Environmental geology and hydrogeology of the Ocala area, Florida ( FGS: Special Publication 31 )

STATE OF FLORIDA
DEPARTMENT OF NATURAL RESOURCES
Tom Gardner, Executive Director

DIVISION OF RESOURCE MANAGEMENT
Jeremy A. Craft, Director

FLORIDA GEOLOGICAL SURVEY
Walter Schmidt, State Geologist and Chief

SPECIAL PUBLICATIOGl HiO 31

ENVIRONMENTAL GEOLOGY AND HYDROGEOLOGY'
OF THE
OCALA AREA, FLORIDA
By
Ed Lane janr R.nal-d W\ Ho-erstiri,-

Published for the

FLORIDA GEOLOGICAL SURVEY

Tallahassee
1991

S.' -, -', -- -'- V ": ; 323' -

FERENCE

REF
FGS
SP
31

TABLE 1

CONVERSION FACTORS AND ABBREVIATIONS

This conversion table is for the convenience of readers who may prefer to use metric units instead
of the English units given in this report.

MULTIPLY

inch (in)
foot (ft)
mile (mi)
gallon (gal)
gallons (gal)
gallons per minute (gallmin)
gallons per minute per foot
[ (gal/min) /ft]
gallons per minute (gpm)
cubic feet per second (cfs)
pound avoirdupois (Ib)
ton, short

25.4
0.3048
1.609
3.785
0.003785
0.06308
0.207

0.0022
449
0.4536
0.9072

TO OBTAIN

millimeter (mm)
meter (m)
kilometer (km)
liter (L)
cubic meter (m3
liter per second (L/s)
liter per second per
meter [ (L/s) I/m]
cubic feet per second (cfs)
gallons per minute (gpm)
kilogram (kg)
megagram (Mg)

Chemical concentrations and water temperatures are given in metric units. Chemical concentra-
tion is given in milligrams per liter (mg/L) or micrograms per liter (ug/L). Milligrams per liter is a unit
expressing the concentration of chemical constituents in solution as weight (milligrams) of solute
per unit volume (liter) of water. One thousand micrograms per liter is equivalent to one milligram per
liter. For concentrations less than 7,000 mg/L, the numerical value is the same as for concentrations
in parts per million.

Water temperature is given in degrees Celsius (OC), which can be converted to degrees Fahrenheit
(F) by the following equation:

(F = 1.8 (oC) + 32.

Sea level: In this report, "sea level" refers to the National Geodetic Vertical Datum of 1929 (NGVD
of 1929) a geodetic datum derived from a general adjustment of the first-order level nets of both
the United States and Canada, formerly called "Mean Sea Level of 1929."

STATE OF FLORIDA
DEPARTMENT OF NATURAL RESOURCES
Tom Gardner, Executive Director

DIVISION OF RESOURCE MANAGEMENT
Jeremy A. Craft, Director

FLORIDA GEOLOGICAL SURVEY
Walter Schmidt, State Geologist and Chief

SPECIAL PUBLICATION NO. 31

ENVIRONMENTAL GEOLOGY AND HYDROGEOLOGY
OF THE
OCALA AREA, FLORIDA
By
Ed Lane and Ronald W. Hoenstine

Published for the

FLORIDA GEOLOGICAL SURVEY

Tallahassee
1991

DEPARTMENT
OF
NATURAL RESOURCES

LAWTON CHILES
Governor

JIM SMITH
Secretary of State

BOB BUTTERWORTH
Attorney General

TOM GALLAGHER
State Treasurer

GERALD LEWIS
State Comptroller

BETTY CASTOR
Commissioner of Education

BOB CRAWFORD
Commissioner of Agriculture

TOM GARDNER
Executive Director

LETTER OF TRANSMITTAL

FLORIDA GEOLOGICAL SURVEY
Tallahassee

June 1991

Governor Lawton Chiles, Chairman
Florida Department of Natural Resources
Tallahassee, Florida 32301

Dear Governor Chiles:

The Florida Geological Survey, Division of Resource Management, Department of Natural
Resources, is publishing as Special Publication No. 31, Environmental Geology and Hydrogeology
of the Ocala Area, Florida, prepared by staff geologists Ed Lane and Ronald W. Hoenstine. This report
presents data on the geology and hydrology of the Ocala area, which is one of the fastest growing
urban areas in Florida. This report is timely because of the growth rate, and the information will be
of significant use to local, county, and state planners, as well as to the private sector. The data will
assist these groups to develop and implement long range plans to effectively manage this growth.

Respectfully,

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

Printed for the

Florida Geological Survey

Tallahassee
1991

ISSN 0085-0640

iv

CONTENTS
Page

Acknow ledgem ents ..................................... ... ...................... vii
Introduction and purpose ................. .................. ...................... 1
Location and transportation ........................................................ 1
C lim ate .......... ...................... ...................................... 1
Map Coverage ............................. ........... ......... ................ 1
Well and locality numbering system ............... ................................ 4
Previous investigations ............................................... .......... 4
G eo log y ............................. ................................ .......... 4
Geom orphology ..... .................. .......... .... ........ ............... 4
G eologic history ............................................. ................... 11
W after Resources ........... ........ ......... .... .... ................... 16
The Hydrologic cycle ........................................................... 16
S surface w after ............. .................................................... 18
A q u ifers ....... .. ............................................................. 23
Floridian aquifer system ...................................................... 23
Intermediate aquifer system ................. ................................ 26
Surficial aquifer system .................... ................ .... ............ 26
Evolution of karst terrain ................... ......... .......... ........ .. 26
Chemical weathering of carbonate rocks .......................................... 26
Karst in the Ocala area ................. ...... .............. . ........... 29
W after quality ............. ...................................................... 29
Potentiom etric surface ........ ......................... ......... ................ 37
W after usage ................ .. . .............................. ................ 37
M mineral resources .................................................. ............... 46
Limestone ............... ..... ....... .. ................................... 46
S and .... .... .................................................. ............. 49
Undifferentiated resources ............ ......................................... 49
Land Use ...................... ................... ..................... 49
Environmental hazards associated with karst .... ................................... 60
Solid w aste disposal ........... ....................... .......................... 65
Sum mary .............. .... . ......... . ....... .............. .......... 69
References .................................. ................................... 70

FIGURES

Figure 1 Location m ap ..... ................................................... 2
Figure 2 Transportation map for Marion County ...................... ............ 3
Figure 3 Average monthly air temperature at Ocala ..................... ....... . 5
Figure 4 Monthly rainfall distribution for Ocala .............. ..................... 6
Figure 5 Annual rainfall for Ocala ................ .............................. 7
Figure 6 Topographic map coverage of Marion County ............................. 8
Figure 7 Locality and well numbering system ................................... 9
Figure 8 Geomorphology of Ocala and Marion County .............................. 10
Figure 9 Terraces and shorelines of Ocala and Marion County ...................... 12
Figure 10 Stratigraphic column. ................................................ 13
Figure 11 Cross section location map ........................... ................ 14
Figure 12 Cross sections A-A' and B-B' ........................ ............... 15
Figure 13 Hydrologic cycle ..................................................... 17
Figure 14 Surface water of Marion County . . .................................... 19

Figure 15 Generalized cross-section showing hydrogeological
features common to the Ocala area ................... ................ 21
Figure 16 Porosity and permeability of granular material ........................... 22
Figure 17 Hydrostratigraphic correlation chart ........................ ........... 24
Figure 18 Drainage well in bottom of a sinkhole .................................. 25
Figure 19 Evolution of karst landscape and underground drainage .................... 27
Figure 20 Karst limestone surface exposed by a flood in Ocala
in 1982 ....... ............. .............................. ......... 30
Figure 21 Solution pipes in Ocala limestone surface ........ .............. ......... 31
Figure 22 Topographic map of the Ocala area....................... ............. 32
Figure 23 Sinkholes in City of Ocala ............................................... 33
Figure 24 Sinkhole in City of Ocala ................ ......... ..................... 33
Figure 25 Sinkhole in City of Ocala ............................................ 34
Figure 26 Sinkhole in City of Ocala .............................................. 34
Figure 27 Location of Ocala Very Intensely Studied Area (VISA) ...................... 38
Figure 28 Potentiometric surface maps of the upper Floridan
aquifer system .............................. ....................... 39-43
Figure 29 Change in potentiometric surface of the upper
Floridan aquifer system from September 1987 to May 1988 .................. 44
Figure 30 Fresh ground and surface water withdrawals .............................. 45
Figure 31 Mineral resources map ................... ........................ 47
Figure 32 Active limestone quarry near Ocala ............... .................... 4E
Figure 33 General soil map of Ocala ...................... ....................... 50
Figure 34 Residential land use ........... ............ ........................... 53
Figure 35 Commercial land use ......... .... ............................... 54
Figure 36 Industrial land use ......... ..... ... ..... ........ ..................... 55
Figure 37 Agricultural land use ............ .......... .. ... ................ 56
Figure 38 Governmental land use ............ ... ......... ................... 57
Figure 39 Institutional land use ........... ....................... ...... 58
Figure 40 Miscellaneous land use ..................... ......................... 5S
Figure 41 Drainage basin of the Oklawaha River with drainage
basins of Silver and Rainbow Springs ........... ......................... 61
Figure 42 Limestone fracture zone enlarged by dissolution of
Ocala Group limestone ................ ........ ....................... 62
Figure 43 Flood waters recharging Floridan aquifer system
through sinkhole, 1982 .................. ...... ................ ....... 63
Figure 44 Graphs showing relationships among rainfall, ground-
water levels in the Floridan aquifer system and
discharge of Silver Springs ............................... ............ 64
Figure 45 Finished cell of the Marion County landfill, 1989 .................. ...... 66
Figure 46 Newly opened cell at the Marion County landfill, 1989 ..................... 67
Figure 47 Leachate holding tank at the Marion County landfill, 1989 .................. 67
Figure 48 Generalized cross section of new cells at the Marion
County landfill, 1989 ........... .. ...................... ............. 68

TABLES

Table 1 Conversion factors and abbreviations ........ . . .. . ..... inside front cover
Table 2 Water quality for Silver Springs for 1946 and 1972 ......................... 20
Table 3 Specific parameters of a well used in DER's ground-
water quality monitoring program at Ocala airport ....................... 35
Table 4 Screen analyses of sand samples ............ . . ... ..... ........... 51

ACKNOWLEDGEMENTS

The authors wish to thank the following people and organizations who gave freely of their time
and information. Their assistance provided a firm foundation for this study. Gary Maddox, Depart-
ment of Environmental Regulation, who provided land use data and water quality data; Earl
Blankenship, Solid Waste Administrator, Marion County Board of Commissioners, for information
on the Marion County landfill; Philip Cosson, Planner, City of Ocala, for statistical data for Ocala;
Dennis G. Thompson, Planning Director, Division of Planning, Marion County Board of Commissioners,
for statistical data on Marion County; the Economic Development Council of Ocala for business and
economic information; and G. C. Phelps, U.S. Geological Survey, for information on the aquifer systems
in the Ocala area. In addition, the authors appreciate the efforts of Ken Campbell, Richard Johnson,
Jim Jones, Ted Kiper, Jackie Lloyd, Frank Rupert, Walter Schmidt, Tom Scott, Steven Spencer, and
Bill Yon in reviewing this report.

SPECIAL PUBLICATION NO. 31

ENVIRONMENTAL GEOLOGY AND HYDROGEOLOGY
OF THE
OCALA AREA, FLORIDA

By
Ed Lane, P.G. #141 and Ronald W. Hoenstine, P.G. #57

INTRODUCTION AND PURPOSE

Florida is experiencing phenomenal population
growth. A significant part of this growth is occur-
ring in the Ocala area, which is one of the fastest
growing urban areas in the nation. Ocala, which
had a 1987 population of 44,980, is projected to
have an annual growth rate of 4.64 percent
through 1995 (Thompson, 1988). Rapid urban
growth places unusual stresses on the environ-
ment due to the demands of energy, construc-
tion, transportation, water supplies, and waste
disposal. This report is designed to help local
governments mitigate the impacts of society's
pressures on the environment.
The principal objectives of this report are to
interpret and summarize available cultural infor-
mation and scientific data. By integrating
cultural, climatological, geological, and hydro-
logical data the report will illustrate the impor-
tance that geology plays in land-use planning for
the Ocala urban area. Graphics are emphasized
as a means of presenting data in a format that
can be readily used by the public, scientists,
planners, water managers, and public policy
makers.

LOCATION AND TRANSPORTATION

The City of Ocala is located in north-central
peninsular Florida, approximately in the center
of Marion County (Figure 1). The air-mile circles
on Figure 1 show that Ocala also lies about
equidistant from both extremes of the state's
extent, from Pensacola in the western panhandle
to Miami near the southern tip of the peninsula.
This central location makes Ocala a natural
hub of Marion County's transportation system
(Figure 2). Several of the state's major roads
pass near or through Ocala: Interstate 75, US 27,
US 41, US 441, US 301, and State Highways 40
and 475. A beltway encircling Ocala utilizing
existing and new roads is currently being

considered. CSX Transportation (formerly the
Seaboard Coast Line Railroad) has several
routes that branch out of Ocala, eventually
connecting to Gainesville, Jacksonville and
points north, and south to Tampa, Orlando, and
Miami. Several airlines have scheduled service
to Ocala Municipal Airport.

CLIMATE

Ocala's location in north-central peninsular
Florida is reflected in its humid, subtropical
climate. Its annual average temperature is
71.10F, varying from low averages of approx-
imately 580F in December and January to high
averages of about 820F during July and August
(Figure 3).
Rainfall distribution for Ocala is shown in
Figures 4 and 5. Summer is the "wet" season,
caused by an increase in thunderstorm activity
(Figure 4). Figure 5 shows substantial fluctua-
tions above and below annual average rainfall,
with the widest extremes for the period occurring
within two years of each other, in 1982 and 1984.
The high rainfall of 1982 was due mainly to a
series of April thunderstorms that struck north
central Florida from Marion County southward
to Brevard County. Hail the size of golf balls
covered the ground in many areas. On April 8,
thunderstorms dropped up to 12 inches of rain
over Marion County, and additional rains of
April 9 produced storm totals up to 20 inches,
causing flooding and 150 sinkholes, with
heaviest damage in the Ocala area (NOAA, 1982).
This incident is discussed in more detail in the
Environmental Hazards section.

MAP COVERAGE

A total of 32 U.S. Geological Survey topo-
graphic maps are required to completely cover
Marion County (Figure 6). These maps, which
were used as base maps to plot field data, are
72 minute quadrangles drawn at a scale of

FLORIDA GEOLOGICAL SURVEY

PENSACOLA

TALLAHASSEE

JACKSONVILLE

PQ)

-N- 0 ,0
i5 o o
I v .

0 25 50 MILES
o SCALE 80 KILOMETERS

200 M1

300 v
&PC7

FGS260291

Figure 1. Location map for Marion County and the City of Ocala. Red circles indicate air-mile distances
from Ocala.

Figure 2. Transportation map for Marion County.

FLORIDA GEOLOGICAL SURVEY

1:24,000. All of the maps have 10-foot land eleva-
tion contour intervals. Also, the other U.S.
Geological Survey maps of the State of Florida,
at scales of 1:100,000, 1:250,000, and 1:500,000
include Marion County. In addition, the Florida
Department of Transportation general highway
map for Marion County was used in plotting
roads and location descriptions. Other maps of
interest covering Marion County and Ocala
include the Florida Geological Survey's Environ-
mental Geology Series: Gainesville (Knapp,
1978), Orlando (Scott, 1978), Daytona Beach
(Scott, 1979), and Tarpon Springs sheets (Deuer-
ling and MacGill, 1981), all 1:250,000 scale. A
mineral resources map of Marion County (Hoen-
stine et al., 1988) is reproduced herein as
Figure 31, at reduced scale.

WELL AND LOCALITY NUMBERING SYSTEM

The well and locality numbering system used
in this report is based on the location of the well
or locality, and uses the rectangular system of
section, township and range for identification
(Figure 7). The number consists of five parts.
These are: 1) prefix letters designating L for
locality, W for well, and Mr for Marion County,
2) the township, 3) the range, 4) the section, and
5) the quarter/quarter location within the section.
The basic rectangle is the township, which is
6 miles on a side and encompasses 36 square
miles. It is consecutively measured by tiers both
north and south of the Florida Base Line, an
east-west line that passes through Tallahassee,
as Township north or south. This basic rectangle
is also consecutively measured both east and
west of the Principal Meridian, a north-south line
that passes through Tallahassee, as Range East
or West. In recording the township and range
numbers, the T is left off the township numbers
and the R is left off the range numbers (e.g.,
17S, 23E). Each township is divided equally into
36 one-mile-square blocks called sections, and
are numbered 1 through 36, as shown on
Figure 7.
The sections are divided into quarters with the
quarters labeled "a" through "d." In turn, each
of these one-quarter sections is divided into
quarters with these quarter/quarter squares
labeled "a" through "d" in the same manner. The
"a" through "d" designation may be carried to
any extent needed.

The location of well W-1762 on Figure 7 would
be in the center of the northwest quarter of the
northwest quarter of Section 28, Township 17
South, Range 23 East, Marion County.

PREVIOUS INVESTIGATIONS

A number of previous studies have been
published on the Ocala area. Many of these
investigations have focused on water resources,
including Anderson and Faulkner (1973), who
conducted a study into the quantity and quality
of the surface water in Marion County. Rosenau
et al. (1977) addressed in general terms the
hydrogeology of Silver Springs and its tributaries;
Miller (1986) published a comprehensive study of
the hydrogeology of the Floridan aquifer system;
and Marella (1988) reported on water use and
trends.
Other studies have been undertaken of a more
general nature. Knapp (1978) presented the
environmental geology of the city of Ocala and
surrounding area in a map format. Hoenstine
et al. (1988) published a map that addressed the
mineral resources of Marion County. Thompson
(1988) compiled statistical data on population,
housing and transportation for Marion County.
The Marion County Planning Department (1988)
developed a future land use plan addressing
major development, urban service, goals, objec-
tives, and policies. The City of Ocala Planning
Department and the Ocala-Marion County Metro-
politan Planning Organization (1988) prepared a
City of Ocala Statistical Profile, including data
on census, utilities, traffic, and other cultural
parameters.

GEOLOGY
GEOMORPHOLOGY

Marion County lies near the north edge of the
central (mid-peninsular) physiographic zone of
White (1970). This zone is characterized by a
series of ridges and valleys trending approx-
imately parallel to the Atlantic Coast. Within this
area, these distinct ridges and valleys comprise
geomorphic subdivisions which are generally
named for nearby towns or geographic areas
(Figure 8).

SPECIAL PUBLICATION NO. 31

90

80

S -.-x AVERAGE 71.1- -

a. 70

60
50

50 ~ -i > C
e L s 4 a -,s c 0 z o

Figure 3. Average monthly air temperature at Ocala for period of record 1951-1986
(NOAA).

FLORIDA GEOLOGICAL SURVEY

- U a. 0 a o
-2 LL 4 Z -R t400 z a

Figure 4. Average monthly rainfall for Ocala for period of record 1951-1986,
showing distribution of summer "wet" season and winter "dry" season (NOAA).

,10

0

5
6-

0

AVERAGE 4.41 7 -

-- 4-

S1 1 -I

20
% ABOVE
Q 10 -
z-
'" NORMAL
-0
. BELOW
. -10 -
4 NORMAL
Iz -20-

SI I I I I I I I I I I I I I I I I I I II I I I I I I I I I I I I i I I I I
1950 1960 1970 1980 1990

Figure 5. Annual rainfall at Ocala for period of record 1951-1986, showing deviation above and below normal
amount (NOAA).

20.65

NORMAL
58 Inch7

-15.22

Figure 6. Topographic map coverage of Marion County, U.S. Geological Survey 7-1/2 minute quadrangles.

SPECIAL PUBLICATION NO. 31

RANGE 23 EAST

6 5 4 3 2 1
7 8 9 10 11 12
18 17 16 15 14 13

19 20 21 22 23 24
30 29 28 27 26 25
31 32 33 34 35 36

SECTION

SECTION

Figure 7. Locality and well numbering system.

VMr-17S-23E-28aa
/ v176a
QbQ lo
C01Cd

28

FLORIDA GEOLOGICAL SURVEY

TSALIA
APOPKA --
PLAIN

Figure 8. Geomorphology of Ocala and
Marion County (modified after White, 1970).

EXPLANATION
CENTRAL HIGHLANDS
I CENTRAL VALLEY
O | MARION UPLAND
S| MOUNT DORA RIDGE
| BROOKSVILLE RIDGE
-- FAIRFIELD HILLS
E OCALA HILLS
1 COTTON PLANT RIDGE
| SUMTER UPLAND
| MARTEL HILL
* WESTERN VALLEY
STSALA APOPKA PLAIN
GULF COASTAL LOWLANDS
DUNNELLON GAP
ST. JOHNS RIVER OFFSET

SPECIAL PUBLICATION NO. 31

Four of these geomorphic subdivisions are
present within the Ocala area. From north to
south these include portions of the Fairfield
Hills, the Central Valley, the Sumter Upland and
the Ocala Hills.
The extreme southern portion of the Fairfield
Hills is present in the north-central part of the
study area. Named for the community of Fair-
field, this geomorphic feature forms an irregular
15 by 20 mile area in northwest Marion County
and is underlain by surface and near-surface
clayey sands and sandy clays of the Hawthorn
Group. Within the Ocala area this feature has
elevations ranging from 75 to 135 feet above
mean sea level (MSL). White (1970) considers the
Fairfield Hills to be remnants of a former upland
surface,
The Central Valley occupies the northeastern,
central, and a portion of the northwestern part
of the study area. This geomorphic feature,
which originates in Alachua County and extends
through east-central Marion County and Lake
County into Orange County, is underlain in the
near-surface by sand with minor amounts of silt
and clay. In contrast to the relatively high eleva-
tions associated with the Fairfield Hills, the
Central Valley ranges in elevation from approx-
imately 50 to 75 feet above MSL in the study
area.
The Sumter Upland, located south of the Fair-
field Hills and the Ocala Hills, occupies the
western third and southeastern part of the study
area. This feature is characterized by sand and
clayey sand hills having elevations ranging from
70 to 150 feet above MSL. This region contains
few lakes or ponds.
The Ocala Hills comprise an elevated area in
the south-central and east-central part of the
study area. Bounded on the north by the Central
Valley and lying within the Sumter Upland, this
feature is a nine-mile-long series of hills trending
southwestward from Ocala. Composed primarily
of clayey sand, these hills have elevations that
range from about 75 to 100 feet above MSL.
White (1970) postulated an origin similar to the
Fairfield Hills.
Superimposed on the present day topography
of Marion County are a series of relict marine ter-
races (Figure 9). Formed during the Pleistocene
Epoch, they reflect higher sea level stands.
Healy (1975) recognized three marine terraces
based on elevation in this part of Marion County.

From highest (oldest) to lowest (youngest) these
include the Sunderland-Okefenokee Terrace (100
to 170 feet above MSL), the Wicomico Terrace
(70 to 100 feet above MSL), and the Penholoway
Terrace (42 to 70 feet above MSL).
The higher Sunderland-Okefenokee Terrace
generally coincides with the Ocala Hills and Fair-
field Hills. The Wicomico Terrace is associated
with the Central Valley and lower elevations of
the Sumter Upland. The Penholoway Terrace is
located in the northeastern part of the study area
in the lower elevations of the Central Valley.
Healy (1975) recognizes the higher Coharie
Terrace (170 to 215 feet above MSL) and two
lower terraces the Talbot Terrace (25 to 42 feet
above MSL) and the Pamlico Terrace (8 to 25 feet
above MSL) as being present in Marion County
outside of the study area (Figure 9).

GEOLOGIC HISTORY

Located in north-central Florida, the study
area is underlain by a thick sequence of
Mesozoic and Cenozoic Era carbonate sedimen-
tary rocks (limestone and dolomite) which are
mantled by siliciclastic sediments composed of
quartz sand, silt, clayey sand and sand. The
carbonate sequence is in turn underlain by
metamorphic basement rocks at a depth of
approximately 4,200 feet below land surface. An
oil test well drilled in 1926 by the Ocala Oil
Corporation eight miles southwest of Ocala
(Florida Geological Survey (FGS) W-18, section
10, Township 16S, Range 20E) encountered a
quartzite mica schist at a depth of 4,100 feet
below land surface.
Much of the stratigraphy (the sequence of
layered rocks and their characteristics) of
western Marion County has been influenced by
the Ocala Platform. This structural feature,
previously called the Ocala Uplift by Puri and
Vernon (1964), was described by them as "... a
gentle anticlinal flexure about 230-miles long
and 70-miles wide exposed near the surface in
west-central Florida." The influence of the Ocala
Platform in Marion County causes the Ocala
Group and Hawthorn Group sediments to occur
at shallow depths in western Marion County
relative to their greater depths in eastern Marion
County. Figure 10 is a generalized stratigraphic
column showing Middle Eocene and younger
sediments present in the Ocala area.

FLORIDA GEOLOGICAL SURVEY

EXPLANATION

I 170'-215' COHARIE TERRACE
E- 100'-170' SUNDERLAND TERRACE (COOKE. 1939)/
OKEFENOKEE TERRACE (MACNEIL, 1950)
EI- 70'-100' WICOMICO TERRACE
S42'-70' PENHOLOWAY TERRACE
E 25'-42' TALBOT TERRACE
10'-25' PAMUCO TERRACE

Figure 9. Terraces and shorelines of Ocala and Marion County
(modified after Healy, 1975).

SPECIAL PUBLICATION NO. 31

SYSTEM SERIES FORMATION

QUATERNARY

TERTIARY

Holocene

Pleistocene

Pliocene

Miocene

Undifferentiated
Sands and
Clays

Cypresshead
Formation

Hawthorn Group

Oligocene absent/

Eocene

Ocala Group

Avon Park
Formation

Figure 10. Stratigraphic column.

Figure 11. Cross section location map.

FEET/METERS
200 -4- 60

40

100--

-20

-0

-20

AVON PARK TD 178' AVON PARK TO 280'
FORMATION FORMATION

VERTICAL EXAGGERATION IS APPROXIMATELY 211 TIMES

FEET/METERS
200 - 60

-40

100--

-100 -- -20

TD 305' TO 400' AVON PARK
FORMATION

Figure 12. Cross sections A-A' and B-B'.

0 4 MILES
I I I I I
0 6 KILOMETERS
SCALE

TD 77'
OCALA GROUP UNDIFFERENTIATED ?_

*5' AVON PARK
FORMATION

0-

-100-

FGS270291

FLORIDA GEOLOGICAL SURVEY

The oldest rocks exposed in Florida are the
Avon Park Formation. These rocks have no
surface occurrences in the study area. They
form part of the Floridan aquifer system in
Marion County and underlie the Ocala Group
limestones.
The oldest rocks exposed in the study area are
the Ocala Group limestones. These rocks,
referred to in this report as the "Ocala Group
Undifferentiated," were deposited approximately
38 to 40 million years ago during the Eocene
Epoch. Marine fossils associated with these
sediments, including foraminifera, mollusks,
bryozoans, and echinoids, are abundant and
indicate that deposition took place in a shallow
marine setting.
The Ocala Group limestone commonly occurs
as a soft, white, fossiliferous limestone. The
occurrence of the distinctive foraminifera genus
Lepidocyclina is common to abundant and often
used as a guide in identifying these sediments.
Within the immediate Ocala area, it is variable
in thickness ranging from less than 50 feet in
FGS well W-1153 (section 30b, Township 15S,
Range 23E) to a maximum observed thickness
of approximately 190 feet in FGS well W-892
(Figures 11 and 12) (section 35, Township 13S,
Range 21 E). Some variations in thickness are a
result of limestone removal through erosional
karst processes, which are discussed in detail
later in this report.
The Hawthorn Group overlies the Ocala Group
limestone in the Ocala area. These sediments,
consisting of interbedded phosphatic clay, sand,
dolomite, and limestone, are undifferentiated in
this report and are referred to in the cross
sections as "Hawthorn Group Undifferentiated"
(Figure 12). These diverse lithologic sediments
were deposited during the Early and Middle
Miocene Epoch.
Common to lithologies within the Hawthorn
Group and an important lithologic guide to its
identification is the presence of phosphate
grains. This constituent, which may comprise
greater than eight percent of the sediment
sample, is generally disseminated throughout
sandy clays and very fine to medium, clayey,
quartz sands and carbonates. The unconformable
boundary between the Hawthorn Group and the
underlying Ocala Group is readily apparent. This
distinctive lithologic boundary presents a sharp

contrast between the common phosphatic sand
present in the lower Hawthorn in the Ocala area
and the richly fossiliferous, white to cream
colored Ocala Group limestone.
The Hawthorn Group has an average thick-
ness of approximately 20 to 30 feet throughout
the study area. Exceptions to this occur due to
the presence of a number of paleosinks in Ocala
limestone in which Hawthorn Group and younger
sediments have filled old, inactive sinkholes.
One such occurrence is FGS W-3889 (section
15dd, Township 15S, Range 24E) which pene-
trated 144 feet of Hawthorn Group sediments
over the Ocala Group.
The Cypresshead Formation is present over
much of the eastern half of Marion County east
of Ocala. This Pliocene-Pleistocene unit, which
overlies the Hawthorn Group, has outcrops in the
Ocala National Forest and in southeastern
Marion County. Lithologically, it consists of an
orange to white, very fine to coarse clayey sand
and some gravel. Highly variable in thickness,
the Cypresshead Formation may reach over 100
feet with even greater thicknesses encountered
in paleosinks.
Sands, silts, clayey sands, and clays, referred
to in this report and cross sections as "Undif-
ferentiated Sands and Clays," form a surface
veneer over most of the study area. In general,
they overlie the Cypresshead Formation in
eastern Marion County and the Hawthorn Group
in the rest of the county. Exceptions occur in
western Marion County where the Hawthorn
Group and Cypresshead Formation are missing,
in which case these sediments directly overlie
the Ocala Group limestone. Typically, these
Pleistocene and Holocene age sediments con-
sist of sand with a clay matrix and occasional
occurrences of quartz pebbles. Figure 12 illus-
trates the variable thickness of these sediments.
Undifferentiated sediments within the study area
are generally less than 10-feet thick.

WATER RESOURCES
THE HYDROLOGIC CYCLE

The hydrologic cycle describes the continuous
movement and interaction of water in all its
phases on, above, and below the earth's surface.
Figure 13 shows the main phases of the
hydrologic cycle in Florida.

Figure 13. Hydrologic cycle, showing its main phases as they occur in Florida.

FLORIDA GEOLOGICAL SURVEY

The hydrologic cycle is driven by the elemental
forces of sunshine and gravity. Figure 13 shows
the paths water may take as it moves through
the hydrologic cycle. Starting at the ocean, the
sun's radiation heats the ocean's surface and
evaporates fresh water, which is carried aloft by
rising convection currents of air, eventually
forming clouds of water vapor. The clouds drop
their moisture as rain, snow, or hail. Under usual
atmospheric conditions some of the precipitation
evaporates before it reaches the ground. After
precipitation reaches the ground, three things
can happen to it: some will evaporate directly
from soil, plants, and free bodies of water, as
evapotranspiration; some may infiltrate the soil
or rocks; and some may run off across the land
surface. The runoff may contribute to normal
surface drainage in the form of streams or lakes,
eventually returning to the ocean to begin the
hydrologic cycle anew.
Water that finds its way underground, however,
will have a more circuitous route before it returns
to the sea. Some water may percolate downward
to recharge ground-water aquifers, then move
laterally until being discharged to stream beds
or in surface or submarine springs. Some under-
ground water may be taken up by plants and
evapotranspired to the atmosphere; some may
be withdrawn by wells for human use. In the
Ocala area, two of the most important paths are
recharge to the ground-water aquifers by infiltra-
tion and recharge through karst features.

SURFACE WATER

Marion County has a number of lakes, ponds
and rivers which are primarily located around the
perimeter of the county (Figure 14). In contrast,
the Ocala area, which is located in west-central
Marion County, has only a few minor surface-
water bodies.
This surface water is comprised of several
lakes, in addition to both natural and man-made
ponds. The lakes, which are small, generally
average between 5 and 20 acres in extent. The
ponds are more numerous and are present
throughout the area. Many of the ponds are
man-made, established as retention ponds or
resulting from mining activity. A number of
limestone quarries in the area have associated
water bodies formed as a result of excavation

that has breached sediments of the Floridan
aquifer system. These quarry ponds are relatively
small, usually less than two acres in area. At
these sites the water level represents the local
potentiometric surface of the Floridan aquifer
system. This is the water level that water would
rise in a tightly cased well that penetrates the
aquifer.
One notable exception to this phenomenon is
Silver Springs. This major spring, which is
located about six miles northeast of Ocala,
forms the headwater of the Silver River, a major
tributary of the Oklawaha River (Figure 14).
Silver Springs forms a large pool measuring
250 feet in diameter at the head of the Silver
River. Here, beneath a limestone ledge, the main
spring flow occurs at a depth of 30 feet from a
cavern mouth measuring five feet in height and
135 feet in width (Rosenau et at., 1977).
Several smaller springs occur along the spring
run out to a distance of 3,500 feet from the main
vent. Measurements of stream flow along the
Silver River indicate that spring flow to the river
is concentrated within this 3,500 feet distance
(Ferguson et al., 1947). Investigations by the U.S.
Geological Survey show that the spring flow
occurs through a system of fractures and
dissolution channels in limestone and dolomite
of the Ocala Group (Rosenau et al., 1977). This
flow is provided from recharge by local rainfall
in an area situated to the north, west and south
of the springs measuring approximately 730
square miles (Faulkner, 1973) (Figures 14 and 41).
Discharge is highly variable and averages 820
cubic feet per second (cfs). Measurements
ranged from a maximum observed discharge of
1,290 cfs recorded in October, 1960 to a
minimum value of 539 cfs measured in May, 1957
(Rosenau et al., 1977).
Water clarity is usually excellent in the pool
and along the run. Water temperature is rela-
tively constant ranging from 23 to 240C (73 and
740F) within a few feet of the surface (Rosenau
et al., 1977).
Analyses of water samples taken by the U.S.
Geological Survey for the years 1946 and 1972
are shown in Table 2. These results show that
the majority of measured parameters including
calcium, magnesium and chlorides have re-
mained relatively consistent over this period. An
exception to this is the nitrates (NO3 as N) which

-N-

0 2 4 MILES
0 3 6 KILOMETERS
SCALE

EXPLANATION

L4AKE
7'" SWAMP

ORANOF ce'~

ORANGE f -
S L4 AKE .

..:.:.:.:.:.. -.- o

4A-srn
/ -(:-

RAINBOW
SPRINGS

FGS050291

SILVER

S/L VA .
SPRINGS

OCALA

72
2~.~.~.
C

.9. 0
%v '^: -j.

.
\ S '/ )J

* i <:. ...

( '-
S.. .. .
C **<- .* :--

2~on
",- ." 0' ,,, ,-',,, <3--

/4* / N o .

Ko o 4'."' 212b :.**

SLAKES K
^ * * ? i.0 ***""

o ,
** i* *

~ a '* ::y-

Figure 14. Surface water of Marion County.

p'
A -'.-. , -.

:::::.t,
%

Z

0,

SAKE
GEORGE

FLORIDA GEOLOGICAL SURVEY

Table 2. Water quality for Silver Springs for 1946 and 1972 (Rosenau et al., 1977).
Units are in milligrams per liter unless otherwise noted.

Date of Collection October 21 September 16
1946 1972

Nitrite (NO2 as N) -- 0.00
Nitrate (NO3 as N) 0.29 2.6
Calcium (Ca) 68 68

Magnesium (Mg) 9.6 9.3
Sodium (Na) 4.0 4.3
Potassium (K) 1.1 .2
Silica (SiO2) 9.2 9.8
Bicarbonate (HCO3) 200 200
Carbonate (CO3) 0 0
Sulfate (SO4) 34 39
Chloride (CI) 7.8 8.0
Fluoride (F) .1 0.2
Nitrate (CO3) 1.3 --
Dissolved solids
Calculated -- 242
Residue on evaporation at 180C 237 246
Hardness as CaCO3 210 210
Noncarbonate hardness as CaCOa -- 42
Alkalinity as CaCO3 -- 170
Specific conductance
(micromhos/cm at 250) 401 420
pH (units) 7.8 8.1
Color (platinum cobalt units) 4 0
Temperature (C) -- 23.5
Turbidity (JTU) -- 0
Biochemical oxygen demand
(BOD, 5-day) -- .1
Total organic carbon (TOC) -- 8,0
Organic nitrogen (N) -- .37
Ammonium (NH4 as N) -- .03
Orthophosphate (P04 as P) -- .14
Total phosphorus (P) -- .14
Strontium (Sr) -- 500 ug/I
Arsenic (As) --0 ug/ll
Cadmium (Cd) -- 0 ug/l
Chromium (Cr6) --0 ug/l
Cobalt (CO) -- 0 ug/l
Copper (Cu) -- 0 ug/l
Lead (Pb) -- 2 ug/l

contaminants

PUMPING

WELL
*r 1;' ''"

-*t "+%

;..1 4 -,

~vI
ATSLL

Floridan aquifer
potentiometric surface

recharge
through recharge by
open sinkhole infiltration

SILVER
SPRINGS

a - ^ J 1 i' L...J

*4
1". -' "" h if. .. --

r-.1. * .. -} i"- -,-
.':ON- TI FLORIDAN

rFLORIDAN
..L ... "* '-i -*-4.-. .-- ~, -.

I

,-H

L rr.. '

-1,;, *--4 -
t* i' *~

AQUIFER SYSTEM
(Ocala Group)
N-
-k
'- i- ..

Figure 15. Generalized cross-section showing hydrogeological features common to the Ocala area. Recharge
to the Floridan aquifer system can occur in several ways: (1) by infiltration from rain through thin, sandy soil
or where limestone crops out at the surface; (2) through sinkholes that breach the confining units; or (3) by drainage
wells. Drainage wells pose a threat to the aquifer due to contaminants in urban runoff. Discharge from the aquifer
is by pumpage or at springs.

mmmmd

I
'" .

FLORIDA GEOLOGICAL SURVEY

aB ....

Figure 16. Porosity and permeability as shown by two examples of a well-sorted granular material,
such as sand. In Figure A the porous and permeable sand is clean with open, interconnected voids
that allow water to move freely. In Figure B the same well-sorted, porous sand is rendered impermeable
to water flow due to the retarding effect of the interstitial material, such as clay (from Lane, 1986).

SPECIAL PUBLICATION NO. 31

shows an increase. This may be attributed to the
effects of intensive agriculture practices, such
as fertilization and spraying, which are used
within the Silver Springs drainage basin.

AQUIFERS

Figure 15 illustrates several hydrogeological
features commonly encountered in Florida sedi-
ments and rocks. This figure particularly applies
to the local conditions in the Ocala area.
All ground water occupies the open spaces,
or pores, that occur in many of the rocks of the
earth's crust. Aquifers are defined as units of
rocks or sediments that yield water in sufficient
quantities to be economically useful for society's
activities.
Porosity and permeability are two fundamen-
tal characteristics of rocks or sediments that
control the quantities of water that they can
store, transmit, or release. Porosity and perme-
ability are intimately related. A porous medium,
such as clean sand or gravel, has voids which
may contain water, as shown in Figure 16.
Permeability is a measure of a porous medium's
ability to allow fluids to move through its pores.
By definition, then, permeability implies that a
rock's pores are interconnected so fluids can
move through them. A clean sand, therefore, is
permeable; water can migrate through it (Figure
16a). Porous rocks are not always permeable,
however. A similar, well-sorted sand may have
its interstices filled with clay, small grains of
organic matter, or some other fine-grained
material, which effectively blocks the free
passage of water (Figure 16b). In this case, the
sand would be classified as impermeable (if only
very small quantities of water could pass
through it).
Limestone, though usually thought of as being
"solid" rock, often has a granular texture and
considerable porosity and permeability, either
primary (developed when the limestone was
deposited) or secondary (developed after deposi-
tion). Ground-water flow through granular and
porous limestone is, therefore, similar to flow
through sand. This is an important concept to
keep in mind during the following discussions of
aquifers and chemical weathering of limestone.

Floridan Aquifer System

The Floridan aquifer system is the principal
source of water for the city of Ocala. Indeed, this
aquifer is the principal artesian aquifer in
Florida, Georgia, Alabama, and South Carolina
(Miller, 1986). Figure 17 correlates the geologic
formations that comprise the Floridan aquifer
system, which includes the Ocala Group and the
Avon Park Formation.
In general, the Ocala Group limestone forms
the top of the Floridan aquifer system. This top
occurs at or near land surface throughout the
Ocala area, creating a matter of environmental
concern. The industrial, commercial, and
residential growth in Ocala brings associated
environmental risks to the extremely fragile
aquifer system. Because of the Floridan aquifer
system's near-surface occurrence in a highly
karstic area, the potential exists for significant
contamination of this system from the flow of
surface waters into the aquifer or from an
accidental spill (Phelps, 1989). Porous surface
sands and numerous sinkholes serve as excellent
conduits for potential pollutants to enter the
aquifer.
Recharge to the Floridan aquifer system in
this area occurs in the form of rainfall and
ground-water inflow from potentiometrically
higher areas immediately to the north and south
(Faulkner, 1973). In addition, recharge occurs via
sinkholes, which are numerous throughout the
area, some of which have drainage wells installed
to control urban runoff (Figures 15 and 18).
Ground-water discharge in and around Ocala
occurs primarily from Silver and Rainbow
Springs.
The water quality of the Floridan aquifer
system is considered excellent for public and
domestic consumption. The water is a hard,
calcium bicarbonate type, commonly free of
bacteriological contamination. The mineral
content usually increases with depth (Faulkner,
1973).
Ocala's public water supply is currently
obtained from a well field consisting of five wells
located in the northeastern part of the city
(section 10bb, Township 15S, Range 22E). These
wells are 24 inches in diameter, have casing
depths ranging from 86 feet to 140 feet below

HYDRO-
STRATIGRAPHIC UNIT GEOLOGIC UNIT SERIES

UNDIFFERENTIATED TERRACE
MARINE AND FLUVIAL DEPOSITS
SURFICIAL AQUIFER
SYSTEM

r-
0

INTERMEDIATE
AQUIFER SYSTEM HAWTHORN GROUP MIOCENE 0
AND 5
INTERMEDIATE
CONFINING UNIT
C:
-C
OCALA GROUP
FLORIDAN AQUIFER EOCENE
SYSTEM AVON PARK FORMATION

FGS010291

Figure 17. Hydrostratigraphic correlation chart (Southeastern Geological Society, 1986).

SPECIAL PUBLICATION NO. 31

* 4K:

Figure 18. City drainage well in bottom of a sinkhole connecting to the upper Floridan
aquifer system. This type of well is used to control flooding by diverting urban runoff
into the cavernous limestone aquifer. Florida Geological Survey photograph.

FLORIDA GEOLOGICAL SURVEY

land surface, and are drilled to depths ranging
from 190 feet to 266 feet below land surface. An
older abandoned well field is located near the
center of the city. Wells in this field now serve
as monitoring wells.
In addition to the Floridan aquifer system, two
other aquifer systems may be present. FGS well
data suggests that a surficial aquifer system and
an intermediate aquifer system may have
sporadic occurrences in the Ocala area, as
discussed below.

Intermediate Aquifer System

An intermediate aquifer system may be present
in isolated pockets of relatively thick deposits
of Hawthorn Group sediments. As cross section
A-A' shows, Hawthorn Group thicknesses may
be as great as 130 feet (W-3889, Figure 12).
Presently, there are no data indicating that either
the surficial or intermediate aquifer systems are
being used as sources of water (Phelps, personal
communication, 1989).

Surficial Aquifer System

When near-surface sand and clay lenses or
beds are arranged so that the units can retain
infiltrated water for a reasonable length of time,
the sediments are included in a shallow aquifer
system (Southeastern Geological Society, 1986).
A surficial aquifer system may be present in
areas having appreciable thicknesses (on the
order of tens-of-feet) of undifferentiated sand
and clay sediments.

EVOLUTION OF KARST TERRAIN

The evolution of any terrain into characteristic
landforms involves weathering and erosional or
accretionary processes: wind, water, frost
heaving, slumping, or wave activity, to name a
few. In most areas, the predominant weathering,
erosional, and transporting agent is water, either
falling, flowing across the land, or circulating
through subsurface rocks.

Ocala lies in a karst terrain, an area charac-
terized by undulating hill and swale topography,
sinkholes, disappearing streams, springs, and
caves. The two things necessary to create karst
are abundant in the area: limestone in the
shallow subsurface and slightly acidic waters to
dissolve it.

CHEMICAL WEATHERING
OF CARBONATE ROCKS

The creation of karst involves the development
of underground drainage systems (Figures 19a,
19b, 19c, 19d). Most chemical erosion processes
that create karst take place unnoticed, under-
ground, and imperceptibly slowly. Over time,
perhaps after thousands of years, evidence of
these persistent processes will occur as the
formation of a sinkhole, a spring, ground sub-
sidence, an influx of muddy water in a well, or
as some other karst phenomenon that may inter-
fere with society's activities.
Chemical weathering is the main erosive pro-
cess that forms karst terrain, in an evolutionary
sequence shown in Figures 19a, 19b, 19c, 19d.
As rain falls, some nitrogen and carbon dioxide
gases dissolve into it, forming a weak acidic
solution. When the water contacts decaying
organic matter in the soil, it can become even
more acidic. When the water contacts limestone,
its corrosive attack begins. All rocks and
minerals are soluble in water to some extent, but
limestone is especially susceptible to dissolu-
tion by acidic water. Limestones, by nature, tend
to be fractured, jointed, laminated, and to have
units of differing texture, all characteristics
which, from the standpoint of percolating ground
water, are potential zones of weakness. These
zones of weakness in the limestone are avenues
of attack that, in time, the acidic waters will
enlarge and extend. Given geologic time, con-
duits will form in the rock and allow water to flow
relatively unimpeded for long distances.
During the chemical process of dissolving the
limestone, the water takes into solution some of
the minerals. The water containing the dissolved
minerals moves to some point of discharge
which may be a spring, a stream bed, the ocean
or a well.

SPECIAL PUBLICATION NO. 31

Figure 19a. Relatively young karst landscape showing underlying limestone beds and sandy over-
burden with normal, integrated surface drainage. Solution features are just beginning to develop
in the limestone (after Lane, 1986).

Figure 19b. Detail of Figure 19a showing early stages of karst formation. Limestone is relatively
competent and uneroded. Chemical weathering is just beginning, with little internal circulation
of water through the limestone. Swales, forming incipient sinkholes act to concentrate recharge
(after Lane, 1986).

FLORIDA GEOLOGICAL SURVEY

c I LSLVLLES1_%E IlI'j< J
Figure 19c. Advanced karst landscape. Original surface has been lowered by solution and ero-
sion. Only major streams flow in surface channels and they may cease to flow in dry seasons.
Swales and sinkholes capture most of the surface water and shunt it to the underground drainage
system. Cavernous zones are well-developed in the limestone (after Lane, 1986).

Figure 19d. Detail of Figure 19c showing advanced stage of karst formation. Limestone has well-
developed interconnected passages that form an underground drainage system, which captures
much or all of prior surface drainage. Overburden has collapsed into cavities forming swales or
sinkholes. Caves may form. Land surface has been lowered due to loss of sand into the limestone's
voids. Silver Spring is an example of a cavernous underwater spring (after Lane, 1986).

SPECIAL PUBLICATION NO. 31

Removal of the rock, with the continuing
formation or enlargement of cavities, can
ultimately lead to the collapse of overlying rocks
or sediments. If the collapse is sudden and com-
plete, an open sinkhole will result, sometimes
revealing the cavity in the rock (Figures 20 and
21). More often, though, debris or water covers
the entrance to subterranean drainage. Partial
subsidence of the overburden into cavities will
form swales at the surface, producing hum-
mocky, undulating topography. By this slow,
persistent process of dissolution of limestone
and subsequent collapse of overburden, the land
is worn down to form a karst terrain.
At some point in this process of dissolution
of underground rocks, any existing surface
drainage system will begin to be transformed
into a dry or disappearing stream system.
Continuing dissolution of the limestone will
create more swales and sinkholes, which will
divert more of the surface water into the under-
ground drainage. Eventually, all of the surface
drainage may be diverted underground, leaving
dry stream channels that flow only during floods,
or disappearing streams that flow down swallow
holes (sink holes in stream beds) and reappear
at distant points to flow as springs or resurgent
streams.

KARST IN THE OCALA AREA

There are a variety of karst features in the
Ocala area. Figure 22 shows the extent to which
the area's topography has been dissected by
karst features. Silver Springs is a spectacular
example of a cavernous spring, as shown in
Figure 19d. It is the source of Silver River, and
a major discharge point for water from the
Floridan aquifer system, with flows ranging from
539 to 1,290 cubic feet per second (834,000,000
to 1,997,000,000 gallons per day) (Rosenau et al.,
1977). These quantities of water can dissolve and
carry away in solution as much as 541 tons of
limestone per day (Lane, 1986), which gives some
idea of the erosive capacity of karst processes.
Sinkholes are common features in the Ocala
area (Figures 23, 24, 25, 26). Sinclair and Stewart
(1985) classify the sinkholes that occur in the
Ocala area as three types: solution, cover-
collapse, and cover-subsidence. In their classi-
fication solution sinkholes occur in areas where
limestone is exposed at land surface or is

covered by thin soil and permeable sand. Under
these conditions the land surface subsides
gradually. The topographic expression of this
type of sinkhole is usually a bowl-shaped depres-
sion that may have ponded water. The rolling,
hill-and-swale topography of the Ocala area is
typical. Cover-collapse sinkholes generally occur
suddenly, in areas where limestone is near the
surface. Sinkhole walls tend to be near-vertical,
exposing limestone in the round solution pipes
that lead to the underground drainage system
(Figures 20 and 21). Cover-subsidence sinkholes
occur where the overburden is relatively perme-
able and poorly cohesive, which characterizes
much of the soil in the Ocala area. In areas of
thick sand cover subsidence may be sudden or
proceed ,slowly over many years, producing
sinkholes only a few feet in diameter and depth.

WATER QUALITY

The Florida Department of Environmental
Regulation (DER) monitors a number of water
wells in Marion County which are part of the
department's statewide ground-water quality
monitoring network. This network is made up of
wells placed in areas assumed to be unaffected
by man at the present time.
One of these wells is located west of the city
of Ocala, at the Ocala Airport (section 19b,
Township 15S, Range 21E). This six-inch well is
drilled to a depth of 90 feet below land surface
into the upper Floridan aquifer system. Table 3
lists the specific parameters.analyzed and their
respective values for this well. All of the values
are within established U.S. Environmental
Protection Agency (EPA) units for potable water.
In addition to the ambient network wells, DER
and the St. Johns River Water Management Dis-
trict (SJRWMD) are in the process of establishing
a Very Intense Study Area (VISA) network within
the city of Ocala. This VISA is located in the east-
central part of the study area (Figure 27) and is
one of five initial VISAs to be established in the
water management district. In contrast to the
ambient wells, which are strategically placed to
monitor unaffected areas whose ground water
is not associated with degradation due to pollu-
tion sources, the VISA wells are intended to
monitor the impact of a potential or confirmed
pollution source on local water quality (based on
land-use activity).

FLORIDA GEOLOGICAL SURVEY

^^, =,.
*'

.' ,- *~( ,' ,:

p.., i -

>' ** s '.

'4

Figure 20. Karst limestone surface exposed by a flash-flood in Ocala in 1982. Note ver-
tical solution pipes. Florida Geological Survey photograph.

SPECIAL PUBLICATION NO. 31

,<*

Figure 21. Close-up of solution pipes in Ocala limestone surface, in the same area as
in Figure 20. Pipes are between one and two feet in diameter. Sinkholes and other karst
surface expressions can appear when such pipes become unplugged of their sediment-
fill. Florida Geological Survey photograph.

; w ., i
ny "

.r TOPO A 0l

and d s s"''1 s nr is5fe ith s'm o3ous
.- .r .6 A .. ..... .
-. 7 f' -,S A"s"' .....
,. F"- F- "*\ "-L. 6- '-, ".! .
. -, t K / '

Figure 22. Topographic map of the Ocala study area showing larger karst features. Hundreds of smaller sinkholes
and depressions do not show at this scale. Contour interval is 25 feet with selected intermediate contours.

SPECIAL PUBLICATION NO. 31

rj
4

Figure 23. Sinkholes in City of Ocala formed during the flood of April 1982. Florida
Geological Survey photograph.

p7 .
* t N ,1
*'f ^ ; - ,4

Figure 24. Sinkhole in City of Ocala formed during the flood of April 1982. Florida
Geological Survey photograph.

FLORIDA GEOLOGICAL SURVEY

I?

,4w~
4,-
it. ~
I- .1 ~

.,; A,

^j

'I;;;
* S.

Figure 25. Sinkhole in City of Ocala
Geological Survey photograph.

formed during the flood of April 1982. Florida

r6
s,

it

*is

A

Figure 26. Sinkhole in City of Ocala formed during the flood of April 1982. Florida
Geological Survey photograph.

34

4

SPECIAL PUBLICATION NO. 31

Table 3. Water quality analysis of Ocala Airport Ground-Water
quality monitor well (sec 19b, Township 15S, Range 21E)
(Dept. of Environmental Regulation data, 1989)

PARAMETER AVERAGE

1, 1, 1 Trichloroethane
1, 1, 2 Trichloroethane
1, 1 Dichloroethene
1, 1 Dichloroethane
1, 2 Dichloroethane
1, 2 Dichlorobenzene
1, 2 Dichloropropane
1, 3 Dichlorobenzene
1, 4 Dichlorobenzene
1122 Tetrachloroethane
Arsenic
Barium
Bicarbonate
Bromoform
Bromomethane
Bromodichloromethane
C1, 3 Dichloropropene
Cadmium
Calcium
Carbonate
Carbon Tetrachloride
Chloromethane
Chloride
Chloroethane
Chlorobenzene
Chloroform
Chromium
Conductivity
Copper
Dibromochloromethane
Dichlorodifluoromethane
Fluoride
Iron
Lead
Magnesium
Manganese
Mercury
Methylene Chloride
Nitrate
pH
Phosphate
Potassium
Selenium
Silver
Sodium

1.0000
1.0000
1.0000
1.0000
1.0000
1.0000
1.0000
1.0000
1.0000
1.0000
0.0020
0.0300
108.0000
1.0000
1.0000
1.0000
1.0000
0.0020
38.3000
0.1000
1.0000
1.0000
3.4000
1.0000
1.0000
1.0000
0.0120
230.0000
0.0130
1.0000
1.0000
0.0460
0.0300
0.0200
1.7600
0.0050
0.0000
1.0000
0.9240
7.4000
0.0810
0.2100
0.0020
0.0080
2.2000

UNITS*

ug/I
ug/I
ug/I
ug/I
ug/I
ug/I
ug/l
ug/I
ug/l
ug/l
mg/I
mg/I
mg/I
ug/I
ug/l
ug/l
ug/l
mg/I
mg/I
mg/I
ug/I
ug/l
mg/I
ug/I
ug/I
ug/I
mg/I
umhos/cm
mg/I
ug/I
ug/l
mg/1
mg/I
mg/I
mg/I
mg/1
mg/I
ug/l
mg/I
s.u.
mg/I
mg/I
mg/I
mg/I
mg/I

FLORIDA GEOLOGICAL SURVEY

PARAMETER AVERAGE UNITS*

Sulfate 8.1400 mg/I
T1, 2 Dichloroethene 1.0000 ug/l
T1, 3 Dichloropropene 1.0000 ug/l
Total Dissolved Solids 157.0000 mg/I
Temperature 24.5000 degree C
Tetrachloroethene 1.0000 ug/l
Total Organic Carbon 13.7000 mg/Il
Trichloroethene 1.0000 ug/l
Trichlorofluoromethane 1.0000 ug/l
Vinyl Chloride 1.0000 ug/I
Zinc 0.0200 mg/I
2, 4, 5-TP 0.0020 ug/l
2, 4-D 0.0050 ug/l
2 Chloroethyl Vinyl Ether 1.0000 ug/l
4, 4'-DDD 0.0100 ug/l
4, 4'-DDE 0.0040 ug/I
4, 4'-DDT 0.0100 ug/l
Aldrin 0.0040 ug/l
Benzene 1.0000 ughl
Chlordane 0.0100 ug/l
Dieldrin 0.0020 ug/l
Endosulfan I 0.0100 ug/l
Endrin 0.0010 ug/l
Ethyl Benzene 1.0000 ug/i
Heptachlor 0.0030 ug/l
Heptachlor Expoxide 0.0800 ug/l
Laboratory pH 7.7700 s.u.
Methoxychlor 0.0100 ug/l
Mirex 0.0010 ug/I
Parathion 0.0100 ug/I
Sulfide 0.1000 mg/I
Toluene 1.0000 ug/l
Toxaphene 0.1000 ug/l
g-BHC 0.0000 ug/l
Gross PCB's 0.0100 ug/l

* ug/l = micrograms per liter
mg/I = milligrams per liter
s.u. = standard units
umhos/cm = micromhos per centimeter

SPECIAL PUBLICATION NO. 31

The Ocala VISA is placed in an area
designated as "mixed urban-light industrial"
covering approximately three square miles. This
VISA will have a number of wells installed to
monitor the local area's water quality. Water
quality from these wells will be compared to that
of nearby wells in the ambient ground-water
quality background network to determine if any
degradation is occurring as a result of land-use
activities within the VISA.

POTENTIOMETRIC SURFACE

Figures 28a-28e show the potentiometric
surface of the upper Floridan aquifer system for
the months of May and September for the years
1978,1980,1982,1984,1986, and 1988(SJRWMD
data). The potentiometric surface is a measure-
ment used by hydrogeologists to show the eleva-
tion or altitude (expressed in feet above mean
sea level) at which water level would stand in
tightly cased wells that penetrate the aquifer.
These contoured data show that Ocala and
surrounding areas have a potentiometric surface
that varies in a narrow range from 40 to 47 feet
above MSL. A maximum value of 47 feet above
MSL was recorded in September 1982 and a
minimum value of 40 feet above MSL was
recorded in May of 1988. This may be attributed
to increased consumption of ground water that
SJRWMD records show occurred over this period
of time.
The potentiometric surface appears to be
relatively stable, having shown minimal varia-
tions over a period of time in which the City of
Ocala has had significant growth. Figure 29
lends support to this observation as the change
in potentiometric surface experienced variations
from minus two feet to plus one foot in the
period from September 1987 to May 1988, similar
to seasonal fluctuations shown for prior years
(Figures 28a, 28b, 28c, 28d, 28e). Approximately
half of the study area experienced a slight rise
in the potentiometric surface, while a large part
of the rest of Marion County had no observed
change.

WATER USAGE

Figure 30 shows the various water usages
from both ground and surface water withdrawals
in the St. Johns River Water Management
District for 1986 (the latest year for which data
are available). These data clearly illustrate the
importance of the Floridan aquifer system, as it
was the source of more than 90 percent of the
ground water withdrawn in the district in 1986.
Thediagrams (Figure 30) show the dominance
of the agricultural sector and to a lesser extent
the public water supply as users of ground water.
Together, these two categories accounted for 73
percent of the ground water withdrawn f-rom the
district in 1986.
The agricultural sector is the largest user of
ground water in Marion County. Within this
category irrigation accounts for the largest
usage. The largest uses of water for irrigation are
field corn followed by improved pastures, golf
course turf grass and sod. In the county, water
withdrawn for these purposes totaled 8.56
million gallons/day from ground water and 2.10
million gallons/day from surface water for the
year 1986. This withdrawal has experienced
fluctuations over time showing a 28 percent
decline for the period 1975 to 1985 and a 22
percent increase from 1985 to 1986. It should be
noted that agricultural water usage is extremely
sensitive to weather conditions and shows the
greatest seasonal variations in withdrawals.
The second largest user of ground water is the
public water supply which accounts for 35 per-
cent of the ground-water usage (Figure 30). The
Floridan aquifer system supplies 100 percent of
the City of Ocala's public water supply and sup-
plies more than 95 percent of the entire district's
public water (SJRWMD data). Specifically, the
City of Ocala withdrew an average of 7.668
million gallons of water per day for this purpose.
This amount is included in the 10.91 million
gallons per day extracted from the Floridan
aquifer system for all of Marion County in 1986.
The public water supply usage in Marion County
increased by 50 percent in the period from 1980
to 1985.

SILVER SPRINGS BLVD FORT KING ST ?
0
M 208 C>
M209 209
M 2052 >/
S_ M 2217

-" \OCALA CITY LIMITS

IM 0 VISA area with monitor well
VS are wt moFGS250291

Figure 27. Location of Ocala Very Intense Study Area (VISA). (St. Johns River Water Management District data).

R 20 E R 21 E R 22 E R 23 E R 24 E R 25 E R 26 E

Figure 28a. Potentiometric surface of the upper Floridan aquifer system in Marion County, May 1978 and September
1978 (unpublished St. Johns River Water Management District data).

T 11 S

T 12 S

T 13 S

T 14 S

T 15 S

T 16 S

T 17 S

R 18 E R 19 E

R 20 E R 21 E R 22 E R 23 E R 24 E R 25 E R 26 E

Figure 28b. Potentiometric surface of the upper Floridan aquifer system in Marion County, May 1980 and September
1980 (unpublished St. Johns River Water Management District data).

11 S

12 S

13 S

14 S

15 S

T 16 S

T 17 S

R 18 E R 19 E

R 20 E R 21 E R 22 E R 23 E R 24 E R 25 E R 26 E

T 11 S

T 12 S

T 13 S

(fl
-a

T 14 S >
r'

r"

T 15S >
-4
z
z
40 0

T 16 S

T 17 S

Figure 28c. Potentiometric surface of the upper Floridan aquifer system in Marion County, May 1982 and September
1982 (unpublished St. Johns River Water Management District data).

R 18 E R 19 E

R 20 E R 21 E R 22 E R 23 E R 24 E R 25 E R 26 E

T 11 S

T 12 S

T 13 S

-n
r-
o
T 14S S

m
0
I-
T 15 S 0

T 16S <

T 17 S

Figure 28d. Potentiometric surface of the upper Floridan aquifer system in Marion County, May 1984 and September
1984 (unpublished St. Johns River Water Management District data),

R 18 E R 19 E

R 20 E R 21 E R 22 E R 23 E R 24 E R 25 E R 26 E

T 11 S

T 12 S

T 13 S

C0

T 15 S >
z
z2
m

T 16 S

T 17 S
r-
-o

r-

T 17 S

Figure 28e. Potentiometric surface of the upper Floridan aquifer system in Marion County, May 1986 and September
1986 (unpublished St. Johns River Water Management District data).

R 18 E R 19 E

R 20 E R 21 E R 22 E R 23 E R 24 E R 25 E R 26 E

T 11 S

S1 T 12 S
4 MILES
KILOMETERS

0
NATION "" .'" T 13 S

-CHANGE T 14 S

T 15S 0

S+ / .

+1 T 1+6 S

T 17S

Figure 29. Change in the potentiometric surface of the upper Floridan aquifer system from September 1987 to
May 1988 (unpublished St. Johns River Water Management District data).

R 18 E R 19 E

SPECIAL PUBLICATION NO. 31

St. Johns River Water Management District

GROUND WATER

Agricultural Irrigation
403.33 Mgal/d
38%

712%

Commercial/Industrial self-supplied
127.96 Mgal/d
Power Generation -
4.71 Mgal/d 0.5%

-\ Public supply
366.52* Mgal/d

Domestic self-supplied
82.33 Mgal/d

Miscellaneous
66.25 Mgal/d

* includes 1.74 Mgal/d of saline ground water.

SURFACE

WATER

Agricultural Irrigation
214.64 Mgal/d
57%

Commercial/Industrial self-supplied
20.50 Mgal/d

Power Generation
129.01 Mgal/d

Public supply
15.47 Mgal/d FGS240291

Figure 30. Fresh ground and surface water withdrawals by category, 1986, in the St. Johns River Water
Management District (after Marella, 1988).

FLORIDA GEOLOGICAL SURVEY

The commerciallindustrial water use in Marion
County (primarily in the study area) increased
from 0.3 to 2.6 million gallons/day between 1975
and 1985. This amounts to a dramatic 780 per-
cent increase, a strong indication of economic
and population growth.
The total extraction of ground water from the
underlying aquifer systems in Marion County for
all uses amounted to 33.36 million gallons/day
for 1986. This total fresh water use in the county,
excluding thermoelectric power generation,
increased by 37 percent in the period from 1975
to 1985 and eight percent from 1985 to 1986.

MINERAL RESOURCES

The following is a general discussion of the
economic geology of the Ocala area. It is not
intended to be a complete investigation leading
to immediate industrial development because,
in many cases, the data represent information
on a single outcrop, pit or mine. However, where
the data are favorable, they may indicate that
certain areas might warrant further investigation
and consideration in land-use planning. Figure
31 is a mineral resource map designed to present
an overview of the major mineral commodities
in and around Ocala (Hoenstine et al., 1988).
Factors such as thickness of overburden as well
as the quality and volume of the deposit will
affect the mining of the mineral commodity at
any specific site. The following is a discussion
of the limestone, sand, and more general undif-
ferentiated resources present in the area.

LIMESTONE

Limestone deposits of considerable economic
value are present in Marion County. Figure 31
shows the distribution of the limestone deposits
in Marion County. High calcium Ocala Group
limestones lie at or near the surface throughout
much of west-central Marion County.
The Ocala Group limestones have been mined
in Marion County for many years as indicated by
the numerous active and inactive quarries
present throughout the county (Figure 31). As a
point of interest, Marion County has one of the

highest concentrations of limestone mines in the
state. These mines are generally confined to the
west-central part of the county. A number of
inactive mines are present in the north-central
portion of Ocala and one active mine is less than
one mile north of the study area (Figure 32).
All companies mining limestone in the county
employ the open pit method for extracting the
rock. This method uses heavy equipment for the
removal of vegetation and overburden prior to
mining a new quarry. The amount of overburden
can vary from a few inches to as much as 50 feet
(Hoenstine et al., 1988). For example, areas in the
southwestern part of Marion County have thick
deposits of overburden which may have potential
as a local source of fill. After clearing the area
to be mined, shot holes are frequently drilled into
the rock and the quarry face is shattered by
blasting. The shattered rock is then loaded by
dragline or front-end loader into trucks and
transported to rock crushers for processing. This
process involves size reduction and subsequent
screening to obtain the various rock size frac-
tions (Campbell, 1986):
The Ocala Group limestones are presently
mined by a number of companies including
Stavola Industries, Boutwell Construction,
Monroe Mines, Ocala Bedrock, and Rainbow
Marion Mines. This limestone is fairly soft and
is removed using bulldozers and front-end
loaders. The depth of mining is dependent on
available equipment. Currently, some companies
are mining limestone from a maximum depth of
65 feet below the water table by dragline. In
many instances, this results in a total mined
section of greater than 100-feet deep.
Limestone has a variety of uses, most of
which are dependent on the specific deposit's
physical properties or chemical composition. In
Marion County, the primary use of the commodity
is for roadbase material with minor amounts
used for agricultural lime and the processing of
glass sand.
Total production and resource estimates of
limerock produced from the Ocala Group in the
area are not available. However, the widespread
occurrence and thickness of the Ocala Group
limestone suggest that these deposits can be
mined for many years.

EXPLANATION
cLA..
*I H [ LIMESTONE

II PETis*oqn
:D AND

* MN-1
1W"

I;

+ t

A. *, I -N-

SI ..-.1

4 1 '1 . r- t ? -

+: ,. k : .. . ....

-'.I Il, t A -..I
I ,- i 'X 1, I '- "-,I. .." ".. .
"- r'- /' -.-,.':--< '. , \

J'/ -\ r I ' ^J- .

l! *II! ; ". x

r 1 .
t -;-- I I I *, I

I, I ( T ; + tI .1 t
/ )- ,- F 1/ . ..- r' ' . .) 1_.-
jIv

.. k I f .

...N, I I I I
XII
I-] I .I--' .

L,. i I *i / r- '- I _.- i ,-i --
~jII

,MINEALRES OUt "CES O
1. I, + -'', +. M I --ER _EO R E OF

MARION COUNTY
FLORIDA
o 88
+ .... + ... + ri .... + .. t + .. r

Figure 31. Mineral resources map of Marion County (Hoenstine et al., 1988).

FLORIDA GEOLOGICAL SURVEY

t- *."

S." 4

Figure 32. Active limestone quarry in Ocala Group limestone, approximately
one mile north of Ocala, T14S, R21E, section 34. Note karst conduit in center
of high wall. Florida Geological Survey photograph.

SPECIAL PUBLICATION NO. 31

SAND

Sand covers much of the eastern third of the
Ocala area. In the topographically low region of
the Central Valley, sand forms a surface veneer
over limestone. Thicker sequences of clayey
sand and sandy clay cap the upland and hill
areas. Thicknesses typically vary from 40 to 60
feet with a maximum thickness of 100 feet pre-
sent to the east of Ocala in the vicinity of the
Ocala National Forest (Cathcart and Patterson,
1983). These fine to coarse-grained sand deposits
are extensive and can be observed in numerous
borrow pits located in the Ocala National Forest.
At present, two commercial and two county road
department operations are located in Marion
County. The Marion County Road Department
maintains two clayey sand pits, which are
located to the southeast of Ocala, one near
Candler (section 26, Township 16S, Range 22E)
and the other one at Celery Farm (section 27,
Township 16S, Range 24E). One of the commer-
cial operations is located in the southeastern
corner of the county (section 19, Township 17S,
Range 26E) and the other near the town of Lynne
(section 3, Township 15S, Range 24E) (Figure 31).
Figure 33 is modified from a United States Soil
Conservation Service (USSCS) map showing part
of the USSCS (1979) soil survey of Marion
County. This survey, which is based on a number
of soil samples taken to a depth of 80 inches,
shows several major soil associations to be
present in and around Ocala. These include the
Astatula and Candler-Apopka soils (well drained
sandy soils), the Arredondo-Gainesville and
Kendrick-Hague-Zuber and Bluff-Martel soils
(sandy to loamy soils), the Sparr-Lochloosa-
Tavares and Eureka-Paisley-Eaton and Lynee-
Pomona-Pompano soils (sandy, loamy to clayey
soils), and the Blichton-Flemington-Kanapaha
soils (sandy, loamy and clayey soils).
This soil survey also provides data on the
general suitability of soils for use as construc-
tion materials. The SCS states that the Astatula
and Candler-Apopka soil associations, which are
present in the southwestern quarter and the
eastern half of the Ocala area, are good sources
of sand (Figure 31).
Several sediment samples were collected in
an area to the east and southeast of Ocala for
testing (Hoenstine et al., 1988). These included
both channel and individual spot samples and

were taken from selected existing pits (Figure 31).
Laboratory procedures involved in analyzing
the samples consisted of drying then quartering
using a riffle type sample splitter. One quarter
was then weighed and screened using a U.S.
Standard Sieve Series. Data obtained are pre-
sented in Table 4 (Hoenstine et al., 1988). This
information can be useful in assessing the
economic potential of these deposits.
Test results indicate that these sands may be
suitable for concrete, brick masonry, sand-
cement riprap, sand-asphalt hot mix and as sand
seal coat. Tests to determine suitability for glass
manufacturing were not made. However, iron
oxide coatings on the sand grains probably
preclude their use for this purpose. Data from
Table 3 represent only one particular set of
samples and does not necessarily depict all
material in a given deposit.

UNDIFFERENTIATED RESOURCES

Much of the surface and near-surface sedi-
ments of the extreme eastern and south-central
portions of the study area are comprised of
clayey sands (referred to on Figure 31 as
"Limited Potential"). This area coincides with
much of the Ocala Hills geomorphic feature. The
heterogeneous nature of these sediments would
tend to preclude their large scale economic
marketability. Locally, however, where costs are
not prohibitive and the need is present for uses
such as top soil or road fill, extraction is feasible.
The possibility is very small that these undif-
ferentiated sediments can be used for large
scale economic or industrial applications.

LAND USE

The University of Florida has developed a com-
puterized data base to identify specific land use
patterns in Florida. These data are based on a
number of sources including municipal and
county property taxes, assessments and plat-
books. Presently, over 100 specific land uses
have been defined, all of which have been
grouped by the Florida Department of Revenue
under one of seven general land use categories.
These seven broad categories are residential,
commercial, industrial, agricultural, governmen-
tal, institutional and miscellaneous.

R21 E

FLORIDA GEOLOGICAL SURVEY

I R22E

R23E

FGS220291
0 2 MILES
I I I' SOIL ASSOCIATIONS
0 3 KILOMETERS
MAINLY EXCESSIVELY DRAINED, NEARLY LEVEL TO STRONGLY SLOPING SOILS OF THE
UPLANDS.
-- ASTATULA association: Nearly level to strongly sloping, excessively drained soils, sandy to a
1 depth of more than 80 inches.
CANDLER-APOPKA association: Nearly level to strongly sloping, excessively drained and well
2l drained sandy soils, some with thin sandy loam lamellae at a depth of 60 to 80 inches and
others loamy at a depth of 40 to 80 inches.
WELL DRAINED, NEARLY LEVEL TO SLOPING SOILS OF THE UPLANDS.
ARREDONDO-GAINESVILLE association: Nearly level to sloping, well drained soils, some sandy
to a depth of more than 40 inches and loamy below and others sandy throughout-
KENDRICK-HAGUE-ZUBER association: Nearly level to sloping, well drained soils, sandy to a
S4 depth of less than 40 inches and loamy or clayey below.
SOMEWHAT POORLY DRAINED AND MODERATELY WELL DRAINED, NEARLY LEVEL TO
SLOPING SOILS OF THE UPLANDS AND FLATWOODS.
I SPARR-LOCHLOOSA-TAVARES association: Nearly level to sloping, somewhat poorly drained
and moderately well drained soils, some sandy to a depth of 20 to more than 40 inches and
loamy below and others sandy throughout.
POORLY DRAINED, NEARLY LEVEL SOILS OF THE FLATWOODS.
LYNNE-POMONA-POMPANO association: Nearly level, poorly drained sols, some sandy to a
S6 I depth of 22 to 80 inches, weakly cemented within a depth of 30 inches, and loamy and clayey
in the lower layers and others sandy throughout.
POORLY DRAINED, NEARLY LEVEL TO STRONGLY SLOPING SOILS OF THE UPLANDS.
W BUCHTON-FLEMINGTON-KANAPAHA association: Nearly level to strongly sloping, poorly
F8 |drained soils, sandy to a depth of less than 20 to more than 40 inches and loamy or clayey
below.
VERY POORLY DRAINED SOILS OF THE FLATWOODS AND FLOOD PLAINS.
BLUFF-MARTEL association: Nearly level, very poorly drained soils, some loamy and clayey
throughout and others loamy in the upper part and clayey within a depth of 20 inches.

Figure 33. General soil map of Ocala study area (after U.S. Soil Conservation Service Soil Survey
of Marion County, 1979).

SPECIAL PUBLICATION NO. 31

Table 4. Screen analyses of sand samples in Marion County, Florida (Hoenstine et al., 1988).

LABORATORY TEST DATA
DEPOSITS SCREEN ANALYSIS
SIEVE NO, AND CUMULATIVE WEIGHT PERCENT RETAINED

SAMPLE NO. (RASEC.) METHOD OF SAMPLING 4 8 16 30 60 100 200 MODULUS

MR-1 16S,24E,22ac CHANNEL 1.070 11.22 44.5680 73.580 94.540 97.560 3.23

MR-2 17S,26E,6ba CHANNEL 0.030 1.520 10.480 28.960 79.460 94.770 2.15

MR-3 15S,24E,14da CHANNEL 1.230 27.080 55.890 84.980 96.690 2.66

MR-4 15S,24E,3do SPOT 0.050 6.300 35.100 56.580 88.050 99.700 2.86

MR-5a 11S,24E,28bd CHANNEL 3.090 12.700 35.570 58.220 90.850 97.990 2.98

MR-5b 118,24E,28bd CHANNEL 6.010 47.880 82.740 94.910 97.800 3.28

MR-6a 12S,24E,20ab CHANNEL 2.080 14.680 42.520 39.080 82.030 94.900 2.95

MR-6b 12S,24E,20ab CHANNEL 0.400 12,870 39.750 52.330 71.910 98.220 2.72

MR-6c 12S,24E,20ab CHANNEL 0.220 3.760 12.030 27.150 76.150 95.540 2.15

*FINENESS MODULUS: A MEANS OF EVALUATING SAND AND GRAVEL DEPOSITS WHICH CONSISTS OF SIEVING SAMPLES THROUGH A STANDARDIZED
SET OF SIEVES, ADDING THE CUMULATIVE WEIGHT PERCENTAGES OF THE INDIVIDUAL SCREENS, DIVIDING BY 100, AND COMPARING THE RESULTANT
FINENESS MODULUS NUMBER TO VARIOUS SPECIFICATION REQUIREMENTS (SATES AND JACKSON, 1980).

FLORIDA GEOLOGICAL SURVEY

Figures 34 through 40 are computer generated,
color-coded illustrations that show either the
number of parcels or the acreage within a sec-
tion (640 acres) which are devoted to the stated
land use. These numbers are based on percen-
tages of the value in the section on the map
which contains the greatest numerical sum (in
parcels of acreage as indicated) of that specific
land use. For example, the section in Marion
County which has the greatest number of
parcels for the residential land use, contains
1,000 parcels (Figure 34). This section is shown
on the map in the same color as the 81 to 100
percent category. The other sections are shown
in colors representing intervals from 1 to 100 per-
cent, based on this 100 percent value of 1,000.
The residential category includes vacant resi-
dential, single family, mobile homes, condo-
miniums and multi-family units. As Figure 34
shows, this category is well represented in the
Ocala area with a number of the sections falling
in the 81 to 100 percent category. The densest
residential areas are located adjacent to the
central part of the city. The lightest residential
development occurs in northwest Ocala. As
would be expected, Ocala, which is the largest
city in Marion County, has the highest concen-
tration of maximum residential values in the
county. Residential housing units in Ocala
totaled 18,871 units, 21.18 percent of the total in
Marion County in 1988 (Thompson, 1988).
The proximity of the Ocala Group limestone
to land surface in the western half of the study
area is a cause for concern when planning
residential development. The presence of a thin
cover of undifferentiated sands and clays and
Hawthorn Group sediments overlying limestone
bedrock in this area is a situation conducive to
the development of sinkholes and potential
structural damage. In addition, the geology of
this area permits easy access of potential con-
taminants to this limestone unit which is the
upper part of the Floridan aquifer system. Exten-
sive use of septic tanks and associated drain
fields here has the potential for significant
degradation of ground-water quality.
Similarly, the surficial aquifer system present
in the thick deposits of Undifferentiated Sands
and Clays in the eastern half of the study area
could experience contamination by residential
developments using drain fields and septic
tanks. Additionally, the use of pesticides and

fertilizers on residential lawns and gardens
could degrade water quality of both the Floridan
aquifer system in the western half of the study
area and the surficial aquifer system in the
eastern half.
The commercial land use classification in-
cludes vacant commercial property, department
stores, supermarkets, regional and community
shopping centers, professional services
buildings, service stations, parking lots,
restaurants, motels, golf courses, and tourist
attractions. Except for the City of Ocala, this
category is lightly represented throughout the
county (Figure 35). The localized commercial ac-
tivity recorded in Ocala is in part a consequence
of the city's rapid development and the diversity
of,services associated with this growth.
Some commercial categories, such as service
stations and large parking lots associated with
malls and supermarkets, pose serious environ-
mental threats to the fragile protection of the
ground water offered by the thin soil cover over
the limestone. Specifically, leaking or improperly
installed underground fuel storage tanks could
cause significant degradation of the limestone
aquifer. This is of special concern in the central
part of Ocala where the highest concentration
of commercial activity occurs (Figure 35). Here,
limestone is near to land surface and the
associated ground water is highly susceptible to
contamination. Also, runoff from improperly
designed parking lots has the potential to
infiltrate surrounding unpaved sediments which,
in eastern and central Ocala, form a thin
permeable cover over the Floridan aquifer
system.
Ocala's industrial complex is similar to the
commercial category in its diversity and concen-
tration in the Ocala area (Figure 36). This activity
includes light manufacturing, heavy equipment
manufacturing, warehousing, canneries, and
lumber yards. The area's large mobile home
manufacturing plants are represented in this
category.
The concentration of industrial activity in cen-
tral and west-central Ocala poses risks similar
to those of commercial activities. The proximity
of the aquifer to land surface in this area and its
susceptibility to contamination requires that
effective procedures involving the usage and
disposal of industrial chemicals must be imple-
mented and strictly monitored.

R 21 E

SCALE
0 2 MILES

0 3 KILOMETERS

R 22 E

1-20

S61 -80

SOCALA

21-40

[ 81-100

R 23 E

-

FGS100291

m- 41-60

NO DATA

Figure 34. Residential land use, 1988. Number of parcels per section, 100% = 1,000 (from Hatchitt, 1989).

p

R 22 E

SCALE
0 2 MILES

0 3 KILOMETERS

L]_ 1-20
1 61-80

I -1 21-40
LI 81-100

A
-N--

ft

FGS110291

11- 41-60
NO DATA

OCALA
Figure 35. Commercial land use, 1988. Number of parcels per section,

100% = 200 (from Hatchitt, 1989).

R 23 E

R 21 E

_ ---1

R 21 E

SCALE
0 2 MILES

0 3 KILOMETERS

R 22 E

1-20

61-80

I 21-40

' 81-100

R 23 E

-- -N-

FGS080291

I NO DATA

OCALA
Figure 36. Industrial land use, 1988. Number of parcels per section, 100% = 100 (from Hatchitt, 1989).

R 22 E

SCALE
0 2 MILES

0 3 KILOMETERS

I 1-20
--1 61-80

___ 21-40
LII 81-100

A
-N-

it

FGS120291

41-60
]NO DATA

SOCALA
Figure 37. Agricultural land use, 1988. Number of parcels per section, 100% = 640 (from Hatchitt, 1989).

R 23 E

R 21 E

R 21 E

SCALE
0 2 MILES

0 3 KILOMETERS

R 22 E

EZI_ 1-20

--':- 61-80

21-40

81-100

R 23 E

-----N-

FGS130291

41-60

LI NO DATA

OCALA
Figure 38. Governmental land use, 1988. Number of parcels per section, 100% = 20 (from Hatchitt, 1989).

R 22 E

SCALE
0 2 MILES

0 3 KILOMETERS

l 1-20
61-80

21-40
81-100

-N-

I

FGS090291

41-60
NO DATA

fl OCALA
Figure 39. Institutional land use, 1988. Number of parcels per section, 100% = 20 (from Hatchitt, 1989).

_ __j

R 23 E

R 21 E

R 22 E

SCALE
0 2 MILES

0 3 KILOMETERS

S1-20

OCALA

SNO DATA

Figure 40. Miscellaneous land use, 1988. Number of parcels per section, 100% = 640 (from Hatchitt, 1989).

-N-

FGS070291

R 23 E

R 21 E

FLORIDA GEOLOGICAL SURVEY

Agriculture is an extremely important compo-
nent of Marion County's economy. In addition to
vegetables, fruit, field crops, and ornamentals,
Marion County is nationally recognized for its
thoroughbred horse farms. Figure 37 shows that
a significant percentage of the county is involved
in agriculture. In contrast, the City of Ocala has
a small amount of agricultural acreage. This may
be reduced in the future as continued growth and
development in the city and the county will
doubtless expand in part at the expense of
agriculture.
Large scale use of pesticides, herbicides, and
fertilizers by the agricultural sector is an ever-
present threat to Ocala's ground-water supply.
Concentrations of agriculture in the north-
eastern part of the study area is of particular
concern as the Floridan aquifer system occurs
almost at land surface there, providing
pollutants easy access to ground water.
As the county seat, Ocala has a number of city
and county government activities. These activi-
ties are part of the governmental category which
includes municipal government facilities (county
and city), public colleges, hospitals and schools
(Figure 38).
The institutional category is well represented
in the Ocala area (Figure 39). It includes
churches, private schools and colleges, private
hospitals, clubs, convalescent homes and
cultural organizations.
The miscellaneous category (Figure 40) is a
general classification. It incorporates everything
not covered by the above categories. These
include such things as railroads, rivers, lakes,
sewage disposal and rights-of-way of streets,
roads, and ditches.

ENVIRONMENTAL HAZARDS
ASSOCIATED WITH KARST

The karst terrain of the study area creates
special conditions that are responsible for most
of the area's environmental hazards, excluding
such weather hazards as hurricanes. The prior
discussion of the evolution of the local karst
terrain pointed out the most important aspect of
karst its underground drainage system. Karst
and its intimate relationship to the area's water

resources dictates, to a large degree, the extent
to which society's activities can stress the
environment and not create problems.
An adequate supply of fresh water is a key-
stone to a high standard of living, for public
water supplies, for industrial demands, and for
agricultural usage, such as irrigation farming.
Because of karst there is very little surface water
available; consequently, most of the area's water
supplies are ground water from the Floridan
aquifer system. Protection of the quality of the
area's ground water must be of paramount con-
cern in any planning, development, or regulatory
context. Special conditions associated with
karst hydrologic systems require special pre-
ca4tions and considerations.
The study area lies wholly within the drainage
basin of Silver Springs. Faulkner (1973) analyzed
regional surface and ground-water levels to
determine the drainage basins of the Oklawaha
River, and Rainbow and Silver Springs (Figure 41).
Note that the springs' drainage basins lie partly
within and partly outside the Oklawaha River's
surface drainage basin divide, which was drawn
along topographic highs. This anomalous situa-
tion is due to karst. The well developed under-
ground drainage for the area provides rapid
recharge to the shallow sand aquifers or to the
limestone aquifer. Many of the sinkholes open
directly into the limestone or they have
permeable sediment fill which allows infiltration.
This situation illustrates the uncertainties in
dealing with ground-water problems in karst
terrain. Relative to the tiny pores in most sandy,
unconsolidated sediments, the karstic porosity
of the Floridan aquifer system's limestones are
megascopic, as shown in Figures 20, 21, and 42.
These cavernous openings in the limestone
permit conduit flow to occur, analogous to flow
in a system of open pipes. Countless sinkholes
in the area provide direct, almost instantaneous,
recharge to the aquifer. Recharge, in this con-
text, refers to water from any source, along with
entrained contaminants, that enter the Floridan
aquifer system. The ability of these avenues of
recharge to accept practically limitless quan-
tities of surface water was dramatically demon-
strated during the flooding of parts of Ocala as
a result of torrential rains in April 1982, when
nearly 12 inches of rain fell in one day (Figure 43).

SPECIAL PUBLICATION NO. 31

OKLAWAHA RIVER / 8 g --
DRAINAGE BASIN / 8 KILOMETERS
BOUNDARY i 0o | MLS I
\ / \ SCALE

rR WNAGE AREA

EXPLANATION SU-MTER CO. LAKE Co.
OKLAWAHARAINBO SPRINGSRvER
Possible seasonal variation in springs BASIN ENDS TO SOU
SS2302LVER SPRINGS
DRAI.IA, NAGAE AREA \ \ \\

EXPLANATION SUMMER CO. '

Spring drainage area boundary
\Okawaha River drainage basin bounder, \\
2.870 square miles. I OKLAWAHA RIVER
Possible seasonal variation in springs BASIN EXTENDS TO SOUTH
drainage basins in this zone.
FGS230291

Ngure 41. Drainage basin of the Oklawaha River with drainage basins of Silver and Rainbow Springs
I Perimposed (modified after Faulkner, 1973).

FLORIDA GEOLOGICAL SURVEY

( 1*-

A

f,
I ., .

4 :' .

,_ *, '- ".

i : ,.. % :

Figure 42. Limestone fracture zone enlarged by solution activity in Ocala Group
limestone. The cavernous opening is about four-feet high by two-feet wide; height
of photograph is about 20 feet. Location is the same as in Figure 32. Florida
Geological Survey photograph.

62

~444

.'" t "-*i.'

SPECIAL PUBLICATION NO. 31

-1;

V-7-p:
.J, "

r=#i

S 4

Figure 43. Flood waters recharging Floridan aquifer system
through a sinkhole that opened up as a result of the April 1982
flood in Ocala. Ocala Group limestone is within two to three feet
of surface here. Florida Geological Survey photograph,

63

51 I .... ...
S3.7 MI. S.E. of OCALA

0 50 I
3
S 49 < -1100
>I R
o I a
48 I Z 1000 0
I- I I w--

47 I 900 0 ,"

>46 0 I ( W
I \ 0
w 45 DISCHARGE OF SILVER SPRINGS 700 0

44 600

0
I [-o 0
15 )
o7 !; MONTHLY RAINFALL AT OCALA' 0
il ^r
z 10 o-
- C

J I ,'

JAN J DEC J D J D J D J D J D
1981 1982 1983 1984 1985 1986

Figure 44. Graphs showing relationships among rainfall, ground-water levels in the Floridan aquifer system and
discharge of Silver Springs. Note that all three graphs display very similar curves, which indicates a strong cause-
effect relationship. Note the very short recharge lag-time (R) between major rainfall events and a rise in the water
level in the Floridan aquifer system well, usually only a few days. The discharge lag-time (D) is longer and represents
the delays due to the water's travel through recharge, storage within the aquifer, and eventual discharge at Silver
Springs; this can vary from a few days to a few weeks. Data from U.S. Geological Survey, Water Resources Data,
1981-1986.

SPECIAL PUBLICATION NO. 31

It is not difficult, therefore, to visualize how
rapidly the cavernous porosity of the aquifer can
transmit recharge through the system, from a
point of entry, such as a sinkhole, to a point of
discharge, such as a well or spring. Conduit flow
would prevail in many cases, with transit times
of only hours or days from point of entry to a
point of discharge that could be several miles
distant. Figure 44 illustrates the two most impor-
tant characteristics of the Floridan aquifer
system's response to hydrologic events in the
Ocala area: (1) rapid recharge to the aquifer
through karst features and thin soil cover over
the limestone, and (2) rapid transit of water
through the aquifer.
Up to a point, the natural workings of Ocala's
hydrologic system can be considered favorable
to society's activities. The area has plenty of
rain, which can be easily recharged to the
aquifer, providing large quantities of fresh water
in storage, which can be easily tapped by wells.
However, when society intrudes with some of its
activities, which do not consider the workings of
the karst hydrology, the results can be environ-
mental problems. Examples of society's stresses
to the karst environment are: large expanses of
pavement and roofs, drainage wells for surface
runoff, some types of agricultural and industrial
practices, and landfills.
Paving and roofing remove large amounts of
land that would otherwise be diffuse recharge
areas, thereby concentrating runoff and recharge
to smaller areas. As urbanization continues, this
has the cumulative effect of concentrating
sources of potential contaminants to the aquifer.
The use of drainage wells to alleviate surface-
water flooding problems also acts to concen-
trate potential contamination to the aquifer
(Figure 18). In urban development plans there is
a need to dedicate more green-belt open areas
to offset the loss of recharge areas.
The over-application of fertilizers, pesticides,
or the use of chemicals that are long-lived or
non-biodegradable, and the over-application of
irrigation water can create sources of contami-
nation. New methods of irrigation, such as
trickle delivery and root delivery, conserve large
quantities of water while at the same time
reducing the build-up of salts in the soil.
Urban growth inevitably brings construction
and service industries, such as gas stations and

merchandisers, or manufacturing plants. With
very few exceptions in the past, most of these
activities have been implicated as sources of
pollution to surface or ground water. Before
operating permits or business licenses are
issued, permitting authorities should require an
inventory of materials to be handled, processed
or dispensed, as well as a plan that adequately
addresses waste disposal practices at each
location.

SOLID WASTE DISPOSAL

Past and current practices of open dumping
and landfilling have been documented as
sources of ground-water pollution in Florida's
karst terrain (Hoenstine et al., 1987). Recent
regulatory and engineering approaches are
designed to prevent contaminants from leaving
the landfills.
Managing solid waste is a monumental task
that faces the nation. In many local areas it has
become a critical task, demanding short-term
solution. To avoid a garbage crisis in the'near
future it will be necessary to change the nation's
attitude towards solid waste disposal, and to
indulge in careful planning based on those
changed attitudes. Instead of a "throw away"
society we must become a "recycle and con-
serve" society.
Realize that the United States generates
between 150-300 million tons of solid waste per
year, about 4 to 8 pounds per person per day.
Florida generates more than 13 million tons of
solid waste per year, about 7 pounds per person
per day. At the Marion County landfill, southeast
of Ocala, the daily input varies from 600-650 tons
per day with peak inputs up to 1,000 tons per
day (Earl Blankenship, Solid Waste Admini-
strator, Marion County landfill, pers. comm.,
1989). This means that, on the average, every
person in Marion County generates from 6.5 to
10.9 pounds of solid waste per day. In recent
years the disposal of these quantities of solid
waste has resulted in a mountain, literally, being
created southeast of Ocala; this truncated pyra-
midal mountain currently has a 10-acre footprint
and rises 90 to 100 feet above the surrounding
flat countryside (Figure 45). Three additional,
similar mountains will rise nearby before the
landfill reaches its planned capacity.

FLORIDA GEOLOGICAL SURVEY

- -rw

or!

Figure 45. Finished cell of the Marion County landfill, view to north. Florida
Geological Survey photograph, February 1989.

.4 K A

SPECIAL PUBLICATION NO. 31

.. : -',] ,a-l u ..** ... -. _. ^ "
.* - *,'A ,

: .? ". ^ - .. . *-- "_ "

Figure 46. Newly opened cell at the Marion County landfill, showing plastic liner on left
and background walls. The liner has been covered with sand on the other two walls for
protection. Note the leachate collection pipes on the left and the 30,000 gallon holding
tank in the left background. View to the south from the top of the recently finished, older
cell, shown in Figure 45. Florida Geological Survey photograph, February 1989.

1 4 ''-
., .-:'* "'" v *

o-if. 'ii~

A-

Figure 47. The 30,000 gallon leachate holding tank at the Marion County landfill, show-
ing some of the pipes that connect to those shown in Figure 46. Florida Geological Survey
photograph, February 1989.

FINISHED, CLOSED CELL --

WALLS OF CELL

TO
HOLDING
TANK
100-MIL
LEACHATE COLLECTION PIPES PLASTIC LINER
ON TOP OF LINER

*:-~ v~ v-.:.:v:: : : :v:;:v::; -.: : :: SAN D . . .
.SAND..-CLA...........

.." -- L.CLAY . . . . . ..- AN
- -- - - - _L
n~-^pp ^ -"Tn~ ~ - - -- -- -- --

OCALA GROUP LIMESTONE
(FLORIDAN AQUIFER SYSTEM)

C

MONITOR WELLS
- AROUND LANDFILL

11

I 'L9

FGS020291

Figure 48. Generalized cross section of new cells at the Marion County landfill, 1989. Not to scale.

S I

SPECIAL PUBLICATION NO. 31

Some of the more obvious problems associ-
ated with the disposal of such huge quantities
of solid waste are: large expenditures by local
governments to operate landfills; landfills are
very difficult to site in a safe environment; and
the available good sites are becoming harder to
find. One of the most important problems with
solid waste disposal is the potential for contami-
nating ground and surface water by biological
and chemical constituents that leach out after
burial.
Federal and state regulatory agencies have
mandated many requirements for operating
landfills to protect the environment. Current
policy towards landfill design is to build facilities
that almost totally isolate the refuse from the
environment. The first of the new cells at the
Marion County landfill, which started operation
in early 1989, incorporates much state-of-the-art
technology to achieve this goal. Present and
future cells have double linings of clay in the
sub-floor, topped by a 100-mil-thick plastic liner
that extends up the sides of the cell (Figure 46),
forming what is, in effect, a liquid-proof con-
tainer in which the solid waste is placed; water
is excluded and leachate is contained. An extra
measure of protection is provided by a leachate
collection system, consisting of a series of
suction pipes laid on top of the liner, and
connected to a 30,000-gallon, fiberglass holding
tank (Figure 47). Should it be necessary, col-
lected leachate may be transported to an off-site
waste-treatment facility. Figure 48 shows these
design features in the new cells.
The older landfill, however, was begun before
the present standards and technology were
available for operating solid waste disposal
facilities. The Florida Department of Environ-
mental Regulation requires all landfill operations
to maintain a system of ground-water monitoring
wells around the facility, and to regularly sample
and test the aquifers, in order to detect any
contamination. As of the date of this report, no
deterioration of ground-water quality has been
detected.

SUMMARY

The data and information in this report
establishes the intimate relationship among
climate, geology, and hydrology of the Ocala
area. There are demonstrated reasons for citi-
zens, planners, and other governmental agencies
to have concerns with regards to past, and future,
industrial, agricultural, and urban development.
Protection of Ocala's ground-water resources
must be a top priority in planning, development,
or regulatory context.
The carbonate rocks of the Floridan aquifer
system occur at or near land surface in the study
area. Their high degree of karstification provides
easy, and rapid; access to the aquifer by rain-
water and any entrained contaminants. Urbani-
zation increases the types and amounts of
contaminants to the aquifer, as well as concen-
trating runoff so that the natural filtering action
of soil overburden is bypassed. Potential threats
to ground-water quality due to urbanization in-
clude improperly installed septic tanks and drain
fields, leaking storage tanks for petroleum or
other chemicals, runoff from paved areas, drain-
age wells, and improper lahdfilling practices.
Agriculture is a major part of the area's
economy. Wide-spread use of chemicals to
increase yields poses a significant threat to the
ground water. Indiscriminant and over-application
of irrigation water increases the possibility of
ground-water contamination.

FLORIDA GEOLOGICAL SURVEY

REFERENCES

Anderson, W., and Faulkner, G. L., 1973, Quantity and quality of surface water in Marion County,
Florida: prepared by the U.S. Geological Survey in cooperation with the Southwest Florida
Water Management District and the Board of County Commissioners of Marion County,
Florida, scale: 4 miles to 1 inch.

Campbell, K. M., 1986, Industrial minerals of Florida: Florida Geological Survey information Circular
102, 94 p.

Cathcart, J, B., and Patterson, S. H., 1983 Mineral resource potential of the Farles Prairie and Buck
Lake roadless areas, Marion County, Florida: U.S. Geological Survey Map Series
MF-1519B.

City of Ocala Planning Department and the Ocala-Marion County Metropolitan Planning Organization,
1988, City of Ocala Statistical Profile, 75 p.'

Deuerling, R. J., and MacGill, P. L., 1981, Environmental geology series, Tarpon Springs sheet: Florida
Bureau of Geology Map Series 99, scale 1:250,000.

Faulkner, G. L., 1973, Geohydrology of the cross-Florida barge canal area with special reference to
the Ocala vicinity: U.S. Geological Survey Water Resources Investigation 1-73, 117 p.

Ferguson, G. E., Lingham, G. W., Love, S. K. and Vernon, R. 0., 1947, Springs of Florida: Florida
Geological Survey Bulletin 31, 198 p.

Hatchitt, J., 1989, Florida summary mapping system (users guide), Armasi, Inc., 17 p.

Healy, H. G., 1975, Terraces and shorelines of Florida: Florida Bureau of Geology Map Series 71,
scale 1:2,000,000.

Hoenstine, R. W., Lane, E., Rupert, F. R., Yon, J.W., Jr., and Spencer, S. M., 1988, Mineral Resources of
Marion County, Florida: Florida Geological Survey Map Series 117, scale: 2 miles to 1 inch.

Lane, E., Spencer, S. M., and O'Carroll, T., 1987, A Landfill site in a karst environment,
Madison County, Florida a case study, in: Proceedings of the 2nd Multidisciplinary Con-
ference on Sinkholes and the Environmental Impacts of Karst, Beck, B. F., and Wilson,
W. L., eds.: Florida Sinkhole Research Institute, University of Central Florida, Orlando,
Florida, p. 253-258.

Knapp, M. S., 1978, Environmental geology series, Gainesville sheet: Florida Bureau of Geology Map
Series 79, scale 1:250,000.

Lane, E., 1986, Karst In Florida: Florida Geological Survey Special Publication 29, 100 p.

Marella, R. L., 1988, Water withdrawals, use and trends in the St. Johns River Water Management
District: St. Johns River Water Management District Technical Publication 88-7, 131 p.

SPECIAL PUBLICATION NO. 31

Marion County Planning Department, 1988, Future land use element, Marion County Comprehensive
Plan, March 1988 draft, 72 p.

Miller, J. A., 1986, Hydrogeologic framework of the Floridan aquifer system in Florida and in parts of
Georgia, Alabama, and South Carolina: U.S. Geological Survey Professional Paper 1403-B,
91 p.

NOAA (National Oceanic and Atmospheric Administration), 1982, Storm Data, v. 24, no. 4, 46 p.

NOAA (National Oceanic and Atmospheric Administration), 1981-1986, Climatological Annual
Summaries, Florida.

Phelps, G. C., 1989, Hydrogeology and effects of selected drainage wells and improved sinkholes on
water quality in the upper Floridan aquifer, Silver Springs Basin, Marion County, Florida:
in Water Resources Activities in Florida, U.S. Geological,Sirvey Open File Report 89-227,
p. 68.

Puri, H. S., and Vernon, R. 0., 1964, Summary of the geology of Florida and a guidebook to the classic
exposures: Florida Geological Survey Special Publication 5 (revised), 312 p.

Rosenau, J. C., Faulkner, G. L., Hendry, C. W., Jr., and Hull, R. W., 1977, Springs of Florida (revised):
Florida Geological Survey Bulletin 31, 461 p.

Scott, T. M., 1978, Environmental geology series, Orlando sheet: Florida Bureau of Geology Map Series
85, scale 1:250,000.

,1979, Environmental geology series, Daytona Beach sheet, Florida Bureau of Geology
Map Series 93, scale 1:250,000.

Sinclair, W. C., and Stewart J. W., 1985, Sinkhole type, development and distribution in Florida: Florida
Bureau of Geology Map Series 110, scale: 30 miles to 1 inch.

Southeastern Geological Society Ad Hoc Committee on Florida Hydrostratigraphic Unit Definition,
1986: Florida Geological Survey Special Publication 28, 8 p.

Thompson, D., 1988, Marion County statistical overview: Marion County Department of Community
Development, 63 p.

U.S. Geological Survey, 1981-1986, Water Resources Data, Florida Surface Water Records and
Groundwater Records, vol. 1, Northeast Florida.

United States Soil Conservation Service, 1979, Soil survey of Marion County area, Florida: U.S.
Department of Agriculture Soil Conservation Service in cooperation with University of
Florida, Institute of Food and Agricultural Sciences, 148 p.

White, W. A., 1970, The geomorphology of the Florida peninsula: Florida Bureau of Geology Bulletin
51, 164 p.

FLORIDA GEOLOGICAL SURVEY
903 W. TENNESSEE STREET
TALLAHASSEE, FLORIDA 32304-7700

Peter M. Dobbins, Admin. Ass
Jessie Hawkins, Custodian

Walter Schmidt, Chief
;t. Al

Vanessa Allred, Library Asst.

ice Jordan, I -.i --.ii-- .
-d'.- Ray, Admin. Secretary

GEOLOGICAL INVESTIGA1IONS 5F.CfOO

Thomas M. Scott, Senior Geologist/Administrator
Jon Arthur, Petrologist Ted ,Yi r-ni .y,-.-
Paulette Bond, Geochemist Nancy LaPlace, ; n-,. Asst.
Dianne Brien, Research Asst. Milena l ,-.:.i, -,: .: ,. Asst
Ken Campbell, Sedimentologist Mel Martinez, Research Asst.
Cindy Collier, Secretary Ted Maul, Research Asst.
Mitch Covington, Biostratigrapher Robert Mince, H s--.,-.h Asst.
Joel Duncan, Sed. Petrologist John Morrill, Driller
Bob Fisher, Research Asst. Larry Papetti, Research Asst.
Rick Green, Research Asst. Albert Phillips, Asst. Driller
Mark Groszos, Research Asst. Frank Rupert, Paleontologist
Kent Hartong, Research Asst. Frank Rush, Lab Tech.
Jim Jones, Cartographer Tom Seal, Research Asct
Clay Kelly, Research Asst.

MINERAL RESOURCE INVESTIGATIONS
AND
ENVIRONMENTAL GEOLOGY SECTION

Jacqueline M. Lloyd, Senior Geologist/Administrator
Ed Lane, Env. Geologist Ron Hoenstine, Env. Geologist
Steve ;Er:'nc -, Economic Geologist

OIL AND GAS SECTION

L. David Curry, Administrator
Brenda Brackin, Secretary Scott Hoskins, Dist. Coordinator
Robert Caughey, Dist. Coordinator Barbara McKamey, Secretary
Joan Gruber, Secretary Marycarol Reily, Geologist
Don Hargrove, Engineer Koren Taylor, Research Asst.
Charles H. Tootle, Pet. Engineer

,.. ..' -. ,
9 ....... ........
96 3 ,-W. L STREET
AliA .: Lvi>, ')F,'

.i,8000014 5370
FlllORIDA uOLOGICAL SURVE
FLORIDA GEOLOGICAL STRVSY

	Front Cover
	Title Page
	Letter of transmittal
	Table of Contents
	Acknowledgement
	Main
	References
	Back Cover

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