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Map Series No. 133
MINERAL RESOURCES OF CLAY
Steven M. Spencer, P.G. #319, J. William Yon,
Jr., Ronald W. Hoenstine and Ed Lane
FLORIDA GEOLOGICAL SURVEY
WALTER SCHMIDT, STATE GEOLOGIST AND CHIEF
DIVISION OF RESOURCE MANAGEMENT
DEPARTMENT OF NATURAL RESOURCES
in recent years considerable attention has been focused on
Florida's rapid development, the accompanying population increase,
and their effects on the state's important mineral resources.
Frequently, this development occurred in areas underlain by known
mineral deposits, precluding extraction of the minerals. These
mineral resources provide substantial employment and income to the
private sector as well as taxes 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
In response to this act and at the request of the Northeast Florida
Regional Planning Council, the Florida Geological Survey initiated a
study of Clay County's mineral resources. The objective of this report
is to interpret and summarize geologic data (i.e., core and well cutting
descriptions, geophysical logs, and data derived from field
reconnaissance) in a format appropriate for use by city and county
A knowledge of Clay County's mineral resources is basic and
integral to the process of initiating, developing and implementing an
effective comprehensive land use plan. This information is essential
to planners and officials in their analyses of urban and rural
development in such areas as zoning, road construction and the
establishment of waste disposal sites.
Factors used in evaluating the economic value of the county's
known and potential mineral resources are varied, changing and in
many instances interrelated, thus complicating an accurate
assessment. The evaluation process is inherently dependant on an
extensive exploration program to determine reserves, content and
extent of specific mineral resources. In addition, such factors as
operating expenses, transportation, beneficiation, reclamation and
capital costs of mining must be included in the overall calculations.
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sources including Florida Geological Survey reports and unpublished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, company
reports, questionnaires, and numerous discussions with mining
company personnel and state and federal officials. Although detailed
information on company statistics is confidential, information of a
more general nature is readily available or can be reasonably
extrapolated from existing data. The diversity of sources as well as
their close association to the various aspects of resource evaluation
lends substantial confidence to the general assessment and
inferences of this report.
tMeTRIC CONVERSION FACTORS
To prevent the duplication of English and metric units in this report,
the following conversion factors are provided.
Located in northeast Florida,
(1970) Northern (Proximal) Zone
This zone is characterized by a
extends across the northern Florid
Western Highlands of Florida's p
divided into a number of geomori
are present in Clay County. Thes
Trail Ridge, Duval Upland, Peoria
The Northern Highlands cove
County (Figure 1). The topograpl
numerous lakes and elevations tha
mean sea level (MSL). The ea
Highlands in Clay County is marl
which approximates the 100 feet al
(1970) describes this break as the
the Atlantic Coastal Plain.
Trail Ridge is located along th
border of Clay County. This dist
Northern Highlands. Elevations
northeastern Florida, averaging ove
mineral deposits present in the
BY TO OBTAIN
5/9 F-32) centigrade
Clay County falls within White's
which traverses northern Florida.
continuous broad upland which
a peninsula and westward into the
)anhandle. The Northern Zone is
phic subdivisions, several of which
e include the Northern Highlands,
Hill and the Eastern Valley (Figure
rs the western one-third of Clay
hy of this area is characterized by
at frequently exceed 200 feet above
stern boundary of the Northern
ked by the Cody Scarp, the toe of
bove MSL elevation contour. White
best known relict marine scarp of
he northwestern and west-central
inctive feature is a subunit of the
s here are among the highest in
er 200 feet above MSL. The heavy-
area represent one of the largest
concentrationsl inUtl I|| |11 a zUI[ t a a ar ie U O I l o nii, s
The Duval Upland is located to the east of Trail Ridge and the
Northern Highlands. This north-south approximately linear
geomorphic feature is characterized by elevations much lower than
those of Trail Ridge, averaging 100 feet above MSL. The gently
sloping topography of the Duval Uplands includes much of the central
one-third of Clay County.
The Eastern Valley occupies the eastern portion of Clay County.
Although placed by White (1970) in the Central Highlands, this feature
extends into the Northern (Proximal) Zone and lies contiguous to the
eastern boundary of the Duval Upland in Clay County. A number of
swampy areas are present in the Eastern Valley. In general, this area
has the lowest elevations in the county, ranging from a low of
approximately six feet above MSL along the St. Johns River to 30 feet
above MSL near the eastern edge of the Duval Upland (Figure 1).
White (1970) interpreted the Eastern Valley as representing an ancient
beach-ridge plain with relict beach ridges throughout that are coast-
Peoria Hill is a small, irregular shaped feature identified by White
(1970) as being present in the northeastern part of Clay County along
the St. Johns River. Its elevations are distinctly higher than the
surrounding Eastern Valley.
In addition to the above geomorphic features a number of relict
terraces formed by ancient seas are present in the county. Healy
(1975) identified seven terraces in Clay County based on land surface
elevations (Figure 2). In order of descending elevation, they are:
Hazelhurst Terrace (215-320 feet above MSL), Coharie Terrace (170-
215 feet above MSL), Sunderland Terrace (100-170 feet above MSL),
Wicomico Terrace (70-100 feet above MSL), Penholoway Terrace (42-
70 feet above MSL), Talbot Terrace (25-42 feet above MSL) and
Pamlico Terrace (10-25 feet above MSL).
The geology of Clay County is characterized by surface and near-
surface occurrences of siliciclastic sediments (quartz sand, silt, clayey
sand and clay) underlain by thick sequences of carbonates (limestone
and dolomite). In turn, these sediments overlie Paleozoic Era base-
ment rocks at depths of more than 3,000 feet below land surface. A
deep oil test well (W-1590, section 4, Township 6S, Range 25E) drilled
by Humble Oil and Refining Company encountered a Paleozoic age
quartzitic sandstone at a depth of approximately 3,600 feet below
MSL (Applin, 1951).
Figure 3a is a map showing the location of geologic cross sections
used in this report. Figures 3b, 3c and 3d are the geologic cross
sections of sedimentary rocks of Late Eocene and younger age. The
Ocala Group limestone is an important and productive part of the
Roridan aquifer system in Clay County. Deposited during the Eocene
Epoch, 57 to 36 million years before the present (BP), these rocks
generally consist of a soft, white, chalky, relatively pure limestone
containing abundant fossils foraminiferaa, mollusks, bryozoans and
echinoids). The top of the Ocala Group is typical of a karst surface
with numerous sinkholes and depressions. Present throughout Clay
County, the Ocala Group occurs at varying depths ranging from 80 to
300 feet below MSL (Florida Geological Survey well data). A
maximum observed thickness of 254 feet was encountered in W-
10633 (section 4, Township 4S, Range 26E) in northeastern Clay
County near Orange Park.
Hawthorn Group lithologies, which were deposited during the Early
to Middle Miocene (23 to 15 million years BP) overlie the Ocala Group
limestone throughout the county. The lithology of these sediments is
diverse, consisting of interbedded phosphatic clay, silt, clayey quartz
sand and dolomite. Three formations comprise this group in Clay
County (Scott, 1988a). They are, from oldest to youngest, the Penney
Farms Formation, the Marks Head Formation and the Coosawhatchie
The highly variable nature of the Hawthorn lithologies in this area
makes identification of the individual units difficult. Therefore, these
rocks are referred Ito as Hawthorn Group undifferentiated in the cross
sections of this report (Figures 3b and 3c).
The top of the Hawthorn Group is variable in depth averaging
approximately 25 to 50 feet above MSL. The thickness varies from
less than 225 feet in the northwestern part of the county to as much as
370 feet in north-central Clay County (W-14219, section 27, Township
4S, Range 24E). Approximately 15 feet of Hawthorn Group sediments
(that are overlain by 7 to 10 feet of undifferentiated sands and clays)
can be observed at the Florida Solite Mine (section 39, Township 5S,
Poorly indurated, clayey, silty quartz sands overlie the Hawthorn
Group in western Clay County. These Pleistocene age siliciclastics,
formerly included in the Citronelle Formation by Cooke (1945), have
recently been placed in the Cypresshead Formation (Scott, 1988b).
The Nashua Formation overlies the Hawthorn Group in the
northeastern part of Clay County. The lithologies of this unit range
from an unconsolidated calcareous shelly sand to a sandy shell bed.
Huddlestun (1988) dates this formation as Late Pliocene in age based
on planktonic foraminifera. The lower surface of this unit occurs at
elevations which range from approximately 8 to 6 feet below MSL,
while its thickness varies from 10 to 55 feet in W-14193 (section 13,
Township 4S, Range 25E) and W-14476 (section 17, Township 6S,
Range 26E), respectively (Figure 3d).
Undifferentiated sand, clay and shell with maximum thicknesses of
over 100 feet cover Clay County (Figure 3c). These Pleistocene and
Holocene age deposits are composed of a clayey sand with
occurrences of shell material. An exception is northeastern Clay
County where the surface sediments are predominantly a sandy clay.
The mineral resources map and following discussion of the
economic geology of Clay County is not intended to be a complete
investigation leading to immediate industrial development because, in
many cases, the data represents information on a single outcrop, pit
or mine. Favorable data, however, may indicate that certain areas
warrant further investigation. The Mineral Resources Map is designed
to present an overview of the major mineral commodities in an area.
Factors such as thickness of overburden, quality, and quantity or
volume of the deposit, all have an effect on mining of a mineral
commodity at any one specific site. Geologic cross sections (Figures
3b, 3c and 3d) were generated from core and well cuttings to show
the general distribution and thickness of surface and near-surface
stratigraphic units. The following is a discussion of the clay, heavy
minerals, peat, phosphate, sand and the undifferentiated resources of
Clay minerals (smectite and kaolinite) are common to abundant in
various regions of Clay County. Miocene age Hawthorn Group clays
and Pleistocene to Holocene age undifferentiated alluvial deposits
dominate the surface and near-surface sediments in the northeastern
portion of the county. Sediments in the southwestern corner are
kaolin-bearing sands associated with the Pleistocene age
Kaolinite, a hydrous aluminosilicate, is used in the manufacture of
such items as china ware, paper coating, tile, glaze, and pottery. The
clay, which comprises a matrix material of the Cypresshead, was
analyzed by Calver (1949). The samples were taken from an old,
abandoned kaolin mine (Chalk Hole) located in section 6, Township
8S, Range 23E. Results of the tests indicated the kaolin to be of high
quality similar to the finest produced in Florida at the time. There are
no active kaolin mines in Clay County at the present time.
Ball (1924) conducted a study of the clay resources in a number of
Florida counties. He analyzed samples of common clay and kaolin for
their physical properties. In Clay County, Bell (1924) analyzed
samples from what were then established common clay production
areas such as Doctors Inlet, Middleburg and Green Cove Springs. Bell
also tested the kaolinitic quartz sands near White Sand Lake north of
Keystone Heights. Results of Bell's numerous tests indicate that the
clay from Doctors Inlet was satisfactory for a good grade of common
brick, drain tile, and hollow block. The potential uses for the
Middleburg clay included face brick, common brick, drain tile and
hollow ware. Green Cove Springs clays were suitable for common
brick and drain tile manufacturing. The clay sample (kaolin) from near
White Sand Lake was suitable, if washed, for some grades of white
Calver (1949) tested clays from the Green Cove Springs area,
Russell and Middleburg. The results from the Green Cove Springs
deposit indicated the clay would be unsuitable for common brick. The
Russell deposit was found to be usable for face brick, drain tile, and
common brick. The Middleburg clay was found to be suitable for
hollow ware in addition to the Russell deposit usages.
Hickman and Hamlin (1964) conducted a study on clay sediments
from several northeastern Rorida counties. Within Clay County their
study centered on 59 test holes in the Doctors Inlet to Middleburg
region along State Highway 21 and County Highway 220. Their
findings were similar to previous investigations indicating that the
clays could be used in the manufacture of common brick.
Additionally, due to positive results during bloating tests, potential
uses included lightweight aggregate in hole 36 (section 34, Township
4S, Range 25E) Table 1, hole 42 (section 6, Township 5S, Range 25E)
Table 2, and hole 53 (section 14, Township 5S, Range 25E) Table 3.
Florida Solite Corporation, located near Russell in section 39,
Township 5S, Range 25E, is the only company actively mining clay in
the county. They extract the commodity from a deep, massive,
northwest trending deposit at a depth of approximately 30 feet (John
Kuiken, personal communication, 1989). Up to 10 feet of sand
overlies the clay deposit. The clay is naturally bloating and comprised
of smectite and minor amounts of kaolinite (Campbell, 1986). These
bloating properties are essential for the successful production of
lightweight aggregate, the company's primary product.
Heavy-mineral sands occur as a small fraction in nearly all of
Rorida's sand deposits. The source region for peninsular Florida's
heavy minerals is the Piedmont and Blue Ridge region of the
Appalachian Mountains. The weathering products of the
Appalachians were transported by streams which deposited.them in
alluvial, deltaic, and longshore environments (Pirkle et al., 1974).
The first commercial production of heavy-mineral sands began in
1916 at Mineral City, now called Ponte Vedra, St. Johns County. Mr.
H. Buckman and Mr. G. Pritchard began a mining and milling
operation at the site for the manufacture of titanium tetrachloride,
used for war purposes.
The United States Bureau of Mines (Thoenen and Warne, 1949)
conducted a study and drilled over 700 test. holes in 1947 to 1948 in
northeastern Florida. Much of that investigation was centered around
the Trail Ridge region. The U.S. Bureau of Mines (USBM) drilled holes
along State Highway 100 neai Keystone Heights, along State Highway
21 near the Mike Roess Gold Head Branch State Park, near the Clay-
Bradford county line, and in northwestern Clay County near Highland.
Thoenen and Warne (1949) indicated that the Gold Head Branch State
Park contains sediments with over 6 percent heavy minerals.
Partially, as a result of the USBM study of that area, the E.I. duPont de
Nemours Company ultimately began mining heavy-mineral sands
in the Camp Blanding Military Reservation.
There are three ore deposits in Clay county: the Trail Ridge and
the Highland ore deposit along the western boundary of Clay County,
and the Green Cove Springs ore deposit in the southeastern part of
the county. E.I. duPont de Nemours has mined large tracts of land in
western Clay County. RGC (USA) Minerals, Inc., formerly Associated
Minerials, mines the Green Cove Springs deposit.
Heavy minerals present in the Trail Ridge area characteristically
include the titanium minerals ilmenite, rutile and leucoxene which
comprise approximately half of the total volume of recovered heavy
minerals (RHM) (Reeves, 1962). Zircon is next in abundance at 10-15
percent RHM; the other minerals include monazite, staurolite, kyanite,
sillimanite, tourmaline, andalusite, pyroxene, spinel and corundum, all
of which comprise about 40 percent of the remainder RHM (Reeves,
The Highland Ore body averages about three percent heavy
minerals with the titanium minerals accounting for about 45 percent of
the RHM ore minerals (Pirkle et al., 1977). The average TiO content
of the titanium minerals is 69 percent. Other minerals present in the
deposit include staurolite, zircon, kyanite, slllimanite and tourmaline
(Pirkle et al., 1977).
The Green Cove Springs deposit has, in addition to those minerals
found in the other two deposits, lesser amounts of epidote and garnet
(Pirkle et al., 1974). This deposit of heavy minerals occurs at the top
of a scarp whose toe is at an approximate elevation of 40 feet above
MSL (Pirkle et al., 1974).
Although company statistics are confidential as to the amount of
material produced and the value of those minerals, the USBM reports
that Florida is the leading producer of heavy minerals in the United
States. Geologists continue to explore areas for new deposits to add
to their reserves as old deposits are mined out. The heavy mineral
sands of Clay County continue to hold promise for future operations.
Peat is the accumulation of decomposed organic material, which
collects in perennially wet areas (Davis 1946; Bond et al., 1986). Other
factors of importance for the accumulation of peat include climate and
topography. Specific areas in Clay County are suited for the
accumulation of this commodity and, in fact, peat is presently mined
in southwestern Clay County by Stricklin Peat Inc. (section 16,
Township 8S, Range 24E) (Mineral Resources Map). The areal extent
of the Stricklin mine is approximately 100 acres with a maximum
depth of 28 feet.
Griffin et al. (1982) mapped several peat deposits in Clay County.
However, detailed information on the deposits are not available. The
United States Soil Conservation Service (1989) interim report on the
soils of Clay County shows numerous locations of highly organic soils.
It is the organic-rich Maurepas Muck that is mined as peat in southern
Clay County. Pamlico Muck, another soil type, is also a potential
source for peat.
The Mineral Resources Map shows the location of the previously
mentioned soils which are associated with peat or peaty muck as well
as areas where peat has been or is now mined. In addition to
deposits scattered throughout the county, many highly organic
(peaty) soils are located in the swampy lowlying areas along the St.
Johns River, and Black Creek and its tributaries.
Mining procedures generally used by peat operators include
removal of surface vegetation followed by site dewatering and
subsequent removal of the peat by dragline or bulldozer. The material
is shredded and stockpiled for future use. Currently, all Florida peats
are used for horticultural purposes.
Economic deposits of phosphate are known to exist in several
counties throughout Florida. Clay County is situated in the
Northeastern Phosphate District (Scott, 1988a). Phosphate sediments
in this district are of the pebble and sand-sized variety and are from
the Hawthorn Group. Characteristics of the phosphatic sediments are
NORTHERN PHOSPHATE DISTRICT
Overburden thickness in Feet 50-150
Ore zone thickness in Feet 5-50
Bone Phosphate of Lime (BPL) in precent 62-65
(Source: Zellars and Williams, 1978).
The low economic value of the Clay County phosphatic sediments
probably precludes mining in the near future.
Quartz sand occurs over most of Clay County. It is a primary
component of the Cypresshead Formation and the Pleistocene-
Holocene deposits occurring in the county. The known deposits of
commercial quartz sand found in the county come from the Northern
Highlands area In the southwestern part of Clay County.
Martens (1928) collected and analyzed a number of sand samples
from the following locations in Clay County:
LOCALITY PERCENT PASSING EACH SIEVE
1/4 inch 10 20 50 80 100 200
One mile west of
Green Cove Springs 100.0 -- 96.80 55.80 -- 12.70 3.80
Green Cove Springs 100.0 -- 100.00 97.30 -- 8.80 0.60
Kingsley Lake 100.0 -- 99.90 52.90 -- 0.90 0.02
Two ond one-half 100.0 -- 99.00 71.20 -- 13.60 1.70
miles southwest of
In his analyses of the above samples Martens (1928) determined
that the sample from two and one-half miles southeast of Lake
Geneva was satisfactory for use in the manufacture of concrete.
RFlorida Rock Products currently mines sand from similar deposits at
their Goldhead Mine located in section 2, Township 8S, Range 23E.
Sand is mined at the Goldhead Mine by suction dredge from an open
water-filled pit. From the pit, the sand is pumped in a slurry to screen
shakers where the sand is separated into several size fractions. These
sands are utilized for manufacturing concrete and as a masonry sand.
A number of borrow pits are used by local operators and the Clay
County Road Department for road construction and fill (Mineral
Resources Map). Samples were collected for testing from two borrow
pits (Mineral Resources Map).
Laboratory procedures involved in analyzing the above samples
consisted of drying then quartering using a riffle type splitter. One
quarter was then weighed and screened using a U. S. Standard Sieve
Series. Information from the analysis of this sample is presented in
In the Rorida General Soils Atlas (Kolb, 1974), soils information is
presented which is useful in determining an area's suitability for
various land uses. The soil survey indicates that the Tavares-Myakka-
Bassinger soil association is a good source for sand. The good rating
for this soil association means that the sand is at least three-feet thick
and its top is within six feet of the land surface. Mining factors such
as thickness of overburden, quality of the material and depth to the
water table are not considered in the sand rating. The
Tavares-Myakka-Bassinger soil association occurs along the southern
border of Clay County in the Northern Highlands and the Duval
Upland (Kolb, 1974).
The abundance of potential construction sand in the Northern
Highlands in southwestern Clay County makes the possibility for
developing this area for sand mining relatively high. As indicated by
the number of borrow pits, the sand areas in other parts of the county
have a good potential for use as fill material (Mineral Resources Map).
A large percentage of Clay County's surface and near-surface
sediments are comprised of undifferentiated clayey sands, marl, and
organic muck. The heterogeneous nature of these sediments would
tend to preclude any large scale economic marketability. Locally,
however, where costs are not prohibitive and the need is present for
uses such as fill or top soil, extraction on a small scale may be
feasible. If, in the future, a comprehensive investigation of these
undifferentiated sediments is undertaken, those data may lead to
economic or industrial applications.
American Society of Testing Materials, 1987, Annual book of
ASTM standards, section 4, v. 4.02 Concrete and Mineral
Aggregates: ASTM, Philadelphia, PA, 997 p.
Applin, P. L., 1951, Preliminary report on buried pre-Mesozoic rocks
in Rorida and adjacent states: U. S. Geological Survey Circular
91, 28 p.
Bates, R. L., and Jackson, J.A., eds., 1980, Glossary of geology
(2nd edition): Falls Church, Virginia, American Geological
Institute, 751 p.
Bell, 0. G., 1924, A preliminary report on the clays of Rorida (exclusive
of Fuller's Earth): Florida Geological Survey RFifteenth Annual
Report, pp. 53-260.
Bond, P. A., Campbell, K. M., and Scott, T. M., 1986, An overview of
peat in RFlorida and related issues, report to the Rorida
Legislature: Rorida Geological Survey Special Publication 27,
Calver, J. L., 1949, Rorida kaolins and clays: RFlorida Geological
Survey Information Circular 2, 59 p.
Campbell, K. M., 1986, The industrial minerals of RFlorida: Rorida
Geological Survey Information Circular 102, 94 p.
Cooke, C. W., 1939, Scenery of RFlorida interpreted by a geologist:
RFlorida Geological Survey Bulletin 17, 118 p.
1945, Geology of Rorida: Rorida Geological Survey
Bulletin 28, 339 p.
Davis, J. H., 1946, The peat deposits of Rorida, their occurrence,
development and uses: Rorida Geological Survey Bulletin 30,
RFlorida Department of Transportation, 1984, Manual of RFlorida
sampling and testing methods, sieve analysis of fine and coarse
aggregates: FDOT, designation FM 1-T 027, 6 p.
Griffin, G. M., Weiland, L.Q.H., Goode, R. W., Sawyer, R. K., and
McNeil, 0. F., 1982, Assessment of the peat resources of RFlorida,
with a detailed study of the northern Everglades: State of
Florida, Governor's Energy Office, Tallahassee, RFlorida, 190 p.
Healy, H. G., 1975, Terraces and shorelines of Florida: RFlorida Bureau
of Geology Map Series 71, scale 1:2,000,000.
Hickman, R. C., and Hamlin, H. P., 1964, Ceramic clay investigations
in Alachua, Clay, and Putnam Counties, RFlorida: Florida
Geological Survey Information Circular 102, 94 p.
Huddlestun, P. F., 1988, A revision of the lithostratigraphic units of the
coastal plain of Georgia the Miocene through Holocene:
Georgia Geologic Survey Bulletin 104, 162 p.
Kolb, W. 0., 1974, The Florida general soil atlas with interpretation for
regional planning districts III & IV: Rorida Department of
Administration, Division of State Planning, Bureau of
Comprehensive Planning, 44 p.
MacNeil, F. S., 1950, Pleistocene shorelines in Florida and Georgia:
United States Geological Survey Professional Paper 221-F, p.
Martens, J. H. C., 1928, Sand and gravel deposits of Florida: Florida
Geological Survey Annual Report no. 19, p. 33-123.
Pirkle, E. C., Pirkle, W. A., and Yoho, W. H., 1974, The Green Cove
Springs and Boulougne heavy-mineral sand deposits of Florida:
Economic Geology, v. 6, no. 7, pp. 1129-1137.
______ Pirkle, W. A., and Yoho, W. H., 1977, The Highland
heavy-mineral sand deposit on the Trail Ridge in northern
peninsular Florida: Florida Bureau of Geology Report of
investigation 84, 50 p.
Reeves, W. D., 1962, Mineral resources adjacent to the proposed
Trans-Florida Barge Canal: Rorida Geological Survey
unpublished report, 44 p.
Scott, T. M., 1978, Environmental geology series Jacksonville Sheet:
Rorida Bureau of Geology Map Series 89, scale 1:250,000.
1988a, The lithostratigraphy of the Hawthorn Group
(Miocene) of RFlorida: RFlorida Geological Survey Bulletin 59, 148
1988b, The Cypresshead Formation in northern
peninsular Rorida: in Pirkle, F.L., and Reynolds, J.G. (eds.),
Southeastern Geological Society Annual Fieldtrip Guidebook,
February 19 & 20,1988, 76 p.
Thoenen, J. R., and Warne, J. D., 1949, Titanium minerals in central
and northeastern RFlorida: U. S. Bureau of Mines Report of
Investigation 4515, 23 p.
United States Department of Agriculture Soil Conservation Service,
1989, Interim soil survey report Clay County, Florida: U. S.
Department of Agriculture Soil Conservation Service in
cooperation with the University of RFlorida, Institute of Food and
Agricultural Services, 92 p.
Vernon, R. 0., 1942, Geology of Holmes and Washington Counties,
Rorida: Rorida Geological Survey Bulletin 21, 90 p.
White, W. A., 1970, The geomorphology of the Florida Peninsula:
Rorida Geological Survey Bulletin 51,164 p.
Zellars and Williams, Inc., 1978, Evaluation of the phosphate deposits
of Rorida using the Minerals Availability System: Final report
prepared for the U. S. Bureau of Mines, 196 p.
Table 1. Hole No. 36
(from Hickman and Hamlin, 1964)
Type Unfired color
Clay Medium red groy
Longworklng, plastic, smooth, requiring 36% water for plasticity,
9.0% drying shrinkage, with no drying defects.
Percent Percent App.
Temp. 'F Color Hordness shrinkage absorption Sp.Gr.
1800 Salmon Hard 13.5 11.0 2.52
2000 Lt. red Very hard 13.5 5.4 2.41
2100 Med. red Very hard 16.0 3.4 2.42
2200 Very dk. red Very hard 16.0 3.5 2.36
2300 Expanded & Glozed -.. .
2400 Expanded & Glazed -- -- --
Temp. F Bulk density Ilb. cu. ft. absorpion Remarks
1800 1.48 92.2 17.1 No bloating
1900 1.29 80.4 17.1 No bloating
2000 1.08 67.3 20.5 Poor bloating
2100 1.06 66.0 16.9 Fair bloating
2200 0.72 44.9 20.2 Good bloating
2300 0.70 43.6 08.3 Good bloating
Table 2. Hole No. 42
(from Hickman and Hamlin, 1964)
Type Unfired color
loay Dark Brown
Longworking. plastic, smooth, requiring 29% water for plasticity.
10V drying shrinkage, with no drying defects.
Temp. 'F Color Hordnes sl
Ok. red brown
Percent Percent App.
hrinkage absorption Sp.Gr.
Brick & ULghtweight
Table 3. Hole No. 53
(from Hickman and Hamlin. 1964)
Type Unfired color
Sandy cloy Gray-block
Longworking, plastic, requiring 31X water for plasticity,
10.0X drying shrinkage, with no drying defects.
Percent Percent App.
Temp. "F Color Hardness shrinkage absorption Sp.Gr.
1800 Cocoa brown Hard 10.5 13.4 2.52
2000 Cocoa brown Very hard 13.5 9.0 2.46
2100 Dark brown Steel hard 14.5 4.3 2.16
2200 Expanded -- -- -
2400 Expanded .. .
Temp.'F Bulk density lb. cu. ft. absorplon Remarks
Table 3. (cont.)
Preliminary tests indicate that this clay could be used as decorative
brick if fired around 2000 F. The shrinkage is rather high, but it does
not eliminate the material entirely as a source of brick. If fired to
2100 F, the material might be used in the manufacture of sewer pipe
provided the shrinkage can be reduced by additions of sand.
The material seems to be more favorable for the manufacture of
lightweight aggregate. The bloating range is fairly long and the mate-
rials sees to be fairly strong when bloated. When fired around 2000
to 2100 F, the aggregate weight compares favorably with commercial
*33% of entire Sample 1 was retained in Pan.
**86% of entire Sample 2 was retained in Pan.
Fineness Modulus: A means of evaluating sand and gravel deposits
which consist of sieving samples through a standard set of sieves,
adding the cumulative weight percentages of the individual screens,
dividing by 100, and comparing the resultant fineness modulus to
various specification requirements (Bates and Jackson, 1980).
The fineness modulus is an index of the fineness or coarseness of an
aggregate, but gives no idea of grading. The higher the fineness
modulus the coarser the aggregate (ATSM 1987).
The method of sieve analysis presented here follows that outlined in
ATSM 1987, v. 4.02, section C136-84a. The reader is also referred to
the Rorida DOT Manual of Florida sampling and testing methods for
aggregates, FDOT, designation FM 1-T 027.
2.2 No bloating
9.7 Poor bloating
2.3 Fair bloating
6.4 Fair bloating
2.7 Good bloating
3.5 Good bloating.
Decorative brick, sewer
pipe. and lightweight
The well and quarry 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 abbreviation, the Township, Range, and Section,
and the quarter/quarter location within the section.
r NORTHERN HIGHLANDS
ms Trail Ridge
S DUVAL UPLAND
'N r CODY SCARP
Figure 1. Geomorphology
(modified from White, 1970)
Figure 2. Terraces and Shorelines
(modified from Healy, 1975)
T 320' TO 492' TO 357' TO 708'
Figure 3b. Geologic Cross section A-A'
WCy-6S-25E-7cd W- 14301
SAND CLAY AND-13769SHELL
SAND, CLAY AND SHELL
GROUP UNDIFFERENTIATED TO
Figure 3c. Geologic Cross section B-B'
215-320' INCLUDES HAZELHURST TERRACE (formerly Brandywine)
(Cooke, 1939). COASTWISE DELTA PLAIN (Vernon. 1942)
PART OF HIGH PULIOCENE TERRACE (MocNell. 1950).
170'-215' COHARIE TERRACE
100'-170' SUNDERLAND TERRACE (COOKE. 1939)
OKEFENOKEE TERRACE (MACNEIL. 1950)
70'-100' WICOMICO TERRACE
42'-70' PENHOLOWAY TERRACE
25'-42' TALBOT TERRACE
10'-25' PAMLICO TERRACE -N-
0'-10' SILVER BLUFF TERRACE
S0 2 4 MILES
0 2 4 6 KILOMETERS
-4S-26E-6 For Figures 1, 2, 3o
Figure 35a. Geologic Cross section locations
0 2 4 MESs
C I I I Y
~0 3 6 KLOMCTBB
-36CC VERTICAL. OwEOiNsPoIMAe 6 O ELM Y 211 TIMES
-"1 For Figure 3b. 3c, 3d
Figure 3d. Geologic Cross section C-C'
Table 4. Screen analyses of sand in Clay County, Florida
Laboratory Test Data/Screen Analysis/
Deposits Sieve No. and
Cumulative Weight Percent Retained
Sample Location Method of 4 8 16 30 50 100 Fineness
No. (T.R.Sec.) Sampling Modulus A
*Cloy-1 T5S, R24E Channel .006 .057 .936 1.06
**Clay-2 T6S, R26E Channel .012 .988 1.01