Geology of Gulf County, Florida ( FGS: Bulletin 63 )

MISSING IMAGE

Material Information

Title:
Geology of Gulf County, Florida ( FGS: Bulletin 63 )
Series Title:
Bulletin - Florida Geological Survey ; 63
Physical Description:
viii, 51 p. : ill., maps ; 28 cm.
Language:
English
Creator:
Rupert, Frank
Donor:
unknown ( endowment ) ( endowment )
Publisher:
Florida Geological Survey by State of Florida, Dept. of Natural Resources, Division of Resource Management, Florida Geological Survey
Place of Publication:
Tallahassee, Fla.
Publication Date:
Copyright Date:
1991

Subjects

Subjects / Keywords:
Geology -- Florida -- Gulf County   ( lcsh )
Genre:
bibliography   ( marcgt )
government publication (state, provincial, terriorial, dependent)   ( marcgt )
non-fiction   ( marcgt )

Notes

Bibliography:
Includes bibliographical references (p. 46-51).
Statement of Responsibility:
by Frank R. Rupert.

Record Information

Source Institution:
University of Florida
Holding Location:
University of Florida
Rights Management:

The author dedicated the work to the public domain by waiving all of his or her rights to the work worldwide under copyright law and all related or neighboring legal rights he or she had in the work, to the extent allowable by law.
Resource Identifier:
ltuf - AJH1434
alephbibnum - 001758377
oclc - 24529636
lccn - 93620306
issn - 0271-7832 ;
System ID:
UF00000405:00001

Table of Contents
    Front Cover
        Front cover
    Front Matter
        Page i
        Page ii
        Page iii
        Page iv
        Page v
        Page vi
        Page vii
        Page viii
    Main
        Page 1
        Page 2
        Page 3
        Page 4
        Page 5
        Page 6
        Page 7
        Page 8
        Page 9
        Page 10
        Page 11
        Page 12
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        Page 15
        Page 16
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        Page 25
        Page 26
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        Page 31
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        Page 33
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        Page 43
        Page 44
        Page 45
        Page 46
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        Page 48
        Page 49
        Page 50
        Page 51
    Back Cover
        Page 52
        Page 53
Full Text




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









BULLETIN NO. 63


GEOLOGY OF GULF COUNTY. FLORIDA
BY
Frank R. Rupert














Published for the
FLORIDA GEOLOGICAL SURVEY
Tallahassee
1991








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








BULLETIN NO. 63


OF GULF COUNTY, FLORIDA
BY
Frank R. Rupert


Published for the
FLORIDA GEOLOGICAL SURVEY
Tallahassee
1991


Lnj'MVRI Y OF FLORIDA LIBRA.RIES


GEOLOGY





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
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 its Bulletin No. 63, Geology of Gulf County, Florida, prepared by Frank R. Rupert, P.G. This
report fulfills a need for information on the stratigraphy of Gulf County, which is fundamental to ground-
water resource investigations and land use planning. Information on the hydrogeology and mineral
resources is also presented, along with data helpful to other agencies, planners, and the citizens of
Florida.




Respectfully yours,


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







































Printed for the
Florida Geological Survey


Tallahassee
1991


ISSN 0271-7832







iv






CONTENTS


Page
ACKNOW LEDG EM ENTS............................ .... .................................................................................. viii

INTRO DUCTIO N ...................................................................................................................................... 1
Purpose ............................ ............ ..... .......................... .. ........ ................................ 1
Location and Extent............................................................................................................................. 1
Previous Investigations ..................................................................... ...................... .................. 1
M a p s ........................................ .............................................................................. ............................. 4
W ell and Locality Num being System ................................................... ............................ ........... 4
Metric Conversion Factors ............................................................................................................. 4

G EOLOGY.................................... .................. ..................... ....6.... ............. ............................... 6
Geom orphology.................................................................................................................................... 6
Marine Terraces..................................... .................................................................................... 6
St. Joseph Bay and Spit .............................. ........... .................. ...... .. ............. ....................... 10
Stratigraphy ................................... ..... ................... ........ ............................................. 10
Precam brian and Paleozoic Erathems .................................. .. ........ ............ ............................... 14
Unnam ed volcanic and plutonic com plex ...................... ... .................................... 14
Mesozoic Erathem ................................... ................................................................................. 22
M middle Jurassic System .......................................................................................................... 22
Louann Salt ........................... ...................................................................................... 22
Upper Jurassic System ............................................ ....................................... .................... 22
Norphlet Sandstone ....................................................................................................... 22
Sm ackover Form action ................................................................................................... 22
Haynesville Form action ............................................................. ...................................... 23
Cotton Valley Group ................................... ........ .......................................................... 23
Cretaceous System ............................................ ........... ..... ..................................................... 23
Lower Cretaceous unnam ed sandstone and shale ............................................... .......... .. 23
Atkinson Formation........................................................................................................ 23
Upper Cretaceous unnam ed chalk and lim estone............................. ......................... 23
Cenozoic Erathem ...................................................................................................................... 24
Tertiary System ........................................................................................................................... 24
Upper Paleocene and Lower Eocene Series........................ ..... ................................ 24
W ilcox G group Undifferentiated.......................................................................................... 24
M middle Eocene Series ....................................................................................................... 24
Tallahatta and Lisbon Form nations ................................................................................ 24
Upper Eocene Series............................ ................................... ............................... 25
Ocala G group ...................................... ..... ....................................................................... 25
O ligocene Series........................................... ................................................................. 25
Suwannee Limestone .................................................................................. ................. 25
M iocene Series ................................................. ................................................................. 26
Lower M iocene Series ................................... ................................................................ 26
St. M arks/Chattahoochee Form nations ......................... ........... .. ...................... 26
M middle M iocene Series....................................... ............................................................. 27






Bruce Creek Lim estone................................................................................................ 27
M middle M iocene Pliocene Series..................................................................................... 27
Intracoastal Form action ............................................................................................ ...... 27
Upper Pliocene Series ...................................................................................................... 30
"Chipola-like" sedim ents ............................................................................................... 30
Jackson Bluff Form action .......................................................................... ..................... 30
Pleistocene-Holocene Series...................................................................... ...................... 32
Undifferentiated sands and clays ................................. .. ................................... 32
Structure ... ....... ... .... ...... ................................. 32
Apalachicola Em baym ent ............................................... .......... ............ .......................................... 32
G ulf Trough..................................................................................................................................... 34
Chattahoochee Anticline.......................................................................................... .................. 34
Ocala Platform ................................................................................................................................. 34
Peninsular Arch ........................................................................................................... .............. 35
G round water.................................................................................................. ............................... 35
Surficial aquifer system ............................................................................. .................................... 35
Interm ediate confining unit............................................................................................ ............. 35
Floridan aquifer system ...................................................................... ....................................... 37
Potentiom etric surface ................................................. ..................... .......... .............. ............... 37
M mineral Resources ................................................. .. ............................... ......................... .............. 39
Clay.................................................................................................................................................. 39
Lim stone and dolom ite........................................................................ 39
Sand and gravel ... ........... ... .................................... 42
Heavy M minerals ................................................................................................................................ 42
M agnesium com pounds............................................................................................................. 43
Petroleum ................................................................................................................. ................. 43

REFERENCES ......................................................................................................................................... 46


ILLUSTRATIONS
Figure Page
1 G ulf County location m ap... ................................................................. .................................... 2

2 Index to U.S. Geological Survey 7.5 minute topographic quadrangle map coverage of
G ulf County ..... ........ ...................................... 3

3 W ell and locality num being system .............................................. ............................................. 5

4 M arine terrace elevation zones of G ulf County................................. ................. 8

5 Portion of the Overstreet topographic quadrangle map showing relict beach ridges
northeast of Port St. Joe .................................................................................................................. 9

6 Sand dunes on St. Joseph Spit....................................................................... ........... .............. 11

7 Generalized stratigraphic section in G ulf County.................... ......................................................... 12






8 Paleozoic and Mesozoic geologic cross section in Gulf County................................... .......... 13

9 Cenozoic geologic cross section location map ...................................... .................................. 15

10 Geologic cross section A-A'........................................................................................................ 16

11 Geologic cross section B-B'........................................................................................................ 17

12 Geologic cross section C-C'....................................................................................................... 18

13 Geologic cross section D-D'....................................................................................................... 19

14 Geologic cross section E-E'........................................................................................................ 20

15 Geologic cross section F-F' ...................................................................................................... 21

16 Structural contour map of the top of the Bruce Creek Limestone................................................. 28

17 Structural contour map of the top of the Intracoastal Formation................................... .......... 29

18 Structural contour map of the top of the Jackson Bluff Formation .................................. ........... 31

19 Principal subsurface structures of north Florida............................................ ........................... 33

20 Correlation of lithostratigraphic and hydrostratigraphic units in Gulf County ............................... 36

21 Potentiometric surface map of the Floridan aquifer system in Gulf County................................. 38

22 Map showing locations of oil test wells in Gulf County .............................................. ....... .... 44




TABLES
Page

1. Wells and cores referenced in text and cross sections............................................... ............ 7

2. U.S. Bureau of Mines, Gulf County clay sample analyses..................................................... 40

3. Mineralological analysis of heavy concentrate sands from St. Joe Spit, Gulf County ................. 42






ACKNOWLEDGEMENTS


The author wishes to acknowledge a number of individuals for their assistance in the preparation and
review of this report. The staff of the Florida Geological Survey were especially helpful with their com-
ments and suggestions on the content and format. Special thanks are extended to Jon Arthur, Paulette
Bond, Ken Campbell, Mitch Covington, Joel Duncan, Dr. Ron Hoenstine, Ed Lane, Jackie Lloyd, Dr. Walt
Schmidt, Dr. Tom Scott, and Steve Spencer for critical review of the manuscript. Many thanks are due to
Jim Jones and Ted Kiper for their helpful advice and expert preparation of the photo-negatives of the
illustrations used in this study. The author also greatly appreciates the time Mr. Bill Merchant of Basic
Incorporated spent answering questions on the magnesium extraction process.





Bulletin No. 63


GEOLOGY OF GULF COUNTY, FLORIDA
by
Frank R. Rupert, P.G. No. 149


INTRODUCTION AND PURPOSE


Florida's expected rapid population growth
through the year 2000 dictates the need for an
understanding of the geological parameters
affecting intelligent growth planning. Previous
research has provided a good geologic data
base for much of Florida, but information on
many of the state's less-populous counties is
lacking. Consequently, the Florida Geological
Survey is currently undertaking a series of geo-
logical studies of Florida's counties in an attempt
to fill this information void. The purpose of this
report is to present a general overview of the
geology and mineral resources of Gulf County
based on existing literature and well data on file
at the Florida Geological Survey.


LOCATION AND EXTENT

Gulf County was established in 1925 from
what was formerly the southern portion of
Calhoun County. It is situated on the Gulf coast
of the central Florida panhandle (Figure 1). Gulf
County is bounded on the west by Bay County,
St. Joseph Bay, and the Gulf of Mexico, on the
east by Liberty and Franklin Counties, and on the
south by the Gulf of Mexico. The county is irregu-
lar in shape, spanning 22 miles at its widest east-
west dimension, and is approximately 38 miles
north-to-south. The total area is 578 square
miles. Population in 1988 was estimated to be
12,200 (Smith and Bayya, 1989).


PREVIOUS INVESTIGATIONS

A number of authors have referred to the geol-
ogy, geomorphology, and paleontology of Gulf
County and the adjacent Gulf coastal panhandle


area. Only those studies directly concerned with
the geology of Gulf County are mentioned in the
following discussion. Specific works are also ref-
erenced under the applicable sections in the text.
The earliest studies included brief discussions
of the geology and geomorphology of Gulf
County (then southern Calhoun County) in the
early Annual Reports of the Florida Geological
Survey (Sellards and Gunter, 1918; Sellards and
Gunter, 1922). Martens (1928a) discussed the
sand and gravel deposits of Gulf County. The
same year, Martens (1928b) studied the heavy
mineral sands on Cape San Bias and St. Joseph
Spit. The Gulf County area was included in the
statewide report on the geology of Florida by
Cooke and Mossom (1929). Martens (1931)
described the beaches of St. Joseph Spit in his
work on the beaches of Florida. Cole (1938)
examined a Gulf County oil test well as part of a
biostratigraphic study, and Applin and Applin
(1944) included the Gulf County area in a region-
al paleontologic and stratigraphic paper. In his
statewide report on the geology of Florida, Cooke
(1945) discussed the Pleistocene surficial sands
of Gulf County. Toler and Shampine (1962) and
Musgrove et al. (1965; 1968) covered western
Gulf County in a series of Floridan aquifer sys-
tem studies of the Econfina Creek Basin. Stewart
(1962) investigated the Recent sedimentary his-
tory of St. Joseph Bay as a graduate thesis. The
Gulf County area of the panhandle was also
included in the statewide summary of the geolo-
gy of Florida by Puri and Vernon (1964). Chen
(1965) studied three Gulf County oil wells in his
regional lithostratigraphic analysis of Paleocene
and Eocene rocks. Schnable and Goodell (1968)
described the stratigraphy and evolution of Cape
San Bias. A Bouguer Anomaly map of the west-
ern Florida panhandle, including Gulf County,
was produced by Chaki and Oglesby (1972).
Stapor (1973a) included samples from Gulf
County in his granulometric and compositional




Florida Geological Survey


MILES
0 1 2 3 4 5

0 2 4 6 8
012345KILOMETERS
02468
KILOMETERS


Figure 1. Gulf County location map.


0
0-





Bulletin No. 63


R 12W +


R11W +


+ R 9


+ R8W


MILES
0 1 2 3 4 5

0 2 4 6 8
012345KILOMETERS
02461
KILOMETERS


FGS090391


Figure 2. Index to U.S. Geological Survey 7.5 minute topographic quadrangle map
coverage of Gulf County.





Florida Geological Survey


study of heavy minerals in the Apalachicola
region. Von Drehle (1973) investigated the sedi-
mentology and origin of the linear sand bodies in
the Gulf County Canal, and Stapor (1973b) ana-
lyzed the sand budgets for St. Joseph Spit and
Cape San Bias. Pascale (1975) included Gulf
County on a map showing estimated freshwater
aquifer yields statewide. Barnett (1975) dis-
cussed the basement rocks encountered in three
deep Gulf County oil test wells. Huddlestun
(1976; 1984) utilized Gulf County cores in his
stratigraphic study of the central Florida panhan-
dle. Rosenau et al.(1977) briefly discussed
Dalkieth Springs in Gulf County in their report on
the springs of Florida. In a report on the Jurassic
oil potential in the Florida panhandle, Applegate
et al. (1978) included four Gulf County oil test
wells. Schmidt (1978, 1979) addressed the surfi-
cial geology of Gulf County in a pair of environ-
mental geology maps. Barr and Pratt (1981)
reported on Floridan aquifer system drawdown
tests performed in northern Gulf County. As her
Master's thesis, Boiling (1982) provided a com-
prehensive study of the Neogene stratigraphy of
Gulf County. Schmidt et al. (1982) reported on
the Neogene carbonates in the Florida panhan-
dle and included a stratigraphic cross section
through Gulf County. Schmidt (1984) also includ-
ed five geologic cross-sections covering portions
of Gulf County. Wuchang (1985) investigated the
sedimentological character of beach ridges along
the mainland coast of Gulf County, and Barr
(1987) included Gulf County on a potentiometric
surface map of the Florida panhandle.


MAPS


Elevation information and cross-section pro-
files were obtained from the United States
Geological Survey 7.5 minute topographic quad-
rangle maps. Figure 2 illustrates the topographic
map coverage of Gulf County. County base
maps were derived from the Florida Department
of Transportation General Highway Map for Gulf
County.


WELL AND LOCALITY
NUMBERING SYSTEM


The well numbering system used in this study
is that of the Florida Geological Survey (FGS)
well filing system. Each well is identified by a
"W", a dash, and a one-to-five digit accession
number unique to the well.
Wells and locations within the county are plot-
ted according to the township, range, and section
rectangular system. The location coordinates
assigned to each well consist of five parts: The
township number, the range number, the section
number, and two letters representing the quar-
ter/quarter location within the section. The basic
unit of this coordinate system is the township,
which is six miles square (Figure 3). Townships
are numbered consecutively in tiers both north
and south of the Florida Base Line, an east-west
survey line passing through Tallahassee. The
township squares are also assigned Range num-
bers both east and west of the Principal
Meridian, a north-south line also passing through
Tallahassee. Each township square is equally
divided into 36 one- square-mile pieces called
sections. Sections are numbered 1 through 36,
as shown on Figure 3. The sections are in turn
divided into quarters labeled "a" through "d", and
each quarter is further divided into quarters
labeled "a" through "d" in a similar fashion. Figure
3 provides an example of a well located accord-
ing to this system. Table 1 is a list of the wells
referred to in this report, with their elevations,
depths, and locations.


METRIC CONVERSION FACTORS


In order to prevent awkward duplication of par-
enthetical conversion of units in the text of
reports, the Florida Geological Survey has adopt-
ed the practice of inserting a tabular listing of
conversion factors. For readers who prefer metric
units to the customary U.S. units used in this







Bulletin No. 63


W+ R11W + R10W + R9W + R8W


a I b a b
a b b


12
a b a b
c d
-c--d-
c d ce d

W-14719 T7S-R9W-SEC. 12 cd


5 4 3 2

8 9 10 11

17 16 15 14

20 21 22 23

29 28 27 26

32 33 34 35

RANGE 9 WEST


Figure 3. Well and locality numbering system.


R 12
C)

I-
+


FGS070391




Florida Geological Survey


report, the following conversion
vided:


MULTIPLY
feet
inches
inches
miles
sq. miles
tons


0.3048
2.540
0.0254
1.609
2.590
2.205


factors are pro-


TO OBTAIN
meters
centimeters
meters
kilometers
sq. kilometers
metric tons


GEOLOGY
GEOMORPHOLOGY

Gulf County lies within the Gulf Coastal
Lowlands geomorphic province (Puri and
Vernon, 1964). This province is characterized by
generally flat, sandy terrain and extends from the
coast inland to middle Calhoun County, with its
northern limit at approximately 100 feet above
mean sea level (MSL). The inset map on Figure
4 shows the extent of the lowlands in the pan-
handle. The modern Gulf coastline consists of
well-developed quartz sand beaches and spits,
occasionally interrupted by marshy inlets and
coves. Inland, the terrain is comprised of relict
marine terrace deposits, sand dunes, ridges,
bars, and river delta deposits populated largely
by poorly- drained pine flatwoods and swamps.
The Apalachicola River is the largest river in
Gulf County, forming the northern two-thirds of
the eastern county boundary (Figure 1). Most
smaller streams within the county are tributaries
to the Apalachicola River. These include the
Chipola, Brothers, and Jackson Rivers. The
Chipola River flows southward out of Dead Lake
in a meandering course through the low, swampy
floodplain southeast of Wewahitchka; it empties
into the Apalachicola River east of Dalkeith. The
Brothers River originates in eastern Gulf County,
flowing southeastward, then southward to con-
verge with the Apalachicola River east of Indian
Swamp. Forbes Island, a low swampy area dis-
sected by numerous creeks and sloughs, is
formed between the courses of the Brothers and


Apalachicola Rivers. The Jackson River mean-
ders southeastward out of Lake Wimico, and
comprises a leg of the Intercoastal Waterway
between Gulf and Franklin Counties.


Marine Terraces

Superimposed on the flat terrain of the Gulf
Coastal Lowlands are a series of relict marine
beach ridges, bars, spits, dune fields, and low
marine terraces. These terraces are step-like
surfaces representing near-shore depositional
plains developed during former shoreline posi-
tions of high-standing Pleistocene Epoch seas.
Healy (1975) recognized four marine terrace lev-
els in Gulf County based on topographic eleva-
tion. In order of descending elevation, these are
the Penholoway, Talbot, Pamlico, and Silver Bluff
terrace zones. Figure 4 shows the extent of the
elevation zone assigned to each terrace in Gulf
County.
The Penholoway is an east-west trending ter-
race lying between 42 and 70 feet above MSL
elevation. It spans the northwestern edge of Gulf
County in a five-mile wide band, with the eastern-
most end truncated by Dead Lake and the flood
plain of the Apalachicola River.
The Talbot terrace lies between 25 and 42 feet
above MSL. It trends eastward across north-cen-
tral Gulf County in a variable 3 to 7-mile wide
band, roughly paralleling the Penholoway ter-
race. The eastern end of the Talbot terrace, east
of Wewahitchka, is truncated by the swampy
floodplain of the Apalachicola River.
Lying between the 8 and 25 feet MSL eleva-
tions, the Pamlico terrace occupies much of cen-
tral Gulf County and the northern portion of the
Apalachicola River floodplain. Although Healy
(1975) shows this terrace extending northward
along the Apalachicola River into Calhoun
County, fluvial erosion by the river is undoubtedly
responsible for the lower elevations within the
Apalachicola River Valley. The true northern
extent of the Pamlico terrace is, therefore, uncer-
tain.





Bulletin No. 63


Table 1. Wells and cores referenced in text and cross sections.


Well
County number


Gulf


Permit
No.


W-914
W-1098
W-1462
W-1468
W-1469
W-1470
W-3301
W-5710
W-6881
W-12051
W-12509
W-12483
W-12617
W-12649
W-12723
W-1 3249
W-13341
W-14077
W-14173
W-14451
W-14529
W-14533
W-14704
W-14719
W-14746
W-15808


W-13965


Bay


Calhoun W-14125


Location
(T R S 1/4-1/4)


9W
9W
11W
11W
9W
9W
9W
10W
11W
12W
11W
10W
10W
10W
11W
10W
10W
11W
9W
10W
10W
10W
10W
9W
10W
11W


Land surface
elevation
(feet MSL)


22bb
10cc
3bc
25ad
19ad
21cb
33bc
25ba
26bc
14aa
30da
26ad
12ad
2bd
31ad
20bc
20dc
6aa
29aa
22bc
12dc
20da
7ba
12cd
28cb
12da


Total depth
(feet below
land surface)

8,708
5,796
5,025
5,069
5,606
7,255
4,955
578
500
567
13,284
14,290
14,570
395
325
220
13,587
522
13,587
525
300
516
465
282
410
5,656


3S 12W 14bc


3S 10W 19bc





Florida Geological Survey


FGS210391


MILES
0 1 2 3 4 5

0 2 4 6 8
KILOMETERS


ELEVATION
(FT. ABOVE MSL)
SPENHOLOWAY TERRACE (42-70 FT.)

1 TALBOT TERRACE (25-42 FT.)

Z PAMLICO TERRACE (8-25 FT.)

j SILVER BLUFF TERRACE (0-10 FT.)
(Modified after Healy, 1975).


Figure 4. Marine terrace elevation zones of Gulf County.







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FGS010391


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Florida Geological Survey


The Silver Bluff terrace occupies the portion of
Gulf County lying below approximately eight feet
MSL, and extends to the modern Gulf coast. This
includes St. Joseph Spit and a one-quarter mile
wide strip of mainland coastline facing St. Joseph
Bay, as well as most of southeastern Gulf
County. A prominent escarpment separating the
higher Pamlico terrace and the Silver Bluff ter-
race is evident near the coast just west of
Panther Swamp. Relict beach ridges and dune
systems, most likely associated with the Silver
Bluff sea level stand, are common on St. Joseph
Peninsula and throughout the southern portion of
Gulf County. A distinct series of relict ridges and
swales border Panther Swamp, just east and
north of Port St. Joe, subparallel to the modern
shore of St. Joseph Bay. Figure 5 is a portion of
the Overstreet topographic quadrangle map
showing various relict beach ridges northeast of
Port St. Joe.


St. Joseph Bay and Spit

St. Joseph Bay is a non-estuarine lagoon
formed between St. Joseph Spit and mainland
Gulf County. No major streams directly contribute
freshwater to the bay. North to south, St. Joseph
Bay is approximately 11-miles long, and varies
from three to five-miles wide. Water depths within
St. Joseph Bay range from less than five feet at
the southern, enclosed end, to approximately 30
feet near the northern tip of the spit. Bottom sedi-
ments are predominantly sand, with localized
areas of clayey silt, silty sand, clayey sand, and
gravel-sand mixtures (Stewart, 1962).
St. Joseph Spit is an elongate sand body
formed by a bi-directional littoral drift system. The
northern portion of the spit is supplied by a north-
ward transporting system, and Cape San Bias is
fed by a southward transporting drift system
(Stapor, 1973b). St. Joseph Spit is connected to
the mainland by a three- mile-long arm extending
eastward from Cape San Bias. The spit bends
sharply at Cape San Bias, and extends approxi-
mately 15 miles northward in a gentle convex-


seaward arc. Throughout its entire length, the
width of the spit is generally less than one mile. A
series of relict sand beach ridges and intervening
swales trend north-northwest across the spit;
between Cape San Bias and the mainland, the
ridge trend is nearly east-west. These remnant
ridges vary between 10 and 15 feet MSL over
most of the spit. Coastal aeolian dunes, migrat-
ing over these old ridges, may approach eleva-
tions of 50 feet above MSL at the northern end of
the spit (Stapor, 1973b).
A white quartz sand beach, 50 to 100-feet wide
and backed by aeolian dunes (Figure 6), borders
the Gulf side of the spit; a muddy sand beach of
variable width fringes the bay side. The dunes on
the Gulf side typically reach elevations of 30 feet
above MSL. Eagle Harbor, midway along the
spit, forms a natural cove on the bay side. This
feature represents the remains of an ancient
pass which once divided the spit into two islands
(Stapor, 1973b).
While little is known of the pre-Holocene histo-
ry of St. Joseph Spit, observable changes in the
shape of the spit have occurred in historic times.
Stapor (1973b) reviewed the shoreline changes
in the spit derived from old navigation charts dat-
ing from the period 1841 to 1970. Between 1875
and 1970, the west-facing coast of the spit
underwent about 33 feet per year of retreat.
During this same time interval, St. Joseph Point
migrated northward about a mile, and Cape San
Bias moved eastward about half a mile and
developed its prominent southward-jutting spit. A
series of lighthouses constructed between 1847
and 1919 had to be located progressively further
east on the cape as the land migrated eastward
(Stapor, 1973b). The wrecked iron framework of
one lighthouse constructed in 1885 now sits
1000 feet seaward of the modern Cape San Bias
coast.


STRATIGRAPHY

The known sediments underlying Gulf County
range in age from Paleozoic to Holocene.

























CA)





















Figure 6. Sand dunes on St. Joseph Spit (photo by Ken Campbell).





Florida Geological Survey I


i SYSTEM SERIES UNIT GENERAL LITHOLOGY


HOLOCENE
o QUATERNARY YUN FF NTIAT D SA A D LAY ISH-ORANGE TO YELLOWISH BROWN TO LIGHT GREENISH-GRAY
.1 QUATERNARY PLIST OCENE DIFFERENTIATED SAND AND CLAY UFOSSILIFEROUS QUARTZ SANDS CLAYEY SANDS, AND SANDY CLAYS.

JACKSON BLUFF FORMATION HT GRAY TO GRAYIS-BROWN TO GRAYISH-ORANGE, SANDY, CLAYEY
JACKSON BLUFF FORMATION SHELL BEDS, FOSSILIFEROUS CLAYEY SANDS, AND SANDY CLAYS.
PLIO- UPPER "CHIPOLA-LIKE" SEDIMENTS YELLOWISH-GRAY, SLIGHTLY SANDY, FOSSILIFEROUS LIMESTONE
COMMONLY CONTAINING MOLLUSKS, FORAMINIFERA, AND ECHINOIDS.
SCENE INTRACOASTAL FORMATION LIGHT GRAY TO YELLOWISH-GRAY QUARTZ SANDY, GLAUCONITIC,
YI PHOSPHATIC, FOSSILIFEROUS LIMESTONE.
.,- LOWER
.2- 0 UPPER
2 INTRACOASTAL FORMATION LIGHT GRAY TO YELLOWISH-GRAY TO WHITE. QUARTZ SANDY,
O MIOCENE MIDDLE GLAUCONITIC, AND PHOSPHATIC FOSSILIFEROUS LIMESTONE.
N BRUCE CREEK LIMESTONE WHITE TO LIGHT GRAY TO YELLOWISH-GRAY, FOSSILIFEROUS LIMESTONE
N. O CONTAINING FORAMINIFERA, ECHINOIDS, BRYOZOANS, AND MOLLUSKS.
Z LOWER ST. MARKS/CHATTAHOOCHEE FMS. LIGHT GRAY TO WHITE CALCILUTITIC, SLIGHTLY QUARTZ SANDYFOSILIFE
25.2 w TERTIARY ____B OUS UMESTONE AND DOLOMITE OR MOLDIC, RECRYSTALLIZED DOLOMITE.
30. 0 OLIGO- UPPER
SCENE LOWER SUWANNEE LIMESTONE LIGHT GRAY TO ORANGE TO YELLOWISH-GRY, RECRYSTALLIZED
FOSSILIFEROUS DOLOMITE OR DOLOMITIC LIMESTONE.
36.0" mu
UPPER OCALA GROUP DARK GRAY TO BROWN TO DARK BROWN FRAGMENTAL, MICROCRYSTALLINE
394. Cu G FOSSILIFEROUS LIMESTONE AND DOLOMITE.
SEOCENE MIDDLE TALLAHATTALIBON FRMATIONS RAYISH-BROWN, FOSSILIFEROUS, MICROCRYSTALLINE. SOMETIMES
49.0-C ARGILLACEOUS LIMESTONE AND DOLOMITE AND CALCAREOUS SALES.
4 LOWER
WILCOX GROUP UNDIFFERENTIATED- ER LIGHT GRAY TO LIGHT GRAYISH-BROWN, SANDY, CHERTY,
LCOX GROUP UNDIFFERENOCCASIONALLY GLAUCONITIC LIMESTONE.
0.2- PALEO- UPPER
SCENE LOWER
UNNAMED CHALK AND LIMESTONE GREEN TO GREENISH-GRAY CHALKY LIMESTONE AND INTERBEDDEDCAL
UPPER v ACAREOUS SALES CONTAINING FORAMINIFERA AND INOCERAMUS PRISMS.
UPPER
CRETACEOUS ATKINSON FORMATION GREEN TO DRK GREEN FOSSILIFEROUS SALES AND INTERBEDDED
LOWER UNNAMED SANDSTONE AND SHALE RED TO REDDISH-BROWN QUARTZ SANDSTONES AND SHALES.
131
COTTON VALLEY GROUP PURPLE TO RED TO BROWN TO GREEN, SLIGHTLY LIGNITIC, QUARTZ
COTTON__________ VALLSANDSTONES AND MUDSTONES.
HAYNESVILLE FORMATION GRAY AND RED CALCAREOUS SALES, FINE-GRAINED SANDSTONES, AND
O UPPER _____ ANVILL MAIN THIN-BEDDED LIMESTONES.
N SSSMACKOVER FORMATION GRAY TO BROWN LIMESTONES AND INTERBEDDED SHALES AND FINE
O JURASSIC SANDSTONES.
U NORPHLET SANDSTONE RED TO GRAY TO BROWN SANDSTONES, SILTSTONES, SHALLS, AND THIN
1, LIMESTONES, OFTEN CONTAINING CONGLOMERATIC IGNEOUS MATERIAL.
1 U MIDDLE LOUANN SALT VERY PURE TO ANHYDRITIC SALT.
179-
LOWER
UPPER
S TRIASSIC MIDDLE
o, LOWER
PERMIAN
S CARBONIFEROUS
N DEVONIAN
395- 0
435 SILURIAN
50. ORDOVICIAN
CAMBRIAN UNNAMED VOLCANIC AND GRANODIORITE
PLUTONIC COMPLEX
S---7--------------------------
Eu


A ABSENT IN WELLS


FGS160391


Figure 7. Generalized stratigraphic section in Gulf County (modified from Braunstein et al., 1988).








FEET/METERS
BELOW MSL
2000500
2000-1


4000-




6000-




8000-


-1000


*2000


3100 000
10000-


LOCATION MAP


12000-




14000-


-4000


16000-1 5000

VERTICAL EXAGGERATION = APPROXIMATELY 10 TIMES TRUE SCALE


LOWER CENOZOIC UNDIFFERENTIATED


UPPER CRETACEOUS


L,.OWER MEMBERS


UNNAMED CHALK AND LIMESTONE


ATKINSON FORMATION


LOWER CRETACEOUSIUNNAMED SANDSTONE AND SHALE


COTTON VALLEY GROUP



SMACKOVER FM. AYNEggS5LE FORMA ?
PRECAMBRIAN- NORPHLET ?ST... -
CAMBRIAN UNNAMED O LO ..
VOLCANIC/PLUTONIC COMPLEX R LOUANN
SALT PALEOZOIC? PRECAMBRIAN-
MILES QUARTZITE CAMBRIAN
0 1 2 3 4 5 UATZI UNNAMED VOLCANIC
S1 i COMPLEX
0 2 4 6 8 FG110391
KILOMETERS


Figure 8. Paleozoic and Mesozoic geologic cross section in Gulf County.


I


I


m





Florida Geological Survey


Undifferentiated Pleistocene and Holocene
marine terrace sands and alluvium are the only
deposits exposed at the surface.
The subsurface data discussed in this report
was derived from lithologic logs of water and oil
well cuttings and cores on file at the FGS. Figure
7 is a generalized stratigraphic section for Gulf
County.
Thirteen oil test wells penetrated Cretaceous
or older sediments at depths in excess of 3,000
feet. Five of these wells penetrated Jurassic age
section, and of this group, three wells encoun-
tered Lower Mesozoic or Upper Paleozoic base-
ment rock at or near their respective total depths
(up to -14,522 feet MSL). These wells were uti-
lized to construct the deep stratigraphic cross-
section in Figure 8.
Cuttings from water wells and FGS cores
taken in Gulf County provide data on the shallow
stratigraphy. Figure 9 shows the locations of a
series of geologic cross sections (Figures 10
through 15) illustrating the shallow stratigraphy of
the county.


Precambrian and Paleozoic Erathems
Unnamed volcanic and plutonic complex

Relatively little is known about the Paleozoic
rocks underlying the Florida panhandle. Prior to
the advent of plate tectonics theory, the deep
rocks of the Florida platform were traditionally
considered part of the North American craton.
Bullard et al. (1965) presented a novel model
illustrating the probable pre-rift fit of the circum-
Atlantic ocean continents. In this model, the area
of present day Florida fitted closely with what is
now the coast of northwestern Africa. A number
of subsequent authors (including Wilson, 1966;
Cramer 1971 and 1973; Odom and Brown, 1976;
Smith, 1982; Chowns and Williams, 1983;
Dallmeyer, 1987; and Opdyke et al., 1987) have
suggested that the Precambrian and Paleozoic
rocks underlying Florida were originally part of
the African craton. This fragment of African Plate
underlies both the Florida Platform and the


Bahama Platform, and remained accreted to
North America when the continents rifted in mid-
Mesozoic time. This theory is supported by litho-
logic and paleontologic similarities in the
Paleozoic strata from both Florida and the
Morocco-Algeria area of Africa.
Our knowledge of the Precambrian/Paleozoic
rocks of Florida has been obtained from core
chip and cutting samples recovered during the
drilling of deep oil test wells. The Hunt Oil,
International Paper Company No. 30-4 (W-
12509, Permit 746) drilled 386 feet of granodior-
ite in the interval -12,817 to -13,203 feet MSL
(Barnett, 1975). The granodiorite was K-Ar age
dated at 709 +/- 25 million years old (unpub-
lished report, Earth Resource Consultants, Inc.,
in: Arthur, 1988). This well is situated in the
extreme northwestern corner of Gulf County, at
the southern edge of what Barnett (1975)
believed is the upthrown block of a faulted grani-
toid batholith. A limestone facies of the Jurassic
Norphlet Sandstone immediately overlies the
granodiorite (Applegate et al., 1978).
The Charter Exploration and Production
Company, St. Joe Paper Company No. 6 (W-
12617, Permit 762) encountered 65 feet of
coarse quartzite, with a kaolinized weathered
zone at the top, in the interval -14,477 to -14,522
feet MSL (Barnett, 1975). Applegate et al. (1978)
assign this quartzite to the Paleozoic. However,
Barnett (1975) believed these sediments may be
either Mesozoic (Lower Triassic) or Upper
Paleozoic in age. The Jurassic age Smackover
Formation overlies the quartzite in this well.
The southernmost deep oil test well in Gulf
County, the Charter No. 1 St. Joe Paper
Company (W-12483, Permit 670), encountered
36 feet of reddish-brown dacite porphyry at a
depth of -14,228 feet MSL. Barnett (1975) con-
sidered the rocks to be ash fall tuff and of Late
Triassic or Early Jurassic age. Later authors
(Chowns and Williams, 1983; Arthur, 1988) place
the basement rocks of southern Gulf County in
the Late Pre-Cambrian or Early Cambrian based
on radiometric age dates obtained on similar
strata in nearby wells.





Bulletin No. 63


CALHOUN CO.
A
* W--1Qf; a


Figure 9. Cenozoic geologic cross section location map.








A A'


Sn o
oo >

-100 0 aW
98 Lu moj
20-

0 - MSL




310 0 O


-o -

-300 D





-500 r 3 %0 M4LES

-160 0 1 2 3 4 5
04 V0 I I rIF
_o 0 2 4 6 8
-180 0, KILOMETERS
-600
VERTICAL EXAGGERATION IS APPROXIMATELY
175 TIMES TRUE SCALE FGS120391


Figure 10. Geologic cross section A-A'.








B







20 -



0 -0 MSL


-20
-100
-40


-60 S200


-80






-300
-40-


-60-- _200


-80 -

-300
-100


-120 - 400


-140

-500
-160 -


-180 -
-600


-200
VEF
S-700 175


ITICAL EXAGGERATION IS APPROXIMATELY
TIMES TRUE SCALE


FGS200391

MILES
0 1 2 3 4 5

0 2 4 6 8
KILOMETERS


Figure 11. Geologic cross section B-B'.








C C'

o 0)
T- 04

r- in 0



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li
100
20


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-20
-100
-40


-60 - -201
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-80

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-100 -


-120 -4o


-140

-500
-160


-180
-60


-200

-700
VERTIC
175 TIM


BRUCE CREEK LIMESTONE


..1

MARKS FM.


MILES
0 1 2 3 4 5

0 2 4 6 8
012345KILOMETERS
02468
KILOMETERS


'T.D.-4996 FT.


FGS180391


Figure 12. Geologic cross section C-C'.


)


-I
AL EXAGGERATION IS APPROXIMATELY
ES TRUE SCALE


D


0



0






)






Bulletin No. 63


(0
. i
W .

100
20

0 - 0 MSL


-100


-60 -200


-300


- -400


- -500



- -600


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UNDIFFERENTIATED O A LAY




INTRACOASTAL FORMATION



/




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0 1 2 3 4 5
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KILOMETERS
VERTICAL EXAGGERATION IS APPROXIMATELY 175 TIMES TRUE SCALE












Figure 13. Geologic cross section D-D'.


-80-

-100-

-120 -


-140 -


-160 -


-180-




Florida Geological Survey


U-
u.
100




-0 MSL




-100


--300


-120 -400
I--400


-140 -


I ~'"


--500


-180 -600


-200-


MILES SA '
-700 0 1 2 3 4 5
T.D.=
0 2 4 6 8 FGS130391
FGS130391
KILOMETERS
VERTICAL EXAGGERATION IS APPROXIMATELY 175 TIMES TRUE SCALE


Figure 14. Geologic cross section E-E'.


-80


-100


_ .^ 5?wVV





Bulletin No. 63


MILES
0 1 2 3 4 5

0 2 4 6 8
012345KILOMETERS
02468
KILOMETERS


- -700 VERTICAL EXAGGERATION IS APPROXIMATELY 175 TIMES TRUE SCALE


Figure 15. Geologic cross section F-F'.


T
1-



-100




- 0 MSL




- -100


-60 -200


-80 -


-100 -


-140-


-160 -


-300


-120 -400


-500


-1 -t- -600


-200 -




Florida Geological Survey


Mesozoic Erathem

The Mesozoic stratigraphic section underlying
Gulf County is comprised primarily of Jurassic
and Cretaceous age sedimentary rocks and Late
Triassic to Early Jurassic age igneous rocks. As
with the deeper Paleozoic section, our knowl-
edge of Florida's Mesozoic rocks is derived prin-
cipally from deep oil well samples. Prior to the
discovery of the oil-bearing Jurassic Smackover
Formation and Norphlet Sandstone in the early
1970's, most Florida panhandle oil wells were
terminated in Cretaceous sediments. Recent
wells targeting the Norphlet and Smackover have
penetrated most or all of the Mesozoic section,
bottoming in Paleozoic rocks or Jurassic salt.
Figure 8 illustrates the Mesozoic and older
stratigraphy of Gulf County.


Middle Jurassic System
Louann Salt

The oldest Mesozoic rock known in Gulf
County is the Louann Salt. This unit is an evapor-
ite deposit which formed in the great Jurassic
sea that covered much of southeastern North
America. The Louann Salt is characteristically a
pure to anhydritic salt halitee). Halite often under-
goes plastic flow in response to vertical loading
by overburden sediments. This flow is frequently
upward in a plume which displaces the overlying
younger sediments. The numerous subsurface
salt domes occurring in the northern Gulf of
Mexico coastal areas were formed by upward
extrusion of Louann Salt. The existence of such
domes under Gulf County has, to date, not been
determined. In Gulf County, only well W-14173
(Permit 957) bottomed in Louann Salt at a depth
of -14,139 feet MSL.


Upper Jurassic System
Norphlet Sandstone

The Norphlet Sandstone locally overlies the


unnamed volcanic and plutonic rocks and the
Louann Salt. In the Jay trend of northeastern
Santa Rosa County, this unit is a source of natu-
ral gas production. Its lithology consists predomi-
nantly of red to gray to brown sandstones,
conglomerates, siltstones, and shales, represent-
ing paleoenvironments ranging from braided
stream-deltaic to intertidal mudflat to beach
shore-face (Sigsby, 1976). Three deep Gulf
County oil test wells penetrated Norphlet
Sandstone section. The Hunt Oil, International
Paper Co. No. 30-4 (W-12509, Permit 746)
drilled 267 feet of Norphlet Sandstone between -
12,469 and -12,736 feet MSL. The lithology con-
sisted of red to brown sandstones, siltstones,
and shales (Applegate et al., 1978). Similarly, the
Exxon Neal Lumber No. 1 (W-13341, Permit 846)
bottomed out in Norphlet sediments at -13,528
feet MSL after drilling 117 feet of the unit. The
thickest Norphlet section was encountered in the
Mesa Petroleum St. Joe Paper No. 1 (W-14173,
Permit 957), which drilled 676 feet of Norphlet
between -13,463 and -14,139 feet MSL, before
bottoming out in salt. Dip is generally to the
southwest. Throughout Gulf County, the Norphlet
Formation is unconformably overlain by the
Smackover Formation.


Smackover Formation

In contrast to the siliciclastics of the underlying
Norphlet Sandstone, the Smackover Formation is
largely a carbonate unit comprised of marine,
gray to brown limestones, containing occasional
interbedded calcareous shales and fine sand-
stones (Applegate et al., 1978). The Smackover
dips southwestward. It is an important oil-produc-
ing stratum in the Jay trend fields of northwest
Florida. Oil test wells into the Smackover
Formation in Gulf County have to date been
unsuccessful in finding economic quantities of
petroleum.
Five deep oil test wells penetrated Smackover
Formation section in Gulf County (see Figure 8).
Typical of these is the Charter Exploration and





Bulletin No. 63


Production Company No. 6 St. Joe Paper Co.
well (W-12617, Permit 762), which drilled 196
feet of Smackover Formation. In this well, the
lithology was composed of light to dark gray,
micritic limestones, calcareous shales, and fine-
grained calcareous sandstones.
While all oil tests in Gulf County have been
plugged and abandoned, one well had an oil
show in the Smackover section. Well W-12509
(Permit 749), the Hunt Oil International Paper
No. 30-4, in extreme northwestern Gulf County,
discovered non-recoverable oil locked in 163 feet
of Smackover Formation section. The
Smackover lithology in this well is characterized
by brown, low permeability, miliolid and mollus-
can fossiliferous, occasionally dolomitic, tar-
stained limestone and interbedded, unfossilifer-
ous, micritic limestone (Applegate et al., 1978).


Haynesville Formation

The Upper Jurassic Haynesville Formation
immediately overlies the Smackover Formation in
Gulf County. Averaging approximately 300-feet
thick, the Haynesville is comprised of gray and
red, often calcareous shales, a few fine-grained
sandstones, and thin-bedded micritic limestones
(Applegate et al., 1978). Regional dip is to the
southwest.


Cotton Valley Group

Overlying the Haynesville Formation is a thick
sequence of varicolored lignitic mudstones and
coarse sandstones known as the Cotton Valley
Group. These siliciclastic sediments typically
range from red to purple to brown, and some-
times green in color (Applegate et al., 1978). In
Gulf County, the Cotton Valley Group varies from
about 1,800 to 2,600-feet thick. It generally thick-
ens to the southwest (basin-ward). The top of the
unit varies from approximately -10,000 to -12,000
feet MSL, with a gentle southwest dip.


Cretaceous System
Lower Cretaceous unnamed
sandstone and shale

The Lower Cretaceous of Gulf County is repre-
sented by a thick sequence of undifferentiated
reddish and reddish-brown interbedded shales
and sandstones. These sediments dip and thick-
en towards the southwest, and range from about
4,800 to 5,600 feet thick under Gulf County. They
are differentiated from the overlying Atkinson
Formation sediments primarily on the basis of
color (Applegate et al., 1978).


Atkinson Formation

The Upper Cretaceous Atkinson Formation is
the Florida panhandle stratigraphic equivalent of
the Tuscaloosa Formation of Alabama
(Braunstein et al., 1988). It is generally subdivid-
ed into lower, middle, and upper members. Only
the lower member is present in Gulf County. The
general lithology is comprised of light-colored
sands and interbedded calcareous and glau-
conitic sands and shales (Applegate et al., 1978).
Foraminifera are the dominant fossils, including
species of Planulina, Valvulineria, Ammo-
baculites, Gumbelina, and Trochamina (Florida
Geological Survey unpublished well data). The
thickness of the Atkinson Formation in Gulf
County ranges from about 400 to 800 feet.


Upper Cretaceous
unnamed chalk and limestone

The uppermost Cretaceous sediments of Gulf
County are comprised of an unnamed series of
white, chalky limestones and interbedded gray to
light green calcareous shales. They often contain
fossils of the cephalopod Inoceramus and both
benthic and planktonic foraminifera (Florida
Geological Survey unpublished well data). Well
W-914 penetrated a characteristic unnamed





Florida Geological Survey


Upper Cretaceous section in the interval -3,196
to -4,200 feet MSL. The sediments in this well
were largely chalky limestones and thin,
interbedded, sometimes carbonaceous and pyri-
tiferous shales. Abundant benthic foraminifera
are present, including Gumbelina excolata,
Bulimina carseyi, and Bolivinoides decorate.
The top of the Upper Cretaceous is nearly flat-
lying, at approximately -2,800 to -3,200 feet MSL.
Thickness ranges from about 1,450 feet in north-
ern Gulf County to about 2,150 feet in the south-
ern part of the county. The Cretaceous
sediments are unconformably overlain by Lower
Cenozoic Erathem sediments.


Cenozoic Erathem


The Cenozoic Erathem sediments underlying
Gulf County range in age from Late Paleocene
through Holocene. Most of these deposits are
comprised of marine limestones, dolomites, and
shellbeds, containing varying proportions of silici-
clastic sediments. The Cenozoic units dip and
thicken to the southwest.
The carbonate strata, principally including the
Eocene through Miocene limestones, are fresh-
water-bearing units of the Floridan aquifer sys-
tem. Pleistocene and Holocene undifferentiated
sands and clays form a surficial veneer over all
of Gulf County.


Tertiary System
Upper Paleocene and Lower Eocene Series
Wilcox Group Undifferentiated

Applin (1964) placed the Paleocene sedi-
ments of the Florida panhandle into the Lower
Paleocene Midway Group based on its fossil
foraminifera. Subsequent reevaluations of the
fossil fauna, as well as refinements in planktonic
foraminiferal zonation schemes, indicate that the
assemblage observed by Applin (1964) is actual-
ly Late Paleocene to Early Eocene in age


(Braunstein et al., 1988). Braunstein et al. (1988)
place the Upper Paleocene and Lower Eocene
strata overlying the Cretaceous of the central
Florida panhandle in the Wilcox Group (Crider,
1906) undifferentiated.
Wilcox Group sediments under Gulf County
are predominantly impure marine carbonates.
The downdip carbonate lithology of these sedi-
ments differs significantly from the type area in
Alabama, and direct lithologic correlation is diffi-
cult. Oil test wells have allowed description of the
entire Wilcox sequence under the county. Well
W-1468 penetrated 600 feet of Wilcox Group
section in the depth interval -2,170 to -2,770 feet
MSL. The lithology is comprised of interbedded
very light brown to chalky white, fossiliferous
limestones, argillaceous limestones, calcareous
shale, and light brown, glauconitic and sandy
limestones (Florida Geological Survey well file
data). Foraminifera are the dominant fossils pre-
sent. Similarly, well W-1470 penetrated Wilcox
Group sediments between -2,362 and -2,863 feet
MSL. In this well, the strata were largely light
grayish-brown, cherty dolomites and glauconitic,
sandy, and argillaceous limestones (FGS well file
data).


Middle Eocene Series
Tallahatta and Lisbon Formations

The Tallahatta Formation (Dall, 1898) and the
overlying Lisbon Formation (Smith, 1907) com-
prise the Middle Eocene sediments of the central
and western Florida panhandle. Both units were
named from type areas in Alabama. These units
are age equivalent to the Avon Park Formation
(Miller, 1986) of northern and peninsular Florida.
Gulf County lies in a transitional area of the
Florida panhandle over the axis of the
Apalachicola Embayment. Here the carbonate
facies of the Avon Park Formation grade laterally
westward into the more sandy, glauconitic, and
argillaceous limestones, sands and shales of the
Tallahatta and Lisbon Formations. Consequently,
the Middle Eocene sediments underlying Gulf




Bulletin No. 63


County may contain lithologic constituents char-
acteristic of both eastern and western facies.
Downdip towards the Gulf, all three units are cal-
careous (Chen, 1965). The assignment of these
sediments to a specific lithologic unit is often diffi-
cult. Chen (1965), citing the difficulty of picking
specific Middle Eocene formations in the central
panhandle, grouped the Lisbon, Tallahatta, and
Avon Park Formation sediments into the
Claiborne Group undifferentiated. However,
based on the siliciclastic constituents in the lithol-
ogy as well as paleontological criteria, Braunstein
et al. (1988) placed the Middle Eocene units
under Gulf County into the Tallahatta and Lisbon
Formations.
Most Gulf County oil test wells have penetrat-
ed Middle Eocene section. Two wells have been
described in detail. Well W-1468 in the northeast-
ern part of the county drilled typical Middle
Eocene section in the interval -1,330 to -2,170
feet MSL. The lithology in this well is comprised
of light grayish-brown, fossiliferous limestones
interbedded with argillaceous limestones and
dark grayish brown, calcareous shales (FGS well
file data). Well W-1470, in west-central Gulf
County, also penetrated Middle Eocene strata
between -1,447 feet and -2,362 feet MSL. The
lithology shown in this well ranges from dark
grayish-brown, chalky, fossiliferous limestone to
interbedded calcareous shales and argillaceous
limestones (FGS well file data).
Differentiation of the Tallahatta and Lisbon
Formations in Gulf County is not possible using
lithologic criteria. Therefore, the two units are, in
this report, grouped into Tallahatta/Lisbon
Formations undifferentiated. These units are
overlain by the lithologically distinct Upper
Eocene Ocala Group.


Upper Eocene Series
Ocala Group

Dall and Harris (1892) proposed the name
Ocala Limestone for calcareous sediments
exposed in the vicinity of Ocala, Marion County,


Florida. Since this initial usage, the term Ocala
Limestone has been redefined by numerous
authors. An excellent historical review is provided
by Puri (1957).
The nomenclature proposed by Puri (1957)
has been used by the Florida Geological Survey.
He raised the Ocala to Group rank, with three
subdivisions; in ascending order, these are: the
Inglis Formation, the Williston Formation, and the
Crystal River Formation.
The Ocala Group is known to underlie most of
Florida. Statewide, elevations of the top of the
group range from greater than 100 feet above
MSL in west-central peninsular Florida and the
northern panhandle to over 1,200 feet below
MSL in south Florida and the extreme western
panhandle.
In Gulf County, the Ocala Group lies below the
depth attained by most water wells. Its lithology
in this area is derived from oil test well samples.
The lithology shown in these wells is typically
comprised of cream to light brown, porous, bio-
clastic, fossiliferous limestone and dolomitic lime-
stone. Fossils are generally abundant, especially
species of the large foraminifera Lepidocyclina
and Nummulites and bryozoa, echinoids, mol-
lusks, and algal fragments.
Depth to the top of the Ocala Group sediments
is variable throughout Gulf County, but generally
ranges from about -950 feet to -1,015 feet MSL.
Based on available FGS well data, the thickness
of the Ocala Group varies from approximately
350 feet under north-central Gulf County (well W-
1468) to about 530 feet at the southern edge of
the county (well W-15808). The Ocala Group is
unconformably overlain by the Oligocene
Suwannee Limestone.


Oligocene Series
Suwannee Limestone

The name Suwannee Limestone was pro-
posed by Cooke and Mansfield (1936) for the
fossiliferous limestone exposed along the
Suwannee River in north Florida. Vernon (1942)




Florida Geological Survey


and Cooke (1945) give good nomenclatural his-
tories for this unit, and are recommended as ref-
erences.
In Gulf County, the top of the Suwannee
Limestone lies at depths only reached by oil test
wells, ranging between -700 and 750 feet MSL.
The lithology consists of white to light gray to yel-
lowish gray, well-indurated, chalky to sucrosic,
fossiliferous limestone and dolomite. Mollusks,
bryozoans, and foraminifera are common fossils
in the Suwannee Limestone.
The Suwannee Limestone underlies much of
Florida, and is a major component of the Floridan
aquifer system. It interfingers to the north with
the Marianna Limestone, the only other
Oligocene unit present in the central Florida pan-
handle. In Gulf County, the Suwannee is overlain
by the Lower Miocene St. Marks and
Chattahoochee Formations or by the Middle
Miocene Bruce Creek Limestone.


Miocene Series

The Miocene Epoch marked a change in the
depositional regime of the Florida Platform. An
influx of siliciclastic sediments, reworked and
deposited by high-standing Miocene seas, cov-
ered the carbonates of earlier epochs.
Throughout northern and peninsular Florida, the
Miocene is represented by the siliciclastic and
impure carbonate sediments of the Hawthorn
Group. These units are often characterized by
abundant marine phosphate deposits. In the cen-
tral portion of the Florida panhandle, a series of
impure, fossiliferous, marine carbonate units
were deposited during the Miocene. These
include the Lower Miocene Chattahoochee and
St. Marks Formations, and the Middle Miocene
Bruce Creek Limestone and Intracoastal
Formation. The carbonates typically contain
quartz sand, clay and occasionally phosphate.
Most of the Miocene units in the panhandle dip
and thicken westward into the Gulf of Mexico
Sedimentary Basin, with localized thickening in
the area of the Apalachicola Embayment.


Lower Miocene Series
St. Marks/Chattahoochee Formations

Johnson (1888) first applied the term Tampa
Formation to Lower Miocene sediments cropping
out in the vicinity of Tampa, Hillsborough County,
Florida. Over the years, many authors have
attempted to redefine and divide this unit. Vernon
(1942) included all sediments lying above the
Suwannee Limestone and below the Alum Bluff
Group in the Tampa Formation. Puri (1953)
placed all sediments previously assigned to the
Tampa Formation in the Tampa (Aquitanian)
Stage and erected two lithologic subdivisions: the
St. Marks (Finch, 1823) and Chattahoochee (Dall
and Stanley-Brown, 1894; Langdon, 1889)
facies. These faces were raised to formation sta-
tus by Puri and Vernon (1964).
The name St. Marks Formation includes the
calcareous downdip facies, which underlie por-
tions of Wakulla and Franklin Counties to the
east of Gulf County. Lithologically, the St. Marks
Formation is a very pale orange to light gray to
white, well-indurated, fossiliferous, sometimes
quartz-sandy and dolomitic, marine calcarenitic
limestone. Mollusks and foraminifera are the
common fossils in this formation, with the mol-
lusks often present as molds. It is often indistin-
guishable in wells from the overlying Middle
Miocene Bruce Creek Limestone, particularly in
the area from central Franklin County westward
(Schmidt, 1984). The St. Marks occurs at the sur-
face in eastern Wakulla County. From its surface
occurrence, it dips and thickens westward into
the trough of the Apalachicola Embayment,
reaching a thickness of over 200 feet under the
axis of the embayment.
The Chattahoochee Formation underlies por-
tions of the northern central and western Florida
panhandle, including northern Gulf County. This
unit differs from the age-equivalent St. Marks
Formation in being a dolomitic calcilutite or fossil-
iferous calcilutite. It occurs at the surface in the
vicinity of Chattahoochee, Gadsden County, and
dips south and westward.




Bulletin No. 63


Downdip in the vicinity of Gulf County, the St.
Marks Formation, Chattahoochee Formation, and
in some areas, the overlying Bruce Creek
Limestone are frequently altered by ground water
to the extent of being indistinguishable. As a
result, the formations are locally difficult to differ-
entiate, even in cores. For this reason, the St.
Marks and Chattahoochee Formations are herein
lumped as a single unit (St. Marks Formation) in
the geologic cross-sections (Figures 10 15).


Middle Miocene Series
Bruce Creek Limestone

The name Bruce Creek Limestone was pro-
posed by Huddlestun (1976) for a white to light
gray to yellowish-gray, quartz-sandy, often phos-
phatic, highly fossiliferous marine limestone
underlying the south-central panhandle.
Foraminifera, echinoids, bryozoans, and mol-
lusks are the predominant fossils present. It is a
wedge- shaped unit, extending from north-central
Okaloosa County eastward to western Wakulla
County (Schmidt, 1984). In Gulf County, the
Bruce Creek Limestone dips generally to the
southwest, ranging in depth from about -150 feet
MSL at the northern edge of the county to about -
500 feet MSL under St. Joseph Spit. A contour
map of its upper surface is illustrated in Figure
16. Thickness of the unit exceeds 200 feet under
Gulf County. The total thickness range is difficult
to determine because many wells do not pene-
trate the entire sequence. In wells that are deep
enough, the basal Bruce Creek lithology is fre-
quently indistinguishable from the underlying
units, and a lower contact cannot be picked
(Boiling, 1982).
The Bruce Creek Limestone is overlain by the
more fossiliferous and generally more cal-
carenitic Intracoastal Formation. In some wells in
central Gulf County, a thin gray clayey dolosilt
occurs at the top of the Bruce Creek, delineating
the contact between the Bruce Creek and
Intracoastal Formation (Bolling, 1982).


Middle Miocene Pliocene Series
Intracoastal Formation

Huddlestun (1976) first described the
Intracoastal Limestone as a soft, sandy, fossilif-
erous limestone of Pliocene age underlying the
coastal area of western Florida. Schmidt and
Clark (1980) formally introduced the name
Intracoastal Formation, and established a Middle
Miocene to Late Pliocene age for the unit based
on planktonic foraminifera. It is a wedge-shaped
unit, dipping southwestward and westward, and
extending from its updip pinchout in the eastern
Franklin County-western Wakulla County area to
the Okaloosa-Santa Rosa county line. The
Intracoastal Formation underlies all of Gulf
County, reaching a maximum thickness of 300
feet in the southwestern part of the county.
Lithologically, the Intracoastal Formation is a
light gray to yellowish-gray, glauconitic, phos-
phatic, and sometimes argillaceous, highly fossil-
iferous marine limestone. Microfossils are very
abundant. Other fossils commonly include mol-
lusks, echinoids, bryozoans, ostracods, and
shark teeth. The depth to the Intracoastal
Formation typically ranges from about -50 feet
MSL in northern Gulf County to more than -200
feet MSL under St. Joe Spit. A structural contour
map of the top of the Intracoastal Formation is
shown in Figure 17.
The Intracoastal Formation contains abundant
planktonic foraminifera, which are useful sedi-
ment age indicators. Boiling (1982) conducted a
biostratigraphic analysis of the Intracoastal
Formation in six cores in Gulf County. Based on
planktonic foraminiferal assemblages, she dated
the age of the Intracoastal as Middle Miocene,
Globorotalia fohsi Zone. The presence of
Globorotalia margaritae in some samples near
the top of the Intracoastal Formation sequence
indicates that the upper portion of this unit is Late
Pliocene in age (Bolling, 1982). This finding
agrees with the work of Clark and Wright (1979)
in neighboring Bay County. A hiatus, which prob-
ably occurred in the Late Miocene, separates the




Florida Geological Survey


._i


0
-250


CONTOURS ARE IN FEET
BELOW MEAN SEA LEVEL
CONTOUR INTERVAL = 50 FEET


\ 0 MILES
0 1 2 3 4 5
FGS170391 I I I 1 |
02468
0 2 4 6 8
KILOMETERS

Figure 16. Structural contour map of the top of the Bruce Creek Limestone.


.300




Bulletin No. 63


-175 \ FGS040391


S00 CONTOURS ARE IN FEET
BELOW MEAN SEA LEVEL
CONTOUR INTERVAL = 25 FEET

MILES
0 1 2 3 4 5

0 2 4 6 8
012345

02468
KILOMETERS

Figure 17. Structural contour map of the top of the Intracoastal Formation.





Florida Geological Survey


different age sections of the Intracoastal
Formation. Missing section, however, is not
apparent in the lithology (Bolling, 1982).
The Intracoastal Formation is unconformably
overlain by the "Chipola-like" sediments, Jackson
Bluff Formation, or, in a few wells, by
Pleistocene-Holocene undifferentiated sedi-
ments. In local areas, the Jackson Bluff and
Intracoastal Formations may be age equivalent
and grade into one another (Bolling, 1982;
Schmidt, 1984).


Upper Pliocene Series
"Chipola-like" sediments

The sediments of the Chipola Formation have
been described in outcrop areas north of Gulf
County by numerous authors, including Burns
(1889), Dall and Stanley-Brown (1894), Matson
and Clapp (1909), Gardner (1926), Puri (1953),
and Banks and Hunter (1973). Puri and Vernon
(1964) redefined the unit as a formation, describ-
ing the type locality along the Chipola River near
Tenmile Creek in Calhoun County. Here it is
comprised of bluish-gray to yellowish brown, fos-
siliferous molluscan marl. It is restricted in occur-
rence within the east central panhandle area to
the vicinity of the Apalachicola Embayment,
including Bay, Calhoun, Liberty, and possibly
Gulf Counties. Beds with a lithology similar to the
type Chipola Formation have been traced in
cores into Gulf County from the north by Schmidt
(1984). Based solely on lithologic criteria,
Schmidt (1984) included these "Chipola-like"
sediments in the Chipola Formation. Due to
insufficient core coverage and a significant age
discrepancy, some uncertainty exists as to
whether the beds in Gulf County with Chipola
lithology are actually correlative with the type
Chipola Formation to the north. Near the type
area and at Alum Bluff in Liberty County, the
Chipola Formation has been dated by microfos-
sils as Late Early Miocene to Early Middle
Miocene in age (Akers, 1972; Huddlestun, 1976).
Downdip in Gulf County, the "Chipola-like" unit is


entirely in the subsurface and has not been
directly dated. However, age dates obtained from
microfossils in the underlying Intracoastal
Formation place this unit in the Early Late
Pliocene. The "Chipola-like" sediments must
therefore be younger downdip than in the type
area to the north, and based on stratigraphic
position, are Late Pliocene in age. For this rea-
son, these sediments in Gulf County are herein
referred to as "Chipola-like" sediments.
In general, the Chipola Formation grades
downdip from the molluscan calcarenite of the
type area into a yellowish-gray to light gray,
quartz-sandy, fossiliferous limestone of the
"Chipola- like" beds in Gulf County. It occurs spo-
radically in wells, possibly as erosional remnants,
and does not underlie all of Gulf County. The
"Chipola-like" sediments generally range from
about 80 feet MSL to -140 feet MSL in depth
under Gulf County. Thickness of the unit varies
from 0 to about 50 feet.


Jackson Bluff Formation

Puri and Vernon (1964) combined the Upper
Miocene Ecphora and Cancellaria mollusk faces
of Puri (1953) into the Jackson Bluff Formation,
named after Jackson Bluff on the Ochlockonee
River in western Leon County, Florida. The
Jackson Bluff Formation extends in a blanket-like
deposit from central Washington County east-
ward to central Leon County. It crops out sporad-
ically along stream beds in the north-central
panhandle.
In Gulf County, the Jackson Bluff Formation is
comprised of light gray to gray, poorly consolidat-
ed clayey sands and sandy clays containing
abundant mollusk shells. It underlies most of the
county, dipping and thickening to the southwest.
Depth to the top of the unit varies from approxi-
mately +5 feet MSL at the northern edge of the
county to nearly -165 feet MSL at the southern
tip near Cape San Bias (Figure 18). The thick-
ness of the Jackson Bluff ranges from 0 feet in
wells where it is missing (primarily north-central





Bulletin No. 63


0I


CONTOURS ARE IN FEET
BELOW MEAN SEA LEVEL
CONTOUR INTERVAL = 25 FEET


0 2 4 6 8
02468KILOMETERS
KILOMETERS


Figure 18. Structural contour map of the top of the Jackson Bluff Formation.





Florida Geological Survey


and eastern Gulf County) to about 150 feet along
the western and southern edges of the county
(Figure 18).
Based on planktonic foraminiferal assem-
blages (Akers, 1972; Huddlestun, 1976) and cal-
careous nannofossils (Akers, 1972; Akers and
Koeppel, 1973) the Jackson Bluff Formation is
placed in the Late Pliocene Series. Planktonic
foraminifera suggest a latest Pliocene and possi-
bly early Pleistocene age for the downdip por-
tions of this unit (Schmidt and Clark, 1980). The
Jackson Bluff Formation is overlain by the
Pleistocene-Holocene undifferentiated sands and
clays.


Pleistocene-Holocene Series
Undifferentiated sands and clays

Much of the southern edge of the Florida pan-
handle is blanketed by Pleistocene to Holocene
age undifferentiated sands and clays. In Gulf
County, these sediments are comprised princi-
pally of white to light gray to greenish-gray to
brown to pale orange sands, clayey sands,
sandy clays and in southern Gulf County, mas-
sive clays. Many of the sands show cross-bed-
ding, and the different lithologies are typically
interbedded (Schmidt, 1984). Shell beds also
occur locally along the coastal portion of the
county. The undifferentiated sediments reach
thicknesses of over 150 feet in the southern and
southwestern portions of the county.
A series of undifferentiated red, limonite-rich
clayey sands similar to the Citronelle Formation
sediments are present along the northern edge
of Gulf County. These deposits may represent
reworked sediments derived from the Citronelle
Formation outcrop area to the north and west of
Gulf County.
The undifferentiated sands and clays forming
the surficial sediments in Gulf County are pre-
dominantly marine and alluvial in origin. Relict
marine features, such as stranded beach ridge
systems now situated inland from the modern
Gulf coast, were formed during the last sea level


highstand of the Pleistocene. Many of the
Pleistocene and Holocene sediments may have
been deposited at the edge of a migrating paleo-
delta of the ancestral Apalachicola River. In
some cores, the undifferentiated sediments show
graded bedding, cross-bedding, and contain well-
preserved wood fragments, most likely repre-
senting deposition in a fluvial or prograding delta
environment (Schmidt, 1984). The interbedded
sands and clays and the massive clay units also
locally contain plant remains and abundant
assemblages of both freshwater and saltwater
diatoms; Schmidt (1984) associated these sedi-
ments with paleo-lagoons or tidal flats adjacent
to a prograding delta.
Prior to the construction of the Jim Woodruff
Dam on the Apalachicola River at the Georgia-
Florida state line, the river provided significant
siliciclastic sediment input into the Gulf County
area. Residual Late Holocene river levee and bar
deposits are common along the eastern edge of
Gulf County today, adjacent to the Apalachicola
River and its tributaries.


STRUCTURE

The subsurface structure of Gulf County has
been influenced by several regional structural
features. Figure 19 illustrates the location and
orientation of these features.


Apalachicola Embayment

* Gulf County is situated over the axis of a broad
sedimentary basin known as the Apalachicola
Embayment. Pressler (1947) estimated its size
as approximately 30,000 square miles. Schmidt
(1984) provides an excellent interpretative and
nomenclatural history for this feature.
The Mesozoic and younger sediments underly-
ing Gulf County are downwarped along the
southwestward-plunging axis of the embayment.
Oil test wells have shown the sediment fill of the
basin to consist of about 13,000 feet of Triassic




Bulletin No. 63


. -


SOUTHEAST
GEORGIA
EMBAYMENT


/


N


MILES
50 100


KILOMETERS


FGS050391


. -


0l


Figure 19. Principal subsurface structures of north Florida.


150

240


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CHEE




Florida Geological Survey


to Holocene age deposits, all resting on
Paleozoic rocks (Applegate et al., 1978; Schmidt
and Clark, 1980). Of this total sediment thick-
ness, approximately 10,000 feet are comprised
of Mesozoic rocks, and the upper 3,000 feet are
Cenozoic in age (Schmidt, 1984).
The Apalachicola Embayment is a basin situat-
ed between two structural highs, the
Chattahoochee Anticline to the west and the
Ocala Platform (variously called the Ocala Arch
or Ocala Uplift see below) to the east. At its
northern terminus, the Apalachicola Embayment
narrows and extends into the Gulf Trough in
southern Georgia. It opens to the south-south-
west, both widening and deepening where it
extends into the modern Gulf of Mexico. The
southernmost extent of the embayment is not
well known due to the lack of offshore well data
(Schmidt, 1984).

Gulf Trough

Dall and Harris (1892) proposed the existence
of a channel- like area of nondeposition separat-
ing the continental border from the Eocene and
Miocene islands of the Florida peninsula. Later
authors, including Veach and Stephenson
(1911), Applin and Applin (1944), Pressler (1947)
and Jordan (1954) recognized a structural chan-
nel or trough, possibly a graben, in Mesozoic and
Cenozoic sediments extending from southeast
Georgia southwestward into the northern pan-
handle of Florida. Schmidt (1984) detailed the
structural history of this feature. During Late
Cretaceous through Oligocene time, this elon-
gate structure connected the Southeast Georgia
Embayment and the Apalachicola Embayment
(Pressler, 1947). Structure maps drawn on differ-
ent subsurface stratigraphic horizons indicate the
axis of the trough migrated over time. In the Late
Mesozoic, the trough axis moved southeastward
to the vicinity of western Taylor and Madison
Counties; the direction reversed in the Early
Tertiary and the trough moved northwestward to
the present Gadsden/Liberty County area
(Schmidt, 1984). Throughout its existence as an


open connection between the embayments, the
trough was an area of non-to-slow deposition.
Chen (1965) believed that strong, scouring water
currents in the trough formed both a lithologic
and biologic facies barrier during almost the
entire Paleocene through Eocene time.
Its influence as a sediment barrier apparently
waned by the end of the Oligocene or earliest
Miocene, at which time the depression had prob-
ably been infilled with sediments. The source of
the sediment fill may have been siliciclastics
eroded from the Appalachian Mountain range
during a period of renewed uplift in the Early
Neogene (Stuckey, 1965; Scott, 1988). The
Paleogene strata in Florida, particularly those
stretching from the central panhandle into the
peninsula, are nearly pure carbonates, repre-
senting a carbonate bank paleoenvironment iso-
lated from continental terriginous sediment input.
Final infilling of the Gulf Trough probably
allowed, for the first time in millions of years, the
influx into peninsular Florida of continentally-
derived siliciclastics. These siliciclastics became
common components of the Lower Miocene and
younger formations in Florida.

Chattahoochee Anticline

North and northwest of the Apalachicola
Embayment is a minor structural high called the
Chattahoochee Anticline (Veach and
Stephenson, 1911; Puri and Vernon, 1964). This
structure is an elongate anticline with an axial
surface oriented northeast- southwest. It crests in
Jackson County, to the north of Gulf County, and
exposes Oligocene and Eocene carbonates in
the vicinity of the crest. Younger sediments pinch
out or are truncated against the flanks of the anti-
cline (Schmidt, 1984).

Ocala Platform

The Ocala Platform (Scott, 1988) is a gentle,
post-Oligocene flexure in west-central peninsular
Florida. Previous workers (Vernon, 1951; Puri
and Vernon, 1964) have applied the name Ocala




Bulletin No. 63


Uplift to this feature. The mechanics and timing
of formation of this structure are not well under-
stood. It brings Eocene carbonates to the surface
around its crest in Citrus and Levy Counties.
Younger units, extending from the Apalachicola
Embayment eastward, approach shallower
depths and are ultimately truncated against the
flanks of the platform.

Peninsular Arch

The Peninsular Arch forms the axis of peninsu-
lar Florida (Applin, 1951). It is a southeast-trend-
ing structural high in pre-Mesozoic sediments. As
with the parallel trending but otherwise unrelated
Ocala Platform, its mode of formation is poorly
understood.

GROUND WATER

Ground water is water that fills the pores and
interstitial spaces in the rocks and sediments
beneath the surface of the earth. Most of Gulf
County's ground water is derived from precipita-
tion within the county and from neighboring coun-
ties to the north. A portion of the precipitation
leaves the area by surface runoff in stream flow
or by evapotranspiration. The remainder soaks
into the ground and some moves downward into
the porous zone of saturation. The top of the
zone of saturation is known as the water table.
Once in the zone of saturation, the water moves
under the influence of gravity towards discharge
points such as wells, seeps, springs, or eventual-
ly the Gulf of Mexico. Some of the water seeps
downward into the deeper aquifer units, providing
recharge to them.
In Gulf County, three primary ground-water
aquifer systems are present. These are, in order
of increasing depth, the surficial aquifer system,
the intermediate confining unit, and the Floridan
aquifer system (Southeastem Geological Society
Ad Hoc Committee, 1986). Figure 20 illustrates
the aquifer nomenclature in use today.


Surficial aquifer system

Water in the shallow undifferentiated Plio-
Pleistocene sand and clay sediments is not con-
fined and the water level is free to rise and fall.
This unconfined water comprises the surficial
aquifer system, which is recharged through direct
infiltration of rain water. The surficial aquifer is
generally a thin unit, varying proportionally with
the thickness of the undifferentiated sands and
clays (Wagner, 1988). In general, the thickness
ranges from 4 feet in eastern Gulf County to as
much as 90 feet in the northwestern part of the
county (Scott et al., 1991 in preparation). The
surficial aquifer system surface is most likely an
approximate replica of the land surface topogra-
phy, and it fluctuates in elevation due to droughts
or seasonal rainfall differences. Water movement
within the surficial aquifer system is generally
downhill, or from topographically high areas to
low areas. It discharges into streams, bays and
the Gulf of Mexico. A small quantity of water from
the surficial aquifer system may percolate down-
ward into the underlying intermediate aquifer sys-
tem. Some form of confining layer, such as clay
or clayey sand sediments, generally forms a low-
permeability confining layer separating the surfi-
cial and intermediate aquifer systems. The.
surficial aquifer system is not used extensively
for public water supplies in Gulf County.

Intermediate confining unit

The intermediate confining unit in Gulf County
lies below the surficial aquifer system and is con-
tained within the sediments of the Jackson Bluff,
Chipola, and Intracoastal Formations. This unit
functions primarily as a confining unit to the
underlying Floridan aquifer system, but may
locally contain minor aquifers, depending on the
thickness and lithology of the host formations.
The aquifers, where present, are comprised of
sands and limestones, and generally yield small
quantities of water suitable for domestic use
(Wagner, 1988).





SYSTEM SERIES FORMATION HYDROSTRATIGRAPHIC

HOLOCENE

QUATERNARY UNDIFFERENTIATED SURFICIAL AQUIFER
PLEISTOCENE SANDS AND CLAYS SYSTEM


JACKSON BLUFF FM.ERMEDI
INTERMEDIATE
w PLIOCENE CHIPOLA FM.
z CONFINING UNIT
l INTRACOASTAL FM.
0C ----------------- -------
O
w BRUCE CREEK LS.
z MIOCENE
ST. MARKS/CHATTAHOOCHEE FMS.
TERTIARY FLORIDAN AQUIFER
S OLIGOCENE SUWANNEE LS. SYSTEM

U OCALA GROUP
O EOCENE TALLAHATTA/LISBON FMS.
SWILCOX GRP. UNDIFF.

PALEOCENE WILCOX GRP. UNDIFF. SUB-FLORIDAN

CRETACEOUS CONFINING UNIT
AND UNDIFFERENTIATED
OLDER

FGS020391
Figure 20. Correlation of lithostratigraphic and hydrostratigraphic units in Gulf County (modified from Southeastern Geological Society
Ad Hoc Committee, 1986).




Bulletin No. 63


The intermediate confining unit generally con-
forms to the geometry of the geological forma-
tions containing it. It ranges from about 150-feet
thick in northeastern Gulf County to nearly 500
feet near Cape San Bias. The top of the interme-
diate confining unit varies from about 10 feet
MSL in northern Gulf County to approximately -
50 feet MSL at the southern edge of the county
(Scott et al., 1991 in preparation). Aquifers within
the intermediate confining unit are recharged pri-
marily from lateral water influx, and from seep-
age from the overlying and underlying aquifers.
The intermediate confining unit is not extensively
used as a potable water source in Gulf County.

Floridan aquifer system

The name Floridan Aquifer was originally pro-
posed by Parker et al. (1955) for the artesian
aquifer including all or parts of formations from
Middle Eocene age to Middle Miocene age. This
name was formally modified to Floridan aquifer
system by the Southeastern Geological Society
Ad Hoc Committee (1986).
The Floridan aquifer system is the most impor-
tant freshwater aquifer in Florida, underlying
much of the central and eastern panhandle, and
most of the peninsula of Florida. In Gulf County,
it is contained within a number of Eocene
through Miocene formations, including the Lisbon
Formation, the Ocala Group, the Marianna and
Suwannee Limestones, the St. Marks Formation,
and the Bruce Creek Limestone.
The Floridan aquifer system is the thickest and
most productive unit in the central panhandle,
supplying the bulk of the domestic, urban and
agricultural water used in Gulf County. Most
wells tap the upper Floridan, where the chloride
concentration of the water is 100 mg/I or less;
this concentration increases to nearly 500 mg/I in
the lower portion of the aquifer (Barr and Pratt,
1981). The top of the Floridan aquifer system
corresponds to the top of the Bruce Creek
Limestone, and in Gulf County, varies from
approximately -150 MSL at the northern edge of
the county to 500 feet MSL under St. Joe


Peninsula. The aquifer thickens to the south-
southwest, ranging from about 1000-feet thick at
the Gulf-Calhoun County line to 2,200-feet thick
in southeastern Gulf County, near Lake Wimico
(Scott et al., 1991 in preparation). The Floridan
aquifer system is underlain by the sub-Floridan
confining unit, comprised of the Middle Eocene
Tallahatta Formation and older sediments. These
sediments typically contain clays, shales, and
chalk which act as confining layers.
The Floridan aquifer system is confined in all
areas of Gulf County. Minor recharge may occur
through downward seepage from aquifer units in
the overlying intermediate confining system, but
most recharge occurs from water inflow from
adjacent counties. Direct recharge to the Floridan
aquifer system occurs in Jackson County to the
north, where the porous limestones comprising
the aquifer are exposed at the surface.

Potentiometric Surface

Water confined within the artesian Floridan
aquifer system is generally under a pressure
greater than atmospheric, resulting in a positive
static head. The height to which water rises in
tightly cased wells penetrating the Floridan
aquifer system forms an imaginary surface called
the potentiometric surface. If the land elevation of
a well is below the level of the potentiometric sur-
face, the well will flow. Figure 21 shows the
potentiometric contours for the upper Floridan
aquifer system in Gulf County. These contours
represent the potentiometric surface relative to
mean sea level. If, for example, the land surface
elevation of a cased well in the Floridan aquifer
system is 50 feet MSL and the water level is 20
feet below land surface, then the potentiometric
surface at this location would be 30 feet above
MSL. Ground water flows from a direction of high
to low potentiometric surface, generally in a
direction perpendicular to the potentiometric con-
tours. In Gulf County, this direction is predomi-
nantly southward. Most water flowing through the
Floridan aquifer system is discharged into the
Gulf of Mexico. The elevation of the potentiomet-




Florida Geological Survey


_ CALHOUN CO.





''00xo/
I


CONTOURS ARE IN FEET
ABOVE MEAN SEA LEVEL


Figure 21. Potentiometric surface map of the Floridan aquifer system in Gulf County (from Barr, 1987).




Bulletin No. 63


ric surface of the Floridan aquifer system is high-
est during rainy seasons, and lowest during dry
periods. It is also locally affected by wells, usual-
ly being lower adjacent to pumping wells.
Water availability within the Floridan aquifer
system is currently good for all of Gulf County.
The amount of water that can be withdrawn from
the aquifer is largely dependent on the thickness
and transmissivity of the rocks containing the
aquifer. Northern Gulf County, with its higher
potentiometric surface and closer proximity to the
recharge areas of Jackson County, has adequate
water availability from the Floridan aquifer sys-
tem. In the coastal areas, the freshwater layer
within the aquifer thins in a seaward direction,
gradually pinching out as it laps over the wedge
of saltwater which fills the aquifer rocks under the
Gulf of Mexico. Less freshwater is available to
pump in these areas. In some high-growth areas
of Florida, such as the lower east and west
coasts of the peninsula, pumping has drastically
drawn down the freshwater aquifer levels caus-
ing a landward migration of the fresh-saltwater
interface. In these areas many coastal wells now
draw saltwater. As long as population growth and
water withdrawal rates in the coastal areas of
Gulf County are low, saltwater contamination of
Floridan aquifer system wells near the coast
should not be a problem.

MINERAL RESOURCES

The following discussion provides a general
overview of the near-surface mineral commodi-
ties and petroleum resources of Gulf County.
Information presented in this section was derived
from mineral reports included in various Florida
Geological Survey publications, data on file at
the FGS, and from data supplied by the Gulf
County Road Department.


Clay

Clay occurs both as discrete beds in, and as a
matrix constituent of, the undifferentiated sedi-


ments covering Gulf County. Most clays repre-
sent Pliocene and Pleistocene deltaic deposits.
While widespread in occurrence, many of these
deposits contain significant impurities such as
quartz sand. Relatively pure Holocene flood plain
clays are common along the Apalachicola River,
and one such deposit has been utilized for brick
making in neighboring Calhoun County.
In general, specific tests on the clay resources
of Gulf County are few. Three Gulf County clay
samples from an area northeast of Wewahitchka
were included in a joint Florida State University-
U.S. Bureau of Mines study performed in 1957
(Florida Geological Survey unpublished data).
These samples were tested by the U.S. Bureau
of Mines for their fired properties, and the sam-
ples were retained in the Florida Geological
Survey Mineral sample series (M-Series). Table
2 summarizes the location and properties of each
sample.
Other clays are associated with the deeper
Pliocene and Miocene units underlying Gulf
County. Most are untested, and the depth of
these units generally limits their economic poten-
tial.
The extent to which Gulf County's clay
resources are explored and utilized will be largely
dependent upon future local demand. At present,
a lack of useable clay deposits and insufficient
demand for clay products precludes economic
development of this resource.

Limestone and Dolomite

Miocene and Pliocene limestone (CaCO3) and
dolomite (CaMg(CO3)2) are present at depth
under all of Gulf County. These materials have
never been mined in the county. The impure
nature of most of these units, as well as the over-
burden thickness make economic mining of this
commodity impractical. It is therefore unlikely that
limestone and dolomite will ever have economic
potential in Gulf County.
Basic, Incorporated, a magnesium oxide pro-
ducer in Port St. Joe (see Magnesium
Compounds, this section), supplied the County




Florida Geological Survey


Table 2. U.S. Bureau of Mines, Gulf County clay sample analyses


SAMPLE NO. M-2992 Common sandy clay


Location:
Dry color:
Water of plasticity:
Dry volume shrinkage:
General plasticity:

Fired Properties

1j
Color: b


Volume shrinkage
(% dry volume): 1(
% absorption: 1


3S 9W sec. 30bb
red-gray
37%
7%
good, slightly sandy and fatty


Cone Temperature (F)

300 2000 2100 2200
uff buff red- red-
brown brown


11.0
20.5


14.5
13.6


15.0
12.2


2300
red-
brown


15.0
11.6


Hardness: Steel hard at 2100F


SAMPLE NO. M-2993 Common clay


Location:
Dry color:
Dry volume shrinkage:
General plasticity:

Fired Properties


Color: b


Volume shrinkage
(% dry volume): 11
% absorption: 21


3S 9W sec. 29cc
buff gray
90%
fair, slightly sandy and fatty


Cone Temperature CF)

300 2000 2100 2200
uff buff red- red-
brown brown


1.0
1.6


11.0
19.6


14.0
19.6


17.5
9.9


2300
red-
brown


17.5
8.8


Hardness: Steel hard at 2200F


2400
dark
brown


15.5
10.9


2400
dark
brown


17.5
6.4


).0
9.6




Bulletin No. 63


Table 2, continued:


SAMPLE NO. M-2994 Sandy common clay


Location:
Dry color:
Water of plasticity:
Dry volume shrinkage:
General plasticity:

Fired Properties:
1
Color: b

Volume shrinkage
(%dry volume):
% absorption: 3


4S 9W sec. 4cd
red gray
30%
6%
sandy, short working, no drying defects.

Cone Temperature (F)


300 2000 2100 2200 2300 2400
uff buff buff buff brown brown


9.0
21.6


10.0
16.5


14.0
15.2


15.0
10.1


Hardness: Very hard at 2,400F


3.0
0.5





Florida Geological Survey


with dolomite residues (called "grits") from their
separation process (Mr. Bill Merchant, Basic,
Inc., personal communication). This material was
used extensively as road base in Gulf County in
the 1960's and 1970's. The source of the
dolomite was originally from Alabama and Ohio,
and is not a local commodity.


Sand and Gravel

Quartz sand (SiO2) is a common component of
the undifferentiated Pliocene through Holocene
age surficial sediments in Gulf County. It is also
the primary constituent of the nearshore conti-
nental shelf deposits (Arthur et al., 1986).
Localized gravel deposits are also present in por-
tions of the undifferentiated sediments in north-
ern Gulf County. Much of this sand, with the
exception of the marine coastal and aeolian
deposits, occurs interbedded with clays. The
beach and dune sand is generally of too fine a
grain size for practical industrial use (Martens,
1928a).
Surficial sand from private borrow pits in the
county is used "as is" for local fill projects. There
are currently no industrial or local governmental
users of sand in Gulf County. As with the other
commodities, future development of this resource
will depend primarily on local demand.


Heavy Minerals

Heavy minerals are comprised of sand-sized
grains of a number of different mineral types,
including ilmenite, zircon, rutile, staurolite, mon-
azite, tourmaline, and others. They are typically
associated with marine sand deposits, and are
often concentrated by wave action along coastal
beaches. Martens (1928b) noted the presence of
thin layers of heavy-mineral concentrates along
the dune front between Cape San Bias and the
northern tip of St. Joe Spit. Table 3 shows the
mineralogical analysis of a sample taken by
Martens about one mile northwest of the south-
ern tip of Cape San Bias.


Table 3: Mineralogical analysis of heavy
concentrate sands from St. Joe
Spit, Gulf County (modified from
Martens, 1928b).

Original sample composition:
68.2% Quartz and feldspar
31.8% Heavy minerals
Percentage of other minerals corrected to
100% after deducting quartz and feldspar (280
grains counted):


Ilmenite
Zircon
Rutile
Monazite
Staurolite
Epidote
Disthene (Kyanite)
Sillimanite
Tourmaline
Hornblende
Leucoxene
Spinel


55.4
15.7
7.5
1.4
3.9
1.1
11.5
0.06
1.8
0.7
0.4
0.4


While similar in composition to the mineable
deposits of northeast Florida, the Gulf County
heavy-mineral deposits are not wide enough or
thick enough to be commercial grade (Martens,
1928b).
Stapor (1973a) included several heavy-mineral
samples from both the western edge of St.
Joseph Spit and from St. Joseph Bay in his gran-
ulometric study of mineral dispersal. He conclud-
ed that the beach face heavy-mineral
concentrations were deposited during periods of
high wave energy, such as storm surges.
Analyses of continental shelf sediments off-
shore of Gulf County show generally similar
heavy-mineral assemblages and proportions.
Arthur et al. (1986) studied samples taken along
three offshore transects south and west of Gulf
County. These authors observed a suite of
heavy-minerals comprised of leucoxine, rutile,
sphene, kyanite, tourmaline, staurolite, zircon,
epidote, sillimanite, and amphibole hornblendee).




Bulletin No. 63


The offshore deposits are most likely from the
same source as the beach deposits, having been
carried into the area from the crystalline belt of
the southern Appalachian Piedmont by the
Apalachicola River (Arthur et al., 1986).


Magnesium compounds

Basic, Incorporated (P.O. Box 160, Port St.
Joe, FL, 32456) is the sole producer of magne-
sium compounds in Florida. This company uti-
lizes a mixture of imported calcined dolomite and
seawater from St. Joseph Bay to produce mag-
nesium oxide and magnesium hydroxide (Mr. Bill
Merchant, Basic, Inc., personal communication).
The calcined (treated by heating to high tempera-
ture) dolomite is shipped in by rail from Alabama
and Ohio. Approximately one-half of the total
compound product is present in the calcined
dolomite as magnesium oxide (MgO) when it
arrives at the plant. The seawater process pro-
duces the other half of the total product in the
form of magnesium hydroxide (Mg(OH)2) precipi-
tate. As the seawater and dolomite are mixed,
the magnesium chloride in seawater reacts with
the calcium hydroxide from the calcined
dolomite, producing magnesium hydroxide and
calcium chloride. This reaction is summarized in
the following equation:

MgCI2 + Ca(OH)2 = Mg(OH)2 + CaCI2
Approximately 16 pounds of magnesium com-
pound is produced for each 1,000 gallons of sea-
water used. The magnesium hydroxide slurry is
filtered to remove water, and the precipitate is
then fired in a rotary kiln. Current production from
the Basic, Incorporated plant at Port St. Joe is
proprietary, but is likely in excess of 10,000 tons
per year. Magnesium oxide is used in the pro-
duction of chemicals, insulation, pulp and paper,
rayon, fertilizers, medicines, rubber, building
materials, and in refractory processes.
Magnesium hydroxide is used in water purifica-
tion processes, pharmaceuticals, and in sugar
refining.


The magnesium reserves in seawater are
unlimited. Aside from the costs of importing the
calcined dolomite, worldwide demand and for-
eign competition determine the economics of
production. Countries such as China can pro-
duce inexpensive, government subsidized mag-
nesium in the form of periclase (Bill Merchant,
personal communication). Therefore, the future
of magnesium production in Gulf County is tied
strongly to world market conditions as well as
international trade agreements.


Petroleum

To date, thirteen oil exploration wells have
been drilled in Gulf County (see Figure 22).
While one had a minor petroleum show, all were
plugged and abandoned as dry holes shortly
after drilling.
The oldest oil wells in the county date to the
mid-1940's and early 1950's. These wells target-
ed Cretaceous sediments, probably in an attempt
to locate a southeastern extension of the produc-
tive Tuscaloosa trend of southwestern Alabama.
None of the earliest wells exceeded 9,000 feet in
depth, and all were dry holes.
After the discovery in 1970 of oil in the
Jurassic Smackover Formation and Norphlet
Sandstone in the Jay Field, Santa Rosa County,
a renewed exploration program was extended by
several companies into the Apalachicola
Embayment area of Gulf County. The Smackover/
Formation is present in the westernmost panhan-
dle, and is absent in all of the central panhandle
except the Apalachicola Embayment area
(Applegate et al., 1978). In the early-to-mid-
1970's, Charter Exploration, Exxon, Hunt Oil, and
Mesa Petroleum drilled a series of wells trending
northwest-southeast through Gulf County. These
wells tested the central panhandle portion of the
Jurassic Smackover Formation and Norphlet
Sandstone units, stopping at depths ranging from
13,284 to 14,570 feet below land surface. Of
these wells, only the Hunt Oil Company's
International Paper Co. 30-4 (Permit 746) in






Florida Geological Survey

CALHOUN CO.


R 11W R 10 W R 9 W
U ) W-12509
o --PERMIT 746 I
-0 HUNT OIL CO., INTERNATIONAL PAPER CO. 30-4, #1 ,
81/13,284 I I




SW-13341 /
I4 PERMIT 846
I EXXON, NEAL LUMBER CO. 20-3, #1
59/13,587
+W-1468
PERMIT 48
PURE OIL CO., E.L. MCMILLIAN #1 -
49/5,069


0I W-1469
PURE OIL CO.,
S43/5,606

PERMIT 95
MESA PETI
S47/14,186
~W_____-3301
SW-1462 PERMIT
R-P RUIT 40 A.R. TE


PURE OIL CO., ST. JOE PAPER CO. #3
24/5,025


30/4,95


R8W


I-

uJ
m

-J

KATE GASKINS#1


7
ROLEUM, ST. JOE PAPER CO. 29-4, #1

194
MPLE-A.W. WILLIAMS, MARY E. LISTER #1
5
I


W-914 I
PURE OILCO., HOPKINS #1
32/8,708
W-1470
PURE OILCO., HOPKINS #2 I
33/7,255 | e/


CO. #1


W-12617
PERMIT 762 /
CHARTER EXPLORATION, ST. JOE APER CO. 12-4, #6
22/14,570.\ / \
SW-12483 "
PERMIT 670 -
CHARTER EXPLORATION, ST. JOE PAPER CO. 26-4, #1
33/14,290


FGS150391


EXPLANATION
MILES
0 1 2 3 4 5 FGS ACCESSION NO.
I FLORIDA PERMIT NUMBER
rR OPERATOR, WELL NAME
0 2 4 6 8 KELLY BUSHING ELEVATION/TOTAL DEPTH BELOW KELLY BUSHING
KILOMETERS

Figure 22. Map showing locations of oil test wells in Gulf County.




Bulletin No. 63


northwestern Gulf County contained oil. The oil
was contained in a dense, impermeable section
of Smackover Formation limestone and in an
underlying calcareous sandstone, with low per-
meabilities and porosity (Applegate et al., 1978).
Due to the low permeability and porosity of the
host rock, the oil was non-recoverable and the
well was plugged and abandoned in 1974.
The Smackover Formation and Norphlet
Sandstone still offer potential as petroleum


sources in Gulf County. Faulting within the
Smackover Formation as well as stratigraphic
pinchouts along the flanks of the igneous intru-
sive bodies on which the Smackover sediments
were deposited may provide traps for economic
accumulations of oil (Applegate et al., 1978). As
rising petroleum prices and dwindling supplies
revitalize the oil industry, the Gulf County area
may be an area of increased exploration activity.





Florida Geological Survey


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Florida Geological Survey


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48





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