The geomorphology, geology and hydrogeology of Baker County, Florida ( FGS: Open file report 33 )

UF00001032.pdf

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








OPEN FILE REPORT 33





THE GEOMORPHOLOGY, GEOLOGY AND HYDROGEOLOGY OF BAKER COUNTY, FLORIDA

By

Paulette Bond


FLORIDA GEOLOGICAL SURVEY
Tallahassee, Florida
1990
"' r'! r' i R F r X,'2A I. "?














































SCREARY
LI3RAR'f









THE GEOMORPHOLOGY, GEOLOGY AND HYDROLOGY OF BAKER COUNTY, FLORIDA

GEOMORPHOLOGY

Baker County lies within the Proximal or Northern Zone of

White (1970). This zone includes the western panhandle of

Florida and extends to the east coast. The southern boundary of

the Proximal Zone extends from the vicinity of Adams Beach in

Taylor County to the boundary between St Johns and Flagler

Counties. Within Baker County two subzones are defined based on

topographic elevations. Most of Baker County is included in the

Northern Highlands subzone, while a small area adjacent to Nassau

and Duval counties falls within the Coastal Lowlands subzone.

Northern Highlands

The Northern Highlands subzone extends across northern

Florida from its western boundary with Alabama east to Trail

Ridge. This province continues north into Alabama and Georgia.

(Figure 1). The Northern Highlands are bounded to the south and

east by the Cody Scarp, a persistent and continuous slope which

is broken only by the valleys of major streams (White, in Puri

and Vernon, 1964). In Baker County the Northern Highlands vary

in elevation from approximately 200 feet above mean sea level

(msl) to approximately 95 feet msl. The province is underlain by

Miocene sand, clay, dolomite and limestone. Miocene deposits are

overlain .by locally thick deposits of quartz sands which contain

variable amounts of clay (Johnson, 1986). Baker County includes

Trail Ridge and the Lake City Ridge, geomorphic subdivisions of

the Northern Highlands (White, in Puri and Vernon, 1964), which







will be discussed separately.


Trail Ridge

White (in Purl and Vernon, 1964) includes Trail Ridge

(Figure 1) as a geomorphic subdivision of the Northern Highlands.

The feature is a linear ridge which is oriented approximately

parallel to the present Atlantic coast line. Trail Ridge is

narrow in Baker County but becomes more broad to the south. It

occurs in southeastern Baker County where Baker is bounded by

Nassau and Duval Counties. Trail Ridge attains topographic

elevations ranging from 100 to 200 feet. The feature is underlain

by quartz sand which contains clay and organic material as well

as heavy minerals (Johnson, 1986). White (1970) proposes that

Trail Ridge originated as a barrier island at a time when sea

level was higher than it is presently.

The Lake City Ridge

The Lake City Ridge is a prominent ridge which is

geographically related to Trail Ridge. Although it is reported

to intersect Trail Ridge (Ceryak et al., 1983), a map of

geomorphologic features (Brooks, 1981) does not show the

intersection. This difference in interpretations is probably

related to differing definitions for the boundaries of the

ridges. Elevations on the Lake City Ridge range from 150 to 215

feet and are similar to those associated with Trail Ridge.

The Atlantic Coastal Lowlands

White (in Purl and Vernon, 1964) described the Atlantic

Coastal Lowlands geomorphic subzone as including the land








adjacent to the Atlantic coast line of Florida. This area is low

in elevation and locally, poorly drained. The geomorphic

features which characterize the Atlantic Coastal Lowlands are

underlain by a mixture of Miocene clay, sand, dolomite and

limestone. The Miocene lithologies are blanketed by variable

amounts of Pleistocene quartz sand and clay ( Knapp, 1978).

Geomorphic features of the Atlantic Coastal Plain are oriented

approximately parallel to the present Atlantic coast line

suggesting that their origin is related to marine processes. The

Atlantic Coastal Lowlands includes a number of geomorphic subdi-

visions. Only one of these subdivisions, the Duval Upland occurs

in Baker County.

Duval Upland

The Duval Upland (White, in Puri and Vernon, 1964), a

geomorphic subdivision of the Atlantic Coastal Plain, occurs in

southeastern Baker County adjacent to the boundary of Baker and

Nassau Counties (Figure 1). It is bounded to the west by Trail

Ridge and is part of a larger coast-parallel landform which

extends eastward into Nassau and Duval Counties. The very small

part of this feature which occurs in Baker County ranges in

elevation from approximately 100 feet to approximately 50 feet

and is characterized by medium to fine sand and clayey sand

(Knapp, 1978).

STRATIGRAPHY

The oldest rocks penetrated by water wells in Baker County

are the limestones of the Eocene age included in the Ocala Group








(Florida Geological Survey in-house well data). The youngest

sediments present are undifferentiated surficial quartz sands and

clayey sands of Pleistocene to Holocene age (Leve, 1968). The

limestone of the Ocala Group and younger overlying limestone and

siliciclastic (sandstone, silt and clay) units (Figures 2 and 3)

are important freshwater aquifers and the following discussion of

the geology of Baker County will be limited to these Eocene and

younger units.

EOCENE SERIES

Ocala Group

Marine limestone of the Ocala Group (Puri, 1957) underlie

all of Baker County (Leve, 1968). The Ocala Group includes three

formations which are listed in ascending order; the Inglis

Formation, the Williston Formation, and the Crystal River

Formation. These formations are generally differentiated based

on lithologic characteristics and fossils. In Baker County,

however, the Inglis, Williston and Crystal River Formations

consist of a fairly homogeneous sequence of cream to light grey,

medium soft chalky to granular, marine limestones which contain

thin beds of hard, massive dolomitic limestone and dolomite

(Leve,1968). Generally the Ocala Group contains abundant

foraminifera, bryozoan fragments and whole and broken echinoid

remains. The thickness of the Ocala Group in the vicinity of

Baker County ranges from approximately 220 to 310 feet and

averages about 250 feet. The upper surface of the Ocala Group

ranges from approximately 200 to 550 feet below the surface of







the ground. The upper surface of the Ocala Group in Baker County

dips to the northeast (Leve, 1968).


OLIGOCENE SERIES

Suwannee Limestone

The Suwannee Limestone lies unconformably above the

limestones of the Ocala Group in the southwestern part of Baker

County (Leve,.1968). It is described as a light grey to white,

granular limestone which contains yellowish brown, indurated

siltstone and calcium carbonate cemented sandstone. The Suwannee

Limestone is less than 30 feet thick in Baker County and occurs

at approximately 180 feet below the surface of the ground. The

unit is absent over much of the county and may not have been

deposited in these areas. Alternatively it may have been removed

by erosion before deposition of the overlying Hawthorn Group

(Leve, 1968).


MIOCENE SERIES

Hawthorn Group

The Hawthorn Group in Baker County unconformably overlies

the Ocala Group limestones or the Suwannee Limestone in Baker

County (Leve, 1968). The Hawthorn Group in north Florida includes

four formations. In ascending order they are the Penney Farms

Formation, the Marks Head Formation, the Coosawhatchie Formation,

and the Statenville Formation (Scott,1988). Locally, in Baker

County the Coosawhatchie Fomation may contain the Charlton Member

(Johnson, 1986; Scott, 1988). In much of Baker County the

Hawthorn Group is not differentiated into its component







formations since cores are required in order for the formations

to be identified and few cores are available. Lithologically,

the undifferentiated Hawthorn Group consists of interbedded

quartz sand, clay and dolostone. The quartz sand varies in color

from yellowish grey to light grey. It is poorly indurated and

contains variable amounts of clay, dolostone and phosphate. The

clay is yellowish grey to light olive grey with sand, dolomite,

and phosphate. It is poorly to moderately indurated. The

dolostone is light grey to olive grey and contains sand, clay and

phosphate. It is poorly to well indurated and contains fossil

molds scattered throughout (Johnson, 1986). The undifferentiated

Hawthorn Group varies in thickness from approximately 125 feet to

about 350 feet (Scott, 1988). The upper surface of the Hawthorn

Group lies from approximately 20 feet below the surface to

approximately 170 feet below the surface. Where core data of good

quality is available, the Hawthorn Group may be differentiated

into its constituent formations (Scott, 1988). In Baker County

the Coosawhatchie Formation has been recognized in a core

(Johnson, 1986). It consists mainly of quartz sand with lesser

amounts of dolomite and limestone. The Coosawhatchie Formation

sometimes contains a recognizable subunit, the Charlton Member.

Where the Charlton Member is described in Baker County it

consists of sandy limestone and calcareous, clayey, quartz sand

with mollusk molds commonly present. The Charlton Member is

restricted in its occurrence to southeastern Baker County where

it lies at the top of the Coosawhatchie Formation and varies in

thickness from less than one foot to about 20 feet. The Charlton







Member occurs at about 160 feet below the surface in Baker County

(Johnson, 1986). The Statenville Formation consists of

interbedded phosphatic sands, dolostones and clays and may extend

into northwestern Baker County (Scott, 1988).


UNDIFFERENTIATED POST-MIOCENE SEDIMENTS

The upper surface of the Hawthorn Group in Baker County is

blanketed by deposits of unconsolidated to poorly consolidated

quartz sand which contains variable amounts of clay. In the area

of the county which lies within the Northern Highlands these

sands vary in thickness from approximately 20 feet to, locally,

100 feet (Florida Geological Survey in-house well data). Sands in

the vicinity of Trail Ridge and the Lake City Ridge are thicker.

In one well from Baker County which completely penetrates the

post-Miocene sequence, a thickness of 162 feet is observed

(Johnson, 1986). The thickness of sands associated with the Duval

Upland in Baker County cannot be documented since well coverage

is not available for that area. Sand from the Northern Highlands

is fine-to-medium-grained and contains only trace amounts of

heavy minerals (Johnson, 1986). In contrast, sand from the Trail

Ridge area is characteristically fine-to-coarse-grained with

common heavy minerals and organic matter. In sand of the

Northern Highlands, clay occurs mixed with sand, while at Trail

Ridge clay occurs both mixed with sand or in discreet scattered

clay beds (Johnson, 1986).


HYDROGEOLOGY

Ground water fills the pore spaces and voids within






subsurface rocks and sediments. In Baker County most of this

water comes from local rainfall and downward seepage of water

from surface streams and marshes. Ground water withdrawn from

Baker County may come from either of three aquifer systems

including the surficial aquifer system, the intermediate aquifer

system and the Floridan aquifer system (Southeastern Geological

Society Ad Hoc Committee on Florida Hydrostratigraphic Unit

Definition, 1986; Leve, 1968).


Surficial Aquifer System

The surficial aquifer system (Southeastern Geological

Society Ad Hoc Committee, 1986) of Baker County includes upper

Miocene sediments of the Hawthorn Group in addition to post-

Miocene sediments which are not differentiated in this report.

Although these sediments range in thickness from approximately

30 to 150 feet, the permeable beds of the aquifer occur generally

within the uppermost 50 feet of these deposits (Leve, 1968).

These permeable sand and shell beds are not continuous and tend

to form lenses which are bounded by less permeable silty clay

beds. The surficial aquifer system is recharged mainly by local

rainfall and downward seepage from surface streams and marshes.

Water leaves the aquifer or, is discharged by evapotranspiration

and seepage into streams, lakes, and swamps when their water

levels are lower than the water level in the aquifer (Leve,

1968). In addition discharge occurs by downward movement or

perolation into deeper aquifers and pumpage by wells in the

county. Water from the surficial aquifer system may be high in

iron causing it to taste bad and stain plumbing fixtures. It is








used locally for rural domestic, stock and irrigation since it is

relatively inexpensive to acquire (Leve, 1968).

Intermediate Aquifer System

The intermediate aquifer system (Southeastern Geological

Society Ad Hoc Committee, 1986). of Baker County consists of

comparatively thin, discontinuous lenses of sand, shell, and

carbonate. These permeable lenses occur within the relatively

impermeable beds of clay and clayey sand within the Hawthorn

Group. The impermeable beds are referred to as the intermediate

confining unit (Southeastern Geological Society Ad Hoc Committee,

1986). Clay beds and beds of clayey sand may serve to restrict

the vertical movement of water so that water may exist under

artesian pressure within some permeable layers (Leve, 1968). The

occurrence of these permeable lenses is variable in Baker county

and their location cannot be predicted. The aquifer system is

recharged by downward movement of water from the shallow aquifer

system. Wells which penetrate the intermediate aquifer system

generally yield more water with a lower iron content than wells

penetrating the shallow system. Water from the intermediate

aquifer system is used for domestic, stock, and irrigation

supplies (Leve, 1968).

Floridan Aquifer System

The Floridan aquifer system is the main water supply source

in northeastern Florida and southeastern Georgia. In Baker

County the Floridan aquifer system consists mainly of permeable

limestone and dolomite units which are Eocene in age. In








restricted areas of the county the Suwannee Limestone of Late

Oligocene age and limestone beds of the Hawthorn Group of Miocene

age may be part of the Floridan aquifer system (Leve, 1968). The

Floridan aquifer system underlies all of Baker County and its

upper surface ranges from approximately 50 feet below mean sea

level in western Baker to more than 350 feet in the eastern part.

The thickness of the Floridan aquifer system is not known in

Baker County, although it is known to be more than 1600 feet

thick in southwestern Baker and approximately 1900 feet thick in

the northeastern part (Leve, 1968). The relatively impermeable

sediments of the Hawthorn Group serve to confine the Floridan.

aquifer system in Baker County. The aquifer system is recharged

primarily in areas where the intermediate confining unit is thin

or breached by streams or sinkholes. In these areas water may

move downward into the aquifer system. Water from the Floridan

aquifer system is discharged by upward seepage and also from

wells (Leve, 1968).


MINERAL RESOURCES

Currently, no mineral resources are being mined commercially

in Baker County (Campbell, 1986; Spencer, 1989). Clayey sands of

post-Miocene age have some potential for use as fill material.

Limestone is deeply buried by post-Miocene clayey sands and also

by the siliciclastics and discontinuous dolostones and limestones

of Miocene age. The occurrence of peat deposits is suggested by

extensive wetland areas in northern Baker County, but no data is

currently available to document their occurrence (Bond et al.,







1986). Although neither phosphate nor heavy minerals are mined

in Baker County at present they will be discussed briefly since

future development of those resources is possible.

Phosphate

Baker County lies within the Northern and Northeast Florida

Phosphate Districts (Campbell, 1986). Scott (1988) notes that

phosphate production in north Florida is from the Statenville

Formation of the Hawthorn Group and is restricted to eastern

Hamilton County (Northern District). This formation may occur in

a very limited area of northwestern Baker County. Eastern Baker

County lies within the Northeast District where phosphate occurs

at approximately 200 feet below land surface (Scott, 1988).

Currently phosphate is not mined in Baker County. This is

probably due to economic factors related to the thickness of

overburden as well as the relative enrichment of phosphate within

the rock units which contain it. As alternate phosphate

resources dwindle and technology improves, commercial

exploitation of this resource might become a future option. The

United States Geological Survey evaluated impacts associated with

potential phosphate mining on the hydrology of the Osceola

National Forest in a study conducted in 1978 (Miller, et al.,

1978).


Heavy Minerals

Trail Ridge is a linear ridge with a north-northwesterly

orientation which occurs in eastern Baker County. It is also

discussed here under the heading "Geomorphology". At the







southern end of Trail Ridge (located in Bradford and Clay

counties) the ore body is mined commercially for heavy minerals.

A core drilled on Trail Ridge in Baker County (Pirkle, et al.,

1977) was found to have an ore zone approximately 35 feet thick.

Heavy minerals from the ore zone include leucoxene and ilmenite.

They occur intermixed with quartz sand, silt, clay, and organic

matter (Pirkle, et al., 1977). Although heavy minerals are not

mined currently in Baker County future development may be a

possibility.

REFERENCES

Bond, P.A., Campbell, K.M., and Scott, T.M., 1986, An overview of
peat in Florida and related issues: Florida Geological
Survey Special Publication no. 27, 151 p.

Brooks, H.K., 1981, Physiographic Divisions of the State of
Florida: Florida Cooperative Extension Services, Institute
for Food and Agricultural Sciences, University of Florida,
Gainesville, 1 p.Campbell, K.M.., 1986, The industrial
minerals of Florida: Florida Geological Survey Information
Circular no. 102, 94 p.

Ceryak, R., Knapp, M.S., and Burnson, T., 1983, The Geology and
Water Resources of the Upper Suwannee River Basin, Florida,
Florida Geological Survey Report of Investigation no. 87,
165 p.

Johnson, R.A., 1986, Shallow stratigraphic core tests on file at
the Florida Geological Survey: Florida Geological Survey
Information Circular no. 103, 431 p.

Knapp, M.S., 1978, Environmental geology series Valdosta sheet:
Florida Bureau of Geology Map Series no. 88, 1 p.

Leve, G.W., 1968, Reconnaissance of the ground-water resources of
Baker County, Florida: Florida Division of Geology Report
of Investigations no. 52, 24 p.

Miller, J.A., Gilbert, H.H., Hull, R.W., Vecchioli, J., and
Seaber, P.R., 1978, Impact of potential phosphate mining on
the hydrology of Osceola National Forest, Florida: U.S.
Geological Survey Water-Resources Investigations 78-6, 159
p.







Pirkle, E.C., Pirkle, W.A., and Yoho, W.H., 1977, The Highland
heavy-mineral sand deposit on Trail Ridge in northern
peninsular Florida: Florida Bureau of Geology Report of
Investigation no. 84, 50 p.

Puri, H.S., 1957, Stratigraphy and zonation of the Ocala Group:
Florida Geological Survey Bulletin no. 38, 248 p.

Puri, H.S. 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, 312 p.

Scott, T.M., 1988, The lithostratigraphy of the Hawthorn Group
(Miocene) of Florida: Florida Geological Survey Bulletin no.
59, 148 p.

Southeastern Geological Society Ad Hoc Committee, 1986,
Hydrogeological units of Florida: Florida Geological Survey
Special Publication no. 28, 8 p.

Spencer, S.M., 1989, The industrial minerals industry directory
of Florida: Florida Geological Survey Information Circular
no. 105, Part I, 51 p.

White, W.A., 1970, The geomorphology of the Florida peninsula:
Florida Bureau of Geology Geological Bulletin no. 51, 164 p.










A A'
West East

n W-4056 W-6502
W-4547
I W-4532
SOlustee UNDIFFERENTIATED W-4599
60 200 Crooeek SANDS AND CLAYS South

30-- 100

MSL MSL
0- 0
HAWTHORN GROUP
-30 -100

-60---200 TD 270

-90 ---300 OCALA GROUP --
TD 340' TD 350'
-120- -400
5 0 MILES TD 825 TD 610'

5 0 KILOMETERS
SCALE











B
North


@to

60-- 200

30-- 100


0 -- 0


MSL


-30- -100

-60- -200

-90 -300

-120- --400


W-13805


UNDIFFERENTIATED \
SANDS AND CLAYS




TD
?OCALA GROUP
OCALA GROUP


W-13812 W-4056


TD 182'
HAWTHORN GROUP


TD 3349'


5 0 MILES

5 0 KILOMETERS
SCALE


B'
South


MSL


TD 340'


TD 3043'











GEORGIA
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NORTHERN. .
HIGHLANDS.... -



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PAGE 1

STATE OF FLORfDA DEPARTMENT OF NATURAL RESOURCES Tom Gardner, Executive Director DIVISION OF RESOURCE MANAGEMENT Jeremy A. Craft, Director FLORIDA GEOLOGICAL SURVEY Walter Schmidt, State Geologist OPEN FILE REPORT 33 THE GEOMORPHOLOGY, GEOLOGY AND HYDROGEOLOGY OF BAKER COUNTY, FLORIDA By Paulette Bond FLORIDA GEOLOGICAL SURVEY Tallahassee, Florida 1990 ,"' r 'Ir'/Ti RF Fr ,, ' .7~ " 'I

PAGE 2

SCREARY LI3RAR'f

PAGE 3

THE GEOMORPHOLOGY, GEOLOGY AND HYDROLOGY OF BAKER COUNTY, FLORIDA GEOMORPHOLOGY Baker County lies within the Proximal or Northern Zone of White (1970). This zone includes the western panhandle of Florida and extends to the east coast. The southern boundary of the Proximal Zone extends from the vicinity of Adams Beach in Taylor County to the boundary between St Johns and Flagler Counties. Within Baker County two subzones are defined based on topographic elevations. Most of Baker County is included in the Northern Highlands subzone, while a small area adjacent to Nassau and Duval counties falls within the Coastal Lowlands subzone. Northern Highlands The Northern Highlands subzone extends across northern Florida from its western boundary with Alabama east to Trail Ridge. This province continues north into Alabama and Georgia. (Figure 1). The Northern Highlands are bounded to the south and east by the Cody Scarp, a persistent and continuous slope which is broken only by the valleys of major streams (White, in Puri and Vernon, 1964). In Baker County the Northern Highlands vary in elevation from approximately 200 feet above mean sea level (msl) to approximately 95 feet msl. The province is underlain by Miocene sand, clay, dolomite and limestone. Miocene deposits are overlain .by locally thick deposits of quartz sands which contain variable amounts of clay (Johnson, 1986). Baker County includes Trail Ridge and the Lake City Ridge, geomorphic subdivisions of the Northern Highlands (White, in Puri and Vernon, 1964), which 1.

PAGE 4

will be discussed separately. Trail Ridge White (in Purl and Vernon, 1964) includes Trail Ridge (Figure 1) as a geomorphic subdivision of the Northern Highlands. The feature is a linear ridge which is oriented approximately parallel to the present Atlantic coast line. Trail Ridge is narrow in Baker County but becomes more broad to the south. It occurs in southeastern Baker County where Baker is bounded by Nassau and Duval Counties. Trail Ridge attains topographic elevations ranging from 100 to 200 feet. The feature is underlain by quartz sand which contains clay and organic material as well as heavy minerals (Johnson, 1986). White (1970) proposes that Trail Ridge originated as a barrier island at a time when sea level was higher than it is presently. The Lake City Ridge The Lake City Ridge is a prominent ridge which is geographically related to Trail Ridge. Although it is reported to intersect Trail Ridge (Ceryak et al., 1983), a map of geomorphologic features (Brooks, 1981) does not show the intersection. This difference in interpretations is probably related to differing definitions for the boundaries of the ridges. Elevations on the Lake City Ridge range from 150 to 215 feet and are similar to those associated with Trail Ridge. The Atlantic Coastal Lowlands White (in Purl and Vernon, 1964) described the Atlantic Coastal Lowlands geomorphic subzone as including the land

PAGE 5

adjacent to the Atlantic coast line of Florida. This area is low in elevation and locally, poorly drained. The geomorphic features which characterize the Atlantic Coastal Lowlands are underlain by a mixture of Miocene clay, sand, dolomite and limestone. The Miocene lithologies are blanketed by variable amounts of Pleistocene quartz sand and clay ( Knapp, 1978). Geomorphic features of the Atlantic Coastal Plain are oriented approximately parallel to the present Atlantic coast line suggesting that their origin is related to marine processes. The Atlantic Coastal Lowlands includes a number of geomorphic subdivisions. Only one of these subdivisions, the Duval Upland occurs in Baker County. Duval Upland The Duval Upland (White, in Puri and Vernon, 1964), a geomorphic subdivision of the Atlantic Coastal Plain, occurs in southeastern Baker County adjacent to the boundary of Baker and Nassau Counties (Figure 1). It is bounded to the west by Trail Ridge and is part of a larger coast-parallel landform which extends eastward into Nassau and Duval Counties. The very small part of this feature which occurs in Baker County ranges in elevation from approximately 100 feet to approximately 50 feet and is characterized by medium to fine sand and clayey sand (Knapp, 1978). STRATIGRAPHY The oldest rocks penetrated by water wells in Baker County are the limestones of the Eocene age included in the Ocala Group 3.

PAGE 6

(Florida Geological Survey in-house well data). The youngest sediments present are undifferentiated surficial quartz sands and clayey sands of Pleistocene to Holocene age (Leve, 1968). The limestones of the Ocala Group and younger overlying limestone and siliciclastic (sandstone, silt and clay) units (Figures 2 and 3) are important freshwater aquifers and the following discussion of the geology of Baker County will be limited to these Eocene and younger units. EOCENE SERIES Ocala Group Marine limestones of the Ocala Group (Puri, 1957) underlie all of Baker County (Leve, 1968). The Ocala Group includes three formations which are listed in ascending order; the Inglis Formation, the Williston Formation, and the Crystal River Formation. These formations are generally differentiated based on lithologic characteristics and fossils. In Baker County, however, the Inglis, Williston and Crystal River Formations consist of a fairly homogeneous sequence of cream to light grey, medium soft chalky to granular, marine limestones which contain thin beds of hard, massive dolomitic limestone and dolomite (Leve,1968). Generally the Ocala Group contains abundant foraminifera, bryozoan fragments and whole and broken echinoid remains. The thickness of the Ocala Group in the vicinity of Baker County ranges from approximately 220 to 310 feet and averages about 250 feet. The upper surface of the Ocala Group ranges from approximately 200 to 550 feet below the surface of

PAGE 7

the ground. The upper surface of the Ocala Group in Baker County dips to the northeast (Leve, 1968). OLIGOCENE SERIES Suwannee Limestone The Suwannee Limestone lies unconformably above the limestones of the Ocala Group in the southwestern part of Baker County (Leve,.1968). It is described as a light grey to white, granular limestone which contains yellowish brown, indurated siltstone and calcium carbonate cemented sandstone. The Suwannee Limestone is less than 30 feet thick in Baker County and occurs at approximately 180 feet below the surface of the ground. The unit is absent over much of the county and may not have been deposited in these areas. Alternatively it may have been removed by erosion before deposition of the overlying Hawthorn Group (Leve, 1968). MIOCENE SERIES Hawthorn Group The Hawthorn Group in Baker County unconformably overlies the Ocala Group limestones or the Suwannee Limestone in Baker County (Leve, 1968). The Hawthorn Group in north Florida includes four formations. In ascending order they are the Penney Farms Formation, the Marks Head Formation, the Coosawhatchie Formation, and the Statenville Formation (Scott,1988). Locally, in Baker County the Coosawhatchie Fomation may contain the Charlton Member (Johnson, 1986; Scott, 1988). In much of Baker County the Hawthorn Group is not differentiated into its component 5.

PAGE 8

formations since cores are required in order for the formations to be identified and few cores are available. Lithologically, the undifferentiated Hawthorn Group consists of interbedded quartz sand, clay and dolostone. The quartz sand varies in color from yellowish grey to light grey. It is poorly indurated and contains variable amounts of clay, dolostone and phosphate. The clay is yellowish grey to light olive grey with sand, dolomite, and phosphate. It is poorly to moderately indurated. The dolostone is light grey to olive grey and contains sand, clay and phosphate. It is poorly to well indurated and contains fossil molds scattered throughout (Johnson, 1986). The undifferentiated Hawthorn Group varies in thickness from approximately 125 feet to about 350 feet (Scott, 1988). The upper surface of the Hawthorn Group lies from approximately 20 feet below the surface to approximately 170 feet below the surface. Where core data of good quality is available, the Hawthorn Group may be differentiated into its constituent formations (Scott, 1988). In Baker County the Coosawhatchie Formation has been recognized in a core (Johnson, 1986). It consists mainly of quartz sand with lesser amounts of dolomite and limestone. The Coosawhatchie Formation sometimes contains a recognizable subunit, the Charlton Member. Where the Charlton Member is described in Baker County it consists of sandy limestone and calcareous, clayey, quartz sand with mollusk molds commonly present. The Charlton Member is restricted in its occurrence to southeastern Baker County where it lies at the top of the Coosawhatchie Formation and varies in thickness from less than one foot to about 20 feet. The Charlton

PAGE 9

Member occurs at about 160 feet below the surface in Baker County (Johnson, 1986). The Statenville Formation consists of interbedded phosphatic sands, dolostones and clays and may extend into northwestern Baker County (Scott, 1988). UNDIFFERENTIATED POST-MIOCENE SEDIMENTS The upper surface of the Hawthorn Group in Baker County is blanketed by deposits of unconsolidated to poorly consolidated quartz sand which contains variable amounts of clay. In the area of the county which lies within the Northern Highlands these sands vary in thickness from approximately 20 feet to, locally, 100 feet (Florida Geological Survey in-house well data). Sands in the vicinity of Trail Ridge and the Lake City Ridge are thicker. In one well from Baker County which completely penetrates the post-Miocene sequence, a thickness of 162 feet is observed (Johnson, 1986). The thickness of sands associated with the Duval Upland in Baker County cannot be documented since well coverage is not available for that area. Sand from the Northern Highlands is fine-to-medium-grained and contains only trace amounts of heavy minerals (Johnson, 1986). In contrast, sand from the Trail Ridge area is characteristically fine-to-coarse-grained with common heavy minerals and organic matter. In sand of the Northern Highlands, clay occurs mixed with sand, while at Trail Ridge clay occurs both mixed with sand or in discreet scattered clay beds (Johnson, 1986). HYDROGEOLOGY Ground water fills the pore spaces and voids within

PAGE 10

subsurface rocks and sediments. In Baker County most of this water comes from local rainfall and downward seepage of water from surface streams and marshes. Ground water withdrawn from Baker County may come from either of three aquifer systems including the surficial aquifer system, the intermediate aquifer system and the Floridan aquifer system (Southeastern Geological Society Ad Hoc Committee on Florida Hydrostratigraphic Unit Definition, 1986; Leve, 1968). Surficial Aquifer System The surficial aquifer system (Southeastern Geological Society Ad Hoc Committee, 1986) of Baker County includes upper Miocene sediments of the Hawthorn Group in addition to postMiocene sediments which are not differentiated in this report. Although these sediments range in thickness from approximately 30 to 150 feet, the permeable beds of the aquifer occur generally within the uppermost 50 feet of these deposits (Leve, 1968). These permeable sand and shell beds are not continuous and tend to form lenses which are bounded by less permeable silty clay beds. The surficial aquifer system is recharged mainly by local rainfall and downward seepage from surface streams and marshes. Water leaves the aquifer or, is discharged by evapotranspiration and seepage into streams, lakes, and swamps when their water levels are lower than the water level in the aquifer (Leve, 1968). In addition discharge occurs by downward movement or perolation into deeper aquifers and pumpage by wells in the county. Water from the surficial aquifer system may be high in iron causing it to taste bad and stain plumbing fixtures. It is

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used locally for rural domestic, stock and irrigation since it is relatively inexpensive to acquire (Leve, 1968). Intermediate Aquifer System The intermediate aquifer system (Southeastern Geological Society Ad Hoc Committee, 1986). of Baker County consists of comparatively thin, discontinuous lenses of sand, shell, and carbonate. These permeable lenses occur within the relatively impermeable beds of clay and clayey sand within the Hawthorn Group. The impermeable beds are referred to as the intermediate confining unit (Southeastern Geological Society Ad Hoc Committee, 1986). Clay beds and beds of clayey sand may serve to restrict the vertical movement of water so that water may exist under artesian pressure within some permeable layers (Leve, 1968). The occurence of these permeable lenses is variable in Baker county and their location cannot be predicted. The aquifer system is recharged by downward movement of water from the shallow aquifer system. Wells which penetrate the intermediate aquifer system generally yield more water with a lower iron content than wells penetrating the shallow system. Water from the intermediate aquifer system is used for domestic, stock, and irrigation supplies (Leve, 1968). Floridan Aquifer System The Floridan aquifer system is the main water supply source in northeastern Florida and southeastern Georgia. In Baker County the Floridan aquifer system consists mainly of permeable limestone and dolomite units which are Eocene in age. In

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restricted areas of the county the Suwannee Limestone of Late Oligocene age and limestone beds of the Hawthorn Group of Miocene age may be part of the Floridan aquifer system (Leve, 1968). The Floridan aquifer system underlies all of Baker County and its upper surface ranges from approximately 50 feet below mean sea level in western Baker to more than 350 feet in the eastern part. The thickness of the Floridan aquifer system is not known in Baker County, although it is known to be more than 1600 feet thick in southwestern Baker and approximately 1900 feet thick in the northeastern part (Leve, 1968). The relatively impermeable sediments of the Hawthorn Group serve to confine the Floridan. aquifer system in Baker County. The aquifer system is recharged primarily in areas where the intermediate confining unit is thin or breached by streams or sinkholes. In these areas water may move downward into the aquifer system. Water from the Floridan aquifer system is discharged by upward seepage and also from wells (Leve, 1968). MINERAL RESOURCES Currently, no mineral resources are being mined commercially in Baker County (Campbell, 1986; Spencer, 1989). Clayey sands of post-Miocene age have some potential for use as fill material. Limestone is deeply buried by post-Miocene clayey sands and also by the siliciclastics and discontinuous dolostones and limestones of Miocene age. The occurrence of peat deposits is suggested by extensive wetland areas in northern Baker County, but no data is currently available to document their occurrence (Bond et al.,

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1986). Although neither phosphate nor heavy minerals are mined in Baker County at present they will be discussed briefly since future development of those resources is possible. Phosphate Baker County lies within the Northern and Northeast Florida Phosphate Districts (Campbell, 1986). Scott (1988) notes that phosphate production in north Florida is from the Statenville Formation of the Hawthorn Group and is restricted to eastern Hamilton County (Northern District). This formation may occur in a very limited area of northwestern Baker County. Eastern Baker County lies within the Northeast District where phosphate occurs at approximately 200 feet below land surface (Scott, 1988). Currently phosphate is not mined in Baker County. This is probably due to economic factors related to the thickness of overburden as well as the relative enrichment of phosphate within the rock units which contain it. As alternate phosphate resources dwindle and technology improves, commercial exploitation of this resource might become a future option. The United States Geological Survey evaluated impacts associated with potential phosphate mining on the hydrology of the Osceola National Forest in a study conducted in 1978 (Miller, et al., 1978). Heavy Minerals Trail Ridge is a linear ridge with a north-northwesterly orientation which occurs in eastern Baker County. It is also discussed here under the heading "Geomorphology". At the

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southern end of Trail Ridge (located in Bradford and Clay counties) the ore body is mined commercially for heavy minerals. A core drilled on Trail Ridge in Baker County (Pirkle, et al., 1977) was found to have an ore zone approximately 35 feet thick. Heavy minerals from the ore zone include leucoxene and ilmenite. They occur intermixed with quartz sand, silt, clay, and organic matter (Pirkle, et al., 1977). Although heavy minerals are not mined currently in Baker County future development may be a possibility. REFERENCES Bond, P.A., Campbell, K.M., and Scott, T.M., 1986, An overview of peat in Florida and related issues: Florida Geological Survey Special Publication no. 27, 151 p. Brooks, H.K., 1981, Physiographic Divisions of the State of Florida: Florida Cooperative Extension Services, Institute for Food and Agricultural Sciences, University of Florida, Gainesville, 1 p.Campbell, K.M.., 1986, The industrial minerals of Florida: Florida Geological Survey Information Circular no. 102, 94 p. Ceryak, R., Knapp, M.S., and Burnson, T., 1983, The Geology and Water Resources of the Upper Suwannee River Basin, Florida, Florida Geological Survey Report of Investigation no. 87, 165 p. Johnson, R.A., 1986, Shallow stratigraphic core tests on file at the Florida Geological Survey: Florida Geological Survey Information Circular no. 103, 431 p. Knapp, M.S., 1978, Environmental geology series Valdosta sheet: Florida Bureau of Geology Map Series no. 88, 1 p. Leve, G.W., 1968, Reconnaissance of the ground-water resources of Baker County, Florida: Florida Division of Geology Report of Investigations no. 52, 24 p. Miller, J.A., Gilbert, H.H., Hull, R.W., Vecchioli, J., and Seaber, P.R., 1978, Impact of potential phosphate mining on the hydrology of Osceola National Forest, Florida: U.S. Geological Survey Water-Resources Investigations 78-6, 159 p.

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Pirkle, E.C., Pirkle, W.A., and Yoho, W.H., 1977, The Highland heavy-mineral sand deposit on Trail Ridge in northern peninsular Florida: Florida Bureau of Geology Report of Investigation no. 84, 50 p. Puri, H.S., 1957, Stratigraphy and zonation of the Ocala Group: Florida Geological Survey Bulletin no. 38, 248 p. Puri, H.S. 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, 312 p. Scott, T.M., 1988, The lithostratigraphy of the Hawthorn Group (Miocene) of Florida: Florida Geological Survey Bulletin no. 59, 148 p. Southeastern Geological Society Ad Hoc Committee, 1986, Hydrogeological units of Florida: Florida Geological Survey Special Publication no. 28, 8 p. Spencer, S.M., 1989, The industrial minerals industry directory of Florida: Florida Geological Survey Information Circular no. 105, Part I, 51 p. White, W.A., 1970, The geomorphology of the Florida peninsula: Florida Bureau of Geology Geological Bulletin no. 51, 164 p.

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A A' West East SW-4056 W-6502 SW-454 W-4532 SOlustee UNDIFFERENTIATED W-4599 60 200 Creek SANDS AND CLAYS Prong 30-100 MSL _MSL 0-0 HAWTHORN GROUP -30 --100 -60---200 TD 270' -90-300 -90---300 OCALA GROUP -TD 340' TD 350' -120 --400 3 TD 825' " 5 0 MILES T 825 TD 610' 5 0 KILOMETERS SCALE r.C

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B B' North South -1500 W-13805 W-13812 W-4056 W-2187 S" C Olustee 60-200 Rudy mp Ocean Creek -UNNAMED Branch/;7 Branch Pond 30-100 UNDIFFERENTIATED MSL SANDS AND CLAYS __MSL 0 00 TD 182' -30 --100 HAWTHORN GROUP TD 272' -60o-200 TD 40' OCALA GROUP -90-300 -9---300 TD 3043' TD 3349' -120--400 5 0 MILES 5 0 KILOMETERS SCALE

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GEORGIA ** -N.NORTHERN. . O ............. ..... ....... .. .. SHIGHLA N DS :.:.::::::.......G ....... I ................ 0 .5 M ILES ....... .. .................SCA LE .... ....*** ....* i **............. .. .< .W -13812. ..'.'.'.'.'.' .' ' W -'1'' '.'.'.. 0 8 KILOMETERS C ..'. .... .............. .1 ...*., V .* *W'.'. 0* S:::::::::::::::D::::::::::: DUVAL ......... ....5.. .............. U P LA N D S ii! ::::::: ::: :::::::::::::::::::::::::: : P LA N .Iw138 12 .... .... .... ... ......... .... ' ....... ... ...... .....v. ...... 0 ..... ........• , • • , I • • • • • ° • 8 ^ -i , , 47' ^ .................. ..."""""".-::.-. SW-217 ............... .. .... S.... N CO. BRADFORD C. .E B ' * * * ..... ............. * * * ... .. ........ UNION CO. BRADFORD CO.

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