The geology of the western part of Alachua County, Florida ( FGS: Report of investigations 85 )
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Permanent Link: http://ufdc.ufl.edu/UF00001272/00001
 Material Information
Title: The geology of the western part of Alachua County, Florida ( FGS: Report of investigations 85 )
Series Title: ( FGS: Report of investigations 85 )
Physical Description: vi, 98 p. : ill. ; 23 cm.
Language: English
Creator: Williams, Kenneth E
Nicol, David, 1915- ( joint author )
Randazzo, Anthony F. ( joint author )
Florida -- Bureau of Geology
Publisher: The Bureau
Place of Publication: Tallahassee
Publication Date: 1977
Subjects / Keywords: Geology -- Florida -- Alachua County   ( lcsh )
Genre: government publication (state, provincial, terriorial, dependent)   ( marcgt )
bibliography   ( marcgt )
non-fiction   ( marcgt )
Statement of Responsibility: prepared for Bureau of Geology, Division of Resource Management, Florida Department of Natural Resources, by Kenneth E. Williams, David Nicol, and Anthony F. Randazzo.
Bibliography: Bibliography: p. 94-98.
General Note: Originated as the first author's thesis, University of Florida.
 Record Information
Source Institution: University of Florida
Rights Management:
The author dedicated the work to the public domain by waiving all of his or her rights to the work worldwide under copyright law and all related or neighboring legal rights he or she had in the work, to the extent allowable by law.
Resource Identifier: aleph - 000195874
oclc - 03691562
notis - AAW2549
lccn - 78621457
System ID: UF00001272:00001

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[year of publication as printed] Florida Geological Survey [source text]

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information and permissions.

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Harmon Shields, Executive Director

Charles M. Sanders, Director

Charles W. Hendry, Jr., Chief


Kenneth E. Williams, David Nicol and
Anthony F. Randazzo
University of Florida

Prepared for


7 -




Secretary of State


Commissioner of Education

Attorney General


Commissioner of Agriculture

Executive Director


Bureau of Geology
September 15, 1977

Governor Reubin O'D. Askew, Chairman
Florida Department of Natural Resources
Tallahassee, Florida 32304

Dear Governor Askew:

The Bureau of Geology, Division of Resource Management, De-
partment of Natural Resources, is publishing as its Report of In-
vestigation No. 85, "The Geology of the Western Part of Alachua
County, Florida."

This investigation represents a portion of the continuing program
to map the Geology of Florida. These type data are invaluable to a
multiplicity of resource users including water resource development
and management, industrial minerals development and environmental
problems such as sinkhole development or structural stability.

Respectfully yours,

Charles W. Hendry, Jr., Chief
Bureau of Geology

Completed manuscript received
Printed for the
Florida Department of Natural Resources
Division of Resource Management
Bureau of Geology


Acknowledgments ........................... ...... ............... 1
Abstract ........................................................... 2
Introduction ..................................................... 4
Methods of Investigation ....................................... 4
M aps ....................................... ................. 4
Previous Geologic Investigations .................................. 6
Physiography ....................... ................................ 8
Northern Highlands Plateau ................................. .. 10
Northern Highlands Marginal Zone ............................. 12
Alachua Stream System ....................................... 13
Fairfield Hills ................................... ............ 16
Western Valley (Newberry Limestone Plain) ..................... 17
Alachua Lake Cross Valley .................................... 21
Brooksville Ridge ............................................ 23
Brooksville Ridge Marginal Zone ............................... 24
Marine Terraces and Quaternary Geology ........................ 24
Structure .................... .................. ................ 28
Cross-County Fracture Zone ................................... 29
Measurement of Fracture Pattern ............................... 32
Stratigraphy and Paleontology ...................................... 34
Crystal River Formation ...................................... 36
Lithology ........................................ ......... 38
Residual Boulders ......................................... 38
Fauna and Zonation ........................................ 40
Environment of Deposition ................................ 45
D distribution ................................................ 46
Oligocene and Pre-Hawthorne Deposits .......................... 54
Hawthorne Formation .......................................... 56
Lithology .................................................. 56
Fauna ........................................ ........... 57
Distribution ................................................ 60
Residual Late Miocene Deposits ................................. 65
Alachua Formation ............................. ...... ....... 66
Lithology and Age ........................................ 67
Distribution ...................................... .......... 69
Plio-Pleistocene to Recent Deposits .............................. 71
Economic Geology ............................................... 73
Appendices ....................................................... 75
Appendix 1: Chart Summary of Selected Wells .................. 75
Appendix 2: Summaries of Selected Well Logs .................. 77
Appendix 3: Location of Profiles and Localities .................. 88
Appendix 4: Geologic Map, Western Alachua County ............. 89
Appendix 5: Figures 1 and 2 Illustrations of
Spirulaea vernoni Richards ................................. 90
References ......................................................... 92


Figure Page
1 Location of study area in Alachua County, Florida .............. 3

2 Topographic maps, western Alachua County .................... 5

3 Physiographic zones, western Alachua County .................. 9

4 Elevation profiles 1 and 2 ...................................... 11

5 Elevation profile 3 ................ .. ......... ....... ...... 14

6 Alachua stream system ........................................ 15

7 A typical sinkhole ... ................... ........ .............. 19

8 Piezometric surface, Alachua County .......................... 20

9 Poe Spring ..................................... ...... 21

10 Cross-county fracture zone .................................... 30

11 Fracture pattern, Crystal River Formation ....................... 33

12 Fracture pattern, Hawthorne Formation ....................... 33

13 Geologic Formations in western Alachua County ................ 35

14 Generalized area-time diagram, western Alachua County ......... 37

15 Comparison of faunal zonations of the Crystal River Formation .... 41

16 Faunal assemblages, Crystal River Formation .................. 43

17 Distribution of faunal zones, western Alachua County ............ 44

18a and b Typical boulders of the Crystal River Formation ............ 52

18c and d Spirulaea vernoni, Turritella martinensis, and
Rhyncholampus gouldii in boulders ....................... 53

19 Siderastraea Siderea Ellis and Solander ...................... 58

20 Occurence of Hawthorne Formation Corals ..................... 59

21 Alachua County Sanitary Landfill ............................. 72

22 Solution pipe, partially filled with Pleistocene sand .............. 73


This project began as a thesis by the senior author who was a
graduate student in the Department of Geology at the University
of Florida. The thesis was supervised by David Nicol, chairman, and
,two committee members: Anthony F. Randazzo and Graig D. Shaak.
The junior authors of this special publication have added photographs
and other illustrations and have rewritten some portions of the thesis
and have included a few additions to the original text.
The authors are particularly indebted to Graig D. Shaak and
S. David Webb of the Florida State Museum and to R. A. Edwards,
E. C. Pirkle, H. K. Brooks, and C. W. Hickcox of the University of
Florida. These geologists either read all or parts of the original manu-
script or offered helpful suggestions and geological information. The
staff at the Bureau of Geology in Tallahassee was helpful by provid-
ing the subsurface data and publications that were not available at
the University of Florida. This project was partially funded by a
research grant from the Florida Water Resources Research Center.



The western part of Alachua County lies in the north-central
portion of the Florida peninsula. The area consists of a low, nearly
flat, limestone karst plain bounded on the east by a subdued
westward-facing escarpment. Erosionally isolated, residual remnants
of the Hawthorne Formation are found in all areas of the limestone
plain and, in the southern portion of the county, large flat-bottomed
lakes and prairies are common.
Two fluvial terraces observed along a highly dissected Pleistocene
stream system in the vicinity of the town of Alachua and along Hog-
town Creek near Gainesville, together with high caverns and solution
features, indicate three former significant stands of the Pleistocene
piezometric surface in the Gainesville area at greater than 125 feet,
85 to 95 feet, and 75 feet. These are respectively correlated to 90 to
100 feet, 50 to 70 feet, and 18 to 25 feet higher Pleistocene stands of
sea level.
Three megafaunal zones are recognizable in the Upper Eocene
Crystal River Formation. The Exputens ocalensis zone is found at
the surface in the southwestern portion of the county. Overlying this
zone is the Amusium ocalanum zone. The Spirulaea vernoni zone is
found in numerous residual silicified boulders along the eastern mar-
gin of the limestone plain. The Middle Miocene Hawthorne Forma-
tion is principally a phosphatic sandy clay with layers and lenses of
limestone and dolomitic limestone. Silicified coral heads of the genus
Siderastraea occur in an essentially north-south zone from Alachua
County north to Hamilton County and may represent a high-energy
zone in the Hawthorne Formation. The Middle Pliocene (Hem-
phillian) Alachua Formation is primarily a gray to bluish-gray
phosphatic clayey sand or sandy clay which weathers to a reddish
color and contains plates and boulders of hard-rock phosphate.
Extending across Alachua County from Orange Lake northwest-
ward to the Santa Fe River sink is an extensively fractured zone
along which considerable ground-water solution has occurred. North-
west and northeast trending fracture sets were found to be dominant
in both the Crystal River and Hawthorne Formations. Episodes of
uplift and erosion occurred in the Middle to Late Oligocene and in
the Late Miocene to Early Pliocene.



Alachua County, having a land area of 892 square miles, lies in
the north central part of peninsular Florida (Figure 1). Elevations in
the western part of the county range from approximately 25 feet
above sea level in the northwestern corner along the Santa Fe River
to over 195 feet in the area northwest of Gainesville. The entire
county is in the Coastal Plain Province (Fenneman, 1938) and is
underlain by limestones of the Ocala Group of Late Eocene age.


This project was initiated in order to study the geology of the
western part of Alachua County in detail and to produce a geologic
map of the area. Both Levy County (Vernon, 1951) and Gilchrist
County (Puri et al., 1967) have been mapped in detail. This study
is an extension of those previous investigations. Numerous outcrops
in limestone quarries, abandoned phosphate mines, stream beds,
roadcuts, caves, and sinkholes were studied. Well records on file at
the Florida Bureau of Geology at Tallahassee were consulted and
utilized for subsurface control. Well cores obtained from the Florida
Highway Department and stored at the Florida State Museum in
Gainesville were examined. Of invaluable aid in the identification
of invertebrate fossils from Florida was the excellent collection at
the Florida State Museum, which was freely consulted throughout
the research.


Topographic maps of the western portion of Alachua County
(Figure 2) were the primary base maps used in the field work. Also
extremely useful in the field investigations were soil survey maps,
the general highway map, and photo-mosaics of Alachua County. A
list of the important maps covering Alachua County is given below.
1. General Highway Map of Alachua County. 1964, revised Oct.,
1970. Scale 1 inch = 2 miles (printed). (Also, 1 inch per mile in
blueprint). Issued by the State of Florida Department of Trans-
2. Soil survey maps of Alachua County. 1954. Scale 1:48,000. Pre-
pared by the U. S. Department of Agriculture Soil Conservation


10 0 10 20

*',0 C

Figure 1. Location of Study Area in Alachua County, Florida.


0 5
IScae in
Scale in miles

Figure 2. Topographic Maps, Western Alachua County. 7.5 Minute Series.




Service in cooperation with the University of Florida Agricultural
Experiment Station.
3. Air Photo-Mosaic Index. U. S. Department of Agriculture. Alach-
ua County. 1938 20 sheets, scale 1" = 2640'. 1949 4 sheets,
scale 1:20,000. 1961 4 sheets, scale 1:20,000. 1969 6 sheets,
scale 1:20,000.
4. Topographic maps of Florida. Issued by the U. S. Geological Sur-
The following 7.5 minute series quadrangles (scale 1 inch = 2000
feet) cover the western part of Alachua County (Figure 2).
Alachua sheet (1966)
Archer sheet (1968)
Arredondo sheet (1966)
Bronson NE sheet (1955)
Brooker sheet (1966)
Flemington sheet (1969)
Gainesville East sheet (1966)
Gainesville West sheet (1966)
High Springs sheet (1962)
High Springs SW sheet (1969)
Micanopy sheet (1966)
Mikesville sheet (1962)
Monteocha sheet (1966)
Newberry sheet (1968)
Newberry SW sheet (1968)
Waters Lake sheet (1968)
Williston sheet (1969)
Worthington Springs sheet (1966)


The earliest report specifically to mention the geology of Alachua
County was by Pierce (1825). He visited several sites in the county
including the rise and sink of the Santa Fe River, the Indian village
of San Felases, and Alachua Sink. Concerning the latter location,
he wrote:
In a section of the hilly district of East Florida called Alachua, I
visited a sink filled with water, covering an acre. It is the outlet of a
mill-stream that winds through a handsome prairie, and plunging into
the rocky basin takes a subterranean course ledges of calcareous and
siliceous shell rock formed the banks of the pool. Rocks in situ and de-
tached, enclosing in a white siliceous matrix, siliceous petrifactions of


marine shells were frequently noted in this vicinity. This mineral gives
fire copiously with steel, and no effervescence is produced by acids
applied to a recent fracture, and on minute division it appears entirely
siliceous. (Pierce, 1825, p. 125)
In addition to the common chert boulders found in this area, he
observed the underlying limestone around the margins of Paynes
Compact light colored limestone, resembling the predominant rock of
Cuba, is found on the western border of the great Alachua savanna,
forming the nucleus of a considerable eminence. The rock embraces
surpulites, pectinites and various bivalves, observed in northern secon-
dary calcareous rocks. (Pierce, 1825, p. 126)
Smith (1881) examined the limestone in the vicinity of Gaines-
ville while collecting data on cotton production for the tenth census.
He correlated this rock with the Vicksburg Limestone (which he con-
sidered to be Late Eocene in age) of Alabama and applied the name
Orbitoides Limestone to it. Phosphate was discovered in Florida by
C. A. Simmons in 1879 (Olson, 1972) near the town of Hawthorne in
eastern Alachua County. Johnson (1885) described the location of
some phosphate deposits, presented an early structural cross section
through Gainesville, and described (Johnson, 1888) the Waldo For-
mation (equivalent to the Hawthorne Formation). He also discussed
the geology of the Gainesville area (Johnson, 1893). The first com-
prehensive report on the geology of Florida, including mention of
Alachua County, was by Dall and Harris (1892) in which the Ocala
Limestone, Hawthorne Formation, and Alachua Formation were
named and described.
Short summaries of the geology of Alachua County were included
in general reports on the geology of Florida by Matson and Clapp
(1909), Matson and Sanford (1913), Cook and Mossom (1929),
Cooke (1945), and Puri and Vernon (1964). Major publications on
the hard-rock phosphate deposits, including references to the county,
were Eldridge (1893), Sellards (1913), Matson (1915), and Espen-
shade and Spencer (1963). The most comprehensive work on Alachua
County geology has been done by E. C. Pirkle who discussed the
physiography of the area and its Miocene and younger sediments
(Pirkle, 1956a & b, 1957a & b, 1958; Pirkle, et al., 1965). A number
of unpublished master's theses have been prepared at the University
of Florida on various aspects of Alachua County geology including
McClellan (1962) on clay minerals from the Devil's Mill Hopper,
Skirvin (1962) on the underground course of the Santa Fe River,
Isphording (1963) who did a study of heavy minerals from the
Devil's Mill Hopper, Mitchell (1965) on the carbonate rocks from


the same locality, Teleki (1966) who studied the sediments of the
Alachua Formation, Vormelker (1966) on the geology of the High
Springs quadrangle, Girard (1968) on the geology of the Gainesville
West quadrangle, and Marcus (1971) who studied rejuvenation fea-
tures along Hogtown Creek near Gainesville.


The topography of the western part of Alachua County consists
basically of a nearly flat plain underlain by the limestone of the
Crystal River Formation, mantled by thin sandy soils and residual
outliers of the Hawthorne Formation, and bordered on the east by a
subdued westward-facing escarpment and an upland plateau com-
posed of the less soluble Hawthorne sediments. Sinks, caves, and
typical karst topography occur in the plain, the marginal escarpment,
and less commonly on the plateau. In the southern part of the county,
in the limestone plain, the surface of the limestone coincides with
the ground-water level, and large flat-bottomed lakes occur.
The primary geologic processes controlling the topographic ex-
pression of landforms in this area are: stream erosion and sheetwash
along slopes in the marginal zone, ground-water solution in both the
Hawthorne and Crystal River formations, and modification by both
higher and lower stands of sea level during the Pleistocene Epoch.
The upland plateau originally extended completely across the
county, both south and west. Retreat of the erosional escarpment has
exposed the underlying limestone sediments, which were reduced to
their present level through the action of solution and modified by
Pleistocene higher sea level stands. Residual remnants of plateau
sediments are found in all areas of the limestone plain and the
dissected plateau continues south of the county.
Several authors have proposed the division of north central
peninsular Florida, including Alachua County, into physiographic
units: Johnson (1888), Sellards (1912), Matson and Sanford (1913),
Fenneman (1938), Cooke (1939, 1945), Vernon (1951), Pirkle
(1956a), White (1958, 1970), and Puri and Vernon (1964). The
delineation of western Alachua County used here (Figure 3) is
somewhat modified after White (1970). The following units were ob-
served in the area and are discussed below:
Northern Highlands Plateau
Northern Highlands Marginal Zone
Fairfield Hills


R 17 E

0Q 5
-i Scale in miles

R 17 E

Figure 3. Physiographic Zones, Western Alachua County.

R 18 E


R 20 E

R 20 E

R 18 E

R 19 E


Western Valley (Newberry Limestone Plain)
Alachua Lake Cross Valley
Brooksville Ridge
Brooksville Ridge Marginal Zone


The Northern Highlands Plateau is a high flat area of very low
relief that ranges in elevation from a maximum of just under 200
feet along its western margin to 145 to 150 feet along the eastern
margin of the area covered in this report. The elevation is generally
about 160 to 170 feet above mean sea level. The plateau is well
illustrated by an east to west elevation profile along the boundary
of Township 8 and 9 south (profile 1, Figure 4) and by a southwest
to northeast elevation profile drawn along a line from Watermellon
Pond through the Devil's Mill Hopper (profile 2, Figure 4). This
gradual but persistent elevation trend is probably due to the effect
of some continued post-depositional uplift along the Ocala arch.
The western and southern boundary of the plateau (Figure 3) is
taken as the point at which headward eroding streams have begun
dissection of the area of low relief. This dissected zone is the North-,
ern Highlands Marginal Zone. The plateau extends east from Gaines-
ville and is a continuous highland north into Georgia.
In this area the upper unit of the Ocala Group, the Crystal River
Formation, dips gently to the east and northeast and lies at a depth
usually greater than 100 to 150 feet below the surface. The Haw-
thorne Formation, consisting of a thick sequence of clays, clayey
sands and some carbonates, overlies the Crystal River Formation and
acts as an efficient aquiclude causing ground water in the primary
aquifer (the Ocala Group) to be under artesian conditions and
supporting a high secondary aquifer under water-table conditions.
Capping the Hawthorne Formation is a sequence of sands and clayey
sands, generally 0- 30 feet thick, at the land surface.
The most characteristic features of the plateau are the numerous
cypress hammocks and poorly drained swampy areas. These fea-.
tures (for example, Buck Bay north of Gainesville) are the result
of a high secondary aquifer supported by the generally impermeable
Hawthorne Formation. Drainage is generally to the north into the
Santa Fe River or to the east into Newnans Lake. Some streams,
fed by numerous seepage springs at the top. of the impermeable,
layers of the Hawthorne Formation, do head south and west and

Northern Highlands Plateau

Western Valley



R1 tIKR18E 5R-235

Elevation Profile 1.

SR-241 1-75 1Br'n e1

US-441 IN Iw Ur .
Vertical Exaggeration: 106X

Highlands Marginal

Vertical Exaggeration: 106X


_1_1_~___ __ _______

p F E






-100 g


Elevation Profile 2.


flow underground in the marginal zone. The Santa Fe River, form-
ing the northern boundary of Alachua County, flows northwest
across the plateau. It and two principle tributaries, Monteocha
Creek and Rocky Creek, drain the northern part of the county.


Elevations in this zone range from a maximum of over 190 feet
in the east, adjoining the Northern Highlands Plateau, to between
75 and 95 feet in the west, depending on the elevation of the surface
of the limestone plain of the Western Valley. Relief in this area is
the greatest to be found in the county. This is illustrated by reference
to elevation profiles 1 and 2 (Figure 4). The reason for this greater
relief lies in the presence of several streams that are in the process
of cutting headward into the plateau. These streams invariably end
in swallow holes or sinks, either before or just after reaching the
limestone plain. Several abandoned stream valleys and several in-
stances of stream capture by the formation of sinkholes may be
seen in this zone.
The Northern Highlands Marginal Zone extends as a continuous
band in the western part of the county from south of Gainesville
northwest to the Santa Fe River (Figure 3). It ranges in width
from approximately 1.5 miles to over 7 miles. The eastern boundary
of the zone is near the headwaters of the various streams that are
present in the marginal zone, and the western boundary is generally
a prominent westward-facing scarp at the contact with the less re-
sistant limestone of the Western Valley.
Topographic relief in this zone is controlled by both the Haw-
thorne Formation and by the underlying Crystal River Formation.
Impermeable layers and lenses in the Hawthorne produce localized
perched water tables commonly seen as small ponds in sinkhole
basins. Near the contact with the plateau region, many streams
begin in small seepage springs at the top of the formation. Other
small springs result from the channeling of ground water by imperme-
able lenses within the unit. Examples of this type of spring are the
small springs around the sides of the Devil's Mill Hopper, Glenn
Springs in northeast Gainesville, and Boulware Springs southeast
of the city.
The Crystal River Formation is rarely exposed at the surface in
this zone, but it nonetheless exerts a strong influence on the topog-
raphy. The numerous sinkholes and sinkhole ponds are the result


of the collapse or gradual subsidence into cavities in this unit. The
presence of several caves and swallow holes demonstrates the effect
of solution in the Crystal River Formation.


In the vicinity of Alachua, there is an excellent example of a
stream system dissected by the formation of sinkholes (Figure 6).
This stream system, draining a basin of over 70 square miles, is dis-
sected by more than 10 swallow holes which divert the water under-
ground. The system includes Townsend Branch, Mill Creek, the
streams flowing into Burnetts Lake, Turkey Creek, Blues Creek,
and Sanchez Prairie. Figure 6 shows the entire system, outlined by
the 75 and 100 foot contours, with the location of the various sinks.
Two former stages in the development of the current drainage pat-
tern may be inferred. The first stage consisted of two streams flowing
westward, one in Section 5, T. 7 S., R. 18 E., and the other in Section
22, T. 8 S., R. 18 E. These two streams were probably adjusted to an
Early Pleistocene base level, either a higher sea level stand at an
elevation of 90 to 95 feet, or to a higher ground-water level as a
result of a higher stand of the sea during the Pleistocene. The second
stage began with the formation of the sink in the SE/4, Section 9, T.
8 S., R. 18 E., which now forms the drain of Townsend Branch and
Mill Creek. Drainage from the southern section was captured by
this sink and the stream valley was lowered to under 75 feet. This
stage may have occurred during a lowered stand of sea level since
the valley cut by this stream is steep and constricted. Downcutting
rather than valley widening appears to have been dominant. At
present, almost three miles of this former stream channel have been
abandoned due to the formation of new sinks upstream at Burnetts
Lake and in the SW/4, Section 24, T. 8 S., R. 18 E. A cut and filled
portion of this former channel may be seen in a roadcut on US-441
in the SE/4, Section 14, T. 8 S., R. 18 E.
In the area southeast of Alachua (the southern part of this drain-
age system), a different type of solution feature has developed.
Sanchez Prairie is a fairly large flatbottomed depression with its
floor below 90 feet whereas the surrounding highlands rise to over
175 feet above sea level. There are several sinks in this basin, one of
which drains Blues Creek, and another drains Turkey Creek. Turkey
Creek appears to have been captured from its former more northerly
course into the Alachua stream system by the formation of a sink

Brooksville Ridge Western valley Alachua Lake Cross valley Fairfield Hills


SR-24 Ri E SR-241 US-41 R18ER19E SR-121 R19EIR20E SR-329 1-75 R20E R21

Vertical Exaggeration: 106X

Figure 5. Elevation Profile 3.


L8 E I

R 18 E

Scale in miles

Present drainage pattern

0L Draina

R 19 E
outlined by 75 and 100 ft.

ge sink \ 1st Stage of Stream system.

S2nd Stage of Stream system.

Figure 6. Alachua Stream System.


within the Sanchez Prairie basin. This basin was considered by
Sellards (1910b) to be in an early stage in the development of a
large flat-bottomed basin similar to those found in the Alachua Lake
Cross Valley, such as Kanapaha and Paynes Prairies. Stubbs (1940)
concurred that the basin was formed by the solution of the underly-
ing limestone and observed that, because of the absence of muck soils,
the basin probably had continuous underground drainage. However,
White (1958, p. 66), in a discussion of Sanchez, Kanapaha, and Hog-
town prairies, states that they "... give every evidence of being ex-
tinct lakes drained by a lowered water table, or a lowered piezometric
Sanchez Prairie is approximately 40 feet higher than Kanapaha
and Hogtown prairies and appears to have been a part of the Alachua
stream system. Its origin was probably caused by the development-
and expansion of multiple drainage sinks within the basin.

The Fairfield Hills form a highland area similar in many respects
to the marginal zone of the Northern Highlands. Elevations in
Alachua County range from a maximum of over 160 feet to a mini-
mum of 60 to 75 feet at the margins adjoining the Alachua Lake
Cross Valley and the Western Valley. Maximum elevations for the
Fairfield Hills occur, however, in northern Marion County and range
to more than 200 feet. This highland is illustrated by an east. to west
elevation profile along the southern boundary of Alachua County
(Figure 5, profile 3).
Relief and topography in this area are similar to that found in
the Northern Highlands Marginal Zone. The Fairfield Hills appear
to be a dissected remnant of a formerly continuous highland that
extended south through the central part of Florida and north to
connect with the Northern Highlands.
Only the northern tip of the Fairfield Hills extends into the
southern portion of Alachua County. They extend south approxi-
mately 20 miles and attain a maximum east-west width of about 15
miles (White, 1970). In Alachua County they are bounded by the
Alachua Lake Cross Valley to the north and by the limestone plain
of the Western Valley on the west. Two small outliers of the hills
occur in Alachua County. A small north-south ridge that attains a
maximum elevation of 110 feet occurs just west of Levy Lake, and a
larger hill with a maximum elevation of 115 feet is bounded by Levy
Lake, Paynes Prairie, and Lake Wauberg.


The geology of the Fairfield Hills is directly comparable to the
Northern Highlands Marginal Zone. The impermeable beds and
clayey lenses of the Hawthorne Formation are locally more than 100
feet thick and overlie the cavernous limestone of the Crystal River
Formation. Perched swamps and sinkhole ponds are common. Streams
that are dissecting the highland by headward erosion flow toward
the limestone plain and the large flat-bottomed lakes of the Alachua
Lake Cross Valley and eventually are diverted underground. These
similar geologic conditions, physiographic features, and maximum
elevations support the conclusion that the Fairfield Hills and the
Northern Highlands once formed a continuous highland across
Alachua County and south into central peninsular Florida.


The Western Valley is a subdued limestone plain composed of
the Crystal River Formation overlain by a thin or variable soil cover
and occasional residual hills composed of sediments of the Hawthorne
Average elevations on the limestone plain range from a high of
just over 100 feet down to about 60 to 65 feet with most of the area
being between 70 and 80 feet above sea level. Extremes of over 125
feet occur on several outlying erosional remnants of the highlands
plateau sediments and low elevations of under 30 feet occur in the--
northern part of the county in sinkholes near the Santa Fe River.
The generally flat and level nature of the Western Valley is illustrated
by elevation profiles 1 and 2 (Figure 4) and profile 3 (Figure 5).
Sinkholes, quarries, and low hills composed of erosional remnants
of the Northern Highlands provide the greatest topographic relief
in the area.
The Western Valley extends in a continuous band north to south
in the western part of Alachua County. It ranges from a minimum
of 5 miles to over 10 miles wide with an average width of 6 to 7 miles.
Boundaries of the limestone plain of the Western Valley on the west
are the Brooksville Ridge and the Brooksville Ridge Marginal Zone,
and on the east are the erosional scarp of the Northern Highlands
Marginal Zone and the lower lands of the Alachua Lake Cross Valley
(Figure 3). The limestone plain extends beyond the county, both to
the north and to the south. White (1970) named the High Springs
Gap for the lowlands through which the Santa Fe River exits the
county at the northern end of the limestone plain. The Williston


Limestone Plain was used by Vernon (1951) in his discussion of the
southern extension of the Western Valley into Levy County.
The Western Valley is underlain by the upper unit of the Ocala
Group, the Crystal River Formation. The eroded upper surface of
this formation forms an essentially level karst plain. Numerous ter-
restrial vertebrate fossil deposits preserved in sinkholes formed in the
Crystal River Formation indicate that it has undergone karstification
periodically since the Late Oligocene. Overlying this surface is a
relatively thin layer of sand and soil cover including common residual
boulders of silicified limestone. These boulders range in size from 1
to 15 feet in diameter and are encountered in all areas of the plain.
Residual sediments occur most frequently as sinkhole fillings and
tend to mask the great irregularities of the limestone surface.
Numerous low hills and slight ridges are composed of Hawthorne
sediments. These erosional remnants have been dissected and com-
pletely isolated from the main body of the formation by retreat of
the escarpment of the Northern Highlands Marginal Zone. The
presence of these isolated remnants indicates that the Northern
Highlands Plateau, underlain by the Hawthorne Formation, once
completely covered the Western Valley.
The essentially level surface of the limestone plain has been con-
sidered by several authors to be a marine terrace. Others have con-
sidered it to be the result of a karst cycle of erosion. Evidence exists
that both marine planation and modification by higher and lower
than present ground-water levels have occurred during the Pleistocene,
but the relative importance of the two processes is difficult to assess.
Dominating the landscape of the Western Valley are innumerable
sinkholes that divert all runoff underground and are the cause of
the lack of surface streams. The Santa Fe River does flow across
the limestone plain in northern Alachua County, although even it is
diverted underground. The sinks often occur in a linear series along
two principle trends, northwest to southeast and northeast to south-
west, with some suggestion of a faint north-south and east-west
lineation. This linearity reflects control of solution by jointing in
the limestone of the Crystal River Formation. Many authors (Lip-
chinsky. 1963; Davis, 1930: Stubbs, 1940; Bretz, 1942; Jordan, 1950;
Stringfield and LeGrand, 1966: and Brooks, 1967) have discussed
speleogenesis and various aspects of the development of karst fea-
tures. It has been shown by them that solution and speleogenesis
may occur not only in the upper phreatic zone but also at depth,
under artesian conditions, in both the limestone plain and beneath
the highlands plateau.


Most of the sinks in western Alachua County are the result of
slumpage of material into a solution cavity, though in some instances
it may be demonstrated that collapse of a portion of the ceiling of an
underground cavity was the causative factor in the formation of a
surficial sink (Figure 7). The surficial expression of Deadmans Cave
northwest of Gainesville is a shallow, steep-sided, funnel-shaped sink
with an opening in the bottom of the depression. This opening was
caused by collapse of a portion of the ceiling of a large room with a
vertical dimension of greater than 55 feet. This type of sink, however,
is rare in the limestone plain of Alachua County.

Figure 7. Typical sink hole resulting from collapse of a solution cavity (SW corner,
NW 1/4, Section 10, T. 8 S., R. 17 E.).
Over 100 caves are known in Alachua County, most of which occur
in the limestone plain. Most are very short with an average length
of less than 500 feet of passageway, large enough for one person. A
few are more extensive, with one cave (Warrens Cave near Alachua)
having a mapped length of over 3 and % miles, most of which is tight
crawlway. Speleothems, so common in caves in other parts of the
country, are extremely rare, and most of the caves in the county have
almost no secondary travertine deposits.
As seen on a map of the piezometric surface in Alachua County
(Figure 8), the Santa Fe River north and west of High Springs
serves as the primary area of discharge for the underground water
serves as the primary area of discharge for the underground water


0 5 10
Scale in miles

Contours represent the elevation of the 'piezometric surface in
feet above mean sea level in June, 1960. Cornuted from data
by Clark et al., 1964a.

Figure 8. Piezometric Surface, Alachua County.

of the county. The following named springs discharge into the Santa
Fe River: River Rise (SW corner, Sec. 14, T. 7 S., R. 17 E.), Hornsby
Spring (NE/4, SE/4, Sec. 27, T. 7 S., R. 17 E.), Darby Spring (SW/4,
NW/4, Sec. 27, T. 7 S., R. 17 E.), Columbia Spring (SW/4, NE/4,
Sec. 28, T. 7 S., R. 17 E), Poe Spring (NW/4, NE/4, Sec. 6, T. 8 S.,
R. 17 E.), and Lilly Spring (SE/4, SE/4, Sec. 36, T. 7 S., R. 16 E.).
Of these, only Poe Spring and River Rise may be considered major


Figure 9. Poe Springs. Water from Poe Springs empties into the Santa Fe River

springs. The average flow of Poe Spring (Figure 9) is 70.4 cubic
feet of water per second or 45 million gallons per day (Ferguson, et
al., 1947, p. 50). River Rise is the outlet not only for the water of the
Santa Fe River, which flows underground at O'Leno State Park ap-
proximately 3 miles to the northeast, but also for a significant amount
of added ground water. In addition to this discharge of ground water
into the river, it has been observed by several authors (Pirkle and
Brooks, 1959; Clarke, et al., 1964a) that the underground course of
the river serves as a point of recharge to the aquifer during flood


The Alachua Lake Cross Valley is a low area in the southern
part of Alachua County characterized by large flat-bottomed lakes
which are connected to the principal aquifer through one or more
drainage sinks located within their basins. Relief in this area is
typically small with elevations ranging from a high of rarely over
75 feet to a low determined by the piezometric surface which ranges


usually between 55 and 60 feet. A profile along the southern boundary
of Alachua County (profile 3, Figure 5) shows the southern section
of the lake region bordered by the limestone plain and the Fairfield
The northern and southern boundaries of the Alachua Lake Cross
Valley are well marked by the erosional scarp of the Northern High-
lands Marginal Zone and the highlands of the Fairfield Hills. The
valley extends eastward to connect with the Central Valley of White
(1970). A gradational boundary exists on the west as the Crystal
River Formation rises gradually to the level of the limestone plain
and the large lakes become less common. A similar but smaller area
contains Lake Kanapaha and Hogtown Prairie but is separated from
the Alachua Lake Cross Valley by a higher ridge about 1.5 to 2 miles
wide composed of the limestone of the Crystal River Formation and
the clays and sands of the Hawthorne Formation. The boundaries of
the Alachua Lake Cross Valley in the western part of Alachua
County are shown in Figure 3.
Underlying the lake region is the eroded surface of the Crystal
River Formation. Occasional low residual remnants of the Hawthorne
Formation and low ridges of limestone separate the various lakes
and basins of the region. Levy Lake and Paynes Prairie occupy the
largest of these basins. Levy Lake drains to the west through a series
of small ponds into Kanapaha Prairie and water in Paynes Prairie
drains into Alachua Sink (SW/4, Sec. 22, T. 10 S., R. 20 E.).
In the last part of the 19th century, Paynes Prairie attracted
much attention due to the formation in this basin of Alachua Lake.
Early reports (Pierce, 1825) indicate the basin as being a dry savanna
with drainage being diverted underground at Alachua Sink. Later
records (Smith, 1881; Dall and Harris, 1892; Johnson, 1893) indi-
cate that from 1868 through 1878 the basin periodically fluctuated
between a lake and marshland depending on precipitation and a
gradually diminished carrying capacity of the underground drainage
conduits. From 1878 through 1891 the basin was continuously oc-
cupied by water and a small freight-carrying steamer operated on the
lake (Sellards, 1910b, p. 65). In 1891 the drainage sink gradually re-
opened and the lake reverted to its former state of marshy prairie
flatlands. More recently, canals were constructed and pumps installed
to prevent the filling of the basin (Pirkle, 1956a).
The origin of the large shallow lake basins and marshy savannas
of the Alachua Lake Cross Valley has been discussed by several
authors (Sellards, 1908, 1910b, 1912; Stubbs, 1940; Pirkle, 1956a;
Pirkle and Brooks, 1959; and Brooks, 1967). Agreement is general


that these basins are the result of solution, and Pirkle (1956a, p.
180) and Pirkle and Brooks (1959) observed that the piezometric
surface is serving as a temporary base level to which high areas are
being eroded and low areas filled.
In addition to the basins that have floors currently below the
piezometric surface and contain water, there are several large dry
basins to the west of the lake area in the limestone plain at a slightly
higher elevation. These basins are similar in many respects to the
basins of Levy Lake and Paynes Prairie. A slight rise in the Late
Pleistocene piezometric surface would fill these basins in a manner
similar to the current lake basins. The two most well-defined of
these basins are seen on the Arredondo and Archer 7.5 minute quad-
rangles. One is partially occupied by Kanapaha Prairie and the
other is centered northeast of Archer in the vicinity of Sections 34
and 35, T. 10 S., R. 18 E.


Only a small part of the northern tip of the Brooksville Ridge is
present in the extreme southwest corer of Alachua County. The
ridge extends to the south of the county approximately 90 miles and
varies from 4 to 15 miles in width (White, 1970).
Relief is relatively great with elevations in the Alachua County
portion of the ridge varying from a high of about 135 feet to a low
of 55 feet in some of the smaller ponds. The ridge in the county is
bounded on the east by the limestone plain (Figure 3). West and
southwest of Archer, the ridge is a distinct highland and the sand
dunes begin rather abruptly. Northwest of Archer, the limestone
plain forms a westward-facing, well-dissected and subdued scarp,
and the sand dunes of the Brooksville Ridge are lower in elevation.
Here, the ridge is marked not by an increase in elevation but by a
distinctive topography of stabilized sand dunes and ridges accentu-
ated by joint-controlled solution of the underlying limestone.
The limestone of the Crystal River Formation in this area forms
a highly uneven and solution-riddled surface. Overlying this unit is
the highly phosphatic Alachua Formation and a thick mantle of
Pleistocene sand. The result of this geological configuration is that
all drainage is underground, and solution plays a dominant role in
shaping the topography. Many small sinkholes and sinkhole ponds
are found here in addition to the relatively large Watermellon,
Horseshoe, and Half Moon Ponds.


As observed by Pirkle (1956a), the sand is probably aeolian and
was associated with a Pleistocene sea located not far to the west of
the county. The dominant northeast to southwest trend of the sand
ridges has probably been accentuated by joint-controlled solution in
the limestone of the Crystal River Formation.


The Brooksville Ridge Marginal Zone is essentially an extension
of the limestone plain of the Western Valley. It is similar also to the
Brooksville Ridge except the thick sand cover is generally absent.
Elevations average around 80 to 85 feet and relief is provided
mainly by numerous sinkholes, caves, and abandoned hard-rock
phosphate mines. The marginal zone occurs along the western bound-
ary of the county between the Western Valley and the Brooksville
Underlying the Brooksville Ridge Marginal Zone is the uneven
surface of the Crystal River Formation covered by phosphatic sedi-
ments of the Alachua Formation. A thin, variable cover of probably
Pleistocene sand covers the surface. Drainage is entirely subsurface
as in both the Brooksville Ridge and the Western Valley. Due to the
presence of rich hard-rock phosphate deposits in the Alachua Forma-
tion and the thin sand cover, this area was extensively exploited
by open pit phosphate mining around the turn of the century.


Landforms in the western part of Alachua County, which are
genetically associated with higher stands of sea level, fall readily into
two categories: those directly formed or effected by eustatic sea level
fluctuations and those indirectly formed or effected. The directly ef-
fected areas are the high flatlands of the Northern Highlands Plateau,
the lower limestone plain of the Western Valley and the relict sand
dunes of the Brooksville Ridge. Indirectly effected landforms are a
result primarily of fluctuations in the piezometric surface in the
limestones of the Ocala Group in response to sea level fluctuations.
These features include aspects of fluvial terraces in the Northern
Highlands Marginal Zone, lowering of the general level of the lime-
stone plain, a more extensive lowering of the plain in the lake region
of the Alachua Lake Cross Valley, and sinkhole and cavern develop-
ment on the limestone plain.


Many authors have discussed and attempted a correlation of
marine terraces and relict shoreline features including Matson and
Sanford (1913), Cooke (1931, 1939, 1945), Flint (1940, 1971),
MacNeil (1950), Alt and Brooks (1965), and Brooks (1966). A
complete review of this material will not be discussed in this report
except as required to supplement the stratigraphic evidence found
in the western part of Alachua County.
The high terrace of the Northern Highlands Plateau has been
referred to by several authors as the Okefenokee Terrace. The maxi-
mum elevation of the shoreline of the Okefenokee sea is given variously
as between 150 and 170 feet (Cooke, 1931, 1939; MacNeil, 1950), and
the age is correlated as Pleistocene (Yarmouth Interglacial). Alt and
Brooks (1965), in a preliminary report, indicated that the plateau
was part of a terrace associated with a Late Miocene stand of sea
level at 215 to 250 feet. Brooks (1966, p. 41) stated, "The Okefenokee
surface is an erosional to depositional fluviatile plain graded to the
Late Pliocene stand of sea level." Evidence to date precisely the
Okefenokee surface is generally lacking in the western part of
Alachua County. The youngest beds underlying this surface in the
region are scattered remnants of an Upper Miocene shell marl such
as seen at Brooks Sink in Bradford County and isolated, probably
fluviatile, occurrences of Middle Pliocene terrestrial vertebrates from
several localities northwest of Gainesville. Therefore, a Late Pliocene
age is considered probable.
The nearly flat limestone plain of the Western Valley has long
been considered as a surface of marine planation. Matson and San-
ford (1913) named it the Newberry Terrace and correlated it to a
70 to 100 foot stand of sea level. Cooke (1931) used the name Wicomi-
co Terrace and later (Cooke, 1939) correlated this 100 foot stand to
the Sanagamon Interglacial. Flint (1940) noted that the Surry Scarp
in Maryland was probably caused by the 100 foot stand. These
correlations were held by several subsequent workers (Cooke, 1945;
MacNeil, 1950; Vernon, 1951; Puri and Vernon, 1964). Alt and
Brooks (1965) indicated an earlier (Pliocene) age, later revised
(Brooks, 1966) to Early Pleistocene (Aftonian Interglacial, Brooks,
1967). That at least part of the limestone plain was covered by a
Pleistocene 90 to 100 foot sea level stand is indicated by the rare oc-
currence in Alachua County of the Pleistocene marine pelecypod,
Chione cancellata (Linnd). One such instance was from a core boring
for the foundation of a high school east of High Springs (FSM Acc.
No. 534). Another, more significant site where Chione cancellata has
been found is the vertebrate locality, Haile XV-A, northeast of New-


berry. The vertebrate fauna at this locality is Early Pleistocene in
age (D. Webb, personal communication). Therefore, an Early Pleisto-
cene planation by a 90 to 100 foot stand of sea level of at least part of
the Western Valley is considered probable.
It is recognized that during the 90 to 100 foot stand of sea level a
significant volume of sediment may have been removed from the
Hawthorne Formation overlying the limestone plain. The subdued
scarp of the Northern Highlands Marginal Zone does not appear to
have been caused by wave action but by differential solution of the
underlying limestone accompanied by the action of numerous small
streams eroding into the semi-consolidated sediments of the Haw-
thorne Formation. Retreat of the escarpment, accompanied by ex-
tensive subaerial erosion and karstification, has removed those fea-
tures that this shoreline may have had in common with modern
beaches. Therefore, an attempt to map the position of the shoreline
during this stand of sea level (as has been done by several workers
by tracing topographic contours) would be extremely difficult if not
impossible. Likewise, the existence of former sea level stands of
between 100 and 150 feet would be similarly difficult to justify based
on evidence in Alachua County.
The surficial unit of the Brooksville Ridge is a thick layer of
Pleistocene sand. Its distribution in Alachua County is shown in,
Figure 3. As noted earlier, the characteristic topographic feature is
that of stabilized sand dunes. Pirkle (1956a) observed that the sand
probably was aeolian, transported from the vicinity of a Pleistocene
sea to the west or southwest. Teleki (1966) demonstrated by variance
analysis that the sand was derived from the underlying Upper Mio-
cene and Pliocene sediments. Espenshade and Spencer (1963)
mapped the extent of the Pleistocene sand. Yon and Puri (1962) and
Puri et al. (1967) investigated the western boundary of the Brooks-
ville Ridge in Gilchrist County and correlated the sand ridge to a
70 to 75 foot stand of sea level which cut an escarpment along the
western margin of the ridge. White (1970) concurred that the western
margin is probably a marine terrace scarp and postulates that parts
of the scarp may have been occupied by more than one sea level
stand. No fossiliferous deposits have been found in this unit; there-
fore, since the sand appears to be associated with sea level stands
of between 70 and 75 feet, a Pleistocene age is accepted.
Several approximate former stands of the piezometric surface
may be postulated in the western part of Alachua County. A signifi-
cant stand of approximately 125 feet above current sea level would
be required for the formation of such high solution features as


Warrens and Deadmans Drop Caves. In both of these caves, the
contact between the Crystal River and Hawthorne formations is at an
elevation greater than 115 feet. Lipchinsky (1963, p. 56) concluded
that these caves were formed ". .. in the phreatic zone out of lime-
stone saturated with water under artesian conditions." Assuming
that there was an inland area of recharge to the aquifer such as exists
today in western Putnam County, and that the scarp of the Haw-
thorne Formation extended farther west than at present, a 125 foot
stand of the piezometric surface may be correlated to the Early
Pleistocene (Aftonian) stand of sea level at 90 to 100 feet.
Pirkle and Brooks (1959, p. 307) stated, "The karst surface in
western Alachua County has been reduced to a limestone plain co-
inciding to a former stand of the water table 80 to 90 feet above the
present level of the sea." Marcus (1971), in a study of rejuvenation
features on Hogtown Creek west of Gainesville, concluded that the
stream was originally graded to a base level of 90 feet. This is the
same elevation to which the earliest streams in the Alachua stream
system were graded. Marcus concluded that the base level was rep-
resented by the 90 foot stand of sea level. An equally valid interpre-
tation, and the one preferred here, is that the local base level for
both stream systems was a 90 foot stand in the piezometric surface.
This stand could be correlated to a Pleistocene sea level stand of
approximately 70 feet as has been postulated for the toe of the
scarp on the western margin of the Brooksville Ridge.
Several abandoned springheads occur in the vicinity of High
Springs. These abandoned valleys were first observed by Stubbs
(1940), and the largest of these was investigated by Edwards (1948).
In the latter report, it was observed that a rise in the piezometric
surface to an elevation of greater than 42 feet above sea level would
be required for the springhead to commence flowage. This higher
ground-water level was correlated to the Pamlico Terrace (25 feet
above current mean sea level, Cooke, 1931). The current gradient of
the piezometric surface (Figure 8) ranges from approximately 55 to
60 feet above sea level in the southern part of the limestone plain
to 25 feet above sea level along the Santa Fe River in the vicinity of
these abandoned valleys. If this gradient is projected to a base level
of 42 feet at the north, at a point of discharge, the late Pleistocene
piezometric surface in the vicinity of Gainesville would have been
approximately 75 to 80 feet (the average surface elevation of the
southern part of the Western Valley in Alachua County) and would
account for the general lack of speleothems in the caves of the
limestone plain and for the rejuvenation of youthful features on a


mature karst plain. At present, the piezometric surface stands be-
tween 50 and 60 feet above sea level beneath the southern part of the
limestone plain in Alachua County and the karst topography is being
rejuvenated. In the lake region, the water table is acting as a local
base level and causing the development of the large flat-bottomed
lakes (Pirkle and Brooks, 1959).
Lower than present stands of sea level occurred during Pleistocene
glaciations with their attendant lowering of the piezometric surface
to below its present level. Analysis of these now submerged features
was beyond the scope of the present investigations.


The Peninsular arch forms the axis of the Florida peninsula and
is the dominant subsurface feature in the State (Applin, 1951). It
extends from southeastern Georgia to the vicinity of Lake Okeecho-
bee. In its southern portion the trend is almost north-south but the
northern section is higher and trends more to the northwest. The
crest passes beneath Alachua County and is highest just north of the
county in Union and Bradford counties (Chen, 1965). The arch was
a topographic high during most of the Cretaceous, with Upper
Cretaceous sediments deposited over it (Applin, 1951). It formed a
relatively stable base upon which sediments through Eocene age
were deposited, interrupted only by intermittent land emergence
and shoal-water conditions.
A younger structural feature developed in the Tertiary. This
feature dominates the surficial expression of rocks in west-central
peninsular Florida. It was named the Ocala uplift by Hopkins in a
U. S. Geological Survey press release (Vernon, 1951). The exposed
area of the uplift is approximately 230 miles long and 70 miles wide
and generally trends in a northwest to southeast direction. It is not
a simple double-plunging anticline but consists of at least two roughly
parallel low folds (Vernon, 1951) with other low folds intersecting
it at various angles. The structurally highest portion of the uplift is
in Levy County and is marked by the surface occurrence of the Avon
Park Formation (Late Middle Eocene). The crest of the uplift is
extensively fractured with high-angle faults tending to flatten its
crest and increase its cross section (Puri and Vernon, 1964). The
western part of Alachua County is on the northeastern flank of the
Ocala uplift. The sediments of the Crystal River Formation and the
overlying Hawthorne Formation dip gently to the northeast. This dip


is not measurable in outcrops, but well data indicate a dip of less than
one degree (95 feet per mile) to the northeast.
Vernon (1951, p. 47-52) was the first to recognize faulting in
Florida and produced a map demonstrating an extensive statewide
fracture pattern. This fracture pattern may be traced from county to
county on aerial photographs. Two trends are prominent. One is
from northwest to southeast and is essentially parallel to the axis
of the Ocala uplift, and the other is approximately at right angles
to it.
In western Alachua County, the Crystal River Formation is ex-
tensively fractured. The principle mode of expression of this fracture
pattern is the controlling influence it has had on ground-water solu-
tion within the unit. The linear occurrence of numerous sinkholes
and caves on the limestone plain attests to the effect of solution on
this fracture system. Brooks (1967) observed that higher-yield water
wells could be obtained by drilling along these fracture traces.
Several streams in Alachua County appear to be joint controlled.
The Santa Fe River along the northern boundary of the county is
an excellent example. There is nothing unusual about this stream
from its headwaters down to Worthington Springs. At this point,
the character of the river valley changes. The stream begins a series
of relatively straight reaches terminated by nearly right angle bends.
Several small tributaries in this area show this pattern. The Santa
Fe River west of Worthington Springs is believed to be reflecting
the joint pattern in the underlying Hawthorne and Crystal River


There is a striking lineation of karst solution features in Alachua
County that extends from Orange Lake in the south to the Santa Fe
River sink in the north in a direction N 40 W. This is a distance of
approximately 45 miles. This lineation only becomes obvious when
one plots the location of all the streams that go underground in the
county. Such a plotting reveals numerous sinking streams along
this trend, whereas only one stream crosses it (Figure 10). Several
other features also occur along the trend.
Orange Lake, on the southern boundary of the county, is typical
of the large flat-bottomed lakes common in the region. During very
dry periods the lake is drained by a large sink in its southeastern
end (Pirkle and Brooks, 1959). The linear nature of Orange Lake,

Scale in miles


* Drainage sink.

( Covered area.

extensively fractured zone.

Figure 10. Cross-County Fracture Zone.


approximately 6 miles long by 1.5 miles wide, is also concurrent
with this trend.
Alachua Sink, south of Gainesville, is the major drain for Paynes
Prairie. There is a large embankment along the northeastern .border
of Paynes Prairie that parallels the linear trend of solution features.
Lake Alice drains into (or drained into before control structures
were erected) a small sink located on the University of Florida
campus. It appears obvious from the topographic maps that Lake
Alice has, in fairly recent times, covered a much larger area and was
once a tributary to Hogtown Creek. It was captured and its surface
level drastically lowered by the opening of the sink. A small stream
tributary to Lake Alice was captured in 1971 by collapse of a
portion of its stream bed. The sink into which the stream flowed
was approximately 15 to 20 feet deep. The sinkhole intersected a cave
with over 900 feet of passageway, including a room over 20 feet
high. This sink has been subsequently filled by the university.
The Devil's Mill Hopper is a very large sink northwest of
Gainesville that is over 125 feet deep. It is the drain for one small
surface stream and several small springs that flow out of the Haw-
thorne Formation which forms its steep sides.
The Alachua stream system, previously discussed (Figure 6),
has been dissected by no less than 10 swallow holes. All of these lie
along this trend.
The largest sinking stream in this area is the Santa Fe River
sink at O'Leno State Park (Skirvin, 1962). As the Santa Fe River
flows off the Hawthorne plateau onto the limestone plain, the entire
river flows underground for a distance of approximately three miles.
The location of several of these sinks may be accounted for very
simply as the effect of solution on the Crystal River Formation as
these streams reach the western boundary of the impermeable Haw-
thorne Formation. However, there are also several sinks located east
of this contact, for example, the Devil's Mill Hopper and the sinks
in Sanchez Prairie. Also, the linear nature of Orange Lake, the scarp
on the northeast margin of Paynes Prairie, and the apparent joint
controlled portions of Hogtown Creek and the Alachua stream system
are not accounted for.
This linear trend of solution features is considered to be a direct
result of an extensively fractured zone both in the Crystal River and
the Hawthorne Formations. Preferential solution occurred along
this fractured zone in the Crystal River Formation. This was ac-
centuated by downward percolation of ground water along joints
and fractures in the Hawthorne Formation. The result of this pref-


erential solution is that streams flowing west across this fractilre
zone have been captured by sinks along it. The formation of linear
features such as the scarp at Paynes Prairie and the orientation of
Orange Lake, in addition to the control of several streams and the
location of such isolated features as Sanchez Prairie and the Devil's
Mill Hopper, is accounted for by this fracture zone.
Brooks (1966) observed that there may be some stratigraphic
displacement in the Gainesville area. Vernon (1951, p. 48) indicates
that in the statewide fracture system, the northwest to southeast
trending joints have a greater probability of being faults. Therefore,
in addition to the location of these features as a result of differential
solution, the possibility of control by faulting is not discounted.
Weakening of the impermeable beds in the Hawthorne Formation -
may be a result of this faulting. Faulting cannot be demonstrated
directly by outcrop observation. The displacement must therefore
be diffused over a width of at least one-half mile by the formation
of numerous small fractures and joints.


Direct outcrop measurement of the fracture pattern in the
homogenous limestone of the Crystal River Formation is impossible.
This pattern only appears as a controlling factor in the lineation and
orientation of solution features. As noted by several authors, it is
observable on a regional scale on air photographs. Most of the caves
in the western part of the county show control of solution by jointing.
Warrens Cave is the longest joint controlled solution feature in the
area. The fracture pattern shown on Figure 11 was taken from the
map of Warrens Cave produced by the Florida Speleological Society.
This diagram illustrates the obvious control of solution by the frac-
ture pattern in the limestone and is representative of this fracture
The Hawthorne Formation is also extensively fractured. Figure 12
shows the fracture pattern observed at one locality in this unit.
Jointing in the Hawthorne Formation may be observed at the Devil's
Mill Hopper and along the beds of several streams in the Gainesville
area. As seen in Figure 12, the fracture pattern in the Hawthorne
Formation is nearly identical to that in the underlying Crystal River
Formation. Primary fracture strikes are N 650 W, N 450 W, and
N 30 E, with secondary strike directions nearly north-south and
east-west. Vernon (1951, p. 47 52) presented an analysis of the


100 measurements, 10 degree increments
Source: unpublished 1966 map of Warrens Cave
prepared by the Florida Speleological

Figure 11. Fracture Pattern, Crystal River Formation.

Figure 12. Fracture Pattern, Hawthorne Formation.

200 measurements, 10 degree increments
Measured at a drainage pit, 0.7 miles
north of the 1-75 Fla-121 Interchange.


statewide fracture pattern. He considered these fractures "... to have
formed under a combination of tensional stresses over the anticlinal
Evidence from the western part of Alachua County indicates at
least two distinct episodes of uplift along the Ocala arch. The first
uplift occurred in the Late Oligocene through the Early Miocene.
That this area was land during this time is indicated by the presence
of several land vertebrate deposits of this age. Also, no Oligocene
Suwannee Limestone or Early Miocene Tampa Formation is present
in the southeastern section of the county. Silicified residual boulders
of the Suwannee Limestone are found in the northern part of the
county which indicates that this unit has been eroded from the area.
The Hawthorne Formation was deposited over this eroded surface.
The present cycle of erosion was initiated by a second episode of
uplift that occurred beginning probably in the Early Pliocene and
continuing sporadically into the Early Pleistocene. Numerous Middle
Pliocene and Pleistocene land vertebrate deposits attest to the pres-
ence of land during this time.


Surficial sedimentary deposits in the western part of Alachua
County range from the Upper Eocene Crystal River Formation to
Recent fluvial deposits and sinkhole fills. There are three extensive
formations in the area: the Crystal River Formation, Hawthorne
Formation, and the Alachua Formation. Residual remnants of Upper
Eocene, Oligocene, Middle and Upper Miocene, Pliocene, and Pleisto-
cene sediments are found in various parts of the county. A short
summary of the strata exposed at the surface is given in Figure 13.
The Crystal River Formation is the oldest unit exposed at the
surface in Alachua County. It is a white to cream-white granular
foraminiferal bioclastic limestone. The most abundant fossils are the
larger foraminifers, several species of echinoids, bryozoans, and
mollusks. This limestone has been extensively quarried for road con-
struction. The upper surface of the unit is an erosional unconformity
and silicified residual boulders of both the Crystal River Formation
and the Oligocene Suwannee Limestone are common. Early Miocene
marine sediments were not deposited in the county as indicated by
the presence of several land vertebrate sites of this age. Overlying the
Crystal River Formation in the eastern part of the county is the
Hawthorne Formation of probable Middle Miocene age. The Haw-







Primarily represented by
sinkhole deposits, flu':ial
terraces, and thin sand
Unconsolidated sand dunes of
the Brooksville Ridge.

Clean to clayey sand. Contains
reworked U. Miocene marine
and Pliocene land fossils.

Middle Alachua Gray to bluish-gray clayey
Pliocene Formation sand. Weathers red to
Contains hard-rock phosphate,
residual U. Eocene and Olig-
ocene boulders, and numerous
Hemphillian vertebrate de-
thru Residual Remnants
Middle Hawthorne Phosphatic clayey sand or
Miocene Formation sandy clay, lenses of dolo-
mite and limestone in places
with heavy concentrations of
fullers earth and phosphorite
Common silicified Ostrea
Lower Absent
Oligocene Suwannee Only as residual silicified
Limestone boulders, some poss. in
place in north end of county.
Rhyncholampus gouldii very



White to cream-white bioclas-
tic limestone.
Extremely fossiliferous with
larger forams and molluscs
especially abundant.
In this area, presence of
Lepidocyclina sp. is diag-

Figure 13. Geologic Formations in Western Alachua County.

I 1 I



thorne Formation is primarily a phosphatic clayey sand or phosphatic
sandy clay with interbedded lenses of dolomite and limestone. In
places there is a heavy concentration of fullers earth and phosphorite.
The most common fossils in the Hawthorne Formation are sharks
teeth, ray dental plates, and occasional bioherms of Ostrea normalis
Dall. In the northern part of the area, silicified heads of the colonial
coral Siderastrea sideria Ellis and Solander are also common. Re-
sidual, isolated remnants of Upper Miocene marine sediments are
found in various areas of the county. The Alachua Formation of
Middle Pliocene age is found as a continuous mappable unit along
the western boundary of the county. It is generally a gray to bluish-
gray clayey sand which weathers red to reddish-brown on exposureL
Residual silicified boulders of Late Eocene, Oligocene, and Miocene
age and very heavy localized concentrations of secondary hard-rock
phosphate are found in this unit. The Alachua Formation is generally
nonfossiliferous with the exception of localized concentrations of
Middle Pliocene land vertebrates. In the early part of this century,
the Alachua Formation was extensively mined for phosphate. The
deposits underlying the Okefenokee Terrace are composed of residual
Upper Miocene and Middle to Upper Pliocene marine and nonmarine
sediments. In the southwestern part of the county there are stabilized
sand dunes of probable Middle Pleistocene age. In various localities
throughout the county there are localized occurrences of Pleistocene
fossils. These sites include land vertebrates, marine and nonmarine
invertebrates. A short summary of the foregoing discussion is given
in Figures 13 and 14. Also illustrated on Figure 14 is an estimation
of the amount of time in which little or no sediments were deposited
in the western part of Alachua. County and an estimation of sedi-
mentary units which were deposited and subsequently eroded.
General discussions of the subsurface section beneath western
Alachua County are given by Applin and Applin (1944), Applin
(1951), and Puri and Vernon (1964).


The Crystal River Formation was defined as the upper unit of
the Ocala Group by Puri (1953, p. 130). The type locality is the
108 feet of limestone exposed in the Crystal River Rock Company
quarry, Section 6, T. 19 S., R. 18 E., Citrus County, Florida. A
section of the type locality is given by Puri (1957, p. 35).


Newberry Alachua Gainesville


In place sediments and probable

former extent.

P-robable erosion.

\ ~Probable non-deposition.

,c'c@ c Residual, silicified boulders.

O Ci Other residual remnants.
V VV Vertebrate deposits.

Figure 14. Generalized Area-Time Diagram, Western Alachua County.

Numerous authors have contributed to the current knowledge of
the stratigraphy and correlation of the limestone of the Ocala Group,
including Smith (1881), Johnson (1888), Dall and Harris (1892),
Dall (1903. in Dall, 1890-1903), Cooke (1915), Applin and Applin
(1944), Vernon (1951) and Puri (1957). The history of these lime-




stones is reviewed in reports by Cooke (1915 and 1945) and Puri


The most common lithology present in the Crystal River Forma-
tion is that of a white to cream, massively bedd6d, soft, granular,
bioclastic limestone. In places it is almost a coquina of large fora-
minifera or of the calcitic shells of Amusium ocalanum Dall or
Chlamys spillmani (Gabb). Layers of these fossils occasionally im-
part a prominent bedding to the rock. Locally the rock is well in-
durated with calcite cement and in other places is extremely granular
and soft. Chemical analyses of limestone from the pit of the Cummer
Lumber Company, 1.25 miles southwest of Newberry (now aban-
doned), indicate from 97.9 per cent to 98.5 per cent calcium carbonate
with minor impurities being principally iron, alumina, insolubles,
and magnesium carbonate (Mossom, 1925, p. 115-117). Analyses
from two pits southwest of Gainesville at Arredondo indicate from
96.1 per cent to 98.8 per cent pure calcium carbonate. The calcium
carbonate is present almost exclusively as the mineral calcite, the
slightly more soluble aragonite having been dissolved or replaced by
calcite. As a significant percentage of marine animals secrete an
aragonitic skeleton, the presence of numerous molds and a high
secondary porosity is thus explained. Those fossils best preserved
are those which originally secreted a calcitic shell, for example, the
echinoids and some pelecypods and foraminifers.
The thickest section of limestone exposed in the western part
of Alachua County is at the S. M. Wall quarry, SW/4, NE/4, Sec.
35, T. 9 S., R. 18 E., where 66 feet of the Crystal River Formation
is exposed.


Portions of the Crystal River Formation have been locally re-
placed by silica. Upon erosion, large boulders remain as residual
remnants of the reworked limestone. These boulders may attain a
size of more than 10 feet in diameter and are extremely variable in
color. They were formed by the in situ replacement of carbonate by
silica. Numerous fossils are preserved as casts, molds or by complete
replacement of the original shell material by silica. The state of
preservation of fossils ranges from almost perfect pseudomorphic


replication to complete obliteration of all organic remains. The outer
surface of these boulders is commonly weathered to varying thick-
nesses and is generally bleached to a white or light gray color, some-
times with a reddish limonitic stain. Those boulders that have been
exposed to weathering the longest sometimes show irregular exfolia-
tion plates.
Chert is commonly found along joints in the Crystal River For-
mation as seen in several caves in the western part of Alachua
County. This chert forms vertical walls and sometimes divides joint-
controlled cave passageways longitudinally. Horizontal layers and
plates of chert are commonly found at the contact between the
Crystal River and Hawthorne Formations. Both of these conditions
may be seen in Warrens Cave northwest of Gainesville where flat
chert plates form both portions of the ceiling and vertical partitions.
The chert appears to be more common on the surface or close to
the contact with the overlying Hawthorne Formation than at depth
within the limestone and is also more common in solution cavities
than disseminated randomly throughout the limestone. The above
observations suggest that the silica necessary to form the chert
boulders was provided by the Hawthorne Formation.
There are several processes that have occurred or are occurring
in the Hawthorne Formation that release silica in solution and
provide an available adequate source for silica replacement of car-
bonate rocks. One process that releases silica is the transformation of
montmorillonite to kaolinite during low temperature supergene weath-
ering (Altshuler et al., 1963). The weathering process was observed
by petrographic studies of samples from outcrops in Alachua County
by Assefa (1969, p. 74). Another process that releases silica is the
replacement of clay minerals by calcite and the replacement of detrital
quartz also by calcite. Carbonate samples from the Hawthorne For-
mation were studied petrographically by Mitchell (1965, p. 47) who
In all thin sections studied from the Devil's Mill Hopper, the plastic
grains and clay are replaced in varying degrees by calcite. The silica
released by this replacement process probably was the source of silica
required for the silicification of portions of unit 1 and the upper surface
of the Ocala Limestone.
Because there are no indications that sufficient silica was deposited
simultaneously with the limestone of the Crystal River Formation,
the formation of chert requires an external source for silica such as
the Hawthorne Formation. The presence of chert boulders at the
surface in the limestone plain is therefore an indication of not only


the former presence of a greater thickness of limestone than is present
today but also of the former presence of the Hawthorne Formation.
The occurrence of these boulders in all areas of the limestone plain
is another indication that the Hawthorne Formation once completely
covered Alachua County and has been subsequently removed by

The Crystal River Formation and the Ocala Group have a diverse
fauna, the limestone being composed principally of the detrital re-
mains of marine organisms. Prominent fossil groups represented are
the pelecypods, gastropods, echinoids, bryozoans, crustaceans, and
foraminifers. Many workers have studied the foraminifera of the
Ocala Group. Significant contributions, including descriptions of
new species, have been made by Cushman (1920, 1934), Vaughan
(1928), Cole (1938, 1941, 1942, 1944), Applin and Jordan (1945),
and Puri (1957). Foraminiferal zonations of the Ocala Group have
been presented by Gravell and Hanna (1938), Applin and Applin
(1944), Applin and Jordan (1945), and Puri (1957). Bryozoans are
numerous and varied in the Ocala Group. Canu and Bassler (1920)
described over 80 species from Ocala, Alachua, and Marianna. Cheet-
ham (1957, 1963) proposed a bryozoan zonation of the Ocala Group.
The echinoids are one of the most common and best preserved
fossils in the Ocala Group. Detailed discussions of Ocala echinoids
are given by Clark and Twitchell (1915), Fischer (1951), and Cooke
(1959). More than 40 species of echinoids have been described from
the Ocala Group. Other fossil groups remain largely unstudied, al-
though Harris (1951) gave a preliminary listing of Ocala pelecypods,
including the species described by Dall (1890-1903), and Puri (1957)
has described ostracodes from the Ocala Group. Richards and Palmer
(1953) have described some of the mollusks from the Inglis Forma-
tion, and Harris and Palmer (1946, 1947) have described the Jack-
sonian Eocene molluscan fauna of the Mississippi embayment, which
included several species that are also found in the stratigraphically
equivalent Ocala Group.
McCullough (1969) found that a megafossil zonation was possible
in the Crystal River Formation of peninsular Florida. He traced the
surficial expression of the Amusium ocalanum zone, and Hoganson
(1972) traced the Spirulaea vernoni zone. The latter zone is the
equivalent of Puri's (1957) Asterocyclina-Spirolaea [sic] vernoni
faunizone in peninsular Florida. These two zones were found to be

Puri (1957)
(Foraminiferal zonation)

Cheetham (1963)
(Bryozoan zonation)

Megafaunal Zonation
(Western Alachua County)

I 4

chaperi zone

Asterocyclina -
vernoni zone

vanderstocki -
Hemicythere zone

Lepidocyclina -


Spondvius dumosus

Floridina antiqua

nodifera zone

I 'I.


Spirulaea vernoni
zone (Residual

Amusium ocalanum

Exputens ocalensis




_ ____









recognizable in the western part of Alachua County, and a third
zone stratigraphically below the Amusium ocalanum zone is named
the Exputens ocalensis zone. Amusium ocalanum has been figured
recently by Toulmin (1969, pl. 4, fig. 9), and Exputens ocalensis
(MacNeil) has been figured by Nichol and Shaak (1973, p. 73).
Figure 15 gives an approximate comparison between the present
megafaunal zonation, the foraminiferal zonation of Puri (1957), and
the bryozoan zonation of Cheetham (1963).
Hoganson, in his investigation of the Spirulaea vernoni zone in
peninsular Florida, found only one locality for the zone in Alachua
County. A few specimens of Asterocyclina sp. were found at Alachua
Sink, southeast of Gainesville. This confirmed the earlier report of
Tubulostium sp. (= Spirulaea sp.) from this site by Cooke (1945).
In this investigation many of the silicified residual boulders so com-
mon in the limestone plain were found to contain the Spirulaea
vernoni zone fauna. Hoganson (1972, p. 14) found that several species
were sufficiently common in the zone so that they may be considered
zone fossils. He listed the annelid worm Spirulaea vernoni Richards,
the echinoids Paraster armiger (Clark) and Wythella eldridgei
(Twitchell), and the pectinid Chlamys (Lyropecten) incertae Tucker-
Rowland. In addition, Puri (1957) listed several species of Astero-
cyclina that are confined to this zone in northwest Florida. The gas-
tropod Turritella martinensis Dall and a pelecypod, Chione sp., were
also found to be excellent zone fossils in the silicified residual bould-
ers in Alachua County. Turritella martinensis also occurs abundantly
in the Lower Oligocene Red Bluff Clay of Alabama and the Forrest
Hill Sand of Mississippi and has been used by several authors
(MacNeil, 1944, p. 1317; Hunter, 1972, p. 11-20; Harper, 1972) in
the correlation of strata in Florida to these units.
The two zone fossils, Spirulaea vernoni (Plate 1, Figures 1 and 2)
and Turritella martinensis, have been observed to occur in the same
stratigraphic interval at several localities in peninsular Florida. In
the western part of Alachua County, those silicified residual boulders
containing common Turritella martinensis also contain all the zone
fossils for the Spirulaea vernoni zone as described by Hoganson
(1972) and therefore are referred to the Crystal River Formation.
Figure 16 lists some of the fossils found in the Spirulaea vernoni
zone with an estimation of their abundance and Figure 17 shows the
approximate locations at which silicified residual boulders containing
the Spirulaea vernoni zone fauna were found.
McCullough (1969) traced the stratigraphic occurrence of the
pectinid Amusium ocalanum in peninsular Florida. He found that


Spirulaea Amusium Exputens
vernoni ocalanum ocalonsis
Species zone zone zone

Lepidocyclina spp. C VA-A C-R

Operculinoides spp. A A VA-A

Asterocyclina spp. VR-R

Paraster armiqer (Clark) C-R

Wythella eldridtei C-R

Oliqopygus spp. R A-C C

Amusium ocalanum Dall VA-C R-VR

Exputens ocalensis VR C-R

Chlamys incertae Tucker- C-R

Chlamys spillmani (Gabb) C VA-C C-R

Pecten perplanus Morton C-R C-R C

Plicatula filamentosa C-R C

Turritella martinensis A-C R

Gisortia harrisi Palmer R-VR

Aturia alabamensis (Morton) R R R

Spirulaea vernoni Richards A-C

Ocalina floridana Rathburn VR-R C-R

Figure 16. Faunal Assemblages, Crystal River Formation.

VA Very Abundant C Common VR Very Rare
A Abundant R Rare


R 18 E En

R 19 E
R 20 E

a Legend

a +O 04 Covered area.
SWestern limit of outcrop of lime:to
a + E of the Amusium ocalanum zone o! t
SCrystal River Formation. West of
this line, limestone of the Ex;ut_
ocalensis zone is at the surface.

V1 Western limit of the area where rer,
"- dual silicified boulders from the
E6 '- Spirulaoa vernoni zone of the
Crystal River Formation were found,
X +Southern limit of the area where re!
X s + } + dual silicified boulders from the
+- Suwannee Limestone were found.

SAmusium ocalanum zone residual


X + 0 Oligocene residual boulders
(Suwannee Limestone).
R 17 E R 1 E R 19 E R 20 E

Figure 17. Distribution of Faunal Zones, Western Alachua County.

the Amusium ocalanum zone lies stratigraphically below the Spi-
rulaea vernoni zone and that there appears to be no interpenetration
of the two zones. The zone is based primarily on the occurrence of
Amusium ocalanum. This bivalve is so common in parts of the Crystal
River Formation that the limestone is almost a coquina of its shells.
In addition to Amusium ocalanum, other common fossils found in
this zone are Lepidocyclina sp., numerous echinoids and especially
Oligopygus wetherbyi de Loriol and Oligopygus haldemani (Conrad),
and Chlamys spillmani. Some of the fossils associated with this zone
are listed on Figure 16. In the eastern part of the limestone plain,
the Amusium ocalanum zone is found at the top of the Crystal River
Formation with the exception of Alachua Sink where the Spirulaea
vernoni zone crops out. The top of this zone is irregularly eroded and
at no place in Alachua County is the full thickness of the zone ex-
posed. The Amusium ocalanum zone thins to the west and the lime-


stone exposed at the surface along the western margin of the county
is stratigraphically below the zone. Figure 15 compares the strati-
graphic range of Amusium ocalanum to the foraminiferal zonation
of Puri (1957) and the bryozoan zonation of Cheetham (1963) and
Figure 17 indicates the distribution of the zone in the western part
of Alachua County. Silicified residual boulders containing an Amusi-
um ocalanum zone fauna are common in all areas of limestone plain
and indicate that the zone once was continuous across the county.
The Exputens ocalensis zone is exposed stratigraphically below
the Amusium ocalanum zone along the western margin of the county
and in several limestone quarries. This zone is named for the relative-
ly common bivalve Exputens ocalensis (MacNeil) and is typically
exposed in several abandoned quarries and phosphate mines south-
west of Newberry. Nicol and Shaak (1973) described the stratigraphic
range of Exputens ocalensis in the Crystal River Formation as being
common in the Spiroloculina newberryensis zone and less common in
the Lepidocyclina Pseudophragmina zone of Puri (1957), (Figure
15). There is some overlap in the range of Exputens ocalensis and
Amusium ocalanum but because Amusium ocalanum rapidly becomes
rare near the base of its zone Exputens ocalensis becomes rare near
the top of its zone, little difficulty has been encountered in plac-
ing the boundary between the two zones. The base of the Exputens
ocalensis zone was not encountered in any of the quarries, pits,
or outcrops visited in the western part of Alachua County and
the zone may extend d6wn into the Williston Formation. In addition
to Exputens ocalensis, some other fossils found in this zone are
Lepidocyclina spp., Operculinoides spp., several species of echinoids,
Chlamys spillmani, Pecten perplanus Morton, and Plicatula fila-
mentosa Conrad. The relatively rare gastropod Gisortia harrisi Pal-
mer appears to be confined to this zone and the crab Ocalina floridana
Rathburn becomes more common within the zone. A portion of the
fauna associated with the Exputens ocalensis zone is listed in Figure
16 and the distribution of the zone is shown on Figure 17. No
silicified residual boulders containing a recognizable fauna of the
Exputens ocalensis zone were found in Alachua County.

The Crystal River Formation was deposited on the Ocala bank,
a submarine plateau over which water depth probably did not exceed
150 feet at any time (Cheetham, 1963, p. 35). A regional petrographic
study by Chen (1965) confirmed the presence of an Eocene carbonate


bank in Florida. Cheetham (1963, p. 1) considered the Ocala bank to
have been deeper than, but otherwise analogous to, the present great
Bahama bank. The foraminiferal assemblages studied by Puri (1957)
also indicate shallow warm-water conditions in an open sea.


The bioclastic foraminiferal limestone of the Crystal River For-
mation crops out over a wide area of the western part of Alachua
County as shown on the accompanying geologic map (Appendix 4).
Exposures of this limestone are numerous throughout the outcrop
area shown on the geologic map. The best exposures are found in the
more than 100 limerock quarries and phosphate pits in the western
part of the county. The most extensively quarried area of the county
is approximately 2 to 2.5 miles northeast of Newberry where over
15 quarries are located within a one-mile radius. At least seven
abandoned pits are located at Arredondo, southwest of Gainesville,
and many other quarries are scattered throughout the limestone
plain. Over 60 abandoned hard-rock phosphate pits are located in
Alachua County. Most were quarried down to the top of the Crystal
River Formation and expose small sections of limestone. The ma-
jority of these pits are located within a two-mile wide zone along
the western boundary of the county northwest of Newberry. There
are over 60 caves in the limestone plain and hundreds of sinks, most
of which expose some limestone of the Crystal River Formation.
Therefore, only a representative sample of the outcrops visited will
be detailed below.
Locality CR1: Abandoned lime quarry SE/4, SE/4, Sec.7, T.10S.,
R.18E., 3.0 miles west of 1-75 on SW 20th Avenue, southwest of
Bed Description Thickness (feet)
4 Surficial sand and soil. Common silicified residual 1-2
Crystal River boulders containing a Spirulaea vernoni
zone fauna.
Crystal River Formation, Ocala Group, Upper Eocene
3 White to cream-white granular foraminiferal and mol- 11.6
luscan bioclastic limestone. In places the bed is rather
unconsolidated and is almost a foraminiferal and mol-
luscan coquina. Common Lepidocyclina spp., Pecten
perplanus, Chlamys spillmani and Amusium ocalanum.


Also, echinoid plates and spines, bryozoans, starfish
ossicles and rare corals.
2 White grandular bioclastic limestone. Sugary textured 3.6
and relatively compact. Some bryozoans and echinoids.
Few Lepidocyclina spp.
1 White to cream-white granular foraminiferal bioclastic 6.0
limestone. Small horizontal solution cavities are com-
mon and the bed is locally case-hardened. Lepidocy-
clina spp. very common, also Amusium ocalanum,
bryozoans, and echinoid plates and spines.
Total thickness ........................... ...... 22-23 ft.
The entire thickness of limestone exposed at this quarry is in the
Amusium ocalanum zone except for the silicified residual boulders
at the surface which are referred to the Spirulaea vernoni zone. There
is another small quarry just west of this quarry where a similar
section is exposed.
Locality CR2: Alachua Sink. SW/4, Sec. 22, T.10S., R.20E., south-
east of Gainesville. Section after Cooke (1945, p. 148).
Bed Description Thickness (feet)
Hawthorne Formation, Middle Miocene
6 Mostly concealed; much debris of gray or white cal- 20.0
careous sandstone like bed 4, in places ferruginous;
to top of slope.
5 Green siliceous clay resembling fullers earth 0.3
4 White calcareous sandstone containing small ellipsoidal 1.6
phosphatic grains.
3 Green clay resembling fuller's earth. 0.5
2 Unconsolidated gray calcareous sand, underlying de- 0.5
posit not exposed.
Crystal River Formation, Ocala Group, Upper Eocene
1 White limestone, hard and cherty in places, soft and 14.0
saccharoidal elsewhere; highly fossiliferous; exposed
30 ft. north of the beds described above.
Total thickness ........ .......................... 36.1 ft.
Cooke (1945) observed Tubulostium sp. at this site, and Hoganson
(1972) confirmed that the limestone exposed at Alachua Sink is an
outcrop of the Spirulaea vernoni zone. This is the only site thus far
seen in Alachua County where this zone crops out as uneroded
limestone as opposed to residual silicified boulders.
Locality CR3: Abandoned limestone quarry at Arredondo. NE
corner, NE/4, SE/4, Sec. 21, T.10S., R.19E., southwest of


Bed Description Thickness (feet)
4 Surficial sand and residual silicified boulders. Nu- Variable
merous solution pits filled with reddish-brown clayey
sand at top of quarry. Amusium ocalanum zone boul-
Crystal River Formation, Ocala Group, Upper Eocene
3 White to cream-white granular foraminiferal/bioclastic 14.0
limestone similar to bed 1. Amusium ocalanum,
Chlamys spillmani, echinoids and very common Lepi-
docyclina spp.
2 Cream to reddish-brown limestone of Bed 1. Some 2.0
iron staining and many small horizontal solution cavi-
1 White to cream massively bedded granular foramini- 8.0
feral bioclastic limestone. Common Lepidocyclina
spp., Amusium ocalanum and Oligopygus sp.
Total thickness .................................... 24.0 ft.
The entire thickness of limestone exposed at this quarry and at the
other quarries at Arredondo is in the Amusium ocalanum zone. Most
of the silicified residual boulders at these quarries belong in the
Amusium ocalanum zone but there are some Spirulaea vernoni zone
boulders present.
Locality CR4: Abandoned limestone quarry, SW/4, NE/4, Sec. 35,
T.9S., R.18E., west of Gainesville. Section measured on north-
west wall of quarry. Section after Puri (1957, p. 58).
Bed Description Thickness (feet)
Crystal River Formation, Ocala Group, Upper Eocene
4 Amusium bed. White, coarsely granular, chalky lime- 21.0
stone with abundant Amusium sp.
3 A coquina of large flat foraminiferal shells in a chalky 10.0
matrix with some Amusium sp. present.
2 Soft, chalky, limestone matrix cementing a lepido- 30.0
cyclinic, camerinid shell coquina. Spondylus sp. and
Pecten (striated) common. Holothurian-like concre-
tions present in the lower portion of section.
1 Modiolus bed. Soft, granular limestone with pockets 5.0
of Modiolus sp. present.
Total thickness .................................... 66.0 ft.
The residual silicified boulders at this quarry contain both the
Spirulaea vernoni zone and Amusium ocalanum zone fauna. Mc-
Cullough (1969, p. 49) reports that the upper 44 feet of limestone


contains the Amusium ocalanum zone fauna. The basal 22 feet are
referred to the Exputens ocalensis zone.
Locality CR5: Abandoned limestone quarry at Buda, Florida. NE/4,
NE/4, Sec. 32, T.8S., R.17E, southwest of High Springs. Sec-
tion after Puri (1957, p. 60.)
Bed Description Thickness (feet)
Crystal River Formation, Ocala Group, Upper Eocene
7 Soft, chalky, friable limestone, studded with Fora- 14.6
minifera and Mollusca.
6 Soft, chalky limestone, questionably glauconitic, with 9.0
abundant Spondylus sp.; upper portion contains stri-
ated Pecten sp.
5 Cream colored, moderately hard, granular limestone, 3.0
with some holothurian-like concretions; partially dolo-
4 Soft, granular limestone, with very little chalk, thin 5.0
streaks of foraminiferal shell coquina; striated Pecten
3 Larger foraminiferal shell coquina in a granular matrix; 5.0
abundant mollusks; some holothurian-like concretions.
2 Cream-colored, soft, granular, somewhat chalky lime- 2.5
stone; with abundant holothurian-like concretions
and Spondylus.
1 Cream-colored, granular, pasty limestone; nodular 4.0
weathering; abundant holothurian-like concretions:and
Spondylus sp., poorly bedded; dolomitized ledges up to
0.5 feet thick with casts of mollusks.
Total thickness ................................... 43.1 ft.
McCullough (1969, p. 49) places the upper 4.0 feet of limestone at
this pit in the Amusium ocalanum zone and the remaining thickness
is referred to the Exputens ocalensis zone.
Locality CR6: Limestone quarry southwest of Newberry, SW cor-
ner, SE/4, Sec. 8, T.10S., R.17E.
Bed Description Thickness (feet)
Crystal River Formation, Ocala Group, Upper Eocene
2 White, massively bedded, granular, soft, foraminiferal 9.0
bioclastic limestone. Chalky. Numerous large Lepido-
cyclina spp. Few Exputens ocalensis and Chlamys
spillmani. Also Spondylus sp., bryozoans and echinoids.
A few rare Amusium ocalanum found at top of section.
1 White to cream-white massively bedded granular bio- 13.0
plastic limestone. In places this unit is well indurated


and tough, especially near the top. Numerous smaller
Lepidocyclina spp. and molds of mollusks were ob-
served. Exputens ocalensis, Plicatula filamentosa, Pec-
ten perplanus and Oligopygus sp. are common. Also,
Ocalina floridana and Calappilia brooks Ross and Sco-
laro were seen.
Total thickness ...................................... 22.0 ft
The entire 22 feet of limestone exposed in this pit is referred to the
Exputens ocalensis zone. This locality is considered to be typical of
the zone.
Locality CR7: Limestone quarry at Haile, SE/4, Sec. 13, T.9S.,
Bed Description Thickness (feet)
Crystal River Formation, Ocala Group, Upper Eocene
2 White to cream-white granular foraminiferal bioclastic 11.0
limestone. Bed is softer and more granular than unit 1.
Numerous large Lepidocyclina spp. and echinoids. Few
Amusium ocalanum and Chlamys spillmani.
1 White to cream-white granular bioclastic limestone. In 17.0
places the unit is well indurated with crystalline
calcite. Abundant echinoids especially Oligopygus spp.
and Laganum spp. Exputens ocalensis, Pecten perplan-
us and molds of gastropods are present.
Total thickness .................................... 28.0 ft.
The basal 17 feet of section exposed at this quarry is referred to the
Exputens ocalensis zone. A similar section is exposed in all the nearby
pits in the vicinity of Haile.
In addition to the measured sections, the following general locality
listings are of interest:
Locality CR8: Abandoned limestone quarry southeast of Haile,
NW/4, Sec. 29, T.9S., R.18E. This small quarry is about 25
feet deep and exposes a section similar to the Haile quarries.
Numerous residual silicified boulders in the vicinity of this pit
contain a Spirulaea vernoni zone fauna. Chlamys spillmani,
Ostrea podagrina Dall, Chione sp., and a few Asterocyclina sp.
were observed. Most of the boulders containing this fauna at
this locality show irregular exfoliation plates which indicate
prolonged weathering.
Locality CR9: Borrow pit, 0.5 miles south of the intersection of 1-75
and SR-26, west of Gainesville, SW/4, NW/4, Sec. 4, T.10S.,
R.19E. This is a shallow pit which contains several very large
silicified boulders containing a Spirulaea vernoni zone fauna.


Selective silicification and replacement have left beautifully
preserved siliceous pseudomorphs of fossils known from other
localities only from casts and molds. The collection from this
site is Florida State Museum accession number 702. Abundant
fossils from this site include Spirulaea vernoni, Turritella mar-
tinensis, Chione sp., Cassidulus trojanus Cooke, several species
of small gastropods, corals, bryozoans, and foraminifers.
Locality CR10: Limestone quarry just west of Locality CR1. SW/4,
SE/4, T.10S., R.18E., southwest of Gainesville. The limestone
exposed at this quarry is similar to locality CR1. Numerous
silicified residual Spirulaea vernoni zone boulders are found at
the surface in and near the quarry. Paraster armiger, Turritella
martinensis, and numerous small gastropods including Diento-
mochilus sp. are present.
Locality CR11: Spirulaea vernoni zone boulders on SR-232 NW
corner, NE/4, NE/4, Sec. 15, T.9S., R.18E. These boulders form
the crest of a small ridge of limestone and contain a typical
Spirulaea vernoni zone fauna.
Locality CR12: Spirulaea vernoni zone boulders along a road just
south of High Springs. NW/4, Sec. 11, T.8S., R.17E. (Figures
18 A-D). Numerous boulders along the road and in a small
borrow pit just north of the road contain the typical Spirulaea
vernoni zone fauna. Boulders at this site are intermixed with
silicified residual boulders of Suwannee Limestone containing
casts and molds of the characteristic Oligocene echinoid Rhyn-
cholampus gouldii (Bouv6).
Locality CR13: Spirulaea vernoni zone boulders southeast of Gaines-
ville, south line, Sec. 5, T.10S., R.19E. Numerous silicified
boulders contain a typical Spirulaea vernoni zone fauna. Com-
mon Paraster armiger, Wythella eldridgei, Chlamys (Lyro-
pecten) incertae, Ostrea podagrina, and Spirulaea vernoni.
Chione sp. and Turritella martinensis are present but are not
as common as at other localities.
Locality CR14: Amusium ocalanum zone residual boulders are com-
mon in a small borrow pit on southwest 20th Ave., Sec. 10,
T.10S., R.19E. Common fossils are Amusium ocalanum,
Chlamys spillmani and Lepidocyclina spp.
Locality CR15: Roadcut on southwest 20th Ave., Sec. 9, T.10S.,
R.19E. This roadcut exposes several filled sinks containing
residual boulders of the Spirulaea vernoni zone and overlain by
sediments of the Hawthorne Formation containing silicified


Figure 18A. Boulders of the Crystal River Formation (a) and the Suwannee
Limestone (b) along a road just south of High Springs (NW 1/4,
Section 11, T. 8 S., R. 17 E.).

Figure 18B. Typical appearance of a limestone boulder of the Crystal River
Formation from the same locality as A.


Figure 18C. Spirulaea veroni (a) and Turritella martinensis (b) in a limestone
boulder of the Crystal River Formation, from the same locality as A.

:igure 18D Rhyncholampus gouldii in a silicified residual boulder of the Su-
wannee Limestone, from the same locality as A.


Fml 4Ws~R ~
* t: ~z"A



Ostrea sp. cf. 0. normalis. Small pinnacles of limestone con-
taining Amusium ocalanum occur at the base of the outcrop.


Silicified residual boulders of Suwannee Limestone containing
numerous molds of the characteristic echinoid Rhyncholampus
gouldii are very common in the northwestern 'portion of the county
around High Springs (Figure 17). These residual boulders become
more common northwestward from Alachua County toward the
area in Columbia County where Oligocene limestone crops out. It is
possible that erosionally isolated remnants of limestone may occur
in northwest Alachua County though none were seen during this
field investigation. In several areas these boulders are found (as
for example Locality CR12) intermixed with residual boulders con-
taining a Spirulaea vernoni zone fauna overlying continuous lime-
stone of the Crystal River Formation containing Amusium ocalanum
DalL This indicates the former presence of not only a greater thick-
ness of the Crystal River Formation but also the former presence
of a once continuous layer of Suwannee Limestone, now eroded, and
an overlying source of silica (the Hawthorne Formation) also now
Residual, isolated deposits of marine Oligocene sediments have
also been found in several other areas of Alachua County. Two wells
encountered Oligocene sediments as seen in Appendices 1 and 2.
Well W-324 (just north of the Gainesville Municipal Airport) pene-
trated 21 feet of Oligocene marine sediments and well W-2580 (just
north of La Crosse) penetrated 5 feet of possible Oligocene (see Ap-
pendix 2 for well logs). Cooke (1945, p. 200 and 202) reported re-
sidual silicified remnants of Suwannee Limestone containing Rhyn-
cholampus gouldii in a phosphate pit one mile north of Newberry.
At the Pliocene vertebrate site at McGehee Farm, approximately
three miles north of Newberry, several specimens of Rhyncholampus
gouldii were collected. The Pliocene vertebrates at this site accumu-
lated in a stream (S. David Webb, personal communication), and
the echinoids do not appear to be excessively water-tumbled. It is
concluded that in middle Pliocene time the areal extent of the Su-
wannee Limestone was much greater than today and that the head-
water portion of this stream was eroding through this formation.
Specimens of Rhyncholampus gouldii in the Florida State Museum
collections were collected from the vicinity of the quarries at Arre-


dondo southwest of Gainesville. In view of the occurrences of residual
marine Oligocene sediments in widely separated areas of the county,
it is not considered unreasonable to postulate that the Suwannee
Limestone was once deposited completely across Alachua County.
In the Late Oligocene and Early Miocene, Alachua County was a
positive area exposed to erosion and karstification. Several land verte-
brate deposits of this period have been discovered in the western
part of Alachua County. A Late Oligocene (Whitneyan) land verte-
brate fauna from just southwest of Gainesville was reported by Pat-
ton (1967, 1969). This deposit (the 1-75 site) was preserved in a
sinkhole in the Crystal River Formation and overlain by Hawthorne
sediments. It contained a diversified terrestrial vertebrate fauna with
some estuarine elements. Patton (1969, p. 545) states, "The 1-75 as-
semblage suggests that faunal connections between Florida and other
biotic provinces of North America, especially the Great Plains, were
at times relatively open." This site is significant because it is the
oldest land vertebrate deposit in Florida (Patton, 1967), and it in-
dicates that movement of the Ocala uplift began before Late Oligo-
cene time. Three other approximately contemporaneous land verte-
brate deposits have been found in or near the western part of Alachua
County. Simpson (1932) discussed an Early Miocene vertebrate
fauna from a now abandoned hard-rock phosphate pit west of New-
berry (Sec. 31, T.9S., R.17E.). A second vertebrate locality of Late
Early Miocene age is exposed in a roadcut on Colclough Hill in
southwest Gainesville. This deposit produced the tooth ". of the
small horse Parahippus blackbergi and a variety of scraps and brack-
ish water vertebrates" (Olsen, 1964, p. 602-604). This deposit was
also preserved in a small sink in the Upper Eocene Crystal River
Formation and overlain by Hawthorne sediments. Brodkorb (1963,
p. 165) noted that this species of Parahippus also occurs in the
Thomas Farm locality which indicates the approximate contem-
poraneity of the two sites. The Thomas Farm locality, though not
located in the western part of Alachua County, should be mentioned
here since it contains one of the richest vertebrate faunas of Early
Miocene age in Florida. Patton (1967, p. 5) states, "Physical and
faunal evidence indicates that the fossil-bearing sediments accumu-
lated in a sinkhole formed in the underlying Ocala Limestone."
Faunal lists and discussions of this site are given by several workers
including Puri and Vernon (1964) and Patton (1967).
The vertebrate localities discussed above (1-75, Newberry, Col-
clough Hill, and Thomas Farm) are considered to have been de-
posited on an uplifted, eroded, and sinkhole-pitted surface prior to


the deposition of the Hawthorne Formation. Sediments of the Lower
Miocene Tampa Formation are absent from western Alachua County
and, as indicated by the vertebrate deposits, probably were never
deposited. The earliest movement of the Ocala uplift probably was
in the Middle Oligocene after the deposition of the Suwannee Lime-
stone and before deposition at the 1-75 locality (Late Oligocene).
This area probably remained a positive topographic feature through-
out the Early Miocene until inundated by the Hawthorne sea.


The early reports concerning the Hawthorne Formation are
summarized by Cooke and Mossom (1929) who redefined the unit
as a member of the Alum Bluff Group of Middle Miocene age.
This age correlation has been accepted by several subsequent workers
including Cooke (1945), Puri (1953), Pirkle (1956b), Carr and
Alverson (1959), Puri and Vernon (1964) and is accepted here as
the probable age for the Hawthorne sediments in the western part
of Alachua County. Several other reports including Brooks (1966,
p. 40), Brodkorb (1963), and Espenshade and Spencer (1963) in-
dicate an Early to Middle Miocene age for the unit, and Brooks
and Underwood (1967) noted that Hawthorne-type materials in
Florida range from Early Miocene to Pliocene.
In naming this unit, Dall and Harris (1892) used the spelling
Hawthorne. Following the discussion by Brodkorb (1963, p. 159),
this is the spelling used in this report.

Excellent discussions of the lithologic characteristics of the Haw-
thorne Formation in Alachua County are given by Pirkle (1956b
and 1958). The Hawthorne basically consists of varying amounts
of clay, quartz sand, calcitic and dolomitic carbonate, and phos-
phatic grains and pebbles. Lithologic variability is more the rule
than the exception and units may pinch out, interfinger or intergrade
both laterally and vertically. There are two lithologic types that
appear to be most common in Hawthorne Formation exposures in
western Alachua County. One is that of a phosphatic, sandy, some-
times dolomitic limestone and the other is a gray to bluish-gray
sandy clay or clayey sand, which is sometimes calcareous and phos-
phatic. Occasionally layers or lenses of relatively pure quartz sand,
fullers earth-type clay, or limestone are found.


Outcrops that show unweathered exposures of Hawthorne sedi-
ments are relatively rare in western Alachua County and most ex-
posures show a highly weathered and leached zone of sediments
derived from the Hawthorne Formation. Weathered exposures are
most commonly reddish-brown to white, clayey, calcareous quartz
sands with frequent limonitic and calcareous pebbles. Worn cal-
careous pebbles showing a boxwork structure and silicified fragments
of Ostrea sp. are common. Pirkle (1958, p. 152) observed that one
of the common sedimentary structures found in the Devil's Mill
Hopper is boxwork. This is an interlacing network of calcium car-
bonate deposited around and between small blocks of clay which
were formed as a result of shrinkage during drying. Worn pebbles
showing a boxwork structure are common in weathered exposures
of the Hawthorne Formation in western Alachua County. The
calcium carbonate in the boxwork structure is often replaced by
wavellite as reported by Blanchard and Denahan (1966).
An interesting, and as yet incompletely resolved problem, is
presented by the concentration of phosphate at the top of the
Devil's Mill Hopper (see section, Locality H3) and other localities
at the top of the Hawthorne Formation. This material is believed to
have accumulated in shallow marine waters during the deposition of
the Hawthorne and subsequently reworked by fresh water streams
(Pirkle, 1956b, p. 219) and possible also by marine waters. The
sediments of this unit are generally unconsolidated phosphatic sand,
clayey sand, or calcarious sand, and contain reworked Upper Miocene
marine invertebrates and Middle Pliocene terrestrial vertebrates
(Brooks and Underwood, 1967, p. 17).

The identifiable fauna of the Hawthorne Formation in the west-
ern part of Alachua County is extremely meager. Those fossils which
have been identified indicate that the Hawthorne Formation and the
Chipola Formation of western Florida are essentially contemporane-
ous. The Chipola Formation has been considered to be Middle
Miocene (Cooke, 1945; Puri and Vernon, 1964; and others).
In the lower portion of the Hawthorne section exposed at the
Devil's Mill Hopper, the bivalves Pecten acanikos Gardner and
Anomia floridana (Dall) are found. An unidentified species of sessile
barnacle occurs in several units of this section. This was the only
site in the western part of Alachua County where Anomia floridana
and Pecten acanikos were observed, though they are found in Haw-


thorne sediments both north and south of the county. In a roadcut
on 1-75 about 0.4 miles north of the SR-232 overpass (Locality H5),
silicified fragments of the echinoid Abertella aberti (Conrad) were
found. This echinoid has also been found in the Choptank Formation
of Maryland and the Chipola Formation of western Florida (Cooke,
1959, p. 45). This fossil has not been previously reported from the
Hawthorne Formation. Probably the most common fossil found in
the Hawthorne Formation of western Alachua County is Ostrea
normalis. This oyster is fairly common and" is quite often partially
silicified. Silicified fragments of Ostrea normalis are found in nu-
merous outcrops of weathered Hawthorne, and Locality H1 is a
section near a small oyster bioherm typical of several such outcrops
in Alachua County.
Large heads of the colonial coral Siderastraea siderea (Figure 19)
are found in the northwestern part of the county. These corals are gen-
erally silicified and may be 2 to 3 feet in diameter. They are generally
found in the weathered residual mantle overlying the Hawthorne

Figure 19. Sideastraea siderea Ellis and Solander. Side view of silicified spec-
imen that Is 27 cm high and has a maximum diameter at the top of
36 cm. Florida State Museum cat. no. 4386, hypotype. Locality: H2,
Alachua County. Sinkhole approximately 4 miles northeast of High
Springs, Sec. 18, T7S, R18E.



Suwannee Co.

Baker Co.

Alachua Co.

Levy Co.

0 o 10 20 30

Scale in miles


0 Locality.

Zone of occurrence.

Figure 20. Occurrence of Hawthorne Formation Corals.



Formation on hilltops and hillsides and in stream beds that are
eroding through the Hawthorne. Dall and Harris (1892) described
these corals as being from the Hawthorne Formation and this in-
vestigation confirms his observation. Several fragments of coral were
observed in place in the lower zone of the Hawthorne Formation ex-
posed at White Springs in Hamilton County. In the areas where it
is common, the coral heads are generally found between 100 and 125
feet above sea level and no corals have been found above 135 feet
in the Hawthorne or surficial mantle. No other fossils were found
in western Alachua County associated with these corals. The corals
are also found in southeastern Columbia County and at White
Springs in Hamilton County (Figure 20). They occur generally
along a north-south zone through the three counties and probably
represent a high-energy zone in the Hawthorne Formation.
In addition to the marine invertebrates, sirenian rib fragments,
shark teeth and ray dental plates are locally abundant in the Haw-
thorne Formation.
The Hawthorne Formation of western Alachua County was
probably deposited in a shallow marine sea. Deposition was relatively
slow and the water remained fairly shallow as evidenced by oyster
biohermes in various localities throughout the unit and several brec-
ciated zones as seen in the Devil's Mill Hopper (Pirkle, 1958).


The phosphatic sandy clays, clayey sands and dolomitic lime-
stones of the Hawthorne Formation underlie a large portion of the
western part of Alachua County as shown on the geologic map
(Appendix 4). The entire northeastern half of the area studied is
underlain by this formation. Surficial exposures of this unit, how-
ever, are limited to the vicinity of the Santa Fe River on the north
and to the Northern Highlands Marginal Zone along the western
margin of the formation's outcrop area. In the Northern Highlands
Plateau area, natural outcrops are essentially nonexistent due to the
flat terrain and thick surficial soil cover. The best exposures of this
unit are found in several sinkholes and along several roads cut through
the marginal zone. The following sections and localities typical of
the formation are listed or described.
Locality H1: Roadcut on the south side of a graded road approxi-
mately 1.0 miles south of the Santa Fe River and 0.2 miles
west of Fla-241. Sec. 34, T.6S., R.18E.


Bed Description Thickness (feet)
Hawthorne Formation, Middle Miocene
4 Surficial sand and soil, weathered Hawthorne Forma- 1.25
tion. Light brown calcitic quartz sand with common
limonitic and calcitic nodules and pebbles.
3 White to light gray sandy calcitic clay stained reddish- 1.3
brown near top. Thin beds of medium sized, well
rounded, moderately well sorted quartz sand. Unit
weathers blocky as a result of high clay content.
2 Gray thin bedded sandy clay. Medium quartz sand 0.8
well rounded and moderately well sorted. Common
Ostrea normalis.
1 Gray to light green blocky clay with some quartz sand. 1.6
Common partially silicified Ostrea normalis in an artic-
ulated, undisturbed position.
Total thickness ......................... ......... 4.95 ft.
Units 1 and 2 grade laterally into a small oyster bioherm containing
numerous silicified, articulated individuals of Ostrea normalis. No
other fossils were observed at this locality.
Locality H2: Sinkhole approximately 4 miles northeast of High
Springs, Sec. 18, T.7S., R.18E. This sink is near, and may be,
the "Nigger Sink" locality mentioned as typical of the Haw-
thorne Formation by Johnson (1885), and Dall and Harris
Bed Description Thickness (feet)
Hawthorne Formation, Middle Miocene
6 Surficial sand and soil containing weathered remnants 2.0
from lower units including very common coral frag-
ments and limonitic pebbles.
5 Light grayish-green sandy clay or clayey sand. Quartz 4.0
sand moderately rounded and sorted. Common Ostrea
normalis and Siderastraea siderea. Unit becomes thin-
ner bedded and weathered near top.
4 Grayish white phosphatic calcareous sandstone with 2.0
small clay blocks. Relatively well indurated.
3 Light green clayey sand with lenses and blocks of 3.0
green clay. Some calcareous boxwork structure and
common Ostrea normalis.
2 Covered slope. 8.0
1 Bluish-gray to light-green sandy clay. Quartz grains 4.0
subrounded and moderately well sorted. Common iron
staining, clay is blocky and contains sandy lenses.


Total thickness ..................................... 23.0 ft.
In the vicinity of this sink, silicified heads of the colonial coral
Siderastraea siderea are extremely common and are the local field
Locality H3: Devil's Mill Hopper, northwest of Gainesville, Sec. 15,
T.9S., R.19E. Section slightly modified after Pirkle et al.,
1965, p. 39.

Bed Description Thickness
Surficial sands
16 Sand. Loose, gray to white.
Pliocene (?), Bone Valley equivalent (?).
15 Phosphate concentration. Abundant pebbles and
grains of phosphorite embedded in a matrix consisting
largely of quartz sand and clay. Many of the pebbles of
phosphorite are impure limestone or marl fragments
in which phosphate has replaced carbonate. These
pebbles contain much included quartz sand. Most of
the phosphate particles are some shade of white, gray,
brown or black.
Hawthorne Formation, Middle Miocene
14 Dolomitic limestone to dolomite. Cream to white to
yellow containing in places abundant molds and casts
of marine pelecypods and gastropods. Locally quartz
sand is an important constituent of the unit. In some
places phosphate particles are common.
13 Clayey sand. Yellow to yellow-brown with local oc-
currences of irregular masses of white carbonate. Up-
per 7 inches of unit has a greenish-blue color and a
higher content of quartz sand.
12 Clayey sand. Upper 1.5 feet of unit is dark blue; rest
of unit is a light pastel greenish-blue. Pyritic.
11 Conglomerate. Green to yellow. Unit consists of a mix-
ture of quartz sand, clay and carbonate. The pebbles
appear to be composed largely of quartz sand ce-
mented with clay and/or carbonate. Locally black
phosphate grains are common. Pyritic.
10 Calcareous clayey sand and sandy clay to massive
blocky clay. Light green to blue. Locally, phosphate
particles are common. In places the unit is highly cal-
careous. The clay present in this unit and continuing
upward through unit 13 has a different appearance
from the clay of underlying units and usually has a










darker color when fresh. Quartz sand, carbonate, and
phosphate particles are more abundant in the upper
10 feet of the unit. Much of the lower 9 feet consists
of massive blocky clay with interbedded stringers and
small lenses of sand and carbonate. Many of the clay
blocks are surrounded by networks of sand and car-
bonate. In the lower foot of the unit quartz sand in-
9 Massive clay. Gray to greenish-gray, blocky with net- 3.5
works of sand and carbonate surrounding some clay
blocks and with stringers of sand and carbonate within
the clay.
8 Clayey sand. Gray, soft. 1.9
7 Limestone, white to gray, lithified. Contains remnants 2.0
of clay blocks. Forms nodular masses and slight ledges
upon weathering.
6 Clay. Gray to grayish-green to olive-green, massive. 10.25
Clay is blocky with networks of carbonate surrounding
clay blocks and with stringers and small lenses of car-
bonate present within the clay. Carbonate is apparent-
ly replacing the clay.
5 Zone containing intraformational breccias or con- 10.9
glomerates. Upper part of unit is a prominent con-
glomerate. Near base of unit is another well defined
conglomerate. Several less conspicuous conglomerates
are present throughout the unit. The intraformational
breccias or conglomerates consist of various mixtures
of quartz sand, clay, phosphate particles, and car-
bonate. In places these zones contain calcitic fossil
shells, and angular blocks and rounded pebbles of
grayish-green clay. The most prominent fossils are
Pecten acanikos Anomia floridana and barnacles.
4 Mixture of quartz sand, clay and carbonate. Distinct 1.1
3 Clayey limestone. White, soft. Contains remnants of 2.6
gray clay blocks, more numerous near upper part of
2 Covered slope. An occasional exposure. Approximate- 9.1
ly 6.5 feet above base of unit calcareous sand is ex-
posed. Just over unit 1, clay is exposed. May be


1 Sandy limestone. Locally dolomitic. White. Rests 3.17
upon underlying Ocala Limestone. In places dense,
dark colored, with stringers of quartz sand. Contains
occasional blocks of gray clay. Parts of this unit are
highly silicified. Where silicified portions rest upon
Ocala Limestone, that limestone is often silicified.
Total thickness ................................... 116.8 ft.
The Devil's Mill Hopper is one of two type localities for the Haw-
thorne Formation as designated by Puri and' Vernon (1964, p. 146).
Due to the lens-like nature of most of the units in this formation
and erosion caused by the numerous streams from springs that origi-
nate near the top of unit 13, sections measured at different times
will show only an approximate correspondence.
Locality H4: Drainage pit at the Gainesville Industrial Park located
approximately 0.7 miles north of the 1-75 and Fla-121 inter-
change, southwest of Gainesville. This pit exposes about 25
feet of Hawthorne sediments overlying several pinnacles of the
Crystal River Formation (Amusiumt ocalanumn zone). The
fracture pattern in the Hawthorne Formation (Figure 12) was
measured in the bed of a drainage ditch on the east end of
the pit.
Locality H5: Road cut on 1-75 about 0.4 miles northwest of the
Fla-232 overpass, Sec. 12, T.9S., R.18E. Numerous silicified
fragments of the echinoid Abertella aberti were found in a
weathered calcareous quartz sandstone in a cut on the north
side of the highway.
Locality H6: Contact between the Hawthorne Formation and the
Crystal River Formation as seen in Warrens Cave, Sec. 13,
T.9S., R.18E. This cave is formed at the contact between
these two formations, and the ceiling of portions of the upper
level of the cave is composed of sandy clays of the Hawthorne
Formation. An undisturbed bioherm of the oyster Ostrea nor-
malis was found at and within 2 feet of the contact with the
underlying Crystal River Formation. Shark teeth and sirenian
ribs were also found.
Locality H7: Contact between the Hawthorne Formation and the
Crystal River Formation exposed at Fisher Sink, Sec. 36,
T.8S., R.18E. This sink is the primary drain for Sanchez
Prairie and exposes about 25 feet of Hawthorne clays and
sandy clays overlying the Crystal River Formation. Wavellite-
cemented sandstone from weathered Hawthorne Formation


sediments has been reported from this site (Blanchard and
Denahan, 1966).
Locality H8: Approximately 30 feet of clays and sandy clays of the
Hawthorne Formation are exposed in a cut on the west side
of US-441 about 2 miles north of Micanopy and across from
Lake Wauberg. Samples from this outcrop were studied petro-
graphically by Assefa (1969).
Locality H9: Hawthorne sediments are exposed in a road cut on
Colclough Hill in southwest Gainesville. Limestone of the
Crystal River Formation is exposed in road cuts up to an
elevation of approximately 95 feet. About 0.5 miles north of
this outcrop, along Sweetwater Branch, horizontal sediments
of the Hawthorne Formation are exposed at an elevation of
less than 75 feet. During a recent widening of SR-831 a fresh
cut was made down the hillside. No evidence of slumped or
tilted beds was found, an indication that this may represent
original deposition of Hawthorne sediments over a buried lime-
stone hill.
In addition to the above mentioned localities, several wells for
which geologic logs are given in Appendix 2 penetrate the Hawthorne
Formation. Many other good outcrops are found in road cuts along
1-75 and in sinks and stream beds in the Northern Highlands
Marginal Zone.
Numerous residual remnants of the Hawthorne Formation are
found in the limestone plain (geologic map, Appendix 4). These iso-
lated patches of Hawthorne sediments usually form low hills and
expose highly weathered sections of sandy clay or clayey sand. The
presence of these erosionally isolated, weathered patches of the
Hawthorne Formation is an indication of the former greater extent
of the formation. It is postulated to have once covered the entire
county to a considerable depth. Most of the sediment was probably
removed by higher sea level stands in the Pliocene and Pleistocene
and by sheetwash and stream erosion during the Pleistocene.


Deposits containing a Late Miocene fauna are rare in the western
part of Alachua County. Upper Miocene sediments do occur both
northeast and south of the county. Overlying Hawthorne sediments
at Brooks Sink (about 4 miles east of Brooker, Bradford County,
and northeast of this area of study) is about 18 feet of a shell marl


that has been dated as Late Miocene based on ostracodes (Pirkle,
1956b, p. 210). In the eastern part of Alachua County several wells
have encountered Late Miocene sediments (Espenshade and Spencer,
1963). Late Miocene marine invertebrates have been reported from
the upper bed at the Devil's Mill Hopper (Brooks and Underwood,
1967, p. 17) and in similar sediments north of the Gainesville Airport
(op cit., p. 20). Teleki (1966) reported Upper Miocene sediments
underlying the southern portion of the Brooksville Ridge. Espenshade
and Spencer (1963, p. 27 and Table 10) report a Late Miocene marine
fauna in residual phosphatic sandstone in an abandoned phosphate
pit (NE/4, Sec. 21, T.10S., R.17E., south of Newberry) in south-
western Alachua County.
Considering the widely scattered occurrence of marine Upper
Miocene sediments in and around Alachua County, it is considered
possible that these sediments were once deposited entirely across the
county and have been removed. This is the same conclusion reached
by Brooks (1966, p. 41).


Sediments referred to the Alachua Formation were described by
Dall (1887, p. 164-165) and named by Dall and Harris (1892, p. 127).
He described the Alachua clay as being a bluish or grayish extremely
tenacious clay containing the bones of extinct mammals. The Plio-
cene vertebrate deposit first mentioned by Dall ("Mixson's Farm,
10 miles south and 1.5 miles east of Archer," Dall and Harris, 1892,
p. 128) is considered to be the type locality (Webb, 1964, p. 25).
This locality is about 2 miles north of Williston, Levy County,
Florida. Leidy and Lucas (1896) described the vertebrate fauna of
the Alachua clays. The reports of Matson and Clapp (1909) and
Matson and Sanford (1913) contain short discussions of the Alachua
Formation. Sellards (1910a) named the hard-rock, phosphate-
bearing deposits the Dunnellon Formation, and he (Sellards, 1913)
presented an excellent discussion of the unit as did Matson (1915).
The original concept of the Alachua Formation was radically changed
and expanded by Sellards (1914) who included the hard-rock phos-
phate sediments of the Dunnellon Formation in the Alachua Forma-
tion. Short discussions of the Alachua Formation in Alachua County
are given in reports by Cooke and Mossom (1929), Cooke (1945),
and Puri and Vernon (1964). There are many excellent reports on
the Florida phosphate deposits including Sellards (1913), Matson


(1915), Mansfield (1942), Vernon (1951), Pirkle (1956), Carr and
Alverson (1959), Cathcart and McGreevy (1959), Espenshade and
Spencer (1963), Teleki (1966), and Olson (1972).

During the course of this investigation, it was found possible to
differentiate and map two distinctive lithologic units in western
Alachua County from the sediments previously mapped as the
Alachua Formation. The upper sand unit which overlies the Alachua
Formation in the southwestern corner of Alachua County is con-
sidered to be Pleistocene in age and will be discussed in a later
section. Differentiation of the two units underlying the Brooksville
Ridge has been made by several authors including Matson (1915),
Espenshade and Spencer (1963) and Teleki (1966), but no attempt
to map them was made.
An excellent description of the Alachua Formation was given by
Matson and Clapp (1909):
The Alachua Clay consists of blue to gray sandy clay which weathers
to light yellow or red from the presence of iron oxide. There is
usually sufficient clay to give the material a distinct plasticity, and
sand is commonly present in considerable quantities. The weathered
material is frequently more or less concretionary as a result of the
aggregation of the iron oxide. The formation is nearly destitute of
fossils except in a few localities where it is filled with vertebrate
remains. (p. 134)
The principal component of the formation in western Alachua County
is faintly stratified and crossbedded, light-gray to bluish-gray, clayey
phosphatic sand which weathers red to orange and is coherent but
rarely well indurated. Layers and lenses of blue to gray clay are
found interbedded with the sands but are not common. A minor but
economically significant constituent of this formation is the plates
and boulders of secondary hard-rock phosphate that commonly
underlie the phosphatic clayey sands or are interbedded with them.
The hard-rock phosphate consists of fragments, plates or rounded
masses of dense, often botryoidal and finely banded apatite with
common irregular, discontinuous cavities. Color is extremely variable
but is often some shade of brown, blue, gray or white. In addition to
the hard-rock phosphate, other minor constituents of the Alachua
Formation are silicified residual boulders of the Crystal River Forma-
tion, Suwannee Limestone, silicified wood and occasionally phos-
phatized limestone of the Crystal River Formation (genetically as-
sociated with the hard-rock phosphate).


The thickness of the Alachua Formation is extremely variable
due to the uneven nature of the upper surface of the underlying
Crystal River Formation but probably does not exceed 50 feet as
seen in several deep abandoned phosphate pits northwest of New-
Numerous authors have discussed the origin of the hard-rock
phosphate and the age of the Alachua Formation. Thorough reviews
of previous work may be found in reports by Sellards (1913), Ketner
and McGreevy (1959), Espenshade and Spencer (1963), Teleki
(1966) and Olson (1972). Sellards (1913) concluded that the Haw-
thorne Formation, and probably some later units, were once con-
tinuous over the present hard-rock phosphate deposits:
The disintegration of these formations supplied the miscellaneous
materials of which the deposits are made up. The mixing of thle ma-
terials was brought about in part by stream action, which has resulted
in a reworking and reaccumulation of the residual material from these
formations, and in part by the local irregular subsidence such as is
constantly going on in a limestone country The fossils now found
in the formation include those that were residual from the formations
that have disintegrated, and those that were incorporated in connection
with the reworking and renacumulation of the materials. The phosphate
and flint boulders are formed chemically through the agency of ground
water. (p. 37-38)
Probably the majority of subsequent researchers have concurred
with Sellards as to the residual origin of the Alachua Formation in-
cluding Cooke (1945), Ketner and McGreevy (1959), Espenshade
and Spencer (1963), Teleki (1966), and Olson (1972).
In earlier sections of this report, geomorphic and stratigraphic
evidence was presented to indicate that the Middle Miocene Haw-
thorne Formation once covered the entire area of Alachua County.
Some evidence was also presented to indicate that Upper Miocene
sediments were deposited over the Hawthorne Formation. Teleki
(1966) found that the phosphatic clayey sands of the Alachua For-
mation were derived from Upper Miocene sandy clays that underlie
the Brooksville Ridge, especially in its southern portions. Some of
these sands may also be derived from disintegration of the Haw-
thorne Formation. There may have been some movements of the
Ocala uplift in Late Miocene to Middle Pliocene time which elevated
western Alachua County and caused the uplift to be breached. There
is also some evidence from a vertebrate fossil locality in Manatee
County (Webb and Tessrran, 1967, 1968) that sea level during a
portion of the Middle Pliocene may have approached its present
level. Alachua County was above sea level, and its western portion


was undergoing erosion and karst development in the Middle Pliocene
as evidenced by the McGehee Farm site and several Hemphillian
vertebrate sites exposed in quarrying operations at Haile (Florida
State Museum vertebrate paleontology collections identified as Haile-
VB, VI and X). The conclusion is inescapable that in western Alachua
County during the Middle Pliocene, sediments of the Hawthorne
Formation and overlying Upper Miocene beds (in addition to the
Suwannee Limestone and Crystal River Formation previously dis-
cussed) were undergoing erosion and redeposition in the Brooksville
Ridge area. These sediments were deposited primarily under ter-
restrial conditions in sinks, streams, ponds, and lakes with possibly
some estuarine influence during a portion of their deposition.
Several authors have noted that deposition of the sediments of
the Brooksville Ridge were controlled by the Ocala uplift because
this ridge follows roughly the stratigraphically highest portions of
the area of outcrop of Eocene limestones. After the highest portion
of the uplift was breached (probably in the Early Pliocene), the
eastern, and possibly the western, limit of deposition of the Alachua
Formation was probably controlled by the retreating erosional scarp
of the Hawthorne Formation.
The Alachua Formation is here considered to be Middle Pliocene
in age as indicated by the presence of Middle Pliocene (Hemphillian)
vertebrate fossil deposits. Webb (1967) stated:
The sediments containing terrestrial vertebrates of Pliocene age are
of two fundamental types: phosphatic sand and sandy montmorillonitic
clay. Unreworked Pliocene land vertebrates have been found in no
other kinds of sediments in eastern United States. (p. 11-12)
Two examples of this are given; one is the type locality of the Alachua
Formation (Mixson's Bone Bed, northeast of Williston where fossils
are in a sandy clay matrix), and the other is the McGehee Farm
site where the fossil-bearing matrix is the typical phosphatic sand
of the Alachua Formation. The several isolated deposits of pre-
Pliocene age found in western Alachua County are not considered
to be part of the Alachua Formation. Numerous Pleistocene deposits
preserved in sinkholes on the limestone plain are not included here
in the Alachua Formation as they are localized, isolated and not
lithologically consistent or mappable.

The Alachua Formation crops out along the western edge of
Alachua County in the area between High Springs and Newberry
and between Newberry and Archer (see geologic map, Appendix 4).


In the southwestern corner of the county, the Alachua Formation is
covered by the Pleistocene Brooksville Ridge sand and is exposed in
only a few abandoned hard-rock phosphate mines. Exposures are
numerous in the over 50 abandoned hard-rock mines in the area
around and northwest of Newberry. Phosphate mining in this area
reached a peak early in the 20th century and declined after World
War I. None of the mines are currently active and most have been
abandoned for over 50 years. U.nweathered exposures of the Alachua
Formation are, therefore, almost nonexistent. A majority of the
mines have been used as garbage dumps, all are badly overgrown,
and exposures are generally highly weathered and slumped. Only a
few significant localities will be mentioned here.
Locality Al: McGehee Farm vertebrate fossil locality approximately
3 miles north of Newberry. The Middle Pliocene vertebrates at
this site are included in a matrix of typical Alachua Formation
phosphatic clayey sands and represent basically a terrestrial
fauna with some estuarine influence (Webb, 1967). Several
specimens of the Oligocene echinoid Rhyncholampus gouldii
were found in the phosphatic sands.
Locality A2: Small sinkhole in the SW corner, Sec. 18, T.9S., R.17E.
This is the only locality where hard-rock phosphate was found
in place at the surface as opposed to being found in the aban-
doned phosphate mines. Numerous cobbles and boulders of
light-blue and gray hard-rock phosphate and some phospha-
tized limestone were found in this small sinkhole. Surface ex-
posures are rare in this area since phosphate mines were lo-
cated in areas with the least amount of overburden.
Locality A3: Residual silicified boulders in a road cut in the NE/4,
SE/4, Sec. 21, T.10S., R.17E. These boulders were found in
Alachua Formation sediments and were encountered while
grading the road. Several fragments of highly weathered, com-
pressed, and silicified coral were found. These fragments may
be conspecific with the common silicified coral in the Haw-
thorne Formation, and if so, are an indication that Hawthorne
Formation sediments were in fact incorporated into the Alachua
Formation at the time of deposition.
Measured geologic sections of the Alachua Formation will not be
given here due to the highly weathered nature of the sediments
commonly seen in abandoned phosphate mines. Several sections are
given for Gilchrist County mines by Purl, Yon and Oglesby (1967,
p. 100-114). Well W-4929 (Appendix 2) passed through 28 feet of
Alachua Formation sediments. Weathered outcrops of the unit may


be seen in several abandoned mines particularly in Sections 18, 30
and 31, T.9S., R.17E., northwest of Newberry.


Short discussions of two units, the Brooksville Ridge sand and
the Okefenokee Terrace deposits were given earlier in the section
on Marine Terraces an Quaternary Geology. They are considered
further here.
Underlying the Northern Highlands Plateau north of Gainesville
is a surficial unit containing material of at least two different ages.
Upper Miocene sediments, similar to those found northeast and east
of the region studied, extended into the area underlying the Plateau
and wedge out to the west. These sediments may once have been
continuous across the county as discussed earlier under the heading
Residual Late Miocene Deposits. Pliocene vertebrate fossils have
been found in numerous localities in and around Gainesville where
streams are eroding the unit. Several of these sites were listed by
Dall and Harris (1892) in their discussion of the Alachua clay. These
Pliocene sediments are not included here in the Alachua Formation
(after Pirkle, 1956b, p. 232). They are interpreted by Brooks (1966,
p. 42) as being Pliocene fluvial deposits. These sediments were not
extensively investigated in this study and the boundaries on the
geologic map (Appendix 4) for the Okefenokee Terrace deposits are
only approximate. These sediments are discussed by Pirkle (1956b)
and Brooks (1966, p. 40-43 and 1967, p. 17).
The southwestern corner of Alachua County is covered by a layer
of Pleistocene sands. For convenience the unit will be referred to as
th Brooksville Ridge sand (see geologic map, Appendix 4). The unit
was differentiated by Teleki (1966) who found it to be derived from
the underlying Alachua Formation. Espenshade and Spencer (1963)
mapped the areas of thick deposits of sand found in the Brooksville
Ridge. The Brooksville Ridge sand as seen in western Alachua
County is composed of lightbrown, cross-bedded, moderately well
sorted, rounded, frosted, medium to fine grained quartz sand. Tree
roots and charcoal fragments are common, and there are occasional
lenses of pure white fine-grained, well-sorted quartz sand. Pirkle
(1956) interpreted the sand to be aeolian in origin and of Pleisto-
cene age. The sand is best exposed in the county sanitary landfill
southwest of Archer (Sections 19 and 30, T.11S., R.18E.) where 15
to 20 feet of this unit is exposed (Figure 21). The sand is also well


exposed around Watermellon Pond in the northwest portion of
T.11S., R.17E.

Figure 21. Alachua County Sanitary Landfill southwest of Archer (Sections 19
and 30, T. 11 S., R. 18 E.). This landfill is located in the Brooksville
Ridge sand.

There are several localities in western Alachua County where
well-stratified sands interbedded with thin clayey layers are found.
These sands are composed of clean white to light brown quartz sands
that are from 1 to 4 inches thick separated by thin (usually less than
0.5 inch) layers of reddish-brown sandy clay. These sands were inter-
preted by Matson (1915, p. 27) and Espenshade and Spencer (1963,
p. 13) as being Pleistocene marine terrace deposits. Espenshade and
Spencer (1963) noted that these sand deposits occur generally be-
tween 50 and 90 feet in elevation, overlying eroded phosphatic sands
in the area of hard-rock phosphate. This rather distinctive type of
Pleistocene sand deposit was found in two localities in the western
part of Alachua County. Sixteen feet of well-stratified sand inter-
bedded with thin clayey layers is found overlying the Crystal River
Formation and Alachua Formation in a borrow pit northeast of
Archer (SE corner, Sec. 36, T.10S., R.17E.). About 10 feet of this
sand is preserved in a solution pit in a quarry (Figure 22) southeast
of Newberry (SW corner, SE/4, Sec. 8, T.10S., R.17E.).


Figure 22. Solution pipe, partially filled with Pleis-
tocene sand, in a quarry southeast of
Newberry (SW corner, SE/4, Section 8,
T. 10 S., R. 17 E.).

At several localities along the Santa Fe River, a fresh-water marl
has been observed. This marl attains a thickness of up to 6 feet and
contains very abundant Goniobasis sp. It is probably of Late Pleisto-
cene to Recent age and has been observed as much as 10 feet above
the present water level of the Santa Fe River.


Limestone and phosphate in quantity have been produced from
mines in western Alachua County. Ground water from the Floridan
Aquifer is an abundant and important resource, and both ceramic
clay and fullers earth deposits have been located but not exploited.


Sand, primarily for fill, has been taken from numerous shallow pits
throughout the county. Several limestone quarries are currently in
operation. The primary use for limestone quarried in western Alachua
County is for use in road building. However, at least one pit in the
Arredondo area is reported to have been worked for the manufacture
of quicklime (Mossom, 1925).
In the early part of this century, Alachua County produced sig-
nificant amounts of hard-rock phosphate. No mines are currently
operating though considerable amounts of recoverable phosphate
exist in the area, especially in the smaller sizes of pebbles and phos-
phatic sand and clay. Such soft phosphate has been profitably mined
in Gilchrist County (Puri et al., 1967). Pirkle (1957b) discussed the
economic possibilities of a pebble phosphate concentration at the
top of the Hawthorne Formation north of Gainesville.
Fullers earth clays occur in the Hawthorne Formation at the
Devil's Mill Hopper but do not occur in quantities sufficient for
mining to be economically feasible. Several clay deposits were investi-
gated by Bell (1924). He found that clay in west Gainesville is
suitable for only a low grade of common brick. In an investigation of
ceramic clay possibilities, Hickman and Hamlin (1964) analyzed
samples from 10 core borings along SR-26 west of Gainesville. Only
one hole showed commercial potential.
Possibly the most important resource of western Alachua County
is ground water. Adequate supplies of water may be obtained by
relatively shallow wells in most of the area studied. The water re-
sources of Alachua County have been reported by Clark et al. (1964a
and b).


Appendix 1.

Chart Summary of Selected Wells






I _Ti_

185GRD e185


56 --

164 -108

210 -318 615 -933 465 -1398 390 -1788




W-1486 168DF 168 l"-0 8- 190 -182 225 -407 525 -932 490 -1422 340 -1762 0opleI
1- 1,0,



97 60

37 130

-93 80 I--

210 -173


te Cenozoic


W-2580 136GRD 136 145 -9 5 14 Oligocene

W-3334 155GRD 145 100 -- -- 55 110 -55 100 -- 210 -155 Lower Ocala

W-3588 173GRD 173 30 -- 143 High top of Ocala

W-3634 77DF 77 30 -- -- 47 155 -108325 -433 460 -893 550 -1443 385 -1928 Coplete Cenozoic
S section
W-3740 76GRD 76 5 -- -- 71 25 46 45 1 60 130 59 ;110 -169 Inglis Ls.Differen-
----- -- tiated
W-3904 151GRD 151 90 -- -- 61 120 -59 90 -- 210 -149 Lower Ocala

W-4076 75GRD 75 50 -- -- 25 90 -70 60 150 -130 1257 -387 Lower Ocala

W-4929 76GRD 76 42 -- -- 34 -- -- 80 46 100 -146 _hin Ocala Section

Elevations are to a base line of sea level.

Appendix I. Chart Summary of Selected Wegs







Abbreviations used in Chart

DF . .......... Drill Floor
GRD . .. .......... .Ground elevation
E ..... .. ........ Elevation
T ..... . .... . Thickness
S...... .. ... .... ....... Hawthorne Formation O
S . . . . .... ... Suwannee Limestone
CR . . . ...... Crystal' iver Formation
W .. .. .. .. . . Williston Formation
I . .. ..... ... .. ...... Inglis Formation
AP. . . . . Avon Park Formation
LC. . . . .. . Lake City Limestone
0 . . . . . Oldsmar Limestone
CK. ...................... Cedar Keys Formation




W-324 Gainesville Municipal Airport #1.
Sec. 14, T.9S., R.19E., 700 ft. from E. line, 525 ft. from
N. line.
Elevation: 185 ft. Ground elevation.
Total Depth: 447.5 feet.
Log by: Stubbs & Applin.
0-95 No samples
Hawthorne Fm. Miocene
95-97 Soft gray limestone.
140-150 Blue clay with phosphatic pebbles.
150-160 Gray clay with phosphate pebbles.
160-169 Soft gray limestone with fragments of limestone and
Suwannee Limestone Oligocene
169-184 White chalky and calcic limestone showing fragments
of molds of macro-fossils. A few specimens of Coski-
nolina sp. and Valvulammina sp. and several species of
smaller foraminifers common to phases of the Oligocene
in parts of Florida.
184-190 Fragments of light gray hard limestone.
Ocala Limestone Upper Eocene
190-225 White fossiliferous limestone and clear quartz sand.
Some Ocala fossils present.
225-245 White and light gray fossiliferous limestone. Fossils
usually badly worn and broken. Fragments of Lepido-
cyclina ocalana and Operculina ocalana fairly common.
245-270 White and light gray fossiliferous limestone. Heteroste-
gina ocalana fairly common. Pseudo-phragmina floridana
270-335 White to light gray fossiliferous limestone. Lepidocyclina
ocalana and other forams common.
335-350 As above. Operculinoides wilcoxi present.
Lower Ocala Limestone Upper Eocene
350-440 A chalky and somewhat calcitic limestone composed
mainly of cemented molds of smaller foraminifers and
small fossil fragments. Amphistegina sp. cf. A. cubensis
present among others.


Avon Park Limestone Middle Eocene
441-447.5 Chalky limestone with many fragments of a brown and
grayish-brown hard irregular porous dolomite. No fossils.

W-1465 Tidewater Assoc. Oil Co., R. H. Cato #1.
Sec. 28, T.8S., R.18E.
Elevation: 112 ft. Drilling floor.
Total Depth: 3146 feet.
Log by: Chen.
Hawthorne Fm. Miocene
0-56 Phosphatic clayey sand.
Ocala Group Upper Eocene
56-220 Highly fossiliferous limestone with some chert and
Avon Park Limestone Middle Eocene
220-530 Very fine crystalline dolomite to calcic dolomite.
Lake City Limestone Middle Eocene
530-1045 Fossiliferous limestone to fine crystalline dolomite. Oc-
casional thin beds of black peat.
Oldsmar Limestone Lower Eocene
1045-1510 Fossiliferous limestone to fine crystalline dolomite.
Cedar Keys Formation Paleocene
1510-1605 Microcrystalline gypsiferous dolomite interbedded with
dolomitic anhydrite.
1605-1900 Light gray to brown slightly porous to rather dense and
fragmental gypsiferous, fossiliferous and microcrystal-
line dolomite.
Top, Upper Cretaceous 1900 feet

W-1486 Tidewater Assoc. Oil Co., Josie Parker.
Sec. 33, T.7S., R.19E.
Elevation: 168 feet. Drilling floor.
Total Depth: 3218 feet.
Log by: Chen.
Hawthorne Fm. Miocene

Phosphatic clayey sand.



Ocala Group Upper Eocene
160-330 Fossiliferous limestone.
330-350 Dolomite, very fine to fine crystalline.
Avon Park Formation Middle Eocene
350-575 Fossiliferous limestone to fine crystalline dolomite.
Lake City Limestone Middle Eocene
575-1100 Fossiliferous limestone to fine crystalline dolomite. Oc-
casional thin beds of black peat.
Oldsmar Limestone Lower Eocene
1100-1590 Fossiliferous limestone to fine crystalline dolomite.
Cedar Keys Formation Paleocene
1590-1930 Microcrystalline gypsiferous dolomite and dolomitic
Top, Upper Cretaceous 1930 feet

W-2447 City of Gainesville.
NE/4, SE/4, Sec. 16, T.10S., R.20E.
Elevation: 96.97 ft. Ground elevation.
Total Depth: 370 feet.
Log by: Vernon.
Hawthorne Fm. Miocene
0- 5 Fine to medium quartz sand to a very sandy apatitic
5-10 White quartz and tan phosphorite in colloidal apatite
10 30 Tan, fine to medium quartz and phosphoritic sand.
30-60 Fine to medium quartz sand and phosphoritic sandy
clay. Some Fuller's earth clay.
Ocala Limestone Upper Eocene
60 70 Tan to gray, hard, dense, cryptocrystalline limestone.
70-80 Cream, hard, fairly porous, granular limestone.
80 96 Cream, soft, porous, coquina limestone.
96 -140 Cream, soft, porous, large foraminiferal coquina in a
chalky to granular calcite matrix. Lepidocyclina ocalana,
Heterostegina ocalana.
140 190 Limestone as above, somewhat more granular and fewer


Moodys Branch Formation (Lower Ocala Group) Upper Eocene
190-240 Light gray to cream colored, hard, granular, porous,
fragmental, marine limestone. Camerina vanderstocki,
C. moodybranchensis. Amphistegina pinnarensis, some
echinoid fragments.
240 270 Cream, hard, porous, granular fragmental marine lime-
stone. Periarchus lyelli fragments.
Avon Park Limestone Middle Eocene
270 290 Cream, granular, soft, porous limestone and quartz sand.
290 310 Tan, finely crystalline, silty textured, hard, dense dolo-
310 350 Brown, crystalline, sugary, vesicular, hard, dense dolo-
350 370 Hard dense dolomite with flecks of peat.

W-2580 Florida Forest Service.
SW/4, SW/4, Sec. 22, T.7S., R.19E.
Elevation: 135.97 feet. Ground elevation.
Total depth: 175 feet.
Log by: Hendry.
Surficial Sand and Soil
0- 15 Light gray, fine to medium grained, clear
subangular to subrounded, quartz sand.
Hawthorne Formation Miocene

to frosted,

15-35 Greenish to dark gray, waxy, blocky clay and sandy
blocky clay. Some montmorillonitic clay and phos-
35 40 Sand and light gray, montmorillonitic type clay; much
40- 75 White sand, fairly well sorted, medium grained; scattered
phosphorite grains, some clay as above.
75-95 Green, blocky, waxy, sandy clay; buff-colored phos-
phorite pebbles; small percentage of pyrite.
95- 130 Fine to medium grained sand; some phosphorite and
montmorillonitic clay.
130 140 Fine to medium grained sand with fragments of sandy
limestone. Traces of finely crystalline, cream colored
limestone. Echinoid plates and spines; ostracod valve,
sharks teeth.


140- 145 Gray to buff colored finely crystalline, hard, dense,
sandy limestone; echinoid spine.
Suwannee Limestone (?) Oligocene
145 150 White to very light-cream colored, cryptocrystalline,
dense, limestone. Echinoid spines.
Ocala Limestone Upper Eocene
150 155 White fine grained dense porous, somewhat chalky fos-
siliferous limestone. Nummulites vanderstoki, Bryozoa,
echinoid spines miliolids.
155 -175 White fine grained chalky fossiliferous limestone. Nu-
merous foraminifera.


W-3334 University of Florida
SW/4, SE/4, Sec. 6, T.10S., R.20E.
Elevation: 155.62 feet. Ground elevation.
Total depth: 450 feet.
Log by: Hendry.
Surficial sand and soil
0 10 Sand, gray to brown, mostly medium grained, sub-
angular to subrounded, clear to frosted, in clay matrix.
Hawthorne Fm. Miocene
10 20 Light green, waxy, blocky, silty to sandy clay.
20-40 Sand; white, fine grained, subangular, clear, with white
to cream, rounded shiny phosphorite grains.
40- 60 Cream colored, fairly soft, finely crystalline, sandy phos-
phoritic argillaceous limestone.
60 70 Mostly calcareous clay, cream to light green.
70- 75 Limestone, gray, finely crystalline, slightly sandy, dense,
hard. Some sandy clay.
75- 85 Limestone, cream colored, hard, finely crystalline, dense,
very sandy and slightly phosphoritic.
85-90 Limestone, cream, hard, crypto to finely crystalline,
dense, sandy. Some manganite dendriticc) and iron
Crystal River Formation Upper Eocene
100 145 Limestone, cream, soft, crypto to very finely crystalline,
fossiliferous (coquinoid), porous. Small forams and echi-


noid spines are abundant. Lepidocyclina, Operculinoides,
145 165 Limestone, cream, hard, mostly larger forams in a chalky
matrix. Very abundant Camerina.
165- 185 Limestone, cream, soft, chalky to granular, very fossili-
ferous. Pecten fragments.
185 210 Limestone, cream, hard, chalky to granular, fossiliferous.
Rotalia cusmani and Peronella sp. present.
Moodys Branch Fm. (Lower Ocala Group) Upper Eocene
210 215 Limestone, cream, hard, porous, very fossiliferous. Am-
phistegina pinarensis abundant. Many Camerina.
215--290 Same, with limestone becoming chalky or argillaceous
and grayish.
290 310 Same, and very hard and granulated.
Avon Park Fm. Middle Eocene
310 330 Dolomite, brown, very finely crystalline, dense, hard.
330 415 Dolomite, brown, micro-moldic porosity, finely crystal-
415 450 Dolomite, buff to light brown, dense, nonporous, hard,
very finely crystalline.
W-3588 University of Florida
SW/4, SW/4, Sec. 9, T.9S., R.19E.
Elevation: 173 feet. Ground elevation.
Total depth: 170 feet.
Log by: Vernon.
Hawthorne Fm. Miocene
0 30 Phosphoritic sandy clay. Also sandy, phosphoritic lime-
Crystal River Formation Upper Eocene
30- 170 (Ten Samples) Limestone, cream, fragmental, marine,
large foraminiferal coquina in a pasty, soft porous ma-
trix. Lepidocyclina ocalana.
W-3634 The Texas Company, A. M. Creighton #1.
Sec. 16, T.11S., R.19E.
Elevation: 77.26 feet. Drill Floor.
Total depth: 3524 feet.
Log by: Chen.


0--30 Miocene and younger
30-185 Ocala Group Upper Eocene
185-510 Avon Park Limestone Middle Eocene
510-970 Lake City Limestone Middle Eocene
970-1520 Oldsmar Limestone Lower Eocene
1520-1905 Cedar Keys Limestone Paleocene
1905- Top, Upper Cretaceous


W-3740 City of Newberry.
SW/4, SE/4, Sec. 4, T.10S., R.17E.
Elevation: 76.71 feet. Ground elevation.
Total depth: 250 feet.
Log by: Puri.
0 5 Sand, white medium grained.
Crystal River Formation Upper Eocene
5 -25 Limestone, white, chalky with Lepidocyclina ocalana
and vars., Heterostegina ocalana, Discocyclina citrensis,
Spiroluculina sp.
25 30 Limestone, pale to white, granular, with same fauna as
above plus Operculinoides ocalanus.
Williston Formation Upper Eocene
30- 55 Limestone, pale, granular, with Fabiania vaughani, Am-
phistegina pinarensis var., and Camerina moodybran-
55-75 Limestone, pale, granular, coquina of Camerina moody-
Inglis Formation Upper Eocene
75-135 Limestone, pale granular, miliolid coquina with frag-
ments of echinoids. Some limonite and dolomite near
bottom of unit.
Avon Park Limestone Middle Eocene
135--230 Dolomite, grayish brown, dense; fragments of miliolitic
limestone, limonite and fragments of Periarchus sp.
(Cavings from above)
230--245 Approximately 50% honey-colored dolomite; fragments
of cream colored dolomite, limonite, and sand.


Lake City Formation Middle Eocene
245 250 Limestone, cream colored micro-coquinoid, with Astero-
cyclina monticellensis and molds of Mollusca.

W-3904 General Electric Corporation.
NE/4, SW/4 Sec. 20, T.8S., R.19E.
Elevation: 151 feet. Ground elevation.
Total depth: 427 feet.
Log by: Yon.
Hawthorne Fm. Miocene
0 --75 Clay, phosphoritic, cream colored, very sandy (coarse
to fine).
75- 90 Limestone, sandy, tan to cream, finely crystalline, hard,
Crystal River Formation Upper Eocene
90- 210 Limestone, rare chert, chalky, light cream, finely crystal-
line, soft to medium hard, intergranular porosity. Abun-
dant microfossils. Lepidocyclina ocalana, Heterostegina
ocalana, Gypsina globula.
Lower Ocala Group Upper Eocene
210 300 Limestone, chalky, calcitic, light cream, finely crystal-
line, medium hard, granular with intergranular porosity.
Abundant microfossils. Camerina moodybranchensis.
Avon Park Formation Middle Eocene
300--310 Dolomite, brown to dark gray, finely crystalline, hard,
310- 360 Dolomite, cherty, dark brown, finely crystalline, pyrite
present, hard, dense, fossiliferous.
360- 400 Dolomite, tan, finely crystalline, granular, moldic and
intergranular porosity, cones.
400 427 Dolomite, tan, finely crystalline to granular, moldic and
intergranular porosity to dense.

W-4076 University of Florida, Central Power Plant.
300 ft. W. and 400 ft. S. of Power Plant, Sec. 7, T.10S.,
Elevation: 75 feet. Ground elevation.


Total depth: 700 feet.
Log by: Vernon.
Pleistocene (?) Sinkhole fill
0 20 Sand, fine to coarse, frosted to clear, subrounded quartz
in an organic clay matrix. Nodules of limonitic sand-
stone and thin beds at base.
20-30 Sand, fine to medium, clear quartz, with green clay
matrix and lenses. Ocala limestone and fossils, and light
gray phosphatic sand, rare phosphorite.
30-55 Sand and clay as above. Limestone fragments contain
Amphistegina pinarensis and therefore are probably
Williston or Inglis boulders or the well cuts a fault.
Crystal River Formation Upper Eocene
55 -70 Limestone, cream, loose coquina of large foraminifers,
very porous, definite Crystal River Formation.
70- 145 Limestone as above. Nummulites moodybranchensis.
Very contaminated by caving from above.
Lower Ocala Group Upper Eocene
145-160 Limestone, cream to light gray, granular, hard, inter-
granular porosity. Nummulites moodybranchensis.
160-170 Dolomite, brown, finely crystalline, hard, dense, peat
170--188 Limestone, tan to cream, soft, intergranular porosity,
188 205 Dolomite, tan to brown, finely crystalline, poorly porous,
hard, Periarchus fragments.
Avon Park Limestone Middle Eocene
205 225 Dolomite, tan to light gray, hard, dense, finely crystal-
line, coffee-colored chert.
225 255 Dolomite, gray to brown, subgranular to finely crystal-
line, micromoldic, hard.
255 270 Dolomite, tan, hard, dense, pasty.
270 320 Dolomite, brown, hard, tough, finely crystalline to sub-
granular, micromoldic.
320 -416 Dolomite, tan to yellow, soft, pasty, impervious. Beds
of similar dolomite, subgranular and streaks of micro-
moldic porosity.
416- 462 Dolomite as above and dolomite, gray, hard, dense, mi-
cromoldic seams, finely crystalline to pasty. Rare chert


Lake City Limestone Middle Eocene
462 475 Dolomite, brown, hard, dense, cryptocrystalline, coated
by peat stains and containing fragments of lignite.
475 491 Dolomite, as above and; brown, finely crystalline, micro-
moldic, hard, peat flecked dolomite.
491 597 Limestone, cream to light gray, soft, small foraminifers,
coquina in granular to pasty matrix. Dictyoconus ameri-
canus. Some lignite fragments.
597 628 Limestone, light gray, soft, fairly porous, granular, co-
quinoid. Some quartz sand. Some dolomite.
628 656 Dolomite, brown, hard, dense, finely crystalline, sugary.
656 700 Dolomite, brown, to very dark brown, micromoldic, sub-
granular to finely crystalline, sugary.
W-4929 U. S. Geological Survey.
SW/4, NW/4, Sec. 22, T.10S., R.17E.
Elevation: 76.27 feet. Ground elevation.
Total depth: 252 feet.
Log by: Clark et al., 1964, p. 57,112.
Pleistocene Terrace deposits
0 12 No sample
12 14 Sand, tan to light yellow, fine.
Alachua Formation Pliocene
14 20 Clay, sandy, gray.
20 30 Clay, reddish, sandy; white limestone.
30 35 Sand, tan, fine; dark blue clay.
35 38 Clay, yellow, sandy; fine sand layers.
38 42 Clay, reddish, sandy.
Ocala Group Upper Eocene

42 44 Limestone, white, soft, coquina; foraminifers; clay.
44 83 Limestone, white to cream colored, sandy, coquina, fora-
minifers, plus some hard, dense, tan limestone.
83 122 Limestone, yellow to tan, hard, foraminifers; sand, tan,
Avon Park Formation Middle Eocene
122 -127 Limestone, tan, dolomitic; foraminifers; limonite; sand,
white, quartz, fine.
127 151 Dolomite, brown, sugary textured; foraminifers; limo-
nite; clay; sand, white, quartz, fine.


151 152 Cavity.
152 -222 Dolomite, brown, calcareous; foraminifers; sand, white,
Lake City Limestone Middle Eocene
222 252 Limestone, grayish-green and tan, hard, dolomitic. Some
fossiliferous and some dense gray limestone.


Appendix 3

Location of Profiles and Localities

X '* C I( e =
n to CI I i o

o K

0 I

, |lnA%
E Elt'


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ul ~ln/r C



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to N
H\' Y^ ^O J-.


*s '"^*y iL &

General Highway Map, Alachua

r t. t 4 R s I r. o rI
4Scae in mies
Scale in miles


Well Location










Appendix 4


____________ 8 _____ 1 ____________ ___

I.... I I


" -

Ees Brooksville Ridge sand
Po Okefenokee Terrace deposits
Pa Alachua Formation
MHi Hawthorn Formation
Ecx Crystal River Formation

Ii t F ti


S+ I* ~* ~



l --, I .

! -1 -N1




Figures I 2. Spirulaea vernoni Richards.
1. Free surface of specimen, greater diameter 18.0 mm,
lesser diameter 15.0 mm, Florida State Museum cat. no.
3300. hypotype. Locality: Suwannee County. Suwan-
nee Limerock Co. Quarry, 2.5 miles south of O'Brien
and just west of State Highway 129. SE/4, NW/4, Sec.
32. T.5S., R.14E. This is the same quarry as that de-
scribed by Puri and Vernon, 1964, p. 93.
2. Cross section of specimen imbedded in limestone, great-
er diameter 13.3 mm, lesser diameter 10.7 mm, Florida
State Museum cat. no. 3301, hypotype. Locality: Lafay-
ette County. Quarry 0.5 miles west of bridge on Su-
wannee River and 0.5 miles north of State Highway
S-250. Approximately 2 miles west of Dowling Park.
NW/4, Sec. 6, T.3S., R.11E. Both figures taken from
Hoganson, 1972.