, a re-
assessment of interpolation methods was
completed. Through an iterative process,
kriging was identified as the most robust and
accurate surface interpolator. The GIS project
was then migrated to ESRI ArcMap 8.3. The
map-unit elevation database was imported into
ArcMap and projected in the FDEP standard
projection (custom Albers equal-area conic
projection). Individual surfaces were then
interpolated using the ordinary kriging function
within the ESRI Geostatistical Analyst.
Iterations of krige data models were produced
for each map unit to minimize the map error.
Prediction errors and other descriptive statistics
for each map were recorded and used to identify
appropriate contour intervals (see Contour
interval selection, p. 30). When evaluating krige
statistics, the variability of the prediction (as
standard deviation) is overestimated when the
root mean squared prediction error (RMS) is less
than the average standard error (ASE) of the
prediction error (Table 3; Johnston et al., 2001).

The krige error automatically reported by the
software is based on the error within a
rectangular area defined by the distribution of
the data (i.e., wells). For nearly all of the maps
in this report, these results are misleading
because the datasets have an irregular spatial
distribution. As a result, for each kriged surface,
a prediction standard error map was also created
and masked to the spatial extent of the unit being
mapped. The average standard error of this
prediction standard error map was then
calculated and recorded (Table 3).






FLORIDA GEOLOGICAL SURVEY


As an extra measure to assess map accuracy,
a script was written to allow comparison of the
observed map-unit elevations (i.e., top of the
Suwannee Limestone in a given well) with the
value of the final interpolated grid cell in which
the well is located. On Table 3, this data is
summarized in the "Grid to Point" column,
where the "mean" represents the average of the
difference between grid cells and map unit
elevations for each well located within its
respective grid cell. In every case, the mean
"Grid to Point" value is less than +3 ft, (0.9 m)
for all maps, and the standard deviation (s) is
less than 20 ft (6.1 m) for 18 of the 22 maps and
less than or equal to 30 ft (9.1 m) for the
remaining 4 maps (Table 3). Qualitative
evaluation of these errors suggests they are
normally distributed.

The standard deviations for the "Grid to
Point" calculations (Table 3) are well within
acceptable limits, especially when considering:
1) geologic processes that can create
perturbations in a mapped surface (e.g., faults,
paleo-karst, paleo-environmental features [e.g.,
wave-cut scarps, river valleys]), 2) well location
error or uncertainty, 3) sample quality (e.g.,
cuttings interval and borehole cavings) and 4)
formation pick uncertainty (i.e., gradational
contacts, differences in professional opinion,
etc.).

Once the kriged surfaces were optimized for
each map unit, the shallow surfaces (i.e., top of
the Peace River Formation) were compared to
land surface elevations. To accomplish this, the
kriged surface was converted to a raster file
(grid) using a 400 m2 (4305.6 ft2) cell size,
which was then subtracted from the FDEP-FGS
15 m (49.2 ft.) resolution DEM to remove
interpolated elevations that exceeded land
surface. The grid was clipped (i.e., masked) to
the lateral extent of its respective map unit. For
most of the mapped units, contours generated
from the kriged and the DEM-trimmed surfaces
were generally irregular or jagged. This
characteristic is not only atypical for maps
depicting subsurface elevations and thicknesses,


but it also overemphasizes the level of resolution
represented by the maps. To remove these
localized and misrepresentative contour
anomalies, the grids were smoothed using the
neighborhood statistics function in Spatial
Analyst. Color shading, contour lines and labels
were then added.

It is noteworthy that substantial effort was
devoted to surface interpolations that would
allow weighting of data from cores
preferentially over that of cuttings and
geophysical logs. Combinations of grid
averages, weights, and point buffering applied
within various interpolators were evaluated
during extensive sensitivity analyses and
validation. In the final assessment, too many
negative attributes were associated with what
was considered the optimal core-weighting
technique. As a result, the well data from cores,
cuttings and geophysical logs are all considered
equally in the maps.

Unlike hand-drawn contours, the smoothed
contours generated from krige-interpolated
surfaces do not always reflect highly anomalous
elevation data points. While this may be
considered a disadvantage, it is substantially
outweighed by numerous advantages of the
digital products developed during this study: 1)
the interpolated surfaces are supported by
accuracy and precision statistics, 2) the
calculated grids can be used in a variety of
groundwater flow models and 3D applications,
3) GIS compatibility exists, including inherent
scalability and flexibility, and 4) the maps can
be readily updated with new information. As a
result, manual modification (editing) of the
contours to reflect anomalous values would
create discrepancies between the maps and the
grid coverages. In cases where contour
adjustments were deemed necessary to reflect
sharp-relief surface trends (as opposed to single
anomalous well values), synthetic control points
were added to improve map accuracy while
maintaining consistency with the calculated
grids.











Table 3. Summary of krige interpolation statistics for each map; ASE is average standard error of the prediction error; RMS is root mean
square of the prediction error. Gray pattern indicates that the prediction error may be overestimated (i.e., ASE>RMS).

Map Unit Prediction error (1s)J Prediction error (1s; map)4 Map "Grid to Point" Number Model
(s)=surface ASE RMS Mean of the 2 X Mean of Contour Error Calculation of Wells5 Algorithm
(t)=thickness ASE (1s) the ASE (2s) Interval
mean s
Hawthorn Group (s) 23 34 22 44 25 1.64 11 526 Exponential
Hawthorn Group (t) 57 68 56 112 75 -0.25 21 321 Spherical
Peace River (s) 25 35 22 44 25 0.64 9 349 Exponential
Peace River (t) 27 34 37 74 30 0.33 25 324 Exponential
Bone Valley Mbr. (s) 26 35 23 46 40 2.61 10 33 Exponential
Bone Valley Mbr. (t) 7 7 10 20 20 0.26 3 38 Spherical
Arcadia Fm. (s) 29 35 25 50 30 0.7 11 466 Exponential
Arcadia Fm. (t) 67 65 61 122 75 -0.27 19 341 Exponential
Tampa Member (s) 50 39 44 88 50 0.6 11 235 Exponential
Tampa Member (t) 40 40 39 78 50 0.13 30 190 Exponential
Nocatee Member (s) 64 455 110 75 1.11 12 117 Exponential
Nocatee Member (t) 3 3 37 74 50 -0.24 21 105 Exponential
Suwannee Limestone (s) 75 51 68 136 75 0.98 18 414 Exponential
Suwannee Limestone (t) 43 47 37 74 50 0.1 12 265 Exponential
Ocala Limestone (s) 67 47 63 126 75 0.97 14 527 Spherical
Ocala Limestone (t) 34 49 30 60 50 -0.15 10 325 Exponential
Avon Park Fm. (s) 84 53 79 158 100 0.77 13 391 Circular
SAS (t) 25 29 25 50 25 0.41 18 703 Exponential
IA.S/ICU I (s 4 'A 91 4A r5, -1 27 1 4ARR Fvxnnnntial


IAS/ICU (t)
FAS (s)
MFCU (s)


54 108 75 0.02 18 334 Spherical
64 128 75 0.87 16 655 Exponential
167 334 150 0.83 12 101 Spherical


3 krige statistics based on rectangular fit around distribution of wells
4 krige statistics based on irregular extent of mapped unit, which more accurately represents error within the study area
5 total number of wells used to produce each map, including wells (not shown on plates) within the outer 10 mile buffer zone


.'


"`""""""'






FLORIDA GEOLOGICAL SURVEY


Contour Interval Selection

Contour intervals for each map were selected
based on the mean of the ASE for each
respective krige model trimmed to the map unit
extents (Table 3 Footnote 2). If one assumes
normality, the ASE of the prediction error is
essentially the standard deviation (s) of the
interpolated surface and represents a 68 percent
level of significance. If one were to double the
error (i.e., 2s), a 95 percent level of significance
is achieved. To avoid inflating implied accuracy
of the krige surfaces, the contour interval for all
but two maps was selected between Is and 2s.
In other words, the selected contour interval is
always greater than or equal to the mean of the
ASE prediction error, except for the IAS/ICU
thickness map and the MFCU surface map. Per
Table 3, the error for these maps is over-
predicted. For every contour map in this study,
the standard deviation for the "Grid to Point"
calculation described above (Table 3) is less
than the contour interval.

STRATIGRAPHY

The stratigraphic framework of the west-
central Florida peninsula, encompassing the
SWFWMD region, is presented from north to
south in the following geographic subdivisions:
northern region (eastern Levy, western Marion,
Citrus, Sumter, western Lake, Hernando and
Pasco Counties), central region (including
Pinellas, Hillsborough, western Polk, Manatee
and Hardee Counties), southern region
(Sarasota, DeSoto and Charlotte Counties) and
the eastern region (e.g., the Lake Wales Ridge,
including eastern Polk and Highlands Counties).
The framework discussion is subdivided into
lithostratigraphy and hydrostratigraphy, and is
characterized through a series of cross sections
and maps (surfaces and thicknesses). East-west
trending cross sections presented in this report
(see Plate 1 for locations) are ordered from the
north to south (i.e., the northern to southern
regions; Plates 4-19), then north to south within
the eastern region (Plates 20-28). Cross sections
trending north-south are ordered from west to
east as follows: Plates 29 and 30 in the northern
region, Plates 31-35 in the central/eastern
regions and Plates 36 and 37 in the southern


region. Maps of lithostratigraphic units are
presented from oldest to youngest (Plates 38 -
54) and hydrostratigraphic units are presented
from shallow to deep (Plates 55 59).


Lithostratigraphy

Introduction

Structure contour (surface) and isopach maps
(thickness) in this report include Lower Eocene
through Lower Pliocene lithostratigraphic units,
which are described in detail in this section.
Characterization of the mapped units includes
age, lithology, mineralogy, porosity, significant
fossils, distribution, nature of vertical and lateral
contacts, distinguishing gamma-ray activity
responses, relation to hydrostratigraphic units
and environment of deposition. Superjacent and
subjacent lithostratigraphic units (i.e., the
Oldsmar Formation) are also presented.

Eocene Series

Oldsmar Formation

The Lower Eocene Oldsmar Formation
("Oldsmar Limestone" of Applin and Applin,
1944) underlies the entire Florida peninsula.
Miller (1986) describes the Oldsmar Formation
as a white to gray limestone with variably thick
interbeds of gray to light brown, crystalline
dolostone that increases in abundance with
depth. Thin beds of chert and evaporites,
including pore-filling gypsum occur within the
unit (Miller, 1986). Reese and Richardson
(2008) report a glauconite marker horizon that
occurs intermittently within upper -200 ft (- 61
m) of the Oldsmar Formation in the study area.
Porosity types include intergranular,
intragranular and fracture (e.g., "Boulder
Zone"). Braunstein et al. (1988) indicate that
the unit may have an unconformable contact
with the subjacent Cedar Keys Formation;
however, the contact with the overlying Avon
Park Formation is possibly conformable.

In the study area, the Oldsmar Formation
limestones vary from packstone to wackestone.






BULLETIN NO. 68


Dolostone is common as well. The microfossil
Helicostegina gyralis (Figure 11) is common but
not unique to the unit (Miller, 1986). In the
southeastern Florida peninsula, this microfossil
is common within a glauconitic bed that serves
as an excellent geophysical marker (Duncan et
al., 1994). Within the study area, the uppermost
Oldsmar Formation contains gypsum as nodules,
laminations and as pore-filling material. Stewart
(1966) reports "selenite impregnation" in the
unit and proposes that the gypsum is altered
from anhydrite. In some areas, these
gypsiferous, low-permeability carbonates
comprise the upper part of the MFCU, whereas
deeper in the section, the carbonates comprise
the upper part of the LFA. Cander (1994)
suggests that the Oldsmar Formation represents
a shallow subtidal to supratidal carbonate paleo-
environment.

Avon Park Formation

The Middle Eocene Avon Park Formation
(Miller, 1986) occurs in the subsurface
throughout the study area and is the oldest
lithostratigraphic unit exposed in Florida (Scott
et al., 2001). This unit was originally described
by Applin and Applin (1944) as two units, the
Lake City Limestone and the Avon Park
Limestone. Due to the inability (except locally)
to distinguish these two formations based on
lithology or fauna, Miller (1986) proposed that
the term Lake City Limestone be abandoned and
formalized the Avon Park Formation to include
the two units of Applin and Applin (1944).

Lithology of the Avon Park Formation varies
between limestone and dolostone. The
limestone is generally cream to light brown,
poorly to well indurated, variably fossiliferous,
skeletal/peloidal wackestone to grainstone with
minor mudstone. The limestone can be
interbedded with dark brown to tan very-fine to
coarse-grained, vuggy, fossiliferous dolostones.
Incomplete to complete dolomitization of
limestone is also observed. Dolostone textures
range from very fine-grained to coarsely
recrystalized (sucrosic). Minor clay beds and
organic-rich laminations may occur, especially
at or near the top of the unit. Although not
common, sedimentary structures include cross-


beds and burrows. The burrows (Callianassa
sp.) generally occur in the uppermost thinly
bedded updip part of the formation (e.g., crops
out in Levy County). Accessory minerals
include chert, pyrite, celestine, gypsum and
quartz (some as doubly-terminated euhedral
crystals "floating" in vugs). Gypsum tends to be
more abundant with depth. Reese and
Richardson (2008) report a glauconite marker
horizon that occurs intermittently within lower
-200 ft (- 61 m) of the Avon Park Formation.

Porosity in the Avon Park Formation is
generally intergranular in the limestone section.
Fracture porosity occurs in the more densely
recrystallized dolostone and intercrystalline
porosity is characteristic of sucrosic textures.
Pinpoint vugs and fossil molds are present to a
lesser extent. Total porosity measured for 16
Avon Park Formation samples averages 31.7
percent (median = 30.0 percent) and ranges from
22.3 percent to 42.0 percent.

Diagnostic fossils include the foraminifera
Cushmania americana (Dictyoconus
americanus) and Fallotella (Coskinolina)
floridana and the echinoid Neolaganum
(Peronella) dalli (Figure 12). The foraminfer
Fallotella (Dictyoconus) cookei occurs in the
Avon Park Formation as well as the Suwannee
Limestone; however, presence of Cushmania
americana is unique to the Avon Park
Formation. Other fossils include algae,
mollusks and carbonized plant remains (e.g.,
Thalassodendron sp.) (Scott, 2001).

Miller (1986) reports the top of Lower
Eocene rocks (the approximate base of Avon
Park Formation) at depths ranging from -1,000 ft
to -2,400 ft (-304.8 to -731.5 m) MSL within the
study area. The Avon Park Formation varies in
thickness across the study area, from 1,000 ft to
1,600 ft (304.8 to 487.7 m), with the thickest
area occurring along northeastern Polk County
(Miller, 1986). Maximum observed elevations
exceed 50 ft (15.2 m) MSL in northern Polk
County (Plate 20). In the southernmost extent of
the study area, the unit is encountered at depths
exceeding -1500 ft (-457.2 m) MSL (Plate 38).
The area, which is centered along eastern
Charlotte Harbor, may be related to structural
deformation (Winston, 1996).






FLORIDA GEOLOGICAL SURVEY


Figure 11. Helicostegina gyralis, a foraminifer common within the Oldsmar Formation (bar = 1 mm).


The contact relations between the Oldsmar
and Avon Park Formations are generally subtle
and difficult to identify within the study area,
which supports the interpretation that the contact
is possibly conformable (Braunstein et al.,
1988). In general, the contact grades from a
dolostone to a chalky white limestone. In many
cases, however, these characteristics are not
present. A useful faunal indicator of the
transition into the Oldsmar Formation is the
appearance of abundant Helicostegina gyralis
(Figure 12; Miller, 1986). Although this
foraminifer does not exclusively occur in the
Oldsmar Formation, it generally appears in
lowermost Avon Park Formation and increases
in abundance in the Oldsmar Formation
carbonates.

The Ocala Limestone unconformably
overlies the Avon Park Formation throughout
nearly the entire study area; exceptions include
parts of Levy and Citrus Counties (Avon Park
Formation exposures) or where the Ocala
Limestone is absent in the subsurface
(northwestern Osceola County). The contact
between these two units is readily apparent in
many up-dip locations and difficult to determine
down dip. The more obvious contact relations
occur where: 1) lithology of the Avon Park
Formation is tan to brown dolostone, overlain by
white to cream limestone of the Ocala
Limestone (e.g., W-16456 [ROMP 49], Plates


14 and 33; W-9059, Plates 23 and 34) and 2) in
the case where both units are limestone, the
uppermost Avon Park Formation is grain-
supported and contains disseminated organic or
thin (less than 2 inches; 5 cm) beds of peat (in
some cases varying toward lignite), whereas the
lowermost Ocala Limestone is finer grained and
skeletal (e.g., W-720, Plates 6 and 29; W-12943
Plates 12 and 21). Although the Avon Park
Formation is not defined based on bio-
assemblages, additional contact indicators
include the appearance of diagnostic
foraminifera and echinoids listed above, as well
as abundance of coralline algae.

Throughout most of the southwestern part of
the study area, including nearly all of Manatee
and Sarasota Counties, the contact between the
Avon Park Formation and the Ocala Limestone
is dolomitized (e.g., Plate 18) and as a result,
formation boundary delineation is difficult. In
this situation, subtle characteristics can be used
to delineate the two units. Dolomitization of the
limestones with slightly varying textures may
yield differences in dolostone textures and
dolomite grain sizes. Fossil molds are another
useful indicator, because fossil molds of
diagnostic fossils may help narrow the
uncertainty. For example, narrow, discoid vugs
may represent prior Lepidocyclina sp. whereas
smaller cone-shaped vugs may represent where
Cushmania or Fallotella sp. were present prior






BULLETIN NO. 68


Figure 12. Selected diagnostic fossils common within the Avon Park Formation. From left to right:
Cushmania americana (Dictyoconus americanus) (bar = 0.5 mm; Rupert, 1989), Fallotella
(Coskinolina) floridana (bar = 1 mm; photo courtesy of Jonathan Bryan) and Neolaganum
(Peronella) dalli (bar = 15 mm; photo courtesy of Invertebrate Paleontology, Florida Museum of
Natural History [IP/FMNH]).


to dolomitization/leaching (e.g., Plate 27; W-
17056 [ROMP 9]). In rare instances, selective
dolomitization occurs where the original
limestone matrix is dolomitized, however, the
faunal assemblage foraminiferaa and echinoids)
remain as calcite.

Gamma-ray response in the Avon Park
Formation is generally due to variable dolomite
and organic content. In many wells, high
gamma-ray activity at or near the top of the
Avon Park Formation corresponds to thin layers
of organic material (e.g., Plate 16; W-16303
[ROMP TR 7-4]; Figure 10). Similar
observations have been made east of the study
area (Davis et al., 2001). In cases where the top
of the Avon Park Formation has been
dolomitized or recrystallized, this organic-
associated gamma-ray peak tends to be a
broadened, more subdued signal. The degree to
which the signal remains is likely a function of
the extent of recrystallization and amount of
organic impurities remaining in the carbonate.
Relative to the overlying Ocala Limestone, the
Avon Park Formation gamma-ray signature has
higher background count rates and is more
variable throughout the unit. In general, a
relatively higher gamma-ray peak is observed at
the top of the Avon Park Formation throughout
the study area, except for the west-central


region, including northern Hillsborough and
Pinellas Counties as well as eastern Polk and
northern Manatee Counties. Several gamma-ray
logs from wells in the study area also exhibit a
peak at depths greater than 350 ft (106.7 m)
below the top of the unit. Preliminary analysis
attributes this peak to organic content.

All major parts of the FAS (the UFA, MFCU
and LFA) can include the Avon Park Formation.
The "Avon Park permeable zone" (Reese and
Richardson, 2008) generally occurs 200 to 400 ft
(60.9 m to 121.9 m) beneath the top of the Avon
Park Formation in the study area, and is
analogous to the "Avon Park highly permeable
zone" reported by Hutchinson (1992) for
southwestern Florida. Reese and Richardson
(2008) map this permeable zone throughout
most of the southern half of peninsular Florida,
describing it as a thick dolostone unit with
interbedded limestone and dominated by fracture
porosity that may occur in either the UFA or the
LFA.

With increasing depth in the Avon Park
Formation, interbedded and intergranular
evaporites (gypsum/selenite and anhydrite)
reduce formation porosity and permeability
throughout much of the region. Water-quality
data, (Sacks and Tihansky, 1996; Jack Hickey,






FLORIDA GEOLOGICAL SURVEY


personal communication, 2004), geophysical
and lithologic evidence indicate that most of the
MFCU surface (Plate 59) correlates with the
middle to lower carbonates of the Avon Park
Formation. In parts of Marion, Osceola and
Pinellas Counties, however, the MFCU occurs in
the upper third of the unit. In the southern
region, a shallower discontinuous MFCU unit
occurs within the middle to upper part of the
formation (Plate 59). The relation between the
Avon Park Formation and the MFCU in east-
central part of the study area (i.e., the vicinity of
southeastern Polk County; Plate 59) requires
further data and research.

The Avon Park Formation was deposited
within a broad, distally steepened carbonate
platform (Budd, 2002). The deposition is
characterized by peritidal carbonate sediments
that may be significantly dolomitized. Highly
cyclical deposits in supratidal to shallow
subtidal environments are represented in the
vertical sediment sequence (Randazzo et al.,
1990; Budd, 2002). The sediments reflect
repeated short-term changes in relative sea level
throughout Middle Eocene deposition
documenting transgressive, regressive and open
marine to shoreline cycles (Randazzo et al.,
1990). Some researchers propose that
dolomitization within the Avon Park Formation
took place during or proximal in time to
deposition (e.g., Randazzo and Hickey, 1978;
Cander, 1994). Miller (1986) suggests that thin
evaporite beds deposited during the Middle
Eocene may have been formed in a tidal flat or
sabkha environment.

Ocala Limestone

The Upper Eocene Ocala Limestone was first
named by Dall and Harris (1892). Puri (1953)
later proposed three separate formations: the
Inglis, Williston and Crystal River Formations,
which were based upon distinct faunal
assemblages. In 1953, Puri elevated the
sequence to Group status. Miller (1986) noted
that these formations were neither easily
recognizable nor mappable and therefore applied
the name Ocala Limestone; however, he
acknowledged that a two-fold division (upper


and lower Ocala Limestone) proposed by Applin
and Applin (1944) was still in use. Recognizing
the biostratigraphic basis of the division on
which the Ocala Group was based, Scott (1991)
identified the Ocala Limestone as a formation in
accordance with the North American
Stratigraphic Code. Despite this rather complex
history in nomenclature leading to recognition of
the unit as a single formation, upper and lower
Ocala Limestone lithologies are generally
recognized.

The lower Ocala Limestone varies from
white to light gray and is variably indurated,
ranging from a packstone to a grainstone.
Where present, dolomite content increases with
depth in the Ocala Limestone, especially in the
southwestern part of the study area where the
base of the unit is often dolomitized (see Avon
Park Formation, p. 31, for more details).
Gaswirth (2004) also noted this pattern and
documented textural end-members within these
dolostones: 1) friable, light to medium brown,
sucrosic and 2) indurated, dark gray to dark
brown, dense, crystalline. The upper part of the
Ocala Limestone varies from white to light
orange and tends to be more mud-supported
(i.e., mudstone to wackestone) and chalky.

Mineralogy of the Ocala Limestone unit is
predominantly calcite, and to a lesser extent,
dolomite. Siliciclastics are rare; however, chert
occurs throughout the formation and is generally
more common where the unit occurs at or near
land surface. Trace amounts of organic and
clay (Green et al., 1995) likely represent post-
depositional infilling. Pyrite is also present as a
trace mineral, but to a lesser extent than the
overlying Suwannee Limestone or underlying
Avon Park Formation. Sedimentary structures
in the Ocala Limestone include cross bedding,
fine laminations and bioturbation. The latter is
dominant at the base of the unit in the form of
burrows (Loizeaux, 1995). The Ocala
Limestone has a diverse fossil assemblage
(Figure 13), including Lepidocyclina sp.,
Nummulites (Operculinoides) sp., milliolids,
bryozoans, gastropods, mollusks, pelecypods,
echinoids (e.g., Eupatagus antillarum) and
Rotularia (Spirolina) vernoni.






BULLETIN NO. 68


Figure 13. Selected diagnostic fossils within the Ocala Limestone. Top photo: Eupatagus
antillarum (bar = 2.5 cm; photo courtesy of IP/FMNH). Middle row, left: Nummulites
(Operculinoides) sp. (bar = 1mm; photo courtesy of Jonathan Bryan), right: Rotularia (Spirolina)
vernoni (bar = 1 cm, photo courtesy of IP/FMNH). Bottom: Lepidocyclina ocalana, (bar = 3 mm);
(A) from Cushman (1920), (B) from Rupert (1989).






FLORIDA GEOLOGICAL SURVEY


Grainstones of the Ocala Limestone comprise
the most permeable zones in the UFA. Porosity
within the unit is generally moldic and
intergranular with occasional macrofossil molds.
Secondary porosity owing to carbonate
dissolution is extensive and has greatly
enhanced permeability, especially where
confining beds are breached or absent (Berndt et
al., 1998). Based on analyses of 70 samples,
total porosity of the Ocala Limestone averages
39.8 percent (median = 41.0 percent) and ranges
from 17.6 percent to 53.5 percent. Of the end-
member dolostone lithologies reported by
Gaswirth (2004), porosity of the induratedd"
type averages 24 percent (n=30) and the
"sucrosic" type averages 35 percent (n=28),
(Gaswirth et al., 2006).

The Ocala Limestone occurs throughout the
study area except where locally removed by
erosion on the Ocala Platform in the
southeastern part of Levy County and
southwestern part of Marion County. In
southwestern Orange County and northwestern
Osceola County, the Ocala Limestone is also
absent possibly due to structural offset and
erosion. Miller (1986) proposes a graben-like
fault system striking along the Polk-Osceola
County boundary; however, data presented
herein does not confirm its presence. An area of
"locally absent" Ocala Limestone (Plate 39)
does, however, approximately coincide with
Miller's (1986) fault-bound area. The top of the
Ocala Limestone occurs at or near land surface
in the northern region (Figure 2) and deepens to
approximately -1275 ft (-388.6 m) MSL in the
southern region (Plate 39). The thickness of the
unit exceeds 400 ft (121.9 m) in Charlotte and
Highlands Counties (Plate 40). This
lithostratigraphic unit is generally thought to be
bound by unconformities (Braunstein et al.,
1988; Loizeaux, 1995).

Two proposed structural features are
significant with regard to the Ocala Limestone.
A fault striking northwest in northwestern Polk
County is proposed by Carr and Alverson
(1959). Vernon (1951) and Stewart (1966)
present contour maps of the "Inglis" (i.e., basal
Ocala Limestone) suggesting local offset in the
same area with the shallower "Inglis" sediments
toward the northeast. This offset is consistent


with Carr and Alverson's (1959) proposed fault.
Although local thickness variations of the Ocala
Limestone in this area are generally consistent
with the proposed fault, the present study does
not have sufficient well control to confirm the
hypothesis. A fault proposed by Winston (1996)
that trends northwest across Charlotte Harbor
may be related to the deepening and thickening
of the Ocala Limestone in this area.

Contact relationships between the Ocala
Limestone and Avon Park Formation are
discussed under Avon Park Formation, p. 31. In
the northern and central regions, the boundary
between the Ocala Limestone and the overlying
Suwannee Limestone is usually not difficult to
distinguish. Not only is the gamma-ray
character different (Figure 10), but the
uppermost Ocala Limestone is generally
"cleaner" (i.e., significantly less non-calcitic
material) finer-grained and more skeletal than
the overlying unit. In some cases, Ocala
Limestone lithoclasts are found at the base of the
Suwannee Limestone (Loizeaux, 1995).
Moreover, the fossil assemblage differs
significantly, with the disappearance of
Lepidocyclina ocalana and the appearance of
Fallotella sp. (Suwannee Limestone) shallower
in the section. There are, however, areas where
the two units are difficult to distinguish. The
transition from Ocala Limestone to Suwannee
Limestone can be gradational toward the south,
showing some evidence of interbedding and thus
a possible conformable contact. Moreover,
some areas contain basal Suwannee carbonates
that range from fine-grained grainstones to
mudstones, which can be difficult to distinguish
from the underlying, sometimes altered, chalky
mudstones and wackestones of the upper Ocala
Limestone. Torres et al. (2001) and Brewster-
Wingard et al. (1997) have also noted that the
boundary is often difficult to pinpoint and
suggest that foraminifera are often useful to
distinguish the units.

Gamma-ray logs for the Ocala Limestone
consistently exhibit very low gamma-ray activity
(low, background-level count rates) and
relatively fewer peaks than the overlying and
underlying formations (Figure 10). In cases
where the Ocala Limestone is dolomitized, the






BULLETIN NO. 68


gamma-ray logs may exhibit a slightly higher
and more sporadic signature (Arthur et al.,
2001a). Many peaks in the gamma-ray logs for
this unit correlate with the presence of trace
organic or pyrite (e.g., W-12640 [ROMP 59];
Plate 21 and 32).

In peninsular Florida, Ocala Limestone
deposition is interpreted to have occurred on a
homoclinal distally steepened carbonate ramp in
shallow (probably less than 10 m [32.8 ft])
subtidal to intertidal, somewhat high-energy,
open marine environment (Randazzo et al.,
1990; Cander, 1994; and Loizeaux, 1995). The
Ocala Limestone represents a more constant and
stable depositional environment than the
underlying Avon Park Formation (Randazzo et
al., 1990). Specifically, deposition of the Ocala
Limestone occurred during a long-term eustatic
high stand representing an overall transgressive
sequence of sedimentation with shoreline
progradation (Randazzo et al., 1990; Loizeaux,
1995). The lower Ocala Limestone represents a
deepening upward sequence with the sediments
becoming muddier through time and then
shoaling in the uppermost Ocala (Randazzo et
al., 1990). This appears to coincide with the
post-middle Eocene marine transgressions
followed by a fall in eustatic sea level at the end
of late Eocene (Loizeaux, 1995).

Oligocene Series


Suwannee Limestone

The Lower Oligocene Suwannee Limestone
was first identified by Cooke and Mansfield
(1936). This formation ranges from light-gray
to white, variably moldic packstones and
grainstones. Carbonate grains are generally
miliolids and peloids. Small amounts of sand (<
3 percent) and clay generally occur within the
uppermost part of the unit when overlain by
Hawthorn Group sediments. South of the study
area, however, Missimer (2002) reports local
sand beds in the Suwannee Limestone. Trace
amounts of pyrite and organic (finely
disseminated and as laminations) also occur
throughout this formation (Arthur et al., 2001b;
Price, 2003). The Suwannee Limestone is also
variably dolomitized. For example, Green et al.,


(1995) noted a relatively consistent dolostone or
dolomitic limestone bed (10-20 ft thick [-3-6
m]) occurring within the lower third of the unit
in the central part of the study area. Chert is
present throughout the unit, especially within the
updip part of the unit. In Hernando County, for
example, partial silicification of the limestone is
observed, leaving echinoids in their original
calcite form. Sedimentary structures include
cross bedding and bioturbation (Budd, 2002).
Porosity types include moldic and intergranular.
Measured total porosity, based on analysis of 29
samples, averages 36.3 percent (median = 37.1
percent) and ranges from 2.3 percent to 55.8
percent. Fossils within the Suwannee
Limestone include mollusks, gastropods,
echinoids (most commonly the index fossil
Rhyncholampus gouldii), abundant miliolids and
other benthic foraminifera including Fallotella
(Dictyoconus) cookei, Discorinopsis gunteri
(Figure 14) and Fallotella (Coskinolina)
floridana (Figure 12).

For the most part, the Suwannee Limestone
unconformably overlies the Ocala Limestone
and is unconformably overlain by Hawthorn
Group sediments; however, there exists some
question regarding the lateral extent of both
unconformities. The contact between the
subjacent Ocala Limestone and the Suwannee
Limestone can be locally gradational, showing
some evidence of interbedding. In some areas,
the lower Suwannee Limestone increases in
carbonate mud content, which can be difficult to
distinguish from the sometimes chemically
weathered, chalky upper Ocala Limestone.
Torres et al. (2001) and Brewster-Wingard et al.
(1997) have also noted that the boundary is often
difficult to pinpoint. These researchers, as well
as the authors of this report, suggest that
foraminifera are often useful to distinguish the
units.

The upper contact of the Suwannee
Limestone is locally gradational with the
overlying Tampa Member (Arcadia Formation)
in northeastern Hillsborough and Pinellas
Counties. Researchers faced with the difficulty
of making formation picks in this area have
come to informally refer to this transitional zone
as "SuwTampaHaw" (Tom Scott, personal
communication, 2004). The Suwannee
Limestone is also locally overlain by green clays






FLORIDA GEOLOGICAL SURVEY


Figure 14. Selected diagnostic Suwannee Limestone fossils. Top row left: Fallotella (Dictyoconus)
cookei (bar = 1 mm; from Rupert, 1989), right: Rhyncholampus gouldii (bar = 2.5 cm, photo
courtesy of Sean Roberts). Bottom row left: Discorinopsis gunteri (bar = 2 mm; Cooke, 1945),
right: milliolid (bar = 1 mm; photo courtesy Jonathan Bryan).


comprising the base of the Tampa Member
(Arcadia Formation) in parts of northern and
central Pinellas County, south-central
Hillsborough County and eastern Polk County.
In other areas, lack of phosphate sand in the
Suwannee Limestone distinguishes it from
overlying phosphatic (i.e., non-Tampa Member)
Hawthorn Group sediments. South of the study
area, however, Suwannee Limestone carbonates
include minor occurrences of blackened
(possibly francolite) discontinuity surfaces
(Missimer, 2002).

The northern extent of the Suwannee
Limestone occurs in Citrus County based on
isolated outcrops and discontinuous borehole
data. The approximate northern limit of laterally
continuous Suwannee Limestone, however,
occurs in southernmost Citrus County (Plates 41


and 42). In the eastern region, the subcrop limit
occurs beneath the Lake Wales Ridge. In
Highlands County, the eastern extent of the unit
is uncertain and denoted with a dashed line
(Plates 41 and 42). Two wells east of the line
contain limited thicknesses of the Suwannee
Limestone; however, nearby wells deep enough
to have encountered the unit do not contain it.
This suggests the two wells represent outliers.
Maximum elevation of the unit exceeds 75 ft
(22.9 m) MSL in parts of Hillsborough and Polk
Counties as well as along the Brooksville Ridge,
while in the southern region, depths exceed -825
ft (-251.5 m) MSL (Plate 41). Maximum
thickness of the Suwannee Limestone in the
study area exceeds 450 ft (137.2 m) in south-
central Charlotte County (Plate 42).

Evidence supporting previously identified


h ie e nt
L__ DicKjjMb^Bwisgteri I






BULLETIN NO. 68


faults in the Suwannee Limestone exists to some
degree within two areas. The feature most
supported by the data presented herein is an
inferred northwest-striking fault in northwestern
Polk County (Figure 3). The Suwannee
Limestone thickness map (Plate 42) indicates an
abrupt change in thickness; wells reflecting
more than 100 ft (30.5 m) of the unit are
proximal to wells that contain no Suwannee
Limestone even though the wells are deep
enough to have encountered the unit (assuming
similar regional dip). The strike and polarity of
this particular feature, indicated as an inferred
fault on Plate 41 and 42, roughly agrees with a
fault proposed by Pride et al. (1966). Northeast
of the fault, the Suwannee Limestone is reported
to occur as exposed remnant boulders in Sumter
County (Campbell, 1989).

A second inferred fault may occur along the
updip limit of the Suwannee Limestone in
northeastern Hernando County (Figure 3).
Vernon (1951) reports a fault intersecting the
"Inglis Member" in the area, with the upthrown
side to the northeast. Data represented in Plates
41 and 42 support the location and polarity of
Vernon's (1951) fault for the Suwannee
Limestone. Thicknesses greater than 50 ft (15.2
m) terminate along the northeastern subcrop
limit of the unit (Plate 41 and 42). In the
Charlotte Harbor area, the "North Port" fault
(Winston, 1996) may have affected the
Suwannee Limestone surface and thickness,
similar to that of the Ocala Limestone and Avon
Park Formation. Other faults and lineaments are
reported in this area (Hutchinson, 1991;
Winston, 1996; Michael Fies, personal
communication, 2007) suggesting a complex
geologic setting.

The Suwannee Limestone is characterized by
a gamma-ray log response (i.e., activity) that is
generally more variable within the lower half of
the unit (e.g., Plate 11 and 12; Figure 10).
Relative to the Ocala Limestone, it has an
overall higher background rate and exhibits
much more variability. This variability is likely
due to higher amounts of dolomite, organic
material and other non-calcitic constituents in
the Suwannee Limestone relative to the Ocala
Limestone. Although the gamma-ray log is
generally useful for providing corroborative


evidence for the lithostratigraphic boundary
between the Eocene Oligocene carbonates, use
of the logs for determination of the upper
boundary of the Suwannee Limestone is not
always as straightforward. For example, where
the Tampa Member (Arcadia Formation) is in
contact with the Suwannee Limestone, gamma-
ray signatures for the two units are quite similar,
both in their background count rates and
distribution of peaks (e.g., Plate 31, W-15204
[TR14-2] and Plate 33, W-16740 [ROMP 39]).

A generally consistent pattern in the
Suwannee Limestone gamma-ray logs,
especially for wells in Gulf-coastal counties, is
the presence of a 50- to 100-ft (15.2 to 30.5 m)
thick interval of high gamma-ray activity within
the central to lower parts of the Suwannee
Limestone. This interval varies in thickness and
depth and apparently does not correlate with a
given stratigraphic horizon. Inspection of
lithologic logs suggests that this high gamma-
ray activity zone is associated with dolomite
and/or minor organic content.

The Suwannee Limestone, where present,
comprises most of the FAS surface; exceptions
being where hydraulic continuity exists between
the Tampa Member (Arcadia Formation) and
Suwannee Limestone in Pasco, Pinellas, most of
Hillsborough and northern Manatee Counties
(Figure 8). Along the updip limit of the Tampa
Member in Pasco County, the top of the FAS
includes the Tampa Member (where present)
and the Suwannee Limestone (Figure 8).
Grainstones within the Suwannee Limestone are
among the most permeable zones in the UFA.

Suwannee Limestone deposition occurred in
shallow open marine to peritidal environments
on the Florida Platform (Cander, 1994) until the
Late Oligocene sea-level low stand (Hammes,
1992). During deposition of the unit in the study
area, the Georgia Channel System (Huddlestun,
1993) acted as a barrier to a southward influx of
plastic sediments from the Appalachian
Mountains. Deposition of the predominantly
skeletal lithologies was cyclic and controlled by
the pre-existing topography as well as
fluctuating sea level. Restricted marine facies
and skeletal shoal facies developed on previous
highs and deeper subtidal facies occurred in the
lows. Hammes (1992) describes the Suwannee






FLORIDA GEOLOGICAL SURVEY


Limestone as three megacycles each composed
of several shallowing upward cycles: 1) the
outer ramp characterized by skeletal-rich, grain
supported to muddy, open-marine, shallow and
deep-ramp facies, 2) shallow ramp facies -
composed of wave dominated skeletal banks and
shoal complexes and shallow and deep subtidal
lagoonal deposits, and 3) restricted marine -
deposition in a restricted marine, brackish
lagoon and mud-rich tidal flat environment.

Oligocene-Pliocene Series

Hawthorn Group

Hawthorn Group sediments range in age
from mid-Oligocene (Brewster-Wingard et al.,
1997) to Early Pliocene (Scott, 1988; Covington,
1993; Missimer et al., 1994) and generally
consist of phosphatic siliciclastics (sands, silts
and clays) and carbonates. Trace amounts of
pyrite occur throughout the Hawthorn Group
section in southwestern Florida (Lazareva and
Pichler, 2007). In the study area, the Hawthorn
Group consists of the Arcadia Formation, the
Peace River Formation and undifferentiated
sediments, all of which generally lie
unconformably above the Suwannee Limestone
and unconformably beneath undifferentiated
Pliocene and younger sands, shells and clays.
Benthic foraminifera characteristic of the
Hawthorn Group include Archaias sp., Sorites
sp., Amphistegina lesson and Cassigerinella
(Cassidulina) chipolonsis (Figure 15).
Predominant formational members of the
Hawthorn Group present in the study area
include the Tampa and Nocatee Members
(Arcadia Formation) and the Bone Valley
Member (Peace River Formation). The extent of
all Hawthorn Group sediments (Plate 43)
generally includes those areas where
undifferentiated confining beds of the IAS/ICU
(Plate 56) are present beyond the mapped extent
of the Arcadia and Peace River Formations
(Plates 45 and 51, respectively) such as Marion
County, Pinellas County and central Pasco
County. The maximum observed thickness of
the Hawthorn Group exceeds 825 ft (251.5 m) in
south-central Charlotte County (Plate 44).

The Hawthorn Group was deposited in a
shallow marine to nonmarine fluvial and deltaic
environment that prograded over the older


carbonate platform (Scott, 1988; Ward et al.,
2003). Similar to other units mapped in this
study, the top of the Hawthorn Group can
demonstrate variable local relief, as exhibited by
its irregular erosional and karstic surface (Berndt
et al., 1998). Based on mineralogy of Hawthorn
Group sediments, incipient stages of
phosphogenesis occurred during the Late
Oligocene during deposition of the lower
Arcadia Formation (Brewster-Wingard et al.,
1997). Sea-level fluctuations strongly
influenced deposition and exerted a major
control on phosphogenesis and sedimentation
(Riggs, 1979a, 1984; Compton et al, 1993).
During sea-level transgressions a large part of
the Florida platform was submerged.
Meandering of the Gulf Stream resulted in
upwelling over the platform, which increased
organic productivity and enhanced
phosphogenesis in the shallow waters of the
shelf (Compton et al, 1993). Maximum
phosphorite precipitation is thought to have
occurred in shallow-water coastal and nearshore
shelf platforms or other submarine topographic
highs (Riggs, 1979a). Sea-level fluctuations and
ocean currents facilitated transport, deposition
and concentration of phosphate grains (Scott,
1988, 1992b). Primary depositional features
such as graded bedding and cross beds provide
evidence of this high-energy depositional
environment (Scott, 1988). The height of
phosphate deposition and reworking was
synchronous with Peace River Formation
deposition (Middle to Early Pliocene).

Arcadia Formation

The Upper Oligocene (Brewster-Wingard et
al., 1997) to Middle Miocene Arcadia Formation
is comprised of a yellowish gray to white,
variably sandy (quartz and phosphorite)
carbonate with interbeds of siliciclastic-
dominant sediments. Although limestone is
present, dolostones are most common, ranging
in grain size from microcrystalline to medium
sand, with the more coarse material being
sucrosic. Minor clays and chert beds (some
comprised of silicified clay) also occur
(Upchurch et al., 1982; Scott, 1988). Porosity
types include intergranular and moldic.






BULLETIN NO. 68


Figure 15. Diagnostic foraminifera in Hawthorn
right bar = 1 mm; bottom row, bar = 0.5 mm.

Measured total porosity of 25 Arcadia
Formation samples averages 34.1 percent, with a
median value of 32.4 percent and a range from
12.4 percent to 54.5 percent.

The updip limit of the unit occurs in northern
Pasco and Polk Counties where maximum
elevations exceed 90 ft (27.4 m) MSL (Plate 34
and 45). The top of the Arcadia Formation
occurs at depths exceeding -270 ft (-82.3 m)
MSL beneath the Lake Wales Ridge in the
southeastern part of the study area. The unit
ranges in thickness to greater than 750 ft (229
m) in south-central Charlotte County (Plate 46).
Sporadically throughout much of the central and
southern regions, the Arcadia Formation


Group units. Upper left bar = 0.1 mm; upper


(undifferentiated) is observed below the Tampa
and Nocatee Members. In several wells, the
contacts between the Tampa and Nocatee
Members and the underlying Arcadia Formation
(undifferentiated) are gradational. The Arcadia
Formation is unconformably overlain by the
Peace River Formation (where present);
however, apparent gradational contacts between
these two units are locally observed.

In general, the Arcadia Formation comprises
the most permeable parts of the IAS/ICU in the
study area (see IAS/ICU, p. 57, for more details).
In addition, the uppermost part of the FAS is
comprised of the Tampa Member where it is in
hydraulic connection with the subjacent






FLORIDA GEOLOGICAL SURVEY


Suwannee Limestone (Figure 8).

Gamma-ray activity in the Arcadia
Formation is distinctive, with strong gamma-ray
peaks characterizing the upper undifferentiated
part of the unit (e.g., W-16784 [ROMP 33],
Plates 16 and 37; Figure 10). Lithostratigraphic
members within and below the formation are
characterized by significantly weaker gamma-
ray responses. For example, where the
undifferentiated Arcadia Formation overlies the
Suwannee Limestone, the gamma-ray response
for the older unit is often contrastingly low in
gamma-ray activity (e.g., W-15683 [TR 3-3],
Plate 19 and W-15333 [TR 2-1], Plates 19, 28
and 37). Although the high gamma-ray activity
sequence in the Arcadia Formation is distinctive,
it is not always useful as a diagnostic tool for
identifying the upper formational boundary.
Phosphate lag deposits locally comprising the
base of the Peace River Formation have gamma-
ray peaks as high as that of the Arcadia
Formation.

Deposition of the Arcadia Formation is
somewhat unique owing to its composition of
mixed carbonate and siliciclastic sediments. In
most depositional environments, an influx of
siliciclastic sediments usually inhibits the
production of carbonates. During the Oligocene,
siliciclastics began to deposit along the Florida
Platform (Hammes, 1992; Missimer, 2002).
This influx of siliciclastics, during low sea-level
stands, began to slowly bypass the Georgia
Channel System (Huddlestun, 1993) as it filled.
By Late Oligocene the lower part of the Arcadia
Formation was being deposited and a more
continuous influx of quartz sand was occurring
(Missimer and Ginsburg, 1998). These
siliciclastics were transported south several
hundred kilometers to the southern part of the
Florida carbonate platform by longshore currents
(Scott, 1988; Missimer and Ginsburg, 1998).
The rate of siliciclastic transport was initially
episodic and sufficiently low to minimize
interruption of the production of carbonates.
Differences in shoreline positions caused by
fluctuating sea levels allowed siliciclastics to
mix over a broad area. Mixing of the carbonates
and siliciclastics was achieved by tidal transport,
storms, longshore currents, bioturbation and
aeolian processes (Scott, 1988; Missimer and


Ginsburg, 1998; Missimer, 2002). Missimer and
Ginsburg (1998) list three important factors that
allowed the homogenized, co-deposition of
Arcadia Formation carbonates and siliciclastics
to occur: 1) a relatively slow rate of siliciclastic
sediment influx, 2) the lack of mud or clay, and
3) marine transport without river or stream
transport. Freshwater input would have caused
an increase in finer-grained siliciclastics (e.g.,
silts and clays), increased turbidity and
decreased salinity, all of which would have
diminished carbonate production.

Noteworthy topographic features occur along
the surface of the Arcadia Formation. In the
Tampa Bay area, interpreted seismic data
indicate subsurface relief of up to -197 ft (60 m;
Hine et al., in press). These features are
attributed to "spatially restricted, semi-enclosed,
siliciclastic-filled karst" that may coalesce into
larger collapse systems (Hine et al., in press). A
karst basin identified in their study due south of
the Pinellas County peninsula in Tampa Bay
correlates well with a trough extending
northward into the peninsula (Plate 45; see also
Tampa Member surface map, Plate 49).

Along the southern part of the Lake Wales
Ridge, the Arcadia Formation deepens sharply
(Plate 45). This elongate depression (or trough)
also occurs in the overlying Peace River
Formation (Plate 51). Although topographic
relief of the troughs are similar (-175 to -200 ft;
-53 to -61 m), the Arcadia Formation exhibits
little evidence of thinning, unlike the Peace
River Formation (Plate 52). Periods of erosion
(scouring?) or non-deposition owing to sea-level
fluctuations and paleo-ocean currents are likely
factors contributing to the origin of this trough.
Miocene-Pliocene structural control of the
feature is not indicated by the thickness of either
formation. The thickness of post-Hawthorn
Group sediments (see Plate 55 for
approximation) suggests that the trough may
have become a depoaxis for Pliocene-
Pleistocene siliciclastics.

A third significant topographic feature occurs
in south-central Charlotte County, where the
surface of the Arcadia Formation deepens to
more than 200 ft (60.9 m) MSL and notably
thickens to more than 700 ft (213 m; Plates 45






BULLETIN NO. 68


and 46). Locations of depocenters within
subjacent lithostratigraphic units occur in
roughly the same locale: the Ocala Limestone,
Suwannee Limestone and Hawthorn Group
deepen in this area (Plates 39, 41 and 43,
respectively), and the units thicken as well
(Plates 40, 42 and 44, respectively). This basin
is also observed in the surface of the Avon Park
Formation (Plate 38); however, due to lack of
well control, Miller's (1986) Middle Eocene
maps do not reflect this feature. These
observations suggest that the area experienced
continued subsidence and infilling from Middle
Eocene through at least Late Miocene.
Alternatively, the apparent depocenters may
have structural control owing to the proximity of
the "North Port" fault (Winston, 1996).

Nocatee Member

The Upper Oligocene (Brewster-Wingard et
al., 1997) Nocatee Member of the Arcadia
Formation is an interbedded sequence of quartz
sands, clays and carbonates all containing
variable amounts of phosphate (Scott, 1988) that
generally average five percent but locally can
reach ten percent or more. The unit is
predominately siliciclastic and generally
interbedded with lower percentages of
carbonate. Original macrofossil material is not
common in this unit; however, fossil molds of
mollusks, algae and corals are observed.
Diatoms are commonly found within the clay
units. Porosity of the Nocatee Member is
generally intergranular, with highly variable
permeability. Total porosity of five core
samples from the Nocatee Member average 27.5
percent (median =24.7 percent) and range from
20.4 percent to 35.4 percent.

The subcrop extent of the Nocatee Member
includes west-central Polk County south to
Charlotte and Glades Counties and extends as
far west as central Sarasota County. The
northeastern limits of the unit are generally well
defined and comprise a stratigraphic pinchout
(e.g., Polk and Highlands Counties); however,
the southwest extent is more subjective as the
unit grades laterally into the undifferentiated
Arcadia Formation, or locally into the Tampa
Member. In an area extending south from


southwestern Polk County, the Nocatee Member
is conformably overlain by the Tampa Member
of the Arcadia Formation. Elsewhere in the
study area, the upper and lower limits of the
Nocatee Member are gradational into the
undifferentiated Arcadia Formation.

The top of the Nocatee Member ranges in
elevation from greater than 50 ft (15.2 m) MSL
in west-central Polk County to depths exceeding
-600 ft (-183 m) MSL in the southeastern part of
the study area (Plate 47). Although the Nocatee
Member ranges in thickness to more than 240 ft
(73.2 m), it averages approximately 75 ft (22.9
m) thick (Plate 48).

Gamma-ray activity within the Nocatee
Member is generally less than or equal to that of
the overlying Hawthorn Group units (i.e., Tampa
Member and Arcadia Formation; e.g., Figure 10
and Plate 26). Where the Nocatee Member is
underlain by (and generally grades into) the
undifferentiated Arcadia Formation, gamma-ray
logs are not as useful in distinguishing between
the two units. On the other hand, where the
Nocatee Member overlies the Suwannee
Limestone, the gamma-ray activity can be very
useful for distinguishing the two units.

Although most of the Nocatee Member
correlates with the IAS/ICU, this
lithostratigraphic unit is hydraulically connected
to the UFA within part of DeSoto County
(Figure 8) and thus locally comprises the
uppermost UFA in those areas.

The Nocatee Member was deposited on the
southeast edge of the carbonate bank prior to
and during deposition of the Tampa Member.
The Nocatee represents a higher energy, more
open near-shore environment and grades
westward into a very sandy facies of the
undifferentiated Arcadia Formation and
northwestward into the carbonate facies of the
Tampa Member (Scott, 1988).

Tampa Member

The Upper Oligocene to Lower Miocene
(Brewster-Wingard et al., 1997) Tampa Member
of the Arcadia Formation is white to yellowish
gray in color and ranges from a wackestone to






FLORIDA GEOLOGICAL SURVEY


packstone with varying amounts of quartz sand
and clay (Scott, 1988). Minor phosphate (less
than 3 to 5 percent), dolomite and chert
(siliceous limestone, silicified corals; see also
Upchurch et al., 1982) are also observed. Fossil
molds of foraminifera, mollusks, gastropods and
algae are all common within the Tampa Member
(Scott, 1988). Pinkish gray to light olive gray
dolostones also occur with a similar accessory
mineral assemblage and fossil assemblage as the
limestones. Thin sand and clay beds can be
found sporadically within the unit (Scott, 1988).
Porosity of the Tampa Member is generally
intergranular and moldic, with measured total
porosity values (17 samples) ranging from 10.4
percent to 49.6 percent, averaging 32.3 percent
(median value =33.6 percent).

The subcrop limit of the Tampa Member
extends from Pasco County to the northernmost
part of Charlotte County and eastward into the
western half of Polk, DeSoto and Hardee
Counties (Plate 49 and 50). The top of the
Tampa Member ranges from more than 100 ft
(30.5 m) MSL in Pasco County to deeper than -
350 ft (-107 m) MSL in Sarasota County (Plate
49) and exhibits variable thickness. The
maximum observed thickness of the Tampa
Member is 292 ft (89.0 m) (Plate 17; W-14882
[TR 6-1]); however, some would propose that
the lower Tampa Member in this well is more
characteristic of the undifferentiated Arcadia
Formation.

In the northern third of its extent, the Tampa
Member overlies the Suwannee Limestone and
the contact appears to be locally conformable.
In Pinellas and northwest Hillsborough
Counties, for example, samples have been
informally referred to as "SuwTampaHaw" due
to the subtle transition between the units. In the
central and southern regions, this unit overlies
the Arcadia Formation (undifferentiated), or the
Nocatee Member of the Arcadia Formation. In
many wells, the transition between the Tampa
Member and the underlying Arcadia Formation
is gradational, with phosphorite content
increasing with depth. The Tampa Member is
conformably overlain by the Arcadia Formation
(undifferentiated) in many areas (e.g., Plate 14);
however numerous exceptions exist. In parts of


Pasco and northern Hillsborough Counties, the
unit is unconformably overlain by UDSC or
undifferentiated clay-rich Hawthorn Group
sediments. East of this area, the Tampa Member
is unconformably overlain by the Peace River
Formation. Toward the east and south, the
Tampa Member facies grades laterally into the
Arcadia Formation. In Sarasota County, the unit
appears to grade laterally into the Nocatee
Member as it becomes increasingly more sandy.
Scott (1988) also reports this lateral facies
change in northern Hardee County.

The Tampa Member generally exhibits
variable gamma-ray activity (Figure 10; Arthur
et al., 2001a) that limits the value of this log to
discern unit boundaries. For example, when
underlain by the Arcadia Formation
(undifferentiated), the Nocatee Member or the
Suwannee Limestone, it is difficult to
distinguish these units from the Tampa Member
based on gamma-ray activity. On the other
hand, where the Tampa Member is overlain by
the Arcadia Formation, the two units are usually
readily distinguishable due to higher gamma-ray
activity in the undifferentiated Arcadia
Formation.

Along the updip erosional pinchout of the
Tampa Member, where it forms an irregular
subcrop contact with the Suwannee Limestone
(Plate 49), the top of the FAS generally
coincides with the uppermost carbonate unit
occurrence (Figure 8). In the west-central part
of the study area, the Tampa Member is the
uppermost lithostratigraphic unit within the FAS
(Figure 8); however, based on lithologic and
hydrologic data from wells in south-central
Hillsborough County, the Tampa Member is
locally hydraulically separated from the
Suwannee Limestone and is therefore considered
part of the IAS/ICU (Figure 8). This latter
hydrogeologic setting occurs locally in northern
Pinellas County as well.

The depositional environment of the Tampa
Member was that of a quiet water lagoon, much
like present day Florida Bay (King, 1979). An
influx of siliciclastics nearly devoid of
phosphorite distinguishes Tampa Member
deposition from older and younger Hawthorn
Group units in the stratigraphic section.






BULLETIN NO. 68


"Venice Clay"

The Venice Clay is an informal unit
originally considered part of the lower Tamiami
Formation (Pliocene); however, microfossil data
suggest an age of Early to Middle Miocene
(Scott, 1993). Scott (1992b) suggests informal
placement of the Venice Clay in the upper half
of the Arcadia Formation based on subjacent and
suprajacent lithologies and preliminary fossil
evidence. The Venice Clay is gray-green
magnesium-rich clay, variably dolomitic with
minor amounts of quartz sand and silt. The unit
rarely contains phosphorite and becomes
increasingly silty toward its upper and lower
contacts (Campbell et al., 1993).

The subcrop extent of the Venice Clay
includes Sarasota County and adjacent parts of
Manatee, DeSoto and Charlotte Counties; the
unit may also extend offshore (Barr, 1996).
Based on data collected in the present study, the
top of the unit generally occurs between -10 ft
MSL and -100 ft MSL (-3.1 to -30.5 m). Barr
(1996) reports that thickness of the unit ranges
up to approximately 30 ft (9.1 m). Gamma-ray
activity is diagnostically very low for this unit,
(note clay beds near top of the Arcadia
Formation in W-15683 [TR 3-3]; Plate 19),
suggesting the mineral assemblage does not
include abundant potassium-rich illite-group
clays. The Venice Clay was likely deposited in
a quiet shallow water marine environment -
possibly an estuary (Tom Scott, personal
communication, 2004).

The Venice Clay acts as a confining unit in
the upper part of the IAS/ICU. Specifically,
Barr (1996) suggests that it comprises the
confining unit below "permeable zone 1."
Owing to its limited thickness and aerial extent,
as well as recent mapping by Barr (1996), the
Venice Clay is not mapped in the present study.

Peace River Formation

The Middle Miocene to Lower Pliocene
(Scott, 1988; Covington, 1993) Peace River
Formation is comprised of yellowish gray to
olive gray, interbedded sands, clays and
carbonates with the siliciclastic component


being dominant (Scott, 1988). The relative
abundance of carbonate beds generally increases
toward the south, especially near the base of the
unit. Variable amounts of phosphate sand and
gravel are interspersed throughout the unit;
however, they are most common within the
uppermost beds. The Peace River Formation
contains a diverse fossil assemblage of marine
and terrestrial fauna (e.g., shark teeth and
vertebrae, ray spines, horse teeth, dugong and
whale ribs, etc.), especially within the Bone
Valley Member (Figure 16). Porosity types in
the formation are generally intergranular, except
in the carbonate-rich zones, where moldic
porosity is also present. Only two total porosity
analyses of Peace River Formation samples have
been measured in this study. The results, 34.4
percent and 39.4 percent, should not be taken as
representative of the unit given its diverse
lithology.

Lithologic characteristics of the Peace River
Formation are generally consistent; however, the
carbonate component becomes more prevalent
from north to south as the unit thickens.
Throughout most of its extent, the Peace River
Formation does not contain shell material, with
possible exception of southeast DeSoto County,
where barnacles are present within the unit
(Green et al., 1999). These barnacle-rich
sediments may be the equivalent of "unit 11"
from Petuch (1982). Missimer (2001) reports
shell material in the Peace River Formation
south of Charlotte County. In the same region,
calcareous nannofossils occur in the unit
(Covington, 1993).

The Peace River Formation generally has an
unconformable contact with the underlying
Arcadia Formation. In an isolated area in north-
east-central Hillsborough County, the Peace
River Formation directly overlies the Tampa
Member (Plates 13 and 33). The Peace River
Formation also has an unconformable contact
with the underlying Ocala Limestone in northern
Polk County (Plates 11 and 34; W-14389
[ROMP 76]). In this area, reworked Peace River
Formation sediments may occur unconformably
above the Avon Park Formation where the Ocala






FLORIDA GEOLOGICAL SURVEY


Figure 16. Assemblage of typical Bone Valley Member fossils. Clockwise from upper left: ray
spines, shark vertebra, shark teeth, horse teeth, alligator tooth in matrix, (nickel for scale) dugong
rib, mammoth tooth and bone fragment. Background is a slab of Avon Park Formation dolostone
with Thalassodendron sp. carbonized impressions. (Photo credit: Jon Arthur, FDEP-FGS).


Limestone is locally absent (Plate 39).

Delineation of the Peace River Arcadia
Formation contact is problematic in some
localities. In many cores, the two units appear to
be conformable, with phosphate-rich
siliciclastics grading with depth to more
siliciclastic-interbedded carbonates containing
generally finer-grained and less abundant
phosphorite. Thickness of this transition zone
may exceed tens of feet. With increasing depth,
Arcadia Formation lithologies become more
dominant. In such cases, the lower contact of
the Peace River Formation is estimated based on
sedimentary structures as well as a best
approximation of where the overall lithologic
sequence becomes more carbonate dominant. In
contrast to the locally gradational contacts, other
areas provide strong evidence of an
unconformity, where a phosphatic rubble zone
occurs at the base of the Peace River Formation
(Scott, 1988).


Post-Pliocene/Miocene sediments disconformably
overlying the Peace River Formation in the
study area are comprised of fossiliferous sands,
clays and shell beds with variable amounts of
limestone and reworked phosphorite (e.g., Plate
11, W-14389 [ROMP 76] and Plate 13, W-
16576 [ROMP DV-1]). The contact of these
sediments with the Peace River Formation can
be difficult to determine because of lithologic
similarities (e.g., clays and phosphorite),
especially where the uppermost beds of the
Peace River Formation have been leached by
groundwater, giving the sediments an
appearance similar to that of some post-
Hawthorn Group lithologies. In addition, it can
be very difficult to distinguish Peace River
Formation sediments from those of reworked
Peace River sediments (e.g., post-Hawthorn
Group undifferentiated sands and clays) when
studying cores (the distinction is extremely
difficult to impossible when evaluating
cuttings).






BULLETIN NO. 68


Similar to basal Peace River Formation lag
deposits, reworked Miocene-Pliocene sediments
may also yield a phosphate lag deposit at the
base of overlying (e.g., post-Hawthorn Group)
sediments. Units superjacent to the Peace River
Formation include the Tamiami, Ft. Thompson
and Caloosahatchee Formations. In most cases,
the Peace River Formation is readily
distinguished from these overlying
sand/shell/carbonate lithofacies.

Lateral facies transitions of the Peace River
Formation are most evident along the
northwestern extent of the unit in Hillsborough
and Polk Counties (Plate 51). In this area,
sediments characteristic of the Peace River
Formation grade into clay-rich and phosphate-
poor sediments of the undifferentiated Hawthorn
Group (e.g., Plate 13).

Maximum elevations of the Peace River
Formation occur in the vicinity of the Polk
Upland and Lakeland Ridge, where the unit
exceeds 125 ft (38.1 m) MSL (Plate 51). The
maximum observed depth of the Peace River
Formation exceeds -200 ft (-60.9 m) MSL along
the Lake Wales Ridge. Thicknesses range to
over 120 ft (36.6 m) along the southeastern third
of the unit's mapped extent (Plate 52).

Gamma-ray activity in the Peace River
Formation is highly variable. In some areas, due
to the high-phosphorite content in the sediments,
strong gamma-ray peaks are readily observed in
contrast to lower gamma-ray activity of the
Arcadia Formation (e.g., W-16576 [ROMP DV-
1], Plate 33). The opposite occurs as well,
where gamma-ray activity in the Peace River
Formation is lower than that of the Arcadia
Formation (Figure 10). Where the Peace River
Formation lies above Eocene carbonates, the
difference is also pronounced, with the younger
unit exhibiting a stronger gamma-ray signal
(Plate 20). In many wells, a lack of gamma-ray
contrast between the Peace River Formation and
the Arcadia Formation is observed (W-16740
[ROMP 39], Plate 33). In wells where the base
of Peace River Formation contains a reworked
phosphate lag deposit, a characteristically strong
gamma-ray peak is observed (e.g., W-15938,


Plate 22). The unit may also be overlain by a
similar lag deposit within undifferentiated post-
Hawthorn Group sediments.

The Peace River Formation is a regional
confining to semi-confining lithostratigraphic
unit within the upper part of the IAS/ICU.
North of central Hillsborough and Polk
Counties, the Peace River Formation and
undifferentiated Hawthorn Group sediments
comprise a low-permeability confining to semi-
confining facies of the IAS/ICU. South of this
region, permeable, water-producing zones exist
within interlayered carbonate lenses (e.g., Ryder,
1985, Torres et al., 2001). In some areas, the
uppermost sediments of the Peace River
Formation are in hydraulic connection with
overlying sands due to a low-to-absent clay
content (e.g., Plate 17, W-14382 [ROMP 23]).
As a result, the Peace River Formation may
comprise the lower part of the SAS. Clay-poor
sediments occur within the uppermost Peace
River Formation in eastern Sarasota County and
western Manatee County (Tom Scott, personal
communication, 2006).

The Middle Miocene Lower Pliocene Peace
River Formation sediments characterize a
complex depositional environment strongly
influenced by sea-level fluctuations (Missimer et
al., 1994). The northern extent of the unit was
deposited in a shallow marine, deltaic to
brackish water environment while further south
open marine conditions prevailed (Scott, 1988).
Carbonate deposition in the unit was
periodically restricted by a flood of siliciclastics
from the north and a rise in sea level (Scott,
1988). Missimer (2001) suggests that the Peace
River Formation immediately south of the study
area was deposited in a variety of depositional
environments ranging from inner ramp to deltaic
to beach and can be explained by shoaling
upward or lateral accretion of sediment. Sea-
level transgressions or highstands appear to
favor phosphogenesis, while reworking of the
sediments during sea-level regressions or
lowstands concentrate the phosphorite (Compton
et al., 1993). Phosphorite concentrations are
considered economic ore deposits in the central
region and are locally mined.






FLORIDA GEOLOGICAL SURVEY


Bone Valley Member

The Middle Miocene to Lower Pliocene
(Webb and Crissinger, 1983) Bone Valley
Member of the Peace River Formation has a
limited areal extent, centered in southwestern
Polk County (Plate 53). It occurs in the Central
Florida Phosphate District which is among the
world's largest economic phosphorite deposits
(Freas and Riggs, 1968). Due to mining, most
of the Bone Valley Member sediments have
been removed. Although similar in lithology to
the Peace River Formation, the Bone Valley
Member contains greater amounts of
phosphorite (more than 30 percent by volume)
that is coarser-grained, ranging up to gravel-size
nodules. Phosphorite occurs as carbonate-
fluorapatite (francolite) nodules, peloids, fecal
pellets, intraclasts and grain coatings. Some
pebble-sized grains show evidence of reworking,
boring structures and multiple stages of
phosphatization. The non-phosphorite
component of the Bone Valley Member is
comprised of quartz sand with clay (e.g.,
palygorskite and sepiolite; Scott, 1988)
generally exceeding 20 percent by volume.
Carbonate beds are not present; however
limestone and dolostone cobbles and larger
fragments are observed (Tom Scott, personal
communication, 2005).

An extremely diverse fossil assemblage
exists within the unit (Webb and Crissinger,
1983) ranging from dugong and whale ribs,
shark teeth and turtle scutes to petrified wood
and teeth from horses and alligators (Figure 16).
Thicknesses of the Bone Valley Member exceed
40 ft (15.2 m) (Plate 54). In terms of hydrologic
function, the unit is a localized, yet efficient
confining unit within the IAS/ICU. On the other
hand, due to the significant economic value of
phosphorite deposits, the unit has been
extensively mined thereby reducing or
eliminating local confinement.

Owing to the high phosphorite content,
gamma-ray log intensities for Bone Valley
Member sediments are very high. For example,
the truncated, high-intensity gamma-ray peak at
the top of the Peace River Formation for W-


14385 (ROMP 45; Plate 22) represents Bone
Valley Member sediments.

Many questions exist regarding the genesis
of phosphate in Florida. Given the diverse fossil
assemblage, it reflects near-shore marine
conditions and is unlike other large phosphate
deposits of the world. Parts of the Bone Valley
Member were deposited in a high-energy
nearshore environment (topographic highs)
while other parts were deposited in a shallow
marine environment such as an embayment or
lagoon (Scott, 1988). The stratigraphy of the
unit is complicated by rapid facies changes and
post-depositional erosion, redeposition and
weathering (Freas and Riggs, 1968; Webb and
Crissenger, 1983).

Hawthorn Group (Undifferentiated)

Undifferentiated Hawthorn Group sediments
lie unconformably above Eocene and Oligocene
carbonates and unconformably below
undifferentiated Pliocene and younger sands and
clays along the upland geomorphic provinces
within the northern region, as well as in parts of
Pinellas, Hillsborough and Polk Counties. In
Marion, Sumter and Lake Counties, sediments
mapped as undifferentiated Hawthorn Group
may be comprised of one or more of the
following lithostratigraphic units (from oldest to
youngest): the Penney Farms Formation, the
Marks Head Formation and the Coosawhatchie
Formation (Scott, 1988). These formations are
not delineated owing to their limited extent and
stratigraphic pinch-out along the northeastern
part of the study area. Moreover, Scott (1988)
reported on the difficulty of distinguishing the
uppermost Coosawhatchie Formation from
undifferentiated Hawthorn Group sediments in
central Florida. In the north-central part of the
study area, undifferentiated Hawthorn Group
sediments occur along the Brooksville Ridge
(e.g., W-6903, Plate 5 and W-15933, Plate 9) as
well as within karst features and isolated lenses
flanking the ridge. Vernon (1951) describes
"Miocene Hawthorn formation" sediments along
the Brooksville Ridge in Citrus County as
greenish-gray montmorillonitic clays. The
distribution of these sediments, as well as the






BULLETIN NO. 68


occurrence of hard-rock phosphate in the region
lend support to the proposal by Scott (1988) that
Hawthorn Group sediments once covered the
entire Florida peninsula. Upchurch (1992) also
suggests that Hawthorn sedimentation occurred
on the crest of the Ocala Platform.

Undifferentiated Hawthorn Group sediments
are generally comprised of clay beds with
variable amounts of carbonate, quartz sand and
silt, phosphorite, organic material and minor
shell fragments. Maximum elevations of
undifferentiated Hawthorn Group sediments
exceed 100 ft (30.5 m) MSL along inland
uplands and ridges north of Pasco County. In
Pinellas County, these sediments generally occur
deeper than -25 ft (-7.6 m) MSL.
Undifferentiated Hawthorn Group sediments
occurring in Hillsborough, Pinellas and Pasco
Counties grade laterally southeastward into the
Peace River Formation. In central Pinellas
County undifferentiated Hawthorn Group
sediments exceed 100 ft (30.5 m) thick and
grade southward into the Arcadia Formation
(Plate 31).

Gamma-ray response of the undifferentiated
Hawthorn Group sediments varies from low-
background counts where the unit is dominated
by clays, to broad and diffused patterns where
phosphorite is more abundant. Gamma-ray logs
are generally not very useful as a tool to
determine the contact with underlying and
overlying units.

In the northern region, undifferentiated
siliciclastic sediments of the Hawthorn Group
comprise discontinuous semi-confinement
between the SAS and FAS. The lateral extent
and effectiveness of this lower-permeability
layer is difficult to define due to factors such as:
1) variable lithology (e.g., percent clay) and
thickness, 2) desiccation cracking of thin clay-
rich beds during long-term low-water table
conditions and 3) breaches due to fractures and
sinkholes. As a result, many areas in this region
are denoted on Plate 55 as "discontinuous basal
confinement of SAS." These same areas are
likewise labeled "discontinuous" on Plates 56 and 57.


Pliocene and younger Series

Post-Hawthorn Group Sediments

Sediments overlying Hawthorn Group and
older units in the study area are generally
comprised of varying percentages of
undifferentiated sand, shell and clay. Within the
eastern half of the study area, the Cypresshead
Formation dominates most uplands (Figure 2)
and is well exposed along the Lake Wales
Ridge. In the southern region, three Pliocene-
Pleistocene formations are recognized: the
Tamiami Formation, the Caloosahatchee
Formation and the Fort Thompson Formation.
The latter two formations are faunally rather
than lithologically based. As a result, Scott
(1992c) provides a conceptual framework to
include Caloosahatchee and Fort Thompson
sediments as part of the Okeechobee formation
(informal). The framework also includes
informal "Bermont formation" sediments.

Although mapping post-Hawthorn Group
sediments is beyond the scope of this study,
general descriptions of the units are provided
herein. These undifferentiated surficial
sediments and formations generally comprise
the SAS. In the southern region, the lower
Tamiami Formation is considered part of the
IAS/ICU. In the cross sections (Plates 4-37),
undifferentiated sediments are broadly
classified as sand and clay (UDSC) or sand
and shell (UDSS). Existing lithologic
descriptions may identify "Pliocene -
Pleistocene" sediments (often referred to as
"PCPC"); however in the present study, these
sediments are labeled "UDSC" due to
difficulty in distinguishing the two
undifferentiated types as well as inconsistent
usage of PCPC. Gamma-ray activity in post-
Hawthorn Group sediments is highly variable
(Plates 4-37; Davis et al., 2001). In some
areas, however, a consistent peak at the base
of these sediments represents a phosphate lag
deposit reworked from Hawthorn Group
sediments (Scott, 1988; Green et al., 1995;
see also W-16303 [TR 7-4] and W-17057
[TR 7-2], Plate 16).






FLORIDA GEOLOGICAL SURVEY


Tamiami Formation

Lithology of the Lower- to mid Pliocene
(Missimer, 2002) Tamiami Formation
(Mansfield, 1939) is difficult to characterize due
to the large number of sediment facies it
contains. These facies occur over a large region
of southern Florida and represent a complex set
of depositional environments (Berndt et al.,
1998). The Tamiami Formation consists of a
wide range of mixed carbonate/siliciclastics
(sandy limestone, sand and clay with varying
percentages of phosphate grains) and shell beds
that are subdivided as members (e.g., Ochopee
Limestone Member) south of the study area
(Missimer, 1993). The Tamiami Formation is
unconformably overlain by the Caloosahatchee
Formation and overlies the Peace River
Formation either conformably or
unconformably.

Where present in the study area, the Tamiami
Formation is part of the IAS/ICU and SAS
(Bemdt et al., 1998). A semi-regionally
extensive clay layer within the Tamiami
Formation comprises the top of the IAS/ICU,
whereas the uppermost higher permeability
sediments are hydraulically connected with the
SAS.

Sands and finer-grained facies probably
represent deposition in a regressing Tamiami sea
in the brackish water of a lagoon or bay (DuBar,
1962). Deposition of the shell beds are most
likely the result of storms and processes
occurring in shallow coastal waters (Missimer,
2001). Phosphatic quartz sand facies containing
giant barnacles and echinoids exposed along
Alligator Creek and in pits near Acline
(Charlotte County) are thought to represent
deposition in a shallow water, nearshore
environment (DuBar, 1962).

Cypresshead Formation

The Upper Pliocene Cypresshead Formation
(Huddlestun, 1988) is composed entirely of
siliciclastics, predominantly quartz and clay
minerals (Scott, 1992b; Berndt et al., 1998). It
consists of characteristically mottled reddish


brown to reddish orange, unconsolidated to
poorly consolidated, fine to very coarse grained,
clean to clayey sands (Scott, 2001), some of
which are cross bedded. Discoid quartz pebbles
and mica are also often present. Clay beds are
generally thin and discontinuous. Overall, the
clay content varies from trace amounts to more
than 50 percent, averaging 10-20 percent (Scott,
1992b). Due to weathering, the clays are often
altered to kaolinite. Davis et al. (2001) describe
three lithozones within the unit, which are based
on color, sedimentary structures and varying
proportions of siliciclastics. Original fossil
material is not present in the sediment but poorly
preserved casts and molds of mollusks and
burrow structures are occasionally present
(Scott, 2001).

The Cypresshead Formation occurs in the
central uplands of the Florida peninsula south
into Highlands County (Arthur, 1993; Scott et
al., 2001). Exposure of the formation generally
occurs above 100 ft. (30.4 m) MSL (Scott,
1992b, 2001). In the northern half of the study
area, the unit lies unconformably on Eocene
carbonates, whereas in the southern half it
unconformably overlies Hawthorn Group
sediments. The Cypresshead Formation can be
readily distinguished from the Hawthorn Group
because the younger unit is non-phosphatic,
contains prominent horizontal bedding and cross
bedding, is largely nonfossiliferous and contains
burrow and bioturbation structures (Huddlestun,
1988). Along the Lake Wales Ridge, the SAS is
comprised of sediments from the Cypresshead
Formation and undifferentiated sediments (Scott,
1992b). Huddlestun (1988) suggests that the
depositional environment was coastal marine
(see also discussion of Figure 7 on p. 15).

Caloosahatchee Formation

The Caloosahatchee Formation was first
recognized by Heilprin (1887) as a Pliocene
formation he called the "Floridan Beds." Dall
(1887) also considered the deposits Pliocene and
described many of the fossils; he referred to
them as the Caloosahatchee Beds or Marls.
Scott (1992c) includes sediments informally
referred to as the Bermont formation within the






BULLETIN NO. 68


Caloosahatchee Formation and reports a Late
Pliocene to Early Pleistocene age. The
Caloosahatchee Formation consists of marls
composed primarily of quartz sand, silt and
shells with varying amounts of carbonate in the
matrix. It varies from poorly indurated to well
indurated and the fauna is varied and often well
preserved. Usually moderately to abundantly
fossiliferous, some sands are almost or
completely barren of fossils (DuBar, 1958).
Freshwater limestones are commonly present.

The extent of the Caloosahatchee Formation
is shown on previous geologic maps by Cooke
(1945) and Vernon and Puri (1964). The contact
between the subjacent Tamiami Formation and
the Caloosahatchee Formation is generally
unconformable. The Tamiami Formation was
subjected to significant subaerial erosion and the
deposition of the Caloosahatchee Formation
gradually filled in old "Tamiami valleys"
(DuBar, 1958). The Caloosahatchee Formation
comprises part of the SAS. In most
hydrogeological investigations, the
Caloosahatchee Formation is not differentiated
from the Fort Thompson Formation (Scott,
1992a). The depositional environment was
subtropical with predominantly carbonate
deposition and a coastal influx of quartz sand.
Tropical and subtropical mollusks and corals
abundant in the unit reflect an environment
similar to the present area between Cape Sable
and Florida Bay (Missimer, 2001).


Fort Thompson Formation

Sellards (1919) proposed the name Fort
Thompson Beds, which were informally
designated a formation by Cooke and Mossom
(1929). DuBar (1958) recognized the unit as
upper Pleistocene. The Fort Thompson
Formation is a sandy limestone deposited under
freshwater and marine conditions. The sand is
fine to medium grained and is interlayered with
shell beds and limestones. The shell beds are
slightly indurated to unconsolidated and variably
sandy (Scott, 1992b; Berndt et al., 1998). A
characteristic Fort Thompson marine fossil is
Chione elevata and Helisoma scalare (Figure
17) is typical of freshwater beds in the unit
(DuBar, 1958).

The Fort Thompson Formation is thin, does
not exceed 30 ft (9.1 m) in thickness, and has an
unconformable relationship to the variable units
above and below. It is most commonly
underlain by the Caloosahatchee Formation or
the Tamiami Formation (DuBar, 1958). The
Fort Thompson Formation is part of the
undifferentiated sediments in southern Florida
(Scott, 1992b) and comprises part of the SAS.
The extent of the Fort Thompson Formation is
shown on geologic maps by Cooke (1945) and
Vernon and Puri (1964). On the most recently
published geologic map of Florida (Scott et al.,
2001), the Ft. Thompson and Caloosahatchee
Formations are mapped as undifferentiated
Tertiary Quaternary shell-bearing sands
(TQsu; Figure 2).


Figure 17. Characteristic Ft. Thompson Formation fossils Chione elevata (left) and Helisoma
scalare (right; photos courtesy of IP/FMNH); bar = 12 mm.






FLORIDA GEOLOGICAL SURVEY


Hydrostratigraphy

Introduction

The hydrostratigraphic setting of the study
area varies from a locally exposed single aquifer
system in the north, to three aquifer systems in
the central and southern parts of the study area.
In the northern region, the FAS ranges from
variably confined to unconfined; clayey
sediments of the IAS/ICU or basal SAS are
locally present; IAS/ICU confining sediments
are present especially within the uplands and
ridges. The SAS, where present, is intersected
by numerous karst features (Trommer, 1987; see
also Plate 3) which may act as direct hydraulic
connection between the SAS and the FAS.
Increased permeability of the IAS/ICU occurs
where the Hawthorn Group sediments thicken
southward from central Hillsborough and Polk
Counties. In the central and southern regions,
the IAS/ICU collectively forms a thick confining
unit with intervening permeable zones that
separate the FAS from the SAS. As noted
earlier, the nomenclature applied herein is based
on aquifer system nomenclature as modified
from Florida Geological Survey Special
Publication 28 (see Hydrogeology, p. 17;
Appendix 2).

Hydrogeological properties

Numerous studies provide details on
hydrogeologic properties of aquifer systems in
the study area. For detailed information on
aquifer transmissivity, storativity, leakance
coefficients, etc., the reader is referred to USGS
publications (e.g., Ryder, 1985; Wolansky and
Corral, 1985; Metz, 1995; Yobbi, 1996;
Knochenmus, 2006), numerous SWFWMD
ROMP technical reports (e.g., Clayton, 1994,
1999; Gates, 2001; LaRoche, 2004); SWFWMD
hydrogeological studies (e.g., Barcelo and
Basso, 1993; Hancock and Basso, 1993; Basso,
2002, 2003) and especially the Southwest Florida
Water Management District (2006b) compilation:
"Aquifer Characteristics within the Southwest Florida
Water Management District, July 2005."

To provide a general characterization of these


hydrogeologic parameters, two datasets are
statistically and graphically summarized in the
discussion of each aquifer system: 1) data in
Southwest Florida Water Management District
(2006b) that meet certain quality
assurance/quality control (QA/QC) standards6
and 2) results of more than 200 hydraulic
conductivity and total porosity analyses
measured at the FDEP-FGS on cores from
within the study area. Both datasets are
presented to represent laboratory and field-scale
conditions. The Southwest Florida Water
Management District (2006b) compilation
represents properties measured during aquifer
pumping and performance tests, while the
FDEP-FGS dataset represents matrix
permeability (vertical) and porosity of core
samples. In Florida's dual-porosity (e.g,
intergranular and conduit flow) heterogeneous
carbonate terrain, it is widely recognized that
permeability calculated from field-scale aquifer-
test data (e.g., Basso, 2002) may differ by orders
of magnitude from that of laboratory
measurements. These data summaries are
presented herein to characterize expected ranges
of these parameters for use in hydrologic models
and to provide a frame of reference for those
collecting hydrological data in the field or lab.
For further details on matrix permeability, as
well as discussion of its significance and
limitations, the reader is referred to Budd (2001,
2002) and Budd and Vacher (2004).

In the descriptive statistics for each aquifer
system, standard parameters are summarized,
including mean, median, range, quartile values,
and number of analyses. Also included are
distribution descriptors: skewness, kurtosis and


6 QA/QC screening guidelines: 1) used data with
"acceptable" and "good" test-reliability scores as
defined and assigned in Southwest Florida Water
Management District (2006b); 2) avoided aquifer
tests where partial penetration was noted and no
corrections applied; 3) avoided tests where aquifer
penetration thicknesses were inconsistent with casing
and total depth data; 4) avoided use of well pairs in
which the observation well open interval differed
from the open interval in the test well by more than
15 percent; 5) avoided short-duration tests; and 6)
evaluated comments with respect to quality of test
data.






BULLETIN NO. 68


the Anderson-Darling test for normality. In the
Anderson-Darling test, the A2 value is the test
statistic for normality; if the probability (P-
value) is greater than 0.05, the data are normally
distributed. Graphical summaries of the
hydrogeological data include histograms, box
plots and 95 percent confidence interval range
charts. The histograms include a log-normal
curve fit for all parameters except for the
porosity data and SAS vertical hydraulic
conductivity. The vertical (y) axis on the
histograms reflects the total number of analyses
(N), which are listed in each statistical summary.
Units for each parameter are listed in the figure
header. The horizontal (x) axis of the box plots
corresponds to the histogram x-axis. Asterisks
in the box plots denote statistical outliers.

Surficial aquifer system

The surficial aquifer system (SAS) is
predominately comprised of Late Pliocene to
Holocene sediments and is contiguous with land
surface. This hydrostratigraphic unit occurs
throughout the study area, with the exception of
two hydrogeologic settings: 1) where an
unobstructed vertical hydraulic connection exists
between surficial sediments and the FAS (e.g.,
unconfined FAS) and 2) where the very low-
permeability sediments of the Hawthorn Group
(e.g., Peace River Formation) locally occur at or
near land surface (e.g., SAS absent and FAS is
confined). This latter setting occurs in the
central and southern Polk Upland physiographic
province (Figure 6). The extents of either of
these settings are too localized or disturbed by
mining to delineate accurately within the scale
and scope of this project. The SAS generally
consists of unconsolidated quartz sand with
variable amounts of shell, clay, phosphate and
organic material. Shell content in the SAS
increases significantly toward the southern part
of the study area (Vacher et al., 1993; see also
"UDSS" comprising the SAS in the
southernmost cross sections [e.g., Plates 18,
19]). Excluding the ridges, thickness of the SAS
averages -30 ft (-9 m). Along the Lake Wales
Ridge in the southeastern part of the study area,
SAS thicknesses range to more than 300 ft (99.4
m) (Plates 26 and 55). In the southern region,
the areas with relatively thick SAS generally


correspond to localities where the permeable
upper Tamiami Formation sediments are
included within the SAS.

The SAS is delineated in areas where
laterally extensive, sufficiently confining clayey
sediments of the IAS/ICU occur beneath
unconsolidated surficial sediments. In parts of
the northern region, the SAS locally may
directly overly the FAS. Iron-cemented zones
("hardpan") and intermittent basal clays may
result in a "perched" water table or local SAS-
like unit. On the other hand, basal confinement
breached by sinkholes or fractures precludes
characterizing much of the northern region as a
laterally extensive and functional SAS due to
lack of regional hydraulic continuity. In this
hydrogeologic setting, delineation of the SAS
becomes subjective. To account for such areas,
a hachured pattern is included on Plate 55 to
reflect "discontinuous basal confinement of the
SAS." It is noteworthy that this subjective
delineation could also be applied to the northern,
significantly karstified part of the Brooksville
Ridge; however, in recognition of available data
and to maintain consistency with the IAS/ICU,
the SAS is delineated in this area.

Groundwater w ithdrawals from the SAS are
minimal compared to that of the IAS/ICU or
FAS. Based on data from Marella (2004), the
SAS yielded between 1 percent and 5 percent of
total groundwater withdia\\als in Charlotte,
Citrus, Levy, Marion, and Sumter Counties
during 2000. In Lee County, the SAS comprised
more than 55 percent of total w ithdia\\al
(Marella, 2004). Each of the remaining counties
in the study area withdrew less than 1 percent
groundwater from the SAS (Marella, 2004).

Throughout the study area, the local water
table mimics topography (Sepulveda, 2002;
Arthur et al., in review). Elevation of the water
table varies widely throughout the study area,
ranging to more than 175 ft (53.3 m) MSL
(Arthur et al., in review). Along much of the
Lake Wales Ridge, such as in the Intraridge
Valley (Figure 6) the water table is often less
than 10 ft (3.0 m) below land surface. The water
table in other parts of the Lake Wales Ridge, as
well as other upland areas, can exceed 50 ft
(15.2 m) below land surface. Movement of SAS






FLORIDA GEOLOGICAL SURVEY


groundwater is dynamic, due to complex
interactions between recharge, discharge
(including pumping and mining operations),
runoff, infiltration, evapotranspiration and
seepage to and from underlying aquifers
(Lewelling et al., 1998). Evidence from paired
monitor wells confirms local semi-permeable
hydrologic connection between the SAS and
FAS in parts of the Lake Wales Ridge due in
part to interaquifer connectivity through sinks or
paleosinks (Tihansky et al., 1996). Depending
on hydraulic conditions, karst density, and the
leakance of basal SAS clays (or IAS/ICU clays),
the SAS may locally recharge the FAS in parts
of the northern study area. Local pumping,
rainfall events, seasonal and climatic variations
add to the complex dynamics of this
relationship.

Surface-water/groundwater interactions are
evident throughout the study area, such as
coastal springs and base flow in rivers and
streams. An outstanding example of these
dynamic interactions occurs within the Peace
River basin. Along the upper part of the basin,
maximum river-flow losses exceed 11 million
gallons per day (4.2x107 liters per day), locally
recharging underlying aquifers due to a
downward head gradient, riverbed sinkholes and
inferred buried subsidence structures (Lewelling
et al., 1998). Further downstream in the lower
part of the basin, the river receives intergranular
(rather than karst-related) seepage from the SAS
and possibly the IAS/ICU (Lewelling et al.,
1998). Understanding such surface-
water/groundwater interactions is essential
toward the establishment of effective minimum
flows and levels (MFL) and total maximum
daily loads (TMDL). Some karst-related
features, however, do not affect these
interactions. For example, the closed
topographic depressions in eastern Sarasota
County (Plate 3) are likely "sags" formed due to
the dissolution of carbonate shell material (Sam
Upchurch, personal communication, 2004).
These sags likely do not function as preferential
recharge pathl an s from the SAS to underlying
aquifer systems.
Correlation of the SAS with lithostratigraphic
units in the study area generally places the
system within post-Hawthorn Group sediments.
In the northern region, these Pliocene and


younger sands and clays are undifferentiated
(UDSC). Along the eastern region, the
sediments correlate with the Cypresshead
Formation. Further south, the Ft. Thompson,
Caloosahatchee and Tamiami Formations
comprise most of the SAS. Basal SAS clays
may represent low-permeability undifferentiated
Hawthorn Group sediments, or re-worked
Hawthorn Group sediments in the northern and
central region. In the central and eastern
regions, the base of the SAS generally coincides
with the top of the Peace River Formation
(Hawthorn Group); however, relatively clean
sands of the Peace River Formation comprise
part of the SAS in localized areas (e.g., W-
14382 [ROMP 23], Plate 17). In the southern
region, the base of the SAS not only overlies the
Peace River Formation, but also the fine-grained
dolostones of the Arcadia Formation (parts of
western/coastal Manatee and Sarasota Counties)
and middle-Tamiami clays (e.g., southeastern
Charlotte and Lee Counties; Reese, 2000;
Weinberg and Cowart, 2001). Note however,
that Missimer and Martin (2001) report two
aquifers within the SAS in Lee County, the
lowermost being the "Lower Tamiami Aquifer;"
whereas researchers such as Knochenmus and
Bowman (1998) and Torres et al. (2001) place
the entire Tamiami Formation within the
IAS/ICU. The relation between the Tamiami
Formation and hydrostratigraphic units from Lee
County north to Sarasota County warrants
further investigation.

Vadose-zone hydrogeologic characteristics of
the SAS can be approximately inferred from a
comparison of environmental geology and soil
permeability maps (Figures 4 and 18,
respectively). Patterns in both of these maps
roughly correlate with major geomorphic
provinces (Figure 6). The most permeable soils
and shallow sand-dominated sediments or
carbonate lithologies are located in the Coastal
Swamps, Gulf Coastal Lowlands, the Lake
Wales Ridge, whereas some of the least
permeable soils occur along the southern extent
of the Brooksville Ridge and parts of the
Western Valley.

In the northern region, surficial deposits may
be missing, having been eroded away and
exposing limestone at the surface (e.g.,






BULLETIN NO. 68


unconfined FAS; see Plates 29 and 30). In
contrast, these same deposits may locally exceed
100 ft (30.5 m) thick where they infill karst
features (including paleo-sinks represented by
W-15075 and W-10829; Plates 5, 6 and 29).
Depending on the permeability of infilling
sediments, the karst features may provide
hydraulic connection between the SAS and the
FAS.

Topographic inversion (i.e., differential
carbonate dissolution due to chemical buffering
and confinement) also contributes to the highly
variable thickness of the SAS in the northern
region. Along the axis of the Brooksville Ridge,
for example, more than 50 ft (15.2 m) of SAS is
locally observed. Much of the Ridge, however,
is perforated by sinkholes (Plate 3), making
delineation of the SAS problematic. Although
lithologic data from wells support presence of
the SAS along the Brooksville Ridge, extent of
the unit is even more subjective in the
surrounding region. Assessment of regional
mapping (geology [Figure 2], environmental
geology [Figure 4], and soil permeability [Figure
18]) warrants the dashed (i.e., approximate)
extent of the SAS in the region (Plate 55).
These hachured areas are considered semi-
confined to unconfined FAS.

In addition to lithologic evidence, hydraulic
data support local delineation of the SAS in
parts of the northern region. Well W-15647
(ROMP 90; Plate 10) provides a classic example
of confinement between the SAS and the FAS in
this region. Water levels measured during
drilling rose 3 ft (0.9 m) when the clays
underlying the SAS were fully penetrated and
artesian conditions of the FAS became evident.
The IAS/ICU in this well is too thin to depict
graphically in Plate 10. Moreover, given the
proximity of the well to the IAS/ICU extent,
whether the clays are basal SAS or IAS/ICU is
subjective. Confined and semi-confined areas of
Citrus County have been identified (Lee, 1998).

Water levels in paired monitor wells also
provide valuable information regarding the
presence of the SAS (i.e., basal confinement) in


the absence of an extensive IAS/ICU. This data,
however, should be interpreted with caution:
similar water levels may reflect "leaky"
confinement and seasonal or local pumping
conditions should be considered. The "Floridan"
water levels in W-14336 (ROMP 93, Plate 10),
are at least 5 ft (1.5 m) lower than SAS water
levels (U.S. Geological Survey, 1990) indicating
a well-defined hydraulic separation between the
two aquifer systems. Hydrologic data from W-
16644 (ROMP LP-6), located approximately 2
mi (3.2 km) north of cross section D-D' (Plate 7)
indicates that FAS water levels are typically
more than one foot (0.3 m) above the surficial
water table. At W-16644, 12 ft (3.7 m) of clay
and clayey sand provide sufficient confinement
between the FAS and SAS.

As noted above, effectiveness of the
hydraulic separation between the SAS and the
subjacent FAS varies locally. Water levels in
the paired wells L11KD and L11KS (northeast
of W-5054, Plate 2), are nearly
indistinguishable, thus indicating leaky to
unconfined conditions between the FAS and
"water table" levels in surficial sediments (U.S.
Geological Survey, 1998). In contrast, water
levels from the monitor-well pair L11MM and
L11MS (southeast of W-5054, Plate 2) confirm
existence of SAS conditions because "water-
table" elevations differ from the FAS
potentiometric surface (U.S. Geological Survey,
1998). Paired monitor wells with inconsistent
trends in water levels suggest that there may be
some degree of confinement of the FAS, either
as low permeability horizons in the base of the
SAS or in the uppermost carbonates of the FAS
(e.g., mudstones/micrites or densely
recrystallized zones).

A SWFWMD Technical Memorandum
(Basso, 2004) provides detail on the
hydrogeologic setting of the Herando-Pasco
County (or "Northern Tampa Bay") region. In
the memorandum, the location of wetlands, soil
properties, lithologic data and hydrographs from
nested wells and lakes are used to delineate three
zones: unconfined UFA, locally perched water
table (generally restricted to the southern






FLORIDA GEOLOGICAL SURVEY


7W7
hUc.


Mexico 1. -f














II'
Gulf
0of






















Explanation
T _Ld, 4re3
- -- VV3l-r Mana,.-n-i-nl Dislri.:l;
Soil Permeability
S20 0 n/hr
100 n/hr
0 1 in/hr


Soil Permeability



S '1- Ir I l -, ",.=
PrOleichr, C l-lr.:.nm FDEP -I1.Er.
L


E'00
J Ai
**
i


C,'


Figure 18. Soil permeability of study area (Arthur et al., in review); (data compiled on per county
basis from U.S. Department of Agriculture, Natural Resource Conservation Service, 2002 and the
Florida Geographic Data Library [www.fgdl.org]).


~ "






BULLETIN NO. 68


Brooksville Ridge) and semi-confined UFA.
This localized study provides a refinement of
confining conditions within the northern Tampa
Bay region. Although differences in
nomenclature and scale of study exist, the areas
delineated by Basso (2004) are broadly
consistent with regional representations of the
SAS in Plate 55. Basso suggests, however, that
the locally perched water table aquifer (SAS in
this report) along the southern part of the
Brooksville Ridge terminates northward near the
Hemando-Citrus County boundary. This
conclusion is consistent with an increase in soil
permeability and a relative abundance of closed
topographic depressions within the Brooksville
Ridge in Citrus County (Figure 18 and Plate 3).
Moreover, the potentiometric surface for paired
SWFWMD monitor wells in southern Citrus
County ("Lecanto 1" [deep] and "Lecanto 2"
[shallow]), which have been measured since
1965, track almost perfectly indicating
unconfined FAS. On the other hand, lithologic
data from wells in the Brooksville Ridge, Citrus
County, documents more than 30 ft (9.1 m) of
local confinement. These observations serve as
additional examples of the complex and variable
degrees of confinement in the northern region
and underscore the subjective nature of the SAS
extents shown in Plate 55.

The SAS occurs throughout most of the
central and southern regions, except where
IAS/ICU sediments crop out (e.g., central Polk
County). Several paired monitor wells
document the SAS, for example, discrete
monitor wells constructed in both the SAS and
the FAS at W-12943 (Plates 12 and 31) reveal
head differences between the two aquifer
systems (Coffin and Fletcher, 1992). Other
complementary pairs of monitor wells in the
northern Pinellas and Hillsborough Counties
support the presence of a "water table" that is
distinguishable from FAS potentiometric levels,
suggesting that some degree of laterally
extensive confinement exists between the two
aquifer systems. In the southern region, the SAS
is isolated from the FAS by thick intervening
permeable and less permeable siliciclastics and
carbonates of the IAS/ICU. High-density karst
areas (Plate 3) such as the Lake Wales Ridge increase
the potential for inter-aquifer communication
between the SAS and subjacent aquifers.


Hydraulic properties for the SAS vary widely,
owing to its heterogeneous composition and
thickness. Selected hydrogeologic data from
SWFWMD (2006b; see also p. 52) and Florida
Geological Survey laboratory data are
summarized in Figures 19-22. Surficial aquifer
system parameters include transmissivity,
specific yield and horizontal and vertical
hydraulic conductivity, respectively. Note that
the horizontal hydraulic conductivity (Kh) is
calculated from the unsaturated aquifer thickness
and the transmissivity. In the vertical hydraulic
conductivity (Kv) data, if outliers are excluded,
the range in Kv is similar to that reported by
Vacher et al. (1993). A difference of several
orders of magnitude exists between Kv and Kh
values. One factor influencing this difference
pertains to sampling bias, where many Kv
samples were selected to characterize the degree
of basal confinement of the SAS. Arguably,
some of these sediments may represent the semi-
confining facies of the IAS/ICU.

Intermediate aquifer system/
intermediate confining unit

The IAS/ICU occurs throughout much of
Florida (Scott, 1992a) and is comprised of all
rocks "that lie between and collectively
retard the exchange of water" between the
SAS and the FAS (Southeastern Geological
Society, 1986). In general, this aquifer
system correlates with Oligocene-Pliocene
clays, sands and carbonates of the Hawthorn
Group, and Pliocene clays, sands, limestone
and shell beds of the Tamiami Formation
(e.g., Berndt et al., 1998; Arthur et al., 2001a;
Torres et al., 2001; Ward et al., 2003). In the
study area, the IAS/ICU is broadly characterized
by three hydrogeologic settings: 1) relatively thin,
laterally discontinuous low-permeability
confining to semi-confining sediments that
provide local hydraulic separation between the
SAS and the FAS hachuredd area in Plates 56 and
57), 2) low-permeability confining to semi-
confining sediments hydraulically separating the
SAS from the FAS (non-hachured areas in the
northern region, Plate 56 and 57), and 3)
interlayered sequences of permeable and less-
permeable rocks and sediments separating the
SAS from the FAS (central and southern regions;
Figure 23 and Plates 56-57).








FLORIDA GEOLOGICAL SURVEY


Figure 19. Statistical summary of SAS transmissivity data from Southwest Florida Water
Management District (2006b). The horizontal (x) axis of the box plots corresponds to the histogram
x-axis. Asterisks in the box plot denote statistical outliers.


Figure 20. Statistical summary of SAS specific yield data from Southwest Florida Water
Management District (2006b).


Summary for SAS T (ft^2/day)
















0 1500 3000 4500 6000 7500


i I I-- I




95% Confidence Intervals

Mean- I I

Median- I I
500 1000 1500 2000 2500 3000


Anderson-Darling Normality Test
A-Squared 1.50
P-Value < 0.005
Mean 1830.4
StDev 2119.8
Variance 4493649.8
Skewness 1.80288
Kurtosis 2.50311
N 15
Minimum 20.0
1st Quartile 374.0
Median 1260.0
3rd Quartile 2206.0
Maximum 6930.0
95% Confidence Interval for Mean
656.5 3004.3
95% Confidence Interval for Median
459.2 2041.3
95% Confidence Interval for StDev
1552.0 3343.2


Summary for SY















0.00 0.05 0.10 0.15 0.20 0.25






95% Confidence Intervals

Mean I

Median-

0.050 0.075 0.100 0.125 0.150 0.175 0.200


Anderson-Darling Normality Test
A-Squared 0.74
P-Value 0.036
Mean 0.14617
StDev 0.09114
Variance 0.00831
Skew ness -0.59933
Kurtosis -1.35168
N 10
M inim um 0.00510
1st Quartile 0.05625
Median 0.20000
3rd Q uartile 0.20500
Maxim um 0.25660
95% C confidence Interval for Mean
0.08097 0.21137
95% Confidence Interval for Median
0.05117 0.20685
95% C confidence Interval for StDev
0.06269 0.16639








BULLETIN NO. 68


Summary for SAS Kh** (ft/day)




Anderson-Darling Normality Test
A-Squared 0.36
P-Value 0.407
Mean 31.015
StDev 17.940
Variance 321.854
Skewness 0.17215
Kurtosis -1.27803
N 15
Minimum 6.930
1st Quartile 12.000
12 24 36 48 60 Median 32.700
3rd Quartile 50.300
Maximum 59.000
_______ 95% Confidence Interval for Mean
21.080 40.950
95% Confidence Interval for Median
95% Confidence Intervals 14.988 45.706

Mean- I I 95% Confidence Interval for StDev
13.135 28.294
Median- I I
15 20 25 30 35 40 45


Figure 21. Statistical summary of SAS horizontal hydraulic conductivity data from Southwest
Florida Water Management District (2006b). ** calculated from transmissivity and saturated
aquifer thickness.


Figure 22. Statistical summary of SAS vertical hydraulic conductivity data based on falling-head
permeameter analyses of core samples completed at the FDEP-FGS. Due to sampling bias, most
samples represent clay-bearing sediments. Asterisks in the box plot denote statistical outliers.


Summary for SAS Kv (ft/day)






L-









0.1 0.4 0.7 1.0 1.3 1.6 1.9


u-u *




95% Confidence Intervals

Mean I-------*------

Median- 0
-0.05 0.00 0.05 0.10 0.15 0.20 0.25


Anderson-Darling Normality Test
A-Squared 7.75
P-Value < 0.005
Mean 0.09749
StDev 0.36853
Variance 0.13582
Skewness 4.7300
Kurtosis 23.0704
N 26
Minimum 0.00002
st Quartile 0.00004
Median 0.00010
3rd Quartile 0.02215
Maximum 1.85700
95% Confidence Interval for Mean
-0.05137 0.24634
95% Confidence Interval for Median
0.00004 0.00090
95% Confidence Interval for StDev
0.28903 0.50873






FLORIDA GEOLOGICAL SURVEY


OSCEOLA


" POLR


Explanation -
I-] Extent of IAS from Miller (1986)
L I FDEP IAS public supply wells +20km buffer
_ _I Approximate extent of permeable IAS/ICU
(present study)


20 10 0 20
Miles
20 10 0 20
Kilometers


Figure 23. Approximate extent of IAS/ICU permeable zones. The region mapped as IAS/ICU
(Plates 56 and 57) north of this line is dominated by lower permeability hydrogeologic facies.






BULLETIN NO. 68


Up to three relatively more permeable water-
yielding zones exist in the latter regions (Corral
and Wolansky, 1984; Trommer, 1993; Torres et
al., 2001; Knochenmus, 2006), which provide
groundwater to municipalities, industries and
agriculture. During 2000, the IAS/ICU was the
source of approximately 10 percent to 15 percent
of total groundwater withdrawal in DeSoto,
Hardee, and Highlands Counties (Marella 2004).
In Sarasota and Charlotte Counties, the usage
was 32 percent and 75 percent respectively
(Marella, 2004).

Lithology and hydrology of IAS/ICU
permeable zones is heterogeneous and complex.
Where multiple water-producing zones exist,
they are generally laterally discontinuous and
difficult to map, even with the aid of
hydrochemical assessment (Knochenmus and
Bowman, 1998; Knochenmus, 2006).
Moreover, the hydraulic character of the
IAS/ICU is unpredictable due to varying degrees
of vertical and lateral permeability within the
unit. In the northern region, IAS/ICU sediments
generally occur along upland features such as
the Brooksville Ridge, Fairfield Hills and
Sumter and Lake Uplands (Figure 6, Plate 56).
This hydrostratigraphic unit also occurs
throughout the central and southern regions.
Maximum IAS/ICU elevations exceed 125 ft
(38.1 m) MSL along the Brooksville and
Lakeland Ridges. Thickness of the IAS/ICU
ranges to more than 900 ft (274 m) in the
southernmost part of the study area (Plate 57).

Various extents of IAS/ICU water-producing
zones have been proposed within the study area
(Figure 23). In the Florida Aquifer
Vulnerability Assessment (FAVA), (Arthur et
al., in review) the extent includes Miller's
(1986) delineation plus a region defined by the
distribution of FDEP-regulated public water
supply wells that utilize the IAS/ICU (Figure
23). Included among the FDEP supply-well
region is a 12.4 mile (20 km) buffer, which was
added to account for lateral uncertainty (Arthur
et al., in review). In the present study, however,
lithologic data represented in cross sections were
assessed to re-define an approximate northern
limit of IAS/ICU permeable zones (Figure 23).
This redefined extent is comparable to that
proposed by Basso (2003). The region north of


the zone is dominated by variably low-
permeability IAS/ICU sediments, except for
localized relatively permeable sediments within
the Brooksville Ridge (e.g., W-15933; Plate 9).

Within the northeastern part of the study
area, the IAS/ICU is comprised of the
Coosawhatchie Formation (Hawthorn Group)
and possibly other Hawthorn Group units (i.e.,
the Marks Head and Penney Farms Formations)
(W-8883, Plate 5; W-12794, Plate 8). In the
central part of the northern region, the IAS/ICU
occurs along the axis of the Brooksville Ridge
and is comprised of undifferentiated Hawthorn
Group sediments (e.g., W-6903, Plate 5; W-
15933, Plate 9). Scott (1988) suggests that these
sediments at one time likely blanketed the entire
northern region. In the lowlands flanking the
Brooksville Ridge, laterally discontinuous
Hawthorn Group remnants (possibly reworked)
or Pliocene-Pleistocene clayey sediments (e.g.,
W-707, Plate 9) function hydrologically as semi-
confining sediments that promote local FAS
artesian and perched water-table conditions.

As indicated by the hachured areas in Plates
56 and 57, at least half of the northern region is
discontinuous with respect to semi-confining
sediments of the IAS/ICU. This qualitative
delineation is based on inspection of borehole
lithologic data, assessment of the state geologic
map (Scott et al., 2001) and topographic analysis
(i.e., comparing Hawthorn Group distribution
and depth to carbonate rocks with the 15 m (49.2
ft) resolution DEM. In some of these areas, the
IAS/ICU is absent and local aquifer conditions
range from SAS overlying FAS (with varying
degrees of hydraulic separation) to unconfined
FAS. Thickness of the IAS/ICU along the
Brooksville Ridge and the northeastern part of
the study area averages -35 ft (-11 m) and
locally exceeds 100 ft (30.5 m) (W-15933, Plate
9). Highly variable and localized IAS/ICU
thicknesses in these areas are due in part to
infilling ofpaleosinks. Plates 5 and 6 reflect this
scenario, however, due to the localized
occurrence, the IAS/ICU was not delineated.

In the central region, hydrogeologic
properties of the IAS/ICU are highly variable
due to lithologic heterogeneity and complex
interbedding typical of the Hawthorn Group






FLORIDA GEOLOGICAL SURVEY


sediments. The IAS/ICU primarily correlates
with the Hawthorn Group in this region;
however, some post-Hawthorn siliciclastics may
also be included in the uppermost IAS/ICU (e.g.
reworked Hawthorn Group sediments in
southern Pasco and northern Hillsborough
Counties).

Throughout most of Pinellas and
Hillsborough Counties, vertical hydraulic
continuity generally exists between the Tampa
Member (Arcadia Formation) and the Suwannee
Limestone, thereby placing the base of the
IAS/ICU at the top of the Tampa Member
(Broska and Barnette, 1999). In northern
Pinellas County, however, roughly a third of the
wells penetrating the Suwannee Limestone
encounter clay beds at the base of the Tampa
Member. Given the discontinuous nature of
these clays, the base of the IAS/ICU is
considered to correlate with the top of the
Tampa Member although local-scale head
differences may occur between this unit and the
Suwannee Limestone. In southern Hillsborough
County, however, lithologic data from six
adjacent wells indicate that basal Tampa
Member clays are more laterally extensive,
suggesting contiguous hydraulic separation from
the Suwannee Limestone. In this area (Figure
8), the Tampa Member is considered part of the
IAS/ICU (Green et al., 1995; Figure 8; Plates 14,
21 and 20). As additional hydrologic and
lithologic data become available, the base of the
IAS/ICU should be reassessed in these areas.

Mixed siliciclastic-carbonate deposits of the
IAS/ICU thicken southward from -75 ft (22.8
m) in central Polk County to more than 900 ft
(274 m) in Charlotte County (Plate 57) creating
several water-bearing zones (Trommer, 1993).
In most of west central Florida the IAS/ICU is
less permeable than the underlying FAS and
restricts movement of water between the SAS
and FAS (Ryder, 1985).

Where multiple permeable zones exist in the
IAS/ICU in the central and southern regions,
flow regimes are not fully understood. Extents
of these permeable zones need to be better
defined along with groundwater flow patterns in
order to improve management of the IAS/ICU as
a water supply source (Torres et al., 2001). The


hydrologic parameters for these zones have been
well characterized by Basso (2002) for southern
Hillsborough, Manatee and northern Sarasota
Counties. Additional details regarding depths,
thicknesses, extents and hydraulic properties of
these permeable zones are presented in Duerr
and Enos (1991), Barr (1996), Knochenmus and
Bowman, (1998), Torres et al. (2001), Basso
(2003) and Knochenmus (2006).

Distinct differences exist among
potentiometric levels representing IAS/ICU
permeable zones (Duerr, 2001). Regional
IAS/ICU potentiometric maps, however, are
generally constructed from wells open to
multiple permeable zones. As a result, the
potentiometric surface of the IAS/ICU
represents a composite of permeable zones,
which likely contributes to its high variability
across the study area. In May 2001, the
composite head level in the IAS/ICU ranged
from more than 120 ft (36.6 m) MSL in the
"Four Corers" area (northwestern Hardee
County) to approximately 50 ft (15.2 m) MSL in
Highlands County (Duerr, 2001). Within the
study area, IAS/ICU potentiometric elevation
lows occur in southern Hillsborough County and
northern Sarasota County (Duerr, 2001).

Selected hydrogeologic data compiled in
SWFWMD (2006; see also discussion on p.52)
are statistically summarized in Figures 24-27
(transmissivity, storativity, leakance and Kh,
respectively). Laboratory data from the FDEP-
FGS, including falling-head Kv analyses (Figure
28) and total porosity (Figure 29) are also
presented. Basso (2002) presents similar
hydrologic data subdivided based on IAS/ICU
permeable zones. A five order-of-magnitude
difference exists between Kv and Kh mean
values reported herein.

Similar to the SAS data, sampling bias may
account for some of this variation; Kh values
predominately reflect data from IAS/ICU
permeable zones while samples from which Kv
was measured may have been somewhat biased
toward less permeable zones or more indurated
core samples. Moreover, as with all Kv data in
heterogeneous strata, the measured values are
affected by lower-permeability horizons within
the analyzed core segments.








BULLETIN NO. 68


Figure 24. Statistical summary of IAS/ICU transmissivity data from Southwest Florida Water
Management District (2006b).


Figure 25. Statistical summary of IAS/ICU storativity data from Southwest Florida Water
Management District (2006b). Asterisks in the box plot denote statistical outliers.


Summary for IAS T (ft^2/day)
















0 2000 4000 6000 8000 10000 12000

-I i i *




95% Confidence Intervals

Mean- I I

Median- I I
1000 2000 3000 4000


Anderson-Darling Normality Test
A-Squared 2.66
P-Value < 0.005
Mean 2916.2
StDev 3679.0
Variance 13534930.9
Skewness 1.59693
Kurtosis 1.82144
N 30
Minim um 3.0
1st Quartile 265.5
Median 1186.6
3rd Quartile 4975.1
Maximum 12967.9
95% Confidence Interval for Mean
1542.4 4290.0
95% Confidence Interval for Median
655.4 2874.0
95% Confidence Interval for StDev
2930.0 4945.7


Summary for IAS S
















0.0000 0.0004 0.0008 0.0012 0.0016 0.0020 0.0024







95% Confidence Intervals
Mean I S I

Median- I I
0.0001 0.0002 0.0003 0.0004 0.0005 0.0006 0.0007


Anderson-Darling Normality Test
A-Squared 4.03
P-Value < 0.005
Mean 0.000397
StDev 0.000621
Variance 0.000000
Skewness 2.75235
Kurtosis 7.29439
N 25
Minimum 0.000030
1st Quartile 0.000073
Median 0.000180
3rd Quartile 0.000351
Maximum 0.002530
95% Confidence Interval for Mean
0.000141 0.000653
95% Confidence Interval for Median
0.000100 0.000276
95% Confidence Interval for StDev
0.000485 0.000863








FLORIDA GEOLOGICAL SURVEY




Summary for IAS L (per day)


0.00 0.01 0.02 0.03







95% Confidence Intervals


Mean-

Median-


Figure 26. Statistical summary of IAS/ICU leakance data from Southwest Florida Water
Management District (2006b). Asterisks in the box plot denote statistical outliers.


Summary for IAS Kh** (ft/day)




Anderson-Darling Normality Test
A-Squared 3.07
P-Value < 0.005
Mean 38.481
StDev 53.858
Variance 2900.656
Skewness 2.12027
Kurtosis 4.85107
N 30
Minimum 0.045
1st Quartile 4.988
0 60 120 180 240 Median 13.200
Median 13.200
3rd Quartile 59.125
MI Maximum 232.000
F 95% Confidence Interval for Mean
18.370 58.592
95% Confidence Interval for Median
95% Confidence Intervals 8.684 34.030

Mean- I 'I 95% Confidence Interval for StDev
42.893 72.402
Median- I I
10 20 30 40 50 60

Figure 27. Statistical summary of IAS/ICU horizontal hydraulic conductivity data from Southwest
Florida Water Management District (2006b). Asterisk in the box plot denotes statistical outliers.

** calculated from transmissivity and permeable zone thickness.


Anderson-Darling Normality Test
A-Squared 3.70
P-Value < 0.005
Mean 0.003427
StDev 0.008193
Variance 0.000067
Skewness 3.7045
Kurtosis 14.2198
N 16

Minimum 0.000033
1st Quartile 0.000187
Median 0.000968
3rd Quartile 0.001921
Maximum 0.033425
95% Confidence Interval for Mean
-0.000939 0.007792
95% Confidence Interval for Median
0.000196 0.001759
95% Confidence Interval for StDev
0.006052 0.012680














BULLETIN NO. 68


Figure 28. Statistical summary of IAS/ICU vertical hydraulic conductivity data based on falling-
head permeameter analyses of core samples completed at the FDEP-FGS. Asterisks in the box plot
denote statistical outliers.


Figure 29. Statistical summary of IAS/ICU total porosity data based on core sample volumetric
analyses completed at the FDEP-FGS.


Summary for IAS Kv (ft/day)


















0.0035 0.0110 0.0185 0.0260 0.0335


I l- ** *




95% Confidence Intervals

Mean- I I

Median I-I ------I

0.000 0.001 0.002 0.003 0.004 0.005 0.06


Anderson-Darling Normality Test
A-Squared 6.72
P-Value < 0.005

Mean 0.003318
StDev 0.006677
Variance 0.000045
Skewness 2.69316
Kurtosis 7.41148
N 38
Minimum 0.000000
1st Quartile 0.000048
Median 0.000337
3rd Quartile 0.003100
Maximum 0.030300
95% Confidence Interval for Mean
0.001124 0.005513
95% Confidence Interval for Median
0.000102 0.001230
95% Confidence Interval for StDev
0.005443 0.008638


Summary for IAS Total Porosity (% )



A












15.0 22.5 30.0 37.5 45.0 52.5



959

95c
95% Confidence Intervals

Mean- I I 95

Median- I I
30 32 34 36 38 40


nderson-Darling Normality Test
A-Squared 0.34
P-Value 0.447
Mean 34.126
StDev 9.540
Variance 91.010
Skew ness -0.547647
Kurtosis 0.466245
N 19
Minimum 14.130
1st Quartile 28.900
Median 35.370
3rd Quartile 39.400
Maximum 49.550
i% Confidence Interval for Mean
29.528 38.724
o Confidence Interval for Median
29.626 38.225
% Confidence Interval for StDev
7.208 14.108






FLORIDA GEOLOGICAL SURVEY


Floridan aquifer system

The FAS occurs throughout Florida and is
often an artesian aquifer. Artesian conditions
may vary with seasonal rainfall and pumping
conditions. In the study area, springs flow year-
round along parts of coastal Citrus, Pasco and
Hemando Counties (Figure 6; Healy, 1974;
Scott et al., 2004). Other common areas of FAS
discharge include wetlands in the Tsala Apopka
Plain, southern Pasco County, and the Green
Swamp (northwest Polk County). The FAS
discharges into the SAS along the northern part
of the Lake Wales Ridge and also provides
baseflow to surface-water bodies (e.g.,
Hillsborough River). Along the trace of the
Peace River, the FAS discharges into permeable
zones of the IAS/ICU (Sepulveda, 2002).
Similar conditions exist within southern
Sarasota County, southwestern DeSoto County
and most of Charlotte County. Throughout the
remainder of the study area, the FAS is
recharged from overlying aquifer systems.

The top of the FAS does not always coincide
with a specific lithostratigraphic unit. Instead, it
is defined by permeability and hydraulic
connection (Johnston and Bush, 1988).
Moreover, per the Southeastern Geological
Society (1986) definition, the top of the FAS
"generally coincides with the absence of
significant thicknesses of (silici)clastics from the
section and with the top of the vertically
persistent permeable carbonate section." In the
study area, the surface of this hydrostratigraphic
unit may include the following formations in
ascending order: Avon Park Formation, Ocala
Limestone, Suwannee Limestone, and units
within the Hawthorn Group (Trommer, 1993;
Ryder, 1985; Berndt et al., 1998; Corral and
Wolansky, 1984).

Figure 8 summarizes the extent of
lithostratigraphic units that comprise the FAS
surface. The top of the FAS correlates
regionally with the Oligocene Suwannee
Limestone where present; however, in west-
central Florida, the Tampa Member (Arcadia
Formation) of the Hawthorn Group coincides
with the top of the FAS where it is hydraulically
connected to the underlying Suwannee


Limestone (generally Pinellas [e.g., Hickey,
1982; Broska and Barnette, 1999], southern
Pasco, Hillsborough and Manatee Counties
[Green et al., 1995]). In the absence of the
Tampa Member or Suwannee Limestone,
Eocene rocks (Avon Park Formation or Ocala
Limestone) comprise the top of the FAS (Figure
8; Miller, 1986). Based on lithostratigraphic
correlation and the FAS definition applied
herein (see also Appendix 2), the top of the unit
ranges in age from Middle Eocene to Early
Miocene.

In the northern region, the FAS (Plates 4
through 8) includes the Avon Park Formation,
Ocala Limestone and Suwannee Limestone. In
Pasco County (Plate 11), hydrogeologic data
suggest that the Tampa Member is also
hydraulically connected to the FAS. For
example, water levels measured at well W-
16609 (TR 18-2A; Plates 11 and 29) increased
only -1.2 inches (- 3 cm) in elevation while
coring through the Tampa Member into the
Suwannee Limestone (DeWitt, 1990). Overall,
the FAS is unconfined to semi-confined in the
region. Along parts of the northern coastal zone,
laterally extensive confining units are thin to
absent (Plate 56) and hydraulic head differences
allow local recharge to the FAS, which in turn
enhances development of secondary porosity
along fractures and bedding planes in the FAS.
These dissolution-widened channels have a
much higher hydraulic conductivity. For
example, dissolution channels in the Ocala
Limestone are highly developed in Hernando,
Citrus and Marion Counties (Trommer, 1993).
Abundant sinkholes in the region, indicated by
the region's pattern of closed topographic
depressions (Plate 3), locally breach confining
beds.

As indicated by the hydrologic data
presented in the Surficial aquifer system section,
p. 53, local unconfined to semi-confined FAS
conditions exist in the northern region. For
example, water levels in a FAS monitor well and
a surficiall" monitor well at site W-16311
(ROMP LP-4, Plate 7) exhibit nearly identical
elevations, suggesting that confinement is leaky
or absent between surficial sediments and the
carbonates of the FAS. Along the Brooksville
Ridge and parts of the northeastern margin of






BULLETIN NO. 68


the study area, IAS/ICU Hawthorn Group
sediments provide increased confinement of the
FAS. Numerous sinkholes (Plate 3) and paleo-
sinks breach confining clayey sediments that
would otherwise justify delineation of confined
FAS (Plates 6, 7 and 8; Trommer, 1987). As a
result, characterization of certain areas along the
Brooksville Ridge as IAS/ICU and SAS is very
subjective.

In the central, southern and eastern regions,
the zero MSL (sea-level) contour of the FAS
surface (central Hillsborough and Polk Counties;
Plate 58) represents a hinge-line, south of which
the dip of the FAS markedly increases. As
noted in Figure 8, the FAS surface generally
correlates with lithostratigraphic units. The
surfaces of these units have been affected by
depositional, erosional or structural features
(e.g., dissolution, basins, channel scouring,
fracture-controlled drainage systems, possible
faults, etc.). Other variations in the FAS surface
(Plate 58) are due to sub-regional confinement
between lithostratigraphic units. For example,
several wells in central Hillsborough County
indicate that confinement exists between the
Suwannee Limestone and the Tampa Member
(Arcadia Formation), resulting in correlation of
the FAS surface with the Suwannee Limestone.
Uncertainty in the area with regard to vertical
hydraulic connectivity between these two
lithostratigraphic units and lateral/regional
groundwater flow warrant further study.

In the southern region, the FAS surface
generally coincides with the top of the
Oligocene Suwannee Limestone. Along western
DeSoto County, however, the FAS surface
correlates poorly with any specific
lithostratigraphic unit (Figure 8). In some
boreholes, such as W-18117 (ROMP 35,
northwest DeSoto County, Plate 2), the FAS
surface occurs approximately 90 ft (27.4 m)
below the top of the Suwannee Limestone
(LaRoche, 2004). Along the eastern margin of
the study area, the Ocala Limestone comprises
the surface of the FAS, except for a small area in
northeastern Osceola County, where the Ocala
Limestone is absent and the Avon Park
Formation is the uppermost unit (Figure 8;
Gates, 2006). Plate 34 is a representative cross
section of the FAS surface, where it occurs


nearly 100 ft (30.4 m) MSL in well W-15650
(ROMP 88; northern Polk County) and deepens
significantly toward the south where it occurs at
-861 ft (-262 m) MSL in well W-15289.

The FAS potentiometric surface within the
study area (Figure 30) is highly variable and
contains several prominent features. Maximum
elevations (exceeding +130 ft [39.6 m] MSL)
occur in north-central Polk County, near Polk
City and within the Green Swamp. This
maximum is located in the center of a ridge-like
potentiometric high that extends north-northwest
into Marion and Sumter Counties, and south-
southeast along the axis of the Lake Wales
Ridge. Another topographically associated high
occurs along the Brooksville Ridge in Pasco and
Hernando Counties. At least two distinct
potentiometric highs with more than 20 ft (6.1
m) of relief also occur: 1) the Dunellon Gap
(Levy County), and 2) the Big Cypress Swamp
(central Pasco County). Minimum elevations
occur within a few feet below sea level in
southwestern Hillsborough County. Troughs in
the UFA potentiometric surface align with the
Withlacoochee River in Hernando and Pasco
Counties, the Hillsborough and Alafia Rivers
(Hillsborough County), indicating significant
baseflow contributions to these rivers (Figure
30). A less distinct trough is associated with
lakes in eastern Citrus County (i.e., Tsala-
Apopka Lake and Lake Panasofkee). Flow
directions vary considerably in response to these
highs/ridges and lows/troughs; however, in a
very broad sense the groundwater flow in the
UFA for the region west of the Lake Wales
Ridge is generally toward the Gulf coast.

Seasonal perturbations in the potentiometric
surface are generally due to variable recharge
rates and pumping. Regionally, the most notable
difference between the May 2005 (Ortiz and
Blanchard, 2006) and September 2005
potentiometric surface (Ortiz, 2006) is a
broadening of the ridge-like high along the Lake
Wales Ridge in response to the rainy season.
Relative to a predicted "pre-development"
potentiometric surface, Bush and Johnston
(1988) report drawdown exceeding 20 ft (6.1 m)
in a region encompassing roughly one-third of
the District centered on northwest Hardee
County.







FLORIDA GEOLOGICAL SURVEY


Floridan aquifer system
Potentiometric Surface
September, 2005
0 5 10 20 30 40
-Miles
0 5 10 20 30 40
Kilometers
Scale 1:1,750,000
Contour Interval: 10 ft
Projection: Custom FDEP Albers


Explanation --
aMajor Rivers
-- Potentiometric Line (Feet) 7
- Water Management Districts
rI Study Area


Figure 30. Potentiometric surface of the Floridan aquifer system, September, 2005 (from Ortiz,
2006); A Withlacoochee River, B Hillsborough River and C Alafia River. See Figure 1 for
additional river labels.


Gulf
of
Mexico






BULLETIN NO. 68


A meaningful comparison of the IAS/ICU
potentiometric surface (Duerr, 2001) with that of
the FAS is qualitative at best (see discussion
starting on page 62). A more accurate, although
site-specific method for assessing the
recharge/discharge relation between the
IAS/ICU and FAS is to compare water levels in
nested wells, many of which are located at
District ROMP sites. As noted above, Miller
(1986) subdivided the FAS into the Upper
Floridan aquifer (UFA) and the Lower Floridan
aquifer (LFA). The UFA is the principal source
of groundwater throughout the study area except
for Charlotte County, where only 20 percent of
total w ithdra \als originate from the UFA (based
on data from 2000 as compiled by Marella,
2004) due to naturally poor water quality. The
most productive units of the UFA are located
within the Avon Park Formation, Ocala
Limestone and the Suwannee Limestone (Ryder,
1985).

A highly permeable facies of the FAS,
referred to as the "Boulder Zone" (Kohout,
1965), is characterized by cavernous, fractured
dolostones with very high transmissivities (Puri
et al., 1973). Vernon (1970) reported "Boulder
Zone" facies throughout the Florida peninsula.
More recently, however, this hydrogeologic
facies has been recognized as discontinuous and
found to be limited to the southern third of the
Florida peninsula (Miller, 1986). The facies
does not occur within the same lithostratigraphic
unit throughout its extent (Miller, 1986).
Maliva et al. (2001) report occurrences of
"Boulder Zone" facies in the Early Eocene
Oldsmar Formation in Charlotte, Lee and Collier
County injection wells. This facies has been
reported to occur at depths shallower than -1300
ft (-396.2 m) MSL in Charlotte County (Maliva
et al., 2001), which corresponds to Avon Park
Formation carbonates. In the southernmost
peninsula, the facies occurs within the Paleocene
Cedar Keys Formation as well as the Eocene
Avon Park Formation and Ocala Limestone
(Puri and Winston, 1974).

Wolansky et al. (1980) mapped "the highly
permeable dolomite zone" of the Avon Park
Formation throughout the southern two-thirds of
the District. These well-indurated dolostones
are commonly fractured and contain large


dissolution channels. The zone occurs -100 ft
(- 30.5 m) below the top of the Avon Park
Formation in the central part of the study area
and 400 ft (- 122 m) below the Avon Park
Formation surface in the southern region. The
SAS and IAS/ICU generally provide
confinement of the UFA (Berndt et al., 1998)
except for areas in the northern region where the
UFA may be unconfined and where karst and
paleokarst promote inter-aquifer connectivity.
Hydrogeologic conditions vary considerably
between the northern and southern regions
depending on the degree of confinement.

The interpolated surface of the UFA ranges
from greater than 75 ft (22.9 m) MSL along the
Brooksville Ridge to less than -825 ft (-251 m)
MSL in southern Charlotte County (Plate 58).
Locally, maximum elevations exceed 130 ft
(39.6 m) along the Brooksville Ridge (W-14917
[ROMP 109], Plate 7). A map of overburden
thickness provides a different perspective on the
depth to the top of the UFA (Figure 31). This
map, developed by subtracting the UFA surface
from a 15 m (49.2 ft) resolution DEM (Arthur et
al., in review), allows comparison of the aquifer
system to geomorphic features. For example,
note the thin overburden along the Brooksville
Ridge compared to the Lake Wales Ridge, as
well as the maximum overburden thickness of
-900 ft (-274 m) in Charlotte County.

The base of the UFA occurs within the lower
Avon Park Formation, where vertically and
laterally persistent evaporite minerals (gypsum
and anhydrite) are present in the carbonate rocks
(e.g., Ryder, 1985; Hickey, 1990; see Middle
Floridan confining unit [MFCU], p. 75, for more
information). Thickness of the UFA, calculated
as a "grid difference map," ranges from less than
300 ft (91.4 m) to more than 1500 ft (457 m;
Figure 32). Regional subjacent confinement of
the UFA is comprised of the MFCU where
present. Examples of basal UFA confinement
are represented in several cross sections (e.g.,
Plates 7, 9, 21 and 31). Note, however, that
Miller's (1986) delineation of overlapping
MFCU units by default suggests that the base of
the UFA in these areas is a complex
discontinuous surface. This aspect of the UFA
is described in more detail in the next section.







FLORIDA GEOLOGICAL SURVEY


Floridan aquifer system
Overburden Thickness
0 5 10 20 30 40
m mMiles
0 510 20 30 40
Kilometers
Scale 1:1,750,000
Projection: Custom FDEP Albers


I


Explanation
| Study Area
- Water Management Districts
FAS Overburden Thickness
900 ft
450 ft


Figure 31. Floridan aquifer system overburden thickness as predicted from geospatial modeling
(i.e., DEM minus top of FAS). The map is not contoured due to extreme resolution differences in
source grids.


Gulf
of
Mexico







BULLETIN NO. 68


Upper Floridan aquifer
Thickness
0 5 10 20 30 40
Im 3 Miles
0 510 20 30 40
Kilometers
Scale 1:1,750,000
Contour Interval: 150 ft
Projection: Custom FDEP Albers


II
I

'I


Explanation

I Study Area
Contours
- Water Management Csit[r.:ti.
UFA Thickness
S1600 ft
665 ft
265 ft


Figure 32. Thickness of the Upper Floridan aquifer (includes non-potable).


Gulf
of
Mexico







FLORIDA GEOLOGICAL SURVEY


The LFA lies beneath MFCU strata and
consists of the lower part of the Avon Park
Formation, the Oldsmar Formation and the
upper part of the Cedar Keys Formation (Miller,
1997). The Cedar Keys Formation forms the
lower boundary of the LFA and generally
consists of persistently dolomitized carbonates
with widespread bedded and intergranular
gypsum and anhydrite. Except for the
northeastern part of the study area, the LFA is
commonly highly saline and not used as a
potable or an economically treatable water
source. Research on use of the LFA as a
sustainable fresh water resource for the
northeastern part of the District is underway
(Southwest Florida Water Management District,
2006a).

The LFA is the lowermost known and well-
defined aquifer, ranging in elevation from -400
ft (-122 m) MSL in the northeastern part of the
study area to more than -2500 ft (-762.0 m)
MSL in Sarasota and Charlotte counties; LFA
thicknesses exceed 2,400 ft (731.5 m) in the
southeast part of the study area (Miller, 1986).
Per findings of the CFHUD II (Copeland et al.,
in review) the low-transmissivity strata lying at
the base of the FAS (e.g., the "sub-Floridan
confining unit" referenced in Southeastern


Geological Society, 1986) is informally referred
to as "undifferentiated aquifer systems."

Hydraulic properties of the FAS are
summarized in Figures 33-38 for the parameters
transmissivity, storativity, leakance, Kh, and
total porosity, respectively. A large degree of
vertical anisotropy exists in the FAS (e.g., Ryder
et al., 1980; Ryder, 1982) due to variations in
grain size and diagenetic factors affecting
permeability (e.g., Budd, 2002; Budd and
Vacher, 2004). Median horizontal and vertical
hydraulic conductivity values differ by three
orders of magnitude, which is notably less than
the difference between these same parameters in
the SAS and IAS/ICU. This is due in part to a
relative lack of sampling bias in the analyzed
FAS core samples. A greater degree of
anisotropy in the SAS and IAS/ICU relative to
the FAS is another possible contributing factor.
Anomalously high transmissivity values (Figure
33) likely reflect the influence of dual-porosity
(i.e. fracture/conduit flow). It is also noteworthy
that spatial analysis of dolines (e.g., sinkholes)
in the northern and central region indicates a
statistically significant correlation between FAS
hydraulic conductivity and doline-area ratios
(Armstrong et al., 2003).


Summary for UFA T (ft^2/day)


A nderson-D arling Normality Test
A-Squared 18.49
P-Value < 0.005
Mean 88602
StDev 187201
Variance 35044192303
Skewness 4.4198
Kurtosis 21.3092
N 90
Minimum 1300
0 200000 400000 600000 800000 1000000 1200000 1st Quartlle 18650
M edian 38369
3rd Q uartile 69789
-J -- Maximum 1203210
95% Confidence Interval for Mean
49393 127810
95% Confidence Intervals 95% Confidence Interval for Median
29279 48540
Mean- I 95% Confidence Interval for StDev
Median 163279 219401
Median
20000 40000 60000 80000 100000 120000 140000

Figure 33. Statistical summary of UFA transmissivity data from Southwest Florida Water
Management District (2006b). Asterisks in the box plot denote statistical outliers.









BULLETIN NO. 68


Figure 34. Statistical summary of UFA storativity data from Southwest Florida Water
Management District (2006b). Asterisks in the box plot denote statistical outliers.


Figure 35. Statistical summary of UFA leakance data from Southwest Florida Water Management
District (2006b). Asterisks in the box plot denote statistical outliers.


Summary for UFA S

















0.000 0.016 0.032 0.048 0.064 0.080 0.096







95% Confidence Intervals

Mean-

Median-

0.000 0.001 0.002 0.003 0.004 0.005


A nderson-Darling Normality Test
A-Squared 24.66
P-Value < 0.005
Mean 0.002660
StDev 0.010812
Variance 0.000117
Skew ness 6.6858
Kurtosis 47.7119
N 81
Minimum 0.000000
1stQuartile 0.000265
Median 0.000640
3rd Q uartile 0.001200
Maximum 0.086000
95% Confidence Interval for Mean
0.000269 0.005050
95% Confidence Interval for Median
0.000404 0.000935
95% Confidence Interval for StDev
0.009365 0.012792


Summary for UFA L (per day)

















0.000 0.012 0.024 0.036 0.048 0.060 0.072


** *



95% Confidence Intervals

Mean- II

Median- -

0.000 0.001 0.002 0.003 0.004 0.005 0.006


Anderson-Darling Normality Test
A-Squared 15.47
P-Value < 0.005
Mean 0.003141
StDev 0.010668
Variance 0.000114
Skewness 5.6131
Kurtosis 33.5295
N 59
Minimum 0.000029
1st Quartile 0.000147
Median 0.000300
3rd Q uartile 0.001800
Maximum 0.072380
95% Confidence Interval for Mean
0.000361 0.005921
95% Confidence Interval for Median
0.000241 0.000567
95% Confidence Interval for StDev
0.009031 0.013036








FLORIDA GEOLOGICAL SURVEY


Figure 36. Statistical summary of UFA horizontal hydraulic conductivity data from Southwest
Florida Water Management District (2006b). ** calculated from transmissivity and permeable
zone thickness. Asterisks in the box plot denote statistical outliers.


Summary for UFA Kv* (ft/day)



Anderson-Darling Normality Test
A-Squared 26.02
P-Value < 0.005
Mean 0.10028
StDev 0.22808
Variance 0.05202
Skewness 4.2139
Kurtosis 21.8401
N 137
i-- M minimum 0.00000
0.0 0.3 0.6 0.9 1.2 1.5 1st Q uartile 0.00565
Median 0.01967
3rd Quartile 0.08725
|- I* Maximum 1.72957
95% C confidence Interval for Mean
0.06175 0.13882
95% Confidence Intervals 95% Confidence Interval for Median
M 0.01422 0.02795
Mean 95% Confidence Interval for StDev

Median 0.20389 0.25882
Median I-

0.000 0.025 0.050 0.075 0.100 0.125 0.150


Figure 37. Statistical summary of UFA vertical hydraulic conductivity data based on results of
falling-head permeameter analyses of core samples completed at the FDEP-FGS. Asterisks in the
box plot denote statistical outliers.


Summary for UFA Kh** (ft/day)















0 1000 2000 3000 4000 5000 6000


-I-& 9
9.


95% Confidence Intervals 95

Mean- I

Median- -

100 200 300 400 500


Anderson-Darling Normality Test
A-Squared 21.43
P-Value < 0.005
Mean 276.61
StDev 787.65
Variance 620386.37
Skewness 5.8896
Kurtosis 38.2409
N 86
Minim urn 7.65
1st Quartile 50.50
Median 91.90
3rd Quartile 178.75
Maxim urn 6050.00
5% Confidence Interval for Mean
107.74 445.49
% Confidence Interval for Median
78.51 110.07
5% Confidence Interval for StDev
684.97 926.82







BULLETIN NO. 68


Summary for UFA Total Porosity (% )


Anderson-Darling Normality Test
A-Squared 1.91
P-Value < 0.005
Mean 37.056
StDev 8.601
Variance 73.978
Skewness -1.22649
Kurtosis 2.93402
N 117
SMinimum 2.300
0 10 20 30 40 50 1st Q uartile 31.950
S Median 38.730
3rd Quartile 42.625
IM axim um 53.490
95% Confidence Interval for M ean
35.481 38.631
95% Confidence Intervals 95% Confidence Interval for Median
S37.100 39.950
Mean II 95% Confidence Interval for StDev
7.622 9.870
Median I I
35 36 37 38 39 40

Figure 38. Statistical summary of UFA total porosity data based on results of core sample
volumetric analyses completed at the FDEP-FGS. Asterisks in the box plot denote statistical
outliers.


Middle Floridan confining unit

Miller (1986) recognizes three confining
units within the study area (Units I, II and VI)
that separate the UFA from the LFA; however,
in context of the overall FAS he states: "... the
units act as a single confining unit within the
main body of permeable limestone that
constitutes the aquifer system." In the present
study, we adopt a more descriptive
hydrostratigraphic name for the Miller's (1986)
"middle confining unit" of the FAS: the Middle
Floridan confining unit (MFCU). This name
simply associates the confining units with the
aquifer system in which they reside. This
nomenclature has also been adopted by the
CFHUD II (Copeland, et al., in review).
Complexity of the MFCU within and beyond the
study area is readily apparent given the seven
units mapped by Miller (1986) separating the
UFA from the LFA in Florida. On a more local
scale, delineation of the base of the UFA
becomes challenging where overlapping
confining units of the MFCU occur.

Within the study area, unit I occurs along the


eastern margin and is identified as a leaky
confining unit that is "...not much different from
that of the permeable zones vertically adjacent to
it..." (Miller, 1986). Units II and VI are
identified as carbonates (primarily dolostone)
with intergranular gypsum and comprise a
hydrogeologically significant confining facies
that separates the UFA from the LFA in the
study area.

The MFCU mapped herein includes Miller's
(1986) units II and VI and is principally
identified based on lithology and mineralogy:
borehole samples that contain thin
gypsum/anhydrite beds or intergranular
gypsum/anhydrite > five percent (by volume).
While some may consider five percent too
conservative (e.g., too high), a notable relative
increase in matrix confining properties is the
emphasis herein, recognizing that transition
zones may occur, as well as zones where
variable precipitation and dissolution of these
minerals may have occurred. Geophysical logs
and water-quality data are also used to identify
or infer evidence of the MFCU. In addition to
data generated for this report, data from Miller







FLORIDA GEOLOGICAL SURVEY


(1988), Hickey (1982), Sacks (1996), Stewart
(1966), O'Reilly et al. (2002) and unpublished
SWFWMD ROMP reports are also used to
interpolate the MFCU surface.

Miller's (1986) unit II, which reaches depths
of -1,900 ft (-579.1 m) MSL in Sarasota County
correlates with most of the MFCU surface (Plate
59). Unit VI (Miller, 1986) reaches depths of -
2,100 ft (-640.1 m) MSL in southeastern DeSoto
County and along the southern half of Charlotte
County. According to data from Miller (1988),
the two units overlap in western
Highlands/eastern DeSoto Counties as well as
western Charlotte and Lee Counties. Several
wells investigated by Miller (1986, 1988) and in
the present study indicate that the MFCU may
not be laterally continuous throughout the study
area; however for purposes of regional mapping,
the MFCU is contoured continuously and the
areas in question are annotated (Plate 59).


The initial protocol for mapping the MFCU
was to reflect the uppermost occurrence of the
unit in a borehole using the lithologic criteria
outlined above. This method, however, yielded
anomalous surface patterns and vertical
discontinuities where Miller's (1986) units II
and VI coexist in a well. A MFCU surface map
based on this initial protocol yielded two dome-
like features in the southern region in the
vicinity of these wells. The domes represented
unit II overlying unit VI, separated by high
permeability zones (Miller, 1988) and thus did
not reflect a contiguous mappable surface. The
distribution of well control for unit II (Plate 59)
also brings into question the degree to which
unit II is laterally continuous. Many sufficiently
deep wells within the extent of unit II do not
encounter the unit. It is also noteworthy that
Miller (1986) describes units II and VI as having
nearly indistinguishable lithologic characteristics.


Figure 39. Interpretations of the MFCU in the study area. Upper cross section reflects MFCU units
mapped by Miller (1986); lower cross section reflects alternate interpretation showing continuity
between Miller's units II and VI, with isolated MFCU middle to upper Avon Park confinement
overlying the deeper, more laterally continuous unit. See Plate 59 for cross-section location.


A A'
NORTH 2 a SOUTH
Fee I F M Fw
MSL f MSL
0 0

-500- 500
Miller (1986.1988)
MFCU -1000ooo -1000
Unit II
UnitVI -i SO- 1500
2000 -2 000

-2500- -2500


Present Study o o
MFCU = -500o -s00
Locally
Shallow | ia Olow000 t-
MFCU






BULLETIN NO. 68


Evaluation of the regional slope of the
MFCU, lithologic similarities between the units,
and sparse data for unit II lead to an alternate
interpretation: unit II north of Manatee and
Hardee Counties may correlate with unit VI
south of these counties (Figure 39). In this
interpretation, isolated MFCU facies occur
approximately 400 ft (122 m) above the lower
MFCU unit in southwestern Highlands and
western Charlotte Counties. Plate 59 and Figure
39 (bottom half) reflect this latter interpretation.
Wells that encountered both MFCU facies (II
and VI) are represented by green symbols (Plate
59) and are labeled with the elevation of the
shallower discontinuous MFCU facies, which is
informally referred to as the "middle to upper
Avon Park confining unit." Data in Miller
(1988) indicate a high permeability zone
between the base of the "middle to upper Avon
Park confining unit" and the MFCU as mapped
herein within all wells containing both of
Miller's MFCU facies (II and VI).

Based on comparison of Plate 38 with
Miller's (1986) Middle Eocene isopach, the
MFCU as defined and mapped in this study
generally occurs within the lower half of the
Avon Park Formation. Exceptions to the
generalization include Marion, Osceola and
Pinellas Counties, where the MFCU occurs
within the upper third of the Avon Park
Formation. Several cross sections contain wells
that penetrate the MFCU (e.g., Plates 7, 9, 21,
29, 30 and 34). In the northwestern part of the
study area, the elevation of the MFCU is
generally deeper than -400 ft (-122 m) MSL.
The unit dips southward to depths below -2100
ft (-640.1 m) MSL in Charlotte County. South
of the study area, Reese (2000) mapped the
"dolomite-evaporite unit in the middle confining
unit" of the FAS, recognizing the significance of
dense unfractured dolostones in his study area.
He also notes that this unit may locally be
considered the top of the MFCU, which is
generally supported by the MFCU surface in
Plate 59. It is possible that the few wells with
shallower elevations in Reese's (2000)
"dolomite evaporite unit" map are related to
the discontinuous "middle to upper Avon Park
confining unit" described herein.

Presence of the MFCU is debatable for two
regions within the eastern half of the study area.


Throughout most of Marion County (including
parts of Alachua, Sumter and Lake Counties),
the MFCU is inferred. Borehole cuttings from
multiple wells in the area show no evidence of
gypsum/anhydrite; however, anomalously high
sulfate concentrations (some exceeding 500
mg/L; Sacks, 1996) in FAS groundwater
samples suggest the MFCU may be present. As
such, this area is denoted on Plate 59 as "MFCU
inferred based on water quality data." In eastern
Polk County, Miller (1986) mapped the MFCU;
however, available well control (this study and
Miller, 1988), as well as water quality data for
the area, yields no direct evidence that it is
present. Sprinkle (1989) and Katz (1992) report
relatively low sulfate concentrations (< 50
mg/L) within the UFA in the area. To
emphasize this uncertainty the MFCU in this
area is labeled "MFCU possibly absent: limited
data" (Plate 59).

Hydraulic conductivity analyses of MFCU
rocks were not completed for this study;
however, data exists in SWFWMD and
consultant's reports. For example, Hickey
(1982) reports hydraulic conductivities ranging
from 1.1 ft/day to 6.0x10-7 ft/day (3.8x10-4 to
2. 1xl0-10 cm/sec) based on core representing the
"lower confining bed" (greater than -1000 ft
[-305 m] MSL) in Pinellas County. To provide
characterization of MFCU hydraulic
conductivity and total porosity, data has been
compiled from three injection well sites:
Knight's Trail, Sarasota County, (Law
Environmental, Inc., 1989), Burnt Store
Utilities, Charlotte County, (ViroGroup, Inc.,
1995) and Punta Gorda, Charlotte County, (City
of Punta Gorda, Water Resource Solutions, Inc.,
and Boyle Engineering Corporation, 2001).
Data from Stewart (1966) and Hickey (1982)
and Montgomery Watson Americas (1997) are
also included. Hydraulic conductivity (Kv) for
the 21 MFCU cores analyzed in these studies
range from 1.5x10-' ft/day to 1.0xl0-6 ft/day
(5.3x10-' to 3.53x10-10 cm/sec), with a median
value of 1.84x10-3 ft/day (6.5x10-7 cm/sec;
Figure 40). Total porosity for these samples
average 17.2 percent (median = 19.6 percent)
and range from 5 percent to 30 percent (Figure
41). Basso (2002) reports Kh values ranging
from .002 to .04 ft/day (7.06x10-07 to 1.4x105
cm/sec). Transmissivity data range from 0.08 to
2.9 ft2/day (0.86 to 31.2 m2/day).








FLORIDA GEOLOGICAL SURVEY


Figure 40. Statistical summary of MFCU vertical hydraulic conductivity data based on results of
falling-head permeameter analyses of core samples; compiled from Stewart (1966), Hickey (1982),
Law Environmental (1989), ViroGroup (1995), Montgomery Watson Americas, Inc., (1997), City of
Punta Gorda, et al., (2001). Asterisks in the box plot denote statistical outliers.




Summary for MFCU Total Porosity (%)




Anderson-Darling Normality Test
A-Squared 0.77
P-Value 0.038
Mean 17.147
StDev 6.854
Variance 46.980
Skewness -0.499332
Kurtosis -0.197892
N 19
Minimum 5.000
1st Quartile 13.700
4 8 12 16 20 24 28 32 Median 19.600
3rd Quartile 21.000
M maximum 30.000
95% Confidence Interval for Mean
13.844 20.451
95% Confidence Interval for Median
95% Confidence Intervals 15.169 21.000
Mean I I 95% C confidence Interval for StDev
5.179 10.136
Median- I I
14 16 18 20 22


Figure 41. Statistical summary of MFCU total porosity data based on volumetric analyses of core
samples; compiled from Stewart (1966), Law Environmental (1989), ViroGroup (1995),
Montgomery Watson Americas, Inc. (1997), City of Punta Gorda, et al., (2001).


Summary for MFCU Kv (ft/day)
















0.00 0.03 0.06 0.09 0.12 0.15






95% Confidence Intervals
Mean I

Median
-0.005 0.000 0.005 0.010 0.015 0.020 0.025


Anderson-Darling Normality Test
A-Squared 5.50
P-Value < 0.005
Mean 0.010796
StDev 0.032419
Variance 0.001051
Skewness 4.2710
Kurtosis 18.8184
N 21
Minimum 0.000001
1st Quartile 0.000326
Median 0.001840
3rd Quartile 0.007085
Maximum 0.149000
95% Confidence Interval for Mean
-0.003961 0.025553
95% Confidence Interval for Median
0.000426 0.004443
95% Confidence Interval for StDev
0.024803 0.046816






BULLETIN NO. 68


SUMMARY

The hydrogeologic framework of the
Southwest Florida Water Management District
region described in this report is spatially
characterized through a series of 32 maps (plates
and figures) and 34 cross sections. Lithologic,
hydrologic and geophysical data from more than
1050 wells comprise a database of subsurface
elevations and thicknesses for nine
lithostratigraphic and four hydrostratigraphic
units represented in these maps and cross
sections. Elevations of unit boundaries for most
of the wells used in the maps and cross sections
have been confirmed through visual inspection
of cores and cuttings by the authors and those
acknowledged in this report. Additional data on
which the maps and cross sections are based are
incorporated from peer-reviewed reports and
interpreted from geophysical logs and existing
lithologic descriptions. The lithostratigraphic
units are discussed in terms of age, lithology,
mineralogy, common fossils, sedimentary
structures, porosity/permeability, contact
relations with other units, facies changes, spatial
distribution (vertical and lateral), gamma-ray log
responses, hydrostratigraphic unit correlations
and depositional environments.
Hydrostratigraphic units are similarly discussed
in terms of spatial distribution, regional and
local hydraulic characteristics, hydrogeologic
properties and correlation with lithostratigraphic
units.

Among the challenges that exist when
creating subsurface stratigraphic maps based on
well data is the need to balance three factors: 1)
accuracy of the interpolated contours relative to
the data on which each map is based, 2) the
implicit resolution of the map, which is depicted
by the contour interval and the degree of
perturbations in the contours and 3) an accurate
regional characterization of the unit being
mapped. For example, a map that is 100 percent
accurate with respect to elevations or
thicknesses may overemphasize local anomalies
such as karst features. Although a small
percentage of wells represent these anomalous
elevations, the wells also represent an
infinitesimal fraction of the total number of
anomalous features in the mapped surface. In


other words, thousands of paleosink features
may exist in the top of a carbonate unit;
however, less than five percent of the wells in
the database may have encountered one of these
features. Hence, a regional-scale map would be
more representative of the true regional
character of the surface (or thickness) if the local
anomalies had less influence on the interpolated
surface. Moreover, a highly accurate map may
also result in jagged, irregular contours, which
may imply changes in elevation (or thickness) at
a scale that is not justified by the distribution
and density of the well data.

To achieve an appropriate balance of the
aforementioned factors, an iterative process of
data evaluation, sample inspection, data
interpretation, and spatial and statistical analysis
was completed. For the final maps, kriging was
used to interpolate map surfaces, which were
then corrected as needed for consistency with
land surface and other mapped units. The
interpolated surfaces were then smoothed to
reflect the regional character of each mapped
unit. The surface interpolations also provide
GIS coverages that can be applied in
groundwater flow models and 3D applications.

The cross sections focus on data from cores,
with an emphasis on those collected through the
SWFWMD Regional Observation and Monitor-
well Program (ROMP). Data from geophysical
logs as well as cores and cuttings archived in the
Florida Geological Survey sample repository
were used to fill gaps in the cross-section well
coverage. Of the 34 cross sections, nine trend
approximately north-south, averaging
approximately 60 mi (-96 kilometers) in length,
while the remaining sections generally trend
east-west and average approximately 35 mi (-56
km) in length. Graphical representation of
borehole data from 149 wells used in the cross
sections include lithostratigraphic and
hydrostratigraphic boundaries and cross-well
correlations, lithology, mineralogy and gamma-
ray log response. Each section also includes
topographic profiles labeled with selected
anthropogenic features.

The relationship between lithostratigraphic
and hydrostratigraphic units is straightforward in
many parts of the study area; however, the






FLORIDA GEOLOGICAL SURVEY


association can be locally complex and
indistinct. In either case, the relationship
depends on the degree of hydraulic continuity
between and among lithostratigraphic units. The
variable hydrogeologic setting in the northern
region serves as an example: characterization of
the SAS (water-table aquifer) is complicated by
lateral hydraulic discontinuities. Regionally, the
water table may reflect the potentiometric
surface of the unconfined FAS (e.g., west of the
Brooksville Ridge); however, local hydraulic
separation between the SAS and the FAS may
exist. As a result, delineation of a regionally
extensive SAS that is significant as a water-


producing unit is the subject of some debate.

The framework of stratigraphy and
hydrogeology developed during this
investigation serves as a foundation for
numerous applications, ranging from more
refined hydrogeological mapping to mineral
resource assessments, well-field designs and
groundwater models. Regardless of the
application, it is our hope that this study
facilitates science-based decision making
regarding the protection, conservation and
management of the solid-earth and water
resources of southwestern Florida.






BULLETIN NO. 68


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Full Text

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HYDROGEOLOGIC FRAMEWORK OF THE SOUTHWEST FLORIDA WATER MANAGEMENT DISTRICT FLORIDA DEPARTMENT OF EN VIRONMENTAL PROTECTION FLORIDA GEOLOGICAL SURV EY BULLETIN NO. 68 Prepared in cooperation with the Southwest Florida Water Management District

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FLORIDA DEPARTMENT OF ENVIRONMENTAL PROTECTION Michael W. Sole, Secretary LAND AND RECREATION Bob G. Ballard, Deputy Secretary OFFICE OF THE FLORIDA GEOLOGICAL SURVEY Walter Schmidt, State Geologist and Director ADMINISTRATIVE AND GEOLOGICAL DATA MANAGEMENT SECTION Jacqueline M. Lloyd, Assistant State Geologist David Arthur, Computer Programmer Analyst Leslie Knight, Administrative Assistant Traci Billingsley, Administrative Assistant Anthony Miller, Environmental Specialist Paulette Bond, Professional Geologist Sarah Ramdeen, Computer Program Analyst Doug Calman, Librarian Ging er Rinkel, Secretary Specialist Brian Clark, Environmental Specialist Frank Rupert, Professional Geologist Jeff Erb, Systems Programmer Carolyn Stringer, Management Analyst Jessie Hawkins, Custodian GEOLOGICAL INVESTIGATIONS SECTION Thomas M. Scott, Assistant State Geologist Ken Campbell, Professional Geologist Patrick Madden, Laboratory Technician Brie Coane, Geologist Harl ey Means, Professional Geologist Rick Green, Professional Geologist Mike Nash, Laboratory Technician Eric Harrington, Engineering Technician David Paul, Professional Geologist Laura Hester, Laboratory Technician Dan Phelps, Professional Geologist Ron Hoenstine, Professional Geologist Supervisor Guy Richardson, Engineering Technician Jessie Hurd, Laboratory Technician Wade Stringer, Engineering Specialist Michelle Ladle, Laboratory Technician David Wagner, Laboratory Technician Christopher Williams, Geologist HYDROGEOLOGY SECTION Jonathan D. Arthur, Assistant St ate Geologist (Acting Director) Rick Copeland, Professional Geologist Lisa Fulton, Environmental Specialist Adel Dabous, Environmental Specialist Tom Greenhalgh, Professional Geologist Rodney DeHan, Senior Research Scientist Nick John, Geologist Scott Barrett Dyer, Environmental Specialist Clint Kromhout, Professional Geologist Cindy Fischler, Professional Geologist Amber Rainsford, Environmental Specialist

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STATE OF FLORIDA DEPARTMENT OF ENVIRONMENTAL PROTECTION Michael W. Sole, Secretary LAND AND RECREATION Bob G. Ballard, Deputy Secretary FLORIDA GEOLOGICAL SURVEY Walter Schmidt, State Geologist and Director BULLETIN NO. 68 HYDROGEOLOGIC FRAMEWORK OF THE SOUTHWEST FLORIDA WATER MANAGEMENT DISTRICT By Jonathan D. Arthur, Cindy Fischler, Clint Kromhout, James M. Clayton, G. Michael Kelley, Richard A. Lee, Li Li, Mike O'Sullivan, Richard C. Green, and Christopher L. Werner Published for the FLORIDA GEOLOGICAL SURVEY Tallahassee, Florida in cooperation with the SOUTHWEST FLORIDA WATER MANAGEMENT DISTRICT 2008

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ii Printed for the Florida Geological Survey Tallahassee 2008 ISSN 0271-7832

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iii In memory of the spirited life and geoscience contributions of Rick Lee (1956 2007)

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iv

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v PREFACE The Florida Geological Survey/Florida Departme nt of Environmental Pr otection is publishing as its Bulletin 68, the Hydrogeologic Framework of the Sou thwest Florida Water Management District . The report summarizes a multi-year study of the three-dimensional framework of southwestern Florida’s hydrogeol ogy, with a focus on the subsur face distribution of aquifer systems and geologic units comprising these syst ems. As groundwater resources in Florida experience increased stress due to rapid population growth, an understanding of the aquifer systems is invaluable to environmental managers, scientists, planners and the public as decisions are made regarding use, protecti on and conservation of these vulne rable resources. The FDEPFGS is pleased to have had the opportunity to pa rtner with the Southwest Florida Water Management District to complete this report. State Geologist and Director Florida Geological Survey Florida Department of Environmental Protection

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vi

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vii TABLE OF CONTENTS Abbreviations, acronyms and conversions........................................................................................ ...........xi Acknowledgements.....................................................................................................................................xii ntroduction .................................................................................................................................................1 Background...............................................................................................................................................1 Purpose and scope.................................................................................................................................1 Study area..................................................................................................................... .........................2 Previous investigations.........................................................................................................................2 Physical setting............................................................................................................... ..........................5 Geology.................................................................................................................................................5 Structure................................................................................................................................................7 Geomorphology.................................................................................................................. ................11 Physiographic provinces and features........................................................................................... ..11 Sinkholes...................................................................................................................... ...................15 Springs........................................................................................................................ ....................15 Hydrogeology.....................................................................................................................................17 Methods........................................................................................................................ ..............................20 Sample description............................................................................................................. .....................20 Delineation of boundaries...................................................................................................... .................21 Formations/Members............................................................................................................. .............21 Aquifer sy stems................................................................................................................ ..................21 Cross-section construction..................................................................................................... .................22 Topography..................................................................................................................... ....................22 Lithology...................................................................................................................... .......................24 Gamma-ray logs................................................................................................................. .................24 Aquifer sy stems................................................................................................................ ..................24 Map development and data management................................................................................................24 Map interpolation a nd spatial accuracy......................................................................................... .....27 Contour interval selection..................................................................................................... ..............30 Stratigraphy................................................................................................................... ..............................30 Lithostratigraphy.............................................................................................................. .......................30 Introduction................................................................................................................... ......................30 Eocene Series.................................................................................................................. ....................30 Oldsmar Formation.............................................................................................................. ...........30 Avon Park Formation............................................................................................................ ..........31 Ocala Limestone.............................................................................................................................34 Oligocene Series............................................................................................................... ..................37 Suwannee Limestone............................................................................................................. .........37 Oligocene-Plio cene Se ries...................................................................................................... ............40 Hawthorn Group................................................................................................................. ............40 Arcadia Formation.............................................................................................................. ........40 Nocatee Me mber................................................................................................................. ....43 Tampa Member................................................................................................................... ....43 “Venice Clay”.................................................................................................................. .......45 Peace River Fo rmation.......................................................................................................... ......45 Bone Valley Member............................................................................................................. .48

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viii TABLE OF CONTENTS (CONTINUED) Hawthorn Group (undifferentiated)............................................................................................48 Pliocene and younger Series.................................................................................................... ...........49 Post-Hawthorn Group sediments.................................................................................................. ..49 Tamiami Formation.............................................................................................................. .......50 Cypresshead Formation.......................................................................................................... .....50 Caloosahatchee Formation....................................................................................................... ...50 Fort Thompson Formation........................................................................................................ ..51 Hydrostratigraphy.............................................................................................................. .....................52 Introduction................................................................................................................... ......................52 Hydrogeological properties..................................................................................................... ........52 Surficial aquifer system....................................................................................................... ...............53 Intermediate aquifer system/in termediate confining unit...................................................................57 Floridan aquifer system.......................................................................................................................66 Middle Floridan confining unit................................................................................................. ..........75 Summary........................................................................................................................ .............................79 Refere nces..................................................................................................................... ..............................81 FIGURES Figure 1. Study area.......................................................................................................... ........................4 Figure 2. Geologic map of study area.......................................................................................... .............6 Figure 3. Structural feat ures within th e study area...................................................................................8 Figure 4. Environmental geology of the study area............................................................................. .....9 Figure 5. Shaded relief t opography of th e study area.............................................................................12 Figure 6. Geomorphology of the study area..................................................................................... ......13 Figure 7. Shaded topographic relief of the southern extent of th e Lake Wales Ridge...........................16 Figure 8. Generalized correlation between lithostratigraphic units and the surface of the FAS.............23 Figure 9. Explanation (legend for cross sections)............................................................................ .......25 Figure 10. Characteristic gamma-ray l og responses............................................................................. ....26 Figure 11. Helicostegina gyralis , a foraminifer common within the Oldsmar Formation.......................32 Figure 12. Selected diagnostic fossils co mmon within the Avon Park Formation...................................33 Figure 13. Selected diagnostic foss ils within the Ocala Limestone..........................................................35 Figure 14. Selected diagnostic Suwannee Limestone fossils.................................................................... 38 Figure 15. Diagnostic foramini fera in Hawthorn Group units..................................................................4 1 Figure 16. Assemblage of typical Bone Valley Member fossils...............................................................46 Figure 17. Characteristic Ft. Thompson Formation fossils..................................................................... ..51 Figure 18. Soil permeability of study area................................................................................................56 Figure 19. Statistical summary of SAS transmissivity data.................................................................... ..58 Figure 20. Statistical summary of SAS specific yield data..................................................................... ..58 Figure 21. Statistical summary of SAS horizontal hydraulic conductivity data.......................................59 Figure 22. Statistical summary of SAS vertical hydraulic conductivity data...........................................59 Figure 23. Approximate extent of IAS/ICU permeable zones..................................................................60 Figure 24. Statistical summary of IAS/ICU transmissivity data...............................................................6 3 Figure 25. Statistical summary of IAS/ICU storativity data................................................................... ..63 Figure 26. Statistical summa ry of IAS/ICU leakance data...................................................................... .64

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ix FIGURES (CONTINUED) Figure 27. Statistical summary of IAS/ICU horizontal hydraulic conductivity data................................64 Figure 28. Statistical summary of IAS/ ICU vertical hydraulic conductivity data....................................65 Figure 29. Statistical summary of IAS/ICU total porosity data................................................................ 65 Figure 30. Potentiometric surface of the Fl oridan aquifer system, September, 2005...............................68 Figure 31. Floridan aquifer system overburden thickness...................................................................... ..70 Figure 32. Thickness of the Upper Flor idan aquifer (includes non-potable)............................................71 Figure 33. Statistical summary of UFA transmissivity data.................................................................... .72 Figure 34. Statistical summa ry of UFA storativity data....................................................................... ....73 Figure 35. Statistical su mmary of UFA leakance data.......................................................................... ...73 Figure 36. Statistical summary of UFA horizontal hydraulic conductivity data......................................74 Figure 37. Statistical summary of UF A vertical hydraulic conductivity data..........................................74 Figure 38. Statistical summary of UFA total porosity data.................................................................... ..75 Figure 39. Interpretations of the MFCU in th e study area...................................................................... ..76 Figure 40. Statistical summary of MFCU vertical hydraulic conductivity data.......................................78 Figure 41. Statistical summary of MFCU total porosity data................................................................... 78 TABLES Table 1. Units mapped in this study. Map types are structure contour (surface) and isopach (thickness)..3 Table 2. Generalized correlation chart for units mapped within study area...............................................19 Table 3. Summary of krige inter polation statistics for each map...............................................................2 9 APPENDICES Appendix 1. Commentary on Florida h ydrostratigraphic nomenclature.....................................................99 Appendix 2. Explanation of revisions to FDEP-FG S Special Publication 28 aquifer definitions............101 PLATES 1. Cross section locations 2. Wells used in this study 3. Closed topographic depressions in the study area 4. Cross section: A-A’ Levy and Marion Counties 5. Cross section: B-B’ Levy and Marion Counties 6. Cross section: C-C’ Citrus and Sumter Counties 7. Cross section: D-D’ Citrus and Sumter Counties 8. Cross section: E-E’ Hernando, Sumter, and Lake Counties 9. Cross section: F-F’ Hernando, Pasco, Sumter and Lake Counties 10. Cross section: G-G’ Pasco, Sumter, and Polk Counties 11. Cross section: H-H’ Pasco and Polk Counties 12. Cross section: I-I’ Pinellas and Hillsborough Counties 13. Cross section: J-J’ Pinellas and Hillsborough Counties 14. Cross section: K-K’ Pinellas and Hillsborough Counties

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x PLATES (CONTINUED) 15. Cross section: L-L’ Manatee, Hillsborough, and Polk Counties 16. Cross section: M-M’ Manatee County 17. Cross section: N-N’ Sarasota and Manatee Counties 18. Cross section: O-O’ Sarasota County 19. Cross section: P-P’ Charlotte County 20. Cross section: Q-Q’ Polk and Osceola Counties 21. Cross section: R-R’ Hillsborough and Polk Counties 22. Cross section: S-S’ Hillsborough and Polk Counties 23. Cross section: T-T’ Manatee, Hardee, and Highlands Counties 24. Cross section: U-U’ Manatee, Hardee, and Highlands Counties 25. Cross section: V-V’ Manatee, DeSoto, Hardee, and Highlands Counties 26. Cross section: W-W’ Sarasota, DeSoto, and Highlands Counties 27. Cross section: X-X’ Sarasota, DeSoto, Highlands, and Glades Counties 28. Cross section: Y-Y’ Charlotte and Glades Counties 29. Cross section: Z-Z’ Levy, Citrus, Pasco, and Hernando Counties 30. Cross section: AA-AA’ Marion, Sumter, Hernando, and Pasco Counties 31. Cross section: BB-BB’ Pinellas County 32. Cross section: CC-CC’ Hillsborough and Manatee Counties 33. Cross section: DD-DD’ Hi llsborough and Manatee Counties 34. Cross section: EE-EE’ Lake, Polk, Hardee, DeSoto, and Charlotte Counties 35. Cross section: FF-FF’ Polk, Highlands, and Glades Counties 36. Cross section: GG-GG’ Manatee, Sarasota, and Charlotte Counties 37. Cross section: HH-HH’ Manatee, Sarasota, and Charlotte Counties 38. Avon Park Formation surface 39. Ocala Limestone surface 40. Ocala Limestone thickness 41. Suwannee Limestone surface 42. Suwannee Limestone thickness 43. Hawthorn Group surface 44. Hawthorn Group thickness 45. Arcadia Formation surface 46. Arcadia Formation thickness 47. Nocatee Member of the Arcadia Formation surface 48. Nocatee Member of the Arcadia Formation thickness 49. Tampa Member of the Arcadia Formation surface 50. Tampa Member of the Arcadia Formation thickness 51. Peace River Formation surface 52. Peace River Formation thickness 53. Bone Valley Member of the Peace River Formation surface 54. Bone Valley Member of the Peace River Formation thickness 55. Surficial aquifer system thickness 56. Intermediate aquifer system/intermediate confining unit surface 57. Intermediate aquifer system/intermediate confining unit thickness 58. Floridan aquifer system surface 59. Middle Floridan confining unit surface

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xi ABBREVIATIONS, ACRONYMS AND CONVERSIONS ASE average standard error BLS below land surface CFHUD II Second Ad Hoc Committee on Florid a Hydrostratigraphic Unit Definitions CTD closed topographic depression DEM digital elevation model District Southwest Florida Water Management District FAS Floridan aquifer system FDCA Florida Department of Community Affairs FDEP Florida Department of Environmental Protection FGS Florida Geological Survey IAS/ICU intermediate aquifer sy stem/intermediate confining unit IDW inverse distance weighted IP/FMNH Invertebrate Paleontology, Florida Museum of Natural History Kh horizontal hydraulic conductivity Kv vertical hydraulic conductivity L leakance LFA Lower Floridan aquifer LIDAR light detection and ranging MFCU Middle Floridan confining unit MSL mean sea level RMS root mean squared ROMP Regional Observation and Monitor Well Program S storativity SAS surficial aquifer system SWFWMD Southwest Florida Water Management District SY specific yield T transmissivity UFA Upper Floridan aquifer USGS United States Geological Survey ~ approximately gamma Multiply By To obtain cubic foot (ft3) 0.0283 cubic meter (m3) foot (ft) 0.305 meter (m) foot per day (ft/d) 3.53x10-4 centimeter/second (cm/s) foot squared per day (ft2/d) 0.0929 meter squared per day (m2/d) gallon (gal) 3.79x10-3 cubic meter (m3) gallon (gal) 3.79 liter (L) gallon per minute (gal/min) 6.32x10-5 cubic meter per second (m3/s) inch (in) 25.4 millimeter (mm) mile (mi) 1.609 kilometer (km)

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xii ACKNOWLEDGEMENTS This research was a cooperative effort between th e Florida Department of Environmental Protection (FDEP) Florida Geological Survey (FGS) and th e Southwest Florida Water Management District (SWFWMD). Special thanks are extended to Davi d L. Moore, SWFWMD Executive Director and Dr. Walter Schmidt, FDEP-FGS Director and State Geologi st for administrative and financial support. Essential geology and hydrogeology data-collection programs in the SWFWMD, FDEP-FGS and the U.S. Geological Survey (USGS) have made the development of this comprehensive report possible. Numerous individuals and countless hours of well drilling and logging, aquifer and laboratory testing, database development and management, lithologic descripti ons, formation boundary determinations, surface modeling, and map/cross section production have cont ributed to the development of this report. The authors express their appreciation to the numerous individuals for their insightful review of the manuscript and plates. From the FDEP-FGS, these i ndividuals include Carol Armstrong, Ken Campbell, Jackie Lloyd, Frank Rupert, Dr. Walter Schmidt, Dr. Tom Scott; from SWFWMD, Ron Basso, Michael Beach, Marty Clausen, Michael Gates, Tony Gilboy, Jason LaRoche, John Parker, Robert Peterson and Donald Thompson. Ken Campbell and Dr. Tom Scott are thanked for their contributions and discussions regarding the lithostratigraphy and hydr ostratigraphy of the study area. Discussions with John J. Hickey, Rick Spechler, Dr. Tom Scott and Dr. Sam Upc hurch helped refine our understanding of the hydrostratigraphy of the region. Doug Rapphun also contributed to our knowledge of the hydrogeology in the region. The authors also gratefully acknowledge those staff of the FDEP-FGS who participated in this project. Lance Johnson and Paula Polson provided assistance with cross-section development. Surface interpolations during early phases of the project were completed by Bill Pollock, Amy Graves, John Marquez and Andrew Rudin. Developers of the data base for this project included Mark Groszos, Marco Cristofari and Rob Stoner. Data management suppor t included the assistance of Jackie Bone, Patricia Casey, Lance Johnson, Natalie Sudman , and Holly Tulpin. Lithologic descriptions of numerous borehole samples were completed by Alan Baker, Jim Cichon, Erin Dorn, Kris Esterson, Mabry Gaboardi, Diedre Lloyd, Matt Mayo, Sarah Ramdeen and Holly Williams. Many of the photos and photomicrographs of fossils presented in this report are provided courtesy of Roger Portell and Sean Roberts (Invertebrate Paleontology, Florida Museum of Natural History) , Dr. Jonathan Bryan (Okaloosa-Walton Community College) and Frank Rupert. Dr. Rick Copeland w as helpful with regard to discussions of quality assurance of hydrogeologic data and presentation of descriptive statistics.

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BULLETIN NO. 68 1 HYDROGEOLOGIC FRAMEWORK OF THE SOUTHWEST FLORIDA WATER MANA GEMENT DISTRICT By Jonathan D. Arthur, (P.G. #1149), Cindy Fischler (P.G. #2512), Clint Kromhout (P.G. #2522), James M. Clayton, (P.G. #381), G. Michael Kelley (P.G. #249), Richard A. Lee (P.G. #956), Li Li, Mike O'Sullivan (P.G. #2468), Richard C. Green (P.G. #1776), and Christopher L. Werner (P.G. #2366) INTRODUCTION Background Groundwater comprises approximately 85 percent of the total water-resource supply in the Southwest Florida Water Management District (SWFWMD), where existing water demands are on the order of 435 billion gallons per year (Southwest Florida Water Management District, 2006a). By 2025, the population of the region is expected to increase more than 30 percent, placing further demands on water resources. Development of alternative water supplies and continued water-resource management and conservation are critically important toward the sustainability of groundwater resources within the aquifer systems of southwest Florida. These practices, however, require the accumulation, management and interpretation of hydrogeological data. In the mid-1990’s, the SWFWMD and the Florida Department of Environmental Protection Florida Geological Survey (FDEP-FGS) entered into a cooperative project to develop a series of geologic and hydrogeologic cross sections throughout the 16-county SWFWMD region. The project was designed to characterize the relation and extent of lithostratigraphic1 and 1 Lithostratigraphic units are laterally extensive sequences of rocks and sediments reflecting unique lithologic characteristics; each unit was deposited within a generally similar paleo-environment during a given period of time in Earth’s history. hydrostratigraphic2 units within the region with an emphasis on use of hydrogeologic data collected by the District’s Regional Observation and Monitor-well Program (ROMP). This project was later expanded to include production of surface and thickness maps of the units represented in the cross sections. To accomplish the goal of the regional cross section project, the District was divided into four study areas (three project phases): Phase IA includes Pinellas and Hillsborough Counties; Phase IB includes Manatee, Sarasota, Hardee, DeSoto and Charlotte Counties; Phase II includes the northern part of the District, from Levy, Marion and Lake to Pasc o Counties; and Phase III includes the southeastern part of the District, encompassing all areas not covered in Phases IA, IB and II. Interim reports were published for Phase IA and II (Green et al., 1995 and Arthur et al., 2001a, respectively). Rather than separately publishing reports for the remaining phases, the cross sections are incorporated in this report. Purpose and Scope The purpose of this study is to refine the hydrogeological framework of the region to facilitate science-base d decision making with regard to the protection, conservation and management of southwest Florida’s water 2 Hydrostratigraphic units include laterally extensive sequences of rocks and sediments that are related by hydrogeologic characteristics. Hydrostratigraphic units may or may not correlate with lithostratigraphic units.

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FLORIDA GEOLOGICAL SURVEY 2 resources. Thirty-four cross sections have been produced for this study (Plate 1). Each of the cross sections illustrates regional lithostratigraphy of Eocene through Pliocene formations, lithology, mineralogy, gamma-ray logs, topographic profiles and hydrostratigraphic delineations. Although most of the data used to construct the cross sections was taken from wells drilled as part of ROMP (Gomberg, 1975), borehole data (e.g., from cores, cuttings and geophysical logs) from the FDEP-FGS and the U.S. Geological Survey (USGS) were utilized to fill in as many gaps as possible. The mapping phase of the study facilitated development of a new geologic and hydrogeologic database, FGS_Wells. Structure contour (surface elevations) and isopach (thickness) maps for all regionally extensive lithostratigraphic and hydrostratigraphic units within the District were then developed. The maps include all units between land surface and the top of the Middle Floridan confining unit (Table 1). Data from more than 1050 wells (including offshore boreholes) serve as control for these maps (Plate 2). In addition, synthetic wells were used to provide lateral (edge) control during map surface interpolation. These wells represent an artificial stratigraphic record for a given location based on interpolated elevations from existing maps or cross sections. The new surface and thickness maps presented herein were developed using the ESRI geographic information system (GIS) program ArcMAP (see Map Development and Data Management, p. 24) for details on map production. Each map includes the lateral extent of each unit and locations of wells within the study area that were used to interpolate surfaces and thicknesses. Study Area Maps and cross sections produced for this study cover the entire SWFWMD region (Figure 1). To facilitate present and future hydrologic modeling and comparison of these maps to adjacent Water Management Districts, a 10 mi (16.1 km) wide buffer extending beyond the District boundary was included in the study area (Figure 1, Plate 2). Surface interpolation techniques, such as kriging, can produce nonrepresentative contours along the margins of mapped units. To address these undesirable “edge effects,” data fro m within a second 10 mi (16.1 km) wide buffer zone was utilized. The additional data helped stabilize surface interpolations and contours, and allowed for a more accurate delineation of the vertical and lateral extents of certain mapped units. The project study area, which covers approximately 14,340 mi2 (37,141 km2), does not include wells within the second (outermost) buffer. Previous Investigations Numerous researchers have focused on the regional geology and hydrogeology of southwest Florida. Sub-Floridan aquifer system geology, with an emphasis on pre-Cenozoic basement geology, is presented in several papers including Applin (1951), Applin and Applin (1965), Bass (1969), Barnett (1975), Smith (1982) and Chowns and Williams (1983). Arthur (1988) and Heatherington and Mueller (1997) focus on geochemistry of basement terrains, while Smith and Lord (1997) summarize the tectonic and geophysical aspects of the Florida basement. Gohn (1988) and Rand azzo (1997) provide comprehensive overviews of Mesozoic and Cenozoic geology of the Atlantic Coastal Plain, including peninsular Florida. Mesozoic and Cenozoic paleoceanographic and structural evolution along the margin of the Florida peninsula is presented in Hine (1997). Selected early studies of Cenozoic and younger formations include Applin and Applin (1944), Cooke (1945), Puri and Vernon, (1964) and Chen (1965). More recent stratigraphic research on units in south and southwest Florida has been completed by Miller (1986), Scott (1988), McCarten et al. (1995), BrewsterWingard et al. (1997) and Cunningham et al. (1998). Missimer (2002) focused on Oligocene through Pliocene stratigraphic relationships in the southernmost part of the present study area (Charlotte County), as well as Lee and western Collier Counties. Pliocene and younger stratigraphy has been the fo cus of several studies

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BULLETIN NO. 68 3 Table 1. Units mapped in this study. Map typ es are structure contour (SC) and isopach (I). Lithostratigraphic Units Map types Hydrostratigraphic Units Map types Hawthorn Group SC, I surficial aquifer system I Peace River Formation SC, I intermediate aquifer system / intermediate confining unit SC, I Bone Valley Member SC, I Floridan aquifer system overburden I Arcadia Formation SC, I Floridan aquifer system SC Tampa Member SC, I Upper-Floridan aquifer system I Nocatee Member SC, I Middle Floridan confining unit SC Suwannee Limestone SC, I Ocala Limestone SC, I Avon Park Formation SC (e.g.,Evans and Hine, 1991; Scott, 1997; Missimer, 2001). Hydrogeologic framework studies that include the southwestern Florida region include Gilboy (1985), Johnston and Bush (1988), Miller (1986), Ryder (1985) and Reese and Richardson (2008). Maps depicting the thickness and extent of the Floridan aquifer system (FAS), the “intermediate aquifer” and intermediate “confining beds” include Buono and Rutledge (1978), Wolansky et al. (1979a), Wolansky et al. (1979b), Wolansky and Garbode (1981), Corral and Wolansky (1984) and Miller (1986). Allison et al. (1995) present a map of the top of rock of the FAS in the Suwannee River region, located along the northeast part of the SWFWMD study area. Meyer (1989) provides a comprehensive characterization of the hydrogeologic framework of southern Florida. Spechler and Kroening (2007) present a comprehensive study of Polk County hydrology. Reese (2000) and Missimer and Martin (2001) present the hydrogeology and water quality of the FAS in Lee, Hendry and Collier Counties. Statewide hydrochemical characterizations of the upper FAS have focused on aquifer-system mineralogy and processes that led to observed native groundwater chemistry (e.g., Plummer, 1977; Sprinkle, 1989), and hydrochemical facies (Katz, 1992). Upchurch (1992) characterized not only hydrochemical facies , but also naturally occurring and anthropogenic constituents in the FAS. Other studies that focused on regional aspects of FAS hydroche mistry (i.e., salinity, solute transport and dolo mitization) include Back and Hanshaw (1970), Cander (1994, 1995), Hanshaw and Back (1972), Jones et al. (1993), Maliva et al. (2002), Randazzo and Zachos (1984), Sacks (1996), Sacks and Tihansky (1996), Steinkampf (1982), Swancar and Hutchinson (1995), Trommer (1993), and Wicks and Herman (1994, 1996). Budd et al. (1993), Budd (2001, 2002) and Budd and Vacher (2004) have studied in detail the role of permeability, compaction and cementation in FAS carbonates of southwest Florida. An overview of surfacewater and groundwater hydrology is provided by Wheeler et al. (1998). In contrast to these regional characterizations, Tihans ky (2005) identified the complex relation between water quality, groundwater flow patterns and structural heterogeneity within the FAS in northeastern Pinellas County by employing diverse hydrogeological and geophysical analyses. Hydrochemical studies of the intermediate aquifer system/intermediate confining unit

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FLORIDA GEOLOGICAL SURVEY 4 75 75 301 98 441 19 98 41 27 441 41 17 98 27 The Villages Trenton Cross City Inglis Avon Park New Port Richey Dade City LAKEM A R I O N 75 4 95 275 175 27 19 1 17 98 192 301 92 41 441 19A 27 129 41 98 301 Tampa Ocala Bartow Arcadia Sebring Orlando Tavares Sanford Deltona De Land Bronson Bunnell Palatka La Belle Sarasota Wauchula Lakeland Bushnell Bradenton Kissimmee Inverness Cape Coral Fort Myers Okeechobee Clearwater Titusville Punta Gorda Moore Haven Brooksville Gainesville Daytona Beach St. Petersburg POLK LAKEM A R I O NOSCEOLA HENDRYV O L U S I AD IX I EGLADES ORANGE PASCOA L A C H U AP U T N A MH I G H L A N D SBR E V A R DCITRUSMANATEE HARDEE DESOTOS U M T E RHILLSBOROUGH OKEECHOBEEF L A G L E RSARASOTA CHARLOTTE HERNANDO INDIAN RIVER SEMINOLEGILCHRISTP I N E L L A SB R E V A RDLEE FLAGLER ST . JOHNS ST. JOHNS LEVYGulf of MexicoPeace RiverM aya kka Ri v e rM a nat e e RiverL i t t l e M a n atee RiverA l a fia RiverH i l lsb o rou gh R iv e rAncl o te R iverW i t hla c ooc hee R iv e rWit hla coochee RiverWaccasassa R iverFi shea t ing CreekCa l o o sah atchee R i verAr buckl e CreekK iss immeeRi verEconlo c kha tch ee Ri v e rSt . Johns R ive rSt . Joh ns R iverOklaw ah a Ri v e rP a lat a kaha R i v e rSuwan nee R ive rT o m oka R ive rLake OkeechobeeL a k e Ge o r g e F L T u r n p i k eF L T u r n p i k e Enlarged Area Explanation Study Area Cities Rivers Lakes Water Management Districts US Interstate FL Turnpike US Highway Study Area 010203040 5 KilometersProjection: Custom FDEP Albers 010203040 5 Miles1:1,750,000Scale Figure 1. Study area.

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BULLETIN NO. 68 5 include Joyner and Sutcliff (1976), Upchurch (1992), Kauffman and He rman (1993), Broska and Knochenmus (1996) and Torres et al. (2001). Knochenmus (2006) characterizes the water quality and hydraulic heterogeneity of the intermediate aquifer system in the southern part of the District. The study underscores that previously defined “permeable zones” of this aquifer system are hydraulically similar to “semi-confining units” in the upper Floridan Aquifer System. A statewide hydrochemical assessment of the surficial aquifer system was completed by Upchurch (1992). Several groundwater flow models of the SWFWMD region have been published (e.g., Ryder, 1985; Barcelo and Basso, 1993; Yobbi, 1996), most of which are discussed in the comprehensive work of Sepulveda (2002), wherein he developed a groundwater flow model for peninsular Florida that includes the Intermediate and Floridan aquifer systems. Selected compilations of aquifer parameters on which many of these models are based are presented in Hydrogeological Properties , p. 52. Physical Setting Geology Development of the Florida carbonate platform primarily occurred during the Late Cretaceous through middle Cenozoic and was generally free of intermixed sands and clays. Strong currents across northern Florida in a feature broadly referred to as the Georgia Channel System (Huddlestun, 1993) effectively precluded transport and deposition of these siliciclastics to the platform. During this period, deposition of the Cedar Keys Formation, Oldsmar Formation, Avon Park Formation, Ocala Limestone, and the Suwannee Limestone occurred. Huddleston (1993) proposed the Georgia Channel System recognizing spatially and temporally overlapping features (e.g., Suwannee Strait and Gulf Trough) proposed in the literature that described paleotopography (paleobathymetry) and associated paleocurrents. Randazzo (1997) provides an overview of this dynamic system and feature names. During the Oligocene, the southern Appalachians experienced uplift and erosion (Scott, 1988). Southward transport and deposition of ensuing siliciclastic sediments began to fill the channel system, which allowed ocean currents to transport sediments southward across the well-developed carbonate platform. As a result, some of the first siliciclastic sediments in southern Florida carbonates appear as sand lenses in the Lower Oligocene Suwannee Limestone south of Charlotte County (Missimer, 2002). The influx of siliciclastic sediments, mixing with locally-formed carbonates led to Late Oligocene through the Early Pliocene deposition of the Hawthorn Group (Scott, 1988; Missimer et al., 1994) throughout most of Florida. In much of peninsular Florida phosphate deposition occurred yielding many economic phosphorite deposits. This period of phosphogenesis is described by Riggs (1979a, 1979b) and Compton et al. (1993); [see Bone Valley Member, p. 48, for more detail]. During the Late Pliocene to Recent, sediment deposition became even more siliciclastic dominant. Shell beds were deposited along coastal areas and migrated in response to sea-level fluctuations. The geology and depositional environment of lithostratigraphic units in the region are the subject of numerous studies in southwestern Florida; results of which are presented in the Lithostratigraphy section, p. 30, of this report. From deposition of the Cedar Keys Formation through Pliocene-Pleistocene shell beds, a dynamic transition from carbonate to siliciclastic-dominated depositional environments is reflected. The surface distribution of lithostratigraphic units (Figure 2) in the study area is a function of post-depositional influences ranging from tectonic activity, platform stability, sea-level changes and karst processes. For example, the Avon Park Formation is the oldest exposed lithostratigraphic unit in the study area (Figure 2). This Eocene unit gently dips southward toward Charlotte County to depths exceeding 1500 ft (457.2 m) below land surface (BLS). In

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FLORIDA GEOLOGICAL SURVEY 6 TQsu To Qu Tc TQuc Qu Qbd Qbd Qu Thc Qu Thpb Qh Qh Thp Th TQsu Qu Th Tc Th Qh TQu Tc Qbd Qbd Ts That TQu Tc Qh Tc Thp Tc Qu TQuc Thp Th Tha TQsu TQsu Thc Qu Tc Thc Qu Thc TQd Qh TQu Tap Qbd TQd TQd Qu TQu Qu Tc Qh Qu TQu Qu Qa Th Qu Qu Qu TQd Tap Tap Qu Qu Qh Qu Qh Thc Thc That Tc TQd Qh That Qa Qu Thpb Q b Qh Qh Tha Qh Qu Th Qh Tap TQd Qu Qa Qbd Qu TQu Ts That Qh Tha TQsu Qbd Qu Qh Qu Th Qbd Qh Thc Qh That Tc Th Qh Qh That Qh Qh TQsu Qu Qh To Qh Qh Qh Thp Ts Q T Q To Qh Ts Qh Qh Qh Qh Tt Thp Qu TQsu TQsu Qa That TQsu Qh Qh TQsu Gulf of Mexico Explanation Study Area Water Management Districts(undifferentiated)Stratigraphic Units Shelly Plio-Pleistocene Sediments Qbd: Beach Ridge and Dune Qh: Holocene Sediments Qu: Undifferentiated Sediments TQd: Dunes TQsu: TQu: Undifferentiated Sediments TQuc: Reworked Cypresshead Sediments Tap: Avon Park Formation Tc: Cypresshead Formation Th: Hawthorn Group Tha: Hawthorn Group, Arcadia Formation That: Hawthorn Group, Arcadia Formation, Tampa Member Thc: Hawthorn Group, Coosawhatchie Formation Thp: Hawthorn Group, Peace River Formation Thpb: Hawthorn Group, Peace River Formation, Bone Valley Member To: Ocala Limestone Ts: Suwannee Limestone Tt: Tamiami Formation Geologic MapProjection: Custom FDEP Albers Scale 1:1,750,000 0102030 5Kilometers 010203040 5 Miles Figure 2. Geologic map of study area (from Sc ott et al., 2001) depicting the uppermost mappable units within 20 ft (6.1 m) of land surface.

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BULLETIN NO. 68 7 general, the younger form ations follow this pattern, however, many are not observed throughout the full extent of the study area (i.e., absence of the Peace River Formation [Hawthorn Group] in the northern third of the District). In the sections that follow, details of the features and processes affecting the overall geologic framework are discussed. Structure Numerous structural features affect the thickness and extent of geologic units in the study area (Figure 3). The oldest known “basement” feature in the region is the Bahamas Fracture Zone (Klitgord et al., 1983), which is also referred to as the Jay Fault (Pindell, 1985). This zone bisects the Florida peninsula basement from Tampa Bay southeast to the Lake Worth area on the east coast. Lithologic and geophysical data suggest that this basement feature represents an Early Mesozoic transform fault that was important to the development of the Gulf of Mexico. Christenson (1990), however, suggests that based on assessment of more recently acquired borehole geology and magnetic anomaly data, the feature represents a Triassic-Jurassic extensional rift margin with little to no lateral offset. He proposes the name “Florida Lineament” to describe this feature, which coincides with the Jay Fault and the Bahamas Fracture Zone across peninsular Florida (Christenson, 1990; see feature “A” in Figure 3). The South Florida Basin (Applin and Applin, 1965; Winston, 1971) is a stratigraphic basin that contributed to southward thickening of Mesozoic and Early Cenozoic lithostratigraphic units in the southern Florida peninsula (Figure 3). A possible successor basin, the younger Okeechobee Basin (Riggs, 1979a) may have contributed to south southeastward dipping of Oligocene and older lithostratigraphic units along the eastern margin of the study area (Highlands and Glades Counties). The influence of “basement” structures on Cenozoic and younger stratigraphic units is poorly understood. For example, an apparent southeast plunging syncline (“B” in Figure 3) trends from Sarasota to Hendry Counties in the “sub-Zuni” (i.e., pre-Middle Jurassic) map presented in Barnett (1975). Shallower northwest-striking faults reported by Winston (1996) occur in the same region. Maps of the structural surface of Eocene rocks (Miller, 1986) indicate a generally south-plunging trough extending from central Charlotte County. Deepening and thickening of units in the Charlotte County region are observed in the present study (see Lithostratigraphy , p. 30). The Early Cretaceous “Broward Syncline” (Applin and Appin, 1965; “C” in Figure 3) is located approximately 20 mi (32 km) to the east of feature “B” and has a generally parallel strike. These inferred faults and basement relationships warrant further study, especially given their potential role in water quality and distribution of permeable zones. Knowledge of the distribution of low-permeability sediments beneath the FAS is also important as potential sites for CO2 sequestration are explored. The Ocala Platform (“D” in Figure 3) is the most dominant feature in the central peninsular region. Evidence of this platform is apparent in the geologic map (Figure 2) where the Eocene Avon Park Formation (Tap) and Ocala Limestone (To) are exposed at or near land surface. This feature is also evident in the Environmental Geology composite map (Figure 4), which reflects lithologic and sediment types within 10 ft (3.1 m) of land surface. Shallow or exposed carbonate rocks in Levy, Marion, Citrus and Sumter Counties reflect the influence of the platform. This structure is not thought to be an uplift (Winston, 1976) but rather a tectonically stable area on which disconformable marine sedimentation and differential subsidence has occurred (Scott, 2001). It is also a major controlling factor in the thickness and extent of lithostratigraphic units in central and southwestern Florida. As a result, this feature also has a very significant effect on the distribution of regional aquifer systems. Remaining structural features are discussed in this section from north to south. Several northwest-trending faults, as well as orthogonal fracture traces (or lineaments), have been proposed within the Levy and Citrus County area by Vernon (1951). It is possible that some

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FLORIDA GEOLOGICAL SURVEY 8 Gulf of Mexico FG-1 FG-2 A B CU DU DD U E D F M M S o u th F l o rid a Bas i nProposed Faults Winston, 1996 Hutchinson, 1991 Miller, 1986 Pride et al., 1966 Carr and Alverson, 1959 Vernon, 1951Explanation Study Area Fault Groups Plunging syncline Plunging anticline F MOkeechobee Basin Sproul et al., 1972 Structural FeaturesProjection: Custom FDEP Albers Scale 1:1,750,000 010203040 5 Miles 010203040 5 Kilometers Christenson, 1990 Present Study (inferred) Figure 3. Structural features within the study area. A Florida Lineament; B pre-middle Jurassic plunging syncline inferred from Barnett’s (1975) “sub-Zuni” map; C - “Broward Syncline;” D Ocala Platform; E – Kissimmee Faulted Flexure; FG-1 fault group along strike with fault inferred in present study; FG-2 gro up of reported faults possibly affecting subcrop extent of the Ocala Limestone. U/D – upthrown/downthrown block.

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BULLETIN NO. 68 9 Gulf of MexicoExplanation Study Area Water Management DistrictsEnvironmental GeologyRock/Sediment Type Clayey Sand Dolostone Limestone Limestone/Dolostone Med. Fine Sand and Silt Peat Sandy Clay and Clay Shelly Sand and Clay Lake Okeechobee Environmental GeologyProjection: Custom FDEP Albers Scale1:1,750,000 010203040 5 Miles 010203040 5 Kilometers Figure 4. Environmental Geology of the study area (after Knapp, 1978; Scott, 1978; Scott, 1979; Lane, 1980; Lane et al., 1980; Knapp, 1980; Deuerlin g, 1981). Lithotypes depicted in this map are reported to occur less than or equal to 10 ft (3.0 m) from land surface.

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FLORIDA GEOLOGICAL SURVEY 10 of the inferred “offsets” in his study are due to wells having encountered buried karst pinnacles and paleo-sinks. Carr and Alverson (1959), Pride et al. (1966), and Vernon (1951) report a northwest trending normal fault(s) in northwestern Polk County (fault group “FG-1”, Figure 3). Pride et al. (1966) suggest that the fault affects not only the Avon Park Formation, but also juxtaposes the Suwannee Limestone and Ocala Limestone. Carr and Alverson (1959) indicate that the fault penetrates Hawthorn Group sediments as well. Both studies report the northeast block of the inferred fault as the upthrown side. In the present study, evidence supports two possible northwest-trending faults along the northeastern extent of the Suwannee Limestone (Figure 3; see also Suwannee Limestone , p. 37). Both faults are similar in strike and offset direction (polarity) to fault group “FG-1” in Figure 3. One of the offsets proposed herein is a northwestern extension of a fault proposed by Carr and Alverson (1959). Faults affecting Middle and Upper Eocene (e.g., Avon Park Formation and Ocala Limestone) strata are proposed along the PolkOsceola County boundary (Pride et al., 1966; Miller, 1986). The Kissimmee Faulted Flexure (Vernon, 1951; “E” in Figure 3) occurs in the same area and was originally considered a wedge-shaped, fault-bounded block that had been tilted and rotated, with beds containing small folds and structural irregularities. Wells that penetrate the feature contain variably thick Pliocene-Miocene sediments that overly the Avon Park Formation. Scott (1988) and Davis et al., (2001) consider the Kissimmee Faulted Flexure to be an Avon Park Formation stratigraphic high with the Ocala Limestone and Hawthorn Group sediments locally absent due to erosion. Additional faults (“FG-2” in Figure 3) affecting the subcrop extent of the Ocala Limestone along the western margin of the Flexure have also been proposed. Data presented in this study support the interpretations of Scott (1988) and Davis et al., (2001). Further to the south in the vicinity of Charlotte Harbor, a west-northwest trending reverse fault penetrating a dolostone layer in the Suwannee Limestone is proposed (Hutchinson, 1991). Maps presented herein do not lend support to the inferred reverse fault. In the same area, a series of northeast-trending lineaments along the northern margin of Charlotte Harbor (Michael Fies, personal communication, 2007) coincide with anomalously high groundwater temperatures in the upper FAS (Smith and Griffin, 1977) suggesting a potential line of further investigation (E. Richardson, written communication, May, 2006). The “North Port Fault” (Winston, 1996) strikes nearly coastparallel (northwest) across North Port and Punta Gorda. Winston (1996) suggests that the downthrown side may occur on the southwest block, which more or less coincides with thickening and deepening of several units mapped in the present study (see Lithostratigraphy , p. 30, for further discussion). South of the study area, west-northwest trending normal and reverse faults offsetting Miocene Hawthorn Group sediments on the order of 50 to 100 ft (15 to 30.5 m; vertical) are reported (Sproul et al., 1972). Evidence of some degree of vertical offset is present within cores in the study area; however, there is insufficient proximal well control to delineate faulting. Core from W-16913 (ROMP 5), for example, contains abundant high-angle fractures and slickensides that make some lithostratigraphic unit surfaces obscure. Regarding hydrostratigraphic units, brecciated and fractured zones in core from W-17392 (ROMP 13) contribute to difficulties correlating the Middle Floridan confining unit. These are only two of many examples of fractured intervals encountered during data collection that warrant further structural study. Small irregular surfaces in Miocene and older lithostratigraphic units in th e southern part of the study area raise many questions regarding the prevalence of structural deformation within Florida’s relatively young carbonate platform. Missimer and Maliva (2004) suggest that observed disturbances in lithostratigraphic surfaces throughout Florida are due to “differential subsidence by tensional basement displacement.” Their conclusions are based on seismic surveys and borehole data attained from areas of variable formation depths. Charlotte and Lee Counties are among the most widely

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BULLETIN NO. 68 11 studied of these areas. Seismic surveys reveal variations in depth to fo rmations (i.e., relief of unit surface) between ~130 to ~230 ft (39.6 m to 70.1 m) (Missimer and Gardner, 1976). Other seismic profiles in the region also suggest deformation (Evans a nd Hine, 1991; Lewelling et al., 1998). Missimer and Maliva (2004) propose that these deformed surfaces, some of which extend more than a mile across, are tectonically induced folds. On the other hand, Wolansky et al. (1983), Evans and Hine (1991), Lewelling et al. (1998) and Cunningham et al. (2001) prefer the hypothesis that observed perturbations in seismic reflectors are the result of karstic processes rather than structurally or tectonically related deformation. Geomorphology The topography (Figure 5) and geomorphology (Figure 6) of Florida have been influenced by interactions of sea-level changes, karst processes and subtle tectonic forces (Rupert and Arthur, 1990; Schmidt, 1997). The rate of Florida’s carbonate platform deposition was controlled by sea-level cycles and stand durations, which produced different physiographic features (e.g., Healy, 1975; Randazzo, 1997). Prominent ridges formed in shallow-water marine environments during sea-level high stands. Paleowater bodies, embayments, swales, relict coastal features and streams control where many present-day streams and lakes are located (White, 1970, Randazzo., 1997). Orthogonal patterns in modern drainage systems within the southern part of the study area may have been influenced by fractures (Lewelling et al., 1998) formed in response to peripheral Miocene-Pliocene stress fields associated with Caribb ean tectonics (Missimer and Maliva, 2004). Physiographic Provinces and Features Aerially extensive and distinctive physiographic provinces in the study area are summarized in this section, starting with the coastal zone and working inland (Figure 6). The coastline along the SWFWMD has been classified into two zones (Tanner, 1960a, 1960b): 1) north of Pasco County the coastal zone is dominated by swamps, salt marshes, oyster reefs and drowned karst topography and 2) south of Pasco County, depositional marine environments contributed to the formation of barrier beaches, barrier islands, barrier spits and over-wash fans. The Gulf Coastal Lowlands (White, 1970) include the western extent of the SWFWMD, ranging in width from less than 2 mi to approximately 45 mi (3.2 km to ~72 km). Elevations range from sea-level to approximately 100 ft ( 30.5 m) above mean sea level (MSL). Diverse ecosystems are present within the Gulf Coastal Lowlands including pine flatwoods, dry prairies and to a lesser extent, swamps, scrub and high pine and salt marshes (Crumpacker, 1992). The Gulf Coastal Lowlands do not coincide with any mappable marine terrace and are generally characterized by wide, flat marine karstic plains, including paleo-dunes (White, 1970). Significant updates and revisions to Florida’s geomorphic nomenclature are ongoing, with an emphasis on geologic processes and framework geology (Scott, 2004). Re-classification of the Gulf Coastal Lowlands into the Chiefland Karst Plain, Crystal River Karst Plain, and the Land O’ Lakes Karst Plain is proposed (Scott, 2004). The Brooksville Ridge is a prominent upland east of the Gulf Coastal Lowlands, striking north-northwest discontinuously from Pasco to Levy Counties. The total length is approximately 110 mi (177 km) including the inter-ridge Dunellon Gap (Figure 6). The Ridge varies in width from approximately 4 to 10 mi (6.4 to 16.1 km) (White, 1970). Elevations along this upland range from approximately 70 to ~300 ft (21.3 to 91.4 m) above MSL. Finegrained, low-permeability sediments within the Brooksville Ridge, particularly Hawthorn Group clays, reduce relative infiltration rates and provide a chemical buffer that inhibits carbonate dissolution. Areas without thick clay-rich siliciclastic deposits, thro ugh geologic time, are more vulnerable to a reduction in land surface elevation. This process, known as topographic

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FLORIDA GEOLOGICAL SURVEY 12 Gulf of MexicoExplanation Study Area Water Management DistrictsElevation 310 ft 0 ft 155 ft TopographyProjection: Custom FDEP Albers Scale 1:1,750,000 010203040 5 Miles 010203040 5 Kilometers Figure 5. Shaded relief topography of the study area based on 15 m (49 ft) resolution digital elevation model DEM (digital elevatio n model) (Arthur et al., in review).

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BULLETIN NO. 68 13 Zephyrhills Gap Lake Harris Cross Valley Manatee Fanning Kings Bay Homosassa Chassahowitska Weeki Wachee Rainbow Silver Silver Glen Alexander Volusia Blue W e s t e r n Va l l e yW e s t e r n V a l l e yWinter Haven RidgeTs a l a A p opk a P l a i nSumter Upland Polk UplandO s c e o l a P l a i nO k e e c h o b e e P l a i n Ocala Hill Northern Highlands Mount Dora RidgeL a k e l a n d R i d g eL a k e W a l e s Ri d g eL a k e U p l a n dL a k e H e n r y R i d g eI n t r a r i d ge V a l l e yFairfield HillsG u l f C o a s ta l L ow l a n dsG ul f C o as t a l L o w l a n d sG u l f C o a s t a l L o w l a n d sDunellon GapDesoto PlainCotton Plant Ridge Coastal SwampsC e n t r a l V a l l e yC en t r a l V a l l e yCaloosahatchee Valley Caloosahatchee Incline Caloosahatchee InclineB r o o k s v i l l e R i d g eB ro o k svi l l e R i d g e Bombing Range Ridge Alachua Lake Cross ValleyGulf of Mexico Explanation Study Area Water Management Districts Springs (1st Magnitude) Springs Geomorphology Geomorphology 010203040 5 Kilometers1:1,750,000ScaleProjection: Custom FDEP Albers 010203040 5 Miles Figure 6. Geomorphology of the study area (from White, 1970 and Puri and Vernon 1964). Spring locations from Scott et al. (2004).

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FLORIDA GEOLOGICAL SURVEY 14 inversion, is thought to have been an important factor in the origin of the Brooksville Ridge (White, 1970; Knapp, 1977). Karst features are abundant along the axis of the Brooksville Ridge. These features are generally internally drained and locally breach the low-permeability sediments in the subsurface and serve as focal points of aquifer recharge. Ecosystems present within the Brooksville Ridge area include scrub and high pine, temperate hardwood forests (with less extensive swamps), pine flatwoods, and dry prairies (Crumpacker, 1992). The Western Valley is located east of the Brooksville Ridge and Tsala Apopka Plain and west of the Sumter and Lake Uplands (Figure 6). It is also bound to the north by the Northern Highlands and the Polk Upland to the south. The Western Valley is approximately 140 mi (225 km) long and between 5 and 15 mi (8.0 to 24.1 km) wide; elevations average approximately 40 ft (12.2 m) MSL and range up to 100 ft (30.5 m) MSL. Ecosystems present in the Western Valley include temperate hardwood forest (to the north), scrub and high pine, minor swamps, pine flatwoods and dry prairies (Crumpacker, 1992). The Western Valley is characterized by its gently rolling limestone karst plains containing a veneer of Pleistocene sediments overlying Eocene carbonates (Rupert and Arthur, 1990). The Tsala Apopka Plain is believed to be a relict feature of a larger paleolake (White, 1970). Scott (2004) proposes reclassification of the Western Valley into the Williston Karst Plain and Green Swamp Karst Plain. The Polk and Lake Uplands, located between the Gulf Coastal Lowlands and the Lake Wales Ridge are approximately 100 mi (161 km) in length and range in elevation from 80 ft (24.4 m) MSL to 130 ft (39.6 m) MSL. Pine flatwoods and dry prairies with lesser amounts of temperate hardwood forest, scrub and high pine comprise the ecosystems in these uplands (Crumpacker, 1992). A scarp with relief of approximately 25 ft (7.6 m) separates the Polk and Lake Uplands from the Gulf Coastal Lowlands and Western Valley (Arthur and Rupert, 1989). These two uplands contain three minor ridges: the Winter Haven Ridge, the Lake Henry Ridge and the Lakeland Ridge (White, 1970). The land surface is comprised mostly of mild to gently rolling hills gradually increasing in elevation eastward. Miocene-Pliocene clays in this region overlying older carbonates create a hydrogeologic environment conducive to the rapid formation of large cover-collapse sinkholes. Scott (2004) proposes to rename the Polk Uplands in combination with the DeSoto Plain: the Polk-DeSoto Plain. The part of the Lake Upland in the present study area is proposed to be renamed the Green Swamp Karst Plain (Scott, 2004). The DeSoto Plain is a broad, gently sloping area south of the Polk Upland, east of the Gulf Coastal Lowlands and west of the Lake Wales Ridge. Elevations vary between 30 and 100 ft (9.1 to 30.5 m) MSL (Wilson, 1977). The DeSoto Plain varies from 10 to 40 mi (16.1 to 64.4 km) in length from north to south and 10 to 50 mi (16.1 to 80.5 km) in width from west to east. Ecosystems present within the area include pine flatwoods and dry prairie with minor swamp, scrub and high pine (Crumpacker, 1992). The lithology consists of thick sandy clays over Pliocene and Miocene limestones of poor induration. The most prominent geomorphic feature in the study area is the Lake Wales Ridge. This large elongate upland extends from Lake County south to Highlands County, where it is flanked by paleodune fields on the eastern margin (Scott et al., 2001). Ecosystems on the Ridge include freshwater marsh, pine flatwoods and dry prairies (Crumpacker, 1992). A belt of lakes dominate the Intraridge Valley in the southern part of the Lake Wales Ridge. Geophysical investigations of lakes within the Intraridge Valley confirm a karst-related origin: irregular, discontinuous seismic reflectors underneath some lakes reveal breaches through confining beds overlying the FAS (Evans et al., 1994; Tihansky et al., 1996), thus indicating that the large collapse features occurred prior to or during Pliocene silicicla stic deposition (Arthur et al., 1995). Elevations on the Lake Wales Ridge range from approximately 70 to 312 ft (21 to 95.1 m) MSL, the latter forming a hilltop feature known as Sugarloaf Mountain in Lake County. Unlike the geology of the Brooksville Ridge, the Lake

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BULLETIN NO. 68 15 Wales Ridge contains a very thick sequence of permeable Pliocene-Pleistocene sediments (as much as 350 ft [107 m]; see also Surficial aquifer system, p. 53) overlying variably thick clays of the Peace River Formation. In the southern part of the Ridge, depth to carbonate rocks exceeds 325 ft (99.1 m) BLS. Morphology of the eastern flank of the Lake Wales Ridge was likely controlled by highenergy shoreline currents throughout the Pleistocene (and perhaps the late Pliocene) as indicated by the sharp topographic relief on the eastern side of the Ridge. The presence of discoid quartz pebbles in these sediments (Cypresshead Formation) also indicates a high energy depositional environment (Tom Scott, personal communication, 2004). In contrast, the western side of the southern part of the Ridge is flanked by less pronounced topographic relief on the Polk Upland and DeSoto Plain. The general topographic relief of the southern part of the Lake Wales Ridge mimics that of the emergent part of the Florida Platform with a steep shelf slope along the east and a broad gentle slope to the west. Along the southern margin of the Ridge (Figure 7), subtle topographic ridges that trend toward the west bear remarkable resemblance to the southern Florida peninsula and the Florida Keys suggesting that paleo-longshore and ocean currents (e.g., loop current) that existed during the Plio-Pleistocene are similar to those of present day. Petuch (1994) referred to this area as the Caloosahatchee Strait. Sinkholes In addition to paleo-sea levels and ocean currents, karst processes have sculpted the landscape of southwest Florida. Sinclair et al. (1985) mapped four types of sinkholes in the SWFWMD: 1) limestone dissolution: slowdeveloping, funnel-shaped with a growth rate similar to the rate at which the carbonate rocks dissolve, overburden is thin; 2) limestone collapse: forms abruptly and overburden is thin 3) coversubsidence sinkholes: gradual formation and generally small diameter, where overlying sands infill limestone dissolution cavities, overburden is greater than 30 ft (9.1 m) thick; and 4) cover-collapse sinkholes: sudden formation and relatively large in diameter, forming upon a breach of clayey material overlying a cavity, overburden is greater than 30 ft (9.1 m) thick. These sinkholes significantly contribute to interaction between surface and groundwater, intra-aquifer and inter-aquifer communication (e.g., Tihansky, 1999) and the vulnerability of aquifers to surface sources of contamination (Arthur et al., 2007). Plate 3 reflects the distribution of closed topographic depressions (CTD) throughout the SWFWMD region. This map is based on a 15 m (49.2 ft) resolution digital elevation model (DEM) produced by the FDEP-FGS in cooperation with othe r FDEP programs and Florida’s water management districts. While not all CTDs reflect karst features (i.e., paleodunes, etc. may also be included), this depression coverage provides a good approximation of sinkhole distribution patterns within the study area. The coverage, however, does not reflect the tens of thousands (if not more) of buried sinkholes detectable by means of surface geophysical surveys (e.g., Wilson and Beck, 1988; Moore and Stewart, 1983), nor does it include small karst features detectable by LIDAR or sinkholes that formed since the USGS topographic maps were last updated. Springs Springs predominantly occur in the northern two-thirds of the study area (Figure 6). Submarine springs occur offshore of Lee County and between Pinellas County and Citrus County (Ryder, 1985; DeWitt, 2003). Five of Florida’s thirty-three first magnitude springs ( 100 ft3/sec; 2.83 m3/sec) occur within the study area: Kings Bay Springs Group, Homosassa Springs Group, Chassahowitzka Springs Group (all in Citrus County), Weeki Wachee Springs Group (Hernando County) and the Rainbow Springs Group (Marion County) (Champion and Starks, 2001). The Coastal Springs Groundwater Basin (Knochenmus and Yobbi, 2001) encompasses parts of Citrus, Hernando and Pasco Counties and includes three of the five first magnitude springs. The Coastal Springs Groundwater Basin is made up of four sub-basins: Aripeka, Weeki Wachee, Chassahowitzka and Homosassa Springs. These groundwater sub-basins comprise part of the total recharge area for these springs. Surface water basins comprise the other component. As defined and described in DeHan

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FLORIDA GEOLOGICAL SURVEY 16 Explanation Counties Lake Wales Ridge 155 ft 0 ft Area of Interest 310 ft Topography of South-Central Florida 01 0 5M i l e s 010 5Kilometers Projection: Custom FDEP Albers Figure 7. Shaded topographic relief of the southern extent of the Lake Wales Ridge.

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BULLETIN NO. 68 17 (2004), “those parts of surface-water and groundwater basins that contribute to the flow of a spring” are called springsheds. Given the proximity and hydraulic interrelationships among the springsheds of the Coastal Springs Groundwater Basin, the term “Springshed Group,” (analogous to a “Group” in lithostratigraphic nomenclature) is herein introduced to characterize this and similar regions of coalescing springsheds (e.g., Coastal Springs Springshed Group). Copeland (2003a) compiled a Florida springs classification system and glossary to facilitate standardized use of springs-related nomenclature among Florida’s various technical (i.e. cave divers), scientific and regulatory/planning communities. The Coastal Springs Springshed Group and the many other springs and springsheds in the study area support unique ecosystems that harbor diverse flora and fauna (Scott et al., 2004; Champion and Starks, 2001). When water quality and quantity decline, these ecosystems are adversely affected. The magnitude and nature of the threats varies within each springshed based on land use and geology (Hartnett, 2000; Florida Department of Community Affairs and Florida Department of Environmental Protection, 2002). It is noteworthy that springshed boundaries are timedependent; they migrate in response to anthropogenic activity (e.g., pumping/withdrawal) and seasonal/climatic effects on the potentiometric surface (DeHan, 2004; Greenhalgh, 2004; Scott et al., 2004). Since the 1970’s scientists have documented a decline in water quality in most of Florida’s springs especially with regard to nutrients (Jones et al., 1998; Hartnett, 2000; Copeland, 2003b). Nitrate is of particular concern as high amounts may lead to excessive growth and eventual eutrophication of surface water bodies. Nuisance and exotic plants can cause reduction of water flow, reduction of dissolved oxygen and habitat changes (Hartnett, 2000). Nitrate has been a concern in SWFWMD for many years as increased levels of nitrates are being detected at many springs (Jones et al., 1997). Natural background concentration of nitrates in the FAS is less than 0.01 mg/L (Champion and Starks, 2001). Florida government agencies have recently proposed best management practices (BMPs) to protect and conserve Florida’s springs (Florida Department of Community Affairs and Florida Department of Environmental Protection, 2002). Spring-water quantity is another issue associated with development and population growth. Under predevelopment conditions springs accounted for about 84 percent of water discharged from the FAS (Ryder, 1985). As development increases and more well fields are used, the potentiometric surface of the FAS is lowered. This results in lower spring discharge, which can then result in changes in water quality (Lee, 1998). Spring flows become dramatically reduced or eliminated by over-pumping water from the aquifer. Near coastal zones, changes in aquifer conditions can also affect the location of the transition zone between fresh and salt water (Scott et al., 2004). As spring discharge rates decrease, calcium and magnesium have been observed to increase possibly owing to upconing or the removal of water from intergranular storage (Rick Copeland, personal communication, 2006). Although not fully established at the current time, preliminary evidence suggests that the upconing of sulfates and other constituents (i.e., micronutrients) may be contributing to algal development in springs (Sam Upchurch, personal communication, 2006). Corresponding increases in chlorides may also be observed in the spring water as discharge rates decrease. These conditions also allow migration of saltwater further inland (Lee, 1998). Hydrogeology Three major hydrostratigraphic units occur in west-central Florida: the surficial aquifer system (SAS), the intermediate aquifer system/intermediate confining unit (IAS/ICU) and the Floridan aquifer system (FAS). Miller (1986) divides the FAS into two zones of higher permeability: the Upper Floridan aquifer (UFA) and the Lower Floridan aquifer (LFA), which are separated by one or more regional confining units (Middle Floridan confining unit; MFCU).

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FLORIDA GEOLOGICAL SURVEY 18 In this report, nomenclature and definitions of units are primarily based on that proposed by the “Ad Hoc Committee on Florida Hydrostratigraphic Unit Definitions” Southeastern Geological Society, 1986). A 2nd Ad Hoc Committee on Florida Hydrostratigraphic Unit Definitions (CFHUD II) is presently convened to address identified concerns regarding exis ting nomenclature and definitions (Copeland et al., in review). The CFHUD II is comprised of representatives from the FDEP-FGS, USGS, water management districts and consulting firms. Appendix 1 includes a commentary on nomenclatural issues with regard to Florida’ s hydrostratigraphy. The present study adopts the following aquifer-system names and definitions, which are minor revisions of the widely accepted, yet dated Southeastern Geological Society (1986) proposal. These definitions are revised in the context of statewide application, and not limited to the study area. Appendix 2 provides explanation of changes from original Southeastern Geological Society (1986) definitions. surficial aquifer system the permeable hydrogeologic unit contiguous with land surface that is comprised principally of unconsolidated to poorly indurated siliciclastic deposits. It also includes carbonate rocks and sediments, other than those of the FAS where the Floridan is at or near land surface. Rocks and sediments making up the SAS belong to all or part of the Miocene to Holo cene Series. The SAS contains the water table and water within it is under mainly unconfined conditions; however, beds of low permeability may cause semi-confined or locally confined conditions to prevail in its deeper parts. Locally perched water-table conditions occur as well. The lower limit of the SAS coincides with the top of laterally extensive and vertically persistent beds of much lower permeability. intermediate aquifer system/ intermediate confining unit – includes all rocks that lie between and collectively retard the exchange of water between the overlying SAS (or land surface) and the underlying FAS. These rocks in general consist of coarse-to-fine-grained siliciclastic deposits interlayered with carbonate strata belonging to parts of the Oligocene and younger series. The aquifers within this system contain water under semi-confined to confined conditions. The top of the IAS/ICU coincides with the base of the SAS and on a local scale with land surface. The base of the IAS/ICU is hydraulically separated to a significant degree from the top of the FAS. Floridan aquifer system – a thick, predominantly carbonate sequence that includes all or part of the Paleocene to Lower Miocene Series and functions regionally as a water-yielding hydraulic unit. Where overlain by the IAS/ICU, the FAS contains water under confined conditions. When overlain directly by the SAS, the FAS may or may not contain water under confined conditions depending on the extent of low permeability material within the base of the SAS. Where the carbonate rocks crop out or are covered by a veneer of permeable siliciclastics, the FAS generally contains water under unconfined conditions near the top of the aquifer system, but because of vertical variations in permeability, deeper zones may contain water under confined conditions. The FAS is present throughout the State and is the deepest part of the active groundwater flow system on mainland Florida. The top of the FAS generally coincides with the absence of significant thicknesses of siliciclastics from the section and with the top of the vertically persistent permeable carbonate section. Generalized correlations between hydrostratigraphic units and lithostratigraphic units mapped in this study are presented in Table 2. The Hydrostratigraphy section, p. 52, of this report provides a more detailed discussion of these aquifer systems. Delineation of aquifer– system boundaries is described in Methods , p. 20.

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BULLETIN NO. 68 19 Table 2. Generalized correlation chart for uni ts mapped within study area (ages compile d from Covington, 1993, Missimer et al., 1994, Scott et al., 1994, and Wingard et al., 1994). Numbers are million years before present. Ages are included for reference on ly and are not scaled to correlate with all columns in the table. MFCU is Middle Floridan confining unit; UDSC includes the Tamiami, Ft. Thom pson and Caloosahatchee Formations. 19 BULLETIN NO. 68

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FLORIDA GEOLOGICAL SURVEY 20 Sediments comprising the SAS are predominately post-Hawthorn in age and generally consist of some combination of sands shells and clays. In parts of the northern District where the IAS/ICU is not laterally extensive, discontinuous clay lenses serve as basal SAS confinement, locally separating the SAS from the FAS. Some of these basal clays may be erosional remnants of (and correlative with) lithostratigraphic units comprising the IAS/ICU. In areas where Pliocene clayey sediments (see “clayey sand,” Figure 4) are exposed at or near land surface, such as west-central Polk County, the SAS or water-table aquifer may not be present; instead, the setting reflects IAS/ICU overlying the FAS. Where hydraulic continuity exists between uppermost Hawthorn Group sands and younger sediments, the SAS includes those sands, which are generally less than 20 ft (6.1 meters) thick. In the southernmost part of the study area, the Ft. Thompson and Caloosahatchee Formations and upper permeable sediments of the Tamiami Formation comprise the SAS. Although mapping of these complex “post-Hawthorn” units is beyond the scope of this study, research did focus on the depth and extent of clays within the Pliocene Tamiami Formation, which are significant as they comprise the base of the SAS in the region (e.g., Reese, 2000; Weinberg and Cowart, 2001). The IAS/ICU occurs throughout most of Florida (Scott, 1992a) and correlates with aquifer systems in parts of Georgia and Alabama. In the study area, it is comprised of midto upper Oligocene Pliocene sediments and is generally continuous south of Pasco County. As this hydrostratigraphic unit thickens southward, interlayered permeable carbonates become important water-producing zones, especially south of Manatee County where the FAS water becomes less potable. In this area, three permeable zones are present; however, correlation and mapping of these zones is difficult, even with the use of hydrochemical parameters (Knochenm us and Bowman, 1998; Torres et al., 2001; Knochenmus, 2006). North of Hillsborough County, the IAS/ICU predominantly occurs within the uplands and ridges, where it functions hydrologically as a semi-confining to confining unit. The FAS is one of the most productive aquifers in the world. It underlies all of Florida, southern Georgia and small parts of Alabama and South Carolina for a total area of about 100,000 mi2 (~259,000 km2) (Johnston and Bush, 1988). In parts of southwest Florida, south from Sarasota, Charlotte, Glades and Lee Counties, the FAS contains mineralized, nonpotable water. As a result, relatively permeable zones within the IAS/ICU comprise the main source of water supply (Miller, 1986; Torres et al., 2001) in this region. The FAS is confined except in parts of the northern third of the study area where it occurs at or just below land surface (Ryder, 1985). Throughout the study area, the FAS predominately consists of carbonate rocks (Southeastern Geological Society, 1986) ranging in age from Paleocene to Miocene. METHODS Sample Description More than 250 detailed lithologic descriptions of borehole cores and cuttings were completed for this study. These descriptions record standard rock, mineral, fossil and textural features. Selected parameters include color, induration, grain size and range, sorting, roundness, mineral percentages and special descriptive, depositional or sedimentary features. Descriptions of carbonate material were based on the Dunham (1962) classification system, which focuses on depositional texture and whether the rock is mud-supported or grainsupported: 1) mudstone muddy carbonate rock containing less than 10 percent grains, 2) wackestone mud supported rock containing more than 10 percent grains, 3) packstone grain supported muddy carbonate, 4) grainstone – mud-free carbonate rock which is grain supported and 5) boundstone carbonate rock showing signs of being bound (e.g. cementation) during deposition and reflecting original position of growth. It should be noted that the Dunham (1962) classification considers a “grain” as having a diameter greater than 20 microns, while “mud” is less than 20 microns. As a result, a very fine grained grainstone may appear as a mudstone even under a low-power binocular microscope (David Budd, 2004, personal

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BULLETIN NO. 68 21 communication). It is likely that this factor has biased identification of mudstones in lithologic descriptions that may technically be fine-grained grainstones. During archiving of borehole cuttings, samples are gently washed in a 63 micron sieve to remove any drilling mud (e.g., silt and claysized material). When describing lithologic characteristics of borehole cuttings, care was taken to inspect the washed and unwashed archival fractions of the samples. In many cases, especially for older wells, the washed sample fraction may under-represent the clay fraction of the sample. For example, cuttings representing the sandy clayey Nocatee Member (Arcadia Formation) may have been washed to the degree that only sand remains in the archived sample. In such cases, the unwashed sets of samples provide a better representation of the original clay-rich lithology. The descriptions are coded within the aforementioned Microsoft AccessTM database – FGS_Wells . This database is undergoing continued enhancements including migration to a more robust enterprise-level platform. These and other lithologic descriptions are available from the Florida Geological Survey web site: http://www.dep.state.fl.us/geology/. Delineation of Boundaries Formations/Members Formation and member boundaries were determined for all described samples and for cores, cuttings and geophysical logs from an additional ~600 wells. Florida Geological Survey published and unpublished data (e.g., Stewart, 1966; Hickey, 1982, 1990; Johnson, 1986; Miller, 1988; Scott, 1988; Campbell, 1989; DeWitt, 1990; Campbell et al., 1993, 1995; Clayton, 1994, 1999; Green et al., 1995, 1999; Sacks, 1996; Arthur et al., 2001a; Gates, 2001; Missimer, 2002; and O’Reilly et al., 2002) provided lithostratigraphic and hydrostratigraphic boundary information on an additional ~200 wells. Gamma-ray logs and fossil assemblages are used only to supplement the lithologic data in the determination of the boundaries. Where uncertainty exists regarding the exact position of the formation boundary, or where the boundary is inferred within an in terval of poor or no sample recovery, a dashed rather than solid line is shown on the cross sections. Dashed contacts are also drawn where only a gamma-ray log was used and no samples were available for inspection. In cases where sample quality is poor, as is often true with cuttings, the gammaray logs become more important in the determination of formation boundaries. Uncertainties in lithostratigraphic unit boundaries were recorded in a database of elevations and thicknesses. These uncertainties exist for several reasons. In the case of inspecting cores, it is not uncommon for two experienced geologists to disagree on a formation boundary, especially when it is subtle or gradational. Moreover, the core may have poor recovery, resulting in missing intervals. Regarding cuttings, samples often contain borehole cavings, whereby the sampled interval contains sediment or rock fragments from overlying units. For example, in an extreme case, dolostone cuttings from the Avon Park Formation may contain phosphatic sands from the upper Hawthorn Group. As a result, it is not uncommon for a formation boundary estimation based on cuttings to include an uncertainty range on the order of 20 ft (6.1 m) based solely on sample quality. Other uncertainties with respect to mapped unit elevations also exist (see Map Development and Data Management , p. 24). Table 2 summarizes the lithostratigraphic units shown on the maps. The same units are also shown on the cross sections. For the purposes of this study, post-Hawthorn units are depicted as Pliocene-Pleistocene sediments (undifferentiated) and Pleistocene Holocene undifferentiated sand and sh ell or sand and clay (UDSS or UDSC, respectively). Aquifer Systems Delineations of hydrostratigraphic units in this report are based on the following: 1) available hydrogeologic data collected during drilling, 2) borehole geophysical logs,

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FLORIDA GEOLOGICAL SURVEY 22 3) hydrogeologic characteristics of the samples (e.g., estimated porosity and permeability, hydraulic continuity between lithostratigraphic units), 4) potentiometric data from nested monitor wells, and 5) in the absence of other data, correlation to lithostratigraphic units. Application of the first four methods is highly preferred; the majority of this data originates from ROMP wells. Contacts between aquifer systems can be very subtle or abrupt depending on the hydrogeologic properties of the rocks and sediments. When only lithologic material from a borehole is available on which to base an aquifer-system boundary, further complications arise. Preferential removal of clay-sized particles, either during drilling or sample archiving (e.g., sorting during material transfer or washing of cuttings), tend to bias toward interpretations of higher sample permeability. Delineation of the basal contact of the SAS is perhaps the most susceptible to the aforementioned bias. If the contact is based solely on estimates of hydrogeologic properties of lithologic data, misrepresentation of clay content, especially in borehole cuttings may result in the interpretation of a preferentially deep base of the SAS. This issue may become a factor where the SAS may include sediments as old as the upper Hawthorn Group. On the other hand, permeable sands along the top of the upper Peace River Formation in Manatee County (Tom Scott, personal communication, 2006) comprise the lower part of the SAS. If there is reason to believe that the two units (Hawthorn and postHawthorn Group sediments) are hydraulically connected, both would be considered part of the SAS. Alternatively, sandy clays overlying clayrich Hawthorn Group sediments would be considered part of the IAS/ICU (assuming sufficient lateral extent). Further south, the Tamiami Formation is included within both the SAS and IAS/ICU. Noting the above exceptions, the lateral extent of the IAS/ICU broadly corresponds to the extent of Hawthorn Group sediments, except where those sediments are part of the FAS (e.g., the Tampa Member [Arcadia Formation] along the upper reaches of the Hillsborough River). For consistency, in areas where the IAS/ICU is mapped owing to sufficient lateral continuity, the SAS is mapped over the same extent. In areas where the SAS and IAS/ICU are discontinuous, the FAS is generally characterized as unconfined to semi-confined (see Hydrostratigraphy , p. 52, for more detail). Figure 8 represents a compilation of hydrogeological data to provide correlation between hydrostra tigraphic units and lithostratigraphic units. In most areas, the correlation is readily apparent, such as the relation between the top of the Suwannee Limestone in Sarasota County with the top of the FAS. In another example, the Tampa Member (Arcadia Formation) is hydraulically connected to the FAS in Pinellas County and therefore comprises the uppermost part of the FAS. The correlations, however, are not always straightforward, such as the area denoted as “variable” (Suwannee Limestone and Nocatee Member, Arcadia Formation) in DeSoto County (Figure 8). Cross-Section Construction Detailed lithologic de scriptions, gamma-ray logs and hydrologic data comprise the bulk of the information used to develop the cross sections. The dominant sources of information for crosssection control are SW FWMD ROMP wells; FDEP-FGS wells were included to fill out appropriate data-point coverage for the cross sections. Where no litholog ic data was available, borehole geophysical logs were used. Of these geophysical logs, gamma-ra y logs were the most readily available and generally useful for correlative purposes within the study area. Gamma-ray logs were included in the cross sections to allow comparison of the gamma-ray signatures relative to each stratigraphic unit. The following discussion outli nes the methods used for construction of the cross sections for this study. Topography Topographic profiles were included on each cross section to facilitate comparison of surface morphologies with subsurface stratigraphy. Data used to construct these profiles was taken from U.S. Geological Survey 1:24,000 (7.5 minute) quadrangle maps. The profiles include selected anthropogenic features, cultural boundaries and landforms.

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BULLETIN NO. 68 23 Gulf of MexicoExplanation Study Area Contours (75ft interval) Avon Park Formation Ocala Limestone Ocala Ls. & Avon Park Fm. Suwannee Limestone Suwannee Ls. & Tampa Mbr. Tampa Member VariableCorrelated FAS Units 0 -7 5 3 0 0 1 5 0 2 2 5 4 5 0 3 7 5 -5 2 5 6 0 0 6 7 5 7 5 7 5 0 8 2 5 7 5 7 5 0 7 5 7 5 7 5 0 7 5 4 50 0 0 0 4 5 0 0 6 7 5 6 7 5 6 7 5 0 7 5 0 7 5 6 7 5 2 2 5 4 5 0 7 5 0 7 5 7 5 Generalized Correlation Between Lithostratigraphy and Top of the Floridan aquifer system Projection: Custom FDEP Albers Scale 1:1,750,000 010203040 5 Kilometers 010203040 5 Miles Figure 8. Generalized correlation between lithostrati graphic units and the surface of the FAS. The area labeled “Variable” includes parts of the Nocatee Member (Arcadia Formation, Hawthorn Group) and the Suwannee Limestone.

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FLORIDA GEOLOGICAL SURVEY 24 Lithology For each well in a cross section, a stratigraphic column was developed to represent borehole lithology. The columns were based on either existing descriptions or new descriptions generated for this report. Hatch patterns depict primary lithologies in the columns, with accessory minerals shown on the right of the columns as text codes. Where space is available, the cross sections contain an explanatory legend that defines mineralogic and lithologic codes and patterns. For those crosssections without sufficient space to include the “Explanation,” it is also provided for reference in Figure 9. Accessory-mineral codes are generally the same as those used in the FDEPFGS lithologic database ( FGS_Wells ). If the volume of reported accessory sand-sized minerals exceeds 5 percent, the content is represented by a stippled sand pattern. If the amount of accessory sand-sized minerals is less than 5 percent, or if the amount is not known based on existing descriptions, the accessories are listed in the text codes. The mineral text codes are listed in decreasing order of abundance if the relative mineral abundance has been reported. The degree of detail within each lithologic column generally reflects the type of material available for description as well as the degree of detail in the description. In most cases, more detailed lithology exists for the cores. The minimum bed thickness represented on the stratigraphic columns is 5 ft (1.5 m) due to graphical constraints. There are several examples where lithologies and accessory minerals have been averaged over a 5 to 10 foot (1.5 to 3.0 m) interval to accommodate this graphical limitation. Gamma-ray Logs Selected gamma-ray logs are plotted to the right of stratigraphic columns on the cross sections. These logs are used as a supplement to delineate formation boundaries and allow comparison of gamma-ray activity between the various lithostratigraphic and hydrostratigraphic units (e.g. Gilboy, 1983; Green et al., 1995; Scott, 1988 and Davis et al., 2001). Gamma-ray intensity units, when known, are shown on the logs (horizontal axis) in counts per second (CPS) or in American Petroleum Institute (API) units. Inconsistencies between logs exist due to different log settings (e.g., time constant, range) and borehole characteristics (e.g., depth of casing and lack of caliper logs to determine sediment wash-out or cavities), making quantitative comparison difficult. To allow assessment of the high degree of variability in the logs and to represent their natural response, the intensity scales have not been normalized. The logs are very useful in the identification of correlative "packages" of gamma-ray peaks and for comparison of the overall gamma-ray signature within formational units. Relatively high gamma-ray activity is generally correlative with phosphate, organic materials, heavy minerals and high-potassium clays. More subtle changes may reflect dolomite and accessory mineral content. Figure 10 summarizes general relationships between gamma-ray activity and mineralogy, the details of which are included in the discussion of each lithostratigraphic unit (see Lithostratigraphy , p. 30). Aquifer Systems Aquifer systems on the cross sections appear as hachured brackets on the left of each lithologic column. Patterns used in the hydrostratigraphic columns identify the three major aquifer systems present in the study area, as well as the MFCU. Map Development and Data Management For wells used in this study, elevations of lithostratigraphic and hydrostratigraphic units were recorded in a database that also included the corresponding FDEP-FGS well accession number (W-number), well name, comments about the well, the geologist(s) who made the determinations and well location (elevation, latitude and longitude). The unit elevations on which the maps are based are recorded in feet BLS; a separate column calculates the elevation

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BULLETIN NO. 68 25 LIMESTONE DOLOSTONE INTERBEDDED LIMESTONE & DOLOSTONE GYPSUM SHELL BED CHERT CLAY SURFICIAL AQUIFER SYSTEM M S P p O R I Q A Ch MICRITE SAND PHOSPHATE GRAVEL PHOSPHATE SAND ORGANICS SPAR IRON STAIN QUARTZ ANHYDRITE CHERT T C Sh D L No Spl G Py SILT CLAY SHELL DOLOSTONE HEAVY MINERALS NO SAMPLE GYPSUM PYRITE COMMENTS CROSS SECTIONS EXPLAN A TION THIN MANTLE OF IAS/ICU SEDIMENTS SEMI-CONFINED TO UNCONFINED FLORIDANAQUIFER SYSTEM CUTTINGS EXAMINED INTHIS INTERVAL INDICATE FORMATION PICKS SHOWN HATCHPATTERNS INTERMEDIATE AQUIFER SYSTEM / CONFINING UNIT FLORIDAN AQUIFER SYSTEM MID-FLORIDAN CONFINING UNIT COARSE MEDIUM FINE SILT COARSE MEDIUM FINE SAND COARSE MEDIUM FINE GRAVEL Figure 9. Explanation (legend for cross sections).

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FLORIDA GEOLOGICAL SURVEY 26 Figure 10. Characteristic gamma-ray ( ) log responses.

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BULLETIN NO. 68 27 relative to MSL. The database also records uncertainty in the unit elevations. Synthetic wells were added to the database to serve as contour control along the margins of the study area in order to facilitate a more accurate interpolated surface. Quality assurance of all well-head elevations was accomplished by comparing the reported elevation with a 15 m (49 ft) DEM. The data on which the maps and cross sections are based is available from http://www.uflib.ufl.edu/ufdc/?b=UF00087428& v=00001 Map Interpolation and Spatial Accuracy As the GIS database was developed, preliminary contour maps were generated to allow identification of anomalous elevations and data gaps. ArcView with the Spatial Analyst extension was used to generate the initial contour maps. For each map, a grid surface model was calculated using a surface interpolation method. Contours were then generated from the surface model. The inverse distance weighted (IDW) interpolator was found to provide a very useful surface model for identifying problem areas and outliers that required additional research. As these issues were identified, borehole cuttings were retrieved from the FDEP-FGS core repository and reevaluated in context of: 1) proximal stratigraphy, 2) sample quality, and 3) stratigraphic boundary uncertainty. This process of generating and reviewing maps and re-examining samples was repeated numerous times through the course of this study. Arthur and Pollock (1998) suggested that the IDW interpolation method is not suitable for geologic mapping of stratigraphic data. The IDW method was used only as an iterative review tool. Interim maps for the initial phases of this project were generated using the spline interpolator. Arthur and Pollock (1998) found the spline-tension method preferable to IDW because spline yielded surface models that were more accurate and geologically characteristic. Upon review of subsequent interim maps generated for this project , several shortcomings in application of the spline interpolator were recognized. These include false highs and lows in the model surface that do not reflect any well control and loss of contour accuracy along the margins of the maps. Moreover, as the interpolator was adjusted to yield smoother contours, the interpolated surface became less accurate. With the exception of accuracy at a given well location, it was also difficult to assess the error associated with the maps in data-poor areas. Due to the “overshooting contour” effect (e.g., false topographic highs), shallow map units may exceed land surface elevations in certain areas, especially along areas of high topographic relief. Prior to generation of the final maps, a reassessment of interpolation methods was completed. Through an iterative process, kriging was identified as the most robust and accurate surface interpolator. The GIS project was then migrated to ESRI ArcMap 8.3. The map-unit elevation database was imported into ArcMap and projected in the FDEP standard projection (custom Albers equal-area conic projection). Individual surfaces were then interpolated using the ordinary kriging function within the ESRI Geostatistical Analyst. Iterations of krige data models were produced for each map unit to minimize the map error. Prediction errors and other descriptive statistics for each map were recorded and used to identify appropriate contour intervals (see Contour interval selection, p. 30). When evaluating krige statistics, the variability of the prediction (as standard deviation) is overestimated when the root mean squared predic tion error (RMS) is less than the average standard error (ASE) of the prediction error (Table 3; Johnston et al., 2001). The krige error automatically reported by the software is based on the error within a rectangular area defined by the distribution of the data (i.e., wells). For nearly all of the maps in this report, these results are misleading because the datasets have an irregular spatial distribution. As a result, for each kriged surface, a prediction standard error map was also created and masked to the spatial extent of the unit being mapped. The average standard error of this prediction standard error map was then calculated and recorded (Table 3).

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FLORIDA GEOLOGICAL SURVEY 28 As an extra measure to assess map accuracy, a script was written to allow comparison of the observed map-unit elevations (i.e., top of the Suwannee Limestone in a given well) with the value of the final interpolated grid cell in which the well is located. On Table 3, this data is summarized in the “Grid to Point” column, where the “mean” represen ts the average of the difference between grid cells and map unit elevations for each well located within its respective grid cell. In every case, the mean “Grid to Point” value is less than ft, (0.9 m) for all maps, and the standard deviation (s) is less than 20 ft (6.1 m) for 18 of the 22 maps and less than or equal to 30 ft (9.1 m) for the remaining 4 maps (Table 3). Qualitative evaluation of these errors suggests they are normally distributed. The standard deviations for the “Grid to Point” calculations (Table 3) are well within acceptable limits, especially when considering: 1) geologic processes that can create perturbations in a mapped surface (e.g., faults, paleo-karst, paleo-environmental features [e.g., wave-cut scarps, river valleys]), 2) well location error or uncertainty, 3) sample quality (e.g., cuttings interval and borehole cavings) and 4) formation pick uncertainty (i.e., gradational contacts, differences in professional opinion, etc.). Once the kriged surfaces were optimized for each map unit, the shallow surfaces (i.e., top of the Peace River Formation) were compared to land surface elevations. To accomplish this, the kriged surface was converted to a raster file (grid) using a 400 m2 (4305.6 ft2) cell size, which was then subtracted from the FDEP-FGS 15 m (49.2 ft.) resolution DEM to remove interpolated elevations that exceeded land surface. The grid was clipped (i.e., masked) to the lateral extent of its respective map unit. For most of the mapped units, contours generated from the kriged and the DEM-trimmed surfaces were generally irregular or jagged. This characteristic is not only atypical for maps depicting subsurface elevations and thicknesses, but it also overemphasizes the level of resolution represented by the maps. To remove these localized and misrepresentative contour anomalies, the grids were smoothed using the neighborhood statistics function in Spatial Analyst. Color shading, contour lines and labels were then added. It is noteworthy that substantial effort was devoted to surface interpolations that would allow weighting of data from cores preferentially over that of cuttings and geophysical logs. Combinations of grid averages, weights, and point buffering applied within various interpolators were evaluated during extensive sensitivity analyses and validation. In the final assessment, too many negative attributes were associated with what was considered the optimal core-weighting technique. As a result, the well data from cores, cuttings and geophysical logs are all considered equally in the maps. Unlike hand-drawn contours, the smoothed contours generated from krige-interpolated surfaces do not always reflect highly anomalous elevation data points. While this may be considered a disadvantage, it is substantially outweighed by numerous advantages of the digital products developed during this study: 1) the interpolated surfaces are supported by accuracy and precision statistics, 2) the calculated grids can be used in a variety of groundwater flow models and 3D applications, 3) GIS compatibility exists, including inherent scalability and flexibility, and 4) the maps can be readily updated with new information. As a result, manual modification (editing) of the contours to reflect anomalous values would create discrepancies between the maps and the grid coverages. In cases where contour adjustments were deemed necessary to reflect sharp-relief surface trends (as opposed to single anomalous well values), synthetic control points were added to improve map accuracy while maintaining consistency with the calculated grids.

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BULLETIN NO. 68 29 Table 3. Summary of krige interpolation statistics for each map; ASE is average standard error of the prediction error; RMS is root mean square of the prediction error. Gray pattern indicates that the prediction error may be overestimated (i.e., ASE>RMS). Prediction error (1s)3Prediction error (1s; map)4 "Grid to Point" Error Calculation Map Unit (s)=surface (t)=thickness ASE RMS Mean of the ASE (1s) 2 X Mean of the ASE (2s) Map Contour Interval mean s Number of Wells5 Model Algorithm Hawthorn Group (s) 23 34 22 4425 1.6411526Exponential Hawthorn Group (t) 57 68 56 11275 -0.2521321Spherical Peace River (s) 25 35 22 4425 0.649349Exponential Peace River (t) 27 34 37 7430 0.3325324Exponential Bone Valley Mbr. (s) 26 35 23 4640 2.611033Exponential Bone Valley Mbr. (t) 7 7 10 2020 0.26338Spherical Arcadia Fm. (s) 29 35 25 5030 0.711466Exponential Arcadia Fm. (t) 67 65 61 12275 -0.2719341Exponential Tampa Member (s) 50 39 44 8850 0.611235Exponential Tampa Member (t) 40 40 39 7850 0.1330190Exponential Nocatee Member (s) 64 48 55 11075 1.1112117Exponential Nocatee Member (t) 38 36 37 7450 -0.2421105Exponential Suwannee Limestone (s) 75 51 68 13675 0.9818414Exponential Suwannee Limestone (t) 43 47 37 7450 0.112265Exponential Ocala Limestone (s) 67 47 63 12675 0.9714527Spherical Ocala Limestone (t) 34 49 30 6050 -0.1510325Exponential Avon Park Fm. (s) 84 53 79 158100 0.7713391Circular SAS (t) 25 29 25 5025 0.4118703Exponential IAS/ICU (s) 24 34 21 4225 -1.2713488Exponential IAS/ICU (t) 58 62 54 108 75 0.0218334Spherical FAS (s) 68 46 64 12875 0.8716655Exponential MFCU (s) 166 122 167 334150 0.8312101Spherical 3 krige statistics based on rectangular fit around distribution of wells 4 krige statistics based on irregular extent of mapped unit, which more accurately represents error within the study area 5 total number of wells used to produce each map, including wells (not shown on plat es) within the outer 10 mile buffer zone 29 BULLETIN NO. 68

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FLORIDA GEOLOGICAL SURVEY 30 Contour Interval Selection Contour intervals for each map were selected based on the mean of the ASE for each respective krige model trimmed to the map unit extents (Table 3 Footnote 2). If one assumes normality, the ASE of the prediction error is essentially the standard deviation (s) of the interpolated surface and represents a 68 percent level of significance. If one were to double the error (i.e., 2s), a 95 percent level of significance is achieved. To avoid inflating implied accuracy of the krige surfaces, the contour interval for all but two maps was selected between 1s and 2s. In other words, the selected contour interval is always greater than or equal to the mean of the ASE prediction error, except for the IAS/ICU thickness map and the MFCU surface map. Per Table 3, the error for these maps is overpredicted. For every contour map in this study, the standard deviation for the “Grid to Point” calculation described above (Table 3) is less than the contour interval. STRATIGRAPHY The stratigraphic framework of the westcentral Florida peninsula, encompassing the SWFWMD region, is presented from north to south in the following geographic subdivisions: northern region (eastern Levy, western Marion, Citrus, Sumter, western Lake, Hernando and Pasco Counties), central region (including Pinellas, Hillsborough, western Polk, Manatee and Hardee Counties), southern region (Sarasota, DeSoto and Charlotte Counties) and the eastern region (e.g., the Lake Wales Ridge, including eastern Polk and Highlands Counties). The framework discussion is subdivided into lithostratigraphy and hydrostratigraphy, and is characterized through a series of cross sections and maps (surfaces and thicknesses). East-west trending cross sections presented in this report (see Plate 1 for locations) are ordered from the north to south (i.e., the northern to southern regions; Plates 4-19), then north to south within the eastern region (Plates 20-28). Cross sections trending north-south are ordered from west to east as follows: Plates 29 and 30 in the northern region, Plates 31-35 in the central/eastern regions and Plates 36 and 37 in the southern region. Maps of lithostratigraphic units are presented from oldest to youngest (Plates 38 54) and hydrostratigraphic units are presented from shallow to deep (Plates 55 59). Lithostratigraphy Introduction Structure contour (surface) and isopach maps (thickness) in this report include Lower Eocene through Lower Pliocene lithostratigraphic units, which are described in detail in this section. Characterization of the mapped units includes age, lithology, mineralogy, porosity, significant fossils, distribution, nature of vertical and lateral contacts, distinguishing gamma-ray activity responses, relation to hydrostratigraphic units and environment of deposition. Superjacent and subjacent lithostratigraphic units (i.e., the Oldsmar Formation) are also presented. Eocene Series Oldsmar Formation The Lower Eocene Oldsmar Formation (“Oldsmar Limestone” of Applin and Applin, 1944) underlies the entire Florida peninsula. Miller (1986) describes the Oldsmar Formation as a white to gray limestone with variably thick interbeds of gray to light brown, crystalline dolostone that increases in abundance with depth. Thin beds of chert and evaporites, including pore-filling gypsum occur within the unit (Miller, 1986). Reese and Richardson (2008) report a glauconite marker horizon that occurs intermittently within upper ~200 ft (~ 61 m) of the Oldsmar Formation in the study area. Porosity types include intergranular, intragranular and fracture (e.g., “Boulder Zone”). Braunstein et al. (1988) indicate that the unit may have an unconformable contact with the subjacent Cedar Keys Formation; however, the contact with the overlying Avon Park Formation is possibly conformable. In the study area, the Oldsmar Formation limestones vary from packstone to wackestone.

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BULLETIN NO. 68 31 Dolostone is common as well. The microfossil Helicostegina gyralis (Figure 11) is common but not unique to the unit (Miller, 1986). In the southeastern Florida peninsula, this microfossil is common within a glauconitic bed that serves as an excellent geophysical marker (Duncan et al., 1994). Within the study area, the uppermost Oldsmar Formation contains gypsum as nodules, laminations and as pore-filling material. Stewart (1966) reports “selenite impregnation” in the unit and proposes that the gypsum is altered from anhydrite. In some areas, these gypsiferous, low-permeability carbonates comprise the upper part of the MFCU, whereas deeper in the section, the carbonates comprise the upper part of the LFA. Cander (1994) suggests that the Oldsmar Formation represents a shallow subtidal to supratidal carbonate paleoenvironment. Avon Park Formation The Middle Eocene Avon Park Formation (Miller, 1986) occurs in the subsurface throughout the study area and is the oldest lithostratigraphic unit exposed in Florida (Scott et al., 2001). This unit was originally described by Applin and Applin (1944) as two units, the Lake City Limestone and the Avon Park Limestone. Due to the inability (except locally) to distinguish these two formations based on lithology or fauna, Miller (1986) proposed that the term Lake City Limestone be abandoned and formalized the Avon Park Formation to include the two units of Applin and Applin (1944). Lithology of the Avon Park Formation varies between limestone and dolostone. The limestone is generally cream to light brown, poorly to well indurated, variably fossiliferous, skeletal/peloidal wackestone to grainstone with minor mudstone. The limestone can be interbedded with dark brown to tan very-fine to coarse-grained, vuggy, fossiliferous dolostones. Incomplete to complete dolomitization of limestone is also observed. Dolostone textures range from very fine-grained to coarsely recrystalized (sucrosic). Minor clay beds and organic-rich laminations may occur, especially at or near the top of the unit. Although not common, sedimentary structures include crossbeds and burrows. The burrows ( Callianassa sp.) generally occur in the uppermost thinly bedded updip part of the formation (e.g., crops out in Levy County). Accessory minerals include chert, pyrite, celestine, gypsum and quartz (some as doubly-terminated euhedral crystals “floating” in vugs). Gypsum tends to be more abundant with depth. Reese and Richardson (2008) report a glauconite marker horizon that occurs intermittently within lower ~200 ft (~ 61 m) of the Avon Park Formation. Porosity in the Avon Park Formation is generally intergranular in the limestone section. Fracture porosity occurs in the more densely recrystallized dolostone and intercrystalline porosity is characteristic of sucrosic textures. Pinpoint vugs and fossil molds are present to a lesser extent. Total porosity measured for 16 Avon Park Formation samples averages 31.7 percent (median = 30.0 percent) and ranges from 22.3 percent to 42.0 percent. Diagnostic fossils include the foraminifera Cushmania americana ( Dictyoconus americanus) and Fallotella (Coskinolina) floridana and the echinoid Neolaganum (Peronella ) dalli (Figure 12). The foraminfer Fallotella ( Dictyoconus ) cookei occurs in the Avon Park Formation as well as the Suwannee Limestone; however, presence of Cushmania americana is unique to the Avon Park Formation. Other fossils include algae, mollusks and carbonized plant remains (e.g., Thalassodendron sp.) (Scott, 2001). Miller (1986) reports the top of Lower Eocene rocks (the approximate base of Avon Park Formation) at depths ranging from -1,000 ft to -2,400 ft (-304.8 to -731.5 m) MSL within the study area. The Avon Park Formation varies in thickness across the study area, from 1,000 ft to 1,600 ft (304.8 to 487.7 m), with the thickest area occurring along nort heastern Polk County (Miller, 1986). Maximum observed elevations exceed 50 ft (15.2 m) MSL in northern Polk County (Plate 20). In the southernmost extent of the study area, the unit is encountered at depths exceeding -1500 ft (-457.2 m) MSL (Plate 38). The area, which is centered along eastern Charlotte Harbor, may be related to structural deformation (Winston, 1996).

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FLORIDA GEOLOGICAL SURVEY 32 Figure 11. Helicostegina gyralis , a foraminifer common within the Oldsmar Formation (bar = 1 mm). The contact relations between the Oldsmar and Avon Park Formations are generally subtle and difficult to identify within the study area, which supports the interpretation that the contact is possibly conformable (Braunstein et al., 1988). In general, the contact grades from a dolostone to a chalky white limestone. In many cases, however, these characteristics are not present. A useful faunal indicator of the transition into the Oldsmar Formation is the appearance of abundant Helicostegina gyralis (Figure 12; Miller, 1986). Although this foraminifer does not exclusively occur in the Oldsmar Formation, it generally appears in lowermost Avon Park Formation and increases in abundance in the Oldsmar Formation carbonates. The Ocala Limestone unconformably overlies the Avon Park Formation throughout nearly the entire study area; exceptions include parts of Levy and Citrus Counties (Avon Park Formation exposures) or where the Ocala Limestone is absent in the subsurface (northwestern Osceola County). The contact between these two units is readily apparent in many up-dip locations and difficult to determine down dip. The more obvious contact relations occur where: 1) lithology of the Avon Park Formation is tan to brow n dolostone, overlain by white to cream limestone of the Ocala Limestone (e.g., W-16456 [ROMP 49], Plates 14 and 33; W-9059, Plates 23 and 34) and 2) in the case where both units are limestone, the uppermost Avon Park Formation is grainsupported and contains disseminated organics or thin (less than 2 inches; ~ 5 cm) beds of peat (in some cases varying toward lignite), whereas the lowermost Ocala Limestone is finer grained and skeletal (e.g., W-720, Plates 6 and 29; W-12943 Plates 12 and 21). Although the Avon Park Formation is not defined based on bioassemblages, additional contact indicators include the appearance of diagnostic foraminifera and echinoi ds listed above, as well as abundance of coralline algae. Throughout most of the southwestern part of the study area, including nearly all of Manatee and Sarasota Counties, the contact between the Avon Park Formation and the Ocala Limestone is dolomitized (e.g., Plate 18) and as a result, formation boundary delineation is difficult. In this situation, subtle ch aracteristics can be used to delineate the two units. Dolomitization of the limestones with slightly varying textures may yield differences in dolostone textures and dolomite grain sizes. Fossil molds are another useful indicator, because fossil molds of diagnostic fossils may help narrow the uncertainty. For example, narrow, discoid vugs may represent prior Lepidocyclina sp. whereas smaller cone-shaped vugs may represent where Cushmania or Fallotella sp. were present prior

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BULLETIN NO. 68 33 Figure 12. Selected diagnostic fossils common within the Avon Park Formation. From left to right: Cushmania americana ( Dictyoconus americanus) (bar = 0.5 mm; Rupert, 1989), Fallotella (Coskinolina) floridana (bar = 1 mm; photo courtesy of Jonathan Bryan) and Neolaganum (Peronella ) dalli (bar = 15 mm; photo courtesy of Invert ebrate Paleontology, Florida Museum of Natural History [IP/FMNH]). to dolomitization/leaching (e.g., Plate 27; W17056 [ROMP 9]). In rare instances, selective dolomitization occurs where the original limestone matrix is dolomitized, however, the faunal assemblage (foraminifera and echinoids) remain as calcite. Gamma-ray response in the Avon Park Formation is generally due to variable dolomite and organic content. In many wells, high gamma-ray activity at or near the top of the Avon Park Formation corresponds to thin layers of organic material (e.g., Plate 16; W-16303 [ROMP TR 7-4]; Figure 10). Similar observations have been made east of the study area (Davis et al., 2001). In cases where the top of the Avon Park Formation has been dolomitized or recrystallized, this organicassociated gamma-ray peak tends to be a broadened, more subdued signal. The degree to which the signal remains is likely a function of the extent of recrystallization and amount of organic impurities remaining in the carbonate. Relative to the overlying Ocala Limestone, the Avon Park Formation ga mma-ray signature has higher background count rates and is more variable throughout the unit. In general, a relatively higher gamma-ray peak is observed at the top of the Avon Park Formation throughout the study area, except for the west-central region, including northern Hillsborough and Pinellas Counties as well as eastern Polk and northern Manatee Counties. Several gamma-ray logs from wells in the study area also exhibit a peak at depths greater than 350 ft (106.7 m) below the top of the unit. Preliminary analysis attributes this peak to organic content. All major parts of the FAS (the UFA, MFCU and LFA) can include the Avon Park Formation. The “Avon Park permeable zone” (Reese and Richardson, 2008) generally occurs 200 to 400 ft (60.9 m to 121.9 m) beneath the top of the Avon Park Formation in the study area, and is analogous to the “Avon Park highly permeable zone” reported by Hutchinson (1992) for southwestern Florida. Reese and Richardson (2008) map this permeable zone throughout most of the southern half of peninsular Florida, describing it as a thick dolostone unit with interbedded limestone and dominated by fracture porosity that may occur in either the UFA or the LFA. With increasing depth in the Avon Park Formation, interbedded and intergranular evaporites (gypsum/selenite and anhydrite) reduce formation porosity and permeability throughout much of the region. Water-quality data, (Sacks and Tihansky, 1996; Jack Hickey,

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FLORIDA GEOLOGICAL SURVEY 34 personal communication, 2004), geophysical and lithologic evidence indicate that most of the MFCU surface (Plate 59) correlates with the middle to lower carbonates of the Avon Park Formation. In parts of Marion, Osceola and Pinellas Counties, however, the MFCU occurs in the upper third of the unit. In the southern region, a shallower discontinuous MFCU unit occurs within the middle to upper part of the formation (Plate 59). The relation between the Avon Park Formation and the MFCU in eastcentral part of the study area (i.e., the vicinity of southeastern Polk County; Plate 59) requires further data and research. The Avon Park Formation was deposited within a broad, distally steepened carbonate platform (Budd, 2002). The deposition is characterized by peritidal carbonate sediments that may be significantly dolomitized. Highly cyclical deposits in supratidal to shallow subtidal environments are represented in the vertical sediment sequence (Randazzo et al., 1990; Budd, 2002). The sediments reflect repeated short-term changes in relative sea level throughout Middle Eocene deposition documenting transgressive, regressive and open marine to shoreline cycles (Randazzo et al., 1990). Some researchers propose that dolomitization within the Avon Park Formation took place during or proximal in time to deposition (e.g., Randazzo and Hickey, 1978; Cander, 1994). Miller (1986) suggests that thin evaporite beds depos ited during the Middle Eocene may have been formed in a tidal flat or sabkha environment. Ocala Limestone The Upper Eocene Ocala Limestone was first named by Dall and Harris (1892). Puri (1953) later proposed three separate formations: the Inglis, Williston and Crys tal River Formations, which were based upon distinct faunal assemblages. In 1953, Puri elevated the sequence to Group status. Miller (1986) noted that these formations were neither easily recognizable nor mappable and therefore applied the name Ocala Limestone; however, he acknowledged that a twofold division (upper and lower Ocala Limestone) proposed by Applin and Applin (1944) was still in use. Recognizing the biostratigraphic basis of the division on which the Ocala Group was based, Scott (1991) identified the Ocala Limestone as a formation in accordance with the North American Stratigraphic Code. Despite this rather complex history in nomenclature leading to recognition of the unit as a single formation, upper and lower Ocala Limestone lithologies are generally recognized. The lower Ocala Limestone varies from white to light gray and is variably indurated, ranging from a packstone to a grainstone. Where present, dolomite content increases with depth in the Ocala Limestone, especially in the southwestern part of the study area where the base of the unit is often dolomitized (see Avon Park Formation , p. 31, for more details). Gaswirth (2004) also noted this pattern and documented textural end-members within these dolostones: 1) friable, light to medium brown, sucrosic and 2) indurated, dark gray to dark brown, dense, crystalline. The upper part of the Ocala Limestone varies from white to light orange and tends to be more mud-supported (i.e., mudstone to wackestone) and chalky. Mineralogy of the Ocala Limestone unit is predominantly calcite, and to a lesser extent, dolomite. Siliciclastics are rare; however, chert occurs throughout the form ation and is generally more common where the unit occurs at or near land surface. Trace amounts of organics and clay (Green et al., 1995) likely represent postdepositional infilling. Pyrite is also present as a trace mineral, but to a lesser extent than the overlying Suwannee Limestone or underlying Avon Park Formation. Sedimentary structures in the Ocala Limestone include cross bedding, fine laminations and bioturbation. The latter is dominant at the base of the unit in the form of burrows (Loizeaux, 1995). The Ocala Limestone has a diverse fossil assemblage (Figure 13), including Lepidocyclina sp ., Nummulites (Operculinoides) sp . , milliolids, bryozoans, gastropods, mollusks, pelecypods, echinoids (e.g., Eupatagus antillarum ) and Rotularia ( Spirolina ) vernoni .

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BULLETIN NO. 68 35 Figure 13. Selected diagnostic fossils within the Ocala Limestone. Top photo: Eupatagus antillarum ( bar = 2.5 cm; photo courtesy of IP/FMNH). Middle row, left: Nummulites (Operculinoides ) sp. (bar = 1mm; photo courtesy of Jonathan Bryan), right: Rotularia ( Spirolina ) vernoni (bar = 1 cm, photo courtesy of IP/FMNH). Bottom: Lepidocyclina ocalana, (bar = 3 mm); (A) from Cushman (1920), (B) from Rupert (1989). A B

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FLORIDA GEOLOGICAL SURVEY 36 Grainstones of the Ocala Limestone comprise the most permeable zones in the UFA. Porosity within the unit is generally moldic and intergranular with occasional macrofossil molds. Secondary porosity owing to carbonate dissolution is extensive and has greatly enhanced permeability, especially where confining beds are breached or absent (Berndt et al., 1998). Based on analyses of 70 samples, total porosity of the Ocala Limestone averages 39.8 percent (median = 41.0 percent) and ranges from 17.6 percent to 53.5 percent. Of the endmember dolostone lithologies reported by Gaswirth (2004), porosity of the “indurated” type averages 24 percent (n=30) and the “sucrosic” type averages 35 percent (n=28), (Gaswirth et al., 2006). The Ocala Limestone occurs throughout the study area except where locally removed by erosion on the Ocala Platform in the southeastern part of Levy County and southwestern part of Marion County. In southwestern Orange County and northwestern Osceola County, the Ocala Limestone is also absent possibly due to structural offset and erosion. Miller (1986) proposes a graben-like fault system striking along the Polk-Osceola County boundary; however, data presented herein does not confirm its presence. An area of “locally absent” Ocala Limestone (Plate 39) does, however, approximately coincide with Miller’s (1986) fault-bound area. The top of the Ocala Limestone occurs at or near land surface in the northern region (Figure 2) and deepens to approximately -1275 ft (-388.6 m) MSL in the southern region (Plate 39). The thickness of the unit exceeds 400 ft (121.9 m) in Charlotte and Highlands Counties (Plate 40). This lithostratigraphic unit is generally thought to be bound by unconformities (Braunstein et al., 1988; Loizeaux, 1995). Two proposed structural features are significant with regard to the Ocala Limestone. A fault striking northwest in northwestern Polk County is proposed by Carr and Alverson (1959). Vernon (1951) and Stewart (1966) present contour maps of the “Inglis” (i.e., basal Ocala Limestone) suggesting local offset in the same area with the shallower “Inglis” sediments toward the northeast. This offset is consistent with Carr and Alverson’s (1959) proposed fault. Although local thickness variations of the Ocala Limestone in this area are generally consistent with the proposed fault, the present study does not have sufficient well control to confirm the hypothesis. A fault proposed by Winston (1996) that trends northwest across Charlotte Harbor may be related to the deepening and thickening of the Ocala Limestone in this area. Contact relationships between the Ocala Limestone and Avon Park Formation are discussed under Avon Park Formation, p. 31. In the northern and central regions, the boundary between the Ocala Limestone and the overlying Suwannee Limestone is usually not difficult to distinguish. Not only is the gamma-ray character different (Figure 10), but the uppermost Ocala Limestone is generally “cleaner” (i.e., significantly less non-calcitic material) finer-grained and more skeletal than the overlying unit. In some cases, Ocala Limestone lithoclasts are found at the base of the Suwannee Limestone (Loizeaux, 1995). Moreover, the fossil assemblage differs significantly, with the disappearance of Lepidocyclina ocalana and the appearance of Fallotella sp. (Suwannee Limestone) shallower in the section. There are, however, areas where the two units are difficult to distinguish. The transition from Ocala Limestone to Suwannee Limestone can be gradational toward the south, showing some evidence of interbedding and thus a possible conformable contact. Moreover, some areas contain basal Suwannee carbonates that range from fine-grained grainstones to mudstones, which can be difficult to distinguish from the underlying, sometimes altered, chalky mudstones and wackestones of the upper Ocala Limestone. Torres et al. (2001) and BrewsterWingard et al. (1997) have also noted that the boundary is often difficult to pinpoint and suggest that foraminifera are often useful to distinguish the units. Gamma-ray logs for the Ocala Limestone consistently exhibit very low gamma-ray activity (low, background-level count rates) and relatively fewer peaks than the overlying and underlying formations (Figure 10). In cases where the Ocala Limestone is dolomitized, the

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BULLETIN NO. 68 37 gamma-ray logs may exhibit a slightly higher and more sporadic signature (Arthur et al., 2001a). Many peaks in the gamma-ray logs for this unit correlate with the presence of trace organics or pyrite (e.g., W-12640 [ROMP 59]; Plate 21 and 32). In peninsular Florida, Ocala Limestone deposition is interpreted to have occurred on a homoclinal distally steepened carbonate ramp in shallow (probably less than 10 m [32.8 ft]) subtidal to intertidal, somewhat high-energy, open marine environment (Randazzo et al., 1990; Cander, 1994; and Loizeaux, 1995). The Ocala Limestone represents a more constant and stable depositional environment than the underlying Avon Park Formation (Randazzo et al., 1990). Specifically, deposition of the Ocala Limestone occurred during a long-term eustatic high stand representing an overall transgressive sequence of sedimentation with shoreline progradation (Randazzo et al., 1990; Loizeaux, 1995). The lower Ocala Limestone represents a deepening upward sequence with the sediments becoming muddier through time and then shoaling in the uppermost Ocala (Randazzo et al., 1990). This appears to coincide with the post-middle Eocene marine transgressions followed by a fall in eustatic sea level at the end of late Eocene (Loizeaux, 1995). Oligocene Series Suwannee Limestone The Lower Oligocene Suwannee Limestone was first identified by Cooke and Mansfield (1936). This formation ranges from light-gray to white, variably moldic packstones and grainstones. Carbonate grains are generally miliolids and peloids. Small amounts of sand (< 3 percent) and clay generally occur within the uppermost part of the unit when overlain by Hawthorn Group sediments. South of the study area, however, Missimer (2002) reports local sand beds in the Suwannee Limestone. Trace amounts of pyrite and organics (finely disseminated and as laminations) also occur throughout this formation (Arthur et al., 2001b; Price, 2003). The Suwannee Limestone is also variably dolomitized. For example, Green et al., (1995) noted a relatively c onsistent dolostone or dolomitic limestone bed (10-20 ft thick [~3-6 m]) occurring within the lower third of the unit in the central part of the study area. Chert is present throughout the unit, especially within the updip part of the unit. In Hernando County, for example, partial silicification of the limestone is observed, leaving echinoids in their original calcite form. Sedimentary structures include cross bedding and bioturbation (Budd, 2002). Porosity types include moldic and intergranular. Measured total porosity, based on analysis of 29 samples, averages 36.3 percent (median = 37.1 percent) and ranges from 2.3 percent to 55.8 percent. Fossils within the Suwannee Limestone include mollusks, gastropods, echinoids (most commonly the index fossil Rhyncholampus gouldii ), abundant miliolids and other benthic foraminifera including Fallotella (Dictyoconus) cookei, Discorinopsis gunteri (Figure 14) and Fallotella (Coskinolina) floridana (Figure 12). For the most part, the Suwannee Limestone unconformably overlies the Ocala Limestone and is unconformably overlain by Hawthorn Group sediments; however, there exists some question regarding the lateral extent of both unconformities. The contact between the subjacent Ocala Limestone and the Suwannee Limestone can be locally gradational, showing some evidence of interbedding. In some areas, the lower Suwannee Limestone increases in carbonate mud content, which can be difficult to distinguish from the sometimes chemically weathered, chalky upper Ocala Limestone. Torres et al. (2001) and Brewster-Wingard et al. (1997) have also noted that the boundary is often difficult to pinpoint. These researchers, as well as the authors of this report, suggest that foraminifera are often useful to distinguish the units. The upper contact of the Suwannee Limestone is locally gradational with the overlying Tampa Member (Arcadia Formation) in northeastern Hillsborough and Pinellas Counties. Researchers faced with the difficulty of making formation picks in this area have come to informally refer to this transitional zone as “SuwTampaHaw” (Tom Scott, personal communication, 2004). The Suwannee Limestone is also locally overlain by green clays

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FLORIDA GEOLOGICAL SURVEY 38 Figure 14. Selected diagnostic Suwannee Limestone fossils. Top row left: Fallotella ( Dictyoconus ) cookei (bar = 1 mm; from Rupert, 1989), right: Rhyncholampus gouldii (bar = 2.5 cm, photo courtesy of Sean Roberts). Bottom row – left: Discorinopsis gunteri (bar = 2 mm; Cooke, 1945), right: milliolid (bar = 1 mm; photo courtesy Jonathan Bryan). comprising the base of the Tampa Member (Arcadia Formation) in parts of northern and central Pinellas County, south-central Hillsborough County and eastern Polk County. In other areas, lack of phosphate sand in the Suwannee Limestone distinguishes it from overlying phosphatic (i.e., non-Tampa Member) Hawthorn Group sediments. South of the study area, however, Suwannee Limestone carbonates include minor occurrences of blackened (possibly francolite) discontinuity surfaces (Missimer, 2002). The northern extent of the Suwannee Limestone occurs in Citrus County based on isolated outcrops and discontinuous borehole data. The approximate northern limit of laterally continuous Suwannee Limestone, however, occurs in southernmost Citrus County (Plates 41 and 42). In the eastern region, the subcrop limit occurs beneath the Lake Wales Ridge. In Highlands County, the eastern extent of the unit is uncertain and denoted with a dashed line (Plates 41 and 42). Two wells east of the line contain limited thicknesses of the Suwannee Limestone; however, nearby wells deep enough to have encountered the unit do not contain it. This suggests the two wells represent outliers. Maximum elevation of the unit exceeds 75 ft (22.9 m) MSL in parts of Hillsborough and Polk Counties as well as along the Brooksville Ridge, while in the southern region, depths exceed -825 ft (-251.5 m) MSL (Plate 41). Maximum thickness of the Suwannee Limestone in the study area exceeds 450 ft (137.2 m) in southcentral Charlotte County (Plate 42). Evidence supporting previously identified

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BULLETIN NO. 68 39 faults in the Suwannee Limestone exists to some degree within two areas. The feature most supported by the data presented herein is an inferred northwest-striking fault in northwestern Polk County (Figure 3). The Suwannee Limestone thickness map (Plate 42) indicates an abrupt change in thickness; wells reflecting more than 100 ft (30.5 m) of the unit are proximal to wells that contain no Suwannee Limestone even though the wells are deep enough to have encountered the unit (assuming similar regional dip). The strike and polarity of this particular feature, indicated as an inferred fault on Plate 41 and 42, roughly agrees with a fault proposed by Pride et al. (1966). Northeast of the fault, the Suwannee Limestone is reported to occur as exposed remnant boulders in Sumter County (Campbell, 1989). A second inferred fault may occur along the updip limit of the Suwannee Limestone in northeastern Hernando County (Figure 3). Vernon (1951) reports a fault intersecting the “Inglis Member” in the area, with the upthrown side to the northeast. Data represented in Plates 41 and 42 support the location and polarity of Vernon’s (1951) fault for the Suwannee Limestone. Thicknesses greater than 50 ft (15.2 m) terminate along the northeastern subcrop limit of the unit (Plate 41 and 42). In the Charlotte Harbor area, the “North Port” fault (Winston, 1996) may have affected the Suwannee Limestone surface and thickness, similar to that of the Ocala Limestone and Avon Park Formation. Other faults and lineaments are reported in this area (Hutchinson, 1991; Winston, 1996; Michael Fies, personal communication, 2007) suggesting a complex geologic setting. The Suwannee Limestone is characterized by a gamma-ray log response (i.e., activity) that is generally more variable within the lower half of the unit (e.g., Plate 11 and 12; Figure 10). Relative to the Ocala Limestone, it has an overall higher background rate and exhibits much more variability. This variability is likely due to higher amounts of dolomite, organic material and other non-calcitic constituents in the Suwannee Limestone relative to the Ocala Limestone. Although the gamma-ray log is generally useful for providing corroborative evidence for the lithostratigraphic boundary between the Eocene Ol igocene carbonates, use of the logs for determination of the upper boundary of the Suwannee Limestone is not always as straightforward. For example, where the Tampa Member (Arcadia Formation) is in contact with the Suwannee Limestone, gammaray signatures for the two units are quite similar, both in their background count rates and distribution of peaks (e.g., Plate 31, W-15204 [TR14-2] and Plate 33, W-16740 [ROMP 39]). A generally consistent pattern in the Suwannee Limestone gamma-ray logs, especially for wells in Gulf-coastal counties, is the presence of a 50to 1 00-ft (15.2 to 30.5 m) thick interval of high gamma-ray activity within the central to lower parts of the Suwannee Limestone. This interval varies in thickness and depth and apparently does not correlate with a given stratigraphic horizon. Inspection of lithologic logs suggests that this high gammaray activity zone is associated with dolomite and/or minor organic content. The Suwannee Limestone, where present, comprises most of the FAS surface; exceptions being where hydraulic continuity exists between the Tampa Member (Arcadia Formation) and Suwannee Limestone in Pasco, Pinellas, most of Hillsborough and northern Manatee Counties (Figure 8). Along the updip limit of the Tampa Member in Pasco County, the top of the FAS includes the Tampa Member (where present) and the Suwannee Limestone (Figure 8). Grainstones within the Suwannee Limestone are among the most permeable zones in the UFA. Suwannee Limestone deposition occurred in shallow open marine to peritidal environments on the Florida Platform (Cander, 1994) until the Late Oligocene sea-level low stand (Hammes, 1992). During deposition of the unit in the study area, the Georgia Channel System (Huddlestun, 1993) acted as a barrier to a southward influx of clastic sediments from the Appalachian Mountains. Deposition of the predominantly skeletal lithologies was cyclic and controlled by the pre-existing topography as well as fluctuating sea level. Restricted marine facies and skeletal shoal facies developed on previous highs and deeper subtidal facies occurred in the lows. Hammes (1992) describes the Suwannee

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FLORIDA GEOLOGICAL SURVEY 40 Limestone as three megacycles each composed of several shallowing upward cycles: 1) the outer ramp characterized by skeletal-rich, grain supported to muddy, open-marine, shallow and deep-ramp facies, 2) shallow ramp facies – composed of wave dominated skeletal banks and shoal complexes and shallow and deep subtidal lagoonal deposits, and 3) restricted marine – deposition in a restricted marine, brackish lagoon and mud-rich tidal flat environment. Oligocene-Pliocene Series Hawthorn Group Hawthorn Group sediments range in age from mid-Oligocene (Brewster-Wingard et al., 1997) to Early Pliocene (Scott, 1988; Covington, 1993; Missimer et al., 1994) and generally consist of phosphatic siliciclastics (sands, silts and clays) and carbonates. Trace amounts of pyrite occur throughout the Hawthorn Group section in southwestern Florida (Lazareva and Pichler, 2007). In the study area, the Hawthorn Group consists of the Arcadia Formation, the Peace River Formation and undifferentiated sediments, all of which generally lie unconformably above the Suwannee Limestone and unconformably beneath undifferentiated Pliocene and younger sands, shells and clays. Benthic foraminifera characteristic of the Hawthorn Group include Archaias sp., Sorites sp., Amphistegina lessoni and Cassigerinella (Cassidulina) chipolonsis (Figure 15). Predominant formational members of the Hawthorn Group present in the study area include the Tampa and Nocatee Members (Arcadia Formation) and the Bone Valley Member (Peace River Formation). The extent of all Hawthorn Group sediments (Plate 43) generally includes those areas where undifferentiated confining beds of the IAS/ICU (Plate 56) are present beyond the mapped extent of the Arcadia and Peace River Formations (Plates 45 and 51, respectively) such as Marion County, Pinellas County and central Pasco County. The maximum observed thickness of the Hawthorn Group exceeds 825 ft (251.5 m) in south-central Charlotte County (Plate 44). The Hawthorn Group was deposited in a shallow marine to nonmarine fluvial and deltaic environment that prograded over the older carbonate platform (Scott, 1988; Ward et al., 2003). Similar to other units mapped in this study, the top of the Hawthorn Group can demonstrate variable local relief, as exhibited by its irregular erosional a nd karstic surface (Berndt et al., 1998). Based on mineralogy of Hawthorn Group sediments, incipient stages of phosphogenesis occurred during the Late Oligocene during deposition of the lower Arcadia Formation (Brewster-Wingard et al., 1997). Sea-level fluctuations strongly influenced deposition and exerted a major control on phosphogenesis and sedimentation (Riggs, 1979a, 1984; Compton et al, 1993). During sea-level transgressions a large part of the Florida platform was submerged. Meandering of the Gulf Stream resulted in upwelling over the platform, which increased organic productivity and enhanced phosphogenesis in the shallow waters of the shelf (Compton et al, 1993). Maximum phosphorite precipitation is thought to have occurred in shallow-water coastal and nearshore shelf platforms or other submarine topographic highs (Riggs, 1979a). Sealevel fluctuations and ocean currents facilitated transport, deposition and concentration of phosphate grains (Scott, 1988, 1992b). Primary depositional features such as graded bedding and cross beds provide evidence of this high-energy depositional environment (Scott, 1988). The height of phosphate deposition a nd reworking was synchronous with Peace River Formation deposition (Middle to Early Pliocene). Arcadia Formation The Upper Oligocene (Brewster-Wingard et al., 1997) to Middle Miocene Arcadia Formation is comprised of a yellowish gray to white, variably sandy (quartz and phosphorite) carbonate with interbeds of siliciclasticdominant sediments. Although limestone is present, dolostones are most common, ranging in grain size from microcrystalline to medium sand, with the more coarse material being sucrosic. Minor clays and chert beds (some comprised of silicified clay) also occur (Upchurch et al., 1982; Scott, 1988). Porosity types include intergranular and moldic.

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BULLETIN NO. 68 41 . Figure 15. Diagnostic foraminifera in Hawtho rn Group units. Upper left bar = 0.1 mm; upper right bar = 1 mm; bottom row, bar = 0.5 mm. Measured total porosity of 25 Arcadia Formation samples averages 34.1 percent, with a median value of 32.4 percent and a range from 12.4 percent to 54.5 percent. The updip limit of the unit occurs in northern Pasco and Polk Counties where maximum elevations exceed 90 ft (27.4 m) MSL (Plate 34 and 45). The top of the Arcadia Formation occurs at depths exceeding -270 ft (-82.3 m) MSL beneath the Lake Wales Ridge in the southeastern part of the study area. The unit ranges in thickness to greater than 750 ft (229 m) in south-central Charlotte County (Plate 46). Sporadically throughout much of the central and southern regions, the Arcadia Formation (undifferentiated) is observed below the Tampa and Nocatee Members. In several wells, the contacts between the Tampa and Nocatee Members and the underlying Arcadia Formation (undifferentiated) are gradational. The Arcadia Formation is unconformably overlain by the Peace River Formation (where present); however, apparent gradational contacts between these two units are locally observed. In general, the Arcadia Formation comprises the most permeable parts of the IAS/ICU in the study area (see IAS/ICU , p. 57, for more details). In addition, the uppermost part of the FAS is comprised of the Tampa Member where it is in hydraulic connection with the subjacent

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FLORIDA GEOLOGICAL SURVEY 42 Suwannee Limestone (Figure 8). Gamma-ray activity in the Arcadia Formation is distinctive, with strong gamma-ray peaks characterizing the upper undifferentiated part of the unit (e.g., W-16784 [ROMP 33], Plates 16 and 37; Figure 10). Lithostratigraphic members within and below the formation are characterized by significantly weaker gammaray responses. For example, where the undifferentiated Arcadia Formation overlies the Suwannee Limestone, the gamma-ray response for the older unit is often contrastingly low in gamma-ray activity (e.g., W-15683 [TR 3-3], Plate 19 and W-15333 [TR 2-1], Plates 19, 28 and 37). Although the high gamma-ray activity sequence in the Arcadia Formation is distinctive, it is not always useful as a diagnostic tool for identifying the upper formational boundary. Phosphate lag deposits locally comprising the base of the Peace River Formation have gammaray peaks as high as that of the Arcadia Formation. Deposition of the Arcadia Formation is somewhat unique owing to its composition of mixed carbonate and silicic lastic sediments. In most depositional environments, an influx of siliciclastic sediments usually inhibits the production of carbonates. During the Oligocene, siliciclastics began to deposit along the Florida Platform (Hammes, 1992; Missimer, 2002). This influx of siliciclastics, during low sea-level stands, began to slowly bypass the Georgia Channel System (Huddlestun, 1993) as it filled. By Late Oligocene the lower part of the Arcadia Formation was being deposited and a more continuous influx of quartz sand was occurring (Missimer and Ginsburg, 1998). These siliciclastics were transported south several hundred kilometers to the southern part of the Florida carbonate platform by longshore currents (Scott, 1988; Missimer and Ginsburg, 1998). The rate of siliciclastic transport was initially episodic and sufficiently low to minimize interruption of the production of carbonates. Differences in shoreline positions caused by fluctuating sea levels allowed siliciclastics to mix over a broad area. Mixing of the carbonates and siliciclastics was achieved by tidal transport, storms, longshore currents, bioturbation and aeolian processes (Scott, 1988; Missimer and Ginsburg, 1998; Missimer, 2002). Missimer and Ginsburg (1998) list three important factors that allowed the homogenized, co-deposition of Arcadia Formation carbonates and siliciclastics to occur: 1) a relatively slow rate of siliciclastic sediment influx, 2) the lack of mud or clay, and 3) marine transport without river or stream transport. Freshwater input would have caused an increase in finer-grained siliciclastics (e.g., silts and clays), increased turbidity and decreased salinity, all of which would have diminished carbonate production. Noteworthy topographic features occur along the surface of the Arcadia Formation. In the Tampa Bay area, interpreted seismic data indicate subsurface relief of up to ~197 ft (60 m; Hine et al., in press). These features are attributed to “spatially restricted, semi-enclosed, siliciclastic-filled karst” that may coalesce into larger collapse systems (Hine et al., in press). A karst basin identified in their study due south of the Pinellas County peninsula in Tampa Bay correlates well with a trough extending northward into the peninsula (Plate 45; see also Tampa Member surface map, Plate 49). Along the southern part of the Lake Wales Ridge, the Arcadia Formation deepens sharply (Plate 45). This elongate depression (or trough) also occurs in the overlying Peace River Formation (Plate 51). Although topographic relief of the troughs are similar (~175 to ~200 ft; ~53 to ~61 m), the Arcadia Formation exhibits little evidence of thinni ng, unlike the Peace River Formation (Plate 52). Periods of erosion (scouring?) or non-deposition owing to sea-level fluctuations and paleo-ocean currents are likely factors contributing to the origin of this trough. Miocene-Pliocene structural control of the feature is not indicated by the thickness of either formation. The thickness of post-Hawthorn Group sediments (see Plate 55 for approximation) suggests that the trough may have become a depoaxis for PliocenePleistocene siliciclastics. A third significant topographic feature occurs in south-central Charlotte County, where the surface of the Arcadia Formation deepens to more than 200 ft (60.9 m) MSL and notably thickens to more than 700 ft (213 m; Plates 45

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BULLETIN NO. 68 43 and 46). Locations of depocenters within subjacent lithostratigraphic units occur in roughly the same locale: the Ocala Limestone, Suwannee Limestone and Hawthorn Group deepen in this area (Plates 39, 41 and 43, respectively), and the units thicken as well (Plates 40, 42 and 44, respectively). This basin is also observed in the surface of the Avon Park Formation (Plate 38); however, due to lack of well control, Miller’s (1986) Middle Eocene maps do not reflect this feature. These observations suggest that the area experienced continued subsidence and infilling from Middle Eocene through at least Late Miocene. Alternatively, the apparent depocenters may have structural control owing to the proximity of the “North Port” fault (Winston, 1996). Nocatee Member The Upper Oligocene (Brewster-Wingard et al., 1997) Nocatee Member of the Arcadia Formation is an interbedded sequence of quartz sands, clays and carbonates all containing variable amounts of phosphate (Scott, 1988) that generally average five percent but locally can reach ten percent or more. The unit is predominately silicicla stic and generally interbedded with lo wer percentages of carbonate. Original macrofossil material is not common in this unit; however, fossil molds of mollusks, algae and corals are observed. Diatoms are commonly found within the clay units. Porosity of the Nocatee Member is generally intergranular, with highly variable permeability. Total porosity of five core samples from the Nocatee Member average 27.5 percent (median = 24.7 percent) and range from 20.4 percent to 35.4 percent. The subcrop extent of the Nocatee Member includes west-central Polk County south to Charlotte and Glades Counties and extends as far west as central Sarasota County. The northeastern limits of the unit are generally well defined and comprise a stratigraphic pinchout (e.g., Polk and Highlands Counties); however, the southwest extent is more subjective as the unit grades laterally into the undifferentiated Arcadia Formation, or locally into the Tampa Member. In an area extending south from southwestern Polk County, the Nocatee Member is conformably overlain by the Tampa Member of the Arcadia Formation. Elsewhere in the study area, the upper and lower limits of the Nocatee Member are gradational into the undifferentiated Arcadia Formation. The top of the Nocatee Member ranges in elevation from greater than 50 ft (15.2 m) MSL in west-central Polk County to depths exceeding -600 ft (-183 m) MSL in the southeastern part of the study area (Plate 47). Although the Nocatee Member ranges in thickness to more than 240 ft (73.2 m), it averages approximately 75 ft (22.9 m) thick (Plate 48). Gamma-ray activity within the Nocatee Member is generally less than or equal to that of the overlying Hawthorn Group units (i.e., Tampa Member and Arcadia Formation; e.g., Figure 10 and Plate 26). Where the Nocatee Member is underlain by (and generally grades into) the undifferentiated Arcadia Formation, gamma-ray logs are not as useful in distinguishing between the two units. On the other hand, where the Nocatee Member overlies the Suwannee Limestone, the gamma-ray activity can be very useful for distinguishing the two units. Although most of the Nocatee Member correlates with the IAS/ICU, this lithostratigraphic unit is hydraulically connected to the UFA within part of DeSoto County (Figure 8) and thus locally comprises the uppermost UFA in those areas. The Nocatee Member was deposited on the southeast edge of the carbonate bank prior to and during deposition of the Tampa Member. The Nocatee represents a higher energy, more open near-shore environment and grades westward into a very sandy facies of the undifferentiated Arcadia Formation and northwestward into the carbonate facies of the Tampa Member (Scott, 1988). Tampa Member The Upper Oligocene to Lower Miocene (Brewster-Wingard et al., 1997) Tampa Member of the Arcadia Formation is white to yellowish gray in color and ranges from a wackestone to

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FLORIDA GEOLOGICAL SURVEY 44 packstone with varying amounts of quartz sand and clay (Scott, 1988). Minor phosphate (less than 3 to 5 percent), dolomite and chert (siliceous limestone, silicified corals; see also Upchurch et al., 1982) are also observed. Fossil molds of foraminifera, mollusks, gastropods and algae are all common within the Tampa Member (Scott, 1988). Pinkish gray to light olive gray dolostones also occur with a similar accessory mineral assemblage and fossil assemblage as the limestones. Thin sand and clay beds can be found sporadically within the unit (Scott, 1988). Porosity of the Tampa Member is generally intergranular and moldic, with measured total porosity values (17 samples) ranging from 10.4 percent to 49.6 percent, averaging 32.3 percent (median value = 33.6 percent). The subcrop limit of the Tampa Member extends from Pasco County to the northernmost part of Charlotte County and eastward into the western half of Polk, DeSoto and Hardee Counties (Plate 49 and 50). The top of the Tampa Member ranges from more than 100 ft (30.5 m) MSL in Pasco County to deeper than 350 ft (-107 m) MSL in Sarasota County (Plate 49) and exhibits variable thickness. The maximum observed thickness of the Tampa Member is 292 ft (89.0 m) (Plate 17; W-14882 [TR 6-1]); however, some would propose that the lower Tampa Member in this well is more characteristic of the undifferentiated Arcadia Formation. In the northern third of its extent, the Tampa Member overlies the Suwannee Limestone and the contact appears to be locally conformable. In Pinellas and northwest Hillsborough Counties, for example, samples have been informally referred to as “SuwTampaHaw” due to the subtle transition between the units. In the central and southern regions, this unit overlies the Arcadia Formation (undifferentiated), or the Nocatee Member of the Arcadia Formation. In many wells, the transition between the Tampa Member and the underlying Arcadia Formation is gradational, with phosphorite content increasing with depth. The Tampa Member is conformably overlain by the Arcadia Formation (undifferentiated) in many areas (e.g., Plate 14); however numerous exceptions exist. In parts of Pasco and northern Hillsborough Counties, the unit is unconformably overlain by UDSC or undifferentiated clay-rich Hawthorn Group sediments. East of this area, the Tampa Member is unconformably overlain by the Peace River Formation. Toward the east and south, the Tampa Member facies grades laterally into the Arcadia Formation. In Sarasota County, the unit appears to grade laterally into the Nocatee Member as it becomes increasingly more sandy. Scott (1988) also reports this lateral facies change in northern Hardee County. The Tampa Member generally exhibits variable gamma-ray activity (Figure 10; Arthur et al., 2001a) that limits the value of this log to discern unit boundaries. For example, when underlain by the Arcadia Formation (undifferentiated), the Nocatee Member or the Suwannee Limestone, it is difficult to distinguish these units from the Tampa Member based on gamma-ray activity. On the other hand, where the Tampa Member is overlain by the Arcadia Formation, the two units are usually readily distinguishable due to higher gamma-ray activity in the undifferentiated Arcadia Formation. Along the updip erosional pinchout of the Tampa Member, where it forms an irregular subcrop contact with the Suwannee Limestone (Plate 49), the top of the FAS generally coincides with the uppermost carbonate unit occurrence (Figure 8). In the west-central part of the study area, the Tampa Member is the uppermost lithostratigraphic unit within the FAS (Figure 8); however, based on lithologic and hydrologic data from wells in south-central Hillsborough County, the Tampa Member is locally hydraulically separated from the Suwannee Limestone and is therefore considered part of the IAS/ICU (Figure 8). This latter hydrogeologic setting occurs locally in northern Pinellas County as well. The depositional environment of the Tampa Member was that of a quiet water lagoon, much like present day Florida Bay (King, 1979). An influx of siliciclastics nearly devoid of phosphorite distinguishes Tampa Member deposition from older and younger Hawthorn Group units in the stratigraphic section.

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BULLETIN NO. 68 45 “Venice Clay” The Venice Clay is an informal unit originally considered part of the lower Tamiami Formation (Pliocene); however, microfossil data suggest an age of Early to Middle Miocene (Scott, 1993). Scott (1992b) suggests informal placement of the Venice Clay in the upper half of the Arcadia Formation based on subjacent and suprajacent lithologies and preliminary fossil evidence. The Venice Clay is gray-green magnesium-rich clay, variably dolomitic with minor amounts of quartz sand and silt. The unit rarely contains phosphorite and becomes increasingly silty toward its upper and lower contacts (Campbell et al., 1993). The subcrop extent of the Venice Clay includes Sarasota County and adjacent parts of Manatee, DeSoto and Charlotte Counties; the unit may also extend offshore (Barr, 1996). Based on data collected in the present study, the top of the unit generally occurs between -10 ft MSL and -100 ft MSL (-3.1 to -30.5 m). Barr (1996) reports that thickness of the unit ranges up to approximately 30 ft (9.1 m). Gamma-ray activity is diagnostically very low for this unit, (note clay beds near top of the Arcadia Formation in W-15683 [TR 3-3]; Plate 19), suggesting the mineral assemblage does not include abundant potassium-rich illite-group clays. The Venice Clay was likely deposited in a quiet shallow water marine environment possibly an estuary (Tom Scott, personal communication, 2004). The Venice Clay acts as a confining unit in the upper part of the IAS/ICU. Specifically, Barr (1996) suggests that it comprises the confining unit below “permeable zone 1.” Owing to its limited thickness and aerial extent, as well as recent mapping by Barr (1996), the Venice Clay is not mapped in the present study. Peace River Formation The Middle Miocene to Lower Pliocene (Scott, 1988; Covington, 1993) Peace River Formation is comprised of yellowish gray to olive gray, interbedded sands, clays and carbonates with the siliciclastic component being dominant (Scott, 1988). The relative abundance of carbonate beds generally increases toward the south, especially near the base of the unit. Variable amounts of phosphate sand and gravel are interspersed throughout the unit; however, they are most common within the uppermost beds. The Peace River Formation contains a diverse fossil assemblage of marine and terrestrial fauna (e.g., shark teeth and vertebrae, ray spines, horse teeth, dugong and whale ribs, etc.), especially within the Bone Valley Member (Figure 16). Porosity types in the formation are generally intergranular, except in the carbonate-rich zones, where moldic porosity is also present. Only two total porosity analyses of Peace River Formation samples have been measured in this study. The results, 34.4 percent and 39.4 percent, should not be taken as representative of the unit given its diverse lithology. Lithologic characteristics of the Peace River Formation are generally c onsistent; however, the carbonate component becomes more prevalent from north to south as the unit thickens. Throughout most of its extent, the Peace River Formation does not contain shell material, with possible exception of southeast DeSoto County, where barnacles are present within the unit (Green et al., 1999). These barnacle-rich sediments may be the equivalent of “unit 11” from Petuch (1982). Missimer (2001) reports shell material in the Peace River Formation south of Charlotte County. In the same region, calcareous nannofossils occur in the unit (Covington, 1993). The Peace River Formation generally has an unconformable contact with the underlying Arcadia Formation. In an isolated area in northeast-central Hillsborough County, the Peace River Formation directly overlies the Tampa Member (Plates 13 and 33). The Peace River Formation also has an unconformable contact with the underlying Ocala Limestone in northern Polk County (Plates 11 and 34; W-14389 [ROMP 76]). In this area, reworked Peace River Formation sediments may occur unconformably above the Avon Park Formation where the Ocala

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FLORIDA GEOLOGICAL SURVEY 46 Figure 16. Assemblage of typical Bone Valley Me mber fossils. Clockwise from upper left: ray spines, shark vertebra, shark teeth, horse teeth, alligator tooth in matrix, (nickel for scale) dugong rib, mammoth tooth and bone fragment. Backgro und is a slab of Avon Park Formation dolostone with Thalassodendron sp. carbonized impressions. (Photo credit: Jon Arthur, FDEP-FGS). Limestone is locally absent (Plate 39). Delineation of the Peace River – Arcadia Formation contact is problematic in some localities. In many cores, the two units appear to be conformable, with phosphate-rich siliciclastics grading with depth to more siliciclastic-interbedded carbonates containing generally finer-grained and less abundant phosphorite. Thickness of this transition zone may exceed tens of feet. With increasing depth, Arcadia Formation lithologies become more dominant. In such cases, the lower contact of the Peace River Formation is estimated based on sedimentary structures as well as a best approximation of where the overall lithologic sequence becomes more carbonate dominant. In contrast to the locally gradational contacts, other areas provide strong evidence of an unconformity, where a phosphatic rubble zone occurs at the base of the Peace River Formation (Scott, 1988). Post-Pliocene/Miocene sediments disconformably overlying the Peace River Formation in the study area are comprised of fossiliferous sands, clays and shell beds with variable amounts of limestone and reworked phosphorite (e.g., Plate 11, W-14389 [ROMP 76] and Plate 13, W16576 [ROMP DV-1]). The contact of these sediments with the Peace River Formation can be difficult to determine because of lithologic similarities (e.g., clays and phosphorite), especially where the uppermost beds of the Peace River Formation have been leached by groundwater, giving the sediments an appearance similar to that of some postHawthorn Group lithologies. In addition, it can be very difficult to distinguish Peace River Formation sediments from those of reworked Peace River sediments (e.g., post-Hawthorn Group undifferentiated sands and clays) when studying cores (the distinction is extremely difficult to impossible when evaluating cuttings).

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BULLETIN NO. 68 47 Similar to basal Peace River Formation lag deposits, reworked Miocene-Pliocene sediments may also yield a phosphate lag deposit at the base of overlying (e.g., post-Hawthorn Group) sediments. Units superjacent to the Peace River Formation include the Tamiami, Ft. Thompson and Caloosahatchee Formations. In most cases, the Peace River Formation is readily distinguished from these overlying sand/shell/carbonate lithofacies. Lateral facies transitions of the Peace River Formation are most evident along the northwestern extent of the unit in Hillsborough and Polk Counties (Plate 51). In this area, sediments characteristic of the Peace River Formation grade into clay-rich and phosphatepoor sediments of the undifferentiated Hawthorn Group (e.g., Plate 13). Maximum elevations of the Peace River Formation occur in the vicinity of the Polk Upland and Lakeland Ridge, where the unit exceeds 125 ft (38.1 m) MSL (Plate 51). The maximum observed depth of the Peace River Formation exceeds -200 ft (-60.9 m) MSL along the Lake Wales Ridge. Thicknesses range to over 120 ft (36.6 m) along the southeastern third of the unit’s mapped extent (Plate 52). Gamma-ray activity in the Peace River Formation is highly variable. In some areas, due to the high-phosphorite content in the sediments, strong gamma-ray peaks are readily observed in contrast to lower gamma-ray activity of the Arcadia Formation (e.g., W-16576 [ROMP DV1], Plate 33). The opposite occurs as well, where gamma-ray activity in the Peace River Formation is lower than that of the Arcadia Formation (Figure 10). Where the Peace River Formation lies above Eocene carbonates, the difference is also pronounced, with the younger unit exhibiting a stronger gamma-ray signal (Plate 20). In many wells, a lack of gamma-ray contrast between the Peace River Formation and the Arcadia Formation is observed (W-16740 [ROMP 39], Plate 33). In wells where the base of Peace River Formation contains a reworked phosphate lag deposit, a characteristically strong gamma-ray peak is observed (e.g., W-15938, Plate 22). The unit may also be overlain by a similar lag deposit with in undifferentiated postHawthorn Group sediments. The Peace River Formation is a regional confining to semi-confining lithostratigraphic unit within the upper part of the IAS/ICU. North of central Hillsborough and Polk Counties, the Peace River Formation and undifferentiated Hawthorn Group sediments comprise a low-permeability confining to semiconfining facies of the IAS/ICU. South of this region, permeable, wate r-producing zones exist within interlayered carbonate lenses (e.g., Ryder, 1985, Torres et al., 2001). In some areas, the uppermost sediments of the Peace River Formation are in hydraulic connection with overlying sands due to a low-to-absent clay content (e.g., Plate 17, W-14382 [ROMP 23]). As a result, the Peace River Formation may comprise the lower part of the SAS. Clay-poor sediments occur within the uppermost Peace River Formation in eastern Sarasota County and western Manatee County (Tom Scott, personal communication, 2006). The Middle Miocene – Lower Pliocene Peace River Formation sediments characterize a complex depositional environment strongly influenced by sea-level fluctuations (Missimer et al., 1994). The northern extent of the unit was deposited in a shallow marine, deltaic to brackish water environmen t while further south open marine conditions pr evailed (Scott, 1988). Carbonate deposition in the unit was periodically restricted by a flood of siliciclastics from the north and a rise in sea level (Scott, 1988). Missimer (2001) suggests that the Peace River Formation immediately south of the study area was deposited in a variety of depositional environments ranging from inner ramp to deltaic to beach and can be explained by shoaling upward or lateral accretion of sediment. Sealevel transgressions or highstands appear to favor phosphogenesis, while reworking of the sediments during sea-level regressions or lowstands concentrate the phosphorite (Compton et al., 1993). Phosphorite concentrations are considered economic ore deposits in the central region and are locally mined.

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FLORIDA GEOLOGICAL SURVEY 48 Bone Valley Member The Middle Miocene to Lower Pliocene (Webb and Crissinger, 1983) Bone Valley Member of the Peace River Formation has a limited areal extent, centered in southwestern Polk County (Plate 53). It occurs in the Central Florida Phosphate District which is among the world’s largest economic phosphorite deposits (Freas and Riggs, 1968). Due to mining, most of the Bone Valley Member sediments have been removed. Although similar in lithology to the Peace River Formation, the Bone Valley Member contains greater amounts of phosphorite (more than 30 percent by volume) that is coarser-grained, ranging up to gravel-size nodules. Phosphorite occurs as carbonatefluorapatite (francolite) nodules, peloids, fecal pellets, intraclasts and grain coatings. Some pebble-sized grains show evidence of reworking, boring structures and multiple stages of phosphatization. The non-phosphorite component of the Bone Valley Member is comprised of quartz sand with clay (e.g., palygorskite and sepiolite; Scott, 1988) generally exceeding 20 percent by volume. Carbonate beds are not present; however limestone and dolostone cobbles and larger fragments are observed (Tom Scott, personal communication, 2005). An extremely diverse fossil assemblage exists within the unit (Webb and Crissinger, 1983) ranging from dugong and whale ribs, shark teeth and turtle scutes to petrified wood and teeth from horses and alligators (Figure 16). Thicknesses of the Bone Valley Member exceed 40 ft (15.2 m) (Plate 54). In terms of hydrologic function, the unit is a localized, yet efficient confining unit within the IAS/ICU. On the other hand, due to the significant economic value of phosphorite deposits, the unit has been extensively mined thereby reducing or eliminating local confinement. Owing to the high phosphorite content, gamma-ray log intensities for Bone Valley Member sediments are very high. For example, the truncated, high-intensity gamma-ray peak at the top of the Peace River Formation for W14385 (ROMP 45; Plate 22) represents Bone Valley Member sediments. Many questions exist regarding the genesis of phosphate in Florida. Given the diverse fossil assemblage, it reflects near-shore marine conditions and is unlik e other large phosphate deposits of the world. Parts of the Bone Valley Member were deposited in a high-energy nearshore environment (topographic highs) while other parts were deposited in a shallow marine environment such as an embayment or lagoon (Scott, 1988). The stratigraphy of the unit is complicated by rapid facies changes and post-depositional erosion, redeposition and weathering (Freas and Riggs, 1968; Webb and Crissenger, 1983). Hawthorn Group (Undifferentiated) Undifferentiated Hawthorn Group sediments lie unconformably above Eocene and Oligocene carbonates and unconformably below undifferentiated Pliocene and younger sands and clays along the upland geomorphic provinces within the northern region, as well as in parts of Pinellas, Hillsborough and Polk Counties. In Marion, Sumter and Lake Counties, sediments mapped as undifferentiated Hawthorn Group may be comprised of one or more of the following lithostratigraphic units (from oldest to youngest): the Penney Farms Formation, the Marks Head Formation and the Coosawhatchie Formation (Scott, 1988). These formations are not delineated owing to their limited extent and stratigraphic pinch-out along the northeastern part of the study area. Moreover, Scott (1988) reported on the difficulty of distinguishing the uppermost Coosawhatchie Formation from undifferentiated Hawthorn Group sediments in central Florida. In the north-central part of the study area, undifferentiated Hawthorn Group sediments occur along the Brooksville Ridge (e.g., W-6903, Plate 5 and W-15933, Plate 9) as well as within karst features and isolated lenses flanking the ridge. Vernon (1951) describes “Miocene Hawthorn formation” sediments along the Brooksville Ridge in Citrus County as greenish-gray montmorillonitic clays. The distribution of these sediments, as well as the

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BULLETIN NO. 68 49 occurrence of hard-rock phosphate in the region lend support to the proposal by Scott (1988) that Hawthorn Group sediments once covered the entire Florida peninsula. Upchurch (1992) also suggests that Hawthorn sedimentation occurred on the crest of the Ocala Platform. Undifferentiated Hawthorn Group sediments are generally comprised of clay beds with variable amounts of carbonate, quartz sand and silt, phosphorite, organic material and minor shell fragments. Maximum elevations of undifferentiated Hawthorn Group sediments exceed 100 ft (30.5 m) MSL along inland uplands and ridges north of Pasco County. In Pinellas County, these sediments generally occur deeper than -25 ft (-7.6 m) MSL. Undifferentiated Hawthorn Group sediments occurring in Hillsborough, Pinellas and Pasco Counties grade laterally southeastward into the Peace River Formation. In central Pinellas County undifferentiated Hawthorn Group sediments exceed 100 ft (30.5 m) thick and grade southward into the Arcadia Formation (Plate 31). Gamma-ray response of the undifferentiated Hawthorn Group sediments varies from lowbackground counts where the unit is dominated by clays, to broad and diffused patterns where phosphorite is more abundant. Gamma-ray logs are generally not very useful as a tool to determine the contact with underlying and overlying units. In the northern region, undifferentiated siliciclastic sediments of the Hawthorn Group comprise discontinuous semi-confinement between the SAS and FAS. The lateral extent and effectiveness of this lower-permeability layer is difficult to define due to factors such as: 1) variable lithology (e.g., percent clay) and thickness, 2) desiccation cracking of thin clayrich beds during long-term low-water table conditions and 3) breaches due to fractures and sinkholes. As a result, many areas in this region are denoted on Plate 55 as “discontinuous basal confinement of SAS.” These same areas are likewise labeled “discontinuous” on Plates 56 and 57. Pliocene and younger Series Post-Hawthorn Group Sediments Sediments overlying Hawthorn Group and older units in the study area are generally comprised of varying percentages of undifferentiated sand, shell and clay. Within the eastern half of the study area, the Cypresshead Formation dominates most uplands (Figure 2) and is well exposed along the Lake Wales Ridge. In the southern region, three PliocenePleistocene formations are recognized: the Tamiami Formation, the Caloosahatchee Formation and the Fort Thompson Formation. The latter two formations are faunally rather than lithologically based. As a result, Scott (1992c) provides a conceptual framework to include Caloosahatchee and Fort Thompson sediments as part of the Okeechobee formation (informal). The framework also includes informal “Bermont formation” sediments. Although mapping post-Hawthorn Group sediments is beyond the scope of this study, general descriptions of the units are provided herein. These undifferentiated surficial sediments and formations generally comprise the SAS. In the southern region, the lower Tamiami Formation is considered part of the IAS/ICU. In the cross sections (Plates 4-37), undifferentiated sediments are broadly classified as sand and clay (UDSC) or sand and shell (UDSS). Existing lithologic descriptions may identify “Pliocene – Pleistocene” sediments (often referred to as “PCPC”); however in the present study, these sediments are labeled “UDSC” due to difficulty in distinguishing the two undifferentiated types as well as inconsistent usage of PCPC. Gamma-ray activity in postHawthorn Group sediments is highly variable (Plates 4-37; Davis et al., 2001). In some areas, however, a consistent peak at the base of these sediments represents a phosphate lag deposit reworked from Hawthorn Group sediments (Scott, 1988; Green et al., 1995; see also W-16303 [TR 7-4] and W-17057 [TR 7-2], Plate 16).

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FLORIDA GEOLOGICAL SURVEY 50 Tamiami Formation Lithology of the Lowerto mid Pliocene (Missimer, 2002) Tamiami Formation (Mansfield, 1939) is difficult to characterize due to the large number of sediment facies it contains. These facies occur over a large region of southern Florida and represent a complex set of depositional environments (Berndt et al., 1998). The Tamiami Formation consists of a wide range of mixed carbonate/siliciclastics (sandy limestone, sand and clay with varying percentages of phosphate grains) and shell beds that are subdivided as members (e.g., Ochopee Limestone Member) south of the study area (Missimer, 1993). The Tamiami Formation is unconformably overlain by the Caloosahatchee Formation and overlies the Peace River Formation either conformably or unconformably. Where present in the study area, the Tamiami Formation is part of the IAS/ICU and SAS (Berndt et al., 1998). A semi-regionally extensive clay layer within the Tamiami Formation comprises the top of the IAS/ICU, whereas the uppermost higher permeability sediments are hydraulica lly connected with the SAS. Sands and finer-grained facies probably represent deposition in a regressing Tamiami sea in the brackish water of a lagoon or bay (DuBar, 1962). Deposition of the shell beds are most likely the result of storms and processes occurring in shallow coastal waters (Missimer, 2001). Phosphatic quartz sand facies containing giant barnacles and echinoids exposed along Alligator Creek and in pits near Acline (Charlotte County) are thought to represent deposition in a shallow water, nearshore environment (DuBar, 1962). Cypresshead Formation The Upper Pliocene Cypresshead Formation (Huddlestun, 1988) is composed entirely of siliciclastics, predominantly quartz and clay minerals (Scott, 1992b; Berndt et al., 1998). It consists of characteristically mottled reddish brown to reddish orange, unconsolidated to poorly consolidated, fine to very coarse grained, clean to clayey sands (Scott, 2001), some of which are cross bedded. Discoid quartz pebbles and mica are also often present. Clay beds are generally thin and discontinuous. Overall, the clay content varies from trace amounts to more than 50 percent, averaging 10-20 percent (Scott, 1992b). Due to weathering, the clays are often altered to kaolinite. Davis et al. (2001) describe three lithozones within the unit, which are based on color, sedimentary structures and varying proportions of siliciclastics. Original fossil material is not present in the sediment but poorly preserved casts and molds of mollusks and burrow structures are occasionally present (Scott, 2001). The Cypresshead Formation occurs in the central uplands of the Florida peninsula south into Highlands County (Arthur, 1993; Scott et al., 2001). Exposure of the formation generally occurs above 100 ft. (30.4 m) MSL (Scott, 1992b, 2001). In the northern half of the study area, the unit lies unconformably on Eocene carbonates, whereas in the southern half it unconformably overlies Hawthorn Group sediments. The Cypresshead Formation can be readily distinguished from the Hawthorn Group because the younger unit is non-phosphatic, contains prominent horizontal bedding and cross bedding, is largely nonfo ssiliferous and contains burrow and bioturbation structures (Huddlestun, 1988). Along the Lake Wales Ridge, the SAS is comprised of sediments from the Cypresshead Formation and undifferentiated sediments (Scott, 1992b). Huddlestun (1988) suggests that the depositional environment was coastal marine (see also discussion of Figure 7 on p. 15). Caloosahatchee Formation The Caloosahatchee Formation was first recognized by Heilprin (1887) as a Pliocene formation he called the “Floridan Beds.” Dall (1887) also considered the deposits Pliocene and described many of the fossils; he referred to them as the Caloosahatchee Beds or Marls. Scott (1992c) includes sediments informally referred to as the Bermont formation within the

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BULLETIN NO. 68 51 Caloosahatchee Formation and reports a Late Pliocene to Early Plei stocene age. The Caloosahatchee Formation consists of marls composed primarily of quartz sand, silt and shells with varying amounts of carbonate in the matrix. It varies from poorly indurated to well indurated and the fauna is varied and often well preserved. Usually moderately to abundantly fossiliferous, some sands are almost or completely barren of fossils (DuBar, 1958). Freshwater limestones are commonly present. The extent of the Caloosahatchee Formation is shown on previous geologic maps by Cooke (1945) and Vernon and Puri (1964). The contact between the subjacent Tamiami Formation and the Caloosahatchee Formation is generally unconformable. The Tamiami Formation was subjected to significant subaerial erosion and the deposition of the Caloosahatchee Formation gradually filled in old “Tamiami valleys” (DuBar, 1958). The Caloosahatchee Formation comprises part of the SAS. In most hydrogeological investigations, the Caloosahatchee Formation is not differentiated from the Fort Thompson Formation (Scott, 1992a). The depositional environment was subtropical with predominantly carbonate deposition and a coastal influx of quartz sand. Tropical and subtropical mollusks and corals abundant in the unit reflect an environment similar to the present area between Cape Sable and Florida Bay (Missimer, 2001). Fort Thompson Formation Sellards (1919) proposed the name Fort Thompson Beds, which were informally designated a formation by Cooke and Mossom (1929). DuBar (1958) recognized the unit as upper Pleistocene. The Fort Thompson Formation is a sandy limestone deposited under freshwater and marine conditions. The sand is fine to medium grained and is interlayered with shell beds and limestones. The shell beds are slightly indurated to unconsolidated and variably sandy (Scott, 1992b; Berndt et al., 1998). A characteristic Fort Thompson marine fossil is Chione elevata and Helisoma scalare (Figure 17) is typical of freshwater beds in the unit (DuBar, 1958). The Fort Thompson Formation is thin, does not exceed 30 ft (9.1 m) in thickness, and has an unconformable relationship to the variable units above and below. It is most commonly underlain by the Caloosahatchee Formation or the Tamiami Formation (DuBar, 1958). The Fort Thompson Formation is part of the undifferentiated sediments in southern Florida (Scott, 1992b) and comprises part of the SAS. The extent of the Fort Thompson Formation is shown on geologic maps by Cooke (1945) and Vernon and Puri (1964). On the most recently published geologic map of Florida (Scott et al., 2001), the Ft. Thompson and Caloosahatchee Formations are mapped as undifferentiated Tertiary – Quaternary shell-bearing sands (TQsu; Figure 2). Figure 17. Characteristic Ft. Thompson Formation fossils Chione elevata (left) and Helisoma scalare (right; photos courtesy of IP/FMNH); bar = 12 mm.

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FLORIDA GEOLOGICAL SURVEY 52 Hydrostratigraphy Introduction The hydrostratigraphic setting of the study area varies from a locally exposed single aquifer system in the north, to three aquifer systems in the central and southern parts of the study area. In the northern region, the FAS ranges from variably confined to unconfined; clayey sediments of the IAS/ICU or basal SAS are locally present; IAS/ICU confining sediments are present especially within the uplands and ridges. The SAS, where present, is intersected by numerous karst features (Trommer, 1987; see also Plate 3) which may act as direct hydraulic connection between the SAS and the FAS. Increased permeability of the IAS/ICU occurs where the Hawthorn Group sediments thicken southward from centra l Hillsborough and Polk Counties. In the central and southern regions, the IAS/ICU collectively forms a thick confining unit with intervening permeable zones that separate the FAS from the SAS. As noted earlier, the nomenclature applied herein is based on aquifer system nomenclature as modified from Florida Geological Survey Special Publication 28 (see Hydrogeology , p. 17; Appendix 2). Hydrogeological properties Numerous studies provide details on hydrogeologic properties of aquifer systems in the study area. For detailed information on aquifer transmissivity, storativity, leakance coefficients, etc., the reader is referred to USGS publications (e.g., Ryder, 1985; Wolansky and Corral, 1985; Metz, 1995; Yobbi, 1996; Knochenmus, 2006), numerous SWFWMD ROMP technical reports (e.g., Clayton, 1994, 1999; Gates, 2001; LaRoche, 2004); SWFWMD hydrogeological studies (e.g., Barcelo and Basso, 1993; Hancock and Basso, 1993; Basso, 2002, 2003) and especially the Southwest Florida Water Management District (2006b) compilation: “Aquifer Characteristics within the Southwest Florida Water Management District, July 2005.” To provide a general characterization of these hydrogeologic parameters, two datasets are statistically and graphically summarized in the discussion of each aquifer system: 1) data in Southwest Florida Water Management District (2006b) that meet certain quality assurance/quality control (QA/QC) standards6 and 2) results of more than 200 hydraulic conductivity and total porosity analyses measured at the FDEP-FGS on cores from within the study area. Both datasets are presented to represent laboratory and field-scale conditions. The Southwest Florida Water Management District (2006b) compilation represents properties measured during aquifer pumping and performance tests, while the FDEP-FGS dataset represents matrix permeability (vertical) and porosity of core samples. In Florida’s dual-porosity (e.g, intergranular and condui t flow) heterogeneous carbonate terrain, it is widely recognized that permeability calculated from field-scale aquifertest data (e.g., Basso, 2002) may differ by orders of magnitude from that of laboratory measurements. These data summaries are presented herein to characterize expected ranges of these parameters for use in hydrologic models and to provide a frame of reference for those collecting hydrological data in the field or lab. For further details on matrix permeability, as well as discussion of its significance and limitations, the reader is referred to Budd (2001, 2002) and Budd and Vacher (2004). In the descriptive statistics for each aquifer system, standard parameters are summarized, including mean, median, range, quartile values, and number of analyses. Also included are distribution descriptors: skewness, kurtosis and 6 QA/QC screening guidelines: 1) used data with “acceptable” and “good” test-reliability scores as defined and assigned in Southwest Florida Water Management District (2006b); 2) avoided aquifer tests where partial penetration was noted and no corrections applied; 3) avoided tests where aquifer penetration thicknesses were inconsistent with casing and total depth data; 4) avoided use of well pairs in which the observation we ll open interval differed from the open interval in the test well by more than 15 percent; 5) avoided short-duration tests; and 6) evaluated comments with respect to quality of test data.

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BULLETIN NO. 68 53 the Anderson-Darling test for normality. In the Anderson-Darling test, the A2 value is the test statistic for normality; if the probability (Pvalue) is greater than 0.05, the data are normally distributed. Graphical summaries of the hydrogeological data include histograms, box plots and 95 percent confidence interval range charts. The histograms include a log-normal curve fit for all parameters except for the porosity data and SAS vertical hydraulic conductivity. The vertical (y) axis on the histograms reflects the total number of analyses (N), which are listed in each statistical summary. Units for each parameter are listed in the figure header. The horizontal (x) axis of the box plots corresponds to the histogram x-axis. Asterisks in the box plots denote statistical outliers. Surficial aquifer system The surficial aquifer system (SAS) is predominately comprised of Late Pliocene to Holocene sediments and is contiguous with land surface. This hydrostratigraphic unit occurs throughout the study area, with the exception of two hydrogeologic settings: 1) where an unobstructed vertical hydr aulic connection exists between surficial sediments and the FAS (e.g., unconfined FAS) and 2) where the very lowpermeability sediments of the Hawthorn Group (e.g., Peace River Formation) locally occur at or near land surface (e.g., SAS absent and FAS is confined). This latter setting occurs in the central and southern Polk Upland physiographic province (Figure 6). The extents of either of these settings are too localized or disturbed by mining to delineate accurately within the scale and scope of this project. The SAS generally consists of unconsolidated quartz sand with variable amounts of shell, clay, phosphate and organic material. Shell content in the SAS increases significantly toward the southern part of the study area (Vacher et al., 1993; see also “UDSS” comprising the SAS in the southernmost cross sections [e.g., Plates 18, 19]). Excluding the ridges, thickness of the SAS averages ~30 ft (~9 m). Along the Lake Wales Ridge in the southeastern part of the study area, SAS thicknesses range to more than 300 ft (99.4 m) (Plates 26 and 55). In the southern region, the areas with relatively thick SAS generally correspond to localities where the permeable upper Tamiami Formation sediments are included within the SAS. The SAS is delineated in areas where laterally extensive, sufficiently confining clayey sediments of the IAS/ICU occur beneath unconsolidated surficial sediments. In parts of the northern region, the SAS locally may directly overly the FAS. Iron-cemented zones (“hardpan”) and intermittent basal clays may result in a "perched" water table or local SASlike unit. On the other hand, basal confinement breached by sinkholes or fractures precludes characterizing much of the northern region as a laterally extensive and functional SAS due to lack of regional hydraulic continuity. In this hydrogeologic setting, delineation of the SAS becomes subjective. To account for such areas, a hachured pattern is included on Plate 55 to reflect “discontinuous basal confinement of the SAS.” It is noteworthy that this subjective delineation could also be applied to the northern, significantly karstified part of the Brooksville Ridge; however, in recognition of available data and to maintain consistency with the IAS/ICU, the SAS is delineated in this area. Groundwater withdrawals from the SAS are minimal compared to that of the IAS/ICU or FAS. Based on data from Marella (2004), the SAS yielded between 1 percent and 5 percent of total groundwater withdrawals in Charlotte, Citrus, Levy, Marion, and Sumter Counties during 2000. In Lee County, the SAS comprised more than 55 percent of total withdrawals (Marella, 2004). Each of the remaining counties in the study area withdrew less than 1 percent groundwater from the SAS (Marella, 2004). Throughout the study area, the local water table mimics topography (Sepulveda, 2002; Arthur et al., in review). Elevation of the water table varies widely throughout the study area, ranging to more than 175 ft (53.3 m) MSL (Arthur et al., in review). Along much of the Lake Wales Ridge, such as in the Intraridge Valley (Figure 6) the water table is often less than 10 ft (3.0 m) below land surface. The water table in other parts of the Lake Wales Ridge, as well as other upland areas, can exceed 50 ft (15.2 m) below land surface. Movement of SAS

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FLORIDA GEOLOGICAL SURVEY 54 groundwater is dynamic, due to complex interactions between recharge, discharge (including pumping and mining operations), runoff, infiltration, evapotranspiration and seepage to and from underlying aquifers (Lewelling et al., 1998). Evidence from paired monitor wells confirms local semi-permeable hydrologic connection between the SAS and FAS in parts of the Lake Wales Ridge due in part to interaquifer connectivity through sinks or paleosinks (Tihansky et al., 1996). Depending on hydraulic conditions, karst density, and the leakance of basal SAS clays (or IAS/ICU clays), the SAS may locally recharge the FAS in parts of the northern study area. Local pumping, rainfall events, seasonal and climatic variations add to the complex dynamics of this relationship. Surface-water/groundwater interactions are evident throughout the study area, such as coastal springs and base flow in rivers and streams. An outstanding example of these dynamic interactions occurs within the Peace River basin. Along the upper part of the basin, maximum river-flow losses exceed 11 million gallons per day (4.2x107 liters per day), locally recharging underlying aquifers due to a downward head gradient, riverbed sinkholes and inferred buried subsidence structures (Lewelling et al., 1998). Further downstream in the lower part of the basin, the river receives intergranular (rather than karst-related) seepage from the SAS and possibly the IAS/ICU (Lewelling et al., 1998). Understanding such surfacewater/groundwater interactions is essential toward the establishment of effective minimum flows and levels (MFL) and total maximum daily loads (TMDL). Some karst-related features, however, do not affect these interactions. For example, the closed topographic depressions in eastern Sarasota County (Plate 3) are likely “sags” formed due to the dissolution of carbonate shell material (Sam Upchurch, personal communication, 2004). These sags likely do not function as preferential recharge pathways from the SAS to underlying aquifer systems. Correlation of the SAS with lithostratigraphic units in the study area generally places the system within post-Hawthorn Group sediments. In the northern region, these Pliocene and younger sands and clays are undifferentiated (UDSC). Along the eastern region, the sediments correlate with the Cypresshead Formation. Further south, the Ft. Thompson, Caloosahatchee and Tamiami Formations comprise most of the SAS. Basal SAS clays may represent low-permeability undifferentiated Hawthorn Group sediments, or re-worked Hawthorn Group sediments in the northern and central region. In the central and eastern regions, the base of the SAS generally coincides with the top of the Peace River Formation (Hawthorn Group); however, relatively clean sands of the Peace River Formation comprise part of the SAS in localized areas (e.g., W14382 [ROMP 23], Plate 17). In the southern region, the base of the SAS not only overlies the Peace River Formation, but also the fine-grained dolostones of the Arcadia Formation (parts of western/coastal Manatee and Sarasota Counties) and middle-Tamiami clays (e.g., southeastern Charlotte and Lee Counties; Reese, 2000; Weinberg and Cowart, 2001). Note however, that Missimer and Martin (2001) report two aquifers within the SAS in Lee County, the lowermost being the “Lower Tamiami Aquifer;” whereas researchers such as Knochenmus and Bowman (1998) and Torres et al. (2001) place the entire Tamiami Formation within the IAS/ICU. The relation between the Tamiami Formation and hydrostratigraphic units from Lee County north to Sarasota County warrants further investigation. Vadose-zone hydrogeologic characteristics of the SAS can be approximately inferred from a comparison of environmental geology and soil permeability maps (Figures 4 and 18, respectively). Patterns in both of these maps roughly correlate with major geomorphic provinces (Figure 6). The most permeable soils and shallow sand-dominated sediments or carbonate lithologies are located in the Coastal Swamps, Gulf Coastal Lowlands, the Lake Wales Ridge, whereas some of the least permeable soils occur along the southern extent of the Brooksville Ridge and parts of the Western Valley. In the northern region, surficial deposits may be missing, having been eroded away and exposing limestone at the surface (e.g.,

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BULLETIN NO. 68 55 unconfined FAS; see Plates 29 and 30). In contrast, these same deposits may locally exceed 100 ft (30.5 m) thick where they infill karst features (including paleo-sinks represented by W-15075 and W-10829; Plates 5, 6 and 29). Depending on the permeability of infilling sediments, the karst features may provide hydraulic connection between the SAS and the FAS. Topographic inversion (i.e., differential carbonate dissolution due to chemical buffering and confinement) also contributes to the highly variable thickness of the SAS in the northern region. Along the axis of the Brooksville Ridge, for example, more than 50 ft (15.2 m) of SAS is locally observed. Much of the Ridge, however, is perforated by sinkholes (Plate 3), making delineation of the SAS problematic. Although lithologic data from wells support presence of the SAS along the Brooksville Ridge, extent of the unit is even more subjective in the surrounding region. Assessment of regional mapping (geology [Figure 2], environmental geology [Figure 4], and soil permeability [Figure 18]) warrants the dashed (i.e., approximate) extent of the SAS in the region (Plate 55). These hachured areas are considered semiconfined to unconfined FAS. In addition to lithologic evidence, hydraulic data support local delineation of the SAS in parts of the northern region. Well W-15647 (ROMP 90; Plate 10) provides a classic example of confinement between the SAS and the FAS in this region. Water levels measured during drilling rose 3 ft (0.9 m) when the clays underlying the SAS were fully penetrated and artesian conditions of the FAS became evident. The IAS/ICU in this well is too thin to depict graphically in Plate 10. Moreover, given the proximity of the well to the IAS/ICU extent, whether the clays are basal SAS or IAS/ICU is subjective. Confined and semi-confined areas of Citrus County have been identified (Lee, 1998). Water levels in paired monitor wells also provide valuable information regarding the presence of the SAS (i.e., basal confinement) in the absence of an extensive IAS/ICU. This data, however, should be interpreted with caution: similar water levels may reflect “leaky” confinement and seasonal or local pumping conditions should be considered. The “Floridan” water levels in W-14336 (ROMP 93, Plate 10), are at least 5 ft (1.5 m) lower than SAS water levels (U.S. Geological Survey, 1990) indicating a well-defined hydraulic separation between the two aquifer systems. Hydrologic data from W16644 (ROMP LP-6), located approximately 2 mi (3.2 km) north of cross section D-D’ (Plate 7) indicates that FAS water levels are typically more than one foot (0.3 m) above the surficial water table. At W-16644, 12 ft (3.7 m) of clay and clayey sand provide sufficient confinement between the FAS and SAS. As noted above, effectiveness of the hydraulic separation between the SAS and the subjacent FAS varies locally. Water levels in the paired wells L11KD and L11KS (northeast of W-5054, Plate 2), are nearly indistinguishable, thus indicating leaky to unconfined conditions between the FAS and "water table" levels in surficial sediments (U.S. Geological Survey, 1998). In contrast, water levels from the monitor-well pair L11MM and L11MS (southeast of W-5054, Plate 2) confirm existence of SAS conditions because “watertable” elevations differ from the FAS potentiometric surface (U.S. Geological Survey, 1998). Paired monitor wells with inconsistent trends in water levels suggest that there may be some degree of confinement of the FAS, either as low permeability horizons in the base of the SAS or in the uppermost carbonates of the FAS (e.g., mudstones/micrites or densely recrystallized zones). A SWFWMD Technical Memorandum (Basso, 2004) provides detail on the hydrogeologic setting of the Hernando-Pasco County (or “Northern Tampa Bay”) region. In the memorandum, the location of wetlands, soil properties, lithologic data and hydrographs from nested wells and lakes are used to delineate three zones: unconfined UFA, locally perched water table (generally restricted to the southern

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FLORIDA GEOLOGICAL SURVEY 56 Figure 18. Soil permeability of study area (Arthur et al., in review); (data compiled on per county basis from U.S. Department of Agriculture, Natural Resource Conservation Service, 2002 and the Florida Geographic Data Library [www.fgdl.org]). Explanation Study Area Water Management DistrictsSoil Permeability 20.0 in/hr 10.0 in/hr 0.1 in/hrGulf of Mexico Soil Permeability 010203040 5 Miles 010203040 5 KilometersProjection: Custom FDEP Albers Scale 1:1,750,000

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BULLETIN NO. 68 57 Brooksville Ridge) and semi-confined UFA. This localized study provides a refinement of confining conditions within the northern Tampa Bay region. Although differences in nomenclature and scale of study exist, the areas delineated by Basso (2004) are broadly consistent with regional representations of the SAS in Plate 55. Basso suggests, however, that the locally perched water table aquifer (SAS in this report) along the southern part of the Brooksville Ridge terminates northward near the Hernando-Citrus County boundary. This conclusion is consistent with an increase in soil permeability and a relative abundance of closed topographic depressions within the Brooksville Ridge in Citrus County (Figure 18 and Plate 3). Moreover, the potentiometric surface for paired SWFWMD monitor wells in southern Citrus County (“Lecanto 1” [deep] and “Lecanto 2” [shallow]), which have been measured since 1965, track almost perfectly indicating unconfined FAS. On the other hand, lithologic data from wells in the Brooksville Ridge, Citrus County, documents more than 30 ft (9.1 m) of local confinement. These observations serve as additional examples of the complex and variable degrees of confinement in the northern region and underscore the subjective nature of the SAS extents shown in Plate 55. The SAS occurs throughout most of the central and southern regions, except where IAS/ICU sediments crop out (e.g., central Polk County). Several paired monitor wells document the SAS, for example, discrete monitor wells constructed in both the SAS and the FAS at W-12943 (Plates 12 and 31) reveal head differences between the two aquifer systems (Coffin and Fletcher, 1992). Other complementary pairs of monitor wells in the northern Pinellas and Hillsborough Counties support the presence of a "water table" that is distinguishable from FAS potentiometric levels, suggesting that some degree of laterally extensive confinement exists between the two aquifer systems. In the southern region, the SAS is isolated from the FAS by thick intervening permeable and less permeable siliciclastics and carbonates of the IAS/ICU. High-density karst areas (Plate 3) such as the Lake Wales Ridge increase the potential for inter-aquifer communication between the SAS and subjacent aquifers. Hydraulic properties for the SAS vary widely, owing to its heterogeneous composition and thickness. Selected hydrogeologic data from SWFWMD (2006b; see also p. 52) and Florida Geological Survey laboratory data are summarized in Figures 19-22. Surficial aquifer system parameters include transmissivity, specific yield and horizontal and vertical hydraulic conductivity, respectively. Note that the horizontal hydraulic conductivity (Kh) is calculated from the unsaturated aquifer thickness and the transmissivity. In the vertical hydraulic conductivity (Kv) data, if outliers are excluded, the range in Kv is similar to that reported by Vacher et al. (1993). A difference of several orders of magnitude exists between Kv and Kh values. One factor influencing this difference pertains to sampling bias, where many Kv samples were selected to characterize the degree of basal confinement of the SAS. Arguably, some of these sediments may represent the semiconfining facies of the IAS/ICU. Intermediate aquifer system/ intermediate confining unit The IAS/ICU occurs throughout much of Florida (Scott, 1992a) and is comprised of all rocks “that lie between and collectively retard the exchange of water” between the SAS and the FAS (Southeastern Geological Society, 1986). In general, this aquifer system correlates with Oligocene-Pliocene clays, sands and carbonates of the Hawthorn Group, and Pliocene clays, sands, limestone and shell beds of the Tamiami Formation (e.g., Berndt et al., 1998; Arthur et al., 2001a; Torres et al., 2001; Ward et al., 2003). In the study area, the IAS/ICU is broadly characterized by three hydrogeologic settings: 1) relatively thin, laterally discontinuou s low-permeability confining to semi-confining sediments that provide local hydraulic separation between the SAS and the FAS (hachured area in Plates 56 and 57), 2) low-permeability confining to semiconfining sediments hydr aulically separating the SAS from the FAS (non-hachured areas in the northern region, Plate 56 and 57), and 3) interlayered sequences of permeable and lesspermeable rocks and sediments separating the SAS from the FAS (central and southern regions; Figure 23 and Plates 56-57).

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FLORIDA GEOLOGICAL SURVEY 58 7500 6000 4500 3000 1500 0 Median Mean 3000 2500 2000 1500 1000 500 Anderson-Darling Normality Test Variance4493649.8 Skewness1.80288 Kurtosis2.50311 N1 5 Minimum 20.0 A-Squared 1st Quartile374.0 Median 1260.0 3rd Quartile2206.0 Maximum6930.0 95% Confidence Interval for Mean 656.5 1.50 3004.3 95% Confidence Interval for Median 459.2 2041.3 95% Confidence Interval for StDev 1552.0 3343.2 P-Value <0.005 Mean 1830.4 StDev 2119.895% Confidence IntervalsSummary for SAS T (ft^2/day) Figure 19. Statistical summary of SAS transm issivity data from Southwest Florida Water Management District (2006b). The horizontal (x) axis of the box plots corresponds to the histogram x-axis. Asterisks in the box plot denote statistical outliers. 0.25 0.20 0.15 0.10 0.05 0.00 Median Mean 0.200 0.175 0.150 0.125 0.100 0.075 0.050 Anderson-Darling Normality Test Variance0.00831 Skewness-0.59933 Kurtosis-1.35168 N10 Minimum0.00510 A-Squared 1st Quartile0.05625 Median0.20000 3rd Quartile0.20500 Maximum0.25660 95% Confidence Interval for Mean 0.08097 0.74 0.21137 95% Confidence Interval for Median 0.051170.20685 95% Confidence Interval for StDev 0.062690.16639 P-Value0.036 Mean0.14617 StDev0.0911495% Confidence IntervalsSummary for SY Figure 20. Statistical summary of SAS specific yield data from Southwest Florida Water Management District (2006b).

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BULLETIN NO. 68 59 60 48 36 24 12 Median Mean 45 40 35 30 25 20 15 Anderson-Darling Normality Test Variance321.854 Skewness0.17215 Kurtosis-1.27803 N15 Minimum6.930 A-Squared 1st Quartile12.000 Median32.700 3rd Quartile50.300 Maximum59.000 95% Confidence Interval for Mean 21.080 0.36 40.950 95% Confidence Interval for Median 14.98845.706 95% Confidence Interval for StDev 13.13528.294 P-Value0.407 Mean31.015 StDev 17.94095% Confidence IntervalsSummary for SAS Kh** (ft/day) Figure 21. Statistical summary of SAS horizontal hydraulic conductivity data from Southwest Florida Water Management District (2006b). ** calculated from transmissivity and saturated aquifer thickness. 1.9 1.6 1.3 1.0 0.7 0.4 0.1 Median Mean 0.25 0.20 0.15 0.10 0.05 0.00 -0.05 Anderson-Darling Normality Test Variance0.13582 Skewness4.7300 Kurtosis23.0704 N2 6 Minimum0.00002 A-Squared 1st Quartile0.00004 Median0.00010 3rd Quartile0.02215 Maximum1.85700 95% Confidence Interval for Mean -0.05137 7.75 0.24634 95% Confidence Interval for Median 0.000040.00090 95% Confidence Interval for StDev 0.289030.50873 P-Value <0.005 Mean0.09749 StDev0.3685395% Confidence IntervalsSummary for SAS Kv (ft/day) Figure 22. Statistical summary of SAS vertical hydraulic conductivity data based on falling-head permeameter analyses of core samples completed at the FDEP-FGS. Due to sampling bias, most samples represent clay-bearing sediments. Asterisks in the box plot denote statistical outliers.

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FLORIDA GEOLOGICAL SURVEY 60 POLK COLLIER DADE LEE OSCEOLA HENDRY GLADES HIGHLANDS PASCO MONROE PALM BEACH MANATEE HARDEE DESOTO HILLSBOROUGH OKEECHOBEE BREVARD BROWARD SARASOTA CHARLOTTE MARTIN ST. LUCIE INDIAN RIVER PINELLAS 20020 10 Miles 20020 10 KilometersFDEP IAS public supply wells +20km buffer Approximate extent of permeable IAS/ICU (present study) Extent of IAS from Miller (1986)Explanation Figure 23. Approximate extent of IAS/ICU permeable zones. The region mapped as IAS/ICU (Plates 56 and 57) north of this line is dominated by lower permeability hydrogeologic facies.

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BULLETIN NO. 68 61 Up to three relatively more permeable wateryielding zones exist in the latter regions (Corral and Wolansky, 1984; Trommer, 1993; Torres et al., 2001; Knochenmus, 2006), which provide groundwater to municipalities, industries and agriculture. During 2000, the IAS/ICU was the source of approximately 10 percent to 15 percent of total groundwater withdrawals in DeSoto, Hardee, and Highlands Counties (Marella 2004). In Sarasota and Charlotte Counties, the usage was 32 percent and 75 percent respectively (Marella, 2004). Lithology and hydrology of IAS/ICU permeable zones is heterogeneous and complex. Where multiple water-pr oducing zones exist, they are generally laterally discontinuous and difficult to map, even with the aid of hydrochemical assessm ent (Knochenmus and Bowman, 1998; Knochenmus, 2006). Moreover, the hydraulic character of the IAS/ICU is unpredictable due to varying degrees of vertical and lateral permeability within the unit. In the northern region, IAS/ICU sediments generally occur along upland features such as the Brooksville Ridge, Fairfield Hills and Sumter and Lake Uplands (Figure 6, Plate 56). This hydrostratigraphic unit also occurs throughout the central and southern regions. Maximum IAS/ICU elevations exceed 125 ft (38.1 m) MSL along the Brooksville and Lakeland Ridges. Thickness of the IAS/ICU ranges to more than 900 ft (274 m) in the southernmost part of the study area (Plate 57). Various extents of IAS/ICU water-producing zones have been proposed within the study area (Figure 23). In the Florida Aquifer Vulnerability Assessment (FAVA), (Arthur et al., in review) the extent includes Miller’s (1986) delineation plus a region defined by the distribution of FDEP-regulated public water supply wells that utilize the IAS/ICU (Figure 23). Included among the FDEP supply-well region is a 12.4 mile (20 km) buffer, which was added to account for lateral uncertainty (Arthur et al., in review). In the present study, however, lithologic data represented in cross sections were assessed to re-define an approximate northern limit of IAS/ICU permeable zones (Figure 23). This redefined extent is comparable to that proposed by Basso (2003). The region north of the zone is dominated by variably lowpermeability IAS/ICU sediments, except for localized relatively permeable sediments within the Brooksville Ridge (e.g., W-15933; Plate 9). Within the northeastern part of the study area, the IAS/ICU is comprised of the Coosawhatchie Formation (Hawthorn Group) and possibly other Hawthorn Group units (i.e., the Marks Head and Penney Farms Formations) (W-8883, Plate 5; W-12794, Plate 8). In the central part of the northern region, the IAS/ICU occurs along the axis of the Brooksville Ridge and is comprised of undifferentiated Hawthorn Group sediments (e.g., W-6903, Plate 5; W15933, Plate 9). Scott (1988) suggests that these sediments at one time likely blanketed the entire northern region. In the lowlands flanking the Brooksville Ridge, laterally discontinuous Hawthorn Group remnants (possibly reworked) or Pliocene-Pleistocene clayey sediments (e.g., W-707, Plate 9) function hydrologically as semiconfining sediments that promote local FAS artesian and perched water-table conditions. As indicated by the h achured areas in Plates 56 and 57, at least half of the northern region is discontinuous with respect to semi-confining sediments of the IAS/ICU. This qualitative delineation is based on inspection of borehole lithologic data, assessment of the state geologic map (Scott et al., 2001) and topographic analysis (i.e., comparing Hawthorn Group distribution and depth to carbonate rocks with the 15 m (49.2 ft) resolution DEM. In some of these areas, the IAS/ICU is absent and local aquifer conditions range from SAS overlying FAS (with varying degrees of hydraulic separation) to unconfined FAS. Thickness of the IAS/ICU along the Brooksville Ridge and the northeastern part of the study area averages ~35 ft (~11 m) and locally exceeds 100 ft (30.5 m) (W-15933, Plate 9). Highly variable and localized IAS/ICU thicknesses in these areas are due in part to infilling of paleosinks. Plates 5 and 6 reflect this scenario, however, due to the localized occurrence, the IAS/ICU was not delineated. In the central region, hydrogeologic properties of the IAS/ICU are highly variable due to lithologic heterogeneity and complex interbedding typical of the Hawthorn Group

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FLORIDA GEOLOGICAL SURVEY 62 sediments. The IAS/ICU primarily correlates with the Hawthorn Group in this region; however, some post-Hawthorn siliciclastics may also be included in the uppermost IAS/ICU (e.g. reworked Hawthorn Group sediments in southern Pasco and no rthern Hillsborough Counties). Throughout most of Pinellas and Hillsborough Counties, vertical hydraulic continuity generally exists between the Tampa Member (Arcadia Formation) and the Suwannee Limestone, thereby placing the base of the IAS/ICU at the top of the Tampa Member (Broska and Barnette, 1999). In northern Pinellas County, however, roughly a third of the wells penetrating the Suwannee Limestone encounter clay beds at the base of the Tampa Member. Given the discontinuous nature of these clays, the base of the IAS/ICU is considered to correlate with the top of the Tampa Member although local-scale head differences may occur between this unit and the Suwannee Limestone. In southern Hillsborough County, however, lithologic data from six adjacent wells indicate that basal Tampa Member clays are more laterally extensive, suggesting contiguous hydraulic separation from the Suwannee Limestone. In this area (Figure 8), the Tampa Member is considered part of the IAS/ICU (Green et al., 1995; Figure 8; Plates 14, 21 and 20). As additional hydrologic and lithologic data become available, the base of the IAS/ICU should be reassessed in these areas. Mixed siliciclastic-car bonate deposits of the IAS/ICU thicken southward from ~75 ft (22.8 m) in central Polk County to more than 900 ft (274 m) in Charlotte County (Plate 57) creating several water-bearing zones (Trommer, 1993). In most of west central Florida the IAS/ICU is less permeable than the underlying FAS and restricts movement of water between the SAS and FAS (Ryder, 1985). Where multiple permeable zones exist in the IAS/ICU in the central and southern regions, flow regimes are not fully understood. Extents of these permeable zones need to be better defined along with groundwater flow patterns in order to improve management of the IAS/ICU as a water supply source (Torres et al., 2001). The hydrologic parameters for these zones have been well characterized by Basso (2002) for southern Hillsborough, Manatee and northern Sarasota Counties. Additional de tails regarding depths, thicknesses, extents and hydraulic properties of these permeable zones are presented in Duerr and Enos (1991), Barr (1996), Knochenmus and Bowman, (1998), Torres et al. (2001), Basso (2003) and Knochenmus (2006). Distinct differences exist among potentiometric levels representing IAS/ICU permeable zones (Duerr, 2001). Regional IAS/ICU potentiometric maps, however, are generally constructed from wells open to multiple permeable zones. As a result, the potentiometric surface of the IAS/ICU represents a composite of permeable zones, which likely contributes to its high variability across the study area. In May 2001, the composite head level in the IAS/ICU ranged from more than 120 ft (36.6 m) MSL in the “Four Corners” area (northwestern Hardee County) to approximately 50 ft (15.2 m) MSL in Highlands County (Duerr, 2001). Within the study area, IAS/ICU potentiometric elevation lows occur in southern Hillsborough County and northern Sarasota County (Duerr, 2001). Selected hydrogeologic data compiled in SWFWMD (2006; see also discussion on p.52) are statistically summarized in Figures 24-27 (transmissivity, storativity, leakance and Kh, respectively). Laboratory data from the FDEPFGS, including falling-head Kv analyses (Figure 28) and total porosity (Figure 29) are also presented. Basso (2002) presents similar hydrologic data subdivided based on IAS/ICU permeable zones. A five order-of-magnitude difference exists between Kv and Kh mean values reported herein. Similar to the SAS data, sampling bias may account for some of this variation; Kh values predominately reflect data from IAS/ICU permeable zones while samples from which Kv was measured may have been somewhat biased toward less permeable zones or more indurated core samples. Moreover, as with all Kv data in heterogeneous strata, th e measured values are affected by lower-permeability horizons within the analyzed core segments.

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BULLETIN NO. 68 63 12000 10000 8000 6000 4000 2000 0 Median Mean 4000 3000 2000 1000 Anderson-Darling Normality Test Variance13534930.9 Skewness1.59693 Kurtosis1.82144 N30 Minimum3.0 A-Squared 1st Quartile265.5 Median1186.6 3rd Quartile4975.1 Maximum12967.9 95% Confidence Interval for Mean 1542.4 2.66 4290.0 95% Confidence Interval for Median 655.4 2874.0 95% Confidence Interval for StDev 2930.0 4945.7 P-Value < 0.005 Mean 2916.2 StDev 3679.095% Confidence IntervalsSummary for IAS T (ft^2/day) Figure 24. Statistical summary of IAS/ICU tran smissivity data from Southwest Florida Water Management District (2006b). 0.0024 0.0020 0.0016 0.0012 0.0008 0.0004 0.0000 Median Mean 0.0007 0.0006 0.0005 0.0004 0.0003 0.0002 0.0001 Anderson-Darling Normality Test Variance0.000000 Skewness2.75235 Kurtosis7.29439 N25 Minimum0.000030 A-Squared 1st Quartile0.000073 Median0.000180 3rd Quartile0.000351 Maximum0.002530 95% Confidence Interval for Mean 0.000141 4.03 0.000653 95% Confidence Interval for Median 0.0001000.000276 95% Confidence Interval for StDev 0.0004850.000863 P-Value <0.005 Mean0.000397 StDev0.00062195% Confidence IntervalsSummary for IAS S Figure 25. Statistical summary of IAS/ICU storativity data from Southwest Florida Water Management District (2006b). Asterisks in the box plot denote statistical outliers.

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FLORIDA GEOLOGICAL SURVEY 64 0.03 0.02 0.01 0.00 Median Mean 0.008 0.006 0.004 0.002 0.000 Anderson-Darling Normality Test Variance0.000067 Skewness3.7045 Kurtosis14.2198 N1 6 Minimum0.000033 A-Squared 1st Quartile0.000187 Median0.000968 3rd Quartile0.001921 Maximum0.033425 95% Confidence Interval for Mean -0.000939 3.70 0.007792 95% Confidence Interval for Median 0.0001960.001759 95% Confidence Interval for StDev 0.0060520.012680 P-Value <0.005 Mean0.003427 StDev0.00819395% Confidence IntervalsSummary for IAS L (per day)Figure 26. Statistical summary of IAS/ICU leakance data from Southwest Florida Water Management District (2006b). Asterisks in the box plot denote statistical outliers. 240 180 120 60 0 Median Mean 60 50 40 30 20 10 Anderson-Darling Normality Test Variance2900.656 Skewness2.12027 Kurtosis4.85107 N30 Minimum0.045 A-Squared 1st Quartile4.988 Median13.200 3rd Quartile59.125 Maximum232.000 95% Confidence Interval for Mean 18.370 3.07 58.592 95% Confidence Interval for Median 8.68434.030 95% Confidence Interval for StDev 42.89372.402 P-Value <0.005 Mean38.481 StDev53.85895% Confidence IntervalsSummary for IAS Kh** (ft/day)Figure 27. Statistical summary of IAS/ICU horizo ntal hydraulic conductivity data from Southwest Florida Water Management District (2006b). Asterisk in the box plot denotes statistical outliers. ** calculated from transmissivity and permeable zone thickness.

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BULLETIN NO. 68 65 0.0335 0.0260 0.0185 0.0110 0.0035 Median Mean 0.006 0.005 0.004 0.003 0.002 0.001 0.000 Anderson-Darling Normality Test Variance0.000045 Skewness2.69316 Kurtosis7.41148 N38 Minimum0.000000 A-Squared 1st Quartile0.000048 Median0.000337 3rd Quartile0.003100 Maximum0.030300 95% Confidence Interval for Mean 0.001124 6.72 0.005513 95% Confidence Interval for Median 0.0001020.001230 95% Confidence Interval for StDev 0.0054430.008638 P-Value <0.005 Mean0.003318 StDev0.00667795% Confidence IntervalsSummary for IAS Kv (ft/day)Figure 28. Statistical summary of IAS/ICU vertic al hydraulic conductivity data based on fallinghead permeameter analyses of core samples completed at the FDEP-FGS. Asterisks in the box plot denote statistical outliers . 52.5 45.0 37.5 30.0 22.5 15.0 Median Mean 40 38 36 34 32 30 Anderson-Darling Normality Test Variance91.010 Skewness-0.547647 Kurtosis0.466245 N1 9 Minimum14.130 A-Squared 1st Quartile28.900 Median 35.370 3rd Quartile39.400 Maximum49.550 95% Confidence Interval for Mean 29.528 0.34 38.724 95% Confidence Interval for Median 29.626 38.225 95% Confidence Interval for StDev 7.208 14.108 P-Value 0.447 Mean 34.126 StDev 9.54095% Confidence IntervalsSummary for IAS Total Porosity (%)Figure 29. Statistical summary of IAS/ICU total porosity data based on core sample volumetric analyses completed at the FDEP-FGS.

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FLORIDA GEOLOGICAL SURVEY 66 Floridan aquifer system The FAS occurs throughout Florida and is often an artesian aquifer. Artesian conditions may vary with seasonal rainfall and pumping conditions. In the study area, springs flow yearround along parts of coastal Citrus, Pasco and Hernando Counties (Figure 6; Healy, 1974; Scott et al., 2004). Other common areas of FAS discharge include wetlands in the Tsala Apopka Plain, southern Pasco County, and the Green Swamp (northwest Polk County). The FAS discharges into the SAS along the northern part of the Lake Wales Ridge and also provides baseflow to surface-water bodies (e.g., Hillsborough River). Along the trace of the Peace River, the FAS discharges into permeable zones of the IAS/ICU (Sepulveda, 2002). Similar conditions exist within southern Sarasota County, southwestern DeSoto County and most of Charlotte County. Throughout the remainder of the study area, the FAS is recharged from overlying aquifer systems. The top of the FAS does not always coincide with a specific lithostratigraphic unit. Instead, it is defined by permeability and hydraulic connection (Johnston and Bush, 1988). Moreover, per the Southeastern Geological Society (1986) definition, the top of the FAS “generally coincides with the absence of significant thicknesses of (silici)clastics from the section and with the top of the vertically persistent permeable carbonate section.” In the study area, the surface of this hydrostratigraphic unit may include the following formations in ascending order: Avon Park Formation, Ocala Limestone, Suwannee Limestone, and units within the Hawthorn Group (Trommer, 1993; Ryder, 1985; Berndt et al., 1998; Corral and Wolansky, 1984). Figure 8 summarizes the extent of lithostratigraphic units that comprise the FAS surface. The top of the FAS correlates regionally with the Oligocene Suwannee Limestone where present; however, in westcentral Florida, the Tampa Member (Arcadia Formation) of the Hawthorn Group coincides with the top of the FAS where it is hydraulically connected to the underlying Suwannee Limestone (generally Pinellas [e.g., Hickey, 1982; Broska and Barn ette, 1999], southern Pasco, Hillsborough an d Manatee Counties [Green et al., 1995]). In the absence of the Tampa Member or Suwannee Limestone, Eocene rocks (Avon Park Formation or Ocala Limestone) comprise the top of the FAS (Figure 8; Miller, 1986). Based on lithostratigraphic correlation and the FAS definition applied herein (see also Appendix 2), the top of the unit ranges in age from Middle Eocene to Early Miocene. In the northern region, the FAS (Plates 4 through 8) includes the Avon Park Formation, Ocala Limestone and Suwannee Limestone. In Pasco County (Plate 11), hydrogeologic data suggest that the Tampa Member is also hydraulically connected to the FAS. For example, water levels measured at well W16609 (TR 18-2A; Plates 11 and 29) increased only ~1.2 inches (~ 3 cm) in elevation while coring through the Tampa Member into the Suwannee Limestone (DeWitt, 1990). Overall, the FAS is unconfined to semi-confined in the region. Along parts of the northern coastal zone, laterally extensive confining units are thin to absent (Plate 56) and hydraulic head differences allow local recharge to the FAS, which in turn enhances development of secondary porosity along fractures and bedding planes in the FAS. These dissolution-widened channels have a much higher hydraulic conductivity. For example, dissolution channels in the Ocala Limestone are highly developed in Hernando, Citrus and Marion Counties (Trommer, 1993). Abundant sinkholes in the region, indicated by the region’s pattern of closed topographic depressions (Plate 3), locally breach confining beds. As indicated by the hydrologic data presented in the Surficial aquifer system section, p. 53, local unconfined to semi-confined FAS conditions exist in the northern region. For example, water levels in a FAS monitor well and a “surficial” monitor well at site W-16311 (ROMP LP-4, Plate 7) exhibit nearly identical elevations, suggesting that confinement is leaky or absent between surficial sediments and the carbonates of the FAS. Along the Brooksville Ridge and parts of the northeastern margin of

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BULLETIN NO. 68 67 the study area, IAS/ICU Hawthorn Group sediments provide increased confinement of the FAS. Numerous sinkholes (Plate 3) and paleosinks breach confining clayey sediments that would otherwise justify delineation of confined FAS (Plates 6, 7 and 8; Trommer, 1987). As a result, characterization of certain areas along the Brooksville Ridge as IAS/ICU and SAS is very subjective. In the central, southern and eastern regions, the zero MSL (sea-level) contour of the FAS surface (central Hillsborough and Polk Counties; Plate 58) represents a hinge-line, south of which the dip of the FAS markedly increases. As noted in Figure 8, the FAS surface generally correlates with lithostratigraphic units. The surfaces of these units have been affected by depositional, erosional or structural features (e.g., dissolution, basins, channel scouring, fracture-controlled drainage systems, possible faults, etc.). Other variations in the FAS surface (Plate 58) are due to sub-regional confinement between lithostratigraphic units. For example, several wells in central Hillsborough County indicate that confinement exists between the Suwannee Limestone and the Tampa Member (Arcadia Formation), resulting in correlation of the FAS surface with the Suwannee Limestone. Uncertainty in the area w ith regard to vertical hydraulic connectivity between these two lithostratigraphic units and lateral/regional groundwater flow warrant further study. In the southern region, the FAS surface generally coincides with the top of the Oligocene Suwannee Limestone. Along western DeSoto County, however, the FAS surface correlates poorly with any specific lithostratigraphic unit (Figure 8). In some boreholes, such as W-18117 (ROMP 35, northwest DeSoto County, Plate 2), the FAS surface occurs approximately 90 ft (27.4 m) below the top of the Suwannee Limestone (LaRoche, 2004). Along the eastern margin of the study area, the Ocala Limestone comprises the surface of the FAS, except for a small area in northeastern Osceola County, where the Ocala Limestone is absent and the Avon Park Formation is the uppermost unit (Figure 8; Gates, 2006). Plate 34 is a representative cross section of the FAS surface, where it occurs nearly 100 ft (30.4 m) MSL in well W-15650 (ROMP 88; northern Polk County) and deepens significantly toward the south where it occurs at -861 ft (-262 m) MSL in well W-15289. The FAS potentiometric surface within the study area (Figure 30) is highly variable and contains several prominent features. Maximum elevations (exceeding +130 ft [39.6 m] MSL) occur in north-central Polk County, near Polk City and within the Green Swamp. This maximum is located in the center of a ridge-like potentiometric high that extends north-northwest into Marion and Sumter Counties, and southsoutheast along the axis of the Lake Wales Ridge. Another topographically associated high occurs along the Brooksville Ridge in Pasco and Hernando Counties. At least two distinct potentiometric highs with more than 20 ft (6.1 m) of relief also occur: 1) the Dunellon Gap (Levy County), and 2) the Big Cypress Swamp (central Pasco County). Minimum elevations occur within a few feet below sea level in southwestern Hillsborough County. Troughs in the UFA potentiometric surface align with the Withlacoochee River in Hernando and Pasco Counties, the Hillsborough and Alafia Rivers (Hillsborough County), indicating significant baseflow contributions to these rivers (Figure 30). A less distinct trough is associated with lakes in eastern Citrus County (i.e., TsalaApopka Lake and Lake Panasofkee). Flow directions vary considerably in response to these highs/ridges and lows/troughs; however, in a very broad sense the groundwater flow in the UFA for the region west of the Lake Wales Ridge is generally toward the Gulf coast. Seasonal perturbations in the potentiometric surface are generally due to variable recharge rates and pumping. Regionally, the most notable difference between the May 2005 (Ortiz and Blanchard, 2006) and September 2005 potentiometric surface (Ortiz, 2006) is a broadening of the ridge-like high along the Lake Wales Ridge in response to the rainy season. Relative to a predicted “pre-development” potentiometric surface, Bush and Johnston (1988) report drawdown exceeding 20 ft (6.1 m) in a region encompassing roughly one-third of the District centered on northwest Hardee County.

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FLORIDA GEOLOGICAL SURVEY 68 3 0 2 0 5 0 6 0 9 0 10 0 1 1 0 8 0 1 2 0 1 0 0 1 3 0 4 0 8 0 5 0 5 0 6 0 1 0 50 A Explanation Major Rivers Potentiometric Line (Feet) Water Management Districts Study Area Gulf of Mexico B C Floridan aquifer system Potentiometric Surface September, 2005Projection: Custom FDEP Albers Scale 1:1,750,000 010203040 5 Miles 010203040 5 KilometersContour Interval: 10 ft Figure 30. Potentiometric surface of the Florid an aquifer system, September, 2005 (from Ortiz, 2006); A – Withlacoochee River, B – Hillsborough River and C – Alafia River. See Figure 1 for additional river labels.

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BULLETIN NO. 68 69 A meaningful comparison of the IAS/ICU potentiometric surface (Duerr, 2001) with that of the FAS is qualitative at best (see discussion starting on page 62). A more accurate, although site-specific method for assessing the recharge/discharge relation between the IAS/ICU and FAS is to compare water levels in nested wells, many of which are located at District ROMP sites. As noted above, Miller (1986) subdivided the FAS into the Upper Floridan aquifer (UFA) and the Lower Floridan aquifer (LFA). The UFA is the principal source of groundwater throughout the study area except for Charlotte County, where only 20 percent of total withdrawals originate from the UFA (based on data from 2000 as compiled by Marella, 2004) due to naturally poor water quality. The most productive units of the UFA are located within the Avon Park Formation, Ocala Limestone and the Suwannee Limestone (Ryder, 1985). A highly permeable facies of the FAS, referred to as the “Boulder Zone” (Kohout, 1965), is characterized by cavernous, fractured dolostones with very high transmissivities (Puri et al., 1973). Vernon (1970) reported “Boulder Zone” facies throughout the Florida peninsula. More recently, however, this hydrogeologic facies has been recognized as discontinuous and found to be limited to the southern third of the Florida peninsula (Miller, 1986). The facies does not occur within the same lithostratigraphic unit throughout its extent (Miller, 1986). Maliva et al. (2001) report occurrences of “Boulder Zone” facies in the Early Eocene Oldsmar Formation in Charlotte, Lee and Collier County injection wells. This facies has been reported to occur at depths shallower than -1300 ft (-396.2 m) MSL in Charlotte County (Maliva et al., 2001), which corresponds to Avon Park Formation carbonates. In the southernmost peninsula, the facies occu rs within the Paleocene Cedar Keys Formation as well as the Eocene Avon Park Formation and Ocala Limestone (Puri and Winston, 1974). Wolansky et al. (1980) mapped “the highly permeable dolomite zone” of the Avon Park Formation throughout the southern two-thirds of the District. These well-indurated dolostones are commonly fractured and contain large dissolution channels. The zone occurs ~100 ft (~ 30.5 m) below the top of the Avon Park Formation in the central part of the study area and ~ 400 ft (~ 122 m) below the Avon Park Formation surface in the southern region. The SAS and IAS/ICU generally provide confinement of the UFA (Berndt et al., 1998) except for areas in the northern region where the UFA may be unconfined and where karst and paleokarst promote interaquifer connectivity. Hydrogeologic conditions vary considerably between the northern and southern regions depending on the degree of confinement. The interpolated surface of the UFA ranges from greater than 75 ft (22.9 m) MSL along the Brooksville Ridge to less than -825 ft (-251 m) MSL in southern Charlotte County (Plate 58). Locally, maximum elevations exceed 130 ft (39.6 m) along the Brooksville Ridge (W-14917 [ROMP 109], Plate 7). A map of overburden thickness provides a different perspective on the depth to the top of the UFA (Figure 31). This map, developed by subtracting the UFA surface from a 15 m (49.2 ft) resolution DEM (Arthur et al., in review), allows comparison of the aquifer system to geomorphic features. For example, note the thin overburden along the Brooksville Ridge compared to the Lake Wales Ridge, as well as the maximum overburden thickness of ~900 ft (~274 m) in Charlotte County. The base of the UFA occurs within the lower Avon Park Formation, where vertically and laterally persistent evaporite minerals (gypsum and anhydrite) are present in the carbonate rocks (e.g., Ryder, 1985; Hickey, 1990; see Middle Floridan confining unit [MFCU], p. 75, for more information). Thickness of the UFA, calculated as a “grid difference map,” ranges from less than 300 ft (91.4 m) to more than 1500 ft (457 m; Figure 32). Regional subjacent confinement of the UFA is comprised of the MFCU where present. Examples of basal UFA confinement are represented in several cross sections (e.g., Plates 7, 9, 21 and 31). Note, however, that Miller’s (1986) delineation of overlapping MFCU units by default suggests that the base of the UFA in these areas is a complex discontinuous surface. This aspect of the UFA is described in more detail in the next section.

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FLORIDA GEOLOGICAL SURVEY 70 Explanation Study Area Water Management DistrictsFAS Overburden Thickness 900 ft 450 ft 0 ft Gulf of Mexico Floridan aquifer system Overburden ThicknessProjection: Custom FDEP Albers Scale 1:1,750,000 010203040 5 Kilometers 010203040 5 Miles Figure 31. Floridan aquifer system overburden thickness as predicted from geospatial modeling (i.e., DEM minus top of FAS). The map is not co ntoured due to extreme resolution differences in source grids.

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BULLETIN NO. 68 71 1 0 5 0 1 2 0 0 4 5 0 1 5 0 0 7 5 0 3 0 0 6 0 0 9 0 0 1 3 5 0 1 0 5 0 1 3 5 0 6 0 0 6 0 0 9 0 0 4 5 0 1 3 5 0 1 5 0 0 1 3 5 0 6 0 0 7 5 0 9 0 0 6 0 0 6 0 0 12 00 1 5 0 0 1 3 5 0 1 3 5 0 Projection: Custom FDEP AlbersUpper Floridan aquifer Thickness 010203040 5 Miles Scale 1:1,750,000 010203040 5 Kilometers Contour Interval: 150 ftExplanation Study Area Contours Water Management DistrictsUFA Thickness 1600 ft 665 ft 265 ft Gulf of Mexico Figure 32. Thickness of the Upper Floridan aquifer (includes non-potable).

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FLORIDA GEOLOGICAL SURVEY 72 The LFA lies beneath MFCU strata and consists of the lower part of the Avon Park Formation, the Oldsmar Formation and the upper part of the Cedar Keys Formation (Miller, 1997). The Cedar Keys Formation forms the lower boundary of the LFA and generally consists of persistently dolomitized carbonates with widespread bedded and intergranular gypsum and anhydrite. Except for the northeastern part of the study area, the LFA is commonly highly saline and not used as a potable or an economically treatable water source. Research on use of the LFA as a sustainable fresh water resource for the northeastern part of the District is underway (Southwest Florida Water Management District, 2006a). The LFA is the lowermost known and welldefined aquifer, ranging in elevation from -400 ft (-122 m) MSL in the northeastern part of the study area to more than -2500 ft (-762.0 m) MSL in Sarasota and Charlotte counties; LFA thicknesses exceed 2,400 ft (731.5 m) in the southeast part of the study area (Miller, 1986). Per findings of the CFHUD II (Copeland et al., in review) the low-transmissivity strata lying at the base of the FAS (e.g., the “sub-Floridan confining unit” referenced in Southeastern Geological Society, 1986) is informally referred to as “undifferentiated aquifer systems.” Hydraulic properties of the FAS are summarized in Figures 33-38 for the parameters transmissivity, storativ ity, leakance, Kh, and total porosity, respectively. A large degree of vertical anisotropy exists in the FAS (e.g., Ryder et al., 1980; Ryder, 1982) due to variations in grain size and diagenetic factors affecting permeability (e.g., Budd, 2002; Budd and Vacher, 2004). Median horizontal and vertical hydraulic conductivity values differ by three orders of magnitude, which is notably less than the difference between these same parameters in the SAS and IAS/ICU. This is due in part to a relative lack of sampling bias in the analyzed FAS core samples. A greater degree of anisotropy in the SAS and IAS/ICU relative to the FAS is another possible contributing factor. Anomalously high transmissivity values (Figure 33) likely reflect the influence of dual-porosity (i.e. fracture/conduit flow). It is also noteworthy that spatial analysis of dolines (e.g., sinkholes) in the northern and central region indicates a statistically significant correlation between FAS hydraulic conductivity and doline-area ratios (Armstrong et al., 2003). 1200000 1000000 800000 600000 400000 200000 0 Median Mean 140000 120000 100000 80000 60000 40000 20000 Anderson-Darling Normality Test Variance35044192303 Skewness4.4198 Kurtosis21.3092 N90 Minimum1300 A-Squared 1st Quartile18650 Median38369 3rd Quartile69789 Maximum1203210 95% Confidence Interval for Mean 49393 18.49 127810 95% Confidence Interval for Median 2927948540 95% Confidence Interval for StDev 163279219401 P-Value <0.005 Mean88602 StDev18720195% Confidence IntervalsSummary for UFA T (ft^2/day)Figure 33. Statistical summary of UFA transmissivity data from Southwest Florida Water Management District (2006b). Asterisks in the box plot denote statistical outliers.

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BULLETIN NO. 68 73 0.096 0.080 0.064 0.048 0.032 0.016 0.000 Median Mean 0.005 0.004 0.003 0.002 0.001 0.000 Anderson-Darling Normality Test Variance0.000117 Skewness6.6858 Kurtosis47.7119 N81 Minimum0.000000 A-Squared 1st Quartile0.000265 Median0.000640 3rd Quartile0.001200 Maximum0.086000 95% Confidence Interval for Mean 0.000269 24.66 0.005050 95% Confidence Interval for Median 0.0004040.000935 95% Confidence Interval for StDev 0.0093650.012792 P-Value <0.005 Mean0.002660 StDev0.01081295% Confidence IntervalsSummary for UFA S Figure 34. Statistical summary of UFA storativity data from Southwest Florida Water Management District (2006b). Asterisks in the box plot denote statistical outliers. 0.072 0.060 0.048 0.036 0.024 0.012 0.000 Median Mean 0.006 0.005 0.004 0.003 0.002 0.001 0.000 Anderson-Darling Normality Test Variance0.000114 Skewness5.6131 Kurtosis33.5295 N59 Minimum0.000029 A-Squared 1st Quartile0.000147 Median0.000300 3rd Quartile0.001800 Maximum0.072380 95% Confidence Interval for Mean 0.000361 15.47 0.005921 95% Confidence Interval for Median 0.0002410.000567 95% Confidence Interval for StDev 0.0090310.013036 P-Value <0.005 Mean0.003141 StDev0.01066895% Confidence IntervalsSummary for UFA L (per day) Figure 35. Statistical summary of UFA leakance data from Southwest Florida Water Management District (2006b). Asterisks in the box plot denote statistical outliers.

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FLORIDA GEOLOGICAL SURVEY 74 6000 5000 4000 3000 2000 1000 0 Median Mean 500 400 300 200 100 Anderson-Darling Normality Test Variance620386.37 Skewness5.8896 Kurtosis38.2409 N8 6 Minimum 7.65 A-Squared 1st Quartile50.50 Median 91.90 3rd Quartile178.75 Maximum6050.00 95% Confidence Interval for Mean 107.74 21.43 445.49 95% Confidence Interval for Median 78.51 110.07 95% Confidence Interval for StDev 684.97 926.82 P-Value <0.005 Mean 276.61 StDev 787.6595% Confidence IntervalsSummary for UFA Kh** (ft/day) Figure 36. Statistical summary of UFA horizont al hydraulic conductivity data from Southwest Florida Water Management District (2006b). ** calculated from transmissivity and permeable zone thickness. Asterisks in the box plot denote statistical outliers. 1.5 1.2 0.9 0.6 0.3 0.0 Median Mean 0.150 0.125 0.100 0.075 0.050 0.025 0.000 Anderson-Darling Normality Test Variance0.05202 Skewness4.2139 Kurtosis21.8401 N1 3 7 Minimum0.00000 A-Squared 1st Quartile0.00565 Median0.01967 3rd Quartile0.08725 Maximum1.72957 95% Confidence Interval for Mean 0.06175 26.02 0.13882 95% Confidence Interval for Median 0.014220.02795 95% Confidence Interval for StDev 0.203890.25882 P-Value <0.005 Mean0.10028 StDev0.2280895% Confidence IntervalsSummary for UFA Kv* (ft/day) Figure 37. Statistical summary of UFA vertical hydraulic conductivity data based on results of falling-head permeameter analyses of core samples completed at the FDEP-FGS. Asterisks in the box plot denote statistical outliers.

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BULLETIN NO. 68 75 50 40 30 20 10 0 Median Mean 40 39 38 37 36 35 Anderson-Darling Normality Test Variance73.978 Skewness-1.22649 Kurtosis2.93402 N1 1 7 Minimum2.300 A-Squared 1st Quartile31.950 Median 38.730 3rd Quartile42.625 Maximum53.490 95% Confidence Interval for Mean 35.481 1.91 38.631 95% Confidence Interval for Median 37.100 39.950 95% Confidence Interval for StDev 7.622 9.870 P-Value <0.005 Mean 37.056 StDev 8.60195% Confidence IntervalsSummary for UFA Total Porosity (%) Figure 38. Statistical summary of UFA total po rosity data based on results of core sample volumetric analyses completed at the FDEP-FGS. Asterisks in the box plot denote statistical outliers. Middle Floridan confining unit Miller (1986) recognizes three confining units within the study area (Units I, II and VI) that separate the UFA from the LFA; however, in context of the overall FAS he states: “ the units act as a single confining unit within the main body of permeable limestone that constitutes the aquifer system.” In the present study, we adopt a more descriptive hydrostratigraphic name for the Miller’s (1986) “middle confining unit” of the FAS: the Middle Floridan confining unit (MFCU). This name simply associates the confining units with the aquifer system in which they reside. This nomenclature has also been adopted by the CFHUD II (Copeland, et al., in review). Complexity of the MFCU within and beyond the study area is readily apparent given the seven units mapped by Miller (1986) separating the UFA from the LFA in Florida. On a more local scale, delineation of the base of the UFA becomes challenging where overlapping confining units of the MFCU occur. Within the study area, unit I occurs along the eastern margin and is identified as a leaky confining unit that is “not much different from that of the permeable zones vertically adjacent to it” (Miller, 1986). Units II and VI are identified as carbonates (primarily dolostone) with intergranular gypsum and comprise a hydrogeologically significant confining facies that separates the UFA from the LFA in the study area. The MFCU mapped herein includes Miller’s (1986) units II and VI and is principally identified based on lithology and mineralogy: borehole samples that contain thin gypsum/anhydrite beds or intergranular gypsum/anhydrite five percent (by volume). While some may consider five percent too conservative (e.g., too high), a notable relative increase in matrix confining properties is the emphasis herein, recognizing that transition zones may occur, as well as zones where variable precipitation and dissolution of these minerals may have occurred. Geophysical logs and water-quality data are also used to identify or infer evidence of the MFCU. In addition to data generated for this report, data from Miller

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FLORIDA GEOLOGICAL SURVEY 76 (1988), Hickey (1982), Sacks (1996), Stewart (1966), O’Reilly et al. (2002) and unpublished SWFWMD ROMP reports are also used to interpolate the MFCU surface. Miller’s (1986) unit II, which reaches depths of -1,900 ft (-579.1 m) MSL in Sarasota County correlates with most of the MFCU surface (Plate 59). Unit VI (Miller, 1986) reaches depths of 2,100 ft (-640.1 m) MSL in southeastern DeSoto County and along the southern half of Charlotte County. According to data from Miller (1988), the two units overlap in western Highlands/eastern DeSoto Counties as well as western Charlotte and Lee Counties. Several wells investigated by M iller (1986, 1988) and in the present study indicate that the MFCU may not be laterally continuous throughout the study area; however for purposes of regional mapping, the MFCU is contoured continuously and the areas in question are annotated (Plate 59). The initial protocol for mapping the MFCU was to reflect the uppermost occurrence of the unit in a borehole using the lithologic criteria outlined above. This method, however, yielded anomalous surface patterns and vertical discontinuities where Miller’s (1986) units II and VI coexist in a well. A MFCU surface map based on this initial protocol yielded two domelike features in the southern region in the vicinity of these wells. The domes represented unit II overlying unit VI, separated by high permeability zones (Miller, 1988) and thus did not reflect a contiguous mappable surface. The distribution of well control for unit II (Plate 59) also brings into question the degree to which unit II is laterally continuous. Many sufficiently deep wells within the extent of unit II do not encounter the unit. It is also noteworthy that Miller (1986) describes units II and VI as having nearly indistinguishable lithologic characteristics. Figure 39. Interpretations of the MFCU in the st udy area. Upper cross section reflects MFCU units mapped by Miller (1986); lower cross section reflects alternate interpretation showing continuity between Miller’s units II and VI, with isolated MFCU middle to upper Avon Park confinement overlying the deeper, more laterally continuous unit. See Plate 59 for cross-section location. A A’

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BULLETIN NO. 68 77 Evaluation of the regional slope of the MFCU, lithologic similarities between the units, and sparse data for unit II lead to an alternate interpretation: unit II north of Manatee and Hardee Counties may correlate with unit VI south of these counties (Figure 39). In this interpretation, isolated MFCU facies occur approximately 400 ft (122 m) above the lower MFCU unit in southwestern Highlands and western Charlotte Counties. Plate 59 and Figure 39 (bottom half) reflect this latter interpretation. Wells that encountered both MFCU facies (II and VI) are represented by green symbols (Plate 59) and are labeled with the elevation of the shallower discontinuous MFCU facies, which is informally referred to as the “middle to upper Avon Park confining unit.” Data in Miller (1988) indicate a high permeability zone between the base of the “middle to upper Avon Park confining unit” and the MFCU as mapped herein within all wells containing both of Miller’s MFCU facies (II and VI). Based on comparison of Plate 38 with Miller’s (1986) Middle Eocene isopach, the MFCU as defined and mapped in this study generally occurs within the lower half of the Avon Park Formation. Exceptions to the generalization include Marion, Osceola and Pinellas Counties, where the MFCU occurs within the upper third of the Avon Park Formation. Several cros s sections contain wells that penetrate the MFCU (e.g., Plates 7, 9, 21, 29, 30 and 34). In the northwestern part of the study area, the elevation of the MFCU is generally deeper than -400 ft (-122 m) MSL. The unit dips southward to depths below ft (-640.1 m) MSL in Charlotte County. South of the study area, Reese (2000) mapped the “dolomite-evaporite unit in the middle confining unit” of the FAS, recognizing the significance of dense unfractured dolostones in his study area. He also notes that this unit may locally be considered the top of the MFCU, which is generally supported by the MFCU surface in Plate 59. It is possible that the few wells with shallower elevations in Reese’s (2000) “dolomite – evaporite uni t” map are related to the discontinuous “middle to upper Avon Park confining unit” described herein. Presence of the MFCU is debatable for two regions within the eastern half of the study area. Throughout most of Marion County (including parts of Alachua, Sumter and Lake Counties), the MFCU is inferred. Borehole cuttings from multiple wells in the area show no evidence of gypsum/anhydrite; however, anomalously high sulfate concentrations (some exceeding 500 mg/L; Sacks, 1996) in FAS groundwater samples suggest the MFCU may be present. As such, this area is denoted on Plate 59 as “MFCU inferred based on water quality data.” In eastern Polk County, Miller (1986) mapped the MFCU; however, available well control (this study and Miller, 1988), as well as water quality data for the area, yields no direct evidence that it is present. Sprinkle (1989) and Katz (1992) report relatively low sulfate concentrations (< 50 mg/L) within the UFA in the area. To emphasize this uncertainty the MFCU in this area is labeled “MFCU possibly absent: limited data” (Plate 59). Hydraulic conductivity analyses of MFCU rocks were not completed for this study; however, data exists in SWFWMD and consultant’s reports. For example, Hickey (1982) reports hydraulic conductivities ranging from 1.1 ft/day to 6.0x10-7 ft/day (3.8x10-4 to 2.1x10-10 cm/sec) based on core representing the “lower confining bed” (greater than -1000 ft [-305 m] MSL) in Pinellas County. To provide characterization of MFCU hydraulic conductivity and total porosity, data has been compiled from three injection well sites: Knight’s Trail, Sarasota County, (Law Environmental, Inc., 1989), Burnt Store Utilities, Charlotte County, (ViroGroup, Inc., 1995) and Punta Gorda, Charlotte County, (City of Punta Gorda, Water Resource Solutions, Inc., and Boyle Engineering Corporation, 2001). Data from Stewart (1966) and Hickey (1982) and Montgomery Watson Americas (1997) are also included. Hydraulic conductivity (Kv) for the 21 MFCU cores anal yzed in these studies range from 1.5x10-1 ft/day to 1.0x10-6 ft/day (5.3x10-5 to 3.53x10-10 cm/sec), with a median value of 1.84x10-3 ft/day (6.5x10-7 cm/sec; Figure 40). Total porosity for these samples average 17.2 percent (median = 19.6 percent) and range from 5 percent to 30 percent (Figure 41). Basso (2002) reports Kh values ranging from .002 to .04 ft/day (7.06x10-07 to 1.4x10-5 cm/sec). Transmissivity data range from 0.08 to 2.9 ft2/day (0.86 to 31.2 m2/day).

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FLORIDA GEOLOGICAL SURVEY 78 0.15 0.12 0.09 0.06 0.03 0.00 Median Mean 0.025 0.020 0.015 0.010 0.005 0.000 -0.005 Anderson-Darling Normality Test Variance0.001051 Skewness4.2710 Kurtosis18.8184 N21 Minimum0.000001 A-Squared 1st Quartile0.000326 Median0.001840 3rd Quartile0.007085 Maximum0.149000 95% Confidence Interval for Mean -0.003961 5.50 0.025553 95% Confidence Interval for Median 0.0004260.004443 95% Confidence Interval for StDev 0.0248030.046816 P-Value <0.005 Mean0.010796 StDev0.03241995% Confidence IntervalsSummary for MFCU Kv (ft/day) Figure 40. Statistical summary of MFCU vertical hydraulic conductivity data based on results of falling-head permeameter analyses of core samples; compiled from Stewart (1966), Hickey (1982), Law Environmental (1989), ViroGroup (1995), Montgomery Watson Americas, Inc., (1997), City of Punta Gorda, et al., (2001). Asterisks in the box plot denote statistical outliers. 32 28 24 20 16 12 8 4 Median Mean 22 20 18 16 14 Anderson-Darling Normality Test Variance46.980 Skewness-0.499332 Kurtosis-0.197892 N1 9 Minimum5.000 A-Squared 1st Quartile13.700 Median 19.600 3rd Quartile21.000 Maximum30.000 95% Confidence Interval for Mean 13.844 0.77 20.451 95% Confidence Interval for Median 15.169 21.000 95% Confidence Interval for StDev 5.179 10.136 P-Value 0.038 Mean 17.147 StDev 6.85495% Confidence IntervalsSummary for MFCU Total Porosity (%) Figure 41. Statistical summary of MFCU total poro sity data based on volumetric analyses of core samples; compiled from Stewart (1966), Law Environmental (1989), ViroGroup (1995), Montgomery Watson Americas, Inc. (1997), City of Punta Gorda, et al., (2001).

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BULLETIN NO. 68 79 SUMMARY The hydrogeologic framework of the Southwest Florida Water Management District region described in this report is spatially characterized through a series of 32 maps (plates and figures) and 34 cross sections. Lithologic, hydrologic and geophysical data from more than 1050 wells comprise a database of subsurface elevations and thicknesses for nine lithostratigraphic and four hydrostratigraphic units represented in these maps and cross sections. Elevations of unit boundaries for most of the wells used in the maps and cross sections have been confirmed through visual inspection of cores and cuttings by the authors and those acknowledged in this report . Additional data on which the maps and cross sections are based are incorporated from peer-reviewed reports and interpreted from geophysical logs and existing lithologic descriptions. The lithostratigraphic units are discussed in terms of age, lithology, mineralogy, common fossils, sedimentary structures, porosity/permeability, contact relations with other units, facies changes, spatial distribution (vertical and lateral), gamma-ray log responses, hydrostratigraphic unit correlations and depositional environments. Hydrostratigraphic units are similarly discussed in terms of spatial distribution, regional and local hydraulic characteristics, hydrogeologic properties and correlation with lithostratigraphic units. Among the challenges that exist when creating subsurface stratigraphic maps based on well data is the need to balance three factors: 1) accuracy of the interpolated contours relative to the data on which each map is based, 2) the implicit resolution of the map, which is depicted by the contour interval and the degree of perturbations in the contours and 3) an accurate regional characterization of the unit being mapped. For example, a map that is 100 percent accurate with respect to elevations or thicknesses may overemphasize local anomalies such as karst features. Although a small percentage of wells represent these anomalous elevations, the wells also represent an infinitesimal fraction of the total number of anomalous features in the mapped surface. In other words, thousands of paleosink features may exist in the top of a carbonate unit; however, less than five percent of the wells in the database may have encountered one of these features. Hence, a regional-scale map would be more representative of the true regional character of the surface (o r thickness) if the local anomalies had less influence on the interpolated surface. Moreover, a highly accurate map may also result in jagged, irregular contours, which may imply changes in elevation (or thickness) at a scale that is not justified by the distribution and density of the well data. To achieve an appropriate balance of the aforementioned factors, an iterative process of data evaluation, sample inspection, data interpretation, and spatial and statistical analysis was completed. For the final maps, kriging was used to interpolate map surfaces, which were then corrected as needed for consistency with land surface and other mapped units. The interpolated surfaces were then smoothed to reflect the regional character of each mapped unit. The surface interpolations also provide GIS coverages that can be applied in groundwater flow models and 3D applications. The cross sections focus on data from cores, with an emphasis on those collected through the SWFWMD Regional Observation and Monitorwell Program (ROMP). Data from geophysical logs as well as cores and cuttings archived in the Florida Geological Survey sample repository were used to fill gaps in the cross-section well coverage. Of the 34 cros s sections, nine trend approximately north-south, averaging approximately 60 mi (~96 kilometers) in length, while the remaining sections generally trend east-west and average approximately 35 mi (~56 km) in length. Graphical representation of borehole data from 149 wells used in the cross sections include lithostratigraphic and hydrostratigraphic boundaries and cross-well correlations, lithology, mineralogy and gammaray log response. Each section also includes topographic profiles labeled with selected anthropogenic features. The relationship between lithostratigraphic and hydrostratigraphic units is straightforward in many parts of the study area; however, the

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FLORIDA GEOLOGICAL SURVEY 80 association can be locally complex and indistinct. In either case, the relationship depends on the degree of hydraulic continuity between and among lithostratigraphic units. The variable hydrogeologic setting in the northern region serves as an example: characterization of the SAS (water-table aquifer) is complicated by lateral hydraulic discontinuities. Regionally, the water table may reflect the potentiometric surface of the unconfined FAS (e.g., west of the Brooksville Ridge); however, local hydraulic separation between the SAS and the FAS may exist. As a result, delineation of a regionally extensive SAS that is significant as a waterproducing unit is the subject of some debate. The framework of stratigraphy and hydrogeology developed during this investigation serves as a foundation for numerous applications, ranging from more refined hydrogeological mapping to mineral resource assessments, well-field designs and groundwater models. Regardless of the application, it is our hope that this study facilitates science-based decision making regarding the protection, conservation and management of the solid-earth and water resources of southwestern Florida.

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BULLETIN NO. 68 81 REFERENCES Aadland, R.K., Rolf, K., Gellici, J.A., and Thayer, P.A., 1995, Hydrogeologic framework of west-central South Carolina: South Carolina Department of Natural Resources Wate r Resources Report 5, 200 p., http://www.dnr.sc.gov/water/hydro/HydroPubs/Abs_dnr_R05.htm (July, 2008). Allison, D., Groszos, M., and Rupert, F., 1995, Top of rock of the Floridan aquifer system in the Suwannee River Water Management District: Flor ida Geological Survey Open-File Map Series 84, scale 1:475,000, 1 sheet. Applin, E.R., 1951, Preliminary report on buried pre-Mesozoic rocks in Florida and adjacent states: U.S. Geological Survey Circular no. 91, 28 p. Applin, P.L., and Applin, E.R., 1944, Regional subs urface stratigraphy and structure of Florida and southern Georgia: American Association of Pe troleum Geologists Bulletin, v. 28, p. 1673-1753. Applin, P.L., and Applin, E.R., 1965, The Comanche Series and associated rocks in central and south Florida: U.S. Geological Survey Professional Paper 447, 84 p. Armstrong, B., Chan, D., Collazos, A., and Mallams, J. L., 2003, Karst studies in west central Florida: USF seminars in karst environments: Doline and aquifer characteristics within Hernando, Pasco and northern Hillsborough Counties, in Proceedings of the 2003 Seminar in Karst Environments Course at the USF Department of Geology: Tamp a, University of South Florida, p. 39-52. Arthur, J.D., 1988, Petrogenesis of early Mesozoic tholeiite in the Florida basement and an overview of Florida basement geology: Florida Geological Su rvey Report of Investigations 97, 39 p. ______, 1993, Geologic map of Highlands County: Fl orida Geological Survey Open-File Map Series 52; scale approximately 1:126,720, 1 sheet. Arthur, J.D., and Rupert, F.R., 1989, Selected geomorphic features of Florida in Scott, T.M., Arthur, J.D., Rupert, F.R., and Upchurch, S., eds., The lithostra tigraphy and hydrostratigraphy of the Floridan aquifer system in Florida: Field trips for the 28th International Geological Congress, p. 10-14. Arthur, J.D., Tihansky, A., and DeWitt, R., 1995, Stratigraphic variability in confining materials overlying the Floridan aquifer system in a re gional and local (sub-lake) geologic framework: Lake Wales Ridge, Central Florida: SEPM Congress on Sedimentary Geology Abstracts, v. 1, p. 26. Arthur, J.D., and Pollock, W.H., 1998, Use of ArcVie w GIS and related extensi ons for geologic surface modeling preliminary results from sub-surface mapping in southwest Florida, in Soller, D., ed., Proceedings of the second annual workshop on digital mapping techniques: Methods for geologic map data capture, management and publication: U.S. Geological Survey Open-File Report 98487, p. 73-78. Arthur, J.D., Lee, R.A., and Li, L., 2001a, Lithos tratigraphic and hydrostratigraphic cross sections through Levy-Marion to Pasco Counties, southwest Florida: Florida Geological Survey Open-File Report 81, 21 p.

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FLORIDA GEOLOGICAL SURVEY 82 Arthur, J.D., Cowart, J.A., and Dabous, A.A., 2001b, Florida aquifer storage and recovery geochemical study: year three progress report: Florida Ge ological Survey Open-File Report 83, 46 p. Arthur, J.D., Wood, H., Baker, A.E., Cichon, J.R ., Raines, G.L., 2007, Development and implementation of a Bayesian-based aquifer vulnerability assessment in Florida: Natural Resources Research, vol. 16, p. 93107. Arthur, J.D., Baker, J., Cichon, J., Wood, A., and Rudin, A., Flor ida Aquifer Vulnerability Assessment (FAVA): Contamination potential of Florida’s principal aquifer systems: Florida Geological Survey Bulletin 67, (in review). Back, W., and Hanshaw, B.B., 1970, Comparison of ch emical hydrogeology of the carbonate peninsulas of Florida and Yucatan: Journal of Hydrology, v. 10, p. 330-368. Barcelo, M., and Basso, R., 1993, Computer model of groundwater flow in the eastern Tampa Bay Water Use Caution Area: Brooksville, Southwest Florida Water Management District, 102 p. Barnett, R.S., 1975, Basement structure of Florida and its tectonic implications: Transactions of the Gulf Coast Association of Geological Societies, v. 25, p.122-142. Barr, G.L., 1996, Hydrogeology of the surficial and in termediate aquifer systems in Sarasota and adjacent counties, Florida: U.S. Geological Survey Wa ter-Resources Investigations Report 96-4063, 22 p. Bass, M.N., 1969, Petrography and ages of crystalline b asement rocks of Florida: American Association of Petroleum Geologists Memoir no. 11, p. 283-310. Basso, R., 2002, Hydrostratigraphic zones within the Eastern Tampa Bay Water Use Caution Area: Brooksville, Southwest Florida Water Management District, 34 p. plus appendices. ______, 2003, Predicted change in hydrologic conditions along the Upper Peace River due to reductions in groundwater withdrawals: Brooksville, Southw est Florida Water Management District, 53 p. ______, 2004, Hydrogeologic setting of lakes with in the Northern Tampa bay region: Brooksville, Southwest Florida Water Management District Technical Memorandum (November 9), 27 p. Berndt, M.P., Oaksford, G.M., and Schmidt, W., 1998, Chapter 3-Groundwater: in Fernald, E.A. and Purdum, E.D., eds., Water Resources Atlas of Florida: Tallahassee, Florida State University, Institute of Science and Public Affairs, 312 p. Braunstein, J., Huddlestun, P., and Biel, R. (eds.), 1988, Gulf Coast Region: Correlation of stratigraphic units in North America (COSUNA) project: Tulsa, American Association of Petroleum Geologists, 1 sheet. Brewster-Wingard, G.L., Scott, T.M., Edwards, L.E., Weedman, S.D., and Simmons, K.R., 1997, Reinterpretation of the peninsular Florida Oli gocene: an integrated stratigraphic approach: Sedimentary Geology, v. 108, p. 207-228. Broska, J.C., and Barnette, H.L., 199 9, Hydrogeology and analysis of aquifer characteristics in westcentral Pinellas County, Florida: U.S. Geological Survey Open-File Report 99-185, 23 p.

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BULLETIN NO. 68 83 Broska, J.C., and Knochenmus, L.A., 1996, Assessment of the hydrogeology and water quality in a nearshore well field Sarasota, Florida: U.S. Geologi cal Survey Water-Resources Investigations Report 96-4036, 64 p. Budd, D.A., 2001, Permeability loss with depth in the Cenozoic carbonate platform of west-central Florida, USA: American Association of Petroleum Geologists Bulletin, v. 85, p. 1253-1272. ______, 2002, The relative roles of compaction and ear ly cementation in the destruction of permeability in carbonate grainstones: A case study from the Pale ogene of west-central Florida, USA: Journal of Sedimentary Research, v. 72, p. 116-128. Budd, D.A., and Vacher, H.L., 2004, Matrix permeab ility of the Upper Floridan aquifer: Hydrogeology Journal, v. 12, p. 531-549. Budd, D.A., Hammes, U., and Vacher, H.L., 1993, Calc ite cementation in the Upper Floridan aquifer: A modern example for confined-aquifer cementation models?: Geology, v. 21, p. 33-36. Buono, A., and Rutledge, A.T., 1978, Configuration of the top of the Floridan Aquifer, Southwest Water Management District and adjacent areas: U.S. Geological Survey Water-Resources Investigations, 78-34, 1 sheet. Bush, P.W., and Johnston, R.H., 1988, Groundwater hydraulics, regional flow and groundwater development of the Floridan aquifer system in Florida and in parts of Georgia, South Carolina, and Alabama: U.S. Geological Survey Professional Paper 1403-C, 80 p. Campbell, K.M., 1989, Geology of Sumter County, Florida: Florida Geological Survey Report of Investigation 98, 28 p. Campbell, K.M., Scott, T.M., Green, R. and Evans, W.L., III, 1993, Sarasota County intermediate aquifer system core drilling and analysis: Florida Geological Survey Open-File Report 56, 21 p. Campbell, K.M., Scott, T.M. and Green, R.C., 1995, Core drilling and analysis: City of Sarasota, downtown well field: Florida Geological Survey Open-File Report 62, 16 p. Cander, H.S., 1994, An example of mixing-zone dolomite, middle Eocene Avon Park Formation, Floridan aquifer system: Journal of Se dimentary Research, v. 64, p. 615-629. ______, 1995, Interplay of water-rock interaction efficiency, unconformities and fluid flow in a carbonate aquifer: Floridan aquifer system: American Association of Petroleum Geologist Memoir, v. 63, p. 103-124. Carr, W.J., and Alverson, D.C., 1959, Stratigraphy of middle Tertiary rocks in part of west-central Florida: U.S. Geological Survey Bulletin 1092, 111 p. Champion, K.M., and Starks, R., 2001, The hydrology and water quality of select springs in the Southwest Florida Water Management Dist rict: Brooksville, Southwest Florida Water Management District, Water Quality Monitoring Program, 149 p. Chen, C.S., 1965, The regional lithostratigraphic analysis of Paleocene and Eocene rocks of Florida: Florida Geological Survey Bulletin 45, 105 p.

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FLORIDA GEOLOGICAL SURVEY 84 Chowns, T.M., and Williams, C.T., 1983, Pre-Cret aceous rocks beneath the Georgia coastal plainregional implications: in Gohn, G.S., ed., Studies related to the Charleston, South Carolina, earthquake of 1886-tectonics and seismicity: U.S. Geological Survey Professional Paper 1313, p. L1-L42. Christenson, G., 1990, The Florida lineament: Transactions of the 40th Annual Meeting of Gulf Coast Association of Geological Societies, v. 40, p. 99-117. City of Punta Gorda, Water Resource Solutions, Inc., and Boyle Engineering Corporation, 2001, City of Punta Gorda injection well project well completion report: 41 p. plus appendices. Clayton, J.M., 1994, Final report of drilling and t esting activities, ROMP 39 (Oak Knoll), Manatee County, Florida: Brooksville, Southwest Florid a Water Management District, Geohydrologic Data Section, Resource Data Department, 23 p. plus figures, tables and appendices. ______, 1999, ROMP 12 Prairie Creek final report drilling and testing program southern district water resource assessment project DeSoto County, Florida: Brooksville, Southwest Florida Water Management District, Geohydrologic Data Section, Resource Data Department, 57 p. plus appendices. Coffin, J.E., and Fletcher, W.L., 1992, Water Resour ces Data, Florida, Water Year 1992: U.S. Geological Survey Water Data Report FL-92-3B, 249 p. Compton, J.S., Hodell, D.S., Garrido, J.R., and Mallins on, D.J., 1993, Origin and age of phosphorite from the south-central Florida Platform: Relation of phosphogenesis to sea-le vel fluctuations and 13C excursions: Geochimica et Cosmochi mica Acta, v. 57, p. 131-146. Cooke, C.W., 1945, Geology of Florida: Florida Geological Survey Bulletin 29, 342 p. Cooke, C.W. and Mossom, S., 1929, Geology of Florida, in Florida Geological Survey 20th Annual Report 1927-1928, p. 29-228. Cooke, C.W., and Mansfield, W.C., 1936, Suwannee Limestone of Florida: Geological Society of America Proceedings, p. 71-72. Copeland, R.E., 2003a, Florida spring classificatio n system and spring glossary: Florida Geological Survey Special Publication 52, 17 p. ______, 2003b, Assessment of long term trends (decades) in Florida spring water quality: Program with Abstracts, The Sixty-Seventh Annual Meeting of the Florida Academy of Sciences, Orlando, v. 66, Supp. 1, p. 53. Copeland, R.E., Upchurch, S., Scott, T., Kromhout, C., Arthur, J., and Means, G, Hydrogeologic units of Florida: Florida Geological Survey Special Publication 28 (Revised), (in review). Corral, M.A., Jr., and Wolansky, R. M., 1984, Generalized thickness and c onfiguration of the top of the intermediate aquifer, west-central Florida: U.S. Geological Survey Water-Resources Investigations Report 84-4018, 1 sheet. Covington, J.M., 1993, Neogene nannofossils of Florida, in Zullo, V.A., Harris, W.B., Scott, T.M., and Portell, R.W., eds., The Neogene of Florida and adjacent regions: Florida Geological Survey Special Publication 37, 112 p.

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BULLETIN NO. 68 85 Crumpacker, D.W., 1992, Chapter 1-Natural Environments: Ecosystems, in Fernald, E.A. and Purdum, E.D., eds., Water Resources Atlas of Florida: Tallahassee, Florida State University, 280 p. Cunningham, K.J., McNeill, D.F., Guertin, L.A., Ciesielski, P.F., Scott, T.M. and de Verteuil, L., 1998, New Tertiary stratigraphy for the Florida Keys an d southern peninsula of Florida: Geological Society of America Bulletin, v. 110, p. 231-258. Cunningham, K.J., Locker, S.D., Hine, A.C., Bukry, D., Barron, J.A., and Guertin, L.A., 2001, Surfacegeophysical characterization of groundwater systems of the Caloosahatchee River Basin, Southern Florida: U.S. Geological Survey Wa ter-Resources Investigations Report 01-4084. 76 p. Cushman, J.A., 1920, The American species of Orthophragmina and Lepidocyclina : U.S. Geological Survey Professional Paper 125-D, p. 39-105. Cushman, J.A., and Ponton, G.M., 1932, The Foramini fera of the upper, middle and part of the lower Miocene of Florida: Florida Geological Survey Bulletin 9, 147 p. Dall, W.H., 1887, Notes on the geology of Florida: American Journal of Science, 3rd series, v. 34, p. 161170. Dall, W.H., and Harris, G.D., 1892, Correlation papers -Neocene: U.S. Geological Survey Bulletin 84, 349 p. Davis, J., Johnson, R., Boniol, D., and Rupert, F., 20 01, Guidebook to the correlation of geophysical well logs within the St. Johns River Water Management District: Florida Geological Survey Special Publication 50, 114 p. DeHan, R., (compiler), 2004, Workshop to develop blue prints for the management and protection of Florida springs: Florida Geological Su rvey Special Publication 51, CD-ROM. Deuerling, R., 1981, Environmental Geology Series – Tarpon Springs Sheet: Florida Geological Survey Map Series 99, scale: 1:250,000, 1 sheet. DeWitt, D.J., 1990, ROMP TR16-2 Van Buren Road monitor wellsite, Pasco County, Executive Summary: Brooksville, Southwest Florida Water Management District. ______, 2003, Submarine springs and other karst featur es in the offshore waters of the Gulf of Mexico and Tampa Bay: Brooksvillle, Southwest Florid a Water Management District, 36 p. plus appendices. DuBar, J.R., 1958, Stratigraphy and paleontology of th e late Neogene starata of the Caloosahatchee River area of southern Florida: Florida Geological Survey Bulletin 40, 267 p. ______, 1962, Neogene biostratigraphy of the Charlotte Harbor area in southwestern Florida: Florida Geological Survey Bulletin 43, 83 p. Duerr, A.D., 2001, Potentiometric surfaces of the In termediate aquifer system, West Central Florida, May, 2001: U.S. Geological Survey Open-File Report 01-309, 1 sheet.

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FLORIDA GEOLOGICAL SURVEY 86 Duerr, A.D., and Enos, G.M., 1991, Hydrogeology of the intermediate aquifer system and upper Floridan aquifer, Hardee and DeSoto Counties, Florida: U.S. Geological Survey Water-Resources Investigations Report 90-4104, 46 p. Duncan, J.G., Evans, W.L., III, and Taylor, K,L., 1994, Geologic framework of the lower Floridan aquifer system, Brevard County, Florida: Florida Geological Survey Bulletin 64, 90 p. Dunham, R.J., 1962, Classification of carbonate rocks according to depositional texture, in Ham, W.E., ed., Classification of carbonate rocks: American Association of Petroleum Geologists Memoir 1, p. 108-121. Evans, M.W., and Hine, A.C., 1991, Late Neogene sequence stratigraphy of a carbonate-siliciclastic transition: Southwest Florida: Geological Society of America Bulletin, v. 103, p. 679-699. Evans, M.W., Snyder, S.W., and Hine, A.C., 1994, High-resolution seismic expression of karst evolution within the Upper Florida aquifer system, Crooke d Lake, Polk County, Florida: Journal of Sedimentary Research, v. B-64, no. 2, p. 232-244. Fetter, C.W., 2001, Applied Hydrogeology: New Jersey, Prentice Hall, 598 p. Florida Department of Community Affairs and Florid a Department of Environmental Protection, 2002, Protecting Florida’s springs: Land use planning strategies and best management practices, Tallahassee, 124 p. Freas, D.H., and Riggs, S.R., 1968, Environments of phosphorite deposition in the central Florida phosphate district, in Brown, L.F., ed., Fourth forum on ge ology of industrial minerals: Austin, University of Texas, Bureau of Economic Geology, p. 117-128. Gaswirth, S.B., 2004, Maturation of regional dolomite bodies in the Late Eocene Ocala Limestone and Early Oligocene Suwannee Limestone, west-central Florida: Processes and effects [PhD Dissertation]: Boulder, University of Colorado, 254 p. Gaswirth, S.B., Budd, D.A., and Crawford, B.R., 2006, Textural and stratigraphic controls on fractured dolomite in a carbonate aquifer system, Ocala Limestone, west-central Florida: Sedimentary Geology, v. 184, p. 241-254. Gates, M.T., 2001, Hydrogeology of the ROMP 16.5 Fort Ogden monitor well site DeSoto County, Florida Phase Two deep exploratory drilling an d monitor well construction: Brooksville, Southwest Florida Water Management District, Geohydrologic Data Section, Resource Data Department, 25 p. plus appendices. ______, 2006, Hydrogeology of the ROMP 74X Davenport monitor well Site, Polk County, Florida, Final Report: Brooksville, Southwest Florida Water Ma nagement District, 23 p. plus appendices. Gilboy, A.E., 1983, A correlation between lithology a nd natural gamma logs within the Alafia Basin of the Southwest Florida Water Management Dist rict: Brooksville, Southwest Water Management District, 7 p. plus plates.

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BULLETIN NO. 68 87 ______, Hydrogeology of the Southwest Florida Wa ter Management District: Brooksville, Southwest Florida Water Management District Technical Report 85-01, 18 p. Gohn, G.S., 1988, Chapter 7-Late Mesozoic and early Cenozoic geology of the Atlantic coastal plain: North Carolina to Florida, in Sheridan, R.E., and Grow, J.A., eds., The Geology of North America v.1-2, The Atlantic Co astal Margin: Boulder, Geological Society of America, p. 107130. Gomberg, D.N., 1975, Regional observation and m onitor-well program (ROMP): Purpose and Plan: Brooksville, Southwest Florida Water Management District, 37 p. Green, R., Arthur, J.D., and DeWitt, D., 1995, Lithos tratigraphic and hydrostratigraphic cross sections through Hillsborough and Pinellas Counties, Florida: Florida Geological Survey Open-File Report 61, 16 p. Green, R., Means, G.H., Scott, T., Arthur, J., and Campbell, K., 1999, Surficial and bedrock geology of the eastern portion of the U.S.G.S. 1:100,000 scale Arcadia quadrangle, south-central Florida: Florida Geological Survey Open-File Map Series 88, 8 sheets. Greenhalgh, T., 2004, Florida’s first magnitude springsheds: Florida Geological Survey Poster 12. Hammes, U., 1992, Sedimentation patterns, sequence stratigraphy, cyclicity and diagenesis of early Oligocene carbonate ramp deposits, Suwannee Formation, southwest Florida, USA.: [Ph.D. dissertation]: Boulder, University of Colorado, 344 p. Hancock, M., and Basso, R., 1993, Computer model of groundwater flow in the northern Tampa Bay: Brooksville, Southwest Florida Water Management District, 120 p. Hanshaw, B.B., and Back, W., 1972, On the origin of dolomites in the Tertiary aquifer of Florida, in Puri, H.S., ed., Proceedings of the Seventh Forum on Geology of Industrial Minerals: Tallahassee, Florida Department of Natural Resources, Bureau of Geology Special Publication 17, p. 139-153. Hartnett, F.M., ed., 2000, Florida’s springs strategies for protection and restoration: Tallahassee, The Florida Springs Task Force, 59 p. Healy, H.G., 1974, Water levels in artesian and nonartesian aquifers of Florida, 1971-72: Florida Geological Survey Information Circular 85, 94 p. ______, Terraces and shorelines of Florida: Flor ida Bureau of Geology Map Series 71; scale approximately 1:2,000,000, 1 sheet. Heatherington, A.L., and Mueller, P.A., 1997, Chapte r 3-Geochemistry and origin of Florida crustal basement terranes, in Randazzo, A.F. and Jones, D.D., eds ., The Geology of Florida: Gainesville, University Press of Florida, p. 27-38. Heilprin, A., 1887, Exploration on the west coast of Florida and in the Okeechobee wilderness: Wagner Free Institute of Science Transactions, v. 1, p. 1-134. Hickey, J.J., 1982, Hydrogeology and results of injec tion tests at waste-injection test sites in Pinellas County, Florida: U.S. Geological Survey Water-Supply Paper 2183, 42 p.

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FLORIDA GEOLOGICAL SURVEY 88 ______, An assessment of the flow of variable-sal inity ground water in the middle confining unit of Floridan aquifer system, west-central Florida: U.S. Geological Survey Water-Resources Investigations Report 89-4142, 13 p. Hine, A.C., 1997, Chapter 11-Structural and paleo ceanographic evolution of the Florida Platform, in Randazzo, A.F. and Jones, D.D., eds., The Geolog y of Florida: Gainesville, University Press of Florida, p. 169-194. Hine, A.C., Suthard, B., Locker, S.D., Cunningham, K.J., Duncan, D.S., Evans, M.W., and Morton, R.A., Karst subbasins and their relationship to transport of Tertia ry siliciclastic sediments on the Florida platform, in Swart, P., Eberli, G., McKenzie, J ., eds., Perspectives in Sedimentary Geology: A Tribute to the Career of Robert Nathan Ginsburg: International Association of Sedimentologists Special Publication 41: Oxford, UK, Blackwell Publishing, (in press). Huddlestun, P.F., 1988, A revision of lithostratigraphic units of the coastal plain of Georgia – The Miocene through Holocene: Georgia Geological Survey Bulletin 104, 162 p. ______, Revision of the lithostratigraphi c units of the coastal plain of Georgia – the Oligocene: Georgia Geologic Survey Bulletin 105, 152 p. Hutchinson, C.B., 1992, Assessment of hydrogeol ogic conditions with emphasis on water quality and wastewater injection, southwest Sarasota and we st Charlotte Counties, Florida: U.S. Geological Survey Water-Supply Paper 2371, 74 p. Johnson, R.A., 1986, Shallow stratigraphic core tests on file at the Florida Geological Survey: Florida Geological Survey Information Circular 103, 431 p. Johnston, K., Ver Hoef, J.M., Krivoruchko, K., a nd Lucas, N., 2001, Using ArcGis Geostatistical Analyst: Redlands, ESRI Incorporated, 300 p. Johnston, R.H., and Bush, P.W., 1988, Summary of the hydrology of the Floridan Aquifer system in Florida and in parts of Georgia, South Ca rolina and Alabama: U.S. Geological Survey Professional Paper 1403-A, 24 p. Jones, I.C., Vacher, H.L., and Budd, D.A., 1993, Transport of calcium, magnesium and SO4 in the Floridan aquifer, west-central Florida: Implicati ons to cementation rates: Journal of Hydrology, v. 143, p. 455-480. Jones, G.W., Upchurch, S.B., Champion, K.M., and Dewitt, D.J., 1997, Waterquality and hydrology of the Homosassa, Chassahowitzka, Weeki Wachee and Aripeka spring complexes, Citrus and Hernando Counties, Florida –Origin of increasing nitrate Concentrations: Brooksville, Southwest Florida Water Management District, Ambient Groundwater Quality Monitoring Program, 167 p. Jones, G.W., Upchurch, S.B., and Champion, K.M., 1998, Origin of nutrients in groundwater discharging from the King’s Bay springs: Brooksville, Southwest Florida Water Management District, Ambient Groundwater Monitoring Program, 159 p. Jorgensen, D. G., Helgeson, J. O., and Imes, J. L., 1993, Aquifer systems underlying Kansas, Nebraska, and parts of Arkansas, Colorado, Missouri, New Mexico, Oklahoma, South Dakota, Texas, and Wyoming--Geohydrologic framework: U.S. Geological Survey, Professional Paper 1414-B, 238 p.

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BULLETIN NO. 68 89 Joyner, B.F., and Sutcliffe, H., Jr., 1976, Water resources of the Myakka River basin area, southwest Florida: U.S. Geological Survey Water-Resources Investigations 76-58, 87 p. Katz, B.G., 1992, Hydrochemistry of the upper Floridan aquifer, Florida: U.S. Geological Survey WaterResources Investigations Report 91-4196, 37 p. Kauffman, S.J., and Herman, J.S., 1993, Chemical evolution of groundwater in a lithologically heterogeneous aquifer: water-rock interactions with clays and carbonates: Geological Society of America 1993 Annual Meeting Abstracts with Programs, v. 25, p. 376. King, K.C., 1979, Tampa Formation of peninsular Fl orida: A formal definition [MS Thesis]: Tallahassee, Florida State University, 83 p. Klitgord, K.D., Dillon, W.P., and P openoe, P., 1983, Mesozoic tectonics of the southeastern Unites States coastal plain and continental margin, in Gohn, G.S., ed., Studies related to the Charleston, South Carolina earthquake of 1866 – tectonics and seismicity: U.S. Geological Survey Professional Paper 1313, p. P1-P15. Kohout, F.A., 1965, A hypothesis concerning cyclic flow of salt water related to geothermal heating in the Floridan Aquifer: New York Academy of Science Trans. 1965, p. 249-271. Knapp, M.S., 1977, The northern Brooksville Ridge, A case for topographic inversion: Florida Scientist v. 40:25 (suppl.). ______, Environmental Geology Seri es – Gainesville Sheet: Florida Geological Survey Map Series 79, scale: 1:250,000, 1 sheet. ______, 1980, Environmental Geology Series – Tampa Sheet: Florida Geological Survey Map Series 97, scale: 1:250,000, 1 sheet. Knochenmus, L.A., 2006, Regional ev aluation of the hydrogeologic framework, hydraulic properties, and chemical characteristics of the intermediate a quifer system underlying southern west-central Florida: U.S. Geological Survey Scientific Investigations Report 2006-5013, 46 p. Knochenmus, L.A., and Bowman, G., 1998, Transmissivity and water qua lity of water-producing zones in the intermediate aquifer system, Sarasota C ounty, Florida: U.S. Geological Survey WaterResources Investigations Report 98-4091, 27 p. Knochenmus, L.A., and Yobbi, D.K ., 2001, Hydrology of the Coastal Springs Groundwater Basin and adjacent parts of Pasco, Hernando and Citrus Counties, Florida: U.S. Geological Survey WaterResources Investigations Report 01-4230, 88 p. Lane, E., 1980, Environmental Geology Series – West Palm Beach Sheet: Florida Geological Survey Map Series 100, scale 1:250,000, 1 sheet. Lane, E., Knapp, M.S., and Scott, T., 1980, Enviro nmental Geology Series – Ft. Pierce Sheet: Florida Geological Survey Map Series 80, scale 1:250,000, 1 sheet. Laney, R.L. and Davidson, C.B., 1986, Aquifer-nomenclature guidelines: U.S. Geological Survey OpenFile Report 86-534, 46 p.

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FLORIDA GEOLOGICAL SURVEY 90 LaRoche, J.J., 2004, ROMP 35 West DeSoto Monitor well site DeSoto County, Florida Final Report exploratory coring monitor-well construction aqui fer performance testing: Brooksville, Southwest Florida Water Management District, Resour ce Data Section, Resource Conservation and Development Department, 44 p., plus appendices. Law Environmental, Inc., 1989, Results of explorat ory/monitor well construction and testing, Knight Trail Park: report prepared for the Florida Depa rtment of Environmental Regulation, file no. UC58-125241. Lazareva, O., and Pichler, T., 2007, Naturally oc curring arsenic in the Miocene Hawthorn Group, southwestern Florida: Potential implication for phosphate mining: Applied Geochemistry, v. 22, p. 953-973. Lee, R.A., 1998, Coastal springs project drilling and testing report freshwater coastal monitor wellsites Pasco, Hernando and Citrus Counties, Florida: Brooksville, Southwest Florida Water Management District, 9 p. Levin, H.L., 1957, Micropaleontology of the Oldsmar Limestone (Eo cene) of Florida: Micropaleontology, v. 3, p. 137-154. Lewelling, B.R., Tihansky, A.G., and Kindinger, J. L., 1998, Assessment of the hydraulic connection between water and the Peace River, west-centr al Florida: U.S. Geological Survey WaterResources Investigations Report 97-4211, 96 p. Loizeaux, N.T., 1995, Lithologic and hydrogeologi c frameworks for a carbonate aquifer: evidence for facies controlled hydraulic conductivity in the Ocala Formation, West-Central Florida [M.S. Thesis]: Boulder, University of Colorado, 298 p. Macfarlane, P. A., 2000, Revisions to the nomenclatur e for Kansas aquifers: Current research in earth sciences: Kansas Geological Survey Bulletin 244, Part 2: http://www.kgs.ku.edu/Current/2000/m acfarlane1.html, (January, 2007). Maliva, R., Walker, C.W., and Callahan, E.X., 2001, Hydrogeology of the lower Floridan aquifer “Boulder Zone” of southwest Florida, in Missimer, T.M., and Scott, T.M., eds., Geology and hydrogeology of Lee County, Fl orida: Durward H. Boggess Memorial Symposium: Florida Geological Survey Special Publication 49, p. 167-182. Maliva, R.G., Kennedy, G.P., Martin, W.K., Missimer, T.M., Owosina, E.S., and Dickson, J.A.D., 2002, Dolomitization-induced aquifer heterogeneity: evidence from the Upper Floridan aquifer, southwest Florida: Geological Society of America Bulletin, v. 114, p. 419-427. Mansfield, W.C., 1939, Notes on the upper Tertiary and Pleistocene mollusks of peninsular Florida: Florida Geological Survey Bulletin 18, 75 p. Marella, R.L., 2004, Water withdrawals, use, dischar ge, and trends in Florida, 2000: U.S. Geological Survey Scientific Investiga tions Report 2004-5151, 50 p. McCartan, L., Weedman, S.D., Wingard, G.L., Edwa rds, L.E., Sugarman, P.J., Feigenson, M.D., Buursink, M.L., and Libarkin, J.C., 1995, Age and diagenesis of the upper Floridan aquifer and the intermediate aquifer system in southwestern Florida: U.S. Geological Survey Bulletin 2122, 26 p.

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BULLETIN NO. 68 91 Metz, P.A., 1995, Hydrogeology and simulated effects of groundwater withdrawals for citrus irrigation, Hardee and DeSoto Counties, Florida: U.S. Geological Survey Water-Resources Investigations Report 93-4158, 83 p. Meyer, F.W., 1989, Hydrogeology, groundwater move ment, and subsurface storage in the Floridan aquifer system in southern Florida: U.S. Geol ogical Survey Professional Paper 1403-G, 59 p. Miller, J.A., 1986, Hydrogeologic Framework of the Flor idan aquifer system in Florida and in Parts of Georgia, Alabama and South Carolina: U.S. Geological Survey Professional Paper 1403-B, 91 p. ______, Geohydrologic data from the Floridan aquifer sy stem in Florida and in parts of Georgia, South Carolina and Alabama: U.S. Geological Survey Open-File Report 88-86, 387 p. ______, 1997, Chapter 6-Hydrogeology of Florida, in Randazzo, A.F., and Jones, D.D., eds., The Geology of Florida: Gainesville, University Press of Florida, p. 69-88. Missimer, T.M., 1993, Stratigraphic relationships of sediment facies within the Tamiami Formation of southwest Florida: Proposed intraformational correlations, in Scott, T.M., and Allmon, W.D. eds., Plio-Pleistocene stratigraphy and paleontology of southern Florida: Florida Geological Survey Special Publication 36, p. 63-73. ______, Late Neogene geology of nor thwestern Lee County, Florida, in Missimer, T.M. and Scott, T.M., eds., Geology and hydrogeology of Lee Count y, Florida: Durward H. Boggess Memorial Symposium: Florida Geological Survey Special Publication 49, p. 21-34. ______, 2002, Late Oligocene to Pliocene evolution of the central portion of the south Florida platform: mixing of siliciclastic and carbonate sediments: Florida Geological Survey Bulletin 65, 184 p. Missimer, T.M., and Gardner, R.A., 1976, High-r esolution seismic reflection profiling for mapping shallow aquifers in Lee County, Florida: U.S. Geological Survey Water-Resources Investigations 76-45, 30 p. Missimer, T.M, McNeill, D.F., Ginsburg, R.N., Muelle r, P.A., Covington, J.M., and Scott, T.M., 1994, Cenozoic record of global sea level events in the Hawthorn Group and Tamaimi Formation on the Florida platform: Geological Society of America Ab stracts with Programs, v. 26, no. 7, p. A 151. Missimer, T.M., and Ginsburg, R.N., 1998, Homogenized carbonates and siliciclastics in the Tertiary of southwest Florida: Gulf Coast Association of Geological Societies Transactions, v. 48, p. 263274. Missimer, T.M., and Martin, W.K., 2001, The hydrogeology of Lee County, in Missimer, T.M., and Scott, T.M., eds., Geology and hydrogeology of Lee County Florida: Durward H. Boggess Memorial Symposium: Florida Geological Survey Special Publication 49, p. 91-139. Missimer, T.M., and Maliva, R.G., 2004, Tectonically induced fracturing, folding and groundwater flow in south Florida: Gulf Coast Association of Ge ological Societies Transactions, v. 54, p. 443-459. Montgomery Watson Americas, Inc., 1997, Charlotte County Utilities – West Port wastewater treatment plant injection well system – Injection Well IW-1 and Monitor Well DZMW-1 Drilling and Testing Report: report prepared for Ch arlotte County Utilities, unpaginated.

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FLORIDA GEOLOGICAL SURVEY 92 Moore, D.L., and Stewart, M.T., 1983, Geophysical signatures of fracture traces in a karst aquifer (Florida, U.S.A.): Journal of Hydrology, v. 61, p. 325-340. Neuendorf, K.K.E., Mehl Jr., J.P., and Jackson, J.A., 2005, Glossary of Geology, Fifth Edition: Alexandria, American Geological Institute, 779 p. North American Commission on Stratigraphic Nomenclatu re, 2005, North American stratigraphic code North American Commission on Stratigraphic Nomenclature: American Association of Petroleum Geologists Bulletin, v. 89, p. 1547 1591. O’Reilly, A.M., Spechler, R.M., and McGurk, B.E., 2002 , Hydrogeology and watercharacteristics of the lower Floridan aquifer in east-central Flor ida: U.S. Geological Survey Water-Resources Investigations Report 02-4193, 60 p. Ortiz, A., G., 2006, Potentiometric surface of the upper Floridan aquifer, west-central Florida, September 2005: U.S. Geological Survey Open-File Report 2006-1128; 1 sheet. Ortiz, A., G. and Blanchard, R.A, 2006, Potentiometric surface of the upper Floridan aquifer, west-central Florida, May 2005: U.S. Geological Survey Open-File Report 2006-1009; 1 sheet. Petuch, E.J., 1982, Notes on the Molluscan paleoecology of the Pinecrest beds at Sarasota, Florida with the description of Pyruella , a stratigraphically important new genus (Gastropoda: Melongindea): Proceedings of the Academy of Natural Scie nces of Philadelphia, v. 134, p. 12-30. ______, 1994, Atlas of Florida fossil shells: Evanston, Chicago Spectrum Press, 394 p. Pindell, J.L., 1985, Alleghenian recons truction and subsequent evolution of the Gulf of Mexico, Bahamas and Proto-Caribbean: Tectonics, v. 4, p. 1-39. Plummer, L.N., 1977, Defining reactions and mass tr ansfer in part of the Floridan aquifer: Water Resources Research, v. 13, p. 801-812. Poland, J.F., Lofgren, B.E., and Riley, F.S., 1972, Glossary of selected terms useful in studies of the mechanics of aquifer systems and land subsid ence due to fluid withdrawal: U.S. Geological Survey Water-Supply Paper 2025, 9 p. Price, R.E., 2003, Abundance and mineralogical association of naturally occurring arsenic in the Upper Floridan aquifer, Suwannee Limestone [MS Thesis]: Tampa, University of South Florida, 74 p. Pride, R.W., Meyer, F.W., and Cherry, R.N., 1966, Hydrology of Green Swamp area in central Florida: Florida Geological Survey Report of Investigations 42, p. 31-33. Puri, H.S., 1953, Zonation of the Ocala Group in peni nsular Florida [Abstract]: Journal of Sedimentary Petrology, v. 23, p. 130. Puri, H.S., and Vernon, R.O., 1964, Summary of the geology of Florida and a guidebook to the classic exposures: Florida Board of Conservation, Division of Geology, Special Publication no. 5 (revised), 225 p. Puri, H.S., Faulkner, G.L., and Winston, G.O., 1973, Hydrogeology of subsurface liquid-waste storage in Florida, in Braunstein, J., ed., Underground Waste Ma nagement and Artificial Recharge, v. 2: Menasha, The George Banta Co., p. 825-850.

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BULLETIN NO. 68 93 Puri, H.S., and Winston, G.O., 1974, Geologic framework of the high transmissivity zones in south Florida: Florida Geological Survey Special Publication 20, 101 p. Randazzo, A.F., 1997, Chapter 4 The sedimentary platform of Florida: Mesozoic to Cenozoic, in Randazzo, A.F., and Jones, D.D., eds., The Geology of Florida: Gainesville, University Press of Florida, p. 39-56. Randazzo, A.F., and Hickey E.W., 1978, Dolomitization in the Floridan aquifer: American Journal of Science, v. 278, p. 1177-1184. Randazzo, A.F., and Zachos, L.G., 1984, Classification a nd description of dolomite fabrics of rocks from the Floridan aquifer, USA: Sedimentary Geology, v. 37, p. 151-162. Randazzo, A.F., Kosters, M., Jones, D.S., and Port ell, R.W., 1990, Paleoecology of shallow-marine carbonate environments, Middle Eocene of peninsula Florida: Sedimentary Geology, v. 66: p. 111. Renken, R.A., 1998, Groundwater atlas of the Unite d States: Segment 5, Arkansas, Louisiana, Mississippi: U.S. Geological Survey Hydrologic Atlas 730-F, 28 p. Reese, R.S., 2000, Hydrogeology and the distribution of salinity in the Floridan aquifer system, southwestern Florida: U.S. Geological Survey Water-Resources Investigations Report 98-4253, 86 p. Reese, R.S. and Richardson, E., 2008, Synthesis of the hydrogeologic framework of the Floridan aquifer system and delineation of a major Avon Park permeable zone in central and southern Florida: U.S. Geological Survey Scientific I nvestigations Report 2007-5207, 60 p. Riggs, S.R., 1979a, Phosphorite sedimentation in Fl orida a model phosphogenic system: Economic Geology, v. 74, p. 285-314. ______, 1979b, Petrology of the Tertiary phosphorite system of Florida: Economic Geology, v. 74, p. 195-220. ______, 1984, Paleoceanographic mode l of Neogene phosphorite depositio n, US Atlantic continental margin: Science, v. 223, no. 4632, p. 123-131. Rupert, F.R., 1989, Selected Cenozoic benthic foraminifera from Florida: Florida Geological Survey Poster 2. Rupert, F., and Arthur, J.D., 1990, The geology and ge omorphology of Florida’s coastal marshes: Florida Geological Survey Open-File Report 34, 13 p. Ryder, P.D., 1982, Digital model of predevelopment flow in the Tertiary limestone (Floridan) aquifer system in west-central Florida: U.S. Geological Survey Water-Resources Investigations Report 81-54, 61 p. Ryder, P.D., 1985, Hydrology of the Floridan aquifer system in west-central Florida: U.S. Geological Survey Professional Paper 1403-F, 63 p.

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FLORIDA GEOLOGICAL SURVEY 94 Ryder, P.D., Johnson, D.M., and Gerhart, J.M., 1 980, Model evaluation of the hydrogeology of the Morris Bridge Wellfield and vicinity in westcentral Florida: U.S. Geological Survey Water Resources Investigations Report 80-29, 92 p. Sacks, L.A., 1996, Geochemical and isotopic compos ition of groundwater with emphasis on sources of sulfate in the upper Floridan aquifer in parts of Ma rion, Sumter and Citrus Counties, Florida: U.S. Geological Survey Water-Resources Inv estigations Report 95-4251, 47 p. Sacks, L.A., and Tihansky, A.B., 1996, Geochemical and isotopic composition of groundwater, with emphasis on sources of sulfate in the upper Floridan aquifer and intermediate aquifer system in southwest Florida: U.S. Geological Survey Water-Resources Investigations Report 96-4146, 54 p. Schmidt, W., 1997, Chapter 1 Geomorphology and physiography of Florida, in Randazzo, A.F., and Jones, D.D., eds., The Geology of Florida: Ga inesville, University Press of Florida, p. 1-12. Scott, T.M., 1978, Environmental Geology Series – Orlando Sheet: Florida Geological Survey Map Series 85, scale: 1:250,000, 1 sheet. ______, 1979, Environmental Geology Series – Dayt ona Beach Sheet: Florida Geological Survey, Map Series 93, scale 1:250,000, 1 sheet. ______, 1988, The lithostratigraphy of the Hawthorn Group (Miocene) of Florida: Florida Geological Survey Bulletin 59, 148 p. ______, 1991, A geological overview of Florida, in Scott, T.M., Lloyd, J.M., and Maddox, G., eds., Florida’s Groundwater Quality Monitoring Prog ram Hydrogeological Framework: Florida Geological Survey Special publication 32, p. 5-14. ______, 1992a, Chapter 3-Hydrostratigraphy, in Maddox, G.L., Lloyd, J.L., Scott, T.M., Upchurch, S.B., and Copeland, R., Florida’s groundwater quality monitoring program – Background hydrogeochemistry: Florida Geological Survey Special Publication No. 34, p. 6-12. ______, 1992b, A geological overview of Florida: Florida Geological Survey Open-File Report 50, 78 p. ______, 1992c, Coastal plains stratigraphy: the dich otomy of biostratigraphy and lithostratigraphy – A philosophical approach to an old problem, in Scott, T.M., and Allmon, W.D. eds., PlioPleistocene stratigraphy and paleontology of southe rn Florida: Florida Geological Survey Special Publication 36, p. 21-23. ______, 1993, Neogene lithostratigraphy of the Florida peninsula – problems and prospects, in Zullo, V.A., et al., eds., The Neogene of Florida a nd adjacent regions: Florida Geological Survey Special Publication 37, p. 1-2. ______, 1997, Chapter 5-Miocene to Holocene history of Florida, in Randazzo, A.F., and Jones, D.D., eds., The Geology of Florida: Gainesville, University Press of Florida, p. 57-67. ______, 2001, Text to accompany the geologic map of Florida (MS 146): Florida Geological Survey Open-File Report 80, 29 p. ______, 2004, The new geomorphic map of Florida: Geological Society of America Abstracts with Programs, v. 36, no. 5, p. 578.

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BULLETIN NO. 68 95 Scott, T.M., Wingard, G.L., Weedman, S.D., and Edward s, L. E., 1994, Reinterpretation of the peninsular Florida Oligocene, a multidisciplinary view: Geological Society of America Abstracts with Programs, v. 26, no. 7, p. A-151. Scott, T.M., Campbell, K.M., Rupert, F.R., Arthur, J.D., Missimer, T.M., Lloyd, J.M., Yon, J.W., and Duncan, J.G., 2001, Geologic map of the state of Florida: Florida Geological Survey Map Series 146, scale approx. 1:750,000. Scott, T.M., Means, G.H., Meegan , R.P., Means, R.C., Upchurch, S.B., Copeland, R.E., Jones, J., Roberts, T., and Willet, A., 2004, Springs of Flor ida: Florida Geological Survey Bulletin 66, 377 p. Seaber, P. R., 1988, Hydrostratigraphic units in hydrogeology, in Back, W., et al, eds., The Geology of North America: Geological Society of America, v. O-2, p. 94. Sellards, E.H., 1919, Geologic sections across the Everglades of Florida: Florida Geological Survey 12th Annual report, p. 67-76. Seplveda, N., 2002, Simulation of grou nd-water flow in the intermediate and Floridan aquifer systems in peninsular Florida: U.S. Geological Survey Wa ter-Resources Investigations Report 02-4009, 130 p. Sinclair, W.C., Stewart, J.W., Knutilla, R.L., Gilboy, A.E., and Miller, R.L., 1985, Types, features and occurrence of sinkholes in the karst of west-cen tral Florida: U.S. Geological Survey WaterResources Investigations Report 85-4126, 81 p. Smith, D.L., 1982, Review of the tectonic history of the Florida basement: Tectonophysics, v. 88. p. 1-22. Smith, D.L. and Griffin, G.M., (eds.), 1977, The ge othermal nature of the Floridan Plateau: Florida Geological Survey Special Publication 21, 161 p. Smith, D.L., and Lord, K.M., 1997, Chapter 2-Tectonic evolution and geophysics of the Florida basement, in Randazzo, A.F., and Jones, D.D., eds., The Geology of Florida: Gainesville, University Press of Florida, , p. 13-26. Southeastern Geological Society (Ad Hoc Committee on Florida hydrogeologic unit definition), 1986, Hydrogeological Units of Florida: Florida Geological Survey Special Publication 28, 8 p. Southwest Florida Water Management District, 2006a , Regional Water Supply Plan (December 1, 2006): Brooksville, Southwest Florida Water Manageme nt District, 255 p., plus appendices. Southwest Florida Water Management District, 20 06b, Aquifer characteristics within the Southwest Florida Water Management District, July 2005: Southwest Florida Water Management District Report 99-1, Fourth Edition, re vised February 2006, 28 p. Sprinkle, C.R., 1989, Geochemistry of the Floridan aquifer system in Florida and parts of Georgia, South Carolina and Alabama: U.S. Geological Survey Professional Paper 1403-I, 105 p. Sproul, C.R., Boggess, D.H., and Woodard, H.J., 1972, Saline-water intrusion from deep artesian sources in the McGregor Isles area of Lee County, Fl orida: Florida Geological Survey Information Circular 75, 30 p.

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FLORIDA GEOLOGICAL SURVEY 96 Spechler, R., and Kroening, S.E., 2007, Hydrology of Polk County, Florida: U.S. Geological Survey Scientific Investigations Report 06-5320, 114 p. Steinkampf, W.C., 1982, Origins and distribution of sa line groundwaters in the Floridan aquifer in coastal southwest Florida: U.S. Geological Survey Wa ter-Resources Investigations Report 82-4052, 38 p. Stewart, H.G., 1966, Groundwater resources of Po lk County: Florida Geological Survey Report of Investigations 44, 170 p. Swancar, A., and Hutchinson, C.B., 1995, Chemi cal and isotopic composition and potential for contamination of water in the upper Floridan aquifer, west-central Florida, 1986-89: U.S. Geological Survey Water-Supply Paper 2409, 70 p. Tanner, W.F., 1960a, Florida coastal classification: Transactions of the Gulf Coast Association of Geological Societies v. 10, p. 259-266. ______, 1960b, Bases for coastal classification: Southeastern Geology v. 1, p. 13-22. Tihansky, A.B., 1999, Sinkholes, west-central Florida, in Galloway, D., et al., eds. Land subsidence in the United States: U.S. Geological Survey Circular 1182, p. 121-140. ______, 2005, Effects of aquifer heterogeneity on groun dwater flow and chloride concentrations in the Upper Floridan aquifer near and within an active pumping well field, west-central Florida: U.S. Geological Survey Scientific Inves tigations Report 2004-5268, 75 p. Tihansky, A.B., Arthur, J.D., and DeWitt, D.W., 19 96, Sublake geologic structure from high-resolution seismic-reflection data from four sinkhole lakes in the Lake Wales Ridge, central Florida: U.S. Geological Survey Open-File Report 96-224, 71 p. Torres, A.E., Sacks, L.A., Yobbi, D.K., and K nochenmus, L.A., 2001, Hydrogeologic framework and geochemistry of the intermediate aquifer system in parts of Charlotte, DeSoto and Sarasota Counties, Florida: U.S. Geological Survey Wate r-Resources Investigations Report 01-4015, 74 p. Trommer, J.T., 1987, Potential for pollution of the upper Floridan aquifer from five sinkholes and an internally drained basin in west-central Florida: U.S. Geological Survey Water-Resource Investigations Report 87-4013, 103 p. ______, 1993, Description and monitoring of the saltwat er-freshwater transition zone in aquifers along the west-central coast of Florida: U.S. Geologi cal Survey Water-Resources Investigations Report 93-4120, 56 p. Upchurch, S.B., 1992, Quality of water in Florida’s aquifer systems, in Maddox, G.L., Lloyd, J.M., Scott, T.M., Upchurch, S.B., and Copeland, R., eds., Florida’s groundwater quality monitoring program – Background hydrogeochemistry: Florida Geological Survey Special Publication 34, p. 12-51. Upchurch, S.B., Strom, R.N., and Nuckels, M.G., 1982, Silicification of Miocene rocks from central Florida; in Scott, T.M., and Upchurch, S.B., eds., Miocene of the southeastern United States: Florida Geological Survey Special Publication No. 25, p. 251-284.

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BULLETIN NO. 68 97 U.S. Department of Agriculture, Natural Resource Conservation Service, 2002, National Soil Survey Handbook, title 430-VI, USDA: http://soils.usd a.gov/technical/handbook/ (January, 2007). U.S. Geological Survey, 1990, Water resources data – Florida, Water year 1990, Volume 3B, southwest Florida groundwater: U.S. Geological Survey Water-Data Report FL-90-3B, 241 p. ______, 1998, Water resources data Florida, Wa ter year 1998, Volume 3B, southwest Florida groundwater: U.S. Geological Survey Water-Data Report FL-98-3B, 323 p. Vacher, H.L., Jones, G.W., and Stebnisky, R.J., 1993, Heterogeneity of the surficial aquifer system in west central Florida, in Scott, T.M., and Allmon, W.D., eds., Plio-Pleistocene stratigraphy and paleontology of southern Florida: Florida Geologi cal Survey Special Publication 36, p. 93-99. Vernon, R.O., 1951, Geology of Citrus and Levy C ounties, Florida: Florida Geological Survey Bulletin 33, 256 p. ______, 1970, The beneficial uses of zones of high tr ansmissivities in the Florida subsurface for water storage and waste disposal: Florida Bureau of Geology Information Circular 70, 39 p. Vernon, R.O., and Puri, H.S., 1964, Geologic map of Florida: Florida Bureau of Geology Map Series 18, scale approximately 1: 2,000,000, 1 sheet. ViroGroup, Inc., 1995, Completion report for Burnt Store utilities class I injection well system Punta Gorda, Charlotte County, Florida: report prepared for Charlotte County, 55 p. plus Appendices. Ward, W.C., Cunningham, K.J., Renken, R.A., Wack er, M.A., and Carlson, J.I., 2003, Sequencestratigraphic analysis of the regional observation monitoring program (ROMP) 29A test corehole and its relation to carbonate porosity and regional transmissivity in the Floridan aquifer system, Highlands County, Florida: U.S. Geological Survey Open-File Report 03-201, 34 p. Webb, S.D. and Crissinger, D.B., 1983, Stratigraphy and vertebrate paleontology of the central and southern phosphate districts of Florida, in The Central Florida Phosphate District – Field Trip Guidebook, Geological Society of America, Southeastern Section Annual Meeting, p. 28-72. Weinberg, J.M., and Cowart, J.B., 2001, Hydrogeol ogic implications of uranium-rich phosphate in northeastern Lee County, in Missimer, T.M., and Scott, T.M., eds., Geology and hydrogeology of Lee County Florida: Durward H. Boggess Memorial Symposium: Florida Geological Survey Special Publication 49, p. 151-166. Wheeler, W., Owen, R., and Johnson, T., 1998, Ch apter 12-Southwest Florida Water Management District, in Fernald, E.A., and Purdum, E.D., eds., Wate r resources atlas of Florida: Tallahassee, Florida State University, 312 p. White, W.A., 1970, The geomorphology of the Florida peninsula: Florida Geological Survey Bulletin 51, 164 p. Wicks, C.M., and Herman, J.S., 1994, The effect of a confining unit on the geochemical evolution of groundwater in the upper Floridan aquifer system: Journal of Hydrology, v. 153, p. 139-155. Wicks, C.M., and Herman, J.S., 1996, Regional hydr ogeochemistry of a modern coastal mixing zone: Water-Resources Research, v. 32, p. 401-407.

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FLORIDA GEOLOGICAL SURVEY 98 Wilson, W.E., 1977, Groundwater resources of DeSoto and Hardee Counties, Florida: Florida Bureau of Geology Report of Investigation 83, 102 p. Wilson, W.L., and Beck, B.F., 1988, Evaluating sinkhole hazards in mantled karst terrane, in Sitar N., ed., Geotechnical aspects of karst terrains; New York, Am erican Society of Civil Engineers, p. 1-24. Wingard, G.L., Weedman, S.D., Scott, T.M., Edwards, L.E., and Green, R.C., 1994, Preliminary analysis of integrated stratigraphic data from the South Ve nice corehole, Sarasota County, Florida: U.S. Geological Survey Open-File Report, 95-3, 129 p. Winston, G.O., 1971, Regional structure, stratigraphy a nd oil possibilities of the South Florida basin: Gulf Coast Association of Geological Societies Transactions, v. 21, p. 15-29. Winston, G.O., 1976, Florida’s Ocala Uplift is not an uplift: Bulletin of the American Association of Petroleum Geologists v. 60, p. 992-94. Winston, G.O., 1996, The Boulder Zone dolomites of Florida, Volume 2: Paleogene zones of the southwestern peninsula: Miami Geological Society, 64 p. Wolansky, R.M., and Corral, M.A., Jr., 1985, Aquifer tests in west-central Florida, 1952-76: U.S. Geological Survey Water-Resources Inv estigations Report 84-4044, 127 p. Wolansky, R.M., and Garbode, J.M., 1981, Generalized thickness of the Floridan aquifer, Southwest Florida Water Management District: U.S. Geological Survey Open-File Report 80-1288, scale 1:500,000, 1 sheet. Wolansky, R.M., Spechler, R.K., and Buono, A., 1979a , Generalized thickness of the surficial deposits above the confining bed overlying the Floridan aquifer, Southwest Florida Water Management District: U.S. Geological Survey Open-File Report 79-1071, scale 1:250,000, 1 sheet. Wolansky, R.M., Barr, G.L., and Spechler, R.M., 1979b, Configuration of the bottom of the Floridan aquifer, Southwest Florida Water Management District: U.S. Geological Survey Open-File Report 79-1490, scale 1:250,000, 1 sheet. Wolansky, R.M., Barr, G.L. and Spechler, R.M., 1980, Configuration of the top of the highly permeable dolomite zone of the Floridan aquifer, Southw est Florida Water Management District: U.S. Geological Survey Open-File Report 80-433, scale 1:250,000, 1 sheet. Wolansky, R.M., Haeni, F.P., and Sylvester, R.E ., 1983, Continuous seismic-reflection survey defining shallow sedimentary layers in the Charlotte Harbor and Venice areas, southwest Florida: U.S. Geological Survey Water-Resources Investigations Report 82-57, 83 p. Yobbi, D.K., 1996, Analysis and simulation of groundwat er flow in Lake Wales Ridge and adjacent areas of central Florida: U.S. Geological Survey Water-Resources Investigations Report 94-4254, 82 p.

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BULLETIN NO. 68 99 APPENDIX 1. COMMENTARY ON FLORIDA HYDROSTRATIGRAPHIC NOMENCLATURE. Considerable debate exists with regard to hydrostratigraphic nomenclature in the study area. While it is beyond the scope of the present study to formally rename principal aquifer systems in southwestern Florida, especially given the pending recommendati ons of the CFHUD II (Copeland et al., in review), some discussion is warranted. This is due in part to the lack of a formal hydrostratigraphic code (Seaber, 1988), unlike that available for lithostratigraphic nomenclature (North American Commission on Stratigraphic Nomenclature, 2005). Hydrostratigraphi c unit definitions and nomenclatural guidelines, however, do exist. Poland et al. (1972) define an aqui fer system as “A heterogeneous body of intercalated permeable and poorly permeable material that func tions regionally as a water-yielding hydraulic unit; it comprises two or more permeable beds separated at least locally by aquitards that impede groundwater movement but do not greatly affect the regional continuity of the system.” Neuendorf et al. (2005) define an aquifer system as “A heterogeneous body of intercalated permeable and less permeable material that acts as a water-yielding hydraulic unit of regional ex tent.” According to nomenclature guidelines set forth by Laney and Davidson (1986), aquifer system names should not be derive d from relative position. In consideration of these definiti ons and guidelines, all or part of the SAS and IAS/ICU may be considered inappropriately named. On the other ha nd, Macfarlane (2000) suggests that aquifer system names should be retained if they are entrenched in th e scientific literature or legally defined in a state’s regulatory framework. With regard to naming confining units, Laney and Davidson (1986) suggest that the name could be based on the aquifer it confines (i.e., the aquifer it ove rlies). Intuitively, a confining unit may also be named after the aquifer system in which it resides, especially if that unit crosses multiple lithostratigraphic units precluding a lithostratigraphicbased name. The MFCU, which has been adopted by the CFHUD II accordingly follows this line of reasoning. Any proposed changes in Florida’s hydrostra tigraphic nomenclature will hopefully address the IAS/ICU, in which relative permeability is an important consideration. In the northern part of the study area, confining to semi-confining sediments are dominan t, whereas in the southern part of the study area, distinct local to sub-regional zones of higher pe rmeability exist. Some hydrogeologists prefer to characterize the northern area as ICU and the southern area as IAS; however, it is noteworthy that a system (IAS) and a unit (ICU) are not at the same hierarchical level (Aadland et al., 1995). As a result, the ICU would be a unit of the IAS. The concept of a confining system should also be considered for the IAS/ICU. Jorgenson et al. (1993) define a confining system as “two or more confining units separated at most locations by one or more aquifers that are not in the same hydraulic system.” Renken (1998) clarifies this definition by stating “confining units that may contain local aquifers, but which function together to retard the vertical movement of water, are called confining systems.” In consideration of these definitions, and Laney and Davidson’s (1986) suggestion on nomenclature (i.e ., avoid naming based on relative position), the IAS may be more appropriately named the Upper Floridan confining system , which would allow for presence of hydraulically disconnected permeable zones within a system that confines the FAS. In the study area, the northern lateral equivalent of this confining system could be named the Upper Floridan confining unit . Alternatively, the area could simply be recognized as part of the Upper Floridan confining system . Naming these systems or units relative to the FAS may be more appropriate than using a lithostratigraphic reference because the FAS, as well as its overlying confining/semi-confining sediments are not limited to a single lithostratigraphic formation or group. For example, to name the IAS/ICU based on association with the Hawthorn Group may lead to conf usion given that part of this lithostratigraphic package is included in the UFA.

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FLORIDA GEOLOGICAL SURVEY 100 Another option is to consider the IAS as a complex system of nearly statewide extent, recognizing that aquifers within this predominantly confining/semi-confining system are sub-regional to regional, yet the overall correlative hydrostratigraphic package is unique relative to the surficial and Floridan aquifer systems. Along this line of reasoning, one may consider the confining/semi-confining sediments in the northern part of the study area as a low-permeability hydrogeologic facies of the IAS. It is noteworthy that hydraulic characteristics of semi-confining zon es identified in Florida are considered “aquifers” or “permeable zones” in other parts of the country, thus lending support to the statewide IAS concept. Fetter (2001) describes an aquifer as a “geologic unit that can store and transmit water at rates fast enough to supply reasonable amounts to wells. The intrinsic permeability of aquifers would range from about 10-2 darcy upward.” Albeit subjective, clayey sands often considered part of semi-confining (and “confining?”) units in Florida fall within Fetter’s (2001) aquifer definition. The proposal of a statewide IAS, however, may l ead to perception issues fo r the lay public as well as concerns regarding aquifer-system de finitions. Many geoscientists contend that statewide use of the IAS name is inconsistent with existing aquifer-system de finitions. Moreover, use of the IAS name in the northern study area may incorrectly imply to the non-scientist that significant water-yielding “intermediate” strata exist in the region, which is not the case.

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BULLETIN NO. 68 101 APPENDIX 2. EXPLANATION OF RE VISIONS TO FDEP-FGS SPECIAL PUBLICATION 28 AQUIFER DEFINITIONS Changes to original Southeastern Geological Society (1986) text are denoted by brackets (additions) and strikethroughs to reflect definitions applied in this report. Footnotes provide explanation. surficial aquifer system : “ the permeable hydrogeologic unit contiguous with land surface that is comprised principally of unconsolidated to poorly indu rated [silici]clastic deposits. It also includes well indurated carbonate rocks [and sediments], other than those of the [FAS] Floridan aquifer system where the Floridan is at or near land surface. Rocks [and sediments] making up the [SAS] surficial aquifer system belong to all or part of the upper 7 Miocene to Holocene Series. [The SAS] It contains the water table and water within it is under main ly unconfined conditions; [however,] but beds of low permeability may cause semi-confined or locally conf ined conditions to prevail in its deeper parts. The lower limit of the [SAS] surficial aquifer system coincides with the top of laterally extensive and vertically persistent beds of much lower permeability.”8 intermediate aquifer system or the intermediate confining unit: “ – includes all rocks that lie between and collectively retard the exchange of water be tween the overlying [SAS] surficial aquifer system [(or land surface)]9 and the underlying [FAS] Floridan a quifer system . These rocks in general consist of [coarse to] fine grained [silici]clas tic deposits interlayered with car bonate strata belonging to all or parts of the [Oligocene] Miocene 10 and younger S [s]eries. [ Section omitted .11] The aquifers within this system contain water under [semi-confined to] confined conditi ons. The top of the intermediate aquifer system or the intermediate confining unit [IAS/ICU] coincides with the base of the [SAS] surficial aquifer system [and on a local scale with land surface]. The b ase of the [IAS/ICU] intermediate aquifer is at [is hydraulically separated to a significan t degree from] the top of the [FAS]12 vertically persistent permeable carbonate section that comprises the Floridan aquifer system, or, in other words, tha t place in the section where clastic layers of significant thickness and permeable carbonate rocks are dominant . [ Section omitted .13].” Floridan aquifer system: “ – [a] thick [predominantly] carbonate sequence [that] which includes all or part of the Paleocene to early [Lower] Miocene Series and functi ons regionally as a water-yielding hydraulic unit. Where overlain by [the IAS/ICU] either the intermediate aquifer system or the intermediate confining unit , the [FAS] Floridan contains water under confined conditions. When overlain directly by the [SAS] surficial aquifer system , the [FAS] may or may not contain water under confined conditions depending on the extent of low pe rmeability material [within the base of] in the [SAS] surficial aquifer system . Where the carbonate rocks crop out [or are covered by a veneer of siliciclastics], the [FAS] Floridan generally contains water unde r unconfined conditions near the top of the aquifer system, but because of vertical variations in permeability, deeper zones may contain water under confined conditions. The [FAS] Florida aquifer system is present throughout the State and is the deepest part of the active groundwater flow system on mainland Fl orida. The top of the [FAS] aquifer system generally 7 Although aquifer systems are based on hydraulic properties, correspondence with age does exist; “upper” is deleted to allow more flexibility with regard to this correlation. 8 Second paragraph describing SAS in Southeastern Geological Society (1986) is omitted. 9 For example, the Peace River Formation is loca lly exposed at land su rface in Polk County. 10 Now recognized as Late Oligocene based on the work of Scott et al. (1994). 11 Related nomenclatural issues pertaining to th e IAS/ICU are being addressed by the CFHUD II. 12 The lower extent of the IAS/ICU in the present study is also based on the relative degree of hydraulic separation from the FAS. 13 Related nomenclatural issues pertaining to th e IAS/ICU are being addressed by the CFHUD II.

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FLORIDA GEOLOGICAL SURVEY 102 coincides with the absence of signifi cant thicknesses of [silici]clastics from the section and with the top of the vertically persistent permeable carbonate section [ Section omitted.14].” 14 Remainder of the Southeastern Geological Society (1986) definition relevant to this study is discussed in other sections of this report.

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7464 7439 7435 7421 7405 7403 7360 7342 7339 7091 7032 6903 6864 6863 6685 6670 6590 6581 6556 6540 6510 6492 6392 6356 1801 51924 51925 51926 6294 6293 6278 6234 6232 6183 6159 6158 6133 6108 5984 5974 5956 5954 5940 5892 5881 5865 5863 5799 5760 5759 5694 5646 5608 5574 5486 5464 5435 5350 5282 5132 5122 5101 5069 5055 5054 4929 4894 4839 4802 4760 4750 4697 4689 4506 4505 4503 4410 4205 4190 4185 4047 636 8778 13609 13095 4044 3852 3839 3790 3772 3740 3711 3675 3634 3615 3556 3512 3469 3428 3310 3215 3214 3118 3113 3090 3086 3073 3067 3052 3009 2983 2979 2971 2927 2876 2859 2842 2779 2766 2688 2677 2607 2605 2569 2566 2539 2526 2493 2475 2441 51928 2397 2382 2367 2365 2359 2324 2237 2229 2179 2178 2163 2160 2152 2010 2007 1997 1936 1921 1893 1864 1845 1844 1809 1791 1773 1763 1760 1742 1741 1740 1739 1726 1710 1690 1669 1668 1645 1633 1632 1615 1564 1511 1476 1457 1448 1442 1406 1245 1244 1242 1241 1240 1236 1220 1211 1201 1200 1198 1112 1111 1095 1094 1007 51898 1003 1537 50162 51869 51918 18153 18154 51889 51888 51887 51885 51884 51883 51882 5188 1 51880 51879 51878 51877 51876 51875 51874 51873 51872 51871 51870 51868 51867 51866 51865 18535 51864 51863 51862 51861 51860 51859 51858 51857 51856 51855 51854 50174 18349 51891 51892 51896 51895 51897 50166 275 51914 5892 18109 51893 3851 10253 50173 50172 50171 50169 50168 50165 50164 50163 50149 50148 50147 50144 50143 50142 50137 50133 50131 50129 50126 50124 50123 50120 50117 50112 50108 50107 50105 50104 50103 50101 50100 50099 50098 50097 50096 50095 50094 50093 50092 50091 50090 50089 50088 50015 50003 50001 18117 18091 18057 18055 17919 17870 17824 1006 1399 1005 17579 16618 17820 17718 17692 17689 17620 17608 17597 17591 17566 17541 17514 17513 17512 17505 17488 17455 17452 17428 17415 17414 17392 17357 17142 17141 17140 17096 17092 17091 17090 17087 17084 17078 17072 17067 17063 17057 17056 17042 17035 17022 51890 17017 17000 16999 16977 16960 16956 16953 16944 16918 16917 16913 16889 16881 17467 16839 16838 16836 16814 16790 16789 16784 16783 16782 16751 16750 16743 16741 16740 16687 16663 16658 16646 16644 16636 16624 17555 16617 16611 16609 16580 16579 16578 16576 16574 16573 16539 16536 16523 16496 16495 16480 16479 16478 16477 16475 16471 16469 16468 16456 16394 16311 16310 16309 16308 16305 16304 16303 16281 16274 16268 16267 16260 16257 16242 16205 16198 16197 16189 16181 16134 16098 16070 16006 16004 16001 15993 15992 15972 15957 15938 15933 15925 15918 15916 15880 15866 15839 15831 15826 15812 15811 15802 15801 15799 15749 15691 15685 15684 15683 15682 15681 15650 15649 15648 15647 15644 15643 15642 15636 15625 15624 15623 15622 15620 15619 15618 15606 15595 15588 15587 51899 16740 51900 15586 15520 15519 15518 15517 15495 15494 15380 15379 15366 15347 15346 15345 15343 15342 15333 15332 15328 15321 15303 15296 15289 15286 15280 15261 15200 15188 15168 15166 15163 15125 15074 14905 14904 14902 14897 14896 14889 14885 14884 14883 14882 14881 14880 14878 14872 14871 14865 14864 14861 14813 14800 14787 14780 14757 11570 2732 18235 14751 14722 14717 14712 14675 14674 14673 14672 14671 14669 14668 14663 14654 14629 14593 14525 14519 14481 14427 14389 14386 14385 14383 14382 14381 14274 14263 14168 14121 14116 14095 14046 14032 13994 13988 13987 13944 13943 13924 13923 13898 13886 13872 13863 13855 13841 13838 13798 13781 13743 13727 13717 13696 13693 13637 13620 13525 51901 51903 1655 13524 13518 13517 13514 13510 13491 13469 13458 13455 13410 13374 13368 13337 13334 13333 13331 13304 13289 13287 13285 13269 13245 13238 13133 13107 13100 13099 13078 13073 18691 13065 13060 13056 13055 13054 13053 13052 13050 13049 13020 13019 13018 12985 12984 12967 12966 12965 12943 12907 12906 12878 12832 12831 12830 12794 12787 12783 12750 51902 12745 12743 12701 12698 12684 12640 12615 12495 12413 12378 12363 12362 12346 12327 12311 12270 12267 12245 12243 12242 12241 12238 12237 12235 12233 12194 12180 12098 12050 12007 11950 11946 11932 11908 11907 11867 11817 11761 51915 11711 11676 11669 11662 11653 11650 11648 11634 11588 11541 11531 11499 11491 11484 11471 11453 11447 11424 12948 51905 51911 11420 11415 11392 11369 11360 11323 11306 11246 11230 11220 11209 11156 10950 10901 10891 10829 10808 10771 10761 10760 10759 10756 10753 10752 10749 10740 10650 10647 10622 10620 10619 10577 10497 10494 10470 10469 10468 10409 10364 10360 10341 10331 10298 10296 10254 10221 10129 10122 10118 10114 10108 10101 10089 9159 9132 9091 4298 2972 2703 2364 9269 51886 50167 18116 17991 17073 17001 16835 16575 16494 16474 16472 16462 16022 15942 15939 15800 15616 15601 15594 15593 15585 15521 15204 15196 14917 14873 14847 14518 14336 14269 14137 14016 13939 13735 13610 13443 13061 13059 13048 12909 12828 12700 12699 12616 12583 12581 12528 12244 12236 12234 12983 12113 12003 11788 11563 11554 11222 11179 11154 10937 10841 10679 10617 10472 18324 10471 10411 10410 10406 10405 10321 10093 10092 51904 51894 51906 51907 51908 51909 51910 51917 15556 51916 51912 3368 S u w a n n e e R i v e r W a t e r M a n a g e m e n t D i s t r i c t South Florida Water Management District St. Johns River Water Management District 81W 81W 8130'W 8130'W 82W 82W 8230'W 8230'W 83W 83W 2930'N 2930'N 29N 29N 2830'N 2830'N 28N 28N 2730'N 2730'N 27N 27N 2630'N 2630'N Gulf of MexicoExplanation Wells Used Study Area Water Management Districts PLATE 2 Wells Used In This Study 010203040 5 Miles 010203040 5 KilometersScale: 1:1,000,000 Projection: Custom FDEP Albers

PAGE 119

81W 81W 81'W 8130'W 82W 82W 8230'W 8230'W 83W 83W 290'N 290'N 29N 29N 280'N 280'N 28N 28N 270'N 270'N 27N 27N 260'N 260'N Explanation Closed Topographic Depressions Water Management Districts Gulf of MexicoPLATE 3 Closed Topographic Depressions 010203040Kilometers 010203040MilesProjection: Custom FDEP Albers Scale: 1:1,000,000

PAGE 154

7 0 0 6 0 0 5 0 0 4 0 0 8 00 90 0 1 0 0 300 2 0 0 1 0 0 0 0 1 1 0 0 1 2 0 0 1 30 0 1 4 0 0 150 0 1 10 0 3 0 0 0 1 0 0 0 0 10 0 1 0 0 1 0 0 1 0 0 1 0 0 0 1 0 0 1 0 0 0 0 81W 81W 8130'W 8130'W 82W 82W 8230'W 8230'W 83W 83W 2930'N 2930'N 29N 29N 2830'N 2830'N 28N 28N 2730'N 2730'N 27N 27N 2630'N 2630'N Explanation Study Area Wells Used Contours Water Management DistrictsAvon Park Fm. Surface (ft. MSL) >0 750 <-1500Gulf of Mexico PLATE 38 Avon Park Formation SurfaceContour Interval: 100 ft Projection: Custom FDEP Albers Scale: 1:1,000,000 010203040 5 Miles 010203040 5 Kilometers

PAGE 155

7 5 3 7 5 4 5 0 15 0 8 2 5 9 0 0 9 7 5 1 0 5 0 7 5 -6 7 5 11 25 1 2 0 0 -7 5 0 1275 3 0 0 2 2 5 5 2 5 6 0 0 0 0 0 75 0 6 0 0 -1 1 2 5 6 7 5 7 5 7 5 0 22 5 7 5 5 2 5 6 0 0 0 1050 -75 3 0 0 0 0 81W 81W 8130'W 8130'W 82W 82W 8230'W 8230'W 83W 83W 2930'N 2930'N 29N 29N 2830'N 2830'N 28N 28N 2730'N 2730'N 27N 27N 2630'N 2630'N Explanation Study Area Wells Used Contours Ocala LS Not Present Ocala LS Locally Absent Water Management DistrictsOcala Ls. Surface (ft. MSL) > 75 -600 <-1275Gulf of MexicoPLATE 39 Ocala Limestone SurfaceContour Interval: 75 ft Projection: Custom FDEP Albers Scale: 1:1,000,000 010203040 5 Miles 010203040 5 Kilometers

PAGE 156

3 0 0 2 5 0 2 0 0 1 5 0 2 50 1 0 0 5 0 3 0 0 3 5 0 4 00 4 5 0 20 0 3 5 0 2 5 0 2 5 0 1 0 0 2 0 0 2 0 0 1 5 0 3 0 0 1 0 0 2 0 0 2 0 0 3 0 0 5 0 2 0 0 20 0 2 0 0 3 0 0 3 0 0 1 0 0 1 5 0 5 0 2 5 0 2 5 0 4 0 0 3 0 0 1 5 0 5 0 100 5 0 1 0 0 2 0 0 1 0 0 3 00 3 5 0 81W 81W 8130'W 8130'W 82W 82W 8230'W 82'W 83W 83W 2930'N 2930'N 29N 29N 2830'N 2830'N 28N 28N 2730'N 2730'N 27N 27N 2630'N 2630'N Explanation Study Area Wells Used Contours Ocala LS Not Present Ocala LS Locally Absent Water Management DistrictsOcala Ls. Thickness (ft.) >450 225 >0Gulf of MexicoPLATE 40 Ocala Limestone ThicknessContour Interval: 50 ft Projection: Custom FDEP Albers Scale: 1:1,000,000 010203040 5 Miles 010203040 5 Kilometers

PAGE 157

0 75 -2 2 5 3 7 5 3 0 0 15 0 600 4 5 0 5 2 5 6 7 5 7 5 7 5 0 8 2 5 4 5 0 75 3 0 0 1 5 0 0 1 5 0 7 5 7 5 0 3 7 5 -5 2 5 6 7 5 6 7 5 3 7 5 7 5 3 7 5 7 5 6 7 5 45 0 4 50 0 3 7 5 6 7 5 81W 81W 8130'W 8130'W 82W 82W 8230'W 8230'W 83W 83W 2930'N 2930'N 29N 29N 2830'N 2830'N 28N 28N 2730'N 2730'N 27N 27N 2630'N 2630'N Gulf of MexicoPLATE 41 Suwannee Limestone SurfaceContour Interval: 75 ft Projection: Custom FDEP Albers Scale: 1:1,000,000 010203040 5 Miles 01020304050 5 Kilometers ? ?Explanation Study Area Contours Wells Used Suwannee LS Extents Approx. Suwannee LS Extents Possible Faults Water Management DistrictsSuwannee Ls. Surface (ft. MSL) > 75 -375 <-825 ?

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1 0 0 1 5 0 2 0 0 2 5 0 3 0 0 5 0 3 50 4 0 0 4 5 0 2 5 0 2 0 0 4 0 0 2 0 0 3 0 0 50 2 0 0 3 5 0 3 0 0 2 0 0 2 5 0 3 0 0 30 0 1 5 0 300 5 0 3 5 0 1 0 0 50 3 5 0 3 0 0 4 0 0 1 0 0 1 00 2 5 0 2 00 4 5 0 1 0 0 5 0 1 0 0 1 5 0 300 2 50 81W 81W 8130'W 8130'W 82W 82W 8230'W 8230'W 83W 83W 2930'N 2930'N 29N 29N 2830'N 2830'N 28N 28N 2730'N 2730'N 27N 27N 2630'N 2630'N ? ?Gulf of MexicoPLATE 42 Suwannee Limestone ThicknessContour Interval: 50 ft Projection: Custom FDEP Albers Scale: 1:1,000,000 010203040 5 Miles 010203040 5 Kilometers Explanation Study Area Contours Wells Used Suwannee LS Extents Approx. Suwannee LS Extents Possible Faults Water Management DistrictsSuwannee Ls. Thickness (ft.) >450 225 >0 ?

PAGE 159

1 2 5 7 5 1 5 0 2 5 0 1 0 0 1 7 5 1 0 0 5 0 2 5 1 2 5 2 0 0 2 5 5 0 7 5 2 5 25 5 0 12 5 2 5 -1 7 5 1 0 0 1 0 0 1 2 5 -7 5 1 0 0 1 0 0 1 2 5 1 0 0 0 7 5 1 0 0 1 0 0 -25 5 0 -1 2 5 2 5 1 0 0 1 2 5 2 5 5 0 1 2 5 7 5 2 5 2 5 75 7 5 1 2 5 5 0 7 5 5 0 7 5 7 5 25 100 7 5 5 0 7 5 7 5 7 5 75 -5 0 0 0 5 0 1 7 5 7 5 7 5 5 0 1 0 0 100 75 5 0 7 5 1 0 0 25 5 0 2 5 81W 81W 8130'W 8130'W 82W 82W 8230'W 8230'W 83W 83W 2930'N 2930'N 29N 29N 2830'N 2830'N 28N 28N 2730'N 2730'N 27N 27N 2630'N 2630'N Gulf of MexicoPLATE 43Explanation Study Area Wells Used Contours Hawthorn Group Extents Water Management DistrictsHawthorn Group Surface (ft. MSL) > 125 35 <-200Hawthorn Group Locally Present (undifferentiated; possibly reworked) Hawthorn Group SurfaceScale 1:1,000,000 Projection: Custom FDEP Albers Contour Interval: 25 ft 010203040 5 Miles 010203040 5 Kilometers

PAGE 160

7 5 37 5 4 50 3 0 0 82 5 1 50 6 7 5 6 0 0 2 2 5 5 2 5 75 0 7 5 75 7 5 3 75 3 7 5 2 25 1 5 0 6 7 5 3 0 0 4 5 0 4 5 0 7 5 5 2 5 30 0 6 0 0 3 7 5 7 5 4 5 0 1 5 0 5 2 5 4 5 0 6 0 0 6 0 0 7 5 4 50 7 5 6 0 0 3 7 5 6 7 5 2 2 5 6 0 0 4 5 0 81W 81W 8130'W 8130'W 82W 82W 8230'W 8230'W 83W 83W 290'N 290'N 29N 29N 280'N 280'N 28N 28N 270'N 270'N 27N 27N 260'N 260'N Gulf of MexicoPLATE 44 Explanation Study Area Wells Used Contours Hawthorn Group Extents Water Management DistrictsHawthorn Group Thickness (ft.) >825 415 >0Hawthorn Group Locally Present (undifferentiated; possibly reworked) Hawthorn Group Thickness 010203040 5 Miles 010203040 5 Kilometers Scale 1:1,000,000 Projection: Custom FDEP Albers Contour Interval: 75 ft

PAGE 161

-180 6 0 2 1 0 9 0 2 4 0 0 9 0 3 0 6 0 2 7 0 1 5 0 30 1 2 0 1 2 0 9 0 12 0 3 0 0 1 2 0 9 0 6 0 6 0 6 0 18 0 6 0 3 0 6 0 6 0 15 0 9 0 1 2 0 9 0 90 -1 5 0 9 0 3 0 1 8 0 21 0 1 5 0 120 81W 81W 8130'W 8130'W 82W 82W 8230'W 8230'W 83W 83W 2930'N 2930'N 29N 29N 2830'N 2830'N 28N 28N 2730'N 2730'N 27N 27N 2630'N 2630'N Gulf of Mexico PLATE 45 Explanation Study Area Wells Used Contours Arcadia Fm. Extents Water Management DistrictsArcadia Fm. Surface (ft. MSL) > 90 -90 <-270 Arcadia Formation SurfaceContour Interval: 30 ft Projection: Custom FDEP Albers Scale: 1:1,000,000 010203040 5 Miles 010203040 5 Kilometers

PAGE 162

2 2 5 6 0 0 6 75 4 5 0 5 2 5 6 0 0 15 0 7 5 7 5 7 5 3 7 5 37 5 7 5 225 3 0 0 1 5 0 375 4 5 0 5 2 5 6 0 0 6 7 5 3 0 0 3 0 0 2 2 5 7 5 6 7 5 3 7 5 4 5 0 7 5 1 5 0 6 0 0 3 0 0 7 5 4 5 0 2 2 5 3 0 0 2 2 5 600 7 5 81W 81W 8130'W 8130'W 82W 82W 8230'W 8230'W 83W 83W 2930'N 2930'N 29N 29N 2830'N 2830'N 28N 28N 2730'N 2730'N 27N 27N 2630'N 2630'N Explanation Study Area Wells Used Contours Arcadia Fm. Extents Water Management DistrictsArcadia Fm. Thickness (ft.) >750 375 >0Gulf of MexicoPLATE 46 Arcadia Formation ThicknessContour Interval: 25 ft Projection: Custom FDEP Albers Scale: 1:1,000,000 010203040 5 Miles 010203040 5 Kilometers

PAGE 163

Ch a n g eF a c ie sC h a ng eF a c i e sFac ie sCh a n g e 3 7 5 4 5 0 3 0 0 0 5 2 5 2 2 5 1 5 0 -75 6 00 30 0 2 2 5 3 0 0 2 2 5 2 2 5 81W 81W 8130'W 8130'W 82W 82W 8230'W 8230'W 83W 83W 2930'N 2930'N 29N 29N 2830'N 2830'N 28N 28N 2730'N 2730'N 27N 27N 2630'N 2630'N Explanation Study Area Wells Used Contours Nocatee Mbr. Extents Nocatee Mbr. Extents Water Management DistrictsNocatee Mbr. Surface (ft. MSL) > 0 -300 <-600Gulf of MexicoPLATE 47 Nocatee Member of the Arcadia Formation SurfaceContour interval: 75 ft Projection: Custom FDEP Albers Scale: 1:1,000,000 010203040 5 Miles 010203040 5 Kilometers

PAGE 164

5 0 1 0 0 1 5 0 2 0 0 5 0 1 0 0 81W 81W 8130'W 8130'W 82W 82W 8230'W 8230'W 83W 83W 2930'N 2930'N 29N 29N 2830'N 2830'N 28N 28N 2730'N 2730'N 27N 27N 2630'N 2630'N F ac i e sC h a n g eF a c ie sC ha n g eF a c i e sC h a n g eExplanation Study Area Wells Used Contours Nocatee Mbr. Extents Nocatee Mbr. Extents Water Management DistrictsNocatee Mbr. Thickness (ft.) > 200 100 > 0 Gulf of MexicoPLATE 48 Nocatee Member of the Arcadia Formation ThicknessContour Interval: 50 ft Projection: Custom FDEP Albers Scale: 1:1,000,000 010203040 5 Kilometers 010203040 5 Miles

PAGE 165

0 5 0 -1 0 0 1 5 0 2 0 0 5 0 -2 5 0 3 0 0 -3 50 1 0 0 2 5 0 1 5 0 50 2 5 0 5 0 2 0 0 2 0 0 3 00 50 3 0 0 -2 5 0 50 0 0 2 0 0 81W 81W 8130'W 8130'W 82W 82W 8230'W 8230'W 83W 83W 2930'N 2930'N 29N 29N 2830'N 2830'N 28N 28N 2730'N 2730'N 27N 27N 2630'N 2630'N F a ci e sC h a n g eF a c i e sC h a n g eF ac i e sC h an g eExplanation Study Area Wells Used Contours Tampa Mbr. Extents Tampa Mbr. Extents Water Management DistrictsTampa Mbr. Surface (ft. MSL) > 100 -225 <-350Gulf of MexicoPLATE 49 Tampa Member of the Arcadia Formation SurfaceContour Interval: 50 ft Projection: Custom FDEP Albers Scale: 1:1,000,000 010203040 5 Kilometers 010203040 5 Miles

PAGE 166

50 10 0 1 5 0 1 5 0 5 0 100 5 0 1 5 0 81W 81W 8130'W 8130'W 82W 82W 8230'W 8230'W 83W 83W 290'N 290'N 29N 29N 280'N 280'N 28N 28N 270'N 270'N 27N 27N 260'N 260'N F a c i e sCha n geF a c i esCh a n g eC h a ng eF a c ie sExplanation Study Area Wells Used Contours Tampa Mbr. Extents Tampa Mbr. Extents Water Management DistrictsTampa Mbr. Thickness (ft.) >150 75 > 0Gulf of MexicoPLATE 50 Tampa Member of the Arcadia Formation ThicknessContour Interval: 50 ft Projection: Custom FDEP Albers Scale: 1:1,000,000 010203040 5 Kilometers 010203040 5 Miles

PAGE 167

20 0 5 0 5 0 0 1 5 0 -1 0 0 1 25 1 0 0 1 7 5 75 2 5 7 5 1 2 5 2 5 1 2 5 1 0 0 1 2 5 1 7 5 2 5 -5 0 50 2 5 0 2 5 1 2 5 7 5 -1 0 0 7 5 0 75 1 2 5 5 0 0 0 1 7 5 0 7 5 0 5 0 7 5 1 0 0 1 0 0 5 0 1 0 0 -7 5 2 5 -150 -2 5 81W 81W 8130'W 8130'W 82W 82W 8230'W 8230'W 83W 83W 2930'N 2930'N 29N 29N 2830'N 2830'N 28N 28N 2730'N 2730'N 27N 27N 2630'N 2630'N F a ci e sC h a n g eF a c ie sC h a n g eExplanation Study Area Wells Used Contours Peace River Fm. Extents Water Management DistrictsPeace River Fm. Surface (ft. MSL) >125 -35 <-200Gulf of MexicoPLATE 51 Peace River Formation SurfaceProjection: Custom FDEP Albers Contour Interval: 25 ft Scale: 1:1,000,000 010203040 5 Miles 010203040 5 Kilometers

PAGE 168

6 0 9 0 3 0 1 2 0 12 0 3 0 9 0 1 20 6 0 3 0 9 0 9 0 3 0 3 0 6 0 90 3 0 12 0 81W 81W 8130'W 8130'W 82W 82W 8230'W 8230'W 83W 83W 290'N 290'N 29N 29N 280'N 280'N 28N 28N 270'N 270'N 27N 27N 260'N 260'N C h a n g eF a c i e sF a c i e sC h a n g eGulf of Mexico PLATE 52Explanation Study Area Wells Used Contours Peace River Fm. Extents Water Management DistrictsPeace River Fm. Thickness (ft.) >120 60 >0 Peace River Formation ThicknessProjection: Custom FDEP Albers Contour Interval: 30 ft Scale: 1:1,000,000 010203040 5 Miles 010203040 5 Kilometers

PAGE 169

1 2 0 0 9 0 3 0 6 0 9 0 30 9 0 9 0 3 0 6 0 81W 81W 8130'W 8130'W 82W 82W 8230'W 8230'W 83W 83W 290'N 290'N 29N 29N 280'N 280'N 28N 28N 270'N 270'N 27N 27N 260'N 260'N F ac i e s C ha n g e F a c i e s C h a ng eFac ies Ch an g eF a c i e s C h a n g e Explanation Study Area Wells Used Contours Bone Valley Mbr. Extents Water Management DistrictsBone Valley Mbr. Surface (ft. MSL) >120 60 <0Gulf of MexicoPLATE 53 Bone Valley Member of the Peace River Formation SurfaceContour Interval: 30 ft Projection: Custom FDEP Albers Scale: 1:1,000,000 010203040 5 Miles 010203040 5 Kilometers

PAGE 170

2 0 4 0 81W 81W 8130'W 8130'W 82W 82W 8230'W 8230'W 83W 83W 290'N 290'N 29N 29N 280'N 280'N 28N 28N 270'N 270'N 27N 27N 260'N 260'N F ac i e s C h ang e F a c i e s C h an geFa c ie s Ch a n g eF a c i e s C h a n g e Explanation Study Area Wells Used Contours Bone Valley Mbr. Extents Water Management DistrictsBone Valley Mbr. Thickness (ft.) >40 20 >0Gulf of MexicoPLATE 54 Bone Valley Member of the Peace River Formation ThicknessContour Interval: 20 ft Projection: Custom FDEP Albers Scale: 1:1,000,000 010203040 5 Miles 010203040 5 Kilometers

PAGE 171

1 0 0 2 5 5 0 3 0 0 5 0 7 5 1 0 0 7 5 10 0 10 0 5 0 1 7 5 1 5 0 7 5 2 5 2 5 0 5 0 2 2 5 2 0 0 2 7 5 5 0 1 2 5 5 0 7 5 5 0 2 5 2 5 2 5 1 00 7 5 5 0 2 5 5 0 2 5 2 5 2 5 1 2 5 25 22 5 5 0 5 0 5 0 25 50 25 7 5 2 5 7 5 5 0 5 0 5 0 2 5 20 0 81W 81W 8130'W 8130'W 82W 82W 8230'W 8230'W 83W 83W 2930'N 2930'N 29N 29N 2830'N 2830'N 28N 28N 2730'N 2730'N 27N 27N 2630'N 2630'N Gulf of MexicoExplanation Study Area Wells Used Contours Discontinuous Basal Confinement of SAS Water Management DistrictsSAS Thickness (ft.) >275 140 >0PLATE 55 SURFICIAL AQUIFER SYSTEM THICKNESSContour Interval: 25 ft Projection: Custom FDEP Albers Scale: 1:1,000,000 010203040 5 Miles 010203040 5 Kilometers

PAGE 173

3 7 5 1 50 7 5 0 7 5 8 2 5 3 0 0 4 5 0 5 2 5 6 0 0 2 2 5 9 0 0 6 7 5 3 7 5 4 5 0 3 0 0 1 5 0 67 5 4 5 0 3 0 0 7 5 60 0 6 7 5 2 2 5 3 0 0 60 0 4 5 0 7 5 5 2 5 5 2 5 7 5 81W 81W 8130'W 8130'W 82W 82W 8230'W 8230'W 83W 83W 2930'N 2930'N 29N 29N 2830'N 2830'N 28N 28N 2730'N 2730'N 27N 27N 2630'N 2630'N * Denotes approximate areas where semi-confinement is laterally more discontinuous than continuous. Non-hachured areas reflect variable degrees of confinement that are more laterally continuous.Gulf of MexicoPLATE 57 Explanation Study Area Wells Used Contours Discontinuous* d d d d Questionable Extent Water Management DistrictsIAS / ICU Thickness (ft.) >900 450 >0Approximate northern limit of IAS permeable zones ? ? ? INTERMEDIATE AQUIFER SYSTEM / INTERMEDIATE CONFINING UNIT THICKNESS 010203040 5 Miles 010203040 5 Kilometers Contour Interval: 75 ft Projection: Custom FDEP Albers Scale: 1:1,000,000

PAGE 174

0 7 5 3 0 0 1 5 0 -2 2 5 4 5 0 3 7 5 5 2 5 6 0 0 6 7 5 7 5 -7 5 0 8 2 5 -4 5 0 0 7 5 7 5 7 5 7 5 -2 2 5 4 5 0 0 0 -7 5 -4 5 0 75 7 5 0 6 7 5 0 7 5 7 5 0 0 6 75 7 5 6 7 5 7 5 0 0 81W 81W 8130'W 8130'W 82W 82W 8230'W 8230'W 83W 83W 2930'N 2930'N 29N 29N 2830'N 2830'N 28N 28N 2730'N 2730'N 27N 27N 2630'N 2630'N Gulf of MexicoExplanation Study Area Wells Used Contours Water Management DistrictsFAS Surface (ft. MSL) > 75 -375 <-825PLATE 58 FLORIDAN AQUIFER SYSTEM SURFACEProjection: Custom FDEP Albers Contour Interval: 75 ft Scale: 1:1,000,000 010203040 5 Miles 010203040 5 Kilometers

PAGE 175

!5 !5 !5 !5 !5 !5 !5 !5 1 5 0 0 8 7 5 7 5 0 1 1 2 5 6 2 5 1 0 0 0 1 5 0 0 -1 3 7 5 175 0 125 0 1 6 2 5 -1 8 7 5 5 0 0 2 0 0 0 3 7 5 2125 5 0 0 -2 1 2 5 -8 7 5 7 5 0 5 0 0 -8 7 5 6 2 5 2 1 2 5 21 2 5 -1691 -1413 -1450 -1686 -1577 -1524 -1635 -1678 81W 81W 8130'W 8130'W 82W 82W 8230'W 8230'W 83W 83W 2930'N 2930'N 29N 29N 2830'N 2830'N 28N 28N 2730'N 2730'N 27N 27N 2630'N 2630'N Water Quality Data Indicates Possible MFCUGulf of MexicoPLATE 59 MFCU Possibly Absent: Limited Data A A' Wells Containing Unit II (Miller, 1986) Overlying Mapped Horizon; Elevation in Feet MSLExplanation Study Area Wells Used !5 Contours Possible Limit of MFCU Water Management Districts A A' Cross Section Location for Figure 39MFCU Surface (ft. MSL) > -450 -1275 < -2100 MIDDLE FLORIDAN CONFINING UNIT SURFACEContour Interval: 125 ft Projection: Custom FDEP Albers 010203040 5 Miles 010203040 5 KilometersScale: 1:1,000,000