<%BANNER%>
HIDE
 Front Cover
 Frontispiece
 Title Page
 Letter of transmittal
 Table of Contents
 Dedication
 Acknowledgement
 List of participants and contr...
 Contributions of Durward H. Boggess...
 The surficial geology of Lee county...
 Late neogene geology of northwestern...
 Sequence stratigraphy of a south...
 Late paleogene and neogene chronostratigraphy...
 The hydrogeology of Lee County,...
 Water level elevation maps of the...
 Hydrogeologic implications of Uranium-rich...
 Hydrogeology of the lower Floridian...
 Caloosahatchee basin integrated...
 Surface water management in Lee...
 Seagrass meadow hourly dissolved-oxygen...
 The Lee County abandoned well...
 Back Cover


FGS FEOL



Geology and Hydrogeology of Lee County, Florida
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 Material Information
Title: Geology and Hydrogeology of Lee County, Florida
Physical Description: Archival
Language: English
Creator: Missimer, Thomas M. ( Editor )
Scott, Thomas M. ( Editor )
Publisher: Florida Geological Survey
Place of Publication: Tallahassee, FL
Publication Date: 2001
 Notes
General Note: Presented at the Durward H. Boggess Memorial Symposium
General Note: Florida Geological Society special publication 49
 Record Information
Source Institution: University of Florida
Holding Location: University of Florida
Rights Management:
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.
System ID: UF00099169:00001

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Table of Contents
    Front Cover
        Front Cover
    Frontispiece
        Frontispiece
    Title Page
        Page i
        Page ii
    Letter of transmittal
        Page iii
        Page iv
    Table of Contents
        Page v
    Dedication
        Page vi
    Acknowledgement
        Page vii
    List of participants and contributors
        Page viii
        Page ix
    Contributions of Durward H. Boggess to the hydrology and geology of Lee County, Florida
        Page 1
        Page 2
        Page 3
        Page 4
        Page 5
        Page 6
        Page 7
        Page 8
        Page 9
        Page 10
        Page 11
        Page 12
        Page 13
        Page 14
        Page 15
        Page 16
    The surficial geology of Lee county and the Caloosahatchee basin
        Page 17
        Page 18
        Page 19
        Page 20
    Late neogene geology of northwestern Lee County, Florida
        Page 21
        Page 22
        Page 23
        Page 24
        Page 25
        Page 26
        Page 27
        Page 28
        Page 29
        Page 30
        Page 31
        Page 32
        Page 33
        Page 34
    Sequence stratigraphy of a south Florida carbonate ramp and bounding siliciclastics
        Page 35
        Page 36
        Page 37
        Page 38
        Page 39
        Page 40
        Page 41
        Page 42
        Page 43
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        Page 45
        Page 46
        Page 47
        Page 48
        Page 49
        Page 50
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        Page 60
        Page 61
        Page 62
        Page 63
        Page 64
        Page 65
        Page 66
    Late paleogene and neogene chronostratigraphy of Lee County, Florida
        Page 67
        Page 68
        Page 69
        Page 70
        Page 71
        Page 72
        Page 73
        Page 74
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        Page 84
        Page 85
        Page 86
        Page 87
        Page 88
        Page 89
        Page 90
    The hydrogeology of Lee County, Florida
        Page 91
        Page 92
        Page 93
        Page 94
        Page 95
        Page 96
        Page 97
        Page 98
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        Page 131
        Page 132
        Page 133
        Page 134
        Page 135
        Page 136
        Page 137
        Page 138
    Water level elevation maps of the primary aquifers in the lower west coast of Florida
        Page 139
        Page 140
        Page 141
        Page 142
        Page 143
        Page 144
        Page 145
        Page 146
        Page 147
        Page 148
        Page 149
        Page 150
    Hydrogeologic implications of Uranium-rich phophate in northeastern Lee County
        Page 151
        Page 152
        Page 153
        Page 154
        Page 155
        Page 156
        Page 157
        Page 158
        Page 159
        Page 160
        Page 161
        Page 162
        Page 163
        Page 164
        Page 165
        Page 166
    Hydrogeology of the lower Floridian aquifer "boulder zone" of southwest Florida
        Page 167
        Page 168
        Page 169
        Page 170
        Page 171
        Page 172
        Page 173
        Page 174
        Page 175
        Page 176
        Page 177
        Page 178
        Page 179
        Page 180
        Page 181
        Page 182
    Caloosahatchee basin integrated surface-groundwater model
        Page 183
        Page 184
        Page 185
        Page 186
        Page 187
        Page 188
        Page 189
        Page 190
        Page 191
        Page 192
        Page 193
        Page 194
        Page 195
        Page 196
    Surface water management in Lee County
        Page 197
        Page 198
        Page 199
        Page 200
        Page 201
        Page 202
        Page 203
        Page 204
    Seagrass meadow hourly dissolved-oxygen recordings
        Page 205
        Page 206
        Page 207
        Page 208
        Page 209
        Page 210
        Page 211
        Page 212
        Page 213
        Page 214
        Page 215
        Page 216
        Page 217
        Page 218
        Page 219
        Page 220
        Page 221
        Page 222
        Page 223
        Page 224
        Page 225
        Page 226
    The Lee County abandoned well program
        Page 227
        Page 228
        Page 229
        Page 230
    Back Cover
        Page 231
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STATE OF FLORIDA
DEPARTMENT OF ENVIRONMENTAL PROTECTION
David B. Struhs, Secretary




DIVISION OF RESOURCE ASSESSMENT AND MANAGEMENT
Edwin J. Conklin, Director




FLORIDA GEOLOGICAL SURVEY
Walter Schmidt, State Geologist and Chief










SPECIAL PUBLICATION NO. 49


GEOLOGY AND HYDROLOGY OF LEE COUNTY, FLORIDA
DURWARD H. BOGGESS MEMORIAL SYMPOSIUM


EDITED BY
Thomas M. Missimer and Thomas M. Scott











Published for the
FLORIDA GEOLOGICAL SURVEY
Tallahassee
2001













LETTER OF TRANSMITTAL


FLORIDA GEOLOGICAL SURVEY
Tallahassee
2001



Governor Jeb Bush
Tallahassee, Florida

Dear Governor Bush:

The Florida Geological Survey, Division of Resource Assessment and Management, Department
of Environmental Protection, is publishing as Special Publication No. 49, Geology and
Hydrogeology of Lee County, Florida, Durward H. Boggess Memorial Symposium, edited by
Thomas M. Missimer and Thomas M. Scott. The information presented herein is valuable in
understanding the geology of the aquifers underlying this growing region. It will be useful to state
planners and land managers who must make informed decisions about local aquifer uses and
resources.


Respectfully,




Walter Schmidt, Ph.D.
State Geologist and Chief
Florida Geological Survey




















































Printed for the
Florida Geological Survey

Tallahassee
2001

ISSN 0085-0640


iv









CONTENTS


Dedication and Editor's Preface ........................................ ...... vi
A cknow ledgem ents ........................................................ vii
List of Participants and Contributors .................................... ...... viii

Contributions of Durward H. Boggess to the hydrology and geology of Lee County, Florida
by Thom as M M issim er . ......... ........................................... 1

GEOLOGY

The Surficial Geology of Lee County and the Caloosahatchee Basin, by Thomas M. Scott and
T hom as M M issim er ...................................................... 17

Late Neogene Geology of Northwestern Lee county, Florida, by Thomas M. Missimer ..... 21

Sequence Stratigraphy of a Carbonate Ramp and Bounding Silicielasties (late Miocene -
Pliocene), Southern Florida, by Kevin J. Cunningham, David Burky, Tokiyuki Sato, John A.
Barron, Laura A. Guertin, and Ronald S. Reese ................................... 35

Late Paleogene and Neogene Chronostratigraphy of Lee County, Florida,
by Thomas M. Missimer . ......... .......................................... 67

HYDROGEOLOGY

Hydrogeology of Lee County, Florida, by Thomas M. Missimer and W. Kirk Martin ........ 91

Water Level Maps of the Primary Aquifers in the Lower West Coast of Florida
by Terry Bengtsson and Hope Radin .................................. . ...... 139

Hydrogeologic Implications of Uranium-rich Phosphate in Northeastern Lee County
by J. Michael W einberg and James B. Cowant .................................. 151

Hydrogeology of the Lower Floridian Aquifer "Boulder Zone" of Southwest Florida
by Robert G. Maliva, Charles W Walker, and Edward X. Callahan .............. . . 167

HYDROLOGY AND WATER QUALITY

Caloosahatchee Basin integrated surface water groundwater model
by Clyde Dabbs, Torten Jacobsen, Douglas Moulton, and Akin Owosina .......... .... .183

Surface Water Management in Lee County, by Archie T Grant and Andrew D. Tilton .... 197

Seagrass meadow hourly dissolved oxygen recordings, central Estero Bay, Lee County
by Hugh J. Mitchell-Tapping, Thomas J. Lee, Cathy R. Williams, and Thomas Winter ... .205

The Lee County Abandoned Well Program, by Jack McCoy .................. . . 227











DEDICATION AND EDITOR'S PREFACE


A special symposium on the geology and hydrology of Lee County, Florida was held in Fort
Myers on November 18 and 19, 1999. This symposium was held as part of the 9th Southwest
Florida Water Resources Conference. The conference was held in honor of Durward H.
Boggess, who made significant contributions to the understanding of the geology and hydrology
of Lee County.

Durward H. Boggess was a hydrologist with the U.S. Geological Survey in Fort Myers from
1966 to 1979. During this time period, Lee County was one of the most rapidly growing regions
in the United States. Little was known about the geology and the aquifer system beneath the
county, as evidenced by the small number of publications on this region by the Florida Geological
Survey. Durward H. Boggess developed a geologic and hydrologic database that allowed the
development of future water supplies to occur with a sound scientific basis.

Most of the papers published in this volume were presented at the conference and a few
others were added to make the volume as complete as possible in terms of recent knowledge
on the geology and hydrology of Lee County. The volume is organized with a discussion of the
contributions of Durward Boggess, followed by a series of papers on the geology of the county.
Based on the geologic framework, a series of papers follows on the hydrogeology of the county.
Finally, some papers on the surface-water hydrology and water quality of the county complete
the volume.

Lee County occurs in the geographic middle of the southern part of the Florida Platform.
The geology of this region is rather unique, because there is a succession of carbonate
sediments followed by a complex mix of carbonate and siliciclastic sediments (beginning in the
Oligocene). The geographic location of the county and the mixing of the sediments caused the
aquifer system beneath the county to be quite complex with numerous different aquifers present.
Over 12 aquifers or major water-bearing zones occur beneath any given area of the county. It
is critical to understand the geology and hydrology of this area, because many of the aquifer are
or will be used for water supply. Also, the deep aquifer system is used for the disposal of liquid
wastes, such as oil field brines, concentrates from desalination plants, and treated domestic
wastewater.

It is extremely important that recent information on the geology and hydrology of this as well
as other regions of Florida be made available to environmental managers and the general pub-
lic in a timely manner.


Thomas M. Missimer Thomas M. Scott
Fort Myers Tallahassee











ACKNOWLEDGEMENTS


The editors wish to acknowledge a number of individuals whose efforts made this sym-
posium and the resulting special publication possible. Perhaps the most difficult task, aside from
finding the time to prepare a paper, is the meeting planning and organization. This task fell on
the conference host committee, whose efforts are greatly appreciated: Ron Edenfield (Chair),
Susan Brookman, John Capece, Clyde Dabbs, Win Everham, Samy Faried, Lynne Felknor,
Jennifer Flaitz, Ron Hamel, Kurt Harclerode, Steve Kempton, Bonnie Kranzer, Jeff Krieger, Tom
Missimer, John Musser, Dan VanNorman, and Sean Weeks.
The editors extend a special thanks to Mrs. Durward Boggess for providing the photo of
her husband used inside the front cover of the publication. And we thank Frank Rupert for com-
piling the different text and graphics formats into QuarkXPress for publication.











LIST OF PARTICIPANTS AND CONTRIBUTORS


John Barron, U.S. Geological Survey, 345 Middlefield rd., Menlo Park, CA 94025
Terry Bengtsson, SFWMD, 2301 McGregor Blvd, Fort Myers, FL 33901
David Bukrey, U.S. Geological Survey, 345 Middlefield rd., Menlo Park, CA 94025
Edward Callahan, Florida Geophysical Logging, Inc., 15465 Pine Ridge Rd., Fort Myers, FL
33908
James Cowart, Department of Geological Sciences, Florida State University, Tallahassee, FL
32306
Kevin Cunningham, U.S. Geological Survey, 9100 NW 36th Street, Suite 107, Miami, FL
33178
Clyde Dabbs, SFWMD, 2301 McGregor Blvd, Fort Myers, FL 33901
Archie Grant, Johnson Engineering, Inc.P.O. Box 1550, Fort Myers. FL 33902
Laura Guertin, Mary Washington College, Fredericksburg, VA 22401
Torsten Jacobsen, DHI Inc., Eight Neshaminy Interplex, Suite 219, Trevose, PA 19053
Thomas Lee, Ostego Bay Foundation Inc./Estero Bay Marine Laboratory Inc., P.O.
Box 0875, Fort Myers Beach, FL 33931
Robert Maliva, CDM/Missimer International, Inc., 8140 College Parkway, Suite 202, Fort
Myers, FL 33919
Joseph Mallon, Ostego Bay Foundation Inc./Estero Bay Marine Laboratory Inc., P.O.
Box 0875, Fort Myers Beach, FL 33931
Kirk Martin, CDM/Missimer International, Inc., 8140 College Parkway, Suite 202, Fort
Myers, FL 33919
Jack McCoy, Lee County Natural Resources Division, P.O. Box 398, Fort Myers, FL 33902
Thomas Missimer, CDM/Missimer International, Inc., 8140 College Parkway, Suite 202, Fort
Myers, FL 33919
Hugh Mitchell-Tapping, Ostego Bay Foundation Inc./Estero Bay Marine Laboratory Inc., P.O.
Box 0875,Fort Myers Beach, FL 33931
Douglas Moulton, C.D.M., 2301 Maitland Center Parkway, Suite 301, Maitland, FL 32751
Akin Owosina, SFWMD, 2301 McGregor Blvd, Fort Myers, FL 33901
Hope Radin, SFWMD, 3301 Gun Club Rd., West Palm Beach, FL
Ronald Reese, U.S. Geological Survey, 9100 NW 36th Street, Suite 107, Miami, FL 33178
Thomas Scott, Florida Geological Survey, 903 West Tennessee St., Tallahassee, FL 32304'
Tokiyuki Sato, Institute of Applied Earth Sciences Mining College, Akita University, Tegata-
Gakuencho 1-1, Akita, 010, Japan
Andrew Tilton, Johnson Engineering, Inc.P.O. Box 1550, Fort Myers. FL 33902
Leslie Wadderburn, Consulting Hydrogelogist
Charles Walker, CDM/Missimer International, Inc., 8140 College Parkway, Suite 202, Fort
Myers, FL 33919
Micheal Weinberg, Water Resource Solutions, 428 Pine Island Rd. SW, Cape Coral, FL 33991
Cathy Williams, Ostego Bay Foundation Inc./Estero Bay Marine Laboratory Inc., P.O.
Box 0875, Fort Myers Beach, FL 33931
Thomas Winter, Ostego Bay Foundation Inc./Estero Bay Marine Laboratory Inc., P.O.
Box 0875, Fort Myers Beach, FL 33931






FLORIDA GEOLOGICAL SURVEY


CONTRIBUTIONS OF DURWARD H. BOGGESS
TO THE HYDROLOGY AND GEOLOGY
OF LEE COUNTY, FLORIDA

Thomas M. Missimer,
CDM/Missimer International, Inc., 8140 College Parkway, Suite 202, Fort Myers, Florida 33919

ABSTRACT

Sparse investigation of the hydrology and geology of Lee County, Florida was conducted
before Durward Boggess established the U.S. Geological Survey office in Fort Myers during
1966. Past work included a general description of the geology along the banks of the
Caloosahatchee River (Heilprin, Dall, DuBar) and some paleontological studies of barrow pit
spoils piles and some surface-water studies in a few streams. Durward Boggess quickly grasped
the water-supply problems of Lee County and recognized the need for both surface-water and
groundwater data.
The completion of the Okeechobee Waterway (construction of S-79) occurred only a short
time before Mr. Boggess moved to Lee County. In 1966, the Caloosahatchee River was believed
to be the most reliable source of water supply for the City of Fort Myers and the unincorporated
areas of Lee County. Intakes were designed and constructed about 1 mile upstream of the W.
P. Franklin Dam (S-79) on the river. These intakes fed the artificial recharge system for the City
of Fort Myers Wellfield via a pipeline and the new Lee County Water Treatment Plant. Mr.
Boggess was concerned about the proximity of the intake structures to the lock through S-79.
Each time a boat passed through the lock in dry periods, a slug of saltwater moved upstream.
So, his first work in Lee County was on how to control the upstream movement of saline water
in the Caloosahatchee River.
Among the many contributions made by Durward Boggess to the study and management of
water resources in Lee County were: 1) the establishment of permanent gaging stations on the
Caloosahatchee River and other larger streams in Lee County, 2) the establishment of the crest-
stage gages in Lee County to assess flooding and drainage problems, 3) the creation of an
extensive data base on the geology and hydrology of Lee County, 4) the initial mapping of the
shallow and intermediate aquifer systems, 5) the definition and naming of the principal aquifers
used in Lee County, including the Lower Hawthorn Aquifer, the Upper Hawthorn Aquifer (now
termed the Mid-Hawthorn Aquifer), the Sandstone Aquifer, and the water-table aquifer, 6) the
recognition that brackish, saline-water in the Lower Hawthorn Aquifer was a resource to be con-
served and would be a water supply for the future, 7) helped establish how saline water inter-
acted with the shallow aquifer system of Sanibel Island and helped established development
practices that would be fundamental to the writing of the City of Sanibel Comprehensive Land
Use Plan, 8) recognized that cut and fill landfills, which were the state-of-the-art landfill type at
that time, were causing groundwater contamination, 9) suggested that the shallow groundwater
system in southern and eastern Lee County would be the source for future public water supplies
in Lee County, 10) recognized that the Mid-Hawthorn Aquifer was being over-pumped in Cape
Coral and Fort Myers, 11) recognized that improper well construction practices were causing
contamination of the freshwater resources of the county with saline water, which led to the adop-
tion of new well construction codes and the establishment of a well plugging program, 12) rec-
ognized that over-drainage of the Lehigh Acres area of Lee County was adversely affecting the
water resources and wetlands, and 13) convinced the Lee County government that the planning
process should include the management of the groundwater resources.
Without the scientific expertise and insight of Durward Boggess, Lee County would have had






SPECIAL PUBLICATION NO. 49


severe water supply problems many years ago. Durward Boggess believed that it was very
important for the public to understand how the hydrologic system functioned and he spent much
time with the media and interested citizens to help educate them. He was one dedicated indi-
vidual, who cared about Southwest Florida, that made a difference in molding the future man-
agement of water resources.

INTRODUCTION

Prior to the 1960's, geological and hydrological work on Lee County, Florida was very limit-
ed (Figure 1). Initial geological and paleontological investigation on this region began in the late
1880's. The first description of geological work in southwestern Florida was that of Heilprin
(1887), who wrote "Prior to our visit, the only portion of the state that had been examined geo-
logically, or on which a geological report had been prepared, was the region lying north of a line
running almost due northeast from the Manatee River, just south of Tampa Bay, to the east coast.
Below all this was conjectural, although the existence of certain limestones of undetermined age
was hinted at, or even located, by a number of causal observers (Tuomey, Conrad) who chanced
to navigate some of the outer waters. Such a limestone was reported by Tuomey to be found in
Charlotte Harbor, but the exact locality of its occurrence is not noted." Heilprin (1887) described
the geology and paleontology of the banks of the Caloosahatchee River from Fort Myers east to
past Labelle in Hendry County. Rather extensive works on the paleontology of the exposed
Pliocene and Pleistocene sediments along the Caloosahatchee River, Shell and Alligator creeks
(Charlotte County) were made by William H. Dall of the Wagner Free Institute of Philadelphia.
Dall (1890-1903) described many of the most common mollusk species of the Neogene
sediments. Additional paleontological investigations were conducted in parts of Lee County by
Wendall C. Mansfield (an original field assistant of Dall), Druid Wilson, Helen I. Tucker, and Axel
Olsson. Some of the data collected are published in Tucker and Wilson (1932-33) and Olsson
and Harbison (1953), but no stratigraphic descriptions were made. Petroleum exploration began
in Southwest Florida in the 1930's with a number of "shallow" dry holes being drilled in Charlotte,
Lee, and Collier counties. Few data were preserved from this early deep exploration work.
Detailed investigations of the exposed Neogene paleontology and geology of the
Caloosahatchee River from Lee County and Hendry County were published by DuBar (1958)
with another study conducted in Charlotte County (DuBar, 1962). A surface geological map of
the area was published by Parker and Cooke (1944), based on minimal data collected from
exposures and barrow pits.
Some reconnaissance work on the hydrogeology of the Southwest Florida region was
undertaken in the 1940's as a part of extensive studies directed by Gerald Parker of the U. S.
Geological Survey. Some preliminary data on rainfall along with some logs of wells in Hendry
County immediately to the east of Lee County were published in Parker et al. (1955). A study of
surface water flows and surface-water quality in a few streams in Lee County was published by
Kenner and Brown (1956). The U. S. Geological District office in Tallahassee was concerned
about the lack of hydrogeologic data and aquifer definitions in the early 1960's and Nevin Hoy
was assigned to make an assessment of the hydrology and geology of Lee County. A draft report
by Hoy was submitted to the Florida Geological Survey but not published, because of insufficient
data.
The U. S. Geological Survey decided to open a field office in Fort Myers under the direction
of the Subdistrict office in Miami during 1965. A senior hydrologist with the U.S.G.S. in Maryland,
Durward H. Boggess, was assigned to open the office. His assignment was to assess the water
resource problems of Lee County, to develop a hydrogeologic data base, and to develop fund-
ing sources for conducting hydrologic investigations.






FLORIDA GEOLOGICAL SURVEY


SCALE

25 MILES

40 KILOMETERS


Figure 1. Map of Lee County showing locations mentioned in text.




In 1966, Lee County was a rural region, with a predominantly agricultural economy and a devel-
oping tourist industry. Population growth was beginning to accelerate and a number of water
supply problems were becoming evident. Water supplies for the new residents of the county
along with the expanding agricultural uses were beginning to become problematical. Durward
Boggess arrived in Lee County in 1966 at a critical time in its development history. He made an
immediate and long-term impact on the management of the water resources of Lee County. The
problems he outlined in "Water-Supply Problems in Southwest Florida" (Boggess, 1968) set the
beginning of his work on the geology and hydrology of Lee County. During the 13 years of serv-
ice with the U. S. Geological Survey in Lee County, Durward Boggess made numerous contri-
butions to the geologic and hydrologic knowledge of Southwest Florida. This paper outlines only
a few of these contributions.






SPECIAL PUBLICATION NO. 49


The Caloosahatchee River as a Water Supply Source
Construction of the Okeechobee Waterway was completed only about a year before
Durward Boggess came to Lee County. In 1966, the City of Fort Myers was having serious prob-
lems with its wellfield, which was the only potable public water-supply source for the city.
Therefore, the city decided to pump surface water from the Caloosahatchee River at the
upstream side of the primary salinity control structure (S-79) to the wellfield in order to recharge
the system via a series of canals. An assessment of the City of Fort Myers wellfield and the
Caloosahatchee River recharge system lead to the first Boggess report on the hydrogeology of
Southwest Florida (Boggess, 1968). Use of the Caloosahatchee River as a water supply source
had some serious problems, because of the lock in the river, which allowed boat traffic to use the
waterway. Each time a boat passed through the lock, a slug of saline-water was allowed to
migrate upstream. This problem was recognized early by Durward Boggess and he assisted the
City of Fort Myers in studying the problem by conducting controlled flushing experiments with the
U. S. Army Corps of Engineers, who were responsible for operation of the waterway (Boggess,
1970a). A cooperative program was initiated between the U. S. Geological Survey and the City
of Fort Myers to establish the first locally funded hydrological studies in Southwest Florida.
Boggess continued to study the saline-water intrusion problem in the river for many years
(Boggess, 1970b; 1972) until the discharge of water from Lake Okeechobee and a bubble cur-
tain were used to control the upstream movement of the saline water.
Unfortunately, the City of Fort Myers and later, Lee County Utilities, did not heed the advice
of Durward Boggess who suggested that the water supply intakes in the Caloosahatchee River
should be moved upstream several miles in order to avoid the salinity problem. The City of Fort
Myers is currently in the process of developing a new water supply source with the intention of
discontinuing use of the Caloosahatchee River.

The Mobil Oil Drilling Program
During the later part of 1966, a geologist from Mobil Oil Corporation, called the U.S.G.S
office in Fort Myers to request some information on the shallow geology of the Southwest Florida
area. A meeting was initiated between a team of Mobil geologists and Durward Boggess to dis-
cuss a proposed confidential test drilling program that Mobil Oil intended to initiate in Southwest
Florida. Mobil was actively involved in a petroleum exploration program in Southwest Florida at
that time. There was some suggestion that the structure of the top of the middle Miocene and
the top of the Eocene sediments in the region could give significant clues with regard to where
to drill in the 12,000 foot zone of the late Cretaceous Sunniland Formation, which was the oil pro-
duction horizon in the area. Durward Boggess and Mobil Oil struck a deal that proved to be the
key factor in the development of an extensive hydrogeologic data base in Southwest Florida.
Mobil decided to drill several hundred test holes to depths ranging from 200 to 1500 feet through-
out Southwest Florida. Drill cuttings would be collected from each well, geologist logs would be
made, and geophysical logs (electric and gamma ray) would be run on each test well. The deal
was that if Durward Boggess agreed to help obtain permission to drill the test wells in road right-
of-ways and assisted in the data collection, he would be given copies of all raw data and geo-
physical logs as long as he agreed not to make the information public for two years (shallow mid-
dle Miocene wells) or five years (upper Eocene wells). Despite being a one man office with sig-
nificant responsibilities and some internal problems with U.S.G.S. policy, the agreement was
made. For over a year, geological data were collected and even water quality information was
obtained. This information formed the hydrogeological data base that allowed Durward Boggess
to define and name the primary freshwater aquifers in Lee County and to suggest where future
water supplies could be obtained (Sproul, Boggess, and Woodard, 1972; Boggess, Missimer,
and O'Donnell, 1977).






FLORIDA GEOLOGICAL SURVEY


The Cape Coral Canal System Salinity Barrier Issue
In the late 1960's and early 1970's, a new urban area in western Lee County, Cape Coral,
was being developed. Gulf American Land Corporation was in the process of digging hundreds
of lineal miles of canals at depths near or below sea level to both obtain fill material to increase
the altitude of the land for flood control and septic tank function and to allow boat access.
In the northwestern part of the development area (north of S.R. 78), the state and local regula-
tory bodies were concerned about the potential for saltwater intrusion into the interior of the area
(Figure 1). Durward Boggess was requested to assess the situation and assist both the regula-
tory agencies and the developer to decide where to control the potential landward movement of
tidal surface-water (saltwater intrusion) through the canal system. After extensive discussion,
Durward Boggess recommended that Burnt Store Road be designated as the salinity control line.
A series of four control structures were constructed along this north-south oriented road. This
was the first concerted effort in Lee County to control the intrusion of tidal saline-water into inte-
rior areas. The precedent set by this decision set the trend for future development throughout
Southwest Florida.

Contamination of the Fresh Groundwater Resources with Artesian Saline-Water
When Durward Boggess arrived in Southwest Florida, all of the water wells in the region
were constructed by the cable-tool method using as little casing as possible. Many of the wells
tapped deep aquifers, under artesian pressure, that yielded saline water. These deep wells were
used for irrigation of crops and for frost protection to some degree. Boggess recognized that
these wells were problematical allowing the entry of saline water into the freshwater aquifers of
Southwest Florida. An earlier study by Klein, Schroeder, and Lichtler (1962) in Hendry County
had documented this problem, and Boggess (1968) first discussed the significance of the prob-
lem in Lee County.
The issue of improper well construction and the adverse effects on groundwater quality was
studied by Boggess for his entire career in Southwest Florida. He demonstrated that if a deep
well was properly plugged, the contamination caused by the discharge of saline-water into the
water-table aquifer was rapidly attenuated by dilution with rainfall (Boggess, 1973). Saline-water
intrusion into confined freshwater aquifers, such as the Sandstone Aquifer in eastern Lee County
or the Mid-Hawthorn Aquifer in western Lee County proved to be a nearly permanent situation
with very slow flushing and dilution (Sproul, Boggess, and Woodard, 1972; Boggess, Missimer,
and O'Donnell, 1977). Boggess recognized that the deep aquifer intrusion of saline-water into
the shallower fresh-water aquifers was not the only problem related to well construction (Figure
2). In Cape Coral, thousands of irrigation and single-family home supply wells were tapping the
Mid-Hawthorn Aquifer. The potentiometric surface of the aquifer was drawn down far below sea
level. Most of the small-diameter irrigation wells that were constructed into the Mid-Hawthorn
Aquifer had steel casings driven by the cable-tool drilling method and contained no cement grout.
Within a few years after construction, corrosion holes formed in the casing at near sea level
cathodicc corrosion). The saline-water occurring within the water-table aquifer adjacent to tidal
canals began to drain into the Mid-Hawthorn Aquifer via gravity feed. This problem virtually
destroyed a large part of the Mid-Hawthorn Aquifer in Cape Coral (Boggess, Missimer and
O'Donnell, 1977).
The research performed by Durward Boggess on the effects of improper well construction
on the fresh groundwater resources lead to the development of new well construction permitting
ordinances imposed by the Lee County government, the South Florida Water Management
District, and years later by the City of Cape Coral. Boggess helped initiate a well plugging pro-
gram to eliminate thousands of wells causing groundwater contamination.







SPECIAL PUBLICATION NO. 49


WELL A
CONTROL VALVE CLOSED
HOLES IN CASING NEAR
LAND SURFACE


WELL B


WELL C


CONTROL VALVE OPEN CONTROL VALVE CLOSED
OR NO VALVE


- WELL CASING -


WELL CASING -


I I


I 1< OPEN BORE
I HOLE
2 (NO CASING)
I I
I I


I I
I I


ARROWS DENOTE
DIRECTION OF
SALINE WATER
I I MOVEMENT


LAND SURFACE
WATER-TABLE AQUIFER
(FRESH WATER)


CONFINING BED
CEMENT GROUT

UPPER PART OF THE
HAWTHORN FORMATION
OR
TAMIAMI FORMATION
(FRESH WATER)


CONFINING BED


LOWER HAWTHORN SUWANEE
OR
DEEPER AQUIFER
UNDER PRESSURE
(SALINE WATER)


Figure 2. Diagram showing how saline-water contaminates freshwater aquifers by improper well
construction or improper management. Well A has corrosion holes in the upper part of the cas-
ing and is not cased to the top of the aquifer containing pressurized saline water. Saline water
migrates into both the confined and unconfined fresh-water aquifers. Well B also is not cased to
the top of the pressurized saline-water aquifer and the wellhead value is either open or broken
off. Saline-water enters all freshwater aquifers via the well or at land surface. Well C is a proper-
ly constructed well with the proper depth of casing and cement grout in the annulus. No saline
water contamination occurs in this well.

Aquifers of Lee County Defined and Named
Little was known about the aquifer system beneath Lee County in 1966. On the Florida East
Coast, the aquifer system was rather simple with the unconfined aquifer in the southeast area
being termed the Biscayne Aquifer and the deep aquifer system being the Floridan Aquifer
(Parker et al., 1955). Boggess recognized that the aquifer system in Lee County was much more
complex than the Florida East Coast with a larger number of aquifers occurring with different
pressures and water qualities. Boggess began to use formal names for the aquifers in order to
communicate with the public in 1970. He was aware that the Floridan Aquifer beneath Lee
County contained numerous individual flow zones. The uppermost two zones that were used for
irrigation and contained slightly saline water, he named in ascending order, the Suwannee
Aquifer and the Lower Hawthorn Aquifer (Figure 3). Two confined aquifers contained freshwa-
ter over large areas of the county. In western Lee County he named the confined freshwater
aquifer the Upper Hawthorn Aquifer (now termed the Mid-Hawthorn Aquifer) and in eastern and
southern Lee County he named the confined freshwater aquifer the Sandstone Aquifer. Boggess


0h
f 7/ h\


I


I






FLORIDA GEOLOGICAL SURVEY


also recognized that another confined freshwater aquifer occurred in the southern part of Lee
County in the Bonita Springs area, which was later termed the Lower Tamiami Aquifer (Figure 3).
There was considerable scientific importance in defining and naming these aquifers. Water
level and quality information could be organized into a consistent scheme using the definitions.
In subsequent years, the aquifer data were used to locate large public supply wellfields and to
develop regional water supply plans.
The definition and naming of the aquifers in Lee County also served an even more impor-
tant function. It allowed the public and press to understand the groundwater system to a greater
degree, which lead to better planning and political decisions on protection and management of
the groundwater resources.

Contamination Caused by Cut and Fill Municipal Landfills
In the 1960's and 1970's, the "state of the art" sanitary landfill design in Florida was the cut
and fill type. In this type of landfill, a series of trenches were dug from land surface into the sur-
ficial aquifer to depths ranging from 8 to 20 feet below surface. A typical "cell" averaged about
15 feet in depth and was up to about 1000 feet in length. Water was removed from the trench
during construction and filling via dewatering. No liners or other methods were used to separate
the municipal waste buried in the cell from the surrounding groundwater. Upon completion of fill-
ing with waste, the trench was covered and another trench was constructed beside it.

The City of Fort Myers operated a cut and fill landfill east of town along Buckingham Road
(Figure 1). The city established a groundwater quality monitoring program around the landfill to
assess any impacts to the groundwater system and at the same time requested the U. S.
Geological Survey to assist in the location of a new landfill site. In 1974, Durward Boggess
informed the City of Fort Myers that the landfill was having an adverse impact on the shallow
groundwater system adjacent to the landfill and on some surface-water bodies that drained into
the headwaters of the Six-Mile Cypress. A report was delivered to the city in 1975 to document
the findings (Boggess, 1975). Ultimately, the city consolidated its efforts to locate a new landfill
site with the Lee County Government and a site was chosen south of State Road 82 (Gulf Coast
Landfill). It should be noted that Durward Boggess advised the Lee County Government that the
site chosen was not ideal for a landfill location, but the county had no other options at the time
because of timing and public protests.

The study of the City of Fort Myers landfill as well as others in South Florida lead to major rule
revisions by the Florida Department of Environmental Regulation (now Florida Department of
Environmental Protection). Cut and fill landfills were outlawed and all landfills ultimately were
required to be lined with impervious material to prevent groundwater contamination. Durward
Boggess was one of the first hydrologists to point out the problem to the local and state govern-
ment officials.

Saline-Water Intrusion into the Shallow Freshwater System of Sanibel Island, Florida
For many years Sanibel Island was a sparsely populated barrier island lying southwest of
Fort Myers. It was connected to the mainland by a ferryboat that took residents and day-trippers
to and from the island. In 1965, a bridge was completed to the island and activity greatly
increased. A building boom began on the island in the early 1970's with a number of deep canals
and artificial lakes being constructed. The shallow aquifer system on Sanibel Island contained
a fragile freshwater lense that was critical to the maintenance of an internal freshwater marsh
and the island vegetation. The construction activity was causing the intrusion of saltwater into
the shallow aquifer system and was destroying the freshwater lense.







SPECIAL PUBLICATION NO. 49


Figure 3. The original aquifer terminology for Lee County as named by Durward Boggess (modi-
fied from Sproul, Boggess & Woodard, 1972).






FLORIDA GEOLOGICAL SURVEY


Durward Boggess was asked to study the problem and conducted an investigation of the
shallow water resources over a period of several years in the early 1970's (Boggess, 1974). The
information obtained from this investigation was used to develop new construction standards for
Sanibel Island and ultimately the information was used to help develop the comprehensive land
use plan for the island (after the incorporation of the City of Sanibel).

Wetland Destruction in Lehigh Acres Caused by Over-Drainage
The development of a vast tract of land in eastern Lee County was very active in the late
1960's and early 1970's. Lehigh Acres was being carved out of pristine pine flatwoods and fresh-
water wetland areas. The area was flat and poorly drained, so a network of deep drainage
canals was being constructed to drain the area to the north via the Orange River, Bedman Creek,
and other streams to the Caloosahatchee River. Over a short period of time, a major wetland
feature in the area, Halfway Pond, dried up and was lost. There was considerable public out-
rage over the destruction of this 400-acre pond and a number of state, federal, and local agen-
cies took interest in the issue.
Durward Boggess was requested to make a rapid investigation of the area to provide a
hydrogeologic assessment of the effects of drainage on the groundwater system (Boggess and
Missimer, 1975). The report on the area was used by federal agencies to stop the over-drainage
of the wetlands and the water management district required that water level control structures be
placed in the drainage canals to retain groundwater.

Saline Water as a Future Water Supply for Lee County
Beginning in the late 1960's, Durward Boggess took a strong interest in the artesian, saline
water resources of Lee County. First, he recognized that the deep, free-flowing wells were a
source of contamination to the freshwater aquifers. However, as he studied the aquifers, he real-
ized that these waters were also resources that could be treated using new water treatment tech-
nology. This realization was confirmed, when he was requested by the Island Water Association
of Sanibel Island to help assist in the development of a public water supply system on the island.
In the past, only shallow wells and cisterns were used for water supply on the island, but with
rapid development, the shallow aquifer was not capable of yielding the necessary quantity of
water required. The Island Water Association decided to use deep wells tapping the Lower
Hawthorn Aquifer System to feed a new desalination system that used the electrodialysis
process to desalt the water. Boggess provided considerable hydrogeologic data and expertise
to develop the first saline-water wellfield in the Lee County (Boggess, 1974b; 1974b; Boggess
and O'Donnell, 1982).
Over a period of several years, Boggess accumulated a large data base on the saline water
resources of Lee County. In 1974, he published a critical document that provided the key hydro-
geologic and water quality information to allow the successful development of those resources
(Boggess, 1974). In the mid-1970's, Cape Coral and Pine Island developed wellfields to use the
saline water resources, using the initial data base and forethought of Durward Boggess.

The Water-Table and Sandstone Aquifers of Eastern and Southeastern
Lee County as Future Water Supplies
In his investigations of Lee County, Durward Boggess realized in the early 1970's that the
county could be divided into the water poor western and northern area and the water rich east-
ern and southern area. From the geologic data base obtained from the Mobil Oil test drilling pro-
gram and from extensive inventorying of existing wells, Boggess believed that the shallow and
immediate aquifers in eastern and southern Lee County would be the only viable freshwater
resources that could be developed in the future. During the later part of his career, he concen-






SPECIAL PUBLICATION NO. 49


treated on compiling the hydrogeologic investigation in this area (Boggess, Missimer and
O'Donnell, 1982; Boggess and Watkins, 1986). The information gathered by Boggess in east-
ern and southern Lee County was instrumental in the successful development of the Lehigh
Acres Utilities Wellfield (Sandstone Aquifer), the Florida Cities Green Meadows Wellfield (water-
table and Sandstone aquifers), the Lee County South Wellfield (water-table and Sandstone
aquifers), the Gulf Utilities north and south wellfields (water-table aquifer), and the Bonita Springs
Utilities west and east wellfields (Lower Tamiami Aquifer).

The Well Schedule and Well Log Data Base
Over his 13 years with the U. S. Geological Survey in Lee County, Durward Boggess was
meticulous about the compilation of a well and geologic data base. He used topographic maps
of the entire county to locate every well on which he could obtain data. The well was given a
number and the data were recorded in a series of well schedules. When a geologic log existed,
it was given a corresponding number and was recorded in a file. The same was true for water
quality analyses. It was a time-consuming and tedious job to establish and maintain this record-
keeping system, but it was critical in developing an accurate and detailed assessment of the
groundwater resource. Data were collected on over 4000 wells in Lee County during the
Boggess years. This is the most extensive hydrogeologic data base established for any county
in the state of Florida and the credit for it goes to Durward Boggess.

Durward H. Boggess, The Man
Durward Boggess left a reputation as a man of impeccable integrity, who could always be
relied upon to give fair and unbiased technical council. He never turned down any information
request and talked to anyone who contacted the U. S. Geological Survey office. He established
an excellent rapport with the press and helped educate numerous, young reporters. He talked
with and provided information to elected officials, but he was never political, in the sense of pur-
suing some personal agenda. He was particularly skilled at finding solutions to the acquisition
of technical data in the field, such as how to keep old, worn-out recording devices working, or
how to collect flood stage data at minimal cost (crest-stage gages), or how to collect water sam-
ples at depths without expensive devices. He was also skilled at teaching water resources data
collection methods to young geologists and to old engineers without ruffling sensitive egos.
Durward Boggess never had said anything derogatory about any person, even when he was crit-
icized. In his quiet, gentle way, he was able to obtain the funding he needed to perform scien-
tific investigations of the highest quality without resorting to crisis creation via the media.

CONCLUSIONS

The contributions of Durward Boggess to the knowledge on the hydrology and geology of
Lee County is a case study on how one man with integrity and spirit can make a profound con-
tribution to science. The methods Mr. Boggess employed to glean the most information possi-
ble with minimal budgets is a case study for all practicing hydrologists and hydrogeologists.
Without the development of the data base and the forethought given by Durward Boggess, the
water resources of Lee County would have been severely damaged two decades ago. These
contributions are still being used today as the population growth of Lee County causes further
development of the water resources. Every citizen of Southwest Florida owes a debt of gratitude
to Durward Boggess for his diligence and perseverance in working on the hydrology and geolo-
gy of Lee County, Florida.






FLORIDA GEOLOGICAL SURVEY


REFERENCES

Dall, W. H., 1890-1903, Contributions to the Tertiary fauna of Florida with special reference to the
Miocene Silex beds of Tampa and the Pliocene beds of the Caloosahatchee River: Wagner
Free Institute Science Trans., v. 3, 6 parts, 1654 pp.

DuBar, J. R., 1958, Stratigraphy and paleontology of the late Neogene strata of the
Caloosahatchee River area of southern Florida: Florida Geological Survey Bulletin No. 40,
267 pp.

DuBar, J. R., 1962, Neogene biostratigraphy of the Charlotte area in Southwestern Florida:
Florida Geological Survey Bulletin No. 43, 83 pp.

Heilprin, A., 1887, Explorations on the West Coast of Florida and in the Okeechobee Wilderness:
Wagner Free Institute of Philadelphia, 134 pp.

Kenner, W. E., and Brown, E., 1956, Surface water resources and quality of waters in Lee
County, Florida: Florida Geological Survey Information Circular No. 7, 69 pp.

Klein, H., Schroeder, M. C., and Lichtler, W. F., 1964, Geology and groundwater resources of
Glades and Hendry counties, Florida: Florida Geological Survey Rept. of Investigations No.
37, 101 pp.

Olsson, A. A., and Harbison, A., 1953, Pliocene Mollusca of Southern Florida: Academy of
Natural Science, Philadelphia, Mon. 8, 457 pp.

Parker, G. G., and Cooke, C. W, 1944, Late Cenozoic geology of southern Florida with a dis-
cussion of the ground water: Florida Geological Survey Geological Bulletin No. 27, 119 pp.

Parker, G. G., Ferguson, G. E., and Love, S. K., 1955, Water resources of southeastern Florida:
U. S. Geological Survey Water-Supply Paper 1255, 965 pp.

Tucker, H. I., and Wilson, D., 1932-1933, Some new and otherwise interesting fossils from the
Florida Tertiary: Bull. Am. Paleontology, v. 18, p. 39-82.

COMPLETE PUBLICATIONS LIST OF DURWARD H. BOGGESS

Lee County:

Boggess, D. H., 1968, Water-supply problems in southwest Florida:U.S. Geological Survey
Open-File Report FL-68003, 27 p.

Boggess, D. H., 1970, A test of flushing procedures to control salt-water intrusion at the W.F.
Franklin Dam near Fort Myers, Florida: Florida Bureau of Geology Information Circular 62.
pt 1, p. 1-15.

Boggess, D. H., 1970, The magnitude and extent of salt-water contamination in the
Caloosahatchee River between La Belle and Olga, Florida: Florida Bureau of Geology
Information Circular 62, pt. 2, p. 17-39.






SPECIAL PUBLICATION NO. 49


Boggess, D. H., 1972, Controlled discharge form the W.P. Franklin Dam as a means of flushing
saline water from the fresh-water reach of the Caloosahatchee River, Lee County, Florida:
U.S. Geological Survey Open-File Report FL-72028, 45 p.

Boggess, D. H., 1973, The effects of plugging a deep artesian well on the concentration of
chloride in water in the water-table aquifer at Highland Estates, Lee County, Florida:
U.S. Geological Survey-Open File Report FL73003, 20 p.

Boggess, D. H. 1974, Saline ground-water resources of Lee County, Florida: U.S. Geological
Survey Open-File Report 74-247, 62 p.

Boggess, D. H., 1974, The shallow fresh-water system of Sanibel Island, Lee County, Florida,
with emphasis on the sources and effects of saline water: Florida Bureau of Geology Report
of Investigations 69, 52 p.

Boggess, D.H., 1975, Effects of a landfill on ground-water quality: U.S. Geological Survey Open-
File Report 75-594, 44 p.

Boggess, D. H., and Missimer, T. M., 1975, A reconnaissance of hydrogeologic conditions in
Lehigh Acres and adjacent Lee County, Florida: U.S. Geological Survey Open-File 75-55,
106 p.

Boggess, D. H.,, Missimer, T. M., and O=Donnell, T. H., 1977, Saline-water intrusion related to
well construction in Lee County, Florida: U.S. Geological Survey Water-Resources
Investigations 77-33, 29 p.

Boggess, D. H., Missimer, T. M. and O=Donnell, T. H., 1981, Hydrogeologic sections through Lee
County, and adjacent areas of Hendry and Collier counties, Florida: U. S. Geological Survey
Water-Resources Investigations Open-File Report 81-639, 1 sheet.

Boggess, D. H., and O=Donnell, T.H., 1982, Deep artesian aquifers of Sanibel and Captiva
Islands, Lee County, Florida: U. S. Geological Survey Open-File Report 82-253, 32 p.

Boggess, D. H., and Watkins, F. A., Jr., 1986, Surficial aquifer system in eastern Lee County,
Florida: U. S. Geological Survey Water-Resources Investigations 85-4161, 59 p.

Fitzpatrick, D. J., Boggess, D. H., Missimer, T. M., and O=Donnell, T. H., 1979, Saltwater intru-
sion in the City of Cape Coral: U. S. Geological; Survey Professional Paper 1150, p. 114-
115.

Missimer, T. M., and Boggess, D. H., 1974, Fluctuations of the water table in Lee County, Florida,
1969-1973: U. S. Geological Survey Open-File Report FL-74019, 41 p.

Sproul, C. R., Boggess, D. H., and Woodard, H. J., 1972, Saline-water intrusion from deep arte-
sian sources in the McGregor Isles areas of Lee County, Florida: Florida Bureau of Geology
Information Circular 75, 30 p.






FLORIDA GEOLOGICAL SURVEY


Other:

Adams, J. K., and Boggess, D. H., 1963, Water-table, surface-drainage, and engineering soils
map of the Saint Georges area, Delaware: U. S. Geological Survey Hydrologic
Investigations Atlas, HA-60.

Adams, J. K., and Boggess, D. H., 1964, Water-table, surface-drainage, and engineering soils
map of the Wilmington area, Delaware: U.S. Geological Survey Hydrologic Investigations
Atlas, HA-79.

Adams, J. K., and Boggess, D. H., 1964, Water-table, surface-drainage, and engineering soils
map of the Taylors Bridge area, Delaware: U. S. Geological Survey Hydrologic
Investigations Atlas, HA-80.

Adams, J. K., and Boggess, D. H., 1964, Water-table, surface-drainage, and engineering soils
map of the Sharptown area, Delaware: U. S. Geological Survey Hydrologic Investigations
Atlas, HA-84.

Adams, J. K., and Boggess, D. H, 1964, Water-table, surface-drainage, and engineering soils
map of the Hickman area, Delaware: U. S. Geological Survey Hydrologic Investigations
Atlas, HA-100.

Adams, J. K., and Boggess, D. H., 1964, Water-table, surface-drainage, and engineering soils
map of the Ellendale Quadrangle, Delaware: U. S. Geological Survey Hydrologic
Investigations Atlas, HA-101.

Adams, J. K., and Boggess, D. H., 1964, Water-table, surface-drainage, and engineering soils
map of the Harbeson Quadrangle, Delaware: U. S. Geological Survey Hydrologic
Investigations Atlas, HA-108.

Adams, J. K., and Boggess, D. H., 1964, Water-table, surface-drainage, and engineering soils
map of the Trap Pond area, Delaware: U. S. Geological Survey Hydrologic Investigations
Atlas, HA-120.

Adams, J. K., Boggess, D. H., and Coskery, 0. J., 1964, Water-table, surface-drainage, and
engineering soils map of the Clayton area, Delaware: U. S. Geological Survey Hydrologic
Investigations Atlas, HA-83.

Adams, J. K., Boggess, D. H., and Coskery, 0. J., 1964, Water-table, surface-drainage, and
engineering soils map of the Seaford East Quadrangle, Delaware: U. S. Geological Survey
Hydrologic Investigations Atlas, HA-106.

Adams, J. K., Boggess, D. H., and Coskery, 0. J., 1964, Water-table, surface-drainage, and
engineering soils map of the Frankford area, Delaware: U. S. Geological Survey Hydrologic
Investigations Atlas, HA-119.

Adams, J. K., Boggess, D. H., and Davis, C. F., 1964, Water-table, surface-drainage, and engi-
neering soils map of the Dover Quadrangle, Delaware: U. S. Geological Survey Hydrologic
Investigations Atlas, HA-139.






SPECIAL PUBLICATION NO. 49


Adams, J. K., Boggess, D. H., and Davis, C. F., 1964, Water-table, surface-drainage, and engi-
neering soils map of the Lewes area, Delaware, U. S. Geological Survey Hydrologic
Investigations Atlas, HA-103.

Boggess, D. H., and Adams, J. D., 1963, Water-table, surface-drainage, and engineering soils
map of the Neward area, Delaware: U. S. Geological Survey Hydrologic Investigations
Atlas, HA-64.

Boggess, D. H., and Adams, J. K., 1964, Water-table, surface-drainage, and engineering soils
map of the Middletown area, Delaware: U. S. Geological Survey Hydrologic Investigations
Atlas, HA-82.

Boggess, D. H., and Adams, J. K, 1964, Water-table, surface-drainage, and engineering soils
map of the Greenwood Quadrangle, Delaware: U. S. Geological Survey Hydrologic
Investigations Atlas, HA-99.

Boggess, D. H., and Adams, J. K., 1964, Water-table, surface-drainage, and engineering soils
map of the Seaford West area, Delaware: U. S. Geological Survey, Hydrologic
Investigations Atlas, HA-105.

Boggess, D. H., and Adams, J. K., 1964, Water-table, surface-drainage, and engineering soils
map of the Bethany Beach area, Delaware: U. S. Geological Survey Hydrologic
Investigations Atlas, HA-122.

Boggess, D. H., and Adams, J. K., 1964, Water-table, surface-drainage, and engineering soils
map of the Laurel area, Delaware: U. S. Geological Survey Hydrologic Investigations Atlas,
HA-123.

Boggess, D. H., and Adams, J. K., 1965, Water-table, surface-drainage, and engineering soils
map of the Millsboro area, Delaware: U. S. Geological Survey Hydrologic Investigations
Atlas, HA-121.

Boggess, D. H., and Adams, J. K., 1965, Water-table, surface-drainage, and engineering soils
map of the Little Creek Quadrangle, Delaware: U. S. Geological Survey Hydrologic
Investigations Atlas, HA-134.

Boggess, D. H., and Adams, J. K., 1965, Water-table, surface-drainage, and engineering soils
map of the Kenton area, Delaware: U. S. Geological Survey Hydrologic Investigations Atlas,
HA-138.

Boggess, D. H., Adams, J. K., and Coskery, 0. J., 1964, Water-table, surface-drainage, and engi-
neering soils map of the Milton Quadrangle, Delaware: U. S. Geological Survey Hydrologic
Investigations Atlas, HA-102.

Boggess, D. H., Adams, J. K., and Davis, C. F., 1964, Water-table, surface-drainage and engi-
neering soils map of the Smyrna area, Delaware: U. S. Geological Survey Hydrologic
Investigations Atlas, HA-81.






FLORIDA GEOLOGICAL SURVEY


Boggess, D. H., Adams, J. K., and Davis, C. F., 1964, Water-table, surface-drainage, and engi-
neering soils map of the Georgetown Quadrangle, Delaware: U. S. Geological Survey
Hydrologic Investigations Atlas, HA-107.

Boggess, D. H., Adams, J. K., and Davis, C. F., 1964, Water-table, surface-drainage, and engi-
neering soils map of the Rehoboth Beach area, Delaware: U. S. Geological Survey
Hydrologic Investigations Atlas, HA-109.

Boggess, D. H., Davis, C. F., and Coskery, 0. J., 1965, Water-table, surface-drainage, and engi-
neering soils map of the Milford Quadrangle, Delaware: U. S. Geological Survey Hydrologic
Investigations Atlas, HA-133.

Boggess, D. H., Davis, C. F., and Coskery, 0. J., 1965, Water-table, surface-drainage, and engi-
neering soils map of the Burrsville area, Delaware: U. S. Geological Survey Hydrologic
Investigations Atlas, HA-135.

Boggess, D. H., Davis, C. F., and Coskery, 0. J., 1965, Water-table, surface-drainage, and engi-
neering soils map of the Wyoming Quadrangle, Delaware: U. S. Geological Survey
Hydrologic Investigations Atlas, HA-141.

Boggess, D. H., and Heidel, S. G., 1968, Water resources of the Salisbury area, Maryland:
Maryland Geological Survey Reports of Investigations 3, 69 p.

Boggess, D. H., and Rima, D. R., 1962, Experiments in water spreading at Newark,
Delaware, U. S. Geological Survey Water-Supply Paper 1594-B, p. B1-B15.

Davis, C. F., and Boggess, D. H., 1964, Water-table, surface-drainage, and engineering soils
map of the Maryland area, Delaware: U. S. Geological Survey Hydrologic Investigations
Atlas, HA-132.

Davis, C. F., and Boggess, D. H., 1964, Water-table, Surface-drainage, and engineering soils
map of the Harrington Quadrangle, Delaware: U. S. Geological Survey Hydrologic
Investigations Atlas, HA-136.

Davis, C. F., and Boggess, D. H., 1964, Water-table, surface-drainage, and engineering soils
map of the Mispillion River Quadrangle, Delaware: U. S. Geological Survey Hydrologic
Investigations Atlas, HA-137.

Davis, C. F., Boggess, D. H., and Coskery, 0. J., 1965, Water-table, surface drainage, and engi-
neering soils map of the Frederica area, Delaware: U.S. Geological Survey Hydrologic
Investigations Atlas, HA-140.







SPECIAL PUBLICATION NO. 49






FLORIDA GEOLOGICAL SURVEY


The Surficial Geology of Lee County and the Caloosahatchee Basin

Thomas M. Scott
Florida Geological Survey, 903 W. Tennessee St., Tallahassee, FL 32304-7700
And
Thomas M. Missimer
Missimer International, Inc., 8140 College Parkway, Suite 202, Fort Myers, FL 33919

ABSTRACT

Knowledge of the surficial geology is a processor to developing an understanding of the
regional hydrogeology. Surficial geologic mapping in Florida is problematic because of the low
relief and sand cover. The mapping effort in Lee County relied heavily on data from well cuttings
and cores due to the sparse occurrence of pits, quarries and natural outcrops. The authors have
spent many years visiting pits and quarries and working subsurface samples to develop an
understanding of the regional geologic framework. The accumulated database was utilized to
determine sand overburden thickness and the underlying stratigraphic units for creating the Lee
County geological map.
The geologic units mapped were the Tertiary Tamiami Formation (Tt), Tertiary-Quaternary
shell units (Tqsu includes Caloosahatchee, Bermont, and Fort Thompson Formations of previ-
ous usage) and Quaternary (Holocene) coastal and estuarine sediments (Qh). Less than 20 feet
of undifferentiated sands occurred within the map area.


INTRODUCTION

Geological maps provide an important tool for developing an understanding of geological
history and natural resources. Knowledge of the regional surficial and near-surface geology is a
necessary prerequisite to beginning to understand hydrogeology. The type and distribution of
surficial and near-surface sediments has a direct bearing on the occurrence of surface water and
the recharge of groundwater.
Vernon and Puri (1964) produced the last geological map by the Florida Geological Survey
(FGS). Brooks (1982) published an independent version of the State geological map. Both
maps required updating and revision. In the late 1980s, the FGS began an effort to create an
updated and revised State geological map. In 1991, the mapping program focus changed toward
the development of county geological maps for a statewide radon hazard analysis investigation.
The maps created for this investigation formed the basis for the new State geological map.
Florida is the only state in the United States that lies entirely within a coastal plain province.
With the highest elevation in the State of just 345 feet, relief is generally limited and few outcrops
exist. The low relief of the southwestern Florida landscape yields little information to geologists
from natural exposures making geological mapping problematic. As a result, the mapping effort
in Lee County and the Caloosahatchee Basin utilized information gathered from well cuttings and
cores (including a number of cores drilled by the FGS), quarries and pits, and limited natural out-
crops. In developing a concept of the regional geologic framework, the authors have spent many
years examining exposed sections and spoil piles in pits and quarries in addition to analyzing
subsurface samples. The accumulated database was utilized in formulating the Lee County geo-
logic map (Figure 1).
Much of the Florida landscape is covered by a sand blanket of varying thickness. Mapping
the general surficial occurrence of the sands provides only limited information. As such, the con-






SPECIAL PUBLICATION NO. 49


vention was adopted of removing up to 20 feet of undifferentiated sands and mapping the under-
lying formations. In areas where the sand cover exceeded 20 feet in thickness, the occurrence
of sand was mapped. Within Lee County, no areas of more than 20 feet of undifferentiated sand
were identified. However, due to the nature of the database, sands thicker than 20 feet may
occur locally within the county.

GEOLOGY

The geologic units mapped in Lee County were the Tertiary Tamiami Formation (Tt), Tertiary-
Quaternary shell units (Qsu includes Caloosahatchee, Bermont and Fort Thompson formations
of previous usage) and Quaternary (Holocene) coastal and estuarine sediments (Qh).
The oldest formation shown on the Lee County geological map is the Pliocene Tamiami
Formation (Tt). The Tamiami Formation is a poorly defined lithostratigraphic unit containing a
wide range of mixed carbonate-siliciclastic lithologies and associated faunas (Missimer, 1992).
The Peace River Formation, Hawthorn Group, underlies the Tamiami Formation throughout the
county. The Tamiami Formation consists a mixture of variably sandy limestone, sands, and clays
containing varying percentages of phosphate grains. Fossils, including mollusks, echinoids and
corals, are commonly abundant in the Tamiami Formation. Fossil preservation varies from well
preserved to molds and casts of the original fossils.
Overlying the Tamiami Formation throughout much of Lee County are sediments mapped as
undifferentiated Tertiary/Quaternary (Plio-Pleistocene) shell-bearing units (Qsu). The
Caloosahatchee, Bermont and Fort Thompson formations of previous references are included
within the Qsu designation due to the primarily biostratigraphic nature of the units throughout
their areal extent (see Scott, 1992). Within portions of the map area, the Caloosahatchee and
Fort Thompson are lithologically separable. However, throughout much of the rest of southern
Florida, the units are lithologically indistinct. This unit consists of sand with subordinate lime-
stone and clay. Fossils, including mollusks and corals, are common, often abundant and preser-
vation is often excellent.
A quartz sand blanket (less than 20 feet thick) overlies Tt and Qsu throughout the county.
The sand is generally a fine to medium well sorted sand with no fossils. Along the coast, below
an altitude of approximately 5 feet msl, are sediments mapped as Holocene age sediments.
These sediments consist of quartz sand with a variable organic component and occasional peat
to muck deposits. The Holocene sediments include the beach ridge and dune sands.

REFERENCES

Brooks, H.K., 1982, Geologic Map of Florida: Center for Environmental and Natural Resources,
University of Florida.

Missimer, T.M., 1992, Stratigraphic relationships of sediment facies within the Tamiami Formation
of southwestern Florida: Proposed intraformational correlations; in Scott, T.M., and Allmon,
W.D., editors, The Plio-Pleistocene stratigraphy and Paleontology of southern Florida;
Florida Geological Survey Special Publication 36, p.63-92.

Scott, T. M., 1992, Coastal Plains stratigraphy: The dichotomy of biostratigraphy and lithos-
tratigraphy A philosophical approach to an old problem: in Scott, T.M., and Allmon, W. D.,
The Plio-Pleistocene stratigraphy and paleontology of southern Florida: Florida Geological
Survey Special Publication 36, p. 21-26.




















































Figure 1. Geologic Map of Lee County, Florida.






SPECIAL PUBLICATION NO. 49


T. Missimer and T. Scott, 1993, Geologic map of Lee County, Florida: Florida Geological Survey
Open File Map Series no. 61.

Vernon, R.O., and Puri, H.S., 1964 Geologic map of Florida, Florida Bureau of Geology Map
Series 18.






FLORIDA GEOLOGICAL SURVEY


LATE NEOGENE GEOLOGY OF NORTHWESTERN
LEE COUNTY, FLORIDA

Thomas M. Missimer
CDM/Missimer International, Inc., 8140 College Parkway, Suite 202, Fort Myers, Florida 33919

ABSTRACT

During the past 24 years, the Neogene geology of northwestern Lee County has been stud-
ied in numerous dewatered, shell pits. The thickness of the stratigraphic section studied is about
30 feet and contains three formations; the Tamiami, the Caloosahatchee, and the Fort
Thompson. The Tamiami Formation is a predominantly siliciclastic unit, equivalent to the Sand
Facies of Missimer (1992) with one occurrence of the Pinecrest Member (predominantly arago-
nitic mollusk shell) atAcline (Charlotte County). The Caloosahatchee Formation is a mixed car-
bonate and siliciclastic unit that is divided into three separate units by two intraformational uncon-
formities. The Fort Thompson Formation is a shell and quartz sand unit that contains two or
three stratigraphic units. From the base to the top of the formation, the relative percentage of
quartz sand increases from about 20 to 100% by volume.
The lithostratigraphy of the shallow Neogene sediments adjacent to Charlotte Harbor shows
that numerous transgressive and regressive sea level events produced a series of depositional
environment changes over the last 4 million years. The region was blanketed with a sheet of
quartz sand similar to the West Florida Shelf of today during the Pliocene as the Tamiami
Formation was deposited. During deposition of the Caloosahatchee Formation, the region was
subtropical with predominantly carbonate deposition and a coastal influx of quartz sand. Tropical
and subtropical mollusks and corals were abundant in the region producing an environment sim-
ilar to the present area between Cape Sable and Florida Bay. Deposition of the Fort Thompson
Formation brought a substantial change to the environment with an evolution to barrier island
and shallow nearshore deposition patterns similar to those observed today.

INTRODUCTION

Geological work in the northwestern area of Lee County and southern area of Charlotte
County began during the 1880's with a few early descriptive works. In his classic work on the
geology of the lower Florida West Coast, Heilprin (1887) wrote "Prior to our visit, the only portion
of the state that had been examined geologically, or on which a geological report had been pre-
pared, was the region lying north of a line running almost due northeast from the Manatee River,
just south of Tampa Bay, to the east coast. Below this all was conjectural, although the exis-
tence of certain limestones of undetermined age was hinted at, or even located, by a number or
causal observers (Tuomey, Conrad) who chanced to navigate some of the outer waters. Such
a limestone was reported by Tuomey to be found in Charlotte Harbor, but the exact locality of its
occurrence is not noted." Another scientist from the Wagner Free Institute of Philadelphia,
William H. Dall, was the first geologist to visit some of the late Neogene exposures in the
Charlotte Harbor area, immediately north of Lee County. Dall (1890-1903) described many of
the fossils found in the Pliocene and Pleistocene sediments of the region. During the 1930's,
several geologists examined exposures of the Caloosahatchee and Fort Thompson formations
at locations near Shell Creek, Alligator Creek, and in spoil piles adjacent to excavations. Wendall
C. Mansfield, Druid Wilson, Helen I. Tucker, and Axel A. Olsson visited several sites and col-
lected fossil mollusks. The paleontology of the fossil mollusks was described in a few publica-
tions (Tucker and Wilson, 1932a; Olsson and Harbison, 1953). In 1958, a shell pit located near






SPECIAL PUBLICATION NO. 49


Acline (Figure 1) was drained to make bed collections of the fossils and to describe the geology.
Druid Wilson of the U.S. Geological Survey and Stanley Olsen of the Florida Geological Survey
made these collections, but no work other than a fauna list (Tucker and Wilson, 1932b; also in
DuBar, 1962) was ever published. A detailed investigation of the Neogene geology of the
Charlotte Harbor area was published by DuBar (1962). DuBar described the geology at 13 sites
located adjacent to Charlotte Harbor and the geology adjacent to Shell Creek.
The geologic descriptions presented in this paper are considered to be preliminary and were
compiled at numerous locations in Lee and Charlotte counties over a period of 24 years by the
author and a number of associates. The author was first introduced to the geology of the
Charlotte Harbor area by F. Sternes McNeill, who was one of W. C. Mansfield's field assistants
in the 1930's. McNeill accompanied Durward Boggess and the author to several locations in the
area between 1972 and 1975.

NEOGENE STRATIGRAPHY

Introduction
A number of shell and sand pits have been excavated adjacent to the southeastern margin
of Charlotte Harbor in Charlotte and Lee counties and in the Cape Coral area of Lee County over
the past 40 years. Many of these excavations were dewatered to facilitate sediment
removal, which allowed detailed descriptions of the sediments to be made. Three Neogene
stratigraphic units were penetrated in most of the excavations, which include the Tamiami,
Caloosahatchee, and the Fort Thompson formations. Neogene time includes the Miocene to the
end of the Pleistocene or 23.8 to 0.01 Ma or a million years before present (Berggren et al.
1995). A general stratigraphic column is shown in Figure 2 using the stratigraphic terminology
of Missimer (1992) for the Tamiami Formation and the terminology of DuBar (1962) for the
Caloosahatchee and Fort Thompson formations. Although geologic information was collected at
each of the locations (sections measured and described) shown in Figure 1, detailed descrip-
tions of the geology are presented for only the Burnt Store Road North Pit (4), the Nelson Road
Pit (5), and the Chiquita Sand Pit (6).

Tamiami Formation
The Tamiami Formation is a Pliocene unit that contains a wide variety of members or facies
dependant upon the specific location studied. Missimer (1992) presented a stratigraphic corre-
lation of the various lithologic units found within the Tamiami Formation in Southwest Florida
(Figure 3). In the northern part of the study area, the exposures of the Tamiami Formation in
Alligator Creek are a sandy, calcareous clay with some phosphate and a few calcitic fossil frag-
ments (DuBar, 1958). The calcareous clay faces correlates to the tan clay and sand faces,
which occurs near the base of the formation (Figure 3). At all other locations, with the exception
of the Acline Pit, the section of the Tamiami Formation penetrated was either a sand and partially
indurated sandstone (Burnt Store Road North Pit), an unlithified quartz sand with solely calcitic
fossils interbedded with some limestone (Nelson Road Pit), or a partially indurated sand and bar-
nacle hash (Chiquita Sand Pit). All of these predominantly quartz sand units correlate lithos-
tratigraphically with the sand faces of Missimer (1992) shown in Figure 3.
The only exposure of the classical Pinecrest Member containing a wide diversity of mollus-
can species with preserved aragonitic shell is at the Acline Pit site. The Pinecrest Member of the
Tamiami Formation is the youngest member of the formation and does not occur as a continu-
ous stratigraphic unit in the area of Charlotte Harbor.





FLORIDA GEOLOGICAL SURVEY


Charlotte
Harbor



Gulfof
MeA'co


Acline Pit
Coral Rock Industries Pit
The Dirt Store Pit
Burnt Store Road Pit
Nelson Road Pit
Chiquita Sand Pit


N

k


SCALE
12 MILES
20 KILOMETERS


Figure 1. Map of Charlotte Harbor area showing the locations of pits studied in Lee and
Charlotte counties.
Caloosahatchee Formation
DuBar (1962) recognized five stratigraphic subdivisions of the Caloosahatchee Formation in
the Charlotte Harbor area (Figure 4). Although these subdivisions of the formation do occur, they
are rarely if ever all present at a single location or in the same stratigraphic position Stratigraphic
sections are commonly described in terms of sequence stratigraphy, in which a sequence is
defined as an unconformity-bounded stratal unit (Van Wagoner et al. 1990). A sequence is sub-
divided into parasequences, which are the building blocks of the sequence. A parasequence is
defined as Arelatively conformable successions of genetically related beds or bedsets bounded





SPECIAL PUBLICATION NO. 49


Age Formation Member

Upper
Fort Thompson Upper
Lower
Pleistocene Lower
F
E

Caloosahatchee
C
B
A
Pliocene
Pinecrest
Tamiami
Sand

Figure 2. General stratigraphic column showing the late Neogene units studied in the Charlotte
Harbor area.
by marine-flooding surfaces or their correlative surfaces@ (Van Wagoner et al. 1990). Based on
modern concepts of sequence stratigraphy, the Caloosahatchee Formation can probably be bro-
ken down into three different sequences or perhaps parasequences when viewed on a regional
basis. There are at least two distinctive breaks in the Caloosahatchee stratigraphic section,
marked by the occurrence of either a laminated crust and disconformity or the occurrence of a
freshwater limestone. These breaks correspond to either marine-flooding surfaces or to terres-
trial discontinuities as in the case of freshwater limestones. In the general stratigraphic column
show in Figure 4, the unconformities dividing the section occur at the top of Units C and E. It is
not possible to correlate regionally individual lithologic units within the formation, because of
spatial variability caused by depositional environment changes. However, the correlation of the
unconformities in stratigraphic order does allow correlation of time lines, which was the method
used by Perkins (1977) for correlating these stratigraphic units along the Florida East Coast.
The Caloosahatchee Formation at the Burnt Store Road North Pit contained four different










2.8


!5

Ld
O 0
4. <






4.2


Figure 3. Diagram showing the correlation of lithostratigraphic unit, defined facies, and formal members of the Tamiami Formation
(from Missimer, 1992).





SPECIAL PUBLICATION NO. 49


WHITE TO
GRAY SAND

YELLOW
TO BROWN
SAND


UNIT


UNIT D


UNIT C
UNIT E
- U NIT


Sand


Sandy marl


Sandy


Sandy marl
-- Conglom.
limestone
Calcareous
clay


Figure 4. General stratigraphic column showing the stratigraphic units studied by DuBar (1962)
in the Charlotte Harbor area with unit descriptions (DuBar, 1962).
lithic units (Figure 5). At this location there are only two stratigraphic breaks in the section
instead of the three found in the DuBar general section. A basal sequence or parasequence con-
tains two lithic units with an unlithified shell and sandy mud at the base and an indurated lime-
stone containing abundant shell at the top. The occurrence of freshwater fossils at the base of
the section could indicate the occurrence of another stratigraphic break, but the remaining sec-
tion does not occur. The uppermost unit consists of a basal, unlithified shell unit overlain by an
indurated limestone containing abundant aragonitic mollusk shells. The top of the limestone con-


UNIT E


* *


* *





FLORIDA GEOLOGICAL SURVEY


0




5



z o


I-
I

a 15




20


Z
0
0.

0
I

L-

U)UJ
85
00
.JI


*-- Sand, white

S -- Sandstone

Shell and sand

Shell
Unconformity
-4 -4--- 4 Limestone, shell
-- Shell

<4- Limestone, shelly

( .- Shell, muddy, sand
Freshwater fossils


Unconformity


<- Sandstone, limestone,
barnacles


*-- Water


Figure 5. Neogene stratigraphy of the Burnt Store Road North Pit in Lee County.
tains a laminated crust at some locations in the pit. Without some absolute time control, it is not
possible to correlate this section with the general DuBar typical section.
To the southeast of Charlotte Harbor, the occurrence of the Caloosahatchee Formation is
limited to only a few locations, because the formation has been removed by erosion or was not
deposited. The southernmost known occurrence of the formation on the Florida West Coast is
at the Nelson Road Pit, but only in the northeast corner of the pit (Figures 6 and 7). Despite the
relatively thin section of the formation at about 8 feet, nine different lithologies were found in
three sequences or parasequences. The basal unit is bounded with a disconformity at the base
and a freshwater limestone at the top. The lowest lithologic unit is an unlithified quartz sand and
shell. An indurated sandy limestone with shell lies conformably above the lowest unit and the
sequence is capped by a freshwater limestone. The middle sequence contains three different
lithologic units beginning at the base with a partially indurated limestone containing well-pre-





SPECIAL PUBLICATION NO. 49


UJ
LL
Z


a-


10




15


20




25


i
Sc

I-


-- Fill
-- Sand
s-- Sandstone


Sand and shell


Shell and sand

- Unconformity

Limestone
and shell

- Unconformity


- Unconformity


__ Muddy sand
and sandstone


Figure 6. Neogene stratigraphy of the Nelson Road Pit located in Lee County.
served aragonitic mollusk shells. This lithic unit is underlain by a coralline boundstone, contain-
ing about ten different species of corals. The sequence is capped by a highly altered limestone
containing predominantly sparite and no preserved aragonitic fossils. The top of the limestone
contains some solution depressions partially infilled with indurated laminated muds. The upper-
most sequence also contains three different lithologies. The base is an unlithified quartz sand





FLORIDA GEOLOGICAL SURVEY


Unconformity
S _Freshwater
13 .limestone

Limestone,
S r hard, indurated

15 Sand and shell

wI- Discontinuity
LI Limestone,
Ssparite
17 r .. .* Coralline
I" boundstone
I- 4-- Limestone, shell
S. .Freshwater

19 0 ,.. limestone
1 0J Limestone, sandy,
shelly

L < Sand and shell
21 Unconformity



Figure 7. Detailed stratigraphy of the Caloosahatchee Formation at the Nelson Road Pit in Lee
County.

and shell. It is topped by a hard, indurated limestone containing preserved aragonitic shell. The
sequence is capped with a freshwater limestone with some preserved laminations at the surface.
The Nelson Road Pit is the only known location in the region that contains all three sequences
described by DuBar (compare Figure 7 to 4).
No Caloosahatchee Formation sediments were found in the Chiquita Sand Pit located east
of the Nelson Road Pit. Specifically defined Caloosahatchee Formation sediments have not
been identified at any other location to the south in Lee or Collier counties.






SPECIAL PUBLICATION NO. 49


Fort Thompson Formation
The Fort Thompson Formation was originally described as a predominantly carbonate unit
based on outcrops located along the Caloosahatchee River and the carbonate shell deposits
found in a number of pits in South Florida (Dall, 1890-1903; DuBar, 1958). After DuBar (1962)
studied the stratigraphy of the Fort Thompson Formation in the Charlotte Harbor area and north-
western Lee County, the definition of the Fort Thompson Formation was forced to include pre-
dominantly siliciclastic and mixed carbonate and siliciclastic sediments. DuBar (1962) recog-
nized two separate quartz sand units within the formation in the Charlotte Harbor area, but did
not formally separate them.
Based on the stratigraphic sections described in the pits along Charlotte Harbor, there are
two or three different stratigraphic units within the Fort Thompson Formation in this region.
These units may represent individual sequences related to two separate sea level events or may
be a single sequence containing a discontinuity. The uppermost unit, above a laminated crust
representing an unconformity is problematical and may represent a very late sea-level deposit
or may be an erosional deposit related to soil development.
At the Burnt Store Road North Pit, the Fort Thompson Formation is clearly divided into three
different stratigraphic units (Figure 5). At the base of the formation, there is a shell bed averag-
ing about 12 inches in thickness. This unit is predominantly aragonitic shell with a minor amount
of quartz sand. The overlying unit consists of a shell and sand bed about 5 feet thick capped
by a laminated sandstone. The uppermost unit is a quartz sand containing little on no carbon-
ate and is sometimes laminated.
The Fort Thompson Formation section at the Nelson Road Pit is quite similar to the Burnt
Store Road North Pit (Figure 6). The section consists of three stratigraphic units. The lowest
unit is a shell and sand bed containing aragonitic shell, quartz sand, and some mud. The mid-
dle unit is a sand and shell bed capped by a laminated sandstone. Quartz sand is the predom-
inant component of the middle unit with up to 70% by volume. About 60 cm of quartz sand over-
lies the laminated crust. The uppermost quartz sand unit contains little or no carbonate.
There is again a clear similarity between the Fort Thompson Formation stratigraphy at the
Chiquita Sand Pit and the pits described (Figure 8). There are three stratigraphic units with the
lowest unit being a shell and quartz sand with a minor quantity of mud. The middle unit is pre-
dominantly quartz sand with 10 to 20% shell and no mud and is capped by a laminated sand-
stone crust. About 2.5 feet of sand occurs as the uppermost unit, which contains a typical soil
profile.

Age of the Neogene Stratigraphic Units
The most recent data available on the age of the Neogene formations discussed in this
paper was collected from Florida Geological Survey core W-16242, located at South Seas
Plantation on Captiva Island east of pit sites (Missimer, 1997). Based on this work, the estimat-
ed age ranges using the time scale of Berggren et al. (1995) for the formations discussed are:
Tamiami Formation, 4.29 to 2.15 Ma; Caloosahatchee Formation, 2.14 or 1.77 to 0.6 Ma; and
Fort Thompson Formation, 0.6 to 0.12 Ma. The Pinecrest Member of the Tamiami Formation has
an age range of 3.22 to 2.15 Ma in this core. These estimated age ranges for the formations are
likely to be similar for the sections discussed based on the close proximity of the Captive Island
core to the pit locations.

DISCUSSION

Study of the Neogene geology of the Charlotte Harbor area indicates that there is consid-
erable spatial variability in the lithologic units constituting the Tamiami, Caloosahatchee and Fort





FLORIDA GEOLOGICAL SURVEY


Thompson formations. Conventional lithostratigraphic correlation is not possible, but mapping
of regional disconformities does allow correlation of time-equivalent units because of the
relatively flat relief of the South Florida Platform (Perkins 1977).
At nearly every location studied, the Tamiami Formation is predominantly a siliciclastic unit
consisting of quartz sand with calcitic shell or slightly cemented quartz sand. The described
lithologic unit is equivalent to the Sand Facies of Missimer (1992). The only location containing
any section of the Pinecrest Member is the Acline Pit, which is further evidence that the Pinecrest
Member is not a regionally mappable stratigraphic unit.
There are two disconformities within the Caloosahatchee Formation that divide it into three
sequences or parasequences. It is likely that each of the three units found represent a single
sea-level event based on the generally shoaling-upward nature of the sediments (note the depth


I-




LU


a


5




10


15




20


i


I-


- Sand, white, brown

-. Sandstone,
laminated


Sand, with shell
(15-20%), white


Shell, with sand
(30-40%), gray,
slightly muddy


Sandstone,
barnacles,
Ostrea


Figure 8. Neogene stratigraphy of the Chiquita Sand Pit in Lee County.






SPECIAL PUBLICATION NO. 49


of water in which the sediments were deposited becomes progressively shallower). Based on
recent age-dating work by Missimer (1997), the uppermost sequence is likely a Pleistocene sea-
level event while the lower two sequences are Pliocene events. Similar
ages for these sediments was determined by Jones et al. (1991) in Sarasota County.
Three different lithologic units were found within the Fort Thompson Formation. These units
show remarkable uniformity in composition. The units become progressively more siliciclastic
from bottom to top of the formation.

CONCLUSIONS

Over the last 4 million years, the geological character of the Charlotte Harbor region has
changed considerably. When the Tamiami Formation was being deposited, the area was pre-
dominantly a sandy, shallow marine environment, similar to the current conditions on the West
Florida shelf with deeper water (Meeder 1987). Based on the work of Meeder (1987), the cli-
mate of the region was subtropical, but perhaps cooler than present. During the later period of
Tamiami Formation deposition, massive shell beds of the Pinecrest Member were deposited in
isolated areas, such as Acline. Deposition of these shell beds is believed to be the result of
storms and processes occurring in shallow coastal waters (Allmon 1993).
During deposition of the Caloosahatchee Formation, there were three sea level events that
showed a rise and then a succeeding recession. Based on the occurrence of tropical and sub-
tropical mollusks and corals in the sediments, and oxygen isotope data collected on core W-
16242 located on Captiva Island (Missimer 1997), the region was perhaps warmer than during
deposition of the Tamiami Formation and showed a greater diversity of depositional environ-
ments ranging from shallow shelf or ramp to open bay, to lagoonal or embayment. The deposi-
tional environments are similar to those currently existing from Cape Sable south to Florida Bay
and to the west on the shelf. Not as much quartz sand was entering the marine environment
during this time, which may indicate that sea level was slightly higher than today.
Sediments of the Fort Thompson Formation show characteristics similar to those currently
being deposited as barrier islands, such as Sanibel Island. The general climatic conditions were
similar to today based on the mollusk assemblage. Large quantities of quartz sand were being
deposited with the mollusks. The environment probably looked similar to today with the shell and
sand deposits occurring along the coast and on the shallow shelf with the muddier sediments
being deposited in shallow embayments, such as the upper part of Charlotte Harbor and the inte-
rior of the Caloosahatchee River embayment.

RESEARCH NEEDS

Although numerous geologic, paleontologic, and seismic reflection studies have been made
of the region in and around Charlotte Harbor, no significant synthesis of the work has been
accomplished. It would be extremely useful to correlate the seismic reflection data collected by
Evans et al. (1989) and Evans and Hine (1991) with the lithostratigraphy in this paper and the
paleontological studies of the past to produce a depositional model of the region through time.

ACKNOWLEDGMENTS

I thank the many geologists that accompanied me during field mapping and sample collec-
tion. This group includes: F. Sternes McNeill (deceased), Durward H. Boggess (deceased),
Thomas M. Scott, Roger Portall, Victor Zullo (deceased), Bill Harris, and many others. Charles
Walker reviewed this manuscript and added helpful comments.






FLORIDA GEOLOGICAL SURVEY


REFERENCES

Berggren, W. A., D. V. Kent, C. C. Swisher, III, and M. P. Aubry. 1995. A revised Cenozoic
geochronology and chronostratigraphy. Pp. 129-212 in: Berggren, W. A., D. V. Kent, M. P.
Aubry, and J. Hardenbol, editors, Geochronology, time scales and global stratigraphic cor-
relation, Soc. Econ. Paleont. Mineral. Spec. Pub. No. 54.

Dall, W. H. 1890-1903. Contributions to the Tertiary fauna of Florida with special reference to the
Miocene Silex beds of Tampa and the Pliocene beds of the Caloosahatchee River. Wagner
Free Institute Science Trans., v. 3, 6 parts, 1654 pp.

DuBar, J. R. 1958. Stratigraphy and paleontology of the late Neogene strata of the
Caloosahatchee River area of southern Florida. Florida Geological Survey Bull. 40, 267pp.

DuBar, J. R. 1962. Neogene biostratigraphy of the Charlotte Harbor area in Southwestern
Florida. Florida Geological Survey Geological Bulletin No. 43, 83pp.

Evans, M.W. and A.C. Hine. 1991. Late Neogene sequence stratigraphy of a carbonate-silici-
clastic transition: Southwest Florida: Geol. Soc. Am. Bull., 103: 679-699.

Heilprin, A. 1887. Explorations on the West Coast of Florida and in the Okeechobee Wilderness.
Wagner Free Institute of Philadelphia, 134p.

Jones, D.S., B.J. MacFadden, S.D. Webb, P.A. Mueller, D.A. Hoddell, and T.M. Cronin. 1991.
Intergrated geochronology of a classic Pliocene fossil site in Florida: Linking marine and ter-
restrial biochronologies: Jour. of Geology, v. 99, p. 637-648.

Meeder, J.F. 1987. The paleoecology, petrology and depositional model of the Pliocene Tamiami
Formation, Southwest Florida (with special reference to corals and reef development): Ph.D.
dissertation, Univ. of Miami, Coral Gables, Florida, 749 pp.

Missimer, T. M. 1992. Stratigraphic relationships of sediment facies within the Tamiami
Formation of Southwest Florida: Proposed intraformational correlations. Pp. 63-92 in Scott,
T. M., and W. A. Allmon, eds., The Plio-Pleistocene Stratigraphy and Paleontology of
Southern Florida. Florida Geological Survey Special Publication No. 36.

Missimer, T. M. 1993. Pliocene stratigraphy of southern Florida: Unresolved issues of facies cor-
relation in time. Pp. 33-42 in Zullo, V. A., W. B. Harris, T. M. Scott, and R. W Portell, The
Neogene of Florida and Adjacent Regions, Proceedings of the Third Bald Head Island
Conference on Coastal Plains Geology. Florida Geological Survey Special Publication 37.

Missimer, T. M. 1997. Late Oligocene to Pliocene evolution of the central portion of the South
Florida Platform: Mixing of siliciclastic and carbonate sediments. Unpublished Ph.D. dis-
sertation, University of Miami, Coral Gables, Florida, 2 volumes, 1001 pp.

Olsson, A. A., and A. Harbison. 1953. Pliocene Mollusca of Southern Florida. Acad. of Natural
Science, Philadelphia, Mon. 8, 457pp.






SPECIAL PUBLICATION NO. 49


Perkins, R. D. 1977. Depositional framework of Pleistocene rocks in South Florida. Pp.131-198
in Enos, P., and R. D. Perkins, Quaternary sedimentation in South Florida. Geological
Society of America Memoir 147.

Tucker, H. I., and D. Wilson. 1932a. Some new and otherwise interesting fossils from the Florida
Tertiary. Bull. Am. Paleontology 18:39-82.

Tucker, H.I. and D. Wilson. 1932b. A list of species from Acline, Florida: Indiana Acad. Sci. Proc.,
v. 41, p. 357.

Van Wagoner, J.C., R.M. Mitchum, K.M. Campion and V.D. Rahmanian. 1990. Siliciclastic
sequence stratigraphy in well logs, cores and outcrops: Concepts for high-resolution corre-
lation of time and faces: AAPG Methods in Exploration Series No. 7, Am. Assoc. of
Petroleum Geologists, Tulsa, Okla., 55 pp.






SPECIAL PUBLICATION NO. 49


SEQUENCE STRATIGRAPHY OF A SOUTH FLORIDA CARBONATE RAMP AND
BOUNDING SILICICLASTICS (LATE MIOCENE-PLIOCENE)

Kevin J. Cunningham1, David Bukry2, Tokiyuki Sato3, John A. Barron2,
Laura A. Guertin4, and Ronald S. Reese1
1. U.S. Geological Survey, 9100 N.W. 36th Street, Suite 107, Miami, FL 33178
2. U.S. Geological Survey, 345 Middlefield Road, Menlo Park, CA 94025
3. Institute of Applied Earth Sciences, Mining College, Akita University, Tegata-Gakuencho 1-1, Akita, 010, Japan
4. Mary Washington College, Fredericksburg, VA 22401


ABSTRACT

In southern peninsular Florida, a late-early to early-late Pliocene carbonate ramp (Ochopee
Limestone Member of the Tamiami Formation) is sandwiched between underlying marine silici-
clastics of the late Miocene to early Pliocene Peace River Formation and an overlying late
Pliocene unnamed sand. At least three depositional sequences (DS1, DS2, and DS3), of which
two contain condensed sections, are recognized in the Peace River Formation; an additional
depositional sequence (DS4) is proposed to include the Ochopee Limestone.
Established chronologies and new biostratigraphic results indicate that the Tortonian and
Zanclean ages bracket the Peace River Formation. Depositional sequence 1 (DS1) prograded
across the present-day peninsular portion of the Florida Platform during the Tortonian age and
laps out near the southern margin of the peninsula. During the latest Tortonian and Messinian
ages, progradation of DS2 overstepped the southern lap out of DS1 and extended at least as far
as the Florida Keys. Deposition of DS2 ended, at the latest, near the Miocene-Pliocene bound-
ary. Siliciclastic supply was reduced during early Pliocene deposition of DS3, which is absent in
southernmost peninsular Florida. This reduction in supply of siliciclastics was followed by aggra-
dational accumulation of heterozoan temperate carbonate sediments on a widespread carbon-
ate ramp that includes the Ochopee Limestone. The Ochopee Limestone was deposited during
eustatic cycle TB3.6 and ended in the late Pliocene with basinward lap out near the southern
margin of the Florida peninsula. The Ochopee Limestone ramp was buried with a late Pliocene
resumption of southward influx of siliciclastics (unnamed sand and Long Key Formation) that
extended south beyond the middle and upper Florida Keys.

INTRODUCTION

Until the early 1990's, stratigraphic investigations of Miocene-Pliocene siliciclastics and car-
bonates beneath southern Florida focused on lithostratigraphy (Peck et al., 1979; Wedderburn
et al., 1982; Peacock, 1983; Missimer, 1984; Knapp et al., 1986; Scott, 1988; Smith and Adams,
1988; Missimer, 1992). Recently, sequence stratigraphy has contributed to conceptualizing a
more accurate spatial and temporal framework of the Miocene-Pliocene stratigraphic framework
of southern Florida (Evans and Hine, 1991; Warzeski et al., 1996; Missimer, 1997; Cunningham
et al., 1998; Guertin et al., 1999; Missimer, 1999; Guertin et al., 2000). This developing
sequence-stratigraphic framework for southern Florida is the result of integrating lithostratigra-
phy, micropaleontology, magnetostratigraphy, strontium-isotope chemostratigraphy, and seismic
stratigraphy along with delineating unconformities that bound depositional sequences (Missimer,
1997; Weedman et al., 1997; Cunningham et al., 1998; Edwards et al., 1998; Guertin, 1998;
Missimer, 1999; Weedman et al., 1999). The purpose of this study is to integrate new lithologic
and paleontologic data with established subsurface data to more accu-rately describe the region-
al lithostratigraphic and sequence-stratigraphic framework of the Miocene-Pliocene siliciclastics






FLORIDA GEOLOGICAL SURVEY


and carbonates of southern Florida. Correlating these data will improve understanding of the
regional stratigraphic framework and constrain time boundaries for depositional sequences.


METHODS

A total of 89 coreholes and cuttings from 18 test wells were used to map lithostratigraphic
boundaries and to develop facies associations and sequence stratigraphy (Fig. 1). The cuttings
were described using a binocular microscope. Descriptions of the cores are from Causaras
(1985), Causaras (1987), Fish (1988), Fish and Stewart (1991), McNeill et al. (1996), Missimer
(1997), Weedman et al. (1997), Cunningham et al., (1998), Edwards et al., (1998), Guertin
(1998), Weedman et al. (1999), Reese and Cunningham (2000, in press), and from the data
archives of the Florida Geological Survey and U.S. Geological Survey.
Co-authors David Bukry and Tokiyuki Sato identified coccolith taxonomy, and John Barron
determined diatom taxonomy. Bukry and Barron conducted identifications by standard U.S.
Geological Survey methods. Sato identified coccoliths for each sample by counting 200 nanno-
fossil specimens for quantitative analysis. The terms abundant (greater than 32 percent of spec-
imens in total assemblage), common (32 to 8 percent of specimens in total assemblage), rare
(less than 8 percent of specimens in total assem-blage) and present (found but not counted)
were used to describe quantitatively coccolith populations defined by Sato. Coccolith taxomony
has been assigned to the biostratigraphic zones of Okada and Bukry (1980) as calibrated to the
coccolith datums of ODP Leg 171B from the Blake Nose east of northern Florida (Shipboard
Scientific Party, 1998) with normalized modifications from Bukry (1991).
Co-author Laura Guertin identified benthic foraminifera at the genus level using data from
Bock et al. (1971), Poag (1981), and Jones (1994). Paleoenvironmental interpretations are
based on grouping of individual benthic foraminiferal associations and species into the broad
depth categories of inner and outer shelf, defined as mean sea level to an approximate water
depth of about 305 feet and from about 305 to 610 feet, respectively (Murray, 1991). Ages are
reported in accordance with the integrated magnetobiochronologic Cenozoic time scale of
Berggren et al. (1995).

CARBONATE RAMP AND BOUNDING SILICICLASTICS
TEMPORAL AND SPATIAL BOUNDARIES

Lithologic units of primary interest in this study, from oldest to youngest, are the Peace River
Formation of the Hawthorn Group, Ochopee Limestone Member of the Tamiami Formation, and
an unnamed sand member (Fig. 2). Facies associations pre-sented for the Peace River
Formation, Ochopee Limestone, and unnamed sand are based on examination of cores and on
existing descriptions within the study areas outlined in Figure 1.

Peace River Formation
Lithostratigraphy
Three depositional sequences (DS1, DS2, and DS3) are newly defined on a regional scale
within the Peace River Formation (Fig. 2). Although interpreted to be depositional sequences,
DS3 actually may be a parasequence. Much of the lithofacies analysis completed by Reese and
Cunningham (2000, in press) for southeastern Florida was limited mostly to DS2 and DS3.
Depositional sequence 1 (DS1) was characterized primarily by Weedman et al. (1997) and
Edwards et al. (1998). Five lithofacies have been identified by Reese and Cunningham (2000, in
press) for the upper part of the Peace River Formation in an area shown in Figure 1: (1) diatoma-








SPECIAL PUBLICATION NO. 49


0 REVERSE-AIR CORE
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Figure 1. Location map of test wells used in this study. Data from this study, Florida Geological Survey lithologic data base,
Causaras (1985, Causaras (1987), Fish (1988), Fish and Stewart (1991), McNeill et al. (1996), Missimer (1997), Weedman et
al. (1997), Edwards et al. (1998), Guertin (1998), Weedman et al. (1999), and Reese and Cunningham (2000, in press). The
dashed polygon shows the area used to develop faces associations for the upper part of the Peace River Formation (Table
1), and the stippled box indicates the area used for development of the faces associations of the Ochopee Limestone
Member of the Tamiami Formation and an unnamed sand (Tables 6 and 7). Locations of cross-sections A-A' (Fig. 5) and B-
B' (Fig. 6) are shown.


P-292


50 MILES







FLORIDA GEOLOGICAL SURVEY


SERIES


HOLOCENE






PLEISTOCENE











PLIOCENE


MIOCENE





OLIGOCENE


h


LITHOSTRAl1GRAPHY


LAKE FLIRT MARL.
UNDIFFIIERENTlATiED x
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0


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ARCADIA
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DS4


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In I = Inlcrval I
In 11 = laterval II
In III = [ntrval III



Figure 2. Correlation of chronostratigraphy, lithostratigraphy, and sequence stratigraphy recog-
nized in much of the study area. Modified from Olsson (1964), Hunter (1968), Miller (1990), Missimer
(1992), Brewster-Wingard et al. (1997), Missimer (1997), Cunningham et al. (1998), Guertin et al.
(1999), Missimer (1999), Weedman et al (1999), and Reese and Cunningham (2000, in press). The
Long Key Formation occurs in southernmost peninsular Florida and the Florida Keys
(Cunningham et al., 1998). DS1, DS2, DS3, and DS4 are depositional sequences, and CS2 and CS3
are condensed sections. Intervals I, II, and III of Guertin et al. (1999) are integrated into the corre-
lation scheme.


-CS3


4-CS2






SPECIAL PUBLICATION NO. 49


AO AO


%,


\


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O Conltnuous core
A=Absent
A?=Absent?
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I I
25 60 KILOMETERS


Figure 3. Structure contour map of the top of the mudstone contained in condensed section 2
(CS2) within deposi-tional sequence 2 (DS2) of the Peace River Formation in southern Florida. The
dashed line shows the mapped limit of CS2. Structure contours show altitude in feet below sea
level of top of the mudstone.


A
a


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I


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FLORIDA GEOLOGICAL SURVEY


AO AO 0
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e A

A 0 2 50 MILES

2*A 81 0 25 50 IKLOMETER8

Figure 4. Structure contour map of the top of the mudstone contained in condensed section 3 (CS3) within
deposi-tional sequence 3 (DS3) of the Peace River Formation in southern Florida. Both mudstones mapped
on the southwest-ern and southeastern parts of Florida were deposited during the early Pliocene, possibly
synchronously, as suggested by dating from Missimer (1997) for the W-16523 corehole in Lee County and the
biochronology of the mudstones in Palm Beach and Martin Counties. Structure contours show altitude in feet
below sea level of top of the mudstone.






SPECIAL PUBLICATION NO. 49


ceous mudstone, (2) terrigenous mudstone, (3) clay-rich quartz sand, (4) quartz sand, and (5)
pelecypod-rich quartz sand or sandstone (Table 1).
The diatomaceous mudstone and terrigenous mudstone typically occur as a couplet with the
diatomaceous mudstone underlying the terrigenous mudstone. Two mudstone couplets were
identified as CS2 and CS3 (Fig. 2). Structure contour maps of the two condensed sections show
that the lower condensed section (CS2) extends over about 6,000 square miles of southeastern
Florida (Fig. 3); the upper condensed section (CS3) is considerably more limited in areal extent
(Fig. 4). The lower condensed section (CS2) thins and pinches out in a paleo-landward or west-
ern direction (Figs. 5 and 6). The paleo-sea-ward lap out of CS2 is near the southern margin and
probably near the southeastern margin of the Florida peninsula (Figs. 3 and 6). The updip lap
out of CS3 is in a paleo-seaward direction from the updip lap out of CS2, suggesting eastward
offlapping progradation of Peace River siliciclastics (Fig. 6).
Above the lower mudstone in much of the study area, the Peace River Formation is com-
posed, from bottom to top, of clay-rich quartz sand, quartz sand, and pelecypod-rich quartz sand
and sandstone (Table 1). Some of the clay-bearing facies of the Peace River Formation may
grade laterally into mainly quartz sand facies in the western part of the study area.

Sequence Stratigraphy
In developing a regional sequence stratigraphy, it is common practice to initially identify the
more easily recognized condensed sections of unconformity-bound depositional sequences
(Posamentier and James, 1993). In prior studies of the Peace River For-mation and equivalent
sediments in southern Florida, only bounding unconformities have been proposed (Missimer,
1997; Guertin, 1998; Guertin et al., 1999; Missimer, 1999).
In the proposed southern Florida sequence stratigraphy for this study, downdip portions of
some sequence boundaries are equivalent to the parasequence concept of shoaling-upward
cycles bounded by flooding surfaces (Van Wagoner et al., 1988) instead of unconformities. The
framework herein provides guidance for further investigation into recognition of unconformities
and a more precise definition of sequence boundaries. Additionally, two newly identified con-
densed sections of the Peace River Formation are placed into the established framework of
unconformities. A condensed section is a relatively thin marine stratigraphic unit composed of
pelagic to hemipelagic sediments that accumulated at very low sedimentation rates (Loutit et al.,
1988). Condensed sections are important for biostratigraphic dating, defining and correlating
depositional sequences, and reconstructing depositional environments (Loutit et al., 1988;
Posamentier and James, 1993). In much of the study area, the distinct lithology of the condensed
sections facilitates their recognition in the context of the proposed developing sequence stratig-
raphy.
The diatomaceous mudstone that forms the two condensed sections of the Peace River
Formation (Figs. 5 and 6) contains a greater concentration of planktic fossils than overlying ter-
rigenous mudstone, suggesting the upper surface of the diatomaceous mud-stone defines the
surface of maximum flooding within each couplet. The maximum flooding surface represents a
time of maximum flooding within a depositional sequence, and marks the change from a trans-
gressive systems tract to a highstand systems tract (Van Wagoner et al., 1988; Posamentier and
James, 1993).
Depositional sequence 1 (DS1) is a wedge-shaped deposit of quartz sand, sandstone, and
minor carbonate that thins toward the southern and eastern edges of the Florida peninsula. This
depositional sequence laps out north of the W-17273 corehole in Miami-Dade County toward the
southern edge of the Florida peninsula (Fig. 6). Downlap of internal strata onto the top of the
Arcadia Formation is suggested by correlations shown in Figure 5. The southern lap out thinning
toward the east and probable downlap to the east suggest progradation of a siliciclastic shelf








FLORIDA GEOLOGICAL SURVEY


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SPECIAL PUBLICATION NO. 49



Table 1. Lithofacies characteristics of the upper part of the Peace River Formation
for the area outlined in Figure 1.

[Visual estimation was made for porosity. Hydraulic conductivity was estimated by comparison of
corehole from Fish and Stewart (1991, table 6)]



Characteristic Lithologic description
Diatomaceous Mudstone Facies
Depositional textures Diatomaceous mudstone
Color Mainly yellowish-gray 5Y 7/2 and light-olive-gray 5Y 5/2
Grain size Mainly terrigenous clay and fine sand-size diatoms; minor silt-size quartz; local very fine sand-size quartz
and phos phate grains, and fish scales
Carbonate grains Local benthic foraminifers
Accessory grains Common quartz grains and local phosphate grains
Porosity Minor microporosity
Hydraulic conductivity Very low (less than 0.1 foot per day)
Terrigenous Mudstone Facies
Depositional textures Terrigenous mudstone and claystone
Color Mainly light-olive-gray 5Y 5/2, yellowish-gray 5Y 7/2, and olive-gray
5Y 4/1, 5Y 3/2
Grain size Mainly terrigenous clay; minor silt-size quartz; local very fine sand- to granule-size quartz grains and very
fine sand- to pebble-size phosphate grains
Carbonate grains Local benthic foraminifers and pelecypod fragments
Accessory grains Common quartz grains; local diatoms, phosphate grains, mica, fish scales, shark's teeth
Porosity Minor microporosity
Hydraulic conductivity Very low (less than or equal to 0.1 foot per day)
Clay-Rich Quartz Sand Facies
Depositional textures Terrigenous clay-rich sand
Color Mainly yellowish-gray 5Y 7/2 and 5Y 8/1, and light-gray-olive 5Y 6/1
Grain size Mainly very fine quartz grains; minor silt-size quartz grains and terrigenous mud; local micrite, fine sand-sizE
to small pebble-size quartz grains and very fine sand-size to pebble-size phosphate grains
Carbonate grains Local thin-shelled pelecypods, oysters, Turritella and benthic foraminifers
Accessory grains Common phosphate grains (trace to 40 percent); minor heavy minerals; trace mica
Porosity Mainly intergrain; local moldic; ranges from 5 to 20 percent
Hydraulic conductivity Mainly very low (less than 0.1 foot per day) to low (0.1 to 10 feet per day); ranges from very low (less than
0.1 foot per day) to moderate (10 to 100 feet per day)
Quartz Sand Facies
Depositional textures Quartz sand with less than 10 percent skeletal grain
Mainly yellowish-gray 5Y 8/1 and yellowish-gray 5Y 7/2; locally medium-dark-gray N4 to very light gray N8,
Color light- olive-gray 5Y 5/2, grayish-yellow-green 5GY 7/2, pale-olive 10Y 6/2, very pale orange 10YR 8/2,
and pale-yellow ish-brown 10YR 6/2
Grain size Mainly very fine to medium quartz sand; ranges from silt to granule size; carbonate grains range from silt to
pebble size; terrigenous clay
Carbonate grains Pelecypods (local Pecten and Chione), benthic foraminifers, echinoids, and undifferentiated skeletal grains
Accessory grains Trace to 30 percent phosphate and heavy mineral grains; local minor terrigenous clay; local trace mica;
trace to 1 percent plagioclase; trace microcline
Porosity Intergrain; ranges from 5 to 20 percent
Hydraulic conductivity Mainly low (0.1 to 10 feet per day) to moderate (10 to 100 feet per day); ranges from very low (less than 0.1
foot per day) to moderate (10 to 100 feet per day)
Pelecypod-Rich Quartz Sand or Sandstone Facies
Depositional textures Quartz sand matrix with pelecypod rudstone framework, or quartz sand supporting skeletal floatstone
Color Mainly yellowish-gray 5Y 8/1 and 5Y 7/2; locally light-gray N7 to white N9, light-olive-gray 5Y 5/2, light-olive
gray 5Y 6/1, and very pale orange 10YR 8/2
Grain size Mainly very fine to fine quartz sand; ranges from silt to very coarse quartz sand; carbonate grains range
from silt to cobble size; local terrigenous clay and lime mudstone
Carbonate grains Pelecypods (including Pecten and oysters), undifferentiated skeletal grains, gastropods (including
Turritella), bryo zoans, serpulids, and echinoids
Accessory grains Trace to 40 percent phosphate and heavy mineral grains; local minor terrigenous clay and lime mudstone;
local trace mica
Porosity Intergrain and moldic; ranges from 5 to 25 percent; local abundant pelecypod molds contribute to high
porosity
Hydraulic conductivity Mainly low (0.1 to 10 feet per day) to moderate (10 to 100 feet per day); ranges from very low (less than 0.1
foot per day) to high (100 to 1,000 feet per day)







FLORIDA GEOLOGICAL SURVEY


-r T. aI 4Kinimcc urifaLe
S I- irt oRCc.mnIcc surface

Figure 7. Correlation of the chronostratigraphy of a portion of the late Tertiary geomagnetic polarity time
scale (Berggren et al., 1995) and coccolith zonation. From ODP Leg 171B at the Blake Nose east of northern
Florida (Ship-board Scientific Party, 1998) with normalized additions of Subzones CN12aA, aB, and aC from
Bukry (1991), the eustatic curves of Haq et al. (1988), diatom datums from offshore California, and southern
Florida sequence stratigraphy.






FLORIDA GEOLOGICAL SURVEY


Table 2. Occurrence of stratigraphically important diatom taxa and the silicoflagellate
D. frugalis in wells W-9110, C-1142, C-1182, and W-17273.

[CS2, condensed section 2 of the Peace River Formation; CS3, condensed section 3 of the Peace River
Formation; <, less than the value. Genus: DF, Distephanus frugalis; HO, Hemidiscus ovalis; KA, Koizumia
adaroi; KT, K. tatsunokuchiensis; RF, Rhaphoneis fatula; TE, Thalassiosira eccentrica; TO, T oestrupii; TP,
T praeoestrupii]
Sample
depth Strati- Esti-
Well No. (feet Sample graphic Subepoch mated Genus present
below type unit age
sea level) (million
years
ago)
DF HO KA KT RF TE TO TP
W-9110 208-218 Cuttings CS-3 Early Pliocene <5.5 X X X X
238-248 Cuttings CS-3 Early Pliocene <5.5 X X X X X
C-1142 123.2 Core CS-2 Late Miocene 6.0- 5.5 X X X
C-1182 147.5 Core CS-2 Late Miocene 6.0-5.5 X X X
W-17273 410.0 Core CS-2 Late Miocene 6.5-5.5 X X X
430.0 Core CS-2 Late Miocene 6.5-5.5 X X X X
445.0 Core CS-2 Late Miocene 6.5- 5.5 X X X
455.0 Core CS-2 Late Miocene 6.5-5.5 X X X


toward the east and south (Figs. 5 and 6). A shelf-margin break is postulated to occur between
the W-17969 and W-17273 cores (Fig. 6).
The bottom of DS1 is delimited by a regional unconformity that separates the Peace River
Formation from the Arcadia Formation. This unconformity in southern Florida represents a hia-
tus of about 1.6 to 11.5 million years based mostly on strontium-isotope chemostratigraphy
(Guertin et al., 2000). An unconformity, with local evidence of subaerial exposure (discussed
later) defines the top of DS1 in the western part of the study area (Fig. 5). In the east and south-
east, the base of a condensed section (CS2) delineates the top of DS1 (Figs. 5 and 6). A
sequence stratigraphy produced by Missimer (1999) at the W-17115 corehole in Collier County
(Fig. 5) was linked to the sequence stratigraphy developed here, suggesting that DS1 is equiv-
alent to a supersequence defined within the lower Peace River Formation (Fig. 7) by Missimer
(1999).
Depositional sequences 2 and 3 (DS2 and DS3) contain coarsening upward siliciclastic
deposits defined by mudstone (CS2 and CS3) at the base that grades upward into mostly very
fine to fine quartz sand and sandstone (Figs. 5 and 6). Depositional sequence 2 (DS2) has a pro-
file in Figure 6 that thins landward, thickens as fill along the marginal slope of DS1 and thins sea-
ward in cross-section B-B' (Fig. 6). The profile in Figure 5 shows landward thinning of this unit in
a sheet like geometry. Most of the base of DS2 is delimited as the base of CS2 (Figs. 5 and 6).
Quartz sands in the W-17273 and GB2 core-holes (Fig. 6) form an early transgressive deposit
at the base of DS2 that is consistent with palynomorph data presented by Cunningham et al.
(1998). These sands and the diatomaceous mudstone of CS2 form the transgressive systems
tract of DS2.
Depositional sequence 2 (DS2) is probably equivalent to Interval I of the Long Key
Formation (Guertin et al., 1999) in the Florida Keys. This depositional sequence is bounded at
the top by an unconformity identified in southernmost Florida by Guertin et al. (1999) at the top
of Interval I of the Long Key Formation (Fig. 6). This unconformity is probably regional in extent






SPECIAL PUBLICATION NO. 49


and may merge to form an amalgamated unconformity with the top of DS1 (Fig. 5). The limits of
CS2 in Figure 3 and the cross sections shown in Figures 5 and 6 suggest that southward trans-
port of quartz sand to the Florida Keys during deposition of DS2 was mostly along the south-
eastern coast of Florida.
Depositional sequence 3 (DS3) is the youngest depositional sequence defined within the
Peace River Formation in the study area. The condensed section (CS3) of DS3 seems to be
restricted to an area in Martin and Palm Beach Counties and possibly an area mostly contained
in Lee County (Fig. 4). Depositional sequence 3 (DS3) contains CS3 as the basal unit in most of
the area, and is partly overlain by the Tamiami Formation (Fig. 5). The PB-1703 corehole (Fig.
1) contains an abrupt contact that may be an erosion/truncation surface and may define an
unconformity at the base of DS3 (Fig. 5). This potential unconformity may become conformable
down dip at the base of CS3 (Fig. 5). An unconformity has not been identified at the top of DS3
in Martin and Palm Beach Counties. An unconformity that bounds the upper Peace River
Formation of early Pliocene age in southwestern Florida (Missimer, 1997; 1999) is a deposition-
al sequence possibly equivalent to DS3 based on similar age (Fig. 7).

Micropaleontology
Taxonomic identification of diatoms, silicoflagellates and coccoliths from the Peace River
Formation are limited to the condensed sections contained in DS2 and DS3 (Figs. 5 and 6).
Micropaleontologic analyses focused on CS2 and CS3 because these mudstone units contain
microfossils that are useful for constructing a chronostratigraphy. Examination of samples for
benthic foraminifera was conducted on both mudstones and quartz sands of the Peace River
Formation. Both the benthic foraminifera and diatom populations were helpful in defining depo-
sitional environments.

Diatoms and silicoflagellates
Biostratigraphic analysis of diatoms was conducted on samples from the W-9110, C-1142,
C-1182, and W-17273 cores (Table 2). Diatoms from one sample of CS2 in the C-1142 corehole
suggest an age of 6.0 to 5.5 Ma (million years ago). Four diatomaceous mudstones samples of
CS2 in the W-17273 corehole and one sample from the C-1182 corehole contain very similar
diatom assemblages. A latest Miocene age older than 5.5 Ma is suggested for CS2 in both of
these cores based on the absence of Thalassiosira oestrupii, which first occurs at 5.5 Ma (Fig.
7). Other diatoms present in the assemblage (Paralia sulcata, Stephanopyxis sp., Delphineis sp.,
Actinoptychus sp., Actinocyclus octonarius, Thalassionema nitzschioides, Thalassiosira. eccen-
trica, Thalassiosira leptopus, Koizumia adaroi, and early forms of Koizumia tatsunokuchienis)
are consistent with an age younger than 6.5 Ma (Yanagisawa and Akiba, 1998; J.A. Barron, U.S.
Geological Survey, written commun., 2000).
The diatom analyses herein suggest that the age of CS2 can be constrained to 6.5 to 5.5
Ma. The presence of the silicoflagette Distephanus frugalis in the W-17273 core-hole supports
an age younger than 6.5 Ma (Barron, 1976). Alternatively, prior work by Cunningham et al. (1998)
reported the age of the diatomaceous mudstones (CS2) of the Peace River Formation in the W-
17273 corehole to range from 7.44 to 6.83 Ma (Fig. 6). This timeframe brackets the Tortonian-
Messinian boundary based on the presence of two cosmopolitan silicoflagellate species
Distephanus pseudofibula and Bachmannocena triodon (Cunningham et al., 1998). The 7.44 to
6.83 Ma range in age is consistent with the broader age range for biostratigraphic assignment of
coccoliths from CS2 (Zone CN9, perhaps only Zone CN9b) as shown in Figure 7.
The assemblages from the C-1142, C-1182, and W-17273 cores are composed pre-domi-
nantly of shelf-dwelling taxa. The diatomaceous mudstones in the C-1142 and C-1182 cores
record a transgressive event, upwelling of nutrients, or possibly both across a siliciclastic shelf






SPECIAL PUBLICATION NO. 49


Plate 1. Photographs of coccoliths from well W-9104. Photographs 1 to 16 are from a
sample interval of 318 to 328 feet below sea level. Photographs 17 to 20 are from a sam-
ple interval of 428 to 438 feet below sea level.

la,b. Coccolithus pelagicus (Wallich) Schiller: (la) cross-polarized light, and (1b) plane light.

2a,b. Calcidiscus leptoporus (Murray and Blackman) Loeblich and Tappan: (2a) cross-polar-
ized light, and (2b) plane light.

3a,b. Calcidiscus macintyrei (Bukry and Bramlette) Loeblich and Tappan: (3a) cross-polarized
light, and (3b) plane light.

4a,b. Reticulofenestra pseudoumbilica (Gartner) Gartner: (4a) cross-polarized light, and (4b)
plane light.

5a,b. Reticulofenestra pseudoumbilica (Gartner) Gartner: (5a) cross-polarized light, and (5b)
plane light.

6a,b. Sphenolithus abies Deflandre: (6a) cross-polarized light, and (6b) plane light.

7a,b. Ceratolithus armatus Muller: (7a) cross-polarized light, and (7b) plane light.

8a,b. Ceratolithus armatus Muller: (8a) cross-polarized light, and (8b) plane light.

9a,b. Ceratolithus armatus Muller: (9a) cross-polarized light, and (9b) plane light.

10a,b. Amaurolithus primus (Bukry and Percival) Gartner and bukry: (10a) cross-polarized
light, and (10b) plane light.

11. Discoaster brouweri Tan. Plane light.

12. Discoaster brouweri Tan. Plane light.

13. Discoaster pentaradiatus Tan. Plane light.

14. Discoaster pentaradiatus Tan. Plane light.

15. Discoaster surculus martini and Bramlette. Plane light.

16. Discoaster surculus Martini and Bramlette. Plane light.

17. Discoaster quinqueramus Gartner. Plane light.

18. Discoaster quinqueramus Gartner. Plane light.

19. Discoaster berggrenii Bukry. Plane light.

20. Discoaster berggrenii Bukry. Plane light.






FLORIDA GEOLOGICAL SURVEY


la 2a


4a 5a


9a l0a


) A


a&


41


Sb 'V

'It
SW
tee 4~
A


12


jp


. 1


10 u m


I

Me
V5f







FLORIDA GEOLOGICAL SURVEY


Table 3. Occurrence of coccolith taxa in cuttings from wells W-9104 and W-9114
[Stratigraphic position: CS2, condensed section 2 of the Peace River Formation; CS3, condensed section 3 of the
Peace River Formation; DS4, depositional sequence 4; BPR, base of Peace River Formation. Genus: C, Ceratolithus
rugosus; CP, Coccolithus pelagicus, D, Dictyococcites sp. (small); DB, Discoaster bellus; DBE, Discoaster berggrenii;
DBR, Discoaster brouweri; DP, Discoaster pentaradiatus; DQ, Discoaster quinqueramus; DS, Discoaster surculus;
DSP, Discoaster sp; DV, Discoaster variabilis; HN, Helicosphaera neogranulata; RP, Reticulofenestra pseudoumbili-
ca; RS, Reticulofenestra sp. (small); SA, Sphenolithus abies. Other abbreviations: A, abundant (greater than 32 per-
cent of specimens in total assemblage); C, common (32 to 8 percent of specimens in total assemblage); R, rare (less
than 8 percent of specimens in total assemblage; P, present (found but not counted); S, sparse or poorly preserved;
?, not determined]

Sample Nanno-
Well No. depth Strati- fossil Nanno
(feet graphic abun- fossil Genus present
below position dance zone
sea
level)
C CP D DB DBE DBR DP DQ DS DSP DV HN RP RS SA
C-1142 132 CS2 Barren --
W-9104* 205-215 DS4 ? CN12aA P P P P P
315-325 CS3 Abundant CN10b C A P P P C P P A P
325-335 CS2 Abundant CN9 P P P P P C A R
W-9110 208-218 CS3 ? CN9-12 S
238-248 CS3 ? CN10c-11 S S
308-318 CS2 Barren --
328-338 CS2 Barren --
408-418 BPR ? CN8 S S S
W-9114 253 263 CS3 Barren --
353-363 CS2 Rare CN9 P P P P P P P
W-17273 415 CS2 Barren --
425 CS2 Barren --
450 CS2 Barren --
460 CS2 Barren --
*The following genera also are present (found but not counted) in well W-9104 at a depth interval of 315 to 325 feet:
Acanthoica sp., Amaurolithus primus, Calcidiscus leptoporus, Calcidiscus macintyrei, Ceratolithus acutus, and
Ceratolithus armatus.

as indicated by the dominance of the shelf-dwelling taxa. The diatomaceous mudstones of the
W-17273 corehole (Fig. 6) also contain an abundance of shelf-dwelling taxa, but the stratigraphic
position of the taxa (Fig. 6) suggests deposition in a shelf-slope or toe-of-slope environment.
Environmental conditions such as currents, wave sweeping, or both could explain the transport
of shelf-dwelling taxa into this off-shelf environment.
Two samples of well cuttings from upper and lower parts of CS3 were collected for analysis
from well W-9110 (Fig. 5 and Table 2). The upper sample (Table 2, 208-218 feet below sea level)
is from the terrigenous mudstone faces (Table 1), and the lower sample (Table 2, 238-248 feet
below sea level) is from the diatomaceous mudstone facies (Table 1). A maximum flooding sur-
face separates the two samples (Fig. 5).
The sample from the upper part of CS3 in well W-9110 contains Paralia sulcata,
Actinocyclus octonarius, Actinoptychus senarius, Stephanopyxis sp., Koizumia tatasunokuchinis,
Thalassionema nitzschioides, Thalassiosira eccentrica, Thalassiosira leptopus, Thalassiosira
oestrupii, and Rhaphoneis fatula. An occurrence of T oestrupii suggests an age






FLORIDA GEOLOGICAL SURVEY


Table 4. Benthic foraminiferal genera and their distribution with depth in wells W-9104,
W-9114, C-1169, PB-1703 and C-1142
[Seven samples are not included in this table due to barren results. Stratigraphic position: DS2, depositional sequence
2 of the Peace River Formation; DS3, depositional sequence 3 of the Peace River Formation, US, unnamed sand.
Genus: A, Archaias; BO, Bolivina; BU, Bulimnella; C, Cancris; CA, Cassidulina; Cl, Cibicides; CR, Cribroelphidium; E,
Eponides; F, Fursenkoina; H, Hanzawaia; N, Nonion; NO, Nonionella; R, Rosalina]

Sample
Well No. depth Sample Strati-
(feet below type graphic Genus present
sea level) position
A__BO B0 U C CA CI CR E F H N NO R
W-9104 315 325 Cuttings DS3 X X
W-9114 253 263 Cuttings DS3 X
C-1169 163.0 Core DS2 X X X
179.0 Core DS2 X X X X X X X
P-1703 55.9 Core US X X X X X X
181.0 Core DS2 X
C-1142 131.5 Core DS2 X X X X
134.0 Core DS2 X __X X X X
139.0 Core DS2 X X X
144.0 Core DS2 X X X X X X X
149.0 Core DS2 X X X X X X X X X
154.0 Core DS2 X X X X X X X X X

Table 5. Ecological data for benthic foraminiferal genera identified in
the W-17614, PB-1703 and C-1142 coreholes
[Depth and environment information according to Murray (1991). Environment information for Criboelphidium accord-
ing to Bock et al. (1971). >, greater than the value]

Approximate
Genus depth Environment
(feet)

Archaias 0 66 Inner shelf
Bulimnella Lagoon, shelf, upper
bathyal
Cancris 164-492 Shelf
Cassidulina Shelf
Cibicides 0 >6,562 Lagoon, shelf-bathyal
Cribroelphidiu Florida; away from reef
m
Eponides Shelf-abyssal
Fursenkoina 0 3,937 Lagoon, shelf, upper
bathyal
Hanzawaia Inner shelf
Nonion 0 591 Shelf
Nonionella 33 3,281 Shelf
Rosalina 0 328 Lagoon, inner shelf







SPECIAL PUBLICATION NO. 49


) Reverse-dr core
* Drl cultings
O Conllnuous core
A=Absent
NS- No samples


-287


PS=Poor sornples
-- --Limit of Ochopee Limestone -
-- =Contour inftevl 50 ft. Datum is sea level.


A
'~ A
A


-"-200-- ,'
- /-
2/


A


50ILES


I I
2 o KL.WL-EIH


Figure 8. Structure contour map of the base of the Ochopee Limestone Member of the Tamiami
Formation. Structure contours show altitude in feet below sea level of base of the Ochopee
Limestone.


BROWARD


%
\


A 82






FLORIDA GEOLOGICAL SURVEY


younger than 5.5 Ma (Fig. 7). A rare presence of R. fatula suggests an early Pliocene age based
on comparison with occurrences in California (Dumont and Barron, 1995). An abundant pres-
ence of P sulcata possibly indicates that this is an outer shelf assemblage (Sancetta, 1981).
The lower sample from CS3 in well W-9110 contains an assemblage similar to the sample
from the upper portion but yields few Paralia sulcata. In addition to the taxa identified in the upper
sample, the lower sample includes the occurrence of Hemidiscus ovalis. The presence of
Thalassiosira oestrupii (Fig. 7) and H. ovalis indicates an early Pliocene age (Dumont and
Barron, 1995). Planktic diatoms are more common in the sam-ple from the lower part (diatoma-
ceous mudstone facies) of CS3 relative to the upper part of the sequence (terrigenous mudstone
facies). Relatively more planktic diatoms in the sample from the lower portion of CS3 is consis-
tent with greater interpreted water depth during deposition of the diatomaceous mudstone rela-
tive to the terrigenous mudstone above the maximum flooding surface. This surface is defined
by the boundary between the diatomaceous mudstone and terrigenous mudstone (Fig. 5).

Coccoliths
Samples were collected for analysis of coccoliths from wells C-1142, C-1182, W-9104, W-
9110, W-9114, and W-17273. These samples were taken from a terrigenous mudstone near the
base of the Peace River Formation and the two condensed sections (CS2 and CS3) of the Peace
River Formation (Figs. 5 and 6). A single sample from the terrigenous mudstone near the base
of the Peace River in well W-9110 (Fig. 5) contains abundant coccoliths that include Discoaster
bellus, Discoaster brouweri, Discoaster pre-pentaradiatus, and a questionable Discoaster bollii.
The assemblage of coccoliths probably belongs to Zone CN8 (Fig. 7), suggesting a Tortonian
age (Perch-Nielsen, 1985).
Coccolith and diatom occurrences suggest assignment of CS2 to Subzone CN9b, but could
be as old as Zone CN9 and as young as Subzone CN10a (Fig. 7). Coccoliths contained in eight
samples from CS2 in the C-1182 corehole suggest assignment of CS2 to Subzone CN9b (7.2-
5.6 Ma) based on the presence of Discoaster berggrenii, Discoaster quinqueramus, Discoaster
surculus, and Amaurolithus primus (Fig. 7). Reworking of coccoliths in samples from the C-1182
corehole was investigated, but is unlikely since no uniquely older or younger taxa were identi-
fied. Two samples from CS2 in the C-1142 corehole contain D. surculus and thus are no older
than Zone CN9. The upper biostratigraphic range of the C-1142 corehole sample is indefinite and
assigned to Zone CN9 or Subzone CN10a, but associated diatoms are late Miocene; therefore,
samples of CS2 from both the C-1182 and C-1142 cores suggest a late Miocene age no older
than Zone CN9 or probably Subzone CN9b (Figs. 5 and 6). The occurrence of the coccoliths D.
quinqueramus and D. berggrenii in one sample of CS2 collected from well W-9104 and another
of CS2 from well W-9114 suggests that CS2 in these wells belongs to Zone CN9 (Fig. 5 and
Table 3)
Combined diatom and coccolith data suggest assignment of CS3 to Subzone CN10b
through Zone CN11 or early Pliocene (Fig. 7). Coccoliths from CS3 in well W-9104 are charac-
terized by the presence of Ceratolithus acutus, Ceratolithus armatus, and Amaurolithus primus
(Plate 1 and Table 3). These taxa and especially the presence of C. acutus indicate assignment
of CS3 to Subzone CN10b (5.23-5.05 Ma) and an early Pliocene age (Fig. 7; Table 3). Two sam-
ples from CS3 in well W-9110 contain a trace to sparse presence of coccoliths including
Discoaster surculus, Ceratolithus rugosus, and Reticulofenestra pseudoumbilica. These coccol-
iths are consistent with assigning CS3 in well W-9110 to Subzones CN10c through Zone CN11
(5.05-3.83) and an early Pliocene age (Fig. 7).







SPECIAL PUBLICATION NO. 49


Table 6. Lithofacies characteristics of the Ochopee Limestone Member of the Tamiami
Formation for the area outlined in Figure 1

[Visual estimation was made for porosity. Hydraulic conductivity was estimated by comparison of core-
hole from Fish and Stewart (1991, table 6)]

Characteristic Lithologic description
Pelecypod Lime Rudstone or Floatstone Facies
Depositional textures Pelecypod lime rudstone or floatstone with quartz sand-rich lime packstone or
grainstone matrix
Color Mainly medium-light-gray N6 to very light gray N8 and yellowish-gray
5Y 8/1; locally yellowish-gray 5Y 7/2, black to medium-gray N5, white N9, and
very pale orange 10YR 8/2
Grain size Carbonate grains range from silt to cobble size; quartz sand mainly very fine to
fine, ranges from silt to very coarse
Carbonate grains Pelecypods (local oysters, Pecten, Chione, and Ostrea), undifferentiated skel
etal fragments, bryozoans, gastropods (local Turritella and Vermicularia),
benthic foraminifers, echinoids, serpulids, barnacles, planktic foraminifers,
ostracods, encrusting foraminifers, corals (hermatypic)
Accessory grains Common quartz sand and phosphate grains
Porosity Mainly intergrain and moldic; local intrafossil and boring; ranges from 5 to 25
percent
Hydraulic conductivity Mainly moderate (10 to 100 feet per day); ranges from low (0.1 to 10 feet per
day) to high (100 to 1,000 feet per day)
Pelecypod-Rich Quartz Sand or Sandstone Facies
Depositional textures Pelecypod-rich quartz sand and quartz-rich sandstone
Color Mainly yellowish-gray 5Y 8/1 and light-gray N7 to very light gray N6; locally
medium-dark-gray N4 to medium-light-gray N6, very pale orange 10YR 8/2,
light-olive-gray 5Y 6/1, yellowish-gray 5Y 7/2, and pale-yellowish-brown
10YR 6/2
Grain size Mainly very fine to fine quartz sand; ranges from silt to coarse quartz sand;
carbonate grains range from silt to cobble size
Carbonate grains Pelecypods (local oysters), undifferentiated skeletal fragments, gastropods,
echinoids, barnacles, serpulids, intraclasts, bryozoans, and encrusting fora
minifers
Accessory grains Absent to 5 percent phosphate and heavy mineral grains; local minor terrige
nous clay or lime mudstone matrix
Porosity Mainly intergrain with local moldic and intragrain; ranges from 10 to 20 per cent
Hydraulic conductivity Mainly low (0.1 to 10 feet per day) to moderate (10 to 100 feet per day); ranges
from low (0.1 to 10 feet per day) to moderate (10 to 100 feet per day)

Benthic foraminifera
Nine samples from CS2 were examined for benthic foraminifera. The benthic foraminifera of
CS2 belong to a marine shelf assemblage. Two samples from CS3 were examined. The assem-
blage present in CS3 is consistent with deposition on a marine shelf (Tables 4 and 5).

Ochopee Limestone Member of the Tamiami Formation

Lithostratigraphy and Depositional Environments
The Ochopee Limestone Member of the Tamiami Formation (Hunter, 1968; Meeder, 1987;
Missimer, 1992; Edwards et al., 1998; Weedman et al., 1999) includes a regionally extensive
limestone facies that can be mapped throughout much of the study area (Fig. 8). The Ochopee
Limestone has a sheet-like geometry that drapes over an unconformity at the top of the Peace
River Formation (Figs. 5 and 6). The Ochopee Limestone repre-sents a shift in sedimentation on
the Florida Platform from the retrogradation of DS3 within the Peace River Formation to aggra-
dation of the Ochopee Limestone. The Ochopee Limestone laps out near the southern margin of
the Florida peninsula. The lapout is probably coincident with the edge of the siliciclastic shelf






FLORIDA GEOLOGICAL SURVEY


containing DS2 of the Peace River Formation (Fig. 6).
Two lithofacies characterize the Ochopee Limestone in an area shown in Figure 1: (1) pele-
cypod lime rudstone or floatstone, and (2) pelecypod-rich quartz sand or sand-stone (Table 6).
The rudstone or floatstone facies is the most common lithofacies, whereas the sand or sand-
stone facies occurs only locally as thin to thick beds. The quartz sand is typically very fine to fine
grained, but locally may range from silt to very coarse sand. Skeletal carbonate grains of the
pelecypod lime rudstone or floatstone include fos-sils listed in Table 6.
The Ochopee Limestone was deposited in a carbonate ramp depositional system (Burchette
and Wright, 1992) during a reduction in siliciclastic supply to much of southern Florida. Criteria
to support the environmental interpretation include: (1) a low basin-ward depositional gradient of
less than 1 degree without a break in slope, as suggested by the upper and lower lithostrati-
graphic boundaries (Fig. 6); (2) widespread continuity of facies patterns; and (3) an almost com-
plete absence of internal exposure surfaces. In the study area, most of the Ochopee Limestone
was deposited in a mid-ramp depositional environment (Burchette and Wright, 1992). Evidence
for this depositional environment is indicated by the common occurrence of coarse-grained lime
rudstone that has a well washed, grain-dominated matrix (Lucia, 1995) and limemud-rich float-
stone (Table 6). The mixture of these grain-dominated and mud-dominated carbonates and the
lack of shallow-water faunal indicators suggest deposition below fair-weather wave base
(FWWB) but above storm wave base (SWB). The zone between FWWB and SWB defines the
mid-ramp depositional environment of Burchette and Wright (1992). Planktic foraminifera-rich
sandstone--similar to lithofacies of the Stock Island Formation of Cun-ningham et al. (1998)--
between depths of 275 and 336 feet below sea level in the W-17157 corehole may represent a
distal portion of the Ochopee ramp that accumulated in relatively deep sea water (Fig. 6).
Although the Ochopee Limestone contains quartz sand, the overwhelming abundance of car-
bonate grains represents a period of reduced quartz sand, silt, and mud to the southern Florida
Platform.
The benthic carbonate grains of the Ochopee Limestone represent a heterozoan particle
association, which James (1997) defined as a group of carbonate particles produced by light-
independent, benthic organisms that may or may not contain red calcareous algae. Red algae
were not observed in the Ochopee Limestone within the study area. The predominately hetero-
zoan assemblage of carbonate particles and an absence of shallow-marine particles, such as
ooids and green algae, is consistent with deposition in a mid-ramp depositional environment with
temperate bottom-water conditions. An almost complete absence of exposure surfaces within the
Ochopee Limestone is also consistent with mid-ramp deposition at water depths sufficient to min-
imize changes in water-bottom conditions during low-amplitude changes in relative sea level.

Sequence Stratigraphy
Depositional sequence 4 (DS4) is bounded at the base and top by regional subaerial uncon-
formities and is composed of the Ochopee Limestone (Figs. 5 and 6). The regional-scale
sequence boundary at the base of the Ochopee Limestone is evidenced by several established
unconformities reported between the top of the Peace River Formation and the base of the
Tamiami Formation in southwestern Florida (Edwards et al., 1998; Mis-simer, 1999). An uncon-
formity and sequence boundary reported by Missimer (1999) separating the Peace River
Formation and the Tamiami Formation in southwestern Florida is probably equivalent to the
unconformity separating Intervals I and II of the Long Key Formation (Fig. 6) in the Florida Keys
(Guertin et al., 1999). This unconformity may also be present as a hiatus identified by Guertin
(1998) in the W-17273 corehole of Miami-Dade County (Fig. 6). A subaerial exposure surface
occurs in the W-17394 corehole (Fig. 1) between the top of an unnamed quartz sand that is
equivalent to the top of the Peace River Formation (this study) and the Ochopee Limestone in







SPECIAL PUBLICATION NO. 49


PALM
BEACH
0-62


0 Reverse-ar core
Drill cuffings
O Continuous core
A=Absent
PS= Poor samples
NS=No samples
- - =LIMIT OF UNNAMED SAND
- =Contour Interval 50 ft. Datum Is sea


0 --210


0 25 s0MILES

D 25 50 KILOMETERS


Figure 9. Structure contour map of an unnamed sand that overlies the Ochopee Limestone
Member of the Tamiami Formation. Structure contours show altitude in feet below sea level of
base of the Pinecrest Sand.







FLORIDA GEOLOGICAL SURVEY


Table 7. Lithofacies characteristics of the unnamed sand for the area outlined in Figure 1
[Visual estimation was made for porosity. Hydraulic conductivity was estimated by comparison of corehole from Fish
and Stewart (1991, table 6)]

Characteristic Lithologic description
Quartz Sand Facies
Depositional textures Quartz sand with locally abundant fossils
Color Mainly yellowish-gray 5Y 8/1 and yellowish-gray 5Y 7/2; locally medium- gray
N5 to very light gray N8, very pale orange 10YR 8/2, light-olive-gray
5Y 6/1, light-olive-gray 5Y 5/2, grayish-yellow 5Y 8/4, grayish-orange
10YR 7/4, and dark-yellowish-orange 10 YR 6/6
Grain size Mainly very fine to fine quartz sand; ranges from silt to very coarse quartz sand;
carbonate grains range from silt to pebble size
Carbonate grains Pelecypods (local oysters), undifferentiated skeletal fragments, echinoids, ser
pulids, bryozoans, and benthic and planktic foraminifers
Accessory grains Trace to 3 percent phosphate and heavy mineral grains; local trace mica; local
minor terrigenous clay
Porosity Mainly intergrain and local intragrain, ranges from 5 to 25 percent
Hydraulic conductivity Mainly low (0.1 to 10 feet per day); ranges from very low (less than 0.1 foot per
day) to moderate (10 to 100 feet per day)
Pelecypod Lime Rudstone and Floatstone Facies
Depositional textures Pelecypod lime rudstone or floatstone with quartz sand-rich lime packstone and
grainstone matrix
Color Yellowish-gray 5Y 8/1, medium-gray N5 to light-gray N7, very pale orange
10YR 8/2, pale-yellowish-brown 10YR 6/2
Grain size Carbonate grains up to pebble size; quartz sand mainly very fine to fine and
ranges from silt to coarse size
Carbonate grains Pelecypods, undifferentiated skeletal fragments, gastropods, oysters, ser pulids,
bryozoans, cerithiids, and echinoids
Accessory grains Trace to 3 percent phosphate and heavy mineral grains
Porosity Mainly intergrain and moldic; local intragrain and shelter; ranges from 5 to 15
percent
Hydraulic conductivity Mainly low (0.1 to 10 feet per day); ranges from very low (less than 0.1 foot per
day) to moderate (10 to 100 feet per day)
Terrigenous Mudstone Facies
Depositional textures Silty terrigenous mudstone to quartz sand-rich terrigenous mudstone; locally
grades into terrigenous clay-rich lime mudstone
Color Light-olive-gray 5Y 5/2, light-olive-gray 5Y 6/1 and yellowish-gray 5Y 8/1;
locally pale-olive 10Y 6/2, light-olive-gray 5Y 6/1, dusky-yellow-green
5GY 5/2, and yellowish-gray 5Y 7/2
Grain size Mainly terrigenous clay; quartz grains range from silt to fine sand size; local
medium to coarse quartz sand
Carbonate grains Pelecypods (local oysters), benthic and planktic foraminifers, undifferentiated
skeletal fragments, and fish scales
Accessory grains Locally common quartz grains; trace to 1 percent phosphate grains; trace to 3
percent heavy mineral grains; local trace mica; trace plagioclase and micro
cline
Porosity Intergrain; less than or equal to 5 percent
Hydraulic conductivity Very low (less than 0.1 foot per day)


Collier County (Edwards et al., 1998). The unconformity recognized in southwestern Florida
(Missimer, 1999), in the W-17157 corehole (Guertin et al., 1999), in the W-17273 corehole
(Guertin, 1998), and in the W-17394 corehole (Edwards et al., 1998) all occur near the Miocene-
Pliocene boundary, suggesting that these unconformities may form a correlative sequence
bound-ary of regional scale (Fig. 6).
The top of the Ochopee Limestone is interpreted to represent a depositional sequence






SPECIAL PUBLICATION NO. 49


boundary. Typically, the contact between the top of the Ochopee Limestone and the unnamed
sand is abrupt. Several coreholes (Fig. 1; C-1181, C-1182, and G-3673) contain an abrupt con-
tact with core-scale microtopography, small dissolution cavities filled with quartz sand of the
unnamed sand, and local blackened crust. Blackened surfaces are reported to characterize the
tops of late Neogene unconformities bounding depositional sequences in southwestern Florida
(Evans and Hine, 1991). Analyses by x-ray diffraction indicate the blackened surfaces at the top
of the Ochopee Limestone do not contain a measurable amount of phosphorite. The absence of
phosphorite possibly suggests that the surface is not a submarine hardground and condensed
section (Loutit et al., 1988). The blackening could be due to fire above the surface during sub-
aerial exposure (Shinn and Lidz, 1988) or to darkened organic matter in soilstone crusts as noted
by Ward et al. (1970).
At the C-1178 corehole in Collier County (Fig. 1), the upper bounding surface of the
Ochopee Limestone contains strong evidence for subaerial exposure (Reese and Cunningham,
2000, in press). Reese and Cunningham (2000, in press) describe an exposure zone (30 feet
thick) bounding the top of the Ochopee Limestone that contains root molds lined with calcrete.
This unconformity is postulated to be equivalent to a lithofacies boundary in the Long Key
Formation at the W-17157 corehole in the Florida Keys. Along this boundary, there is an upward
shift from foraminifera-rich quartz sandstones--similar to lithofacies of the Stock Island Formation
of Cunningham et al. (1998)--to overlying quartz sandstone at a depth of 280 feet below sea level
(Guertin, 1998) as shown in Figure 6.

Micropaleontology
One sample of well cuttings was collected for analysis of coccoliths from well W-9104. This
sample was taken from a sandy mudstone at the base of the Tamiami Formation and possible
basal Ochopee Limestone at a depth interval of 205 to 215 feet below sea level (Fig. 5).
Coccoliths from the interval are assigned to the early Pliocene Subzone CN12aA (Fig. 7) identi-
fied by Bukry (1991). Coccoliths present in this interval include Discoaster brouweri, D. surculus,
D. variabilis, and Sphenolithus abies. Reticulofenestra pseudoumbilica is absent. This assem-
blage along with the absence of R. pseudoumbilica is characteristic of Subzone CN12aA (Bukry,
1991).

Unnamed Sand
Lithostratigraphy
An unnamed sand that overlies the Ochopee Limestone has been mapped in the study area
(Fig. 9). The stratigraphic relation to existing Pliocene-Pleistocene units, such as the Pinecrest
Member of the Tamiami Formation, has not been resolved. Future analysis of mollusks could
help to clarify relations, but Scott and Wingard (1995) have discussed the problems associated
with biostratigraphy and lithostratigraphy of the Plio-Pleistocene in southern Florida.
Three lithofacies have been identified within the unnamed sand for an area shown in Figure
1: (1) a quartz sand facies, (2) a pelecypod lime rudstone and floatstone facies, and (3) a ter-
rigenous mudstone facies (Table 7). The quartz sand facies is characteristic of most of the
unnamed sand. The terrigenous mudstone facies occurs mainly in the north-central part of the
study area outlined in Figure 1 where the facies typically occurs as one or two units within the
lower part of the unnamed sand. The pelecypod lime rud-stone is found only locally as discrete
beds within or near the top of the unnamed sand. Figure 6 shows that the unnamed sand is prob-
ably equivalent to much of Interval II and all of Interval III defined by Guertin et al. (1999) within
the Long Key Formation.
The unnamed sand ranges from 20 to 60 feet in thickness in most of the study area. The
unnamed sand is thickest (about 120 feet) in central and south-central Miami-Dade County. A






FLORIDA GEOLOGICAL SURVEY


structure contour map of the base of the unnamed sand (Fig. 9) shows that the unit pinches out
in the western portion of the Florida peninsula. In southern Miami-Dade County, the unnamed
sand merges with siliciclastics of the Long Key Formation as defined by Cunningham et al.
(1998) in the Florida Keys. The structure contour map at the base of the unnamed sand and the
cross sections shown in Figures 5 and 6 indicate that quartz sands of the unnamed sand were
transported southward mostly along the southeastern coast of Florida to the Long Key Formation
in the Florida Keys.

Sequence Stratigraphy
The sequence stratigraphy of the unnamed sand is more poorly defined than that of the
Ochopee Limestone and Peace River Formation. The unconformity and sequence boundary at
the top of the Ochopee Formation defines the base of the unnamed sand. Possibly a subaerial
unconformity at the base of the Pleistocene defined by Perkins (1977) bounds the top of the
unnamed sand. The unnamed sand is correlated to the middle and upper parts of Intervals II and
all of Interval III defined by Guertin et al. (1999) within the Long Key Formation (Fig. 6), sug-
gesting assignment to the early and late Pliocene. For the present study, however, assignment
of the Ochopee Limestone to Sub-zone CN12aA, at least in part, suggests that the unnamed
sand has a late Pliocene age (Fig. 7).

Micropaleontology
One sample from the terrigenous mudstone lithofacies of the unnamed sand from the PB-
1703 corehole in Palm Beach County was examined (Fig. 1 and Table 4). The assemblage pres-
ent is consistent with deposition on a marine shelf (Tables 4 and 5).

SUMMARY OF DEPOSITIONAL TIMING

Peace River Formation
Established chronologic data (Cunningham et al., 1998; Edwards et al., 1998; Guertin et al.,
1999; Missimer, 1999; Weedman et al., 1999) and the new biochronology of this study indicate
that the Tortonian and Zanclean ages bracket deposition of the Peace River Formation. These
chronologic data allow constraints to be placed on the ages of DS1, DS2, and DS3. In south-
western Florida, Missimer (1999) divided the Peace River Formation into one supersequence
(lower Peace River Formation) and one depositional sequence (upper Peace River Formation).
Deposition of the lower Peace River Formation of Missimer (1999) occurred between the inter-
vals of 11 and 8.5 Ma (Tortonian age) and deposition of the upper Peace River Formation of
Missimer (1999) was between 5.2 and 4.3 Ma (Zanclean age).
Biostratigraphic results presented herein indicate that terrigenous mudstones from the base
of DS1 of the Peace River Formation in Palm Beach County probably can be assigned to Zone
CN8 (Tortonian age). The boundaries of Zone CN8 are 9.4 and 8.6 Ma (Fig. 7).
Micropaleontologic results show that deposition of CS2 of the Peace River Formation occurred
from late Tortonian and Messinian age. Micropaleontologic results also suggest that CS2 is, at
most, 7.2 Ma and likely no younger than 5.6 Ma; however, results from Cunningham et al. (1999)
suggest an age ranging between 7.44 and 6.83 Ma.
Missimer (1999) reports a hiatus in deposition of the Peace River Formation between 8.5
and about 5.2 Ma in southwestern Florida--an interval in time that brackets deposition of CS2 in
southeastern Florida. Edwards et al. (1998) indicate that the unnamed for-mation in western
Collier County, which is equivalent to the Peace River Formation for the present study, ranges in
age from 9.5 to 5.7 Ma based on strontium-isotope chemostratigraphy, but biostratigraphic data
suggest it may be as young as Pliocene. Weedman et al. (1999) produced similar results for the






SPECIAL PUBLICATION NO. 49


Peace River Formation and unnamed formation in eastern Collier and northern Monroe
Counties, which are equivalent to the Peace River Formation for the study herein. Weedman et
al. (1999) report a late Miocene age for the Peace River Formation based on dinocysts and
strontium-isotope chemostratigraphy, and an age for the unnamed formation ranging between
6.9 and 4.6 Ma (late Miocene to Pliocene) based on strontium-isotope chemostratigraphy.
Coccolith data from the condensed section of DS3 and the age of overlying mudstones in well
W-9104 con-strain the age of DS3 to range from 5.23 to 3.83 Ma.
Depositional sequence 1 (DS1) correlates to the lower Peace River Formation of Missimer
(1997; 1999) where the data from the present study are linked to data from Missimer at the W-
17115 corehole (Figs. 5 and 7). Data presented by Edwards et al. (1998) and Weedman et al.
(1999) are consistent with deposition of DS1 during the Tor-tonian and Messinian ages (11.2-
5.32 Ma). Results herein suggest that the age of DS1 is probably at most 11 Ma and no younger
than 7.2 Ma, the probable maximum age of CS2. Biostratigraphic data from CS2 and CS3 are
consistent with deposition of DS2 during the latest Tortonian and Messinian ages (Fig. 7).
Interval I of the Long Key Formation in the Florida Keys (Guertin et al., 1999) is probably equiv-
alent to DS2 (Fig. 7). Guertin et al. (1999) assign Interval I to the Messinian age, suggesting that
Interval I may be equivalent to the upper portion of DS2 that occurs beneath the Florida penin-
sula (Fig. 7). Deposition of the upper Peace River Formation of Missimer (1999) in southwestern
Florida may be coincident with DS3 in southeastern Florida as suggested by an early Pliocene
age for the upper Peace River Formation (Fig. 7).

Ochopee Limestone Member of the Tamiami Formation
Results presented herein suggest that the Ochopee Limestone or DS3 was deposited dur-
ing a time spanning the early-late Pliocene boundary and during the eustatic cycle TB3.6 of Haq
et al. (1988) as shown in Figure 6. Coccolith data from the base of DS4 in well W-9104 are con-
sistent with assignment to Subzone CN12aA (3.83-3.62 Ma) as shown in Figures 5 and 6.
Cunningham et al. (2000, in press) used silicoflagellate and coccolith data to determine the age
of the lower boundary of the Tamiami Formation to be near the early-late Pliocene boundary in
the W-18074 and W-18075 coreholes in Glades County (Fig. 1). Cunningham et al. (2000, in
press) also show a regional-scale seismic sequence boundary at the contact between the Peace
River Formation and the Tamiami Formation. The Tamiami ages at well W-9104 and the two
coreholes (W-18074 and W-18075) in Glades County are consistent with determination by
Missimer (1999) that deposition of the Tamiami Formation began about 0.2 million years after the
Peace River Formation at 4.3 Ma or Tamiami deposition began at about 4.1 Ma. Edwards et al.
(1998) and Weedman et al. (1999) determined the Ochopee Limestone was most likely deposit-
ed during the early Pliocene, but the margin of error spans the late Miocene to late Pliocene age.
A distinctive molluscan assemblage in several coreholes indicates an age for the Ochopee
Limestone near the early-late Pliocene boundary (Edwards et al., 1988).
Age determinations of Edwards et al. (1998), Weedman et al. (1999), and Missimer (1999),
and correlations for the present study suggest that deposition of the Ochopee Limestone was
coincident with deposition of the lower portion of Interval II of the Long Key Formation (Fig. 6).
Foraminiferal sandstone beds occurring at the base of Interval II are composed of a lithofacies
characteristic of the Stock Island Formation (Cunningham et al., 1998), and may represent a dis-
tal portion of the Ochopee Limestone ramp (Fig. 6).

Unnamed Sand
The unnamed sand was probably deposited during the late Pliocene based on age deter-
minations for DS4 (Fig. 6). Correlations shown in Figure 6 suggest that the unnamed sand is
coincident with deposition of the middle and upper parts of Interval II and all of Interval III (Guertin






FLORIDA GEOLOGICAL SURVEY


et al., 1999) within the Long Key Formation.

CONCLUSIONS

In southern Florida, a late-early to early-late Pliocene carbonate ramp (Ochopee Limestone
Member of the Tamiami Formation) is sandwiched between underlying marine siliciclastics of the
late Miocene-to-early Pliocene Peace River Formation and an overlying late Pliocene unnamed
sand. The Peace River Formation contains at least three depositional sequences (DS1, DS2,
and DS3), and the Ochopee Limestone forms a fourth depositional sequence (DS4). The two
youngest depositional sequences of the Peace River Formation, DS2 and DS3, contain con-
densed sections composed of terrigenous mudstone typically overlying diatomaceous mud-
stone. A maximum flooding surface is interpreted to coincide with the contact between diatoma-
ceous mudstone and terrigenous mudstone. The maximum flooding surface bounds the trans-
gressive and highstand systems tracts of DS2 and DS3. The condensed sections have yielded
abundant microfossils, which contribute to their importance for biochronology, defining and cor-
relating the sequences, and reconstructing depositional environments.
Established chronologies and new micropaleontologic results indicate that the Tortonian and
Zanclean ages bracket deposition of the Peace River Formation and provide constraints on the
timing of the deposition of the three Peace River depositional sequences. Depositional sequence
(DS1) prograded across the present-day southern peninsular portion of the Florida Platform dur-
ing the Tortonian age and laps out near the southern margin of the peninsula. The age of DS1 is
probably at most 11 Ma and no younger than 7.2 Ma. During the latest Tortonian and Messinian
ages (probably between 7.2 and 5.6 Ma), progradation of DS2 overstepped the southern lap out
of DS1 and extended at least as far as the Florida Keys. Deposition of DS2 siliciclastics ended,
at the latest, near the Miocene-Pliocene boundary.
Presence of DS3 in southeastern Florida and possibly southwestern Florida and absence in
southernmost Florida suggest a reduction in the southward supply of quartz sand during depo-
sition of the sequence (between 5.23 and 3.83 Ma). This reduction in supply of siliciclastics to
southernmost Florida was followed by aggradational accumulation of heterozoan temperate car-
bonate sediments of the Ochopee Limestone. Deposition of the Ochopee Limestone ended with
basinward lap out near the southern margin of the present-day Florida peninsula. The lap out is
probably coincident with the edge of the siliciclastic shelf containing DS2 of the Peace River
Formation. Deposition of the Ochopee Limestone probably occurred during a late-early to early-
late Pliocene trans-gressive to high-stand sea-level conditions during eustatic cycle TB3.6 of
Haq et al. (1988). Increased supply of siliciclastics to southern Florida resumed in late Pliocene,
burying the Ochopee Limestone ramp. These siliciclastics extend as far south as the middle and
northern Florida Keys. The unnamed sand includes these siliciclastics, which probably are coin-
cident with middle to upper quartz sands of the Long Key Formation beneath the Florida Keys.
Southward transport of quartz sands of the unnamed sand was mostly along the eastern coast
of Florida.

ACKNOWLEDGMENTS

South Florida Water Management District provided partial financial support. Financial sup-
port for Kevin Cunningham came in part from the Division of Marine Geology and Geophysics,
University of Miami. Robert Caughey generously provided well cuttings and logs. Anthony Brown
assisted with preparation of figures. Frank Rupert assisted in identification of mollusks. Scott
Prinos contributed to lithologic descriptions. Ann Tihansky, Lucy Edwards, Tom Missimer and
Tom Scott are thanked for review of the manuscript.






SPECIAL PUBLICATION NO. 49


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Transactions, v. 49, p. 358-368.

Murray, J.W., 1991, Ecology and palaeoecology of benthic foraminifera: Essex, U.K., Longman
Scientific & Technical, 397 p.

Okada, H., and Bukry, David, 1980, Supplementary modification and introduction of code num-
bers to the low-latitude coccolith biostratigraphic zonation: Marine Micropaleontology v. 5, p.
321-325.

Olsson, A.A., 1964, Geology and stratigraphy of southern Florida: in: Olsson, A.A. and Petit,
R.E., Some Neogene mollusca from Florida and the Carolinas: Bulletins of American
Paleontology, v. 47, p. 509-574.

Peacock, R., 1983, The post Eocene stratigraphy of southern Collier County, Florida: South
Florida Water Management District Technical Publication 83-5, 42 p.

Peck, D.M., Slater, D.H., Missimer, T.M., and others, 1979, Stratigraphy and paleoecology of the
Tamiami Formation in Lee and Hendry Counties, Florida: Gulf Coast Association of
Geological Societies Transactions, v. 29, p. 328-341.

Perch-Nielsen, K., 1985, Cenozoic calcareous nannofossils; in: H.M. Bolli and others, (eds.),
Plankton Stratigraphy: Cambridge University Press, p. 427-554.






FLORIDA GEOLOGICAL SURVEY


Perkins, 1977, Depositional framework of Pleistocene rocks in South Florida: in: Perkins, R.D.,
and Enos, P., (eds.), Quaternary sedimentation in South Florida: Geological Society of
America Memoir 147, p. 131-198.

Poag, C.W, 1981, Ecologic atlas of benthic foraminifera of the Gulf of Mexico: New York,
Academic Press, 174 p.

Posamentier, H.W., and James, D.P., 1993, An overview of sequence-stratigraphic concepts:
uses and abuses: in: Posamentier, H.W., Summerhayes, C.P., Haq, B.U., and Allen, G.P.,
(eds.), Sequence stratigraphy and facies associations: Special Publication No. 18 of the
International Association of Sedimentologists, Blackwell Scientific, Boston, p. 3-18

Reese R.S., and Cunningham, K.J., 2000 (in press), Hydrogeology of the gray limestone aquifer
in southern Florida: U.S. Geological Survey Water-Resources Investigations Report 99-
4213.

Sancetta, Constance, 1981, Diatoms as hydrographic tracers: Example from Bering Sea
sediments: Science, no. 211, p. 279-281.

Scott, T.M., 1988, The lithostratigraphy of the Hawthorn Group (Miocene) of Florida: Florida
Geological Survey Bulletin 59, 148 p.

Scott, T.M., and Wingard, G.L., 1995, Facies, fossils and time -A discussion of the litho- and bios-
tratigraphic problems in the Plio-Pleistocene sediments in southern Florida: in: Scott, T.M.,
(ed.), Stratigraphy and paleontology of the Plio-Pleistocene shell beds, southwest Florida:
Southeastern Geological Society Guidebook 35, unpaginated.

Shinn, E.A., and Lidz, B.H., 1988, Blackened limestone pebbles: fire at subaerial unconformities:
in: James, N.P. and Choquette, P.W., (eds.), Paleokarst: New York, Springer-Verlag, p. 117-
131.

Shipboard Scientific Party, 1998, Explanatory notes; in: R.D. Norris and others, (eds.),
Proceedings of the Ocean Drilling Program: Initial Reports 171B, College Station, Texas
(Ocean Drilling Program), p. 11-44.

Smith, K.R., and Adams, K.M., 1988, Ground water resource assessment of Hendry County,
Florida: South Florida Water Management District Technical Publication 88-12, Part 1, 109 p.

Van Wagoner, J.C., Posamentier, H.W., Mitchum, R.M., and others, 1988, An overview of the fun-
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Ward, W.C., Folk, R.L., and Wilson, J.L., 1970, Blackening of eolinite and caliche adjacent to
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p. 548-555.






SPECIAL PUBLICATION NO. 49


Warzeski, E.R., Cunningham, K.J., Ginsburg, R.N., and others, 1996, A Neogene mixed silici-
clastic and carbonate foundation for the Quaternary carbonate shelf, Florida Keys: Journal
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Wedderburn, L.A., Knapp, M.S., Waltz, D.P., and Burns, WS., 1982, Hydrogeologic reconnais-
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Weedman, S.D., Paillet, F.L., Edwards, L.E., and others, 1999, Lithostratigraphy, geophysics,
biostratigraphy, and strontium-isotope stratigraphy of the surficial aquifer system of eastern
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the surficial aquifer system in western Collier county, Florida: U.S. Geo-logical Survey Open-
File Report 97-436, 167 p.

Yanagisawa, Yukio and Akiba, Fumio, 1998, Refined diatom biostratigraphy for the northwest
Pacific around Japan, with an introduction of code numbers for selected biohorizons: Journal
Geological Society of Japan, v. 104, no. 6, p. 395-414.






FLORIDA GEOLOGICAL SURVEY


LATE PALEOGENE AND NEOGENE CHRONOSTRATIGRAPHY
OF LEE COUNTY, FLORIDA

Thomas M. Missimer
CDM/Missimer International, Inc., 8140 College Parkway, Suite 202, Fort Myers, Florida 33919

ABSTRACT

Ages of the geologic formations underlying Lee County, Florida have been in dispute for the
last century. A new, unified chronostratigraphy (age analysis) was developed for the upper
Paleogene and Neogene sediments of the Southwest Florida region. The age constraints were
determined from analysis of samples collected from continuous cores and from compilation of
existing age-data collected by a number of investigators. The ages of the sediments were deter-
mined by the combined use of calcareous nannofossils, planktonic foraminifera, diatoms, stron-
tium isotope stratigraphy, and magnetostratigraphy. Based on these integrated dating tech-
niques, the following age constraints using the Berggren et al. (1995) time scale were placed on
the formations underlying Lee County: the Suwannee Limestone ranges from 33.7 (?) to 28.5
Ma, the Arcadia Formation of the Hawthorn Group from about 26.5 to 12.4 Ma., the Peace River
Formation of the Hawthorn Group from 11(?) To 4.3 Ma, the Tamiami Formation from 4.3 to 2.1
Ma, and the Caloosahatchee Formation from 1.8 to 0.6 Ma. Based on these ages, the
Suwannee Limestone was deposited in the early Oligocene, the Hawthorn Group was deposit-
ed from the late Oligocene to the early Pliocene, the Tamiami Formation was deposited from the
early to the late Pliocene, and the Caloosahatchee Formation was deposited within the late
Pliocene and early Pleistocene.

INTRODUCTION

Ages of the upper Paleogene and Neogene sediments in Lee County have been subject to
debate for many years. Previous stratigraphic investigations have assigned ages to many of the
formations based on paleontological data correlated to areas outside of the Florida Platform
(Cooke, 1939; Mansfield, 1937, 1939; MacNeil, 1944; Parker and Cooke, 1944; Cooke, 1945;
Parker et al., 1955; Akers, 1972; Riggs, 1979; Miller, 1986; COSUNA, 1988; Scott, 1988). The
currently accepted ages of many reference sections used for correlation to the Florida Platform
have changed, but little effort has been given to revising the chronostratigraphy of the Florida
Platform until relatively recently. Beginning in 1972, a series of stratigraphic investigations were
conducted that yielded a large quantity of new age data based on planktonic foraminifera (Akers,
1972; Peck, 1976; Peck et al., 1976; Slater, 1978; Peck et al., 1979a; Peck et al., 1979b;
Armstrong, 1980; Peacock, 1981; Peacock and Wise, 1981, 1982; Jones et al., 1991), calcare-
ous nannoplankton (Peck, 1976; Covington, 1992), diatoms (Klinzing, 1980, 1987), helium-ura-
nium dating (Bender, 1973), vertebrate fossil stratigraphy (Jones et al., 1991), strontium isotope
stratigraphy (Jones et al., 1991; Hammes, 1992; Compton et al., 1993; Mallinson and Compton,
1993; Weedman et al., 1993; Edwards et al., 1998; Weedman et al., 1999), and magneto-stratig-
raphy (Jones et al., 1991).
It is the purpose of this paper to present new data refining the age ranges in the central part
of the South Florida Platform of the Suwannee Limestone, the Arcadia and Peace River
Formations of the Hawthorn Group, the Tamiami Formation, and the Caloosahatchee Formation
(Figure 1). A series of three continuous core borings were used in this investigation (Nos. W-
16242, W-16523, and W-17115 in Figure 2). The new data were obtained using strontium-iso-
tope age dating and magnetostratigraphic analyses with a comparison to and correlation with








SPECIAL PUBLICATION NO. 49


FORMATION


LITHOLOGY


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300

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AGE





FLORIDA GEOLOGICAL SURVEY


OHARLOTTE


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CAPTIVA v





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A


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_________ MARCO
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Figure 2. Map of southern Florida showing the locations of the primary cores
used in this investigation.
existing planktonic foraminifera, calcareous nannoplankton, and other paleontological data. All
age determinations made in this paper utilize the geologic time scale of Berggren et al. (1995).

METHODS

Strontium and Stable Isotope Sample Preparation
Samples of unaltered calcitic mollusk shell and a few phosphorite nodules were collected
from cores W-16242, W-16523 in Lee County, and W-17115 from Collier County for the purpose
of measuring the strontium-isotope ratios to make age determinations. A total of 62 samples
were chosen for analysis from all samples collected based on the location of the samples with-
in the stratigraphic section and the quality of the shell material. A large percentage of the sam-
ples were collected and analyzed from core W-16242 (34 samples), because of the abundant
quantity of unaltered shell, the high percentage of core recovery, and the designation of this core
for magnetostratigraphic analysis. All samples were carefully washed in distilled water, then






SPECIAL PUBLICATION NO. 49


placed in an ultrasonic bath to remove additional contaminants. Each sample was further
cleaned using dilute hydrochloric acid. Most samples were then cut to expose a fresh surface.
Powdered shell was collected by either drilling out the shell interior with a clean dental drill or a
clean cube of shell was extracted from the middle of the sample and crushed into a powder.
All strontium isotope measurements were made at the University of Florida. The analytical
procedure used is described in detail in McKenzie et al. (1988) and Hodell et al. (1990). The
87Sr/86Sr ratios were measured in the triple-collector dynamic mode on a VG354 thermal ion-
ization mass spectrometer. All strontium ratios were normalized to 86Sr/88Sr = 0.1194 and to
Standard Reference Material (SRM) 987 = 0.710235. An evaluation of the analytical precision
indicated that the average within-run precision was +/-1 x 10-5 (2 standard error of the mean).
When all errors associated with the analytical procedure were summed, a range of +/-22 to 24 x
10-6 was determined for the period in which the data were collected. The strontium isotope vari-
ation with time in the World Ocean, as presented in the model of Hoddell et al. (1991), was used
to estimate ages. The error in conversion to estimated ages cannot be determined, because
the model used must be assumed to be correct (P. Mueller, personal communication). The
Hodell ages were then corrected to the Berggren et al. (1995) age model.

Paleomagnetic Measurements
Detailed paleomagnetic data were collected from core W-16242. Up-down oriented sam-
ples were collected from 291 stratigraphic intervals. Since the core was collected with a drilling
rig, the only orientation of the samples that could be determined was the stratigraphic up direc-
tion. Core orientation was checked using geopels wherever observed. Therefore, only inclina-
tion data were used to determine the prevalent polarity during or shortly after deposition. All
magnetic measurements were made at the University of Miami, Rosenstiel School of Marine and
Atmospheric Science. The paleomagnetic measurements were made using a 2G Enterprises
755 superconducting magnetometer contained within a shielded room. A combination of alter-
nating field and thermal demagnetization methods were utilized to obtain inclination data and to
determine polarity.

Foraminifera
Studies of the foraminifera in the Neogene and late Paleogene sediments in Southwest
Florida were presented in a series of theses and resultant publications (Peck, 1976; Peck et al.,
1976; Peck et al., 1977; Peck et al., 1979a; Peck et al., 1979b; Slater, 1978; Peacock, 1981;
Peacock and Wise, 1981; Peacock and Wise, 1982). Since detailed analyses of foraminifera
were previously performed on nearby wells having very direct and reliable lithostratigraphic cor-
relation to the cores in this study, projected planktonic foraminifera ages are used. The strati-
graphic correlation between the cores studied and the planktonic information collected from
nearby wells was accomplished by tracing continuous seismic reflection lines between the wells
and core W-16242 on the north (20 km) and by direct correlation of the stratigraphic units into
core W-16523 on the south (8 km).
The entire Neogene and late Paleogene stratigraphic section was not studied in the
foraminifera research, but the work was concentrated on the "Tamiami Formation," which was
defined at that time as all sediments lying between the disconformity marking the top of the
Arcadia Formation and the disconformity marking the base of the Caloosahatchee Formation.
Since the definitions of the stratigraphic units have been changed to produce a more consistent
framework (Scott, 1988), the foraminiferal investigations were performed on both the Tamiami
and Peace River Formations. The only age diagnostic data, however, were obtained from the
Peace River Formation. The work performed by Peacock (1981) was mostly limited to the
foraminiferal occurrences in the lower part of the Arcadia Formation.






FLORIDA GEOLOGICAL SURVEY


Calcareous Nannofossils

Introduction
Samples were collected throughout cores W-16242 and W-16523 for calcareous nannofos-
sil analysis. This work was conducted as a research project at the Florida Geological Survey by
J. Mitchner Covington. The results of the calcareous nannofossil analyses of these cores was
reported by Covington (1992).

Calcareous Nannofossil Stratigraphy of Core W-16242
Calcareous nannofossils were found in core W-16242 only above the contact with the
Arcadia Formation or in the Peace River Formation and younger Neogene units. Also, the sam-
ples for calcareous nannofossils were not collected from the lowermost part of the Peace River
Formation. Heavy alteration of the carbonate sediments probably caused the destruction of any
calcareous nannofossils that may have occurred in the Arcadia Formation.
The investigation conducted by Covington (1992; unpublished Florida Geological Survey
data) showed that samples from core W-16242 contain varying abundance and diversity of cal-
careous nannofossils. The age ranges of the calcareous nannofossils are plotted with the other
age data on the unified chronostratigraphy of core W-16242 (Figure 3).
The observed assemblage included common to abundant Sphenolithus abies and
Reticulofenestra pseudoumbilica, which collectively yield an early Pliocene age estimate.
Discoasters were also present in this interval for the first time, suggesting that the paleoenviron-
ment was more favorable for the deposition of these forms at that time. No calcareous nanno-
fossils were found in the core below a depth of 88.4 m, or just above the contact between the
upper and lower part of the Peace River Formation.
Abundant calcareous nannofossils occurred between 73.2 and 88.4 m. Nannofossil abun-
dance began to decrease at a depth of 67.1 m and samples collected from the interval between
48.4 and 64.6 m contained no preserved calcareous nannofossils.
The rare species, Sphenolithus abies, was observed at the 27.4 m depth. The extinction of
S. abies occurs in the NN15/CN11b interval and approximates the boundary between the early
and late Pliocene. This depth interval occurs within the Pinecrest Member of the Tamiami
Formation. A barren interval between 21.2 and 22 m was observed.
In the uppermost samples collected from 3 to 12.2 m, a few Gephyrocapsa caribbeanica
were found and no Pseudoemiliania lacunosa were observed. This interval is probably within
nannofossil zone NN20/CN14b of Martini (1971) and Okada and Burky (1980). Diversity is quite
low in this interval and the absence of P. lacunosa may be a function of paleoenvironment
rather than age. Therefore, the inferred age may be older than indicated. The general age of
these sediments is interpreted to be late Pliocene or Pleistocene.

Calcareous Nannofossil Stratigraphy of Core W-16523
Calcareous nannofossils were found in core W-16523 from the mid-section of the Arcadia
Formation to the top of the core. They were not found in every stratigraphic interval, but the gen-
eral state of fossil preservation was better in core W-16523 compared to core W-16242.
The occurrence of Cyclicargolithus floridanus was noted at 177.4 m. This species may be
indicative of the uppermost Oligocene. A noteworthy occurrence includes that of Helicosphaera
ampliaperta at 153.6 m below surface. This species indicates an age between CN3/NN4 and
CN1/NN2 or early Miocene.









SPECIAL PUBLICATION NO. 49






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FLORIDA GEOLOGICAL SURVEY


Diatoms
Diatoms were found in various zones within the Peace River Formation. The diatom stratig-
raphy of this section was studied by Klinzing (1987) and the diatom occurrences were noted in
the Peck et al. (1979). Klinzing (1987) described an assemblage of diatoms in core W-14072,
which is located about 7 km to the east of core W-16523. Peck et al. (1979) noted the occur-
rence of the diatoms in unit 2B and stated that only two of the diatoms were age diagnostic. The
species Actinoptycus bismarkii and Diploneis exemta were reported to occur exclusively in the
late Miocene. Klinzing (1987) concluded that the Peace River Formation was Pliocene in age
based on the occurrence of two species, Thalassiosira oestrupii and Cussia tatsunokuchiensis,
which were believed to occur exclusively in the Pliocene. The work of Klinzing (1987) may indi-
cate that the primary diatom bed, which occurs near the base of the upper Peace River
Formation is Pliocene in age. However, the absence of detailed range data for each diatom
species raises questions with regard to the actual stratigraphic occurrence of the marker
species. Based on the diatom data obtained on the Peace River Formation, it is concluded that
no diagnostic age designation can be made.

Strontium-Isotope Stratigraphy

Introduction
The ratio of 87Sr/86Sr in seawater has varied significantly during Phanerozoic time
(Wickman, 1948; Brass, 1976; Burke et al., 1982; Koepnick et al., 1985; Hess et al., 1986; Miller
et al., 1988; Smalley et al., 1994). In the Tertiary, the ratio has increased, but at a variable rate
(Hodell et al., 1989; Hodell et al., 1990; Hodell et al., 1991). The origin of the strontium isotope
variation is not fully understood, but the long-term changes are related to tectonic processes,
which caused changes in the exposure of the earth's crust and rock types exposed at surface to
weathering. Short time-scale climatic changes influencing continental weathering, such as
glaciation, may be responsible for exposing old shield rocks, leading to accelerated erosion rates
of rocks with higher 87Sr/86Sr ratios (Armstrong, 1971).
If equilibrium between the isotopic ratios of strontium in seawater and living, shell-producing
organisms is assumed, the time dependant change of the strontium-isotope ratios in seawater is
reflected in unaltered shell tests and can be used to date the material (Hoddell et al., 1991).
Therefore, the 87Sr/86Sr ratio in unaltered calcareous marine fossils has been used success-
fully to determine the age of marine sediments (McKenzie et al., 1988). Both marine microfos-
sils benthicc foraminifera) and mollusk shells have been dated using the 87Sr/86Sr technique
(Hodell et al., 1991, Jones et al., 1991; Bryant et al., 1992; Compton et al., 1993). Compton et
al. (1993) also demonstrated that phosphorite nodule strontium-isotope dates can be used to
estimate the age of marine sediments when reworking is not significant.

Results
Strontium-isotope ratios were measured on 62 samples collected from cores W-16242, W-
16523, and W-17115 (Table 1). Age determinations were made using the regression curves
developed by Hodell et al. (1991) with an extrapolation to the late Oligocene and comparison to
the curve developed by Oslick et al. (1994). The measured 87Sr/86Sr ratios were normalized to
the appropriate NBS-987 value before age determinations were made. A total of 34 samples
were analyzed from core W-16242, 17 from core W-16523, and 11 from core W-17115. In core
W-16242, the material used for strontium-isotope analysis was mostly unaltered calcitic mollusk
shell with the exception of samples M-5, M-6, and M-7 (aragonitic mollusks), sample M-36 (phos-
phorite nodule), sample M-37 (phosphorite crust), sample M-40 (recrystallized coral), and sam-
ple M-42 foraminiferaa extracted from whole rock). In cores W-16523 and W-17115, all material






SPECIAL PUBLICATION NO. 49


analyzed for strontium isotopes were unaltered calcitic mollusk shell.
The reduction in the 87Sr/86Sr ratio with depth was relatively consistent in core W-16242
(Figure 3) with the exception of three samples within the Tamiami Formation section, numbers
M-13, M-14, and M-15 and one sample in the lower part of the Peace River section, number M-
20. The four samples with lower than expected strontium-isotope ratios were shell samples, from
the genus Hyotissa. Petrographic examination of thin sections containing Hyotissa showed that
in some cases very fine sand-sized phosphorite grains were trapped within the shell structure of
the mollusk. Since phosphorite is reworked throughout the younger part of the stratigraphic sec-
tion above the Arcadia Formation, it is likely that any phosphorite incorporated in younger mol-
lusk shells would be much older and would be a significant factor in causing a lower 87Sr/86Sr
ratio. It is also possible, although less likely, that these samples were reworked. There is con-
sistency in the 87Sr/86Sr ratio above and below the suspect samples, which strengthens the
case to dismiss the validity of these samples. A similar case can be made for sample M-20,
which yielded a 87Sr/86Sr ratio much lower than anticipated. In this case, it is likely that this
shell material was reworked, because of its stratigraphic position near a major disconformity.
Based on the variation in the data within the stratigraphic framework, it can be concluded that
this set of data appears to yield
a relatively consistent pattern and that it is necessary to have a fairly large number of analyses
in order to rely strictly on strontium-isotope data for age determination.
Strontium-isotope data collected from core W-16523 showed considerable scatter, but the
overall trend for the stratigraphic units was similar to core W-16242. Sample K105.5 showed a
very low 87Sr/86Sr ratio, which is the probable result of phosphorite contamination as previous-
ly described or the shell may be reworked. Sample K585.3 showed a very high 87Sr/86Sr ratio,
which cannot be explained, but may be the result of sample contamination.
The strontium-isotope data from core W-17115 also show a relatively consistent strati-
graphic pattern similar to the other cores. There is some scatter in the data in the lower part of
the core with sample MI571 showing a higher than expected 87Sr/86Sr ratio. The lower strati-
graphic section of core W-17115 was not extensively sampled because of a lack of acceptable
material for strontium-isotope analysis.

Magnetostratigraphy

Introduction
Determination of magnetic polarity changes within sediment sequences is an accepted
method of approximating the age of the sediments (Cande and Kent, 1992; Berggren et al.,
1995a). However, the use of the magnetostratigraphy is not an independent method to deter-
mine age, especially when a stratigraphic section is divided by one or more disconformities. In
this study, a number of biostratigraphic and chronostratigraphic methods were applied to assist
magnetostratigraphic correlation to the Global Polarity Time Scale (GPTS) of Berggren et al.
(1995).
Measurement of depositional remanent magnetization or early post-depositional remanent
magnetization in carbonate sediments has been recently utilized to determine polarity changes
(McNeill et al., 1988; McNeill, 1989). The Neogene sediments of the South Florida Platform
present some interesting problems, because they contain both weakly magnetized carbonate
sediments and detrital siliciclastic sediments containing a significantly stronger magnetic carrier.

Laboratory Methods
Analytical procedures utilized in this investigation closely follow those described by McNeill
et al. (1993). Detailed descriptions of the paleomagnetic measurement methods are given in












TABLE 1.


"Sr/86Sr MEASUREMENTS AND CALCULATED AGES OF SAMPLES
FROM CORES W-16242, W-16523, AND W-17115


Sample Description Depth (m) "8Sr/"Sr Raw Regression Age' Age 2 e2Ma) Age Range3 (Ma)
No. 8"Sr/"Sr

Core W-16242

M-5 Chione cancellata (bivalve) 21.03 0.709086 0.709077 1.81 2.37-1.25

M-6 Turritella sp. 23.77 0.709048 0.709039 2.45 3.01-1.89

M-7 Pecten 28.04 0.709041 0.709032 2.45 3.01-1.89
-rn
M-8 Chlamys eboreous 29.95 0.709022 0.709013 2.91 3.47-2.35 --
O
M-9 Chlamys eboreous 31.70 0.709049 0.70904 -" 4.92-2.61

M-10 Belanus sp. 33.04 0.709015 0.709006 ---. 4.92-2.61 >
m
M-11 Pecten 35.36 0.709064 0.709055 --.. 4.92-2.61 O
I-
M-12 Pecten 36.91 0.709025 0.709016 ---** 4.92-2.61 O

M-13 Hyotissa 43.98 0.708874 0.708865 10.49* 11.85-9.13
I-
M-14 Hyotissa 44.58 0.708907 0.708898 9.23* 10.59-7.87 I)
C
M-15 Hyotissa 47.24 0.708905 0.708894 9.38* 10.74-8.02
m
M-16 Pecten 49.12 0.709032 0.709023 ---"* 4.92-2.61

M-17 Pecten 50.29 0.709065 0.709056 ---* 4.92-2.61

M-19 Oyster 57.04 0.709031 0.709022 ---* 4.92-2.61

M-29 Pecten 74.07 0.70905 0.709041 ---** 4.92-2.61

M-30 Pecten 78.09 0.70901 0.709001 ---* 4.92-2.61

M-31 Pecten 88 0.70903 0.709021 --- **4.92-2.61

M-20 Oyster 88.7 0.708626 0.708617 17.5* 17.98 18.24-16.76

M-32 Oyster 89.21 0.70886 0.708851 10.9 12.26-9.54













TABLE 1.


"7Sr/86Sr MEASUREMENTS AND CALCULATED AGES OF SAMPLES
FROM CORES W-16242, W-16523, AND W-17115


Sample Description Depth (m) 8Sr/"Sr Raw Regression Age'(Ma) Agez(Ma) Age Range3 (Ma)
No._ 87Sr/'6Sr

M-33 Oyster 106.22 0.70878 0.708771 13.8 15.7 15.16-12.44

M-21 Oyster 113.33 0.708768 0.708759 14.3 17.5 15.66-12.94

M-22 Oyster 113.69 0.708746 0.708737 15.1 17.2 16.46-13.74

M-25 Oyster 118.57 0.708643 0.708634 17.3 21.7 18.04-16.56

M-27 Oyster 121.46 0.708752 0.708743 15.3 16.9 16.66-13.94

M-28 Oyster 126.49 0.708742 0.708733 15.3 16.9 16.66-13.94

M-34 Oyster 137.89 0.70864 0.708631 17.3 17.79 18.04-16.56

M-35 Pecten 162.92 0.70849 0.708481 19.8 19.95 20.54-19.06

M-36 Phosphorite nodule 166.42 0.70855 0.708541 18.8 19.12 19.54-18.06

M-37 Phosphorite crust 173.13 0.70846 0.708451 20.3 20.3 21.04-19.56

M-38 Mollusk 176.48 0.70834 0.708331 22.5 22.2 23.24-21.76

M-39 Pecten 190.23 0.70813 0.708121 25.2 25.7 25.94-24.46

M-40 Coral (altered) 192.02 0.70813 0.708121 25.2 25.7 25.94-24.46

M-41 Bivalve 202.69 0.70807 0.708061 26 26.7 26.74-25.26

M-42 Whole rock (forams) 207.87 0.70801 0.708001 28.3 29.61-26.99

W-16523

K18 Oyster 5.49 0.70908 0.709071 1.89 2.45-1.33

K55 Oyster (thin walled) 16.76 0.70893 0.708921 ---" 4.92-2.61













TABLE 1.


"7Sr/"6Sr MEASUREMENTS AND CALCULATED AGES OF SAMPLES
FROM CORES W-16242, W-16523, AND W-17115


Sample Description Depth (m) 87Sr/"Sr Raw Regression Age'(Ma) Age2(Ma) Age Range3 (Ma)
No. 87Sr/86Sr


K71.6 Anomia (bivalve) 21.82 0.70900 0.708991 _____ 4.92-2.61

K105.5 Oyster 32.16 0.70868 0.708671 16.6 17.2 17.34-15.86

K148.5 Pecten 45.26 0.70884 0.708831 11.7 13.3 13.06-10.34

K193 Oyster 58.83 0.70885 0.708841 11.3 13.0 12.66-9.94

K206 Oyster 62.79 0.70852 0.708511 19.4 19.6 20.14-18.66

K252.1 Oyster 76.84 0.70857 0.708561 18.5 18.4 19.24-17.76

K301.9 Oyster 92.01 0.7085 0.708491 19.6 19.8 20.34-18.86

K397 Oyster 121.01 0.70856 0.708551 18.6 18.9 19.34-17.86

K443.2 Pecten 135.09 0.70859 0.708581 18.9 18.5 19.64-18.16

K492.1 Plicula (bivalve) 149.99 0.70844 0.708431 20.5 20.5 21.24-19.76

K553 Pecten 168.55 0.70828 0.708271 23.7 23.9 24.44-22.96

K585.3 Pecten 178.4 0.70873 0.708721 15.9 17.9 16.64-15.16

K623.6 Hyotissa 190.07 0.70813 0.708121 25.2 25.7 25.94-24.46

K664.5 Pecten 202.54 0.70812 0.708111 25.4 25.8 26.14-24.66

K708.2 Pecten 215.86 0.70805 0.708041 26.2 27.0 26.94-25.46

W-17115

MI47.5 Hyotissa 14.48 0.70903 0.709021 ---' 4.92-2.61

MI75.5 Oyster-thin watt 23.01 0.70903 0.709021 ---" 4.92-2.61














8"Sr/86Sr MEASUREMENTS AND CALCULATED AGES OF SAMPLES
FROM CORES W-16242, W-16523, AND W-17115


' Age from HodeUl, et al. (1991)
Corrected to time scale of Berggren, et al. (1995)

2 Age from Oslick, et al. (1994)
Corrected to time scale of Berggren, et al. (1995b)

* Not plotted, obvious stratigraphic error

** On flat part of Hoddell curve


TABLE 1.


Sample Description Depth (m) 87Sr/I'Sr Raw Regression Age'(Ma) Agez(Ma) Age Range3 (Ma)
No. 87Sr/86Sr

MI111.1 Oyster thin-wall 33.86 0.70904 0.709031 -- _____-4.92-2.61

MI144.5 Pecten 43.89 0.70902 0.709011 ___-_-_-4.92-2.61

MI192 Bivalve 58.52 0.70889 0.708881 9.94 11.30-8.58

MI340 Oyster 103.63 0.70873 0.708721 15.7 16.5 17.06-14.34

M1389.3 Oyster 118.66 0.70871 0.708701 16.3 16.8 17.04-15.56

M1447 Bivalve 136.25 0.70872 0.708711 16.1 16.7 16.84-15.36

MI474.4 Oyster-thin wall 144.6 0.70857 0.708561 18.5 18.8 19.24-17.76

MI571 Pecten 174.04 0.70863 0.708621 17.5 17.9 18.24-16.76

M1623.3 Hyotissa 189.98 0.70852 0.708511 19.4 19.5 20.14-18.66






FLORIDA GEOLOGICAL SURVEY


Missimer (1997; 2000).

Magnetostratigraphy and Age Implications
Paleomagnetic polarity data are useful to refine and constrain the age of sediments when
they can be correlated to the GPTS using other age-dating techniques, including strontium iso-
topes and microfossil assemblages. The magnetic polarities for core W-16242 in relationship to
the core lithologic properties and other isotopic data are presented in Figure 3. In order to cor-
relate the magnetic polarity data to the GPTS, the magnetic polarity data, strontium-isotope
ages, and ranges of calcareous nannofossils for core W-16242 are presented in a graphic plot
(Figure 3). Analyses of the magnetic polarity changes in the core are discussed for stratigraph-
ic units, which include: 1) the Suwannee Limestone, 2) the Arcadia Formation, 3) the Peace
River Formation, 4) the Tamiami Formation, 5) the Caloosahatchee Formation, and 6) the com-
bined Fort Thompson Formation and Holocene.

DISCUSSION

Ages of Late Paleogene and Neogene Stratigraphic Units

Introduction
A unified chronostratigraphic analysis was performed on core W-16242 on sediments from
the Suwannee Limestone to land surface (Figure 3). Then, other data on the same stratigraphic
section were compiled from this and other geologic investigations on the South Florida Platform
to synthesize the most current age constraints on the late Paleogene and Neogene sediments
in Lee County. The age ranges of each of the formations investigated, including the Suwannee
Limestone, the Hawthorn Group, the Tamiami Formation, and the Caloosahatchee Formation are

TABLE 2. POSSIBLE AGES OF SELECTED NEOGENE AND
LATE PALEOGENE FORMATIONS ON THE
SOUTH FLORIDA PLATFORM


Formation Estimated Age Range (Ma)

Suwannee Limestone 33.7(?) to 28.5
Arcadia Formation 26.6 to 12.4

Lower Peace River Formation 11 (?) to 8.5
Upper Peace River Formation 5.23 to 4.29

Hawthorn Group 26.6 to 4.29
Pinecrest Member 3.22 to 2.15

Tamiami Formation 4.29 to 2.15

Caloosahatchee Formation 2.14 or 1.77 to 0.6


given in Table 2. These new age ranges for each of the stratigraphic units are compared to past
age estimates and to the current geologic and paleontological time scales in Figure 4.








SPECIAL PUBLICATION NO. 49


STANDARD
CHRONOSTRATIGRAPHY

COSUNA (1988) SCOTT (1988) THIS PAPER
and HAMMES (1992) SOUTH FLORIDA
SYSTEM SERIES STAGES Ma


______ HLCNE_ __________ ____________ __________________


QUARTERNARY PLEISTOCENE


I | 11.2


- 20.5


AQUITANIAN


CHATTIAN


I 1 28.5


RUPELIAN


Tampa Member









Suwannee
Limestone


Tmmi 1r minn 77

// w sso


S Bone Valle








Peace <
River
Formation co



Arcadia
Formation


Arcadia
Formation
Tampa
Member




Suwannee
Formation


Caloosahatchee
Formation
Pinecrest
Tamiami Memer
Formation Sand
I Facies
Peace River UPG





Lower
Peace River LPG
Formation




-D-


Arcadia
Formation

B







Arcadia A
Formation





Suwannee
Limestone


Figure 4. Unified chronostratigraphy of core W-16242 (Captiva Island). The ages of the Global
Polarity Time Scale conform to Berggren et al. (1995).

Suwannee Limestone
Only one strontium-isotope age determination was made on the Suwannee Limestone in
core W-16242, but a large number of additional isotope age determinations were made on the
Suwannee Limestone in several other cores located to the north of the this investigation
(Hammes, 1992; Brewster-Wingard et al. 1997). Hammes (1992) concluded that the age of the
Suwannee Limestone ranged from 33.7 to 29.2 Ma (corrected to time scale of Berggren et al.,
1995) and was confined strictly to the Rupelian Age of the early Oligocene. The strontium-iso-
tope data point in core W-16242 was from a sample collected from near the top of the core. It


PIACENZIAN

ZANCLEAN


MESSINIAN



TORTONIAN


- 5.321


SERRAVALLIAN


LANGHIAN


BURDIGALIAN


Peace River
Formation


Arcadia
Formation


-16.41






FLORIDA GEOLOGICAL SURVEY


produced an age of 29.5 to 26.8 Ma. The magnetostratigraphic analysis of core W-16242
showed a good correlation between the magnetic polarities and the GPTS. The top of the
Suwannee Limestone has a normal polarity that is correlated to Chron C10n. n, which has an
age range from about 28.5 to 28.3 Ma. Since the full thickness of the Suwannee Limestone was
not penetrated in core W-16242, it is not possible to constrain the basal age of the unit. Based
on the data collected from core W-16242 and the large amount of data collected on the forma-
tion to the north, it is concluded that the Suwannee Limestone at this location has an estimated
age range from 33.7 to 28.5 Ma and is restricted to the early Oligocene. The disconformity on
top of the unit is believed to be the mid-Oligocene sea-level event, which constrains the upper
age limit to 28.5 Ma. This analysis is in agreement with Hammes (1992), but differs from
Brewster-Wingard et al. (1997), who believes the upper age range extends into the early
Miocene.

Hawthorn Group-Arcadia Formation
A large number (31) of strontium-isotope age determinations were made on Arcadia
Formation sediments in cores W-16242, W-16523, and W-17115. Also, many additional stron-
tium-isotope age determinations were made on the Arcadia Formation in core W-10761 by
Compton et al. (1993) and in other cores to the north by Brewster-Wingard et al. (1997). Most
of the age determinations range from 26.8 to 13.1 Ma for the Arcadia Formation (all ages cor-
rected to the time scale of Berggren et al. 1995). In the very middle of the platform, which occurs
near the site of the Koreshan core (W-16523), some younger carbonate sediments were pre-
served in the section. At this location a single sequence, Al in the core, was deposited on top
of the middle Miocene disconformity as suggested by a carbon isotope shift at this location. The
magnetostratigraphy of the Arcadia Formation is quite complex and subject to several interpre-
tations within the constraints of the strontium-isotope ages. The base of the Arcadia Formation
has a strontium-isotope age of about 26.6 to 25.3 Ma based on the data from core W-16242. The
magneto-stratigraphic correlation to the GPTS indicates that the normal polarity unit at the base
of the formation correlates to Chron C8n.2n, which has an age range of 26.6 to 26.0 Ma. The
top of the formation correlates to Chron C5Ar, which has an age range of 12.8 to 12.4 Ma. Based
on the strontium isotope data and the magnetostratigraphic data, the top of the Arcadia
Formation at most locations has an age of about 12.4 Ma. It must be stated, however, that this
surface is a major disconformity and is subject to rather extreme variation in erosional relief that
could lead to a variable age at any location as shown in Guertin et al. (2000). Based on all of
the data analyzed, the Arcadia Formation deposition began in the late Oligocene and terminat-
ed in the middle Miocene.

Hawthorn Group-Peace River Formation
The Peace River Formation is divided into two distinctively different stratigraphic units by a
regional disconformity. The lower part of the formation is a relatively flat-bedded, predominant-
ly siliciclastic unit with some carbonate sediment. The upper part of the formation is a mixed sili-
ciclastic/carbonate, deltaic unit containing graded beds with topset, forest geometries. Because
of the differences in sediment faces, the presence of the disconformity, and inferred significant
difference in age between the two units, they are discussed individually.
The age data on the lower Peace River Formation has been determined in a number of wells
in Lee and Hendry counties by analysis of the calcareous nannofossil and planktonic
foraminifera assemblage (Peck et al., 1979a; Peck et al., 1979b; Covington, 1992). A late
Miocene age was determined for the lower part of the Peace River Formation with the general
age restricted to foraminiferal zones N18 and N17 or the solely N17 based on the age of the
Discoaster quinqueramus Zone of Gartner (1969). The strontium-isotope data of core W-16242






SPECIAL PUBLICATION NO. 49


yielded a single age determination of 11.8 to 9.3 Ma. Single strontium-isotope age determina-
tions were made on the lower Peace River Formation in cores W-16523 and W-17115, which
yielded ages of 13.1 to 10.3 Ma and 11.3 to 8.6 Ma, respectively. Compton et al. (1993) also
obtained several age determinations in the 13.1 to 10.0 Ma range, particularly on phosphorite
nodules in the lower part of the Peace River Formation. The lower Peace River section in core
W-16242 is only about 3.5 m thick and is therefore either a condensed section or a small part of
the full section. Paleomagnetic analysis of the lower Peace River Formation in core W-16242
showed that all samples yielded a reversed polarity. A quite tentative correlation of this section
was made to the GPTS. It correlates to Chron C5r, which has an age range from about 11.9 to
10.9 Ma. Based on the data collected in this investigation and in previous investigations, the
Peace River Formation has a probable age range from about 11 to 8.5 Ma, which is late Miocene.
The older phosphorite nodules dated by Compton et al. (1993) are believed to be reworked from
the erosion of the underlying Arcadia Formation or from erosion of the Peace River Formation to
the north where it is older.
Past investigations of the foraminifera and calcareous nannofossils within the Upper Peace
River Formation (defined at one time to be part of the Tamiami Formation) suggested that the
formation ranges from late Miocene to early Pliocene in age (Peck et al., 1979a; Peck et al.,
1979b; Covington, 1992). Strontium-isotope age determinations from core W-16242 all occurred
on the flat part of the curve, yielding an age range of 4.9 to 2.6 Ma. Ages determined by
Compton et al. (1993) for the Peace River Formation in core W-10761 are in the 5.7 to 4.9 Ma
range. Because of the flattening in the seawater strontium-isotope curve, virtually all sediments
having an age range of 4.9 to 2.6 Ma date about the same. The magnetostratigraphy of core W-
16242 correlated to the GPTS produced some reasonably diagnostic age data for the Peace
River Formation (Figure 3). The base of the core has a reversed polarity that corresponds to
Chron C3n.4n, which has an age range of 5.2 to 5.0 Ma. The base of the Peace River Formation
is constrained to this age range, but there is a very high probability that the age of the formation
base is a maximum of 5.23 Ma. This conclusion is reached based on the assumption that the
late Miocene (Messinian) global sea level event should create a hiatus at this age. The reversed
polarity section at the top of the Peace River Formation corresponds to the Chron C3n.lr, which
has an age range from 4.5 to 4.3 Ma. Therefore, the top of the formation is constrained to this
age range, but it is believed that the actual age is probably about 4.4 Ma based on the probable
rapid deposition of the deltaic facies and the age constraint provided by the overlying formation.
The polarity changes measured in core W-16242 correlate well with the GPTS in this strati-
graphic interval. It is concluded that the upper part of the Peace River Formation is early
Pliocene in age with the absolute age ranging from about 5.23 to 4.29 Ma. The Miocene-
Pliocene contact lies between the deltaic sediment sequence and the underlying flat-bedded
mixed siliciclastic/carbonate sequence. The occurrence of coarse siliciclastic and phosphatic lag
deposits commonly marks this boundary. A similar age was determined for this unit in Collier
County by Edwards et al. (1998) and Weedman et al. (1999).
Tamiami Formation.
Age determinations on the Tamiami Formation in core W-16242 were made primarily by
strontium-isotope analysis and magnetostratigraphic analysis. The formation is divided by a dis-
conformity, which separates the Sand Facies from the overlying Pinecrest Member, using the ter-
minology of Missimer (1992). Each of these units has a different age range and they are dis-
cussed separately.
All of the strontium-isotope samples collected from the lower part of the upper Peace River
Formation and the overlying Tamiami Formation yield approximately the same age, because of
the flatting of the strontium-isotope curve and less stratigraphic resolution. The magnetic polar-
ity of the Lower Tamiami Formation is predominantly reversed with the exception of a very thin






FLORIDA GEOLOGICAL SURVEY


interval in the middle of the section and another thin interval, about 1 m, in the lower part of the
section. A significant part of the section was unlithified sand and friable sediment from which no
good quality samples could be obtained. Based on all data obtained, the base of the Sand facies
of the Tamiami Formation correlates to Chron C3n.ln and the top of the unit with Chron C2Ar.
This correlation gives the Sand Facies Member of the Tamiami Formation an age range of about
4.3 to 3.0 Ma. In consideration of the disconformity at the top of the Sand Facies, the upper
boundary is more likely at about 3.2 Ma and the lower boundary of the Pinecrest Member at
about 3.0 Ma. This interpretation is not unique because of the uncertainty in the measurements
within core W-16242. It is possible that less time is missing across the disconformity between
the Pinecrest Member and Sand Facies Member. However, there is a significant change in fau-
nal assemblage and mineralogy of the sediment at this point in the core from the occurrence of
multiple species of abundant aragonitic shell above the disconformity to a much lower diversity
of molds and casts with no aragonitic shell below it. This suggests a significant time lapse, which
would be at least 0.3 m.y. based on this interpretation or as small as 70 k.y. based on correla-
tion of each magnetic polarity change to the GPTS.
Three strontium-isotope analyses were made in the Pinecrest section. The age ranges for
these analyses are from 3.4 to 2.0 Ma with the ages being in stratigraphic order. The two
younger age determinations have a higher probability of being more accurate than the older age,
because of a general flattening of the strontium-isotope curve from 4.9 to 2.6 Ma (Hoddell et al.,
1990). Correlation of the magnetic polarity changes in core W-16242 to the GPTS using the
strontium-isotope ages as guides was made. The lower part of the Pinecrest Member in core W-
16242 has a normal polarity correlating to Chron C2An.ln. This corresponds to the upper part of
the Gauss chron with an age range of 3.2 to 3.1 Ma. This normal polarity interval in the core
could represent all of the C2An.ln chron or more likely represents only part of it. However, the
age constraint on the base of the Pinecrest must be placed on the maximum age of 3.2 Ma. The
age constraint on the upper boundary is more problematical, because there is a small gap in the
polarity data with reversed polarity underlying it. The reversed polarity interval correlates to
anomaly Chron C2r.2r, which has a time range of 2.581 to 2.15 Ma. This time increment is equiv-
alent to the lower Matuyama Chron. If the interpreted correlation to the GPTS is assumed to be
correct, the constraint on the upper boundary is about 2.15 Ma. Therefore, based on the avail-
able data from core W-16242, the Pinecrest Member of the Tamiami Formation in core W-16242
has an age range of 3.2 to 2.2 Ma (with consideration of the disconformities bounding the
Pinecrest) the most probable range is 3 to 2 Ma. This age range correlates quite well to the ages
determinations made for the Pinecrest Member in the Sarasota site to the north of the study area
by Jones et al. (1991). Bender (1973) used the uranium/helium technique to determine the age
of two corals from the Pinecrest Member. These corals produced ages of 4.24 and 3.69 Ma (cor-
rected to time scale of Berggren et al., 1995). Akers (1974) determined that the age of the
Pinecrest Member was Mid-Pliocene based on the concurrent occurrence of Gephyrocapsa
caribbeannica, Reticulofenestra pseudoumbilica, and Sphenolithus abies, which have age
ranges of younger than 3.6 Ma, 11.9 to 3.7 Ma, and 7(?) to 3.66 Ma, respectively. It has also
been noted by Olsson (1964; 1968) that there is a distinctive relationship between the fauna of
the Caloosahatchee Formation and the Pinecrest Member, which may be indicative of a
relatively small time gap between deposition of the two units. Based on the proposed chrono-
logic framework suggested, the time interval is less than 0.2 m.y., which is consistent with the
faunal assemblage similarity. In conclusion, the age of the Pinecrest Member of the Tamiami
Formation in core W-16242 correlates with the upper portions of the Tamiami Formation to the
north. The older ages for the member as determined by Jones et al. (1991) would then corre-
late to the age of the underlying Sand Facies of the Tamiami Formation. Edwards et al. (1998)
found that the Tamiami Formation in Collier County was early to late Pliocene in age.






SPECIAL PUBLICATION NO. 49


Caloosahatchee Formation
Information was collected from core W-16242 on the age of the Caloosahatchee Formation.
The strontium-isotope and magnetostratigraphic data show that the age is approximately from
2.14 or 1.77 to 0.6 Ma. This age range is considered to be uncertain because only one stron-
tium-isotope age determination was made and the magnetostratigraphic data are not continuous
to the base of the Caloosahatchee Formation in core W-16242. Further work will be required to
better resolve the age of the Caloosahatchee Formation in core W-16242. Continued study of
this core is merited, because the Caloosahatchee Formation is 11.3 m thick at this location. This
thickness may represent one of the more complete stratigraphic sections for this unit in southern
Florida.
The age of the Caloosahatchee Formation in southern Florida has been open to dispute for
many years. Dall (1892) considered the formation to be Pliocene in age based on the ratio of
extinct verses living species of mollusks. DuBar (1958; 1974) suggested the entire
Caloosahatchee Formation was Pleistocene in age based on the presence of a fossil horse skull,
Equus leidyi (Hay), which was found in the uppermost shell bed. Brooks (1968) and Conklin
(1968) placed the Pliocene-Pleistocene boundary in the middle of the formation based on the
reassignment of some specific lithologic members into the overlying Fort Thompson Formation
and others into the Caloosahatchee Formation. Perkins (1969; 1977) used the mapping of dis-
continuity surfaces to separate the Pleistocene sediments of South Florida and his lowermost
Pleistocene (Q1) surface occurred in the top of the Caloosahatchee Formation. Bender (1973)
used the uranium/helium dating method to determine the age of some corals collected from the
Caloosahatchee Formation. These ages were 1.97 and 1.88 Ma (corrected to time scale of
Berggren et al., 1995). Unfortunately, the corals were not specifically located within the overall
stratigraphic section of the formation, making it quite difficult to interpret the significance of the
ages.
Based on the historic data collected on the formation, the recent data collected by Jones et
al. (1991) from the Sarasota shell pits to the north of the study area, and the data from core W-
16242, the Caloosahatchee Formation is late Pliocene to early Pleistocene in age. The forma-
tion is separated into several depositional sequences by regional disconformities, one of which
is the Pliocene-Pleistocene boundary. This boundary lies at the base of Chron C2r in core W-
16242 at a depth of 19.2 m below surface.

CONCLUSIONS

Strontium-isotope stratigraphy, magnetostratigraphy, carbon and oxygen isotope stratigra-
phy, foraminifera, calcareous nannofossils, and diatoms were collectively used to constrain the
ages of the major lithostratigraphic formations lying from the Suwannee Limestone to land sur-
face in Lee County, Florida. Although this investigation concerning the age of these units may
be the most comprehensive to date, the detailed age ranges of the units cannot be uniformly
applied over the entire platform or even all of the southern part of it. The geometry of the
sediments within each formation and the spacing of time lines was affected by a number of fac-
tors, such as topography of the shelf at the beginning of each depositional episode, the rate of
sedimentation as each depositional environment responded to changes in sea level, and the pat-
tern of erosion during sea level low stands. All of these factors and others cause spatial varia-
tions in the chronostratigraphy of the stratigraphic sequences, as even locally observed in the
variation between the three cores studied in detail. However, because the Florida Platform has
a relatively flat, rather narrow geometry, major sea level events have caused platform-wide dis-
conformities to develop that help constrain the ages of the formations to general ranges in time.
Therefore, the deposition of units, such as the Arcadia Formation, on the southern part of the






FLORIDA GEOLOGICAL SURVEY


platform began at a given point in time and deposition of the same unit in the north-central part
of the platform may not have occurred until later in time or may not have occurred at all. But
the major lithostratigraghic units that can be correlated will have common age constraints within
the framework of the global sea level cycles. The Suwannee Limestone was believed to have
been deposited during the entire Oligocene. Through the work of Hammes (1992), and this
work, it is now clear that deposition of the Suwannee Limestone is restricted to the early
Oligocene.
Hawthorn Group deposition was restricted to the middle Miocene in the past. Based on the
new chronostratigraphic data, it is concluded that deposition of the phosphatic sediments of the
Hawthorn Group began in the late Oligocene and continued into the early Pliocene.
For many years, researchers on Florida geology believed that virtually no deposition
occurred during Pliocene time. It is now verified that deposition of the upper Peace River
Formation, all of the Tamiami Formation, and the lower part of the Caloosahatchee Formation,
were deposited during Pliocene time.
Acknowledgements
Most of the data presented in this paper were obtained for a Ph.D. Dissertation at the
University of Miami (Missimer, 1997) under the direction of Dr. Robert N. Ginsburg. Assistance
in collection of the magnetostratigraphic data was provided by Dr. Donald H. McNeill. The
chronostratigraphic data were reviewed by Dr. Thomas M. Scott, Florida Geological Survey, and
Dr. Gregor Eberli, University of Miami. The strontium isotope data were reviewed by Dr. Peter
Sweet, University of Miami.


REFERENCES

Akers, W. H., 1972, Planktonic foraminifera and biostratigraphy of some Neogene formations,
northern Florida and Atlantic Coastal Plain: Tulane Stud. Geol. Paleontol., v. 9, parts 1-4,
192p.

Akers, W. H., 1974, Age of the Pinecrest Beds, South Florida: Tulane Studies in Geology and
Paleontology, v. 11, no. 2, p. 119-120.

Armstrong, R. L., 1971, Glacial erosion and the variable composition of strontium in seawater:
Nature, Physical Science, v. 230, p. 132-133.

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