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MAP SERIES NO. 134
MINERAL RESOURCES OF UNION AND BRADFORD
Ed Lane, P.G. #141, Ronald W. Hoenstine, Frank R. Rupert
and Steven M. Spencer
FLORIDA GEOLOGICAL SURVEY
WALTER SCHMIDT, STATE GEOLOGIST AND CHIEF
DIVISION OF RESOURCE MANAGEMENT
DEPARTMENT OF NATURAL RESOURCES
UNION AND BRADFORD COUNTIES
In recent years, considerable attention has been focused on Florida's
rapid development, accompanying population increase and their effect on
the state's important mineral resources. Frequently, urban development
has occurred in areas underlain by known mineral deposits, precluding
future extraction of the minerals. The economics associated with these
mineral resources represent substantial employment and income to the
private sector as well as revenue to county and state governments. One
response to this growing conflict between rapid growth and development
of the state's mineral resources was in the form of legislation enacted by
the Florida Legislature in 1985 requiring each county to establish a
comprehensive land use plan. Additional guidelines and due dates were
established by the 1986 Florida Legislature.
In response to this act and at the request of the North Central Florida
Regional Planning Council, the Florida Geological Survey initiated a study
of Union and Bradford Counties' mineral resources. The objective of this
report is to summarize and interpret geologic data (i.e., core and well
cutting descriptions and geophysical logs, and data derived from field
reconnaissance) in a format appropriate for use by city and county
A knowledge of an area's mineral resources is basic and integral to
the process of initiating, developing and implementing an effective
comprehensive land use plan. The information and data are essential
to planners and officials in their analysis of urban and rural
development in matters of zoning, road construction and the
establishment of waste disposal sites.
Factors used in evaluating the economic value of the counties' known
and potential mineral resources are varied, changing, and in many
instances interrelated, thus complicating an accurate assessment. This
evaluation process is inherently dependent on an extensive exploration
program, which is a necessary precursor to mining in order to determine
reserves, content and extent of specific mineral resources. In addition,
such factors as operating expenses, beneficiation, transportation,
reclamation and capital costs of mining must be included in the overall
Resource evaluation for this report is based on a number of sources,
including Florida Geological Survey reports and unpublished data, field
reconnaissance, state and federal statistical data, and numerous
discussions with state and federal officials. The diversity of sources as
well as their close association with the various aspects of resource
evaluation lends substantial confidence to the general assessments and
inferences of this report.
METRIC CONVERSION FACTORS
In order to prevent duplication of English and metric units in this report,
the following conversion factors are provided:
Situated in north-central Florida, Union and Bradford Counties fall
entirely within the Northern (Proximal) Zone of White (1970). This zone
encompasses all of the Florida panhandle and the northern Florida
peninsula southward to an approximate line connecting the cities of St.
Augustine, Palatka, Gainesville and Perry.
Within the Northern Zone the major geomorphic feature is the Northern
Highlands. This prominent feature, which covers all of Union and
Bradford Counties (Figure 1), extends across the northern part of Florida
from the Trail Ridge on the east to the state's western boundary (White,
1970; Puri and Vernon, 1964). Elevations within the study area range from
less than 50 feet above mean sea level (MSL) along the Santa Fe River in
the south to over 200 feet on parts of Trail Ridge in northeast Bradford
County (Figures 1 and 2).
Union County has a diversity of surface features, including numerous
hills, valleys, broad low areas, streams, and rivers. Navigable waters
include Olustee Creek and the Santa Fe River, forming the western and
southern county boundaries, and New River which forms the Union-
Bradford County boundary. In the general area of Worthington Springs,
distinctive bluffs more than 50-feet high border the Santa Fe River's flood
Trail Ridge is a major feature situated in the eastern part of Bradford
County (Figure 1). Trail Ridge has been thought to be a beach-complex
deposit, however, a more recent study by Force and Garnar (1985)
suggests a sand-dune origin. Relatively rapid increases in elevation occur
as one goes onto the ridge from west-to-east, from approximately 170 feet
at the toe of the ridge to over 215 feet along the eastern Bradford County
line (Figure 2). Maximum ridge elevations occur in neighboring Clay
County east of Lawtey, where the ridge crests at slightly over 220 feet
The counties have a number of relatively shallow lakes, the largest of
which are shown on Figures 1 and 2. Typically, these lakes have low,
swampy shorelines with sand or mud bottoms; all have outflow channels
which are tributaries to Olustee Creek, the New River, or the Santa Fe
River (Clark et al., 1964).
Pleistocene sea level fluctuations have significantly influenced the
surface topography of Union and Bradford Counties. These ancient sea
level high stands formed step-like terraces. Healy (1975) recognized four
terraces based on elevation as being present in Union and Bradford
Counties (Figure 2). They are, from oldest to youngest (and highest to
lowest), the Hazlehurst Terrace (215 320 feet above MSL), the Coharie
Terrace (170 215 feet above MSL), the Sunderland/Okefenokee Terrace
(100 170 feet above MSL) and the Wicomico Terrace (70 100 feet
The study area is underlain by Paleozoic basement rocks at depths of
approximately 3,000 feet below land surface (2,800 feet below MSL). To
date, the deepest penetration of sediments in Union County occurred in
an oil test well, W-11912 (section 31, Township 4S, Range 19E), drilled in
1973 to a depth of 2,917 feet below MSL. Fifteen feet of Paleozoic
basement rocks were first encountered at a depth of 2,902 feet below
MSL (Barnett, 1975; Lloyd, 1985). The deepest well drilled in Bradford
County is oil test well W-1466 (section 15, Township 6S, Range 20E),
drilled in 1947 to 3,035 feet below MSL. At a depth of 3,008 feet below
MSL this well then penetrated 27 feet of Paleozoic basement rocks,
composed of quartzitic sandstone and shale (Lloyd, 1985). These
basement rocks are overlain by thousands of feet of Mesozoic and
Cenozoic age carbonates (limestone and dolomite), which dominate the
area's stratigraphic column (Florida Geological Survey well data). In the
near-surface, the lithology changes to predominantly siliciclastic
sediments consisting of hundreds of feet of marine sands and clays, with
interbedded limestones and dolomites (Clark et al., 1964). Figure 3a is a
map showing geologic cross section locations used in this report.
Figures 3b, 3c, and 3d are west-east and north-south geologic cross
sections showing the near-surface sediments of Union and Bradford
The oldest rock penetrated by water wells in the area is the Avon Park
Formation, which was deposited approximately 49 to 41 million years
before present (B.P.) during the Middle Eocene Epoch. This formation
and the younger overlying limestone units are an integral part of the
Floridan aquifer system, the primary source of fresh water in the counties.
Typically, the Avon Park Formation occurs as a dense, tan to dark brown,
porous dolomite, frequently interbedded with tan, gray or cream-colored
limestone and dolomitic limestones of varying hardness (Clark et al.,
1964). It underlies the area at depths ranging from 260 to 460 feet below
MSL (Florida Geological Survey well data).
The Ocala Group limestones unconformably overlie the Avon Park
Formation throughout the area. These rocks, which in this report are
referred to as the Ocala Group undifferentiated, were deposited during the
Late Eocene Epoch (approximately 41 to 38 million years B.P.). The
lithology of the Ocala Group varies from white to tan, marine fossiliferous
limestone and dolomitic limestone, to white to pale orange, abundantly
fossiliferous, chalky limestones (Clark et al., 1964). In Union County, the
Ocala Group averages approximately 250 feet in thickness. The top of the
Ocala Group is encountered at depths ranging from approximately 20 feet
above MSL in the floodplain of the Santa Fe River in southwestern Union
County to nearly 190 feet below MSL in W-524 (section 16, Township 5S,
Range 21 E) in northeastern Union County. In Bradford County, the top of
the Ocala occurs at depths that range from 26 feet below MSL in W-5180
(section 32, Township 7S, Range 21E) to 292 feet below MSL in W-12360
(section 25, Township 4S, Range 22E) (Figures 3a, 3b, 3c, and 3d).
Thickness ranges from about 200 to 250 feet in Bradford County (Clark et
The Suwannee Limestone of Oligocene age (38 to 33 million years B.P.)
unconformably overlies the Ocala Group in sporadic occurrences in
western Union County and southwestern Bradford County (Clark et al.,
1964). The lithology of this formation is commonly a tan, white, or cream-
colored marine limestone, frequently dolomitic and coquinoid in portions
and varying in hardness. The top of the Suwannee Limestone occurs at a
depth of 38 feet above MSL in W-4533 (section 6, Township 6S, Range
18E), and varies in thickness from 10 to 40 feet. Where present, this
formation is also part of the Floridan aquifer system.
Phosphatic sands, clays, limestones and dolomites comprising the
Early and Middle Miocene (23 to 15 million years B.P.) Hawthorn Group
unconformably overlie the Suwannee Limestone in its area of occurrence.
In those portions of Union and Bradford Counties where the Suwannee
Limestone is missing, the Hawthorn Group unconformably overlies the
Ocala Group. These sediments, which are referred to as Hawthorn Group
undifferentiated in the cross sections, have variable and interbedded
lithologies characterized by phosphatic sands, granules and pebbles.
This unit has a generally northeastward dip in this area and ranges in
thickness from approximately 40 feet in parts of western Union County to
over 260 feet in the northeastern portion of the county near Raiford. In
Bradford County, the Hawthorn Group ranges in thickness from less than
100 feet in the southwest to over 310 feet in the northeast (Florida
Geological Survey well data).
Thick, relatively impermeable clays and clayey sands, present in the
Hawthorn Group, serve as a confining unit for the underlying Floridan
aquifer system. In contrast, quartz sand and carbonate units within the
Hawthorn Group are water-bearing and form part of the intermediate
aquifer system in the two county region (Hoenstine et al., 1989).
Undifferentiated quartz sands and clays unconformably overlie the
Hawthorn Group. These sediments form a veneer over the majority of
Union and Bradford Counties. This unit includes the unnamed reddish,
coarse siliciclastics, the relict Pleistocene Series (1.8 million to 10,000
years ago) marine terrace sands, and Holocene (10,000 years ago to
present) aeolian, lacustrine and alluvial deposits. Sediments within this
unit and in the thin limestone layers in the uppermost Hawthorn Group
contain the surficial aquifer system in Union and Bradford Counties.
The purpose of the following discussion is to provide information on the
occurrence of certain economic mineral commodities in Union and
Bradford Counties. The information presented is not intended to be an
exhaustive investigation leading to immediate industrial development.
However, favorable information may indicate that certain areas warrant
further investigation. The Mineral Resources Map is designed to present a
geographic overview of the major economic mineral commodities
identified in the area. Factors such as thickness of overburden, quality,
and volume of the deposit could affect the mining of the mineral
commodity at any specific site. In contrast, geologic cross sections have
been extrapolated from cores and/or well cuttings to show the
distribution and thickness of surface and near-surface stratigraphic units
(Figures 3b, 3c, and 3d). As a result, occasional variations between the
geologic cross sections and the Mineral Resources Map may occur. The
following is a discussion of the clay, heavy minerals, limestone, peat,
phosphate, sand and the undifferentiated resources of the study area.
Bell (1924) studied the economic clay reserves of northern peninsular
Florida. He concluded that sandy clays are present in Union and
Bradford Counties, however, the clay was not considered suitable for
commercial use. These sandy clays include floodplain deposits present
along the Santa Fe River (Mineral Resources Map). Subsequent surveys
by the U. S. Soil Conservation Service (SCS) (1989a; 1989b) as well as
field work for this report support these early findings.
Quartz sand containing a very small fraction of heavy minerals occurs
over most of Florida. A small area of northeastern Bradford County near
the town of Highland, Florida is known to have heavy minerals in a
quantity substantial enough to be considered for commercial production
(personal communication, U. S. Bureau of Mines). The Highland ore
deposit (Pirkle et al., 1977) is present in northeastern Bradford, Clay,
Baker and Duval Counties. The deposit averages about three percent
heavy minerals of which approximately 45 percent are titanium-bearing
minerals. Pirkle et al. (1977) report the titanium dioxide (Ti02) content of
those minerals is about 69 percent. The heavy minerals associated with
this deposit include ilmenite, leucoxene, staurolite, zircon, kyanite,
sillimanite and tourmaline (Pirkle et al., 1977).
E. I. duPont de Nemours Company leases much of the Highland ore
deposit area as well as mineable deposits along the Trail Ridge which are
mined in neighboring Clay County. Company statistics are held in strict
confidentiality, therefore, the value and production criteria are unavailable.
A study by Tyrrell and Klinefelter (1956) concluded that heavy-mineral
processing tailings may be used as ceramic raw material. The heavy-
mineral sands of the region continue to hold promise for future economic
Limestone occurs at depths of 40 feet or more below land surface
throughout the two counties (Figures 3b, 3c, 3d). Figure 3c shows the top
of the Ocala Group rises to within 40 feet of land surface. Overlying
sediments along the river consist of sandy clays, clayey sands, and clays
(see Mineral Resources Map). Limestone outcrops sporadically in the
Limestone mining has never occurred in either Union or Bradford
Counties. Due to the proximity of limestone deposits to the Santa Fe
River, mining would warrant major environmental considerations.
However, in neighboring Alachua County, Ocala Group limestone is
mined extensively. These nearby locations of commercial grade
limestone deposits lessen the probability of mining the Union County
limestone deposits in the near-future.
Peat is an accumulation of partially decomposed plant remains which
accumulates in perennially wet areas (Davis, 1946; Bond et al., 1986).
Along with wet conditions, other factors such as climate and topography
play an important role in the formation of this material. Union and
Bradford Counties have areas of potential peat accumulation. These
areas are located primarily in the northern region of Union County near
Palestine Lake, Swift Creek Pond, and Turkey Creek Swamp. In Bradford
County the areas are clustered around the Lake Sampson region, in the
Santa Fe Swamp, and near Hampton where Davis (1946) analyzed peat
material (Table 1).
The U. S. Soil Conservation Service (1989a; 1989b) designated those
areas mentioned above along with numerous smaller areas as highly
organic soils (Mineral Resources Map). Dorovan muck is the primary
organic soil type in these areas and attains a known thickness of at least
80-inches (the maximum depth interval sampled by the Soil Conservation
Service). Much of the Santa Fe Swamp, in southeastern Bradford County
(see Mineral Resources Map), contains Dorovan muck (SCS, 1989b).
Georgia-Pacific Corporation has investigated this area relative to using the
organic material as a potential energy source. However, it is presently
under the jurisdiction of the Suwannee River Water Management District,
which probably precludes its exploitation.
Peat is not presently mined in Union or Bradford Counties. However, in
nearby Putnam County peat is mined and used for horticultural purposes.
Florida and North Carolina provide over 75 percent of the phosphate
produced in the United States and greater than 25 percent of the world's
phosphate production (Florida Phosphate Council, 1989). The phosphate
mined in Florida is from the Miocene Hawthorn Group. Although
sediments of the Hawthorn Group are present in Union and Bradford
Counties, their phosphate content is not as high as other areas of Florida.
Analyses conducted by the U.S. Bureau of Mines on Hawthorn Group
sediments in three wells in Bradford County showed average P20O
contents of 3.5 percent (Davis et al., 1983). In a report prepared for the U.
S. Bureau of Mines, Zellars and Williams, Inc. (1978) defined the limits of
the North Florida Phosphate District and included nearly all of Union and
Bradford Counties. They characterized the district as follows:
Thickness of overburden
Thickness of ore zone
Pebble percent of product
Percent Bone Phosphate Lime (BPL)
Percent U308 of product
With the exception of Hamilton County, the characteristics of this district,
especially pebble percent and BPL content, are not sufficient to compete
economically with deposits located farther south in the peninsula. These
unfavorable economic factors probably preclude the mining of phosphate
here in the near future.
Quartz sand is present over most of Bradford and Union Counties.
However, there are no commercial sand mining operations within the
boundaries of Union and Bradford Counties. Nearby, in western Clay
County, along the Trail Ridge, deposits of quartz sand and heavy-mineral
sand have been mined for many years (Spencer et al., in preparation.).
An area along the Trail Ridge offers the greatest potential for
commercial sand mining in this two-county region. In this part of Trail
Ridge in Bradford County, elevations rise to 200 feet above MSL. The
authors defined the sand resource area to include elevations down to the
170 foot contour. This area is considered to afford the best potential as a
sand resource, based on elevation and knowledge of mining activities
along the Trail Ridge (past and present).
Much of Union and Bradford Counties have surface and near-surface
sediments comprised of undifferentiated clayey sand and sandy clay.
Many low-lying, perennially wet areas have sandy or clayey soils with high
percentages of decomposed organic matter, often called "muck." The
potential for large scale economic utilization is diminished by the
heterogeneous nature of these sediments. However, they are locally
valuable as fill, and have use as top soil.
The Florida General Soils Atlas (Kolb, 1974) presents information on
soil potential and uses a rating system which implies predictable material
performance. Several areas are rated as "good" source areas of road fill
material. A good rating for road fill means the sediment will remain intact
after proper compaction and drainage are incorporated, and the soil is
easily excavated. The Interim Soil Surveys for Union County (SCS, 1989a)
and Bradford County (SCS, 1989b) list several soils as probable sources
of construction sand. Although these probable sand source areas are
scattered over the two-county region, the authors believe the Trail Ridge
to be the best sand resource area, based on field reconnaissance. Along
the sand resource area of the Trail Ridge (down to the 170 foot contour)
the SCS identifies the primary soil types as Leon, Allanton and Pottsburg
The Union County Road Department currently operates three borrow
pits for fill material and Bradford County maintains two borrow pits.
Clayey sand extracted from these pits is used as a road-bed material and
fill on many of the county's unpaved roads. Further investigation can
better define these potential resources.
(From Davis. 1946)
Moisture Free Basis, Analysis in Per Cent
Proximate Analysis Ultimate Analysis
Volatile Fixed BTU Per Pound
Sample/Location Matter Carbon Ash N C N 0 S Moisture Free
sec. 30, T7S, R22E 48.5 33.7 17.8 4.0 53.4 2.0 22.5 0.3 8680
Barnett, R. S., 1975, Basement structure of Florida and its tectonic
implications: Gulf Coast Association of Geological Societies
Transactions, v. 25, p. 122-142.
Bell, 0. G., 1924, A preliminary report on the clays of Florida: Florida
Geological Survey Fifteenth Annual Report, 266 p.
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 27, 151 p.
Clark, W. E., Musgrove, R. H., Menke, C. G., and Cagle, J. W., 1964, Water
resources of Alachua, Bradford, Clay and Union Counties, Florida:
Florida Geological Survey Report of Investigation 35, 170 p.
Cooke, C. W., 1939, Scenery in Florida interpreted by a geologist: Florida
Geological Survey Bulletin 17,118 p.
Davis, B. E., Sullivan, G. V., and Llewellyn, T. 0., 1983, Part II -
Characterization and Beneficiation of the northeastern Florida
phosphate-bearing Hawthorn Formation: in The Hawthorn Formation
of northeastern Florida, Report of Investigation 94, 90 p.
Davis, J. H., Jr., 1946, The peat deposits of Florida, their occurrences,
development, and issues: Florida Geological Survey Bulletin 30, 247 p.
Florida Phosphate Council, 1989, Fact Sheet: Phosphate Feeds You.
Force, E., and Garner, T., 1985, High-angle aeolian crossbedding at Trail
Ridge, Florida: Industrial Minerals, August 1985, pp. 55-59.
Healy, H. G., 1975, Terraces and shorelines of Florida: Florida Bureau of
Geology Map Series 71, scale 1:2,000,000.
Hoenstine, R. W., Cooper, R., and Lane, E., 1989, An extension of the
intermediate aquifer system in north-central Florida [Abs.]: Florida
Scientist, v. 52, p. 29-30.
Kolb, W.O., 1974, The Florida general soils atlas with interpretation for
regional planning districts III & IV: Florida Department of
Administration, Division of State Planning, Bureau of Comprehensive
Planning, 44 p.
Lloyd, Jacqueline M., 1985, Annotated bibliography of Florida basement
geology and related regional and tectonic studies: Florida Geological
urvey Information Circular No. 98, 72 p.
MacNeil, F. S., 1950, Pleistocene shorelines in Florida and Georgia: U.S.
Geological Survey Professional Paper 221-F, p. 95-107.
FEET / METERS
Pirkle, E.C., Pirkle, W.A., and Yoho, W.H., 1977, The Highland heavy-
mineral sand deposits on the Trail Ridge in northern peninsular Florida:
Florida Geological Survey Report of Investigation 84, 50 p.
Puri, H. S., and Vernon, R. 0., 1964, The geology of Florida and a
guidebook to classic exposures: Florida Geological Survey Special
Publication 5 (revised), 312 p.
Spencer, S.M., Yon, J.W., Jr., and Hoenstine, R.W., in preparation, The
mineral resources of Clay County, Florida: Florida Geological Survey
Map Series, Scale: 1 inch = 2 miles.
Tyrrell, M. E., and Klinefelter, T. A., 1956, Ceramic materials from beach-
sand concentrator wastes: U. S. Bureau of Mines Report of
Investigations 5216, 25 p.
United States Soil Conservation Service, 1989a, Interim Report 1989,
Soil survey of Union County, Florida: U. S. Department of Agriculture
Soil Conservation Service in cooperation with the University of Florida,
Institute of Food and Agricultural Services, 91 p.
United States Soil Conservation Service, 1989b, Interim Report 1989,
Soil survey of Bradford County, Florida: U. S. Department of
Agriculture Soil Conservation Service in cooperation with the University
of Florida, Institute of Food and Agricultural Services, 91 p.
Vernon, R. 0., 1942, Geology of Holmes and Washington Counties,
Florida: Department of Conservation, Florida Geological Survey
Bulletin 21, 161 p.
White, W. H., 1970, Geomorphology of the Florida peninsula: Florida
Geological Survey Bulletin 51, 164 p.
Zellars and Williams, Inc., 1978, Evaluation of the phosphate deposits of
Florida using the minerals availability system: Final report prepared for
the U. S. Bureau of Mines, 196 p.
SANDS AND CLAYS
Figure 1. Geomorphology
(modified from White, 1970)
Figure 3b. Geologic Cross section A-A'
FEET / METERS
: 170'-215' COHARIE TERRACE
100'-170' INCLUDES SUNDERLAND TERRACE (COOKE, 1939),
OKEFENOKEE TERRACE (MACNEIL, 1950).
70'-100' WICOMICO TERRACE
Figure 2. Terraces and Shorelines
(modified from Healy, 1975)
Figure 3c. Geologic Cross section B-B'
FEET / METERS
0- 10 UMS
0 4 Miles
0 6 Kilometers
Figures 1. 2, 3o
Figure 3a. Geologic Cross section locations
The well system used in this
report uses the rectangular system of
section, township and range for
identification. The well or outcrop
number consists of six parts: W for well
or L for quarry, county abbreviations,
the Township, Range, and Section,
and the quarter/quarter location
within the section.
0 4 Mile.
0 6 Kilometers
Figures 3b.3c. and 3d
VERTICAL EXAGGERATION IS APPROXIMATELY 264 TIMES
Figure 3d. Geologic Cross section C-C'