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






DIVISION OF RESOURCE MANAGEMENT
Jeremy A. Craft, Director





FLORIDA GEOLOGICAL SURVEY
Walter Schmidt, State Geologist and Chief












OPEN FILE REPORT NO. 43

THE GEOMORPHOLOGY AND GEOLOGY OF LIBERTY COUNTY, FLORIDA

BY

Frank R. Rupert


gpelSJ 5F rL3RIDA LIBRARIES







FLORIDA GEOLOGICAL SURVEY
Tallahassee
1991

























L I DA Y










The geomorphology and geology of Liberty County, Florida


Frank R. Rupert, P.G. No. 149


GEOMORPHOLOGY

Liberty County is situated in the Northern Zone
geomorphic province of White (1970), which
includes the northern Florida peninsula and all of
the panhandle. In this portion of the east-central
Florida panhandle, the Northern Zone is divided
into four geomorphic subzones based primarily on
topographic elevations. These include the Gulf
Coastal Lowlands, Beacon Slope, the Tallahassee
Hills, and the River Valley Lowlands (Figure 1).
The Gulf Coastal Lowlands comprise much of
southern Liberty County. This subzone is


characterized by a generally flat and often swampy,
seaward-sloping, sandy plain. Most of the lowlands
area is ancient marine terrace, shaped by high-
standing Pleistocene seas. Today, much of southern
Liberty County is covered by shallow, densly-
wooded swamp-like areas called "bays", and poorly-
defined creeks. Elevations in the Gulf Coastal
Lowlands of Liberty County range from between 20
and 25 feet above mean sea level (MSL) at the
southern end of the county to approximately 100
feet above MSL where the lowlands meet the higher
slopes in northern Liberty County.
An elevationally-transistional gemorphic zone


EXPLANATION

STATEICOUNTY ROAD
CORE
": CROSS SECTION LOCATION

E TALLAHASSEE HILLS
BEACON SLOPE
GULF COASTAL LOWLANDS
APALACHICOLA RIVER
VALLEY LOWLANDS
3 OCHLOCKONEE RIVER
J VALLEY LOWLANDS
-T- CODY SCARP

MILES
0 1 2345
0 2 4 I8
024KILOMETERS
KILOMETERS


Figure 1: Geomorphic and cross section location map of Liberty County.








named the Beacon Slope (White et al., 1964)
separates the Gulf Coastal Lowlands from the
siliciclastic hills of northern Liberty County. The
Beacon Slope is a uniformly-sloping, ramp-like
feature linking the topographically higher
Tallahassee Hills on the north with the Gulf Coastal
Lowlands, Near-surface sediments are largely
siliclastics overlying karstic limestone. Swampy
depressions and cover-subsidence sinks are common
throughout this terrain. In Liberty County,
elevations range from about 100 feet MSL at the
southern edge of the slope to approximately 200
feet MSL at the northern edge, where it adjoins the
Cody Scarp. The origin of the Beacon Slope is
uncertain, but it is most likely an erosional feature
associated with the higher sea level stands of the
Pleistocene.
A relict southward facing marine escapment
named the Cody Scarp (Puri and Vernon, 1964)
forms the boundary between the Beacon Slope and
the topographically higher Tallahssee Hills in
northernmost Liberty County. This feature spans
much of northern Florida, and is one of the most
persistent topographic breaks in the state. The
Cody Scarp has been erosionally obscured in most
of northern Liberty County. In the northeastern
part of the county, the scarp rises from a toe
elevation of approximately 205 feet MSL to a crest
of about 220 feet MSL, marking the southern extent
of the Tallahassee Hills geomorphic zone.
The Tallahassee Hills (Cooke, 1939) are a series
of topographic highlands spanning the northern
edge of the eastern Florida panhandle. They are
part of the Northern Highlands geomorphic
province, which is thought to be a stream-dissected
remnant of a once continuous highland plain
spanning southern Georgia and northern Florida.
The Tallahassee Hills are capped by deltaic to
shallow marine, clayey sands, silts and clays.
Elevations of the hills within Liberty County vary
from approximately 220 feet MSL at the crest of the
Cody Scarp to nearly 250 feet MSL at the northern
county boundary. The modern hilly topography is
the result of post-depositional dissection and erosion
by running water. Steep bluffs occur in
northwestern Liberty County, where the Tallahassee
Hills end abruptly at the floodplain of the
Apalachicola River. The bluffs commonly stand 150
feet or more above the floor of the floodplain,
exposing Miocene to Holocene age strata. Alum
Bluff, located about 2.5 miles northwest of Bristol
on the Apalachicola River, is one of the best
geologic exposures in Florida (Schmidt, 1983;
Johnson, 1989).


The river bluffs are commonly dissected by a
series of deep, east-west trending ravines containing
small creeks which drain into the Apalachicola
River. Many of these ravines extend several miles
east of the river, ending at so-called "steepheads"
(Sellards and Gunter, 1918). Steepheads form from
lateral undercutting of the sandy surficial sediments
by water seeping out of the surficial aquifer system.
Ground water percolates downward through the
surficial sediments until it encounters a clay or marl.
It then travels horizontally over the less permeable
strata and emerges as a small spring or seep at a
bluff face. Gradually, the flowing water undermines
the overburden material, which slumps off forming
a semicircular, steep-walled head. As undermining
and slumping continue through time, the steephead
migrates laterally away from the original bluff face,
cutting a ravine as it progresses. Other steepheads
may branch off from the original ravine, forming a
dendritic series of smaller ravines feeding the parent
ravine.
The Apalachicola and Ochlockonee Rivers are
the major streams flowing in Liberty County. The
Apalachicola River forms the western county
boundary with adjacent Calhoun County. In
northwestern Liberty County, the broad valley of the
Apachicola averages 50 feet MSL in elevation. The
river meanders southwestward through a three-mile
wide valley, which gradually descends to an
elevation of about 25 feet MSL at the southern edge
of Liberty County. Here, the valley coalesces into
the swampy terrain of the Gulf Coastal Lowlands.
The valley comprises a geomorphic subzone named
the Apalachicola River Valley Lowlands.
The Ochlockonee River forms the eastern
Liberty County boundary with Leon and Wakulla
Counties. Originating in Georgia, the river is
dammed as a hydroelectric power source just above
Highway 20 in Leon County, forming Lake Talquin.
South of the dam, the Ochlockonee meanders over
a broad, swampy valley averaging about one mile
wide. This valley comprises the Ochlockonee River
Valley Lowlands geomorphic zone. In northeastern
Liberty County, the river valley is approximately 40
feet above MSL. Numerous small creeks contribute
to the river along its course, and oxbow lakes are
common along the northern stretch of the river. In
southeastern Liberty County, .the valley broadens
considerably, merging with the low swampy "bays"
of the Apalachicola National Forest. Elevations
here average about 10 feet above MSL. The
Ochlockonee empties into Apalachee Bay, southeast
of Liberty County.
A number of small creeks drain the flat,









swampy terrain of central Liberty County, and
empty into the Apalchicola and Ochlockonee Rivers.
Telogia Creek is the largest of these; it enters
northeastern Liberty County from adjacent Gadsden
County, arcs through the north central portion of
the county, and joins the Ochlockonee River
southeast of Hosford.

GEOLOGY

Liberty County is underlain by hundreds of feet
of marine limestones, dolomites, sands, and clays.
The oldest rocks recovered from deep oil test well
drilling in this county were Paleozoic Erathem (570
to 250 million years ago) igneous rocks at depths of
approximately 12,000 feet below land surface (bls)
(Applegate et al., 1978)). The youngest sediments
present in the county are Pleistocene and Holocene
(1.8 million years old to recent) alluvium and
marine terrace sands and clays.
The Mesozoic Erathem (250 to 65 million years
ago) and early Cenozoic Erathem (Paleocene and
Eocene Series, 65 to 38 million years ago) rocks
underlying Liberty County are largely marine
carbonates and interbedded siliciclastics lying at
depths penetrated only by deep oil test wells. Most
water wells in Liberty County draw from Oligocene
and Miocene (38 to 5 million years old) strata at
depths of 500 feet or less bls. One deep municipal
well taps Eocene (40 to 38 million years ago)
limestone. These rocks function as important
freshwater aquifers for the region. For the
purposes of this report, the discussion of the
stratigraphy of Liberty County will be limited to
these Eocene and younger sediments. Figure 1
shows the geologic cross section locations, and
Figures 2 and 3 illustrate the shallow stratigraphy of
Liberty County. Most of the geologic data cited in
this study is taken from Schmidt (1984), Puri and
Vernon,(1964), and from Florida Geological Survey
well log files.

Eocene Series
Ocala Group

The Ocala Group (Puri, 1957) comprises a
series of Upper Eocene (41 to 38 million years old)
marine limestone units which underlie most of
Florida. In Liberty County, sediments of the Ocala
Group are typically white to very pale orange,
slightly dolomitic, highly microfossiliferous
calcarenitic limestone. It is highly porous, and an
important component of the Floridan aquifer
system. The Ocala Group was penetrated at a


depth of 660 feet bls in one municipal water well in
the city of Bristol. Because this unit lies in excess
of 600 feet bls countywide, it is not used extensively
as a water source in Liberty County. The Ocala
Group is overlain by the Oligocene Marianna and
Suwannee Limestones.

Oligocene Series
Marianna Limestone

The Marianna Limestone (Matson and Clapp,
1909) consists of gray to very light orange, chalky,
fossiliferous marine limestone frequently containing
large, coin-shaped Lepidocyclina foraminifera
fossils. The Marianna Limestone is Lower
Oligocene in age (38 to 33 million years old). This
unit was penetrated by only one core (W-6901) in
northwestern Liberty County, and the extent of its
occurrence under the county is uncertain due to a
general lack of well coverage. It probably underlies
western Liberty County at depths in excess of 400
feet bis, but pinches out to the east. The Marianna
Limestone is overlain by sediments of the Upper
Oligocene Suwannee Limestone.

Suwannee Limestone

The Suwannee Limestone (Cooke and
Mansfield, 1936) is an Upper Oligocene (33 to 25
million years old) light gray to yellowish-gray, well
indurated, often dolomitized marine limestone. It
typically contains abundant fossils including
foraminifera, mollusks and echinoids. Depth to the
Suwannee Limestone ranges between about 350 and
450 feet bls. Thickness of the unit is variable, and
usually exceeds 100 feet. It generally dips and
thickens to the southwest into the trough of the
Apalachicola Embayment. The Suwannee
Limestone is a component of the Floridan aquifer
system. It unconformibly overlies the Oligocene
Marianna Limestone, where present, or Eocene
Ocala Group carbonates. The Suwannee Limestone
is overlain by Miocene sediments of the
Chattahoochee, St. Marks, or Chipola Formations,
or by Bruce Creek Limestone.

Miocene and Pliocene Series
Chattahoochee and St. Marks Formations

The Lower Miocene (25 to 20 million years old)
Chattahoochee and St. Marks Formations (Dall and
Stanley-Brown, 1894; Finch, 1823) overlie the
Suwannee. Limestone in Liberty County. The















300


o0-. 200



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I00



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020


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varICAL 81AGGINATION IS APPOXIMATILY ITS TIMIS TRUe SCALE


Figure 2: Geologic cross section A-A'.





B u







I0 g.US .o0

,.."E STOsRRYA r C

-40 1

-40 -200



-100.C 1



-120 0-

VERTICAL EIXAGGRATION IS APPROXIMATELY tS TIMES TRUE SCALE. KI


Figure 3: Geologic cross section B-B'.
-^-- -- ^ ^ = ^























Figure 3: Geologic cross section B-B'.


MILES
1 2 3 4 5

ILOMETERS


MILES
2 3 4 S
4 s
METERSS









Chattahoochee Formation is generally a very pale
orange to white or light gray, often quartz sandy,
phosphoritic, dolomitic marine limestone. It occurs
under northern and western Liberty County. The
age-equivalent St. Marks Formation is a white to
cream, fossiliferous calcilutite limestone underlying
the southern and eastern portions of the county.
The two units interfinger in north-central Liberty
County (Schmidt, 1984).
In some cases, post-depositional ground-water
alteration of the carbonates in portions of the
central and western panhandle has made
differentiation of the Chattahoochee and St. Marks
Formations from the underlying Suwannee
Limestone and overlying Bruce Creek Limestone
difficult or impossible. Where defineable in Liberty
County however, the top of the Chattahoochee/St.
Marks Formations varies from about 75 feet to 200
feet bls. Thickness averages about 200 feet. As
with the underlying Suwannee Limestone, the
Chattahoochee and St. Marks Formations dip to the
west-southwest, grading into or interfingering with
the Bruce Creek Limestone along the southern edge
of Liberty County. The Chattahoochee and St.
Marks Formations are units of the Floridan aquifer
system, and many rural Liberty County wells draw
from these formations. Along the southern edge of
the county, the Bruce Creek Limestone overlies or
grades into the Chattahoochee and St. Marks
Formations. In northernmost Liberty County, the
Bruce Creek Limestone is absent, and the
Chattahoochee Formation is overlain by sediments
of the Miocene Chipola Formation or Torreya
Formation.

Chipola Formation

The Chipola Formation (Burns, 1889) is a
Lower Miocene carbonate unit underlying portions
of northernmost Liberty County. It is typically
comprised of a yellowish-gray to light gray,
moderately-to-well indurated, quartz sandy, marine
limestone. It is exposed as the basal unit at Alum
Bluff, north of Bristol on the Apalachicola River.
Here it commonly contains abundant fossil
mollusks. The Chipola Formation varies between
about 60 and 200 feet bis in Liberty County, and
reaches a maximum of about 50 feet thick. It is
overlain by sediments of the Middle Miocene
Torreya Formation or the Upper Pliocene Jackson
Bluff Formation.


Hawthorn Group
Torreya Formation

The Lower Miocene Torreya Formation (Banks
and Hunter, 1973; Huddlestun and Hunter, 1982;
Scott, 1988) of the Hawthorn Group underlies
northern Liberty County, extending from Leon
County westward to Rock Bluff on the Apalachicola
River. In Liberty County, the Torreya Formation is
typically a siliclastic unit consisting of light gray to
pale orange quartz sands and clays, commonly
containing variable amounts of phosphorite. The
lower portion of the unit is commonly comprised
of a light olive gray, sandy, phosphoritic, and locally
dolomitic limestone. Depth to the top of this
formation in Liberty County varies considerably,
ranging from about 10 feet to 100 feet bls. The
thickness of the unit is also highly variable, reaching
100 to 200 feet thick in the northeastern portion of
the county. The Torreya Formation is
unconformibly overlain by sediments of the
Intracoastal or Jackson Bluff Formations.

Bruce Creek Limestone

The Middle Miocene (17 to 10 million years
old) Bruce Creek Limestone (Huddlestun, 1984) is
a white to yellowish-gray, fossiliferous, calcarenitic,
marine limestone underlying most of central and
southern Liberty County. It is often highly
microfossiliferous, molluskan moldic, and in some
areas, dolomitic. From north-central Liberty
County, this unit thickens and dips rapidly towards
the south, into the trough of the Apalachicola
Embayment. The Bruce Creek Limestone varies in
depth from approximately 125 feet bls at its
northern limit in central Liberty County to over 200
feet bls in the southern portion of the county. Its
thickness increases rapidly from zero in the central
part of the county southward to about 200 feet near
the Liberty-Franklin county line. The Bruce Creek
Limestone is the uppermost unit of the Floridan
aquifer system in Liberty County. It is overlain by
sediments of the Intracoastal, Chipola, or Torreya
Formations.

Intracoastal Formation

The Intracoastal Formation (Huddlestun, 1984;
Schmidt and Clark, 1980) is comprised of a
yellowish-gray, abundantly microfossiliferous, sandy,
poorly-indurated, marine limestone. It spans an age
range of Middle Miocene to Late Pliocene (17 to 2








million years old), with the Late Miocene and Early
Pliocene portions absent due to a hiatus. Like the
underlying Bruce Creek Limestone, the updip limit
of the Intracoastal Formation occurs along a west-
to-east line under northern Liberty County. The
formation is generally absent north of the town of
Hosford. It thickens and dips to the south-
southwest, approaching 100 feet in thickness in the
southeastern corner of the county. Depth to the top
of the unit in Liberty County is highly variable,
generally ranging between 50 and 150 feet bls. The
Intracoastal Formation is locally overlain by
sediments of the Chipola, Torreya, or Jackson Bluff
Formations.

Pliocene Series
Jackson Bluff Formation

The Upper Pliocene (3 to 1.8 million years old)
Jackson Bluff Formation (Puri and Vernon, 1964) is
predominantly comprised of light gray to olive gray,
poorly-consolidated, clayey quartz sands and sandy
shell beds. It overlies the Chipola, Torreya, and
Intracoastal Formations in Liberty County. The
Jackson Bluff Formation is a thin unit, attaining a
maximum thickness of about 30 feet thick in
western Liberty County. Depth to the top of the
Jackson Bluff is variable throughout the county,
ranging from 20 to 100 feet bls. It crops out locally
at Alum Bluff along the Apalachicola River. In
northern Liberty County, it is overlain by the
Citronelle Formation and undifferentiated
sediments. In the southern part of the county, it is
covered by undifferentiated sands and clays.

Citronelle Formation

The reddish, clayey, coarse quartz sands and
gravels of the Upper Pliocene Citronelle Formation
(Matson, 1916) blanket the Tallahassee Hills in
northernmost Liberty County. Believed to be of
fluvial origin, the characteristic Citronelle Formation
sediments are comprised of cross-bedded sands,
gravels, and clays. Portions of the Liberty County
surficial deposits may represent reworked and
redeposited Citronelle sediments, transported from
the eroding highlands to the north. Thickness
generally varies between 20 and. 80 feet, and the
Citronelle deposits comprise the surficial sediments
in their area of occurence. Within Liberty County,
the Citronelle Formation sediments grade laterally
southward into a series of undifferentiated quartz
sands and clayey sands.


Pllo-Pleistocene and Holocene Series
Undifferentiated Sand and Clays

Much of central and southern Liberty County is
covered by surficial quartz sands, clays, clayey sands,
and gravels. Due to the massive and discontinuous
nature of many of these units, they are lumped
together as undifferentiated deposits. These
deposits represent a mixture of marine and fluvial
siliciclastics associated with Pleistocene (1.8 million
to 10,000 years old) sea level highstands and the
prograding Apalachicola delta. The modern soil
profiles probably evolved during the Late
Pleistocene and Holocene (10,000 years ago to
present). Holocene alluvium, in the form of river-
borne clays and quartz sand and gravel, is deposited
along the banks and bars of the Apalachicola and
Ochlockonee Rivers, which border Liberty County.

GROUND WATER

Ground water is water that fills the pore spaces
in subsurface rocks and sediments. This water is
derived principally from precipitation within Liberty
and adjacent counties. The bulk of Liberty County's
consumptive water is withdrawn from ground water
aquifers. Three main aquifers are present under
Liberty County. In order of increasing depth, these
are the surficial aquifer system, the intermediate
aquifer and confining system, and the Floridan
aquifer system. Data on aquifer extent and
thicknesses are taken from Scott et al., 1991 (in
preparation).

Surficial aquifer system

The surficial aquifer system is the uppermost
freshwater aquifer in Liberty County. This non-
artesian aquifer is largely contained within the
undifferentiated sands and the Citronelle Formation
sediments. It is present under most of Liberty
County, reaching a maximum measured thickness of
about 118 feet in the north-central part of the
county. In central and southern Liberty County it
is highly variable in thickness, ranging from about
20 to 70 feet thick. The surficial aquifer system is
unconfined, and its upper surface is the water table.
In general, the water-table elevation fluctuates with
precipitation rate and conforms to the topography
of the land surface. Recharge to the aquifer is
largely through rainfall percolating through the
loose surficial sediments, and to a lesser extent, by
upward seepage from the underlying intermediate
aquifer system. The surficial aquifer system is not









used extensively as a water source in the county.

Intermediate aquifer system or confining unit

The intermediate aquifer system underlies the
surficial aquifer system in Liberty County, and is
largely contained within the Torreya, Intracoastal,
Chipola and Jackson Bluff Formations. Permeable
beds within the intermediate aquifer system vary
considerably in thickness over the areal extent of
the aquifer. In general, the aquifer ranges from 100
to 200 feet in thickness under Liberty County,
corresponding to the variable thicknesses of the
geologic formations containing it. The top of the
intermediate is also highly variable, ranging from
surface outcrop along rivers and creeks in
northeastern and northwestern Liberty County, to
20 feet or less bls at the southern edge of the
county, to as much as 100 feet bls under the
Tallahassee Hills in the.northernmost tip of the
county. Some rural wells draw from this unit, but
the intermediate aquifer system is not widely used.
as a potable water source in this area. Low-
permeability beds in the basal intermediate aquifer
system may locally function as confining units to the
underlying Floridan aquifer system.

Floridan aquifer system

The Floridan aquifer system is comprised of
hundreds of feet of Eocene through Miocene age
marine limestones, including the Ocala Group, the
Marianna and Suwannee Limestones, and where
present, the Chattahoochee Formation, St. Marks
Formation and Bruce Creek Limestone. Depth to
the top of the Floridan aquifer system varies from
about 50 feet bls at the southern edge of the county
to nearly 200 feet in the west-central portion. It is
the principle source of drinking water in Liberty
County. The Floridan aquifer system occurs as an
artesian aquifer under the entire county. Surface
springs issuing from this aquifer are absent in
Liberty County. Most of the regional recharge
occurs further to the north in Jackson County where
the strata comprising the Floridan aquifer system
crop out at the surface.

MINERAL RESOURCES

The principal mineral resources occurring in
Liberty County are sand and gravel, clay, limestone,
peat, phosphate, heavy minerals, and petroleum.
The following discussion summarizes the current
mining potential of each commodity in the county.


Sand and gravel

Pleistocene marine terrace sands and alluvium
and Pliocene Citronelle Formation sediments are
comprised of quartz sand with varying amounts of
clay matrix. These deposits blanket much of. the
county. A number of shallow private pits in Liberty
County are worked for locally-used fill sand. In
addition, the U.S. Forest Service routinely digs
clayey sand for use in stabilizing forest roads in
southern Liberty County (Patterson et al., 1986).
None of this sand is utilized commercially.
Patterson et al. (1986) report a quartz sand and
gravel stratum lying at a depth of about 15 feet
below the Apalachicola National Forest in southern
Liberty County. Although this deposit is of
commercial quality, its remote location and the
thinness of the deposit (about 13 feet thick)
preclude commercial mining. In addition, sand and
gravel products are produced more economically in
other parts of the Florida panhandle, thus lessening
the potential for large-scale mining in Liberty
County.

Clay

Localized deposits of clay and sandy clay are
also associated with the undifferentiated Pleistocene
and Holocene marine terrace deposits, Holocene
alluvium, and Citronelle Formation sediments.
Most of these clays are contained in and
interbedded with other sediments, and as a result
are relatively impure. Miocene age palygorskite
(attapulgite) fuller's earth clays are mined to the
north in Gadsden County, but no commercial-grade
deposits are known in Liberty County.
Flood-plain clay deposits along the
Apalachicola and Ochlockonee Rivers have been
utilized for brick-making in nearby Calhoun and
Gadsden Counties (Bell, 1924). Bell (1924) tested
clays collected at Estiffanulga Bluff, on the
Apalachicola River in Liberty County, for firing and
working properties. He concluded that the clay was
suitable for common brick, hollow block ware, drain
tile, and earthenware. Commercial exploitation
never occurred.
Patterson et al. (1986) noted the presence of a
sandy, shelly, plastic clay in a test boring in southern
Liberty County in the Apalachicola National Forest.
The sand and shell impurities, as well as the remote
location of the deposit preclude economic mining.
Reserve estimates of the clay deposits in Liberty
County have not been made. Future exploitation








million years old), with the Late Miocene and Early
Pliocene portions absent due to a hiatus. Like the
underlying Bruce Creek Limestone, the updip limit
of the Intracoastal Formation occurs along a west-
to-east line under northern Liberty County. The
formation is generally absent north of the town of
Hosford. It thickens and dips to the south-
southwest, approaching 100 feet in thickness in the
southeastern corner of the county. Depth to the top
of the unit in Liberty County is highly variable,
generally ranging between 50 and 150 feet bls. The
Intracoastal Formation is locally overlain by
sediments of the Chipola, Torreya, or Jackson Bluff
Formations.

Pliocene Series
Jackson Bluff Formation

The Upper Pliocene (3 to 1.8 million years old)
Jackson Bluff Formation (Puri and Vernon, 1964) is
predominantly comprised of light gray to olive gray,
poorly-consolidated, clayey quartz sands and sandy
shell beds. It overlies the Chipola, Torreya, and
Intracoastal Formations in Liberty County. The
Jackson Bluff Formation is a thin unit, attaining a
maximum thickness of about 30 feet thick in
western Liberty County. Depth to the top of the
Jackson Bluff is variable throughout the county,
ranging from 20 to 100 feet bls. It crops out locally
at Alum Bluff along the Apalachicola River. In
northern Liberty County, it is overlain by the
Citronelle Formation and undifferentiated
sediments. In the southern part of the county, it is
covered by undifferentiated sands and clays.

Citronelle Formation

The reddish, clayey, coarse quartz sands and
gravels of the Upper Pliocene Citronelle Formation
(Matson, 1916) blanket the Tallahassee Hills in
northernmost Liberty County. Believed to be of
fluvial origin, the characteristic Citronelle Formation
sediments are comprised of cross-bedded sands,
gravels, and clays. Portions of the Liberty County
surficial deposits may represent reworked and
redeposited Citronelle sediments, transported from
the eroding highlands to the north. Thickness
generally varies between 20 and. 80 feet, and the
Citronelle deposits comprise the surficial sediments
in their area of occurence. Within Liberty County,
the Citronelle Formation sediments grade laterally
southward into a series of undifferentiated quartz
sands and clayey sands.


Pllo-Pleistocene and Holocene Series
Undifferentiated Sand and Clays

Much of central and southern Liberty County is
covered by surficial quartz sands, clays, clayey sands,
and gravels. Due to the massive and discontinuous
nature of many of these units, they are lumped
together as undifferentiated deposits. These
deposits represent a mixture of marine and fluvial
siliciclastics associated with Pleistocene (1.8 million
to 10,000 years old) sea level highstands and the
prograding Apalachicola delta. The modern soil
profiles probably evolved during the Late
Pleistocene and Holocene (10,000 years ago to
present). Holocene alluvium, in the form of river-
borne clays and quartz sand and gravel, is deposited
along the banks and bars of the Apalachicola and
Ochlockonee Rivers, which border Liberty County.

GROUND WATER

Ground water is water that fills the pore spaces
in subsurface rocks and sediments. This water is
derived principally from precipitation within Liberty
and adjacent counties. The bulk of Liberty County's
consumptive water is withdrawn from ground water
aquifers. Three main aquifers are present under
Liberty County. In order of increasing depth, these
are the surficial aquifer system, the intermediate
aquifer and confining system, and the Floridan
aquifer system. Data on aquifer extent and
thicknesses are taken from Scott et al., 1991 (in
preparation).

Surficial aquifer system

The surficial aquifer system is the uppermost
freshwater aquifer in Liberty County. This non-
artesian aquifer is largely contained within the
undifferentiated sands and the Citronelle Formation
sediments. It is present under most of Liberty
County, reaching a maximum measured thickness of
about 118 feet in the north-central part of the
county. In central and southern Liberty County it
is highly variable in thickness, ranging from about
20 to 70 feet thick. The surficial aquifer system is
unconfined, and its upper surface is the water table.
In general, the water-table elevation fluctuates with
precipitation rate and conforms to the topography
of the land surface. Recharge to the aquifer is
largely through rainfall percolating through the
loose surficial sediments, and to a lesser extent, by
upward seepage from the underlying intermediate
aquifer system. The surficial aquifer system is not









used extensively as a water source in the county.

Intermediate aquifer system or confining unit

The intermediate aquifer system underlies the
surficial aquifer system in Liberty County, and is
largely contained within the Torreya, Intracoastal,
Chipola and Jackson Bluff Formations. Permeable
beds within the intermediate aquifer system vary
considerably in thickness over the areal extent of
the aquifer. In general, the aquifer ranges from 100
to 200 feet in thickness under Liberty County,
corresponding to the variable thicknesses of the
geologic formations containing it. The top of the
intermediate is also highly variable, ranging from
surface outcrop along rivers and creeks in
northeastern and northwestern Liberty County, to
20 feet or less bls at the southern edge of the
county, to as much as 100 feet bls under the
Tallahassee Hills in the.northernmost tip of the
county. Some rural wells draw from this unit, but
the intermediate aquifer system is not widely used.
as a potable water source in this area. Low-
permeability beds in the basal intermediate aquifer
system may locally function as confining units to the
underlying Floridan aquifer system.

Floridan aquifer system

The Floridan aquifer system is comprised of
hundreds of feet of Eocene through Miocene age
marine limestones, including the Ocala Group, the
Marianna and Suwannee Limestones, and where
present, the Chattahoochee Formation, St. Marks
Formation and Bruce Creek Limestone. Depth to
the top of the Floridan aquifer system varies from
about 50 feet bls at the southern edge of the county
to nearly 200 feet in the west-central portion. It is
the principle source of drinking water in Liberty
County. The Floridan aquifer system occurs as an
artesian aquifer under the entire county. Surface
springs issuing from this aquifer are absent in
Liberty County. Most of the regional recharge
occurs further to the north in Jackson County where
the strata comprising the Floridan aquifer system
crop out at the surface.

MINERAL RESOURCES

The principal mineral resources occurring in
Liberty County are sand and gravel, clay, limestone,
peat, phosphate, heavy minerals, and petroleum.
The following discussion summarizes the current
mining potential of each commodity in the county.


Sand and gravel

Pleistocene marine terrace sands and alluvium
and Pliocene Citronelle Formation sediments are
comprised of quartz sand with varying amounts of
clay matrix. These deposits blanket much of. the
county. A number of shallow private pits in Liberty
County are worked for locally-used fill sand. In
addition, the U.S. Forest Service routinely digs
clayey sand for use in stabilizing forest roads in
southern Liberty County (Patterson et al., 1986).
None of this sand is utilized commercially.
Patterson et al. (1986) report a quartz sand and
gravel stratum lying at a depth of about 15 feet
below the Apalachicola National Forest in southern
Liberty County. Although this deposit is of
commercial quality, its remote location and the
thinness of the deposit (about 13 feet thick)
preclude commercial mining. In addition, sand and
gravel products are produced more economically in
other parts of the Florida panhandle, thus lessening
the potential for large-scale mining in Liberty
County.

Clay

Localized deposits of clay and sandy clay are
also associated with the undifferentiated Pleistocene
and Holocene marine terrace deposits, Holocene
alluvium, and Citronelle Formation sediments.
Most of these clays are contained in and
interbedded with other sediments, and as a result
are relatively impure. Miocene age palygorskite
(attapulgite) fuller's earth clays are mined to the
north in Gadsden County, but no commercial-grade
deposits are known in Liberty County.
Flood-plain clay deposits along the
Apalachicola and Ochlockonee Rivers have been
utilized for brick-making in nearby Calhoun and
Gadsden Counties (Bell, 1924). Bell (1924) tested
clays collected at Estiffanulga Bluff, on the
Apalachicola River in Liberty County, for firing and
working properties. He concluded that the clay was
suitable for common brick, hollow block ware, drain
tile, and earthenware. Commercial exploitation
never occurred.
Patterson et al. (1986) noted the presence of a
sandy, shelly, plastic clay in a test boring in southern
Liberty County in the Apalachicola National Forest.
The sand and shell impurities, as well as the remote
location of the deposit preclude economic mining.
Reserve estimates of the clay deposits in Liberty
County have not been made. Future exploitation








will be largely dependent upon local market
demand.
Limestone

Impure Miocene limestones occur at depth
under most of Liberty County. Most of the
shallower units contain extensive impurities,
including quartz sand. Due to the presence of these
impurities, the overburden thickness (at least 50
feet), and the presence of easily-accessible limestone
deposits at the surface in nearby Jackson County, it
is unlikely that limestone will ever be an economical
commodity in Liberty County.

Peat

Peat deposits form in a wet, reducing
environment when accumulation of organic
materials (vegetation) exceeds the decomposition
rate of that material (Bond et al., 1986). While
such conditions are common in the swampy bays
covering much of the Apalachicola National Forest
in southern Liberty County, only thin layers of non-
commercial peaty material (organic deposits
containing more than 25% ash) are present
(Patterson et al., 1986).

Phosphate

Many of the Miocene and Pliocene formations
underlying Liberty County contain variable
percentages of phosphate sand and granules.
Patterson et al. (1986) reported the phosphate
content of sediments from test borings in southern
Liberty County and adjacent counties to be well
below the minimum commercial percentage. In
addition, most phosphate-bearing strata occur at
depths in excess of 50 feet. These factors preclude
a high mining potential for phosphate in Calhoun
County.

Heavy minerals

Heavy minerals such as rutile, ilmenite, zircon,
staurolite, and others are minor components of the
surficial and near-surface sediments in Liberty
County. Although a county-wide study has not been
conducted, Patterson et al. (1986) determined the
heavy- mineral concentrations in test borings in
southern Liberty County were significantly below
the commercial minimum percentage. In addition,
the wide range of mineral species present rather
than specific concentration of the more valuable
mineral types further reduces the economic


potential of the deposits. Therefore, future mining
potential is low.

Petroleum

Petroleum is produced from the Jurassic-age
Smackover Formation and Norphlet Sandstone west
of Liberty County in the Jay trend of Santa Rosa
County. These formations are also present under
Liberty County, but four oil wells drilled in the
county to test these strata were dry holes
(Applegate et al., 1978; Patterson et al., 1986).
While the prospects for commercial petroleum
production in Liberty County appear slim at
present, only continued exploration of the Jurassic
and older units will ultimately rule out the potential
for the discovery of oil and gas under the county.

REFERENCES

Applegate, A.V., Pontigo, FA., and Rooke, J.H.,
1978, Jurassic Smackover oil prospects in
the Apalachicola Embayment: Oil and Gas
Journal, v. 76, no. 4, p. 80-84.

Banks, J.E., and Hunter, M.E., 1973, Post-Tampa,
Pre-Chipola sediments exposed in Liberty,
Gadsden, Leon, and Wakulla Counties,
Florida: Transactions, Gulf Coast
Association of Geological Societies, v. 23, p.
355-363.

Bell, 0., 1924, A preliminary report on the clays of
Florida (exclusive of Fuller's Earth): in:
Florida Geological Survey 15th Annual
Report, p. 125-127.

Bond, P., Campbell, K.M., and Scott, T.M., 1986,
An overview of peat in Florida and related
issues: Florida Geological Survey
Special Publication 27, 151 p.

Burns, Frank, 1889, Unpublished Field Notes, U.S.
Geological Survey (Referenced in Cooke
and Mossom, 1929, Geology of Florida:
Florida Geological Survey 20th Annual
Report, 103 p.)

Cooke, C.W., 1939, Scenery of Florida interpreted
by a geologist: Florida Geological Survey
Bulletin 17, 118 p.

and Mossom, S., 1929, Geology of
Florida: Florida Geological Survey








will be largely dependent upon local market
demand.
Limestone

Impure Miocene limestones occur at depth
under most of Liberty County. Most of the
shallower units contain extensive impurities,
including quartz sand. Due to the presence of these
impurities, the overburden thickness (at least 50
feet), and the presence of easily-accessible limestone
deposits at the surface in nearby Jackson County, it
is unlikely that limestone will ever be an economical
commodity in Liberty County.

Peat

Peat deposits form in a wet, reducing
environment when accumulation of organic
materials (vegetation) exceeds the decomposition
rate of that material (Bond et al., 1986). While
such conditions are common in the swampy bays
covering much of the Apalachicola National Forest
in southern Liberty County, only thin layers of non-
commercial peaty material (organic deposits
containing more than 25% ash) are present
(Patterson et al., 1986).

Phosphate

Many of the Miocene and Pliocene formations
underlying Liberty County contain variable
percentages of phosphate sand and granules.
Patterson et al. (1986) reported the phosphate
content of sediments from test borings in southern
Liberty County and adjacent counties to be well
below the minimum commercial percentage. In
addition, most phosphate-bearing strata occur at
depths in excess of 50 feet. These factors preclude
a high mining potential for phosphate in Calhoun
County.

Heavy minerals

Heavy minerals such as rutile, ilmenite, zircon,
staurolite, and others are minor components of the
surficial and near-surface sediments in Liberty
County. Although a county-wide study has not been
conducted, Patterson et al. (1986) determined the
heavy- mineral concentrations in test borings in
southern Liberty County were significantly below
the commercial minimum percentage. In addition,
the wide range of mineral species present rather
than specific concentration of the more valuable
mineral types further reduces the economic


potential of the deposits. Therefore, future mining
potential is low.

Petroleum

Petroleum is produced from the Jurassic-age
Smackover Formation and Norphlet Sandstone west
of Liberty County in the Jay trend of Santa Rosa
County. These formations are also present under
Liberty County, but four oil wells drilled in the
county to test these strata were dry holes
(Applegate et al., 1978; Patterson et al., 1986).
While the prospects for commercial petroleum
production in Liberty County appear slim at
present, only continued exploration of the Jurassic
and older units will ultimately rule out the potential
for the discovery of oil and gas under the county.

REFERENCES

Applegate, A.V., Pontigo, FA., and Rooke, J.H.,
1978, Jurassic Smackover oil prospects in
the Apalachicola Embayment: Oil and Gas
Journal, v. 76, no. 4, p. 80-84.

Banks, J.E., and Hunter, M.E., 1973, Post-Tampa,
Pre-Chipola sediments exposed in Liberty,
Gadsden, Leon, and Wakulla Counties,
Florida: Transactions, Gulf Coast
Association of Geological Societies, v. 23, p.
355-363.

Bell, 0., 1924, A preliminary report on the clays of
Florida (exclusive of Fuller's Earth): in:
Florida Geological Survey 15th Annual
Report, p. 125-127.

Bond, P., Campbell, K.M., and Scott, T.M., 1986,
An overview of peat in Florida and related
issues: Florida Geological Survey
Special Publication 27, 151 p.

Burns, Frank, 1889, Unpublished Field Notes, U.S.
Geological Survey (Referenced in Cooke
and Mossom, 1929, Geology of Florida:
Florida Geological Survey 20th Annual
Report, 103 p.)

Cooke, C.W., 1939, Scenery of Florida interpreted
by a geologist: Florida Geological Survey
Bulletin 17, 118 p.

and Mossom, S., 1929, Geology of
Florida: Florida Geological Survey









20th Annual Report, 1927-1928, p. 29-227.

and Mansfield, W., 1936, Suwannee
Limestone of Florida: [abs.] Geological
Society of America Proceedings,
1935, p.71-72.

Dall, W.H., and Stanley-Brown, J., 1894, Cenozoic
geology along the Apalacicola River:
Bulletin of the Geological Society of
America, v. 5, p. 147-170.

Davis, J.H., 1946, The peat deposits of Florida, their
occurence, development, and uses: Florida
Geological Survey Bulletin 30, 250 p.

Finch, J., 1823, Geological essay on the Tertiary
formation in America: American Journal of
Science, v. 7, p. 31-43.

Huddlestun, P.F., 1984, The Neogene stratigraphy of
the central Florida Panhandle: [Ph.D
Dissertation], Florida State University,
Tallahassee, 210 p.

and Hunter, M.E., 1982,
Stratigraphic revision of the Torreya
Formation of Florida (abstract) in: Scott,
T.M., and Upchurch, S., (eds.), Miocene
Symposium of the southeastern United
States: Florida Bureau of Geology Special
Publication 25, p. 210.

Johnson, RA., 1989, Geologic descriptions of
selected exposures in Florida: Florida
Geological Survey Special Publication 30, p.
67.

Matson, G., and Clapp, F., 1909, A preliminary
report on the geology of Florida with
special reference to the stratigraphy:
Florida Geological Survey 2nd Annual
Report, 1908-1909, p. 25-173.

1916, The Pliocene Citronelle
Formation of the Gulf Coastal Plain: U.S.
Geological Survey Professional Paper 98, p.
167-192.

Patterson,, S.H., Cameron, C.C., and Schmidt, W.,
1986, Geology and mineral resource
potential of seven roadless areas in the
Apalachicola National Forest, Liberty
County, Florida: U.S. Geological Survey
Bulletin 1587, 21 p.


Puri, H.S., 1957, Stratigraphy and zonation of the
Ocala Group: Florida Geological Survey
Bulletin 38, 248 p.

and Vernon, R.O., 1964, Summary of
the geology of Florida and a guidebook to
the classic exposures: Florida Geological
Survey Special Publication no. 5 (revised),
312 p.

Schmidt, W., 1983, Cenozoic geology of the
Apalachicola River Area, Northwest
Florida: in: Cenozoic geology of the
Apalachicola River area, northwest Florida:
Southeastern Geological Society Guidebook
No. 25, October 8, 1983, p. 33.

1984, Neogene stratigraphy and
geologic history of the Apalachicola
Embayment, Florida: Florida Geological
Survey Bulletin 58, 146 p.

_, and Clark, M.W., 1980, Geology of
Bay County, Florida: Florida Geological
Survey Bulletin 57, 76 p.

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

Lloyd, J., and Maddox, G., 1991 (in
preparation), Florida's ground water
monitoring network, Volume 1:
Introduction and hydrogeologic framework:
Florida Geological Survey Special
Publication no. 32.

Sellards, E.H., and Gunter, H., 1918, Geology
between the Apalachicola and Ochlockonee
Rivers: Florida Geological Survey
10th Annual Report, p. 27.

White, W., Puri, H., and Vernon, R., 1964,
Unpublished manuscript cited in: Puri, H.
and Vernon, R., 1964, Summary of the
geology of Florida and a guidebook to the
classic exposures: Florida Geological Survey
Special Publication no. 5 (revised), 312 p.

1970, The geomorphology of the
Florida peninsula: Florida Geological
Survey Bulletin 51, 164 p.










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