Geomorphology, geology, and hydrogeology of the Savannas State Reserve, Martin and St. Lucie Counties, Florida /

Material Information

Geomorphology, geology, and hydrogeology of the Savannas State Reserve, Martin and St. Lucie Counties, Florida /
Rupert, Frank
Florida Geological Survey
Place of Publication:
Tallahassee, Fla.
Florida Geological Survey
Publication Date:
Physical Description:
8 p. : maps ; 28 cm.


Subjects / Keywords:
Geomorphology -- Florida -- Martin County ( lcsh )
Geomorphology -- Florida -- Saint Lucie County ( lcsh )
Geology -- Florida -- Martin County ( lcsh )
Geology -- Florida -- Saint Lucie County ( lcsh )
Hydrogeology -- Florida -- Martin County ( lcsh )
Hydrogeology -- Florida -- Saint Lucie County ( lcsh )
Savannas State Reserve (Fla.) ( lcsh )
St. Lucie County ( local )
City of Ocala ( local )
Martin County ( local )
Aquifers ( jstor )
Savannas ( jstor )
Limestones ( jstor )
Counties ( jstor )
Geology ( jstor )
non-fiction ( marcgt )


Includes bibliographical references.
General Note:
Florida Geological Survey open file report 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:
26606138 ( OCLC )


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State of Florida
Department of Natural Resources
Virginia Wetherell, Executive Director

Division of Resource Management
Jeremy Craft, Director

Florida Geological Survey
Walt Schmidt, State Geologist

Open File Report 51

Geomorphology, Geology, and Hydrogeology
of the Savannas State Reserve, Martin
and St. Lucie Counties, Florida


Frank R. Rupert

Florida Geological Survey
Tallahassee, Florida


Geomorphology, Geology, and Hydrogeology
of the Savannas State Reserve, Martin
and St. Lucie Counties, Florida

Frank R. Rupert, P.G. 149
Florida Geological Survey


Many of Florida's natural ecosystems
are rapidly disappearing as the state's
burgeoning population expands. To protect
these unique natural features for the
enjoyment of future generations, the Florida
Legislature mandated the purchase of lands,
both submerged and dry, exhibiting
exceptional biological and aesthetic value. As
a result of the mandates, a number of areas
best representing natural Florida ecosystems
were acquired by the State for permanent
protection. These lands are divided into two
broad categories: aquatic preserves, which
consist of submerged lands and the overlying
waters, and the generally dry land State
Reserves, which may contain associated
wetlands. The Savannas State Reserve is one
of a series of reserves and preserves statewide
which will be maintained in their natural or
existing conditions. The Florida Department
of Natural Resources (FDNR) is charged with
ensuring the quality and preservation of these
exceptional areas. This is accomplished
through the implementation of standardized
management plans, law enforcement, and
public education programs.
Geological processes have played the
dominant role in the evolution of natural
Florida. Many of the unique ecosystems now
protected in preserves and reserves exist as a
result of the particular bedrock geology, the
hydrogeology, the local geomorphology, or
some unique combination of these factors.
Therefore, an understanding of the geology is
integral to formulating effective land and
resource management policy for these natural
areas. To this end, the Florida Geological
Survey prepares, upon request, reports on the
local geology for the aquatic preserves and

State reserve areas. The following text was
prepared at the request of the FDNR Office
of Land Use Planning and Biological Services.


The Savannas State Reserve is situated
on the eastern edge of the Eastern Valley
geomorphic province of the Atlantic Coastal
Lowlands of White (1970). This province
extends eastward from the topographically
higher Osceola Plain province of the central
Florida peninsula to the Atlantic Ocean, and
spans the eastern peninsula from Jacksonville
southward to southern Palm Beach County.
The Eastern Valley is characteristically flat
and elevationally low, with land surface
elevations varying between 0 and 35 feet
above mean sea level (MSL). Surficial
sediments are predominantly marine terrace
sands and shelly sands, deposited during the
Pleistocene age Pamlico sea level highstand.
Relict beach ridges, paralleling the modem
east coast, are common features throughout
the Eastern Valley.
Bordering the eastern edge of the
Eastern Valley province, between the
Savannas and the Indian River, is a narrow
coast-parallel sand ridge named the Atlantic
Coastal Ridge (White, 1970). This ridge
system extends intermittently along Florida's
east coast from Jacksonville Beach to just
south of Miami. Elevations along that portion
of the ridge near the Savannas Reserve
average about 30 to 35 feet above MSL, and
isolated sand hills on the ridge may attain
elevations of 50 feet above MSL These
higher elevations appear to represent now
quiescent aeolian dunes built up on the ridge
core, and vegetated with bunchgrass, low
shrubs, pine, and palmetto (Bearden, 1972).

:: ~' : I ~P.... .........................t ~




Near the reserve, the ridge varies between
about 1/8 and 1/4 mile wide. A separate,
similar ridge, considered by White (1970) to
be part of the Atlantic Coastal Ridge system,
extends along Hutchinson Island east of the
The Atlantic Coastal Ridge has a
foundation composed of calcareous sandstone
and sandy coquina of the Pleistocene
Anastasia Formation (Bearden, 1972). The
mainland portion of the ridge, and
topographically lower Hutchinson Island, a
barrier island lying across the Indian River to
the east, are believed to be developed on
former offshore bars of the Pamlico
(Pleistocene) sea (Cooke, 1939).
Savannas State Reserve occupies most
of a north-south trending, 13 mile long by 3/4
mile wide marshy swale, situated along the
western side of the Atlantic Coastal Ridge.
The savanna terrain extends from
approximately St.Lucie Inlet northward to Ft.
Pierce. Land elevation within the swale is
approximately 14 feet above MSL.
Historically, the Savannas have been a
freshwater marsh. At one time, the portion of
the Savannas north of the present Reserve
was partitioned with a levee and served as a
main water supply reservoir for the city of Ft.
Pierce (Parker et al., 1955; Bearden, 1972).
Cooke (1939) and MacNeil (1950)
believe that the topographically low, trough-
like area occupied by the Savannas is a
portion of a relict Pleistocene waterway,
analogous to the modem Indian River. The
Atlantic Coastal Ridge may have functioned
as a barrier island during higher sea level in
the late Pleistocene, with a shallow, coast
parallel lagoon behind it to the west. Sand
and silt infilling of this Pleistocene lagoon, in
conjunction with a late Pleistocene sea level
drop, produced the modem Savanna


Savannas State Reserve is underlain by
over 12,000 feet of Mesozoic and Cenozoic
sedimentary rocks, resting on Mesozoic

volcanic basement rock. Most of the younger
overlying rocks are Cretaceous and Cenozoic
age marine carbonates and siliciclastics, which
dip and thicken to the southeast. The
Cenozoic rocks which comprise the upper
3,000 feet of the sediment column are
Paleocene, Eocene and Oligocene carbonates,
which function as primary freshwater aquifers.
These are overlain by Miocene to Recent age
siliclastics. Most water wells penetrate
Eocene and younger sediments. For the
purposes of this summary, the discussion of
the geology underlying Savannas Reserve will
be limited to the Eocene and younger strata.

Eocene Series
Avon Park Formation

The Avon Park Formation (Applin and
Applin, 1944; Miller, 1986) is a cream to tan
colored, highly recrystallized biogenic marine
limestone or dolostone. It generally lies at
depths in excess of 800 feet below land surface
(bls) under St. Lucie and Martin Counties,
and attains a thickness of over 1,000 feet
(Chen, 1965; Wedderbum and Knapp, 1983;
FGS well data). The Avon Park Formation is
unconformably overlain by the Upper Eocene
Ocala Limestone.

Ocala Limestone

The Ocala Limestone (Dall and
Harris, 1892) is an Upper Eocene, white to
pinkish-white colored marine calcarenitic
limestone. Two units within the Ocala are
often recognizable: an upper, more coquinoid
unit comprised of large foraminifera, such as
Nummulites and Lepidocyclina, and other
skeletal fragments in a calcilutite matrix, and
a lower, medium to coarse-grained
biocalcarenitic limestone unit. In St. Lucie
County, the Ocala Limestone generally occurs
at depths of 500 feet or more bls, and is
between 50 and 150 feet thick (Chen, 1965;
Mooney, 1979; Wedderbum and Knapp, 1983;
Armstrong, 1980).
Statewide, the Ocala Limestone is an
important unit of the Florida aquifer system.

It is unconformibly overlain locally by either
an Oligocene age unnamed carbonate unit,
where present, or Miocene Hawthorn Group

Oligocene Series
Unnamed carbonate unit

An unnamed, white, microfossiliferous,
calcilutite unit, dated by microfossils as Late
Oligocene unconformably overlies the Ocala
Limestone in eastern St. Lucie and Martin
Counties (Mooney, 1979; Armstrong, 1980).
Some workers (Lichtler, 1960; Stodghill and
Stewart, 1984) have assigned this unit to the
Suwannee Limestone, while others such as
Wedderbum and Knapp (1983) consider it
equivalent to the Hawthorn Group; its
stratigraphic affinity is uncertain. The top of
the unnamed calcilutite ranges between about
392 and 602 feet bls, with a highly variable
thickness between 0 and 168 feet under St.
Lucie County (Mooney, 1979). Most workers
have included this unit in the Floridan aquifer
system. The unnamed calcilutite is
unconformibly overlain by the Miocene
Hawthorn Group.

Miocene Series
Hawthorn Group

The Miocene Epoch marked the
beginning of a significant change in the
depositional regime of the Floridan Platform.
Sediments deposited prior to Miocene time
were largely pure carbonates. In the early
Miocene, siliciclastic sediments from the
continental mainland to the north were
carried onto the platform and reworked and
deposited by marine and fluvial processes.
The rocks deposited since the beginning of the
Miocene therefore contain a significant
siliciclastic component. This is typified by the
sediments of the Hawthorn Group.
The Hawthorn Group (Scott, 1988) in
St. Lucie County is comprised of two units: a
lower carbonate unit, largely quartz sandy,
phosphatic, limestone and dolostone with
interbedded clays, named the Arcadia
Formation by Scott (1988); and an upper unit

composed of gray to olive gray to white
interbedded clayey, phosphatic, and calcareous
quartz sands, clays, and limestones and
dolostones, named the Peace River Formation
by Scott (1988). In St. Lucie County and
northeastern Martin County, the top of the
Hawthorn Group varies, on average, between
100 and 200 feet bls, and the unit ranges from
300 to 600 feet thick, dipping and thickening
to the southeast (Mooney, 1979; Wedderburn
and Knapp, 1983; Scott, 1988). It is
unconformibly overlain by the Pliocene
Tamiami Formation.

Pliocene Series
Tamiami Formation

The Upper Pliocene Tamiami
Formation (Mansfield, 1939) in the vicinity of
Savannas Reserve consists of a white to
greenish-gray quartz-sandy, very fine grained
biogenic limestone, commonly containing
phosphate sand and fossil shells. It occurs at
a depth of approximately 100 feet bls, and is
about 30 feet thick (Wedderburn and Knapp,
1983). The Tamiami formation is overlain by
the Pleistocene Anastasia formation.

Pleistocene Series

The Pleistocene sediments underlying
eastern St. Lucie and Martin Counties range
from clean quartz sands to shellbeds to sandy
limestones and calcareous sandstones. Some
of the units may be locally discontinuous, and
are often difficult to differentiate
lithologically, particularly in well cuttings.

Caloosahatchee Formation

The Caloosahatchee Formation (Dall
and Harris, 1892) is principally composed of
shelly sands and occasional fossiliferous,
slightly phosphatic, light gray to yellowish-gray
limestones. Due to the difficulty in locally
differentiating Pleistocene units and the sparse
well data, the areas of occurrence, depth, and
thickness of the Caloosahatchee Formation
under St. Lucie County is uncertain. Two
wells in eastern St. Lucie County penetrated

gray limestones thought to be Caloosahatchee
Formation in the depth intervals 63 to 125
feet bls and 60 to 105 feet bls respectively
(FGS unpublished well data). It probably
extends eastward and possibly offshore from
its mapped occurrence in the central
peninsula. It overlies the Tamiami Formation,
and is overlain by the Ft. Thompson
Formation, where present, or by Anastasia
Formation sediments.

Ft. Thompson Formation

In its type area in Lee County, the Ft.
Thompson Formation (Sellards, 1919) consists
of discontinuous, alternating beds of fresh,
brackish, and marine marls and limestones.
This unit probably extends under eastern St.
Lucie County, possibly with sporadic
occurrence. One well, near the Savannas
Reserve in eastern St. Lucie County,
penetrated a gray fossiliferous limestone
between 22 and 65 feet bls which may belong
to the Ft. Thompson Formation. Delineation
of the unit in well cuttings, especially in the
absence of definitive freshwater mollusks, is
difficult. Therefore its extent and depth are

Anastasia Formation

The Upper Pleistocene Anastasia
Formation (Sellards, 1912) varies .from
unconsolidated quartz sand and shell to
calcareous sandstone to a quartz sandy, tan to
orange-colored coquina limestone or mollusk
shell hash. It is perhaps best recognized as
the coquina beach rock which outcrops
sporadically along the east coast from St.
Augustine southward to Boca Raton.
Bearden (1972) believes the Anastasia
Formation may comprise the core of the
Atlantic Coastal Ridge and possibly the
offshore barrier islands.
Near the Savannas Reserve, the
Anastasia Formation is predominantly shelly
sands or calcareous sandstone containing
mollusk shell beds. The depth to the top of
the unit is variable, generally ranging from
between 10 and 20 feet bls in low swales to as

much as 50 feet under dune ridges. It locally
attains a thickness of 50 to 100 feet (FGS
unpublished well data; Wedderburn and
Knapp, 1983). The Anastasia Formation is
overlain by a veneer of Pleistocene and
Holocene sands, clays and silts.

Pleistocene and Holocene Series
Undifferentiated surficial deposits

Surficial deposits in the Savannas State
Reserve are predominantly relict marine
quartz sands, with sandy muds and silts
forming the substrate in the wet, marshy
areas. Much of the sand was deposited and
reworked during sea level highstands of the
late Pleistocene, having been carried south
from the eroding Appalachians by longshore
currents. As sea level retreated, Holocene
fluvial muds and silts accumulated in low-lying
areas, and winds formed the aeolian sand
dunes along the crest of the Atlantic Coastal


Three primary hydrostratigraphic units
are present in the vicinity of the Savannas
Reserve. In order of increasing depth they
are: the surficial aquifer system, the
intermediate aquifer system or intermediate
confining unit, and the Floridan aquifer
system (Southeastern Geological Society Ad
Hoc Committee, 1986).

The surficial aquifer system

The surficial aquifer system occurs
within the porous sands, sandstones, shellbeds,
and limestones of the Tamiami through
Anastasia Formations. This unit contains the
water table, and is generally unconfined.
However, in northeastern St. Lucie County, a
low-permeability, dark gray, sandy, clayey,
marl strata, lying at a depth of about 30 feet
bls, may serve to partially confine the lower
portion of the surficial aquifer system and
form a low pressure artesian system (Parker et
al., 1955). The portion above the confining

strata is primarily white to brown quartz
sands. Below the confining strata are a series
of sands, shell marls, and shell beds. The City
of Ft. Pierce developed a municipal well field
within this system at the northern end of the
Savannas (Parker et al., 1955).
The surficial aquifer system also locally
serves as a source of potable water for
domestic use. Most of wells into the surficial
aquifer system were completed between 15
and 170 feet bls. A typical 2 inch diameter
domestic well may yield 40 gallons per minute
(Bearden, 1972).
The surficial aquifer system varies
from about 100 to 150 feet thick; it is
confined at its base by low-permeability clays
of the Hawthorn Group, part of the
intermediate confining unit (Scott et al.,
1991). Its upper limit is the water table,
which varies with surface topography and
degree of drought. It is close to the surface in
low areas, and probably controls the surface
water levels in many of the pools within the
Savannas. Recharge to the surficial aquifer
system is mostly through local precipitation.

The intermediate aquifer system
intermediate confining unit

Low permeability strata within the
lowermost Tamiami Formation and the upper
Hawthorn Group sediments form the base for
the surficial aquifer system, and also serve to
confine the underlying Floridan aquifer
system. This hydrostratigraphic unit is named
the intermediate aquifer system or
intermediate confining unit (Southeastern
Geological Society Ad Hoc Committee, 1986).
The confining beds are comprised primarily of
phosphatic, clayey, and dolomitic quartz sands
(Wedderburn and Knapp, 1983). Interbedded
within the low-permeability units are thin, well
indurated porous carbonates, which may
contain limited quantities of freshwater. Due
to the thinness and low permeability of these
units, they are generally not considered a
source of water (Wedderburn and Knapp,
1983). Porous carbonates at the base of the
Hawthorn Group may be in hydrologic

continuitywith the underlying Floridan aquifer
The top of the intermediate confining
unit in St. Lucie County lies between about
110 and 160 feet deep, and it reaches a
thickness of over 450 feet (Wedderburn and
Knapp, 1983; Scott et al., 1991). Underlying
the intermediate confining unit are porous
limestones of the Floridan aquifer system.

Floridan aquifer system

Paleocene through Oligocene
carbonates locally comprise the Floridan
aquifer system (Southeastern Geological
Society Ad Hoc Committee, 1986). The
highly porous nature of the rocks comprising
the Floridan aquifer system, with few
interbedded confining units, make it a highly
productive unit. It underlies all of Florida at
varying depths, and extends northward into
parts of Georgia, Alabama, and South
The top of the Floridan aquifer system
occurs under eastern St. Lucie and Martin
Counties at a depth of approximately 700 feet
bls (Scott et al., 1991). Here, it is between
2,700 and 3,000 feet thick (Miller, 1986). It
includes Paleocene and Lower Eocene strata,
as well as the Eocene Avon Park Formation
and Ocala Limestone, and the Oligocene age
unnamed carbonate unit.
The Floridan aquifer system is
confined by overlying low-permeability beds in
the Hawthorn Group, and is under artesian
pressure. Water will rise in tightly cased
Floridan aquifer system wells to a
potentiometric elevation of 35 to 50 feet
above mean sealevel in eastern St. Lucie
County (Bearden, 1972; Barr, 1987). It
therefore supplies most wells through natural
The Floridan aquifer system is not
used as a source of domestic water in the St.
Lucie and Martin County area because of its
local highly mineralized, non-potable nature
(Klein, 1975; Causey and Leve, 1976). Such
mineralized water is used primarily in
commercial cooling and in some industrial and
agricultural applications. A number of

County-owned supply wells drilled to depths
of between 800 and 1,200 have produced
yields of about 200 gallons per minute
(Bearden, 1972).


Applin, P.L., and Applin, E.R., 1944, Regional
subsurface stratigraphy and structure
of Florida and southern Georgia:
American Association of Petroleum
Geologists Bulletin, v. 28, n. 12, p. 16.

Armstrong, J.R., 1980, The geology of the
Floridan aquifer system in eastern
Martin and St. Lucie Counties,
Florida: [thesis], Florida State
University, Tallahassee, 82 p.

Barr, G.L., 1987, Potentiometric surface of the
Upper Floridan aquifer in Florida,
May 1985: Florida Geological Survey
Map Series No. 119.

Bearden, H.W., 1972, Water Availability in
Canals and shallow sediments in St.
Lucie County, Florida: Florida Bureau
of Geology Report of Investigations
No. 62, 50 p.

Causey, L.V., and Leve, G.W., 1976,
Thickness of the potable water
zone in the Floridan Aquifer: Florida
Bureau of Geology Map Series No. 74.

Chen, C.S., 1965, The regional
lithostratigraphic analysis of Paleocene
and Eocene rocks of Florida: Florida
Geological Survey Bulletin No. 45, 105

Cooke, C.W., 1939, Scenery of Florida
interpreted by a geologist: Florida
Geological Survey Bulletin No. 17, 118

Dall, W.H., and Harris, G.D., 1892,
Correlation papers, Neocene:
U.S. Geological Survey Bulletin 84,

349 p.

Klein, H., 1975, Depth to the base of potable
water in the Florida Aquifer: Florida
Bureau of Geology Map Series No. 42.

Lichtler, W.F., 1960, Geology and
groundwater resources of Martin
County, Florida: Florida Geological
Survey Report of Investigations No.
23, 149 p.

MacNeil, F.S., 1950, Pleistocene shorelines in
Florida and Georgia: U.S. Geological
Survey Professional Paper 221-F, p.

Mansfield, W.C., 1939, Notes on the upper
Tertiary and Pleistocene mollusks of
peninsular Florida: Florida Geological
Survey Bulletin 18, 75 p.

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

Mooney, R.T., 1979, The stratigraphy of the
Floridan Aquifer System, east and NE
of Lake Okeechobee, Florida: [thesis]
Florida State University, 61 p.

Parker, G.C., Ferguson, G.E., and Love, S.K.,
1955, Water Resources of
Southeastern Florida, with special
reference to the geology and ground
water of the Miami area: U.S.
Geological Survey Water Supply Paper
1255, 965 p.

Sellards, E.H., 1912, The soils and other
surface residual materials of Florida:
Florida Geological Survey 4th Annual
Report, p. 1-79.

1919, Geologic sections across
the Everglades of Florida: Florida
Geological Survey 12th Annual

Report, p. 67- 76.

Scott, T.M., 1988, The lithostratigraphy of the
Hawthorn Group (Miocene) of
Florida: Florida Geological Survey
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(eds), 1991, 1
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Southeastern Geolo
units of Flor
Survey Specia

Stodghill, A.M., an
Resistivity in,
Ridge Aqu
Martin Coun
Water Manal -
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Wedderburn, L.A.,
Field investil
of storing fre:
of the Flori
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Water Mana;
Publication i

White, W.A., 1970,1
Florida penii
Survey Bulle


Date Due

Due Returned Due Returned
MAR 3 1 2i07199__
APR 27 20 PR 27 ______