Stratigraphy of Parts 

of De Soto and 

Hardee Counties 

Florida

GEOLOGICAL SURVEY BULLETIN 1030-B

This report concerns work done on behalf 

of the U. S. Atomic Energy Commission 

and is published with the permission of 

the Commission

Stratigraphy of Parts 

of De Soto and 

Hardee Counties 

Florida

By M. H. BERGENDAHL

CONTRIBUTIONS TO THE GEOLOGY OF URANIUM

GEOLOGICAL SURVEY BULLETIN 1030-B

This report concerns work done on behalf 

of the U. S. Atomic Energy Commission 

and is published with the permission of 

the Commission

UNITED STATES GOVERNMENT PRINTING OFFICE, WASHINGTON : 1956
UNITED STATES DEPARTMENT OF THE INTERIOR 

Fred A. Seaton, Secretary

GEOLOGICAL SURVEY 

Thomas B. Nolan, Director

For sale by the Superintendent of Documents, U. S. Government.Printing Office 

Washington 25, D. C.
CONTENTS

Page

Abstract__________________________ 65

Introduction. ______________________________ - -- 65

Purpose and scope____________________ 65

Methods of investigation. ________________ __ 67

Culture....____________________________ - 67

Topography. _____________________________ 68

Drainage. _______________________ _. 68

Acknowledgments. ____________________________ ____ _ 68

Stratigraphy._____________________ _ 69

Miocene series.________________________________ _______ ___ 69

Hawthorn formation.________________________ _______ 69

Sand of late Miocene age__________________ _____________ 73

Miocene to Pliocene series_____________________________________ 79

Undifferentiated phosphatic sand and clay___________ .__ 79

Ph'ocene series__________________________ _ 84

Caloosahatchee marl_________________________________ 84

Pleistocene series.__________________________________________ 86

Deposits of Pleistocene age.________________________________ 87

Sediments of Recent age_____________________________________ 90

Mechanical analysis_____________________________________ 91

Geologic history__________________________________ 92

Miocene_________________________________________________ 92

Pliocene____________________________________ 93

Pleistocene._______________________________________________ 93

Recent.________________________________________________ 94

Economic considerations______________________ _____ 94

Literature cited.______________________________ _ 95

Index.______________________________________ 97

ILLUSTRATIONS

[All plates in pocket]

PLATE 1. Geologic map showing location of outcrops and drill holes in 

parts of Hardee and De Soto Counties, Fla.

2. Geologic sections through parts of Hardee and De Soto Counties.

3. Cumulative frequency curves of samples from 12 auger holes.

4. Classification of the upper Tertiary rocks in Florida, showing 

stratigraphic terms used by various authors.

in
IV CONTENTS

Page 

FIGURE 6. Index map of land-pebble phosphate district, Hardee and

De Soto Counties___________________________________ 66

7. Summary of exposed formations in Hardee and De Soto

Counties. _____________ __ ________ 70

8. Diagram showing general stratigraphic relations of the

formations in Hardee and De Soto Counties _____________ 71

,. 9. Sketch map and cross sections of borrow pit, 1.6 miles east of

Nocatee, De Soto County____----------_----___---_-_- 74

10. Sketch of section exposed along west bank of Peace River,

near Gardner, Hardee County________________________ 78

11. Plan and profile sketch of exposure along Horse Creek, at

bridge on Florida Route 72, De Soto County___________ 91
CONTRIBUTIONS TO THE GEOLOGY.OF URANIUM

STRATIGRAPHY OF PARTS OF DE SOTO AND HARDEE 

COUNTIES, FLORIDA

By M. H. BERGENDAHL

ABSTRACT

The late Cenozoic stratigraphy of part of central Florida immediately south of 

the land-pebble phosphate district was studied in detail to determine the southern 

limit of the economically important Bone Valley formation and its relations,with 

marine rocks of late Miocene and Pliocene age in south-central Florida. In addition, a reconnaissance-type appraisal of the phosphate and uranium resources of 

this area was desired. The upper Tertiary and Quaternary rocks were mapped, 

and the economic geology was studied in a general manner.

The Hawthorn formation, of early and middle Miocene age, is the oldest rock 

exposed. Undifferentiated phosphatic sand and clay of late Miocene to Pliocene 

age may be composed of: (1) the Bone Valley formation, (2) a combination of Bone 

Valley formation and residuum of weathered Hawthorn formation, or (3) residuum 

of the Hawthorn alone. The Bone Valley formation and residuum of the Hawthorn formation appear to be almost identical in cuttings from auger drilling in 

this area. It was neither feasible nor practical to map these two units separately. 

The undifferentiated phosphatic sand and clay interfingers with a marine sand of 

late Miocene age. The Caloosahatchee marl, of Pliocene age, is present in the 

southeast corner of the area investigated. It is apparent that the undifferentiated phosphatic sand and clay was undergoing subaerial erosion and reworking 

during deposition of the Caloosahatchee marl. Stratified sand and clayey sand 

containing scattered thin lenses of fresh-water limestone and marl of Pleistocene 

age are believed by the writer to be either flood-plain deposits or subaerial top-set 

beds of a delta made by the Pleistocene Peace River. Stream deposits of Recent 

age are present locally along the Peace River and its tributaries.

Bars and shoals in the Peace River south of Brownville, De Soto County, contain appreciable tonnages of low-grade "river-pebble" phosphate. The phosphate 

and uranium content of the undifferentiated phosphatic sand and clay in Hardee 

County is too low to be of economic significance.

INTRODUCTION

PURPOSE AND SCOPE

The results of one part of the investigations of the regional geology 

of central Florida by the U. S. Geological Survey are presented in 

this paper. Work was done on behalf of the Division of Raw Materials of the U. S. Atomic Energy Commission.

The area covered by this report is immediately south of the Florida 

land-pebble phosphate mmins; district (fig. 6).

65
66 CONTRIBUTIONS TO THE GEOLOGY OF URANIUM

82°______________________80°

26'

FIGURE 6. Index map of land-pebble phosphate district, Hardee and De Soto Counties.

Although the geology of Hardee and De Soto Counties is described 

in a number of reports (Matson and Clapp, 1909; Matson and 

Sanford, 1913; Cooke and Mossom, 1929; Cooke, 1945), several 

important problems remained unsolved. The southern extent of the 

Bone Valley formation, which contains the economic phosphate 

deposits, was never accurately mapped. The northern limit of the
STRATIGRAPHY, DE SOTO AND HARDEB COUNTIES, FLORIDA 67

Caloosahatchee marl, a fossiliferous shallow-water marine rock of 

Pliocene age that is present throughout southern Florida, was not 

precisely determined.

This investigation was conducted for two reasons: (1) to clarify 

the late Cenozoic stratigraphy south of the land-pebble phosphate 

district, particularly the relations of the Bone Valley formation with 

the Caloosahatchee marl; (2) to appraise the potential economic 

value of the area for phosphate and uranium.

METHODS OF INVESTIGATION

The area mapped in Hardee and De So to Counties is a strip 42 

miles long and 15 to 17 miles wide, roughly parallel to the Peace 

River (pi. 1). It includes about 700 square miles within the approximate boundaries of 27°2' to 27°39' north latitude and 81°40' to 82°3' 

west longitude. Gardner, which is near the center of the area, is 

about 58 miles (airline) southeast of Tampa and about 50 miles 

(airline) south of Lakeland.

The region is of such low relief that exposures are limited to the 

banks of streams and to shallow borrow pits. In addition, a mantle 

of surficial alluvium and wind-blown sand effectively conceals the 

older sediments. Less than 40 outcrops were found; the maximum 

section was 16 feet thick. A power auger, mounted on the rear of a 

4-wheel-drive truck, was used to obtain more detailed subsurface 

information at 92 localities. In general, holes were drilled at intervals 

of 1 to 2 miles along the rights-of-way of state and county roads. 

In addition, well logs and limestone cores from the U. S. Atomic 

Energy Commission contract drilling in this area were studied.

Topographic maps for this region were not available when field 

work was in progress. Planimetric county road maps, published on 

a scale of 1:125,000 by the Florida State Road Department, were 

used as a base for geologic mapping.

Altitudes of outcrops and drill holes were obtained by aneroid 

barometer traverses. It was possible during traverses to visit U. S. 

Geological Survey and U. S. Coast and Geodetic Survey bench marks 

within time intervals of less than 10 minutes. These elevations 

should be accurate to within 5 feet.

The period May through part of September 1953 was spent in the

field.

CULTURE

The major towns in the area are Wauchula (population 2,872), the 

county seat of Hardee County, and Arcadia (population 4,764), the 

county seat of De Soto County. U. S. Highway 17, which passes 

through Wauchula and Arcadia, is the principal north-south highway 

(pi. 1). State Highways 70 and 72 link Arcadia with Sarasota, on
68 CONTRIBUTIONS TO THE GEOLOGY OF URANIUM ;

the west coast, and with Sebring to the east. In De Soto County 

and southern Hardee County, cattle raising is the chief vocation. 

In northern Hardee County, the well-drained sandy soil is adaptable ' 

to orange groves and truck farming.

TOPOGRAPHY

The area includes two natural topographic subdivisions the Central Highlands, and the Coastal Lowlands (Cooke, 1939, p. 14). The 

northern part of Hardee County is within the Central Highlands. 

The topography is gently rolling, and altitudes generally range be- s 

tween 90 and 150 feet.

Immediately south of Zolfo Springs and Ona, the Central Highlands 

give way to the prairie country of the Coastal Lowlands. This area is 

a conspicuously flat plain, sloping slightly to the south. Altitudes 

range from 35 to 70 feet. In southern De Soto County the banks of 

the Peace River are less than 20 feet above sea level. The water table 

is close to the surface in this region, and many temporary shallow ponds 

appear during the rainy season.

DRAINAGE

The area is drained principally by the Peace River, which flows 

southward from its source in central Polk County for about 70 miles 

to Charlotte Harbor, near Punta Gorda, in Charlotte County. Major 

tributaries in Hardee and De Soto Counties are Payne's Creek, Charlie 

Apopka Creek, Joshua Creek, Horse Creek, and Prairie Creek. 

Intense rainfall during the summer and fall often causes the stream 

levels to rise 15 to 20 feet. During such periods, pastures adjacent to 

the streams are flooded for weeks at a time, and occasionally bridges 

are swept away. Outcrops are submerged by swollen streams, dirt 

roads are impassable, and drilling is difficult because of the flooded 

roadside conditions.

Streams are degrading at present. At many points along the Peace 

River and Charlie Apopka Creek, the banks are vertical. PrePleistocene phosphatic formations are being eroded, and the phosphate 

is being redeposited in shoals and bars along the lower reaches of the 

streams.

ACKNOWLEDGMENTS

Jean Hough identified the vertebrate fossils, and F. S. MacNeil 

examined and identified collections of invertebrate fossils. Radiometric analyses for percent equivalent uranium were made by B, A. 

McCall. Anthony Cerkel assisted the writer in the field.
STRATIGRAPHY, DE SOTO AND HARDEE COUNTIES, FLORIDA 69

STRATIGRAPHY

MIOCENE SERIES 

HAWTHORN FORMATION

The term "Hawthorn formation" has a complex history in Morida 

geology. It is essential that at least a brief review be given here.

Originally, the name "Hawthorne" was given by Dall (1892, p. 107) 

to the phosphatic limestone believed to be of "older" Miocene age 

(pi. 4) near the town of Hawthorne in Alachua County. Younger 

than the Hawthorne "beds", but still of "older" Miocene age, were the 

Tampa, Chipola, and Alum Bluff "beds", which were assigned by Dall 

(1892, p. 112) to the Tampa group (pi. 4). Later, due to a readjustment of the Oligocene-Miocene boundary, the Tampa group was 

regarded as Oligocene by Dall and others.

Matson and Clapp (1909, p. 67-69) combined rocks of the upper 

Oligocene into the Apalachicola group, which consisted of the following 

four formations: Tampa, Chattahoochee, Hawthorne, and Alum Bluff

(Pi. 4).

Matson and Sanford (1913, p. 87-88) shortened the name "Hawthorne" to "Hawthorn." They (Matson and Sanford, 1913, p. 145) 

believed that the land-pebble phosphate deposits lie upon an eroded 

surface of the Alum Bluff formation.

According to Sellards (1915, p. 34-35), the Alum Bluff formation 

was the parent rock from which the land-pebble phosphates were 

derived. Sellards (1916, p. 91-92) later introduced evidence of a 

Miocene vertebrate fauna in the Alum Bluff formation. The opinion 

that the Alum Bluff formation should be considered Miocene was 

generally accepted by later workers (pi. 4).

Gardner (1926, p. 1-2) recognized three distinct marine faunas of 

Miocene age, and, on the basis of these faunas, she raised the Alum 

Bluff to the rank of a group divided into three formations, each of 

which was characterized by a separate fauna. In descending order 

these were: Shoal River formation, Oak Grove sand, and Chipola 

formation (pi. 4).

Cooke and Mossom (1929, p. 98) retained Gardner's Alum Bluff 

group but reinstated the Hawthorn formation as a lateral equivalent 

in peninsular Florida of the Alum Bluff group in western Florida. 

Within the Hawthorn formation, Cooke and Mossom (1929, p. 115) 

included the earlier Alum Bluff formation of Matson and Clapp (1909, 

p. 91) and the original Hawthorne "beds", the Manatee River marl, 

the Sopchoppy limestone, and the Jacksonville limestone of Dall. In 

general, Cooke (1945, p. 144) retained this classification, but he

378283 5C
70 CONTRIBUTIONS TO THE GEOLOGY OF URANIUM

tentatively transferred to the Duplin marl some beds of late.Miocene 

age tbat Cooke and Mossom (1929, p. 115) assigned to the Hawthorn 

formation.

The Alum Blujf-Hawthorn equivalence has survived to the present; 

however, current views do not all agree on the age of the Alum Bluff 

group. According to F. S. MacNeil (written communication, Sept. 

1955), "The Chipola, the basal formation of the Alum Bluff group, is 

regarded by some as late early Miocene, by others as early middle 

Miocene."

The term "Hawthorn formation" as used in this report includes all 

marine rocks in central and southern peninsular Florida that are 

younger than the Tampa limestone, of early Miocene age, but older 

than the lowermost sediments of late Miocene age (fig. 7).

Stream terraces and bars

Mostly gray to white quartz sand, containing varying percentages of phosphate nodules. Thickness 0-28 ft. Economic 

value: Source of river-pebble phosphate

Pleistocene deposits

Brown quartz sand and clayey sand, with scattered thin lenses 

of blue-gray clay. Sand is locally crossbedded. Lentils 

of fresh-water limestone are included. Thickness 0-20 ft. 

Economic value: Limestone is'used for road fill

Caloosahatchee marl 

Gray to blue-gray quartz sand, slightly 

clayey in places. Abundant marine 

fauna forms a shett bed locally. Thickness 0-20 ft. Economic value: Use as 

road fill, when shells are abundant

Sand of late Miocene age 

Dark-green to light-gray quartz sand, 

with few phosphate nodules. Contains a characteristic marine fauna. 

Thickness 0-40 ft. Economic value: 

Use as road fill, when shells are abundant

Bone Valley formation 

Mostly variegated shades of red, gray, 

brown, and blue. Phosphate nodules 

and pellets usually dominant constituent. Quartz sand, day-size material 

may be abundant in places. Vertebrate remains are locally conspicuous. 

Thickness 0-35 ft. Economic value: 

Possible source of-land-pebble phosphate and uranium

Hawthorn formation 

Light-gray to buff phosphatic, silty, 

sandy limestone. Casts of marine invertebrates in upper few feet. Thickness unknown in this area. Economic 

value: None in this area

Weathered residuum of

Hawthorn formation 

Phosphate nodules, sand, day; similar 

to Bone Valley formation. Thickness 

unknown. Economic value: Possible 

source of land-pebble phosphate and 

uranium

FIGURE 7. Summary of exposed formations in Hardee and De Soto Counties.

Lithology. As seen at outcrops along streams in this area and in the 

phosphate mines to the north, the Hawthorn formation is a gray to 

cream, locally buff-colored limestone. Stratification is indistinct and, 

hi places, is marked by concentrations of phosphate grains in beds or 

lenses. Commonly, the Hawthorn formation is consolidated; locally, 

it is indurated.

Fine-grained quartz sand, quartz silt, clay-size particles, phosphate 

nodules, and calcium carbonate are the chief constituents. Magnesium carbonate is usually a minor constituent, but it may be present 

locally hi sufficient quantity to make the formation dolomitic. Indi-
STRATIGRAPHY, DE SOTO AND HARDEE COUNTIES, FLORIDA 71

vkiual sand grains are sub-angular to rounded. Phosphate nodules 

range from, fine sand to cobbles. The phosphate in the Hawthorn 

formation is predominantly brown; individual grains are glossy 

surfaced.

Irregular chert nodules of cobble to boulder size are locally common 

in the upper part of the Hawthorn formation. Some nodules are 

lenticular, others are in a variety of shapes. The nodules are distributed randomly, and the long axes have no apparent relation to the 

bedding in the limestone. These characteristics suggest an authigenic jorigin for the chert.

Internal and external molds of pelecypods and gastropods are 

abundant in the upper part of the Hawthorn formation.

Distribution. The Hawthorn formation underlies the undifferentiated phosphatic sand and clay throughout most of Hardee County 

(pi. 2, and fig. 8). A slight southward dip is indicated by elevations

Sand of late Miocene age

Hawthorn formation

40 Mites

FIGURE 8 Diagram showing the general stratigraphic relations of the formations in Hardee and De

Soto Counties.

of exposures and drill holes, but this is virtually impossible to measure 

because of the eroded relief on the present upper surface of the Hawthorn formation. Well records show that the Hawthorn formation 

varies in thickness. A well drilled at Quincy, in Gadsden County, 

revealed 210 feet of Hawthorn formation (Cooke, 1945, p. 145). Near 

Hilliard, in Nassau County, nearly 400 feet of Hawthorn formation 

was identified from well cuttings (Cooke, 1945, p. 145). Greater 

thicknesses may have been deposited at points farther from the Ocala 

uplift (Cooke, 1945, p. 5-7), particularly in southern Florida, but 

much of the present range in thickness in central and northern Florida 

reflects post-Hawthorn erosion. In southern Hardee and De Soto 

Counties, the formation has been reached in drill holes; however, the 

thickness in this region is unknown.

Details and fauna. Nearly all of the fossils listed in this section 

are described by Gardner (1926) in her detailed work on the middle 

Miocene molluscan fauna of Florida.

Because natural exposures of the Hawthorn formation are limited 

to the upper few feet, details on lithology, sedimentary structures; and
72 CONTRIBUTIONS TO THE GEOLOGY OF URANIUM

fauna are difficult to obtain. Many outcrops are either barren of 

fossils or they are so close to water level of streams that extensive 

investigation is impossible.

The thickest section of Hawthorn formation in this region was found 

along the north bank of the Peace River, at the bridge on U. S. Highway 17 (loc. 22-53, pi. 1), 0.5 mile north of Zolfo Springs (NEKSEK 

sec. 22, T. 34 S., R. 25 E., Hardee County). Here, 6 feet of gray 

indurated limestone is exposed above water level in the river. Chert 

cobbles and boulders are incorporated within the upper 2 feet of the 

limestone. The following fossils, identified by F. S. MacNeil; were 

collected :

Pelecypoda:

Chlamys sp.

Venericardia sp. 

Bryozoa

Although these invertebrates are not diagnostic of the middle 

Miocene, the lithology of the limestone is typical of the Hawthorn 

formation in this area; furthermore, less than 1 mile south of this 

locality along the Peace River (loc. 16-53, pi. 1) at the northwest 

corner of the bridge over the Peace River on State Highway 64, 1.3 

miles west of Zolfo Springs similar limestone containing a probable 

Hawthorn fauna is exposed at water level. The following external 

molds of pelecypods, identified by F. S. MacNeil, were collected here:

Venericardia sp. aff . V. hadra and V. himerta Dall. Fragment of external mold. 

Cardium (Tr achy car dium) sp. Sculpture resembles that of C. malacum Dall. 

Fragments of external mold.

Additional evidence for the middle Miocene age of the limestone in 

this region was furnished from fossiliferous limestone cores of the 

U. S. Atomic Energy Commission. In drill hole 10-8, in SW^SWK 

sec. 15, T. 34 S., R. 25 E., Hardee County (pi. 1), the following 

pelecypods were identified (by F. S. MacNeil) in a soft, phosphatic 

limestone at 36.4 feet below the surface:

Anadara sp.

Chione sp. aff. C. sellardsi Gardner

From drill hole 11-1, in NW^NWK sec. 1, T. 34 S., R. 25 E., 

Hardee County (pi. 1), a tan, sparsely phosphatic, clayey limestone 

yielded these invertebrates, which were identified by F. S. MacNeil, 

at depths ranging from 13.6 feet to 17.0 feet below the surface:

Gastropoda:

Cancellaria sp. cf. C. macneili Mansfield (description from Area zone of the 

Choctawhatchee formation of Cooke and Mossom, 1929)

Semicassis1? 

Pelecypoda:

Cflycymeris sp. aff. G, subovata (Say)
STRATIGRAPHY, DE SOTO AND HARDEE COUNTIES, FLORIDA 73

Anadara sp. cf. A. gunteri Gardner 

Plicatula sp. cf. P. densata Conrad 

Phacoides sp. cf. P. contractus (Say) 

Venericardia sp. 

Cardium sp. 

Dosinia sp. 

Venus sp.

This assemblage is probably late middle Miocene and would therefore be from the upper part of the Hawthorn formation.

In drill hole 11-5 in NE%SE^ sec. 31, T. 33 S., K. 26 E., Hardee 

County, and drill hole 11-6 in NEKSE^ sec. 31, T. 33 S., K. 27 E., 

Hardee County (pi. 1), the Hawthorn formation was penetrated at 

depths of 49 feet and 72 feet respectively. The following pelecypods 

were identified by F. S. MacNeil from the core in drill hole 11-53:

Glycymeris sp. j 

Phacoides sp. cf. P. contractus (Say)

The limestone in drill hole 11-6 contained these pelecypods:

Chlamys sp. aff. C. nicolsi Gardner. Fragments of external mold. 

Venericardia sp. Internal mold.

Chione sp. aff. C. chipolana Dall ' 

Venus sp. Internal mold.

In the southern part of the area, an undetermined thickness of 

strata of late Miocene age overlies the Hawthorn formation. The 

Hawthorn formation is not exposed in De Soto County. The 

upper Miocene sediments, some of which are limestones, thicken! 

southward, down dip, and diagnostic fossils are necessary for dif-; 

ferentiating the Hawthorn formation from the lower strata of the 

upper Miocene rocks.

Origin. The lithology of the Hawthorn formation indicates deposition in a shallow sea. North of the land-pebble phosphate 

district, in Pasco and Hernando Counties, the Hawthorn formation is predominantly sand, which is suggestive of deposition in a near-shore environment. Most writers (Eldridge, 

1893, p. 196-231; Matson and Clapp, 1909, p. 139, 167; Matson and 

Sanford, 1913, p. 145-206; Matson, 1915, p. 65; Sellards, 1915, p. 58) 

believed the subjacent Hawthorne formation to be the source rock 

for the phosphate in the economic land-pebble phosphate deposits.:

SAND OF LATE MIOCENE AGE

A gray to green, slightly phosphatic, marine sand underlies all of 

De Soto County and the southern part of Hardee County and contains an invertebrate fauna, including many large oysters and barnacles. The characteristic lithology and associated fauna are easily 

identified, even in auger cuttings. The sand is the youngest of the 

upper Miocene strata in this area (fig. 7). It is well exposed in a
74 CONTRIBUTIONS TO THE GEOLOGY OF URANIUM

borrow pit (NW&SE& sec. 24, T. 3,8 S., R. 24 E.) along Florida Eoute 

760, 1.6 miles east of the junction of U. S. Koute 17 and Florida 

Route 760 at Nocatee (fig. 9). Fossiliferous sand is exposed at or 

below water level in the pit. Piles of dredged material around the 

sides of the pit yielded marine fossils, which establish the latest 

Miocene age of the sand. A drill hole near the east end of the pit 

revealed a thickness of 16 feet of the Miocene sand at this locality. 

In the borrow pit this late Miocene sand is overlain by 6 feet of a 

surficial sand and calcareous clayey sand containing fresh-water and

Tailings ~, 2

Auger hole 50-53

6'- 

4'-

Z'-

 fw!^^:'-;;'^.;:MS^^^^^. I Pleistocene ^^^^^ deposits osis

id of late 

i Miocene age -4'-

 !H«S-:VH^iS:?$i?:-i:5) I Pleistocene 

^j^^iMSji^M I deP°sits

WA TEK LEVEL

' J

\ Sand of late 

; Miocene age

\ Sand of late 

i Miocene age

EXPLANATION 

Calcareous quartz sand' 

Calcareous clayey sand

300 Feet

Contour interval 6 feet 

Datum is water level in pit

Fossiliferous (non-marine) 

phosphatic quartz sand

Stratified phosphatic sand

FIGURE 9. Sketch map and cross sections of borrow pit, 1.6 miles east ol Nocatee, De Soto County.
STRATIGRAPHY, DE SOTO AND HARDEE COUNTIES, FLORIDA 75

land gastropods of probable Pleistocene age. The upper contact of 

the late Miocene sand with this surficial material is sharp and, at 

several places in the pit, is marked by a 3- to 6-inch bed of phosphate 

pebbles and cobbles comprising the basal unit of the Pleistocene section (fig. 9, sec. A A', B B', C C'}. The lower contact of the 

sand with the Hawthorn formation is not exposed at this locality. 

Indurated limestone (Hawthorn? formation) was encountered in the 

auger hole (fig. 9) at a depth of 27 feet below the surface. No limestone sample was recovered. A bed of nonfossiliferous phosphate 

gravel, 2 feet thick, immediately overlies the limestone at this locality.

No vertebrate fossils were found in the sand of late Miocene age in 

the area investigated; however, MacNeil (written communication, 

July 1954) reported that he found remains of the mastodon Serridentinus floridanus (a "good lower Pliocene" species) in the lower part 

of, or immediately below, similar sand in Charlotte County. This 

apparent coincidence of vertebrate lower Pliocene and invertebrate 

uppermost Miocene fossils points out the current uncertainty as to 

the exact stratigraphic position of the Miocene-Pliocene boundary.

On the basis of MacNeil's invertebrate fossil identifications this 

sand of late Miocene age is either younger than, or equivalent to, the 

uppermost part of the Tamiami formation, because this formation is 

now used to include marine rocks of late Miocene age in southern 

Florida (Parker, 1951, p. 823).

Lithology. The sand of late Miocene age is a fine-grained, darkgreen to light-gray quartz sand, slightly to extremely clayey in places. 

Phosphate, in sand measuring to gravel size, is a conspicuous, though 

minor, constituent. The phosphate nodules are hard, dark colored, 

and smooth surfaced. None of the crumbly white-weathered phosphate, common in the undifferentiated phosphatic sand and clay, is 

present.

In general, the lower part of the unit contains appreciably more 

clayey material than is present in the upper part. Beds of green calcareous clay and scattered lenses of soft sandy limestone are encountered beneath the typical gray to green sand facies during drilling.

The lithology changes somewhat in southern Hardee County. The 

unit is thinner, more clayey, and contains moderate amounts of 

phosphate. Fossils are absent in this area.

Fauna. W. C. Mansfield (1932, p. 43-56) listed and described the 

marine invertebrates collected from the limestone that is exposed hi 

ditches along the Tamiami Trail in Collier and Monroe Counties. At 

that time, he regarded the fauna as Pliocene in age, and he considered 

the limestone to be a facies of the Caloosahatchee marl. Later 

(W. C. Mansfield, 1939, p. 8), he gave this limestone the name 

"Tamiami" and assigned it to the lower part of the Pliocene, thus
76 CONTRIBUTIONS TO THE GEOLOGY OF URANIUM

considering it to be older than the Caloosahatchee marl. Mansfield's 

collection lacked the diagnostic fossils that indicate a Miocene age 

for the Tamiami formation.

During 1947 and 1948, while working with the U. S. Geological 

Survey Florida Phosphate Project, F. S. MacNeil made large new 

collections from the upper Miocene and Pliocene formations in 

southern Florida. As a result, he was able to revise (unpublished) 

the age of the faunas involved. The sequence established by Mansfield (1939) for the Buckingham, Tamiami, and Caloosahatchee 

faunas was supported, but his Buckingham and Tamiami limestones 

were reassigned to the late Miocene.

Many of the species collected from the sand of late Miocene age in 

De So to and Hardee Counties are also found in the Tamiami formation. 

The following fauna, identified by F. S. MacNeil, was collected from 

dredged material piled along the sides of the large borrow pit located 

1.6 miles east of Nocatee (fig. 9):

Gastropoda:

Rapana? or Ecphora n. sp. 

Pelecypoda:

Chlamys (Plagioctenium) n. sp.? aff. C. eboreus watsonensis Mansfield and 

C. caloosensis Mansfield, both upper Miocene

Ostrea tamiamiensis monroensis Mansfield (=0meridionalis Heilprin?) 

disparilis Conrad subsp.?

Pododesmus n. sp.?

Laevicardium sp. 

Cirripedia:

Balanus sp.? A large barnacle, seemingly characteristic of this zone.

Distribution. Auger holes revealed that the sand of late Miocene 

age underlies all of De Soto County and extends northward into 

Hardee County, where it interfingers with the undifferentiated phosphatic sand and clay (pi. 2, fig. 8). Apparently, it occurs over an 

area much larger than Hardee and De Soto Counties. Gardner 

(1945, p. 37-41) described fossils from an oyster "reef" of late Miocene 

age, which was discovered during dredging operations off the southeastern end of Snell Island in Tampa Bay within the city limits of 

St. Petersburg. The matrix between the closely packed oysters 

consists of clear quartz sand and light-gray limy clay. To date, 

this is the most northwesterly occurrence of the sand of late Miocene 

age.

In De Soto County the sand attains thicknesses of 40 feet or more, 

but it gradually becomes thinner northward. In southern Hardee 

County the unit is usually less than 20 feet thick.

Details. Dall (1892, p. 131-133) reported a light-colored phosphatized calcareous sand at a locality 6 miles north of Arcadia, on Mare 

Branch, which is a tributary of the Peace River. He named this
STRATIGRAPHY, DE SOTO AND HARDEE COUNTIES, FLORIDA 77

rock the "Arcadia marl" and considered it early Pliocene in age. 

Dall (1892, p. 131-133) also described an outcrop along the Peace 

River at Shell Point, about 3 miles north of Arcadia. He called this 

rock an "oyster marl" and reported that it contained oysters, barnacles, 

and pectens that are similar to those occurring in the Caloosahatchee 

marl. According to Dall, a similar "oyster marl" was found along 

Joshua Creek near Nocatee and another exposure was found in the 

banks of a small stream just north of Zolfo Springs. The shell bed 

at Zolfo Springs is overlain by 20 to 25 feet of partly indurated 

yellow sand. Matson and Clapp (1909, p. 123) regarded Ball's 

"Arcadia marl" as a phase of the Caloosahatchee marl.

The "Arcadia marl" and "oyster marl" of Dall are both included in 

the unnamed sand of late Miocene age, described herein. At the southwest corner of the bridge over the Peace River, 1.2 miles west of 

BrownviUe, De Soto County (NE^SE^ sec. 31, T. 36 S., R. 25 E., 

loc. 18-53, pi. 1), a soft, buff-colored, phosphatic, sandy limestone 

exposed at water level is probably the "Arcadia marl" described by 

Dall. Core from drill hole 10-15, in SE^NE% sec. 32, T. 36 S., R. 

25 E., De Soto County (pi. 1), about 1 mile east of the above exposure, 

contained Balanus sp., bryozoa, and echinoid spines in a sandy shell 

bed at a depth of 50 feet. This assemblage compares favorably 

with the upper Miocene fauna collected from the borrow pit east of 

Nocatee. The 50-foot depth, at which this shell bed was penetrated, 

is at almost the same elevation as both the limestone along the Peace 

River near Brownville and the shell bed at the .pit near Nocatee. 

Results of auger drilling in the immediate area further substantiated 

the fact that the exposure at the Brownville bridge is a lens of clayey 

limestone within the sand, which is present in the Arcadia-NocateeBrownville area; the Caloosahatchee marl occurs south of Nocatee. 

Dall's "Arcadia marl" is the lower and more clayey part of the sand 

in which his "oyster marl" is the typical material. The occurrence of 

"Arcadia marl" near Zolfo Springs is considered Hawthorn formation. 

The northern limit of upper Miocene and Pliocene marine rocks in 

this region is about 5 miles south of Zolfo Springs.

The contact between the Hawthorn formation and sand of late 

Miocene age is exposed along the west bank of the Peace River (fig. 

10), at the site of a former bridge (NW^SE^ sec. 17, T. 36 S., R. 25 E., 

Hardee County, loc. 20-53, pi. 1) located \% miles west of Gardner. 

A section extending 16 feet above water level is exposed. A thickbedded, phosphatic, slightly clayey calcareous sand disconformably 

overlies a thin-bedded, sparsely phosphatic, silty, soft limestone. 

A phosphate conglomerate occurs at the base of the upper calcareous 

sand. On the basis of similar lithology, the lower thin-bedded unit 

is tentatively called Hawthorn formation. Results of drilling in the

378283 56 3
78 CONTRIBUTIONS TO THE GEOLOGY OF URANIUM 

EXPLANATION

*&&&"^'&&&&&*&&*&

Fossiliferous (marine) phosphatic

Pleistocene 

deposits

DISCONFORMITY

Sand of late 

Miocene(?)age

DISCONFORMITY

Hawthornf?) 

formation

Phosphatic limestone

FIGURE 10. Sketch of section exposed along the west bank of the Peace Elver, near Gardner, Hardee

County.

vicinity favor a late Miocene age for at least the upper thick-bedded, 

calcareous material. From drill hole 10-14 (N^SE% sec. 21, T. 36 

S., R. 25 E., De Soto County), located slightly more than 1 mile 

southeast of the exposure just described, limestone was encountered 

from 27 to 37 feet below the surface. Drilling was discontinued at 

37 feet. Limestone core from 33 to 35.5 feet contained the following 

pelecypods, which were identified by F. S. MacNeil:

Ostrea sp. aff. 0. puekhana d'Orbigny

Chlamys sp.

Cardita sp.

Cardium sp.

Venus?

Spisulal

The oyster is unlike any found in the Hawthorn formation, and this 

assemblage is tentatively identified as upper Miocene.

The limestone in drill hole 10-14 could be equivalent to the thinbedded limestone at the exposure near Gardner (fig. 10). Conversely, 

the phosphatic sand at the Gardner bridge could be a more sandy, 

and more phosphatic phase of the limestone in the drill hole.

Origin. The sand of late Miocene age was deposited in a shallow 

marine environment. In southern Florida, the Tamiami formation 

and the Buckingham marl of Mansfield (1939) are deeper water sediments of the same sea. In southern Hardee County, the character 

of the sand changes, and the following features suggest an estuarine 

environment in this immediate area:
STRATIGRAPHY, DE SOTO AND HARDEE COUNTIES, FLORIDA 79

1. Preponderance of fine-grained sand and clayey sand within the 

formation.

2. Absence of fossils. Changes in pH of the estuarme waters 

caused by fluctuations in the discharge volumes of rivers might create 

unfavorable conditions for organisms.

3. Lack of well-defined beach deposits or bars.

MIOCENE TO PLIOCENE SERIES 

UNDIFFERENTIATED PHOSPHATTC SAND AND CLAY

The phosphorite, which underlies the northern two-thirds of Hardee 

County (pi. 1), is composed of either the Bone Valley formation or 

weathered residuum of Hawthorn formation, or both. These two 

units appear almost identical and are composed of phosphate nodules, 

sand, and clay. In Polk and eastern Hillsborough Counties, the phosphatic beds are well exposed on mine faces. Separate mapping of the 

Bone Valley formation and the residuum of Hawthorn formation may 

be possible where outcrops are relatively abundant and where observations of sedimentary structures and textures of the rocks hi place 

reveal discrete strata. Where subsurface information depends 

primarily on interpretation of auger cuttings, no practical basis exists 

for discriminating between two stratigraphic units of such similar 

lithology. For this reason, the phosphorite in Hardee County is 

mapped as undifferentiated.

Two of the earliest workers in the land-pebble phosphate district of 

central Florida were Ball (1892, p. 141-142), and Eldridge (1893, 

p. 196-231).

Matson and Clapp (1909, p. 138-141) named these phosphate 

deposits "Bone Valley gravel" from a locality west of Bartow, Polk 

County. As defined by them, the Bone Valley gravel consists of 

poorly sorted phosphate pebbles, clay, and sand of Pliocene age. 

Matson and Clapp (1909, p. 140-141) divided the Bone Valley gravel 

into lower beds rich in phosphate nodules and an upper non-economic 

unit containing very little phosphate. According to these writers, 

an unconformity separated the Bone Valley gravel from the overlying 

surficial sand of Pleistocene age. Relations between the Bone Valley 

gravel and the older formations were not known at that time.

Sellards (1915, p. 58) agreed with most of the earlier writers on the 

Pliocene age of the Bone Valley gravel.

Later, from vertebrate fossil evidence, Matson (1915, p. 21) suggested a late Miocene age for the Bone Valley gravel. Horse teeth 

(species of Merychippus or Neohipparion), a mastodon upper jaw 

(Tetrabelodon), and a second upper molar that differed only slightly 

from the corresponding tooth of Teleoceras fossiger, all of which were 

found in the Bone Valley gravel, are indicative of an upper Miocene
80 CONTRIBUTIONS TO THE GEOLOGY OF URANIUM

fauna. Matson (1915, p. 22) located the southern boundary of the 

Bone Valley gravel in the vicinity of Zolfo Springs, Hardee County.

Cooke and Mossom (1929, p. 134) stated that the Bone Valley 

gravel lies unconformably on the Hawthorn formation in the phosphate mines in Polk County. They also reported an unconformity 

at the top of the Bone Valley gravel.

Cooke, (1945, p. 203) suggested that the name "Bone Valley formation" was more appropriate than "Bone Valley gravel," because gravel 

makes up only a small fraction of the rock. Cooke (1945, p. 206) 

proposed that some of the Bone Valley formation "* * * may be the 

residual products of the decomposition in place of the Hawthorn 

formation."

Altschuler and Boudreau (unpublished material, 1949) studied in 

detail the mineralogy and petrogrophy of the Bone Valley formation. 

Cathcart (unpublished material, 1949,1950) discussed the importance 

of the leached upper portion of the Bone Valley formation as a source 

of uranium.

Lithology. The undifferentiated phosphatic sand and clay is an 

unconsolidated rock of a prevailing brownish to buff color. Individual 

lithologic units may be blue green, brown, white, or gray.

The Bone Valley formation may display distinct bedding locally. 

Seams of blue to green clay are disseminated throughout the formation. Residuum of Hawthorn formation is similar in color and 

lithology to the Bone Valley formation^ but bedding is rarely preserved. Phosphate in clay to granule size is usually the most abundant component of both the Hawthorn residuum and Bone Valley

formation. Fine-grained quartz sand, silt-sized quartz, and clay 

minerals comprise the nonphosphatic fraction. The phosphate

grains are polished and are brown, black, gray, and white.

The upper few feet of the Bone Valley formation is generally 

severely leached and weathered. Where the Bone Valley formation 

is thin, or absent, this intense weathering is superimposed on the upper 

part of the Hawthorn residuum. In this leached zone (sometimes 

called the aluminum phosphate zone), the phosphate, which originally 

was present as nodules of carbonate fluorapatite, is altered to crandallite (pseudowavellite), which is the hydrous phosphate of aluminum

and calcium, and to wavellite, which is the hydrous phosphate of 

aluminum (Altschuler and Boudreau, unpublished material, 1949, 

p. 36-38). The former presence of phosphate nodules is marked by 

molds in vesicular clayey sand loosely cemented by wavellite and 

crandallite.
STRATIGRAPHY, DE SOTO AND HARDEE COUNTIES, FLORIDA 81

Fauna. No fossils were found in the undifferentiated phosphatic 

sand and clay during this investigation.

Occurrences of marine invertebrates in the Bone Valley formation 

are rare; however, MacNeil (written communication, July 1954) reported that marine razor clams were found in exposures in southern 

Polk County.

Vertebrate fossils are abundant. Remains of manatees, whales, 

crocodiles, mastodons, and horses have been recovered from the Bone 

Valley formation during phosphate mining operations. Sharks' 

teeth, which are plentiful, possibly were derived from the subjacent 

Hawthorn formation.

Generally, the Bone Valley formation is considered to be Pliocene 

in age, but until the Miocene-Pliocene boundary is re-established the 

age of this formation cannot be categorically stated.

The vertebrate fauna is considered Pliocene (Simpson, 1929, p. 257; 

1930, p. 180), but this dating is flexible. Most of the vertebrate remains could be late Miocene as well as Pliocene in age. Simpson 

(1929, p. 257) admits that "* * * The possibility of derivation of 

fossils from older beds and of accidental mixture with younger fossils 

on collecting or in the compilation of 'faunal lists' based on general 

localities is obviously great." Simpson (1930, p. 179-180) again 

discussed possibilities of false association of the Tertiary land mammals 

in the Bone Valley formation. Most of the fossils of land mammals 

were found by people with no geologic training during hydraulic mining of the phosphate beds.

Distribution. Auger holes were necessary to determine the extent 

of the undifferentiated phosphatic sand and clay. In Hardee County, 

north of about 27°25/ latitude (pi. 1), the Hawthorn formation is overlain by noncalcareous phosphatic sand and clay. The sand of late 

Miocene age interfingers with the undifferentiated phosphatic sand 

and clay in southern Hardee County Cpl. 2). The thickness of the 

phosphorite in this area ranges from less than 10 feet to more than 30 

feet (pi. 2).

Details. Exposures of the upper part of the undifferentiated phosphatic sand and clayey sand were found at only three localities hi 

Hardee County, as follows:

The Bone Valley (?) formation is exposed in the bottom of a ditch 

along the east side of a dirt road in the NWKNWK sec. 18, T. 33 S., 

R. 26 E., Hardee County (loc. 11-53, pi. 1). Only the upper 2 feet of 

stratified clayey sand and sand, which contains abundant phosphate 

nodules, can be seen.
82 CONTRIBUTIONS TO THE GEOLOGY OF URANIUM

At the bridge over the Peace River (loc. 27-53, pi. 1), 1 mile southeast of Wauchula, Hardee County (NW# sec. 11, T. 34 S., R. 25 E.), 

along the east bank of the river, the following section is exposed:

Formation

Depth from 

surface 

(In feet)

Description

Pleistocene deposits. _ _ 0-2%

Disconformity.

Undifferentiated phosphatic sand and 

clay.

6-11^2

Sand, fine-grained, quartz, tan.

Clayey sand, dark-brown, iron-stained; contains scattered soft, white (weathered) 

phosphate nodules.

Slightly clayey sand; contains scattered 

fresh phosphate nodules. Lower 1 foot 

is coarse-grained sand; bottom 4 inches 

is a bed of gravel- to pebble-sized phosphate, fish teeth, worn bone fragments. 

No diagnostic fossils.

Bottom of conglomerate stratum in Pleistocene deposits.

Clayey sand; contains very abundant sandsized phosphate. Interval is slightly 

iron-stained in upper 7 inches, buff to 

olive color below. Entire interval is 

noncalcareous; bedding indistinct.

At this exposure, it was not possible to determine whether the 

phosphorite is Bone Valley formation, Hawthorn residuum, or a 

combination of both. The obscure stratification could be relict 

from the parent Hawthorn formation, or it could be a primary structure of Bone Valley sedimentation. The lower contact of the phosphatic sand and clay with calcareous Hawthorn formation is below 

water level in the river.

In a borrow pit (loc. 10-53, pi. 1), 0.3 mile west of the Peace River 

bridge (NEtf sec. 28, T. 34 S., R. 25 E., Hardee County) on Florida 

State Highway 64, 1.3 miles west of Zolfo Springs, the upper part of 

the Bone Valley formation is exposed beneath sand of Pleistocene 

age. The stratification is distinct below a zone of iron accumulation. 

Individual layers are 2 to 6 inches thick and are differentiated by 

variations in the amounts of clay and phosphate. Phosphate is 

present as partly leached nodules and possibly also as clay-sized 

wavellite and crandallite. Partly indurated sand cobbles, which 

comprise single beds, still retain small voids previously occupied by 

phosphate grains. Several tiny phosphatized shell fragments, which 

could not be identified, were in the indurated sandy cobbles. Phosphate was very abundant at one point. Individual strata, 2 to 3 

inches thick, composed of leached phosphate nodules and quartz
STRATIGRAPHY, DE SOTO AND HARDEE COUNTIES, FLORIDA 83

sand are conspicuous. The bedded phosphatie material in this pit 

is interpreted as a reworked deposit of the aluminum phosphate 

zone of the undifferentiated phosphatie-sand and clay. The preservation of bedding, the stratification of the sandy cobbles, and the 

variation of phosphate content along the face of the pit indicate a 

redeposition of previously weathered material, rather than an accumulation in place of the residual products of a parent rock such as 

the Hawthorn formation.

Origin. While forming hypotheses of the origin of the Bone Valley 

formation, many of the earlier workers presupposed a phosphatie 

residuum of Hawthorn formation that was modified by a variety of 

agents during Pliocene time.

Eldridge (1893, p. 196-231) considered the phosphate deposits as 

a residuum that was later reworked by marine action.

Matson and Clapp (1909, p. 138-139) interpreted the poor sorting 

and the absence of distinct local stratification as evidence of a fluviatile origin. They admitted that some deposition may have occurred 

in the margins of estuaries. Fragments of bone and sharks' teeth were 

assumed to have been derived from older formations.

Matson and Sanford (1913, p. 145-206) described this formation as 

a deposit in a shallow sea. Submergence during Pliocene time resulted 

in the reasserting and redeposition of residual weathered material by 

wave action.

Sellards (1915, p. 58) postulated an advancing sea that redeposited 

material derived from the underlying phosphatie marl.

Cooke and Mossom (1929, p. 164) believed that the phosphate deposits were accumulations within the lower reaches of a river and 

adjacent to its low-lying banks. Cooke (1945, p. 206) reasoned that 

these pbosphatic sediments were deposited in the delta of a southwardflowing river. Estuarine deposition occurred seaward from the delta. 

Cooke also stated that some of the Bone Valley formation may be the 

residual product of weathered Hawthorn formation.

MacNeil (written communication, July 1954) considers the Bone 

Valley formation to be of marine origin, equivalent stratigraphically 

to the unnamed sand of late Miocene age of this report.

The undifferentiated phosphatie sand and clay and the sand of late 

Miocene age interfinger in southern Hardee County (pi. 2). If the 

Bone Valley formation is a marine sediment, it is probable that the late 

Miocene sea inundated all of Hardee County, thus completely reworking the phosphatie Hawthorn residuum and redepositing it as Bone 

Valley formation.

If the Bone Valley formation is of fluvial origin, the incomplete 

reworking of weathered Hawthorn formation would preserve patches 

of residuum, especially on higher areas. Under this hypothesis, the
84 CONTRIBUTIONS TO THE GEOLOGY OF URANIUM

late Miocene shoreline may have been approximately parallel to the 

present northern limit of the sand of late Miocene age. The age of this 

phosphorite, if undifferentiated, would range from middle Miocene 

through Pliocene, because Pliocene marine deposits have never been 

reported as overlying the phosphorite.

Therefore, as long as any possibility exists that the Bone Valley 

formation is a fluvial deposit, it is necessary to refer to the phosphorite 

in this area as undifferentiated phosphatic sand and clay.

PLIOCENE SERIES

CALOOSAHA.TCHEE MARL,

During his explorations in southern Florida, Angelo Heilprin (1887) 

first identified fossiliferous beds exposed along the Caloosahatchee 

River as Pliocene in age.

Ball (1892, p. 140-149) named these beds "Caloosahatchie" and 

extended the marine Pliocene as far northward as Zolfo Springs in 

Hardee County. At that time, his "Arcadia marl" and "oyster marl" 

were considered to be equivalent to the "Caloosahatchie beds."

Cooke (1945, p. 216-217) believed the Caloosahatchee marl to be 

present in the southern part of Be Soto County. He thought that the 

Bone Valley formation and Caloosahatchee marl merged somewhere to 

the north.

The fauna of the Caloosahatchee marl is well known, and the 

Pliocene age of this formation has never been seriously questioned. 

Outcrops along the Caloosahatchee River near La Belle, Hendry 

County, are collecting grounds for the large and well-preserved fauna. 

The precise boundaries and the stratigraphic relations of the Caloosahatchee marl with formations to the north were largely speculative 

because of the limited number of outcrops along the streams. Many 

writers, following Ball's pioneer work, extended the Caloosahatchee 

marl much farther north into Be Soto and Hardee Counties; actually, 

it does not extend this far to the north.

Liihology. The Caloosahatchee marl in this area is a gray finegrained sand, slightly clayey to clayey in places. It is predominantly 

a sand rather than a marl. The marine invertebrate fauna is large, 

and it contains many fossils of present-day species. In some places 

the Caloosahatchee marl is composed primarily of shells for example, 

along Prairie Creek in Be Soto County, where it is mined for road fill. 

Exposures along Prairie Creek are surficially cemented by iron oxide. 

Unweathered material is gray to blue-gray. Belicate shells are 

unusually well preserved, which is an indication of deposition with 

little wave action.

Distribution. Auger holes disclosed that the Caloosahatchee marl 

is restricted to the southeastern part of Be Soto County (pi. 1). In
STRATIGRAPHY, DE SOTO AND HARDEE COUNTIES, FLORIDA 85

the vicinity of Pine Level, 9 miles northwest of Arcadia (sec. 10, 

T. 37 S., R. 23 E., De Soto County), and along Horse Creek (sec. 1, 

T. 38 S., R. 23 E., De Soto County) discontinuous, thin patches of nonfossiliferous calcareous clayey sand are present beneath the Pleistocene 

sediments. This material may be Caloosahatchee marl, but it probably is sand of late Miocene age, because fossiliferous sand of late 

Miocene age is close to the surface here (pi. 2).

Shell fragments in the interval from 5 to 14 feet from an auger hole 

in the SEKSWK sec. 22, T. 38 S., R, 25 E., De Soto County (loc. 42-53, 

pi. 1) mark the northernmost known occurrence of the Caloosahatchee 

marl in the area. Locally, the abundance of land and fresh-water 

snails in the Caloosahatchee fauna suggests that the known distribution of this formation is very close to the Pliocene shoreline. Drill 

records show that the Caloosahatchee marl does not exceed a thickness 

of 20 feet in De Soto County (pi. 2).

Details and fauna. The fauna of the Caloosahatchee marl is described by Heilprin (1887) and by Dall (1903). More than 600 species 

were identified by Dall. Mollusks are predominant among the 

excellently preserved shells.

At a borrow pit in the SWK sec. 26, T. 39 S., R. 25 E. (loc. 1-53, 

pi. 1), about 1,500 feet west of Florida State Highway 31 along 

Prairie Creek, the upper 2 feet of a shell bed is exposed above water 

level in the pit. Such Pliocene species as Area wagneriana Dall, 

Strombus leidyi Heilprin, and Turritella perattenuata Heilprin are 

common among a large molluscan fauna. This Caloosahatchee shell 

bed extends westward at least as far as the NW% sec. 33, T. 39 S., 

R. 25 E., De Soto County (loc. 8-53, pi. 1). At this location, the 

following species, identified by F. S. MacNeil, were collected from 

the top of the shell bed exposed at water level along Prairie Creek:

Gastropoda:

Turritella apicalis Heilprin 

Pelecypoda:

Echinochama arcinella Linnaeus

Chione cancellata Linnaeus

Two limestone pebbles, apparently derived from Mansfield's 

Buckingham marl, of late Miocene age, were incorporated in the 

Caloosahatchee marl at this locality. These pebbles contained the 

following shells, which, according to MacNeil, who identified them 

(written communication, January 1954), are common in Mansfield's 

Buckingham marl:

Pelecypoda:

Chlamys (Plagioctenium) eboreus buckinghamensis Mansfield

Chione athleta Conrad 

Cirripedia:

Balanus sp., which is a medium-sized barnacle that apparently occurs 

abundantly at Buckingham, Lee County.
86 CONTRIBUTIONS TO THE GEOLOGY OF URANIUM

The upper 6 inches of Caloosahatchee marl is exposed above water 

level near the bottom of a drainage ditch in southern De Soto County 

(SWKSWK sec. 28, T. 38 S., R. 25 E., map loc. 25-33, pi. 1). A 

4-inch layer of iron-stained phosphate gravel overlies the Pliocene 

shell bed. This gravel is the basal unit of the surficial sand and 

clayey sand of Pleistocene age, which is 3K feet thick here. The 

species listed below, identified by F. S. MacNeil, were collected 

from the spoil banks along the ditch. The assemblage is clearly a 

Caloosahatchee fauna.

Gastropoda:

Conus sp. (juvenile)

Oliva frag. cf. 0. sayana Ravenel

Turritella subannulata Heilprin

apicalis Heilprin

perattenuata Heilprin 

Pelecypoda:

Anadara lienosa (Say) 

Chlamys harrisi Dall 

Anomia simplex d'Orbigny 

Ostrea sculpturata Conrad

virginica Linnaeus 

Cardita arata Conrad 

Phacoides caloosaensis (Dall) (mold) 

Echinochama arcinella (Linnaeus) 

Chione cancellata Linnaeus

Origin. The Caloosahatchee marl was deposited in a shallow sea. 

The preservation of fragile shells indicates that wave action was 

negligible. It is possible that offshore bars or groups of islands 

acted as barriers against storms. Phosphate nodules were not 

deposited during this submergence.

PLEISTOCENE SERIES

Differentiation of the Pleistocene sediments into formations is difficult in Florida because of the intensely weathered condition and the 

lithologic similarity of the surficial material especially in the interior 

of the peninsula. Much of the study of rocks of Pleistocene age has 

been limited to the fossiliferous limestones and marls that are exposed 

in the southern part of the State. The alternating fresh-water and 

marine limestones and clayey sands of Pleistocene age, comprising 

the Fort Thompson formation, have been described by Cooke and 

Mossom (1929), Parker and Cooke (1944), and Cooke (1945).

A number of marine terraces are recognized by geomorphological 

evidence. These terraces are remnants of higher shorelines that were 

developed during pauses in the oscillations of the Pleistocene sea. 

The surficial sediments associated with each terrace have been given 

formation names by some writers.
STRATIGRAPHY, DE SOTO AND HARDEE COUNTIES, FLORIDA 87

Matson and Sanford (1913, p. 32-35) recognized three terrace deposits of Pleistocene age. The highest of these, called the Newberry, 

included surficial sand and clay at elevations ranging from 70 to 100 

feet above sea level. The surficial sediments at elevations ranging from 

40 to 60 feet above sea level represented a later Tsala Apopka terrace. 

The lowest terrace, which they called the Pensacola, covered a broad 

plain that was less than 40 feet above sea level; it was composed of 

limestone in the southern part of the State.

Richards (1938, p. 1284-1285) found no evidence of marine deposits 

of Pleistocene age above 25 feet altitude along either coast of Florida. 

Above 25 feet, sediments of Pleistocene age contained no fossils; he 

believed that this land stood relatively high during most of the 

Pleistpcen.e.

Cooke (1945, p. 247-248) identified seven, and possibly eight, shorelines that represent stands of sea level during Pleistocene time.

Altitude 

Terrace (feet)

Brandywine___J__ _____________________________ 270

Coharie_________________________________-_____ 215

Sunderland..______________________________________ 170

Wicomico___________________________________________ __________ 100

Penholoway_______________________________ 70

Talbot_____-______________________--____ - 42

Pamlico- _____________^_ _____________________ ___ 25

With these seven shorelines, he assigned corresponding formations 

comprising the surficial sand within each topographic interval. The 

possible eighth shoreline of Cooke, the Silver Bluff, is 5 feet above 

present sea level. Cooke (1945, p. 289) postulated that most of De 

Soto County is covered by the Penholoway formation.

MacNeil (1950, p. 99) reported that the terraces below 150 feet 

are entirely of marine origin. He recognized the following Pleistocene 

shorelines, which he believed to represent peaks of marine transgression.

Terrace Altitude Age 

(feet)

Okefestekee____________ 150 Yarmouth interglacial stage

Wicomico_____________ 100 Sangamon interglacial stage

Pamlico___________ 25-35 Middle Wisconsin glacial recession

Silver Bluff _ _________ 8-10 Post-Wisconsin

No evidence of marine deposition during Pleistocene time was found 

in the area investigated in this report.

DEPOSITS OF PLiEISTOCENE AGE

Lithology. The Pleistocene deposits in the area are made up of 

lenticular strata of varying percentages of quartz sand, silt, and claysized material. These beds are generally brown to tan. Crossbedding 

is conspicuous, especially in the lower part of the formation. A con-
88 CONTRIBUTIONS TO THE GEOLOGY OF URANIUM

glomerate, or gravel, composed primarily of phosphate granules and 

pebbles is nearly always present within the lower 1 foot. Along 

Payne's Creek the deposits are cross-stratified, and a phosphatic 

gravel rests directly on the Hawthorn formation.

The lenticularity of the lithologic units is exhibited at the borrow 

pit near Nocatee (fig. 9), where a waxy blue clay grades laterally to a 

coarse sand within a distance of less than 100 feet. Similarly, the 

section along Horse Creek reveals a layer of brownish clay pinching out 

within a crossbedded sand stratum 2 feet thick.

At every outcrop the depth and intensity of the weathering profile 

developed on the Pleistocene deposits are similar. An iron-cemented 

zone is always present from 3 to 6 feet below the surface. This zone 

is usually less than 2 feet thick, and locally it may be an indurated 

crust or layer of ferruginous cobbles and boulders. Several feet below 

this zone of iron accumulation the color gradually changes to tan and 

the rock is relatively fresh.

Scattered thin deposits of sandy fresh-water limestone are included 

within the unit (pi. 1). These limestones contain fresh-water fossils. 

Root structures, which have been replaced by calcium carbonate, are 

common. The limestone is friable, and it normally grades laterally 

into a blue-gray marl or calcareous clayey sand.

Fine-grained quartz sand is the most abundant constituent. Lenses 

of blue-gray clayey sand and clay, 1 to 3 feet thick, are scattered 

throughout the sand. Phosphate nodules may be abundant locally.

The grain size of the quartz sand is generally greatest near the 

bottom of the formation. Phosphate nodules, if present, are more 

abundant near the lower contact, regardless of the lithology of the 

underlying rock.

Fauna. At an exposure along Prairie Creek (NWK sec. 33, T. 39 S., 

R. 25 E., De Soto County; loc. 8-53, pi. 1), the Caloosahatchee marl 

is overlain by 6 feet of Pleistocene deposits. A 6-inch stratum of 

coarse sand, bone fragments, and minor phosphate gravel is the basal 

unit. Within this basal gravel was found a lower incisor of a rhinoceros, probably Aphelops, which was identified by Jean Hough. The 

age of Aphelops is early to middle Pliocene.

At a borrow pit near Nocatee, part of an upper molar of Neohipparion, identified by Jean Hough, was found in the stratified surficial 

sand. Neohipparion is a horse of early to middle Pliocene age. At 

the borrow pit east of Nocatee (fig. 9), and at a borrow pit northwest 

of Nocatee (SE%SW% sec. 11, T. 38 S., R. 23 E., De Soto County), 

molars of a horse, probably Neohipparion, identified by Jean Hough, 

were collected from the surficial sediments.

Although the vertebrate teeth suggest that the deposits are Pliocene, other evidence points more conclusively to a Pleistocene age.
STRATIGRAPHY, DE SOTO AND HARDEE COUNTIES, FLORIDA 89

invertebrate fauna, which consists predominantly of a freshwater and land assemblage of gastropods, is different from the freshwater mollusks in the Caloosahatchee marl. Many of the species are 

also common hi the brackish and fresh-water sediments of Pleistocene 

age throughout southern Florida. In addition, the unit unconformably 

overlies the Caloosahatchee marl, which is definitely Pliocene, possibly late Pliocene, in age. The vertebrate teeth, which are resistant 

to erosion and weathering, were probably derived from the Bone 

Valley formation. Erosion of these earlier sediments supplied the 

components of the Pleistocene deposits.

Most of the invertebrate species listed in this section also appear 

in Pleistocene faunal lists by Sellards (1916, p. 144), and by W. C. 

Mansfield (1939, p. 33-45). The fauna listed by Sellards was associated with human remains at an exposure near Vero Beach. The 

fossils described by W. C. Mansfield were collected from numerous 

localities throughout southern Florida.

At the borrow pit east of Nocatee (fig. 9) the following invertebrates, identified by F. S. MacNeil, were collected from the phosphatic sand directly overlying sand of late Miocene age:

Gastropoda:

Fresh water:

Viviparus georgianus Lea 

Campeloma sp. 

Goniobasis sp. strong axials 

Helisoma (Seminolind) duryi (Wetherby) var.? 

Land:

Euglandina sp. cf. E. rosea (Ferussac) 

Polygyra septemvolva volvoxis Pfeiffer 

Pelecypoda: 

Rangia sp.

In a shallow ditch along Florida Route 661, 3.5 miles north of 

Limestone, Hardee County (SW%SW% sec. 24, T. 35 S., R. 24 E.), 

the gastropods listed below, identified by F. S. MacNeil, were collected from a 2%-foot section of surficial sandy limestone exposed 

abov& water level.

Land snails:

Polygyra sp. cf. P. cereolus (Muhlfeld) var. floridana Hemphill? 

Succinea sp. (very inflated) aff. S. campestris Say?

Under the heading "Fort Thompson beds," Sellards (1919, p. 

71-73) included alternating fresh-water and marine marl and limestone of Pleistocene age in the vicinity of La Belle and Fort Thompson 

in Hendry County. Cooke and Mossom (1929, p. 211) later changed 

the name to Fort Thompson formation. On the basis of invertebrate 

fossils and stratigraphic position, the unnamed Pleistocene strata 

of this report are correlated with the Fort Thompson formation.
90 CONTRIBUTIONS TO THE GEOLOGY OP URANIUM

Distribution. The Pleistocene strata are 

Auger holes disclosed that they cover the entire area, except -wfeere 

stream erosion has bared the older rocks or where Recent sediments 

are present. Vertical exposures are found along Payne's Creek, Peace 

River (fig. 10), Charlie Apopka Creek, Horse Creek, and Joshua Creek. 

In each drill hole, similar lithology and degree of weathering were 

noted in the surficial sediments. Pebbles of phosphate from the basal 

conglomerate were observed in the cuttings from several holes. The 

thickness of the Pleistocene strata is variable, but it generally does not 

exceed 20 feet.

Origin. The general character of the Pleistocene strata suggests 

deposition in the lower reaches of a river flood plain. Aggrading 

streams, threading channels across a flat plain close to sea level, 

spread a thin veneer of silt and fine sand on the interfluvial areas 

during floods. Channel sediments are characterized by lenticular 

bodies of sand and clay and by crosslamination. Scattered occurrences 

of fresh-water limestone were deposited in flood-plain lakes.

It is possible that part of these beds was deposited in a subaerial 

deltaic environment. In an area of such low relief and poor exposures 

it is difficult to determine where the flood plain ends and where the 

delta begins. Regardless of the precise environment, the evidence is 

clear that the unit was deposited by subaerial agents not far from a 

Pleistocene strand.

Although no evidence exists of any Pleistocene marine invasions in 

this area, there is abundant evidence of invasions at other places in 

the Atlantic Coastal Plain. Flint (1940, p. 757-787) critically examined the literature dealing with Atlantic Coastal Plain sediments of 

Pleistocene age. South of the James River in Virginia he found that 

morphologic evidence favored widespread marine deposition; north of 

the James the sediments are regarded largely as alluvial.

SEDIMENTS OF RECENT AGE

At many places along the banks of the Peace River and its tributaries, exposed stream terraces are clearly younger than the Pleistocene deposits (figs. 7 and 8). Included with these deposits are the 

"river-pebble" phosphate gravels that were mined prior to 1908.

These stream sediments are not extensive. They are confined 

chiefly to the present banks of streams (pis. 1 and 2) . The dominant 

lithology is fine quartz sand, with a negligible amount of clay. Phosphate occurs in sand to cobble size. At many places along the Peace 

River near Nocatee, Arcadia, and Brownville, the sediments of Recent 

age consist of natural levees of fine white quartz sand which line 

both banks. Phosphate, concentrated in bars and shoals in the 

Peace River, is abundant from Brownville southward,
STRATIGRAPHY, DE SOTO AND HARDEE COUNTIES, FLORIDA 91

These river sediments are not conspicuously weathered. The 

stratigraphic position, fresh appearance, and limitation of these sediments to present stream courses indicate that they are of Recent 

age. An outcrop on Horse Creek along the east bank of the stream, 

about 8 miles west of Arcadia, on Florida State Highway 72 (loc. 

32-53, pi. 1 and fig. 11), shows the contact of a Recent stream deposit 

with Pleistocene strata.

A'

________ _____________ ^r-j^, __ _

«f '- ^^^^M^^^^^^^^j^^^^^^

' f>

vK. Of Hoasl c»£tK

EXPLANATION

Quartz sand Quartz sand and Clayey sand 

phosphate nodules

FIOUKE 11. Plan and profile sketch of exposure along Horse Creek, at bridge on Florida Route 72, De

Soto County.

MECHANICAL. ANALYSIS

Mechanical analyses of the Pleistocene deposits, the sand of late 

Miocene age, and the undifferentiated phosphatic sand and clay were 

made to determine the existence of significant differences in grain 

size and to see whether such differences were characteristic of the 

formation or whether they were merely local variations. Striking and 

consistent interformational differences in median diameter of quartz 

sand, for example, would be useful for correlation purposes in instances 

where fossils were lacking or where lithology and sedimentary features 

were altered and obscured by the effects of weathering.

Sampling was done on a lithologic basis. Each sample represents 

a lithologic unit, regardless of thickness. Samples ^from 12 auger 

holes were submerged in muriatic acid for 24 hours, weighed, and 

screened for 7 minutes in a mechanical shaker. Samples, before
92 CONTRIBUTIONS TO THE GEOLOGY OF URANIUM

sieving, weighed approximately 60 grams. The samples were run 

through the following screen sizes:

Mesh size

(in mittiTyler screen no. meters')

20_______-----____.__ 0. 833

28 . . . 589

35____----_-___________._. . 417

48 

Mesh size

(in mffliTyler screen no. meters)

65-_ -------------------- 0. 208

100-____________________ . 147

150 _--------_---_----____ . 104

_____________________ .295 200_ _-_---_-_-_-_____ .074

All material below 0.074 mm (200 mesh) was discarded. All soluble 

components had been dissolved in the acid, therefore only quartz 

sand and a minor amount of accessory heavy minerals were screened. 

For each sample, a cumulative curve was plotted from which the 

median-grain diameter was determined (pi. 3).

The results of the work described in this section are not considered 

absolute values for these sediments. Certain inaccuracies were introduced because of the possible contamination of the auger cuttings. 

Even though the method of sampling was not precise, any consistent 

differences in grain-size distribution among the various sediments 

would still be valid.

The average of the median-grain diameters from all samples was 

computed for each formation. The table below summarizes the 

results:

Median-grain size (in millimeters) _ __

Pleistocene 

deposits

0. 174

Sand of late 

Miocene age

0.210

Undifferentiated 

phosphatlc sand 

and clay

0.244

All of the above averages are within the fine-sand range (0.125- 

0.250 mm) of the Wentworth grade scale. Slight differences such as 

these are not considered significant in themselves; however, an inspection of the cumulative curves for drill holes 62, 75, 86, 90, 99, and 124 

(pi. 3) shows a slight but very noticeable increase in grain size of the 

sediments underlying the surficial material. The finer grain size of 

the Pleistocene deposits seems to be consistent throughout this area. 

In each drill hole, except 117 and 85, the median-grain diameter of 

the sand of the Pleistocene deposits is less than that of the sand of late 

Miocene age or of the Undifferentiated phosphatic sand and clay.

GEOLOGIC HISTORY 

MIOCENE

Submergence during the middle Miocene was extensive, and much of 

peninsular Florida was inundated. The Hawthorn formation was 

deposited in this shallow marine environment. The recession of the
STRATIGRAPHY, DE SOTO AND HARDEE COUNTIES, FLORIDA 93

middle Miocene sea, probably accomplished in part by crustal upwarping associated with the closing stages of the Ocala uplift (Cooke, 

1945, p. 5-7), exposed the Hawthorn formation to weathering and 

erosion as far south as Hardee County and perhaps as far as De Soto 

County. A drainage system, similar in pattern to present drainage, 

was developed on this land surface, and a weathered residuum of the 

less soluble components of the limestone slowly accumulated. This 

mantle consisted of phosphate nodules, clay, and quartz sand. Periodic fluvial reworking of the residual weathered products occurred 

during this time.

During late Miocene time, the sea again advanced, and all of the 

southern part of the Florida peninsula, including De Soto County and 

possibly all of Hardee County, was submerged. The Tamiami formation and the Buckingham marl of Mansfield record this inundation in 

southern Florida. Slightly later, as the sea transgressed farther 

inland, the sand of late Miocene age was deposited in the more shallow 

water to the north. If the Bone Valley formation is of marine origin, 

it was deposited in this sea.

PLIOCENE

Marine deposition in Florida during the Pliocene epoch is marked by 

the Caloosahatch.ee marl. There is no knowledge of an important 

erosion interval after the late Miocene. Shallow Pliocene seas covered 

all of southern Florida and extended at least as far north in this area as 

southern De Soto County (pi. 1). There is no evidence of an extensive 

submergence during Pliocene time. The Caloosahatchee marl has not 

been found at altitudes of more than 40 to 45 feet.

PLEISTOCENE

After withdrawal of the Caloosahatchee sea, much of peninsular 

Florida was exposed. The post-Pliocene exposure was of brief duration, as evidenced by the fact that much of the thin Caloosahatchee 

marl is still preserved; furthermore, the upper part of the Caloosahatchee is relatively fresh and unweathered.

The retraction and release of tremendous volumes of water during 

glacial and interglacial stages caused extraordinary fluctuations in sea 

level during Pleistocene time. Elsewhere in Florida, and northward 

into Georgia, the Carolinas, Virginia, and Maryland, terraced Coastal 

Plain sediments present more graphic evidence of oscillations of sea 

level during the Pleistocene than is exhibited in Hardee and De Soto 

Counties. The Pleistocene strata in this area were deposited by the 

aggrading Peace River while the sea was at a higher level than at 

present. No precise record of earlier and higher stands of the sea 

during the Pleistocene is present here, although Cooke (1945, p. 245-
94 CONTRIBUTIONS TO THE GEOLOGY OF URANIUM

312) and MacNeil (1950, p. 95-107) mapped shorelines elsewhere in 

Florida at elevations of more than 100 feet. These shorelines represent pauses during the latest general retreat of the sea.

RECENT

The stream deposits of Recent age indicate very little change from 

the present environment. Terraces are not more than 15 feet above 

water levels in the streams. The Peace River and its tributaries are 

incised and are establishing a new base level adjusted to the present 

strand.

The Recent history of this area has been essentially a minor readjustment of the drainage to present sea level. Accelerated erosion of 

the Bone Valley formation, the Hawthorn formation, and the Hawthorn residuum in the region to the north is reflected hi the accumulations of "river-pebble" phosphate in the streams south of Brownville, 

De Soto County.

ECONOMIC CONSIDERATIONS

Field studies and radiometric analyses of samples indicate that the 

phosphate and uranium resources of the area covered in this report are 

unimportant under present economic conditions.

Examination of samples of the undifferentiated phosphatic sand and 

clay showed a substantially lower percentage of phosphate nodules 

than is characteristic of the phosphorite in the mining district to the 

north. Phosphate is a minor constituent in the sand of late Miocene 

age, Caloosahatch.ee marl, and the Pleistocene deposits.

Prospecting data in this region are nonexistent. Mansfield (1942, p. 

35) noted that there was no prospecting information available in regard to the area south of T. 34 S., Hardee County. Exploration since 

1942 has been concentrated in the land-pebble phosphate district, and 

the writer could find no record of recent prospecting in Hardee County.

The aluminum phosphate zone of the phosphorite is thin and discontinuous in this area. It cannot be considered a significant source of 

uranium. The low phosphate content in the sediments is a further 

deterrent to consideration of this area for uranium possibilities.

A total of 135 unsieved samples were analyzed radiometrically for 

percent equivalent uranium. The results ranged from less than 0.001 

percent to 0.009 percent. The summarized values are shown below:

Percent 

equivalent 

Number of samples uranium

16 ________-_-_____ 0. 004 

23____.__.__________ . 003 

36______ _ __________ . 002 

13.______.__________ . 001 

27____________ _ __ _ _____<. 001

Number of samples 

1_ . ____ _ __ _

3_

4 ____ _ ______

6

Percent 

eguivalent 

uranium

________ 0. 009

_-__-.__ .008

________ .007

___ ___ .006

________ .005
STRATIGRAPHY, DE SOTO AND HARDEE COUNTIES, FLORIDA 95

The average of the percent equivalent uranium for each stratigraphic 

unit was determined from the 135 samples. The results appear as 

follows:

Percent

equivalent

Formation uranium

Pleistocene deposits_______________________ _____ _ 0. 001

Caloosahatchee marl______________________________________ . 003

Undifferentiated phosphatic sand and clay_____________________ . 003

Upper Miocene deposits.________________________________________ . 002

Hawthorn formation..._____________________________ . 003

G. R. Mansfield (1942, p. 24-27) reported that "river-pebble" 

phosphate was mined in the Peace Eiver from 1888 to 1908. Competition from the land-pebble and hard-rock districts, rather than 

depletion of reserves, was responsible for the death of this industry. 

Large, but unmapped, reserves of low-grade "river-pebble" phosphate 

are still present in De So to County in the lower reaches of the Peace 

River and Joshua, Horse, and Prairie Creeks.

LITERATURE CITED

Cooke, C. W., 1939, Scenery of Florida, interpreted by a geologist: Fla. Geol. 

Survey Bull. 17, p. 14.

 1945, Geology of Florida: Florida Geol. Survey Bull. 29.

Cooke, C. W., and Mossom, Stuart, 1929, Geology of Florida: Fla. Geol. Survey

20th Ann. Rept. 

Ball, W. H., 1892, The Neocene of North America: U. S. Geol. Survey Bull. 84.

 1903, Contributions to the Tertiary fauna of Florida, with especial reference 

to the Miocene silex beds of Tampa and the Pliocene beds of the Caloosahatchie River: Wagner Free Inst. Sci. Trans., v. 3, pt. 6.

Eldridge, G. H., 1893, A preliminary sketch of the phosphates of Florida: Am. 

Inst. Min. Eng. Trans., v. 21, p. 196-231.

Flint, R. F., 1940, Pleistocene features of the Atlantic Coastal Plain: Am. Jour. 

Sci., v. 238, no. 11, p. 757-787.

Gardner, Julia A., 1926, The molluscan fauna of the Alum Bluff group of Florida: 

U. S. Geol. Survey Prof. Paper 142-A, p. 1-3.

 1945, Three new species from an upper Miocene oyster reef in Tampa Bay:

Nautilus, v. 69, no. 2, p. 37-41. 

Heilprin, Angelo, 1887, Explorations on the west coast of Florida and in the

Okeeehobee wilderness: Wagner Free Inst. Sci. Trans., v. 1, 134 p. 

MacNeil, F. S., 1950, Pleistocene shorelines in Florida and Georgia: U. S. Geol.

Survey Prof. Paper 221-F, p. 95-107. 

Mansfield, G. R., 1942, Phosphate resources of Florida: U. S. Geol. Survey Bull.

934. 

Mansfield, W. C., 1932, Pliocene fossils from limestone in southern Florida: U. S.

Geol. Survey Prof. Paper 170, p. 43-56.

 1939, Notes on the upper Tertiary and Pleistocene mollusks of peninsular

Florida: Florida Geol. Survey Bull. 18. 

Matson, G. C., 1915, The phosphate deposits of Floriad: U. S. Geol. Survey Bull.

604. 

Matson, G. C., and Clapp, F. G., 1909, A preliminary report on the geology of

Florida, with special reference to the stratigraphy: Fla. Geol. Survey 2d Ann.

Rept., p. 25-173.
96 CONTRIBUTIONS TO THE GEOLOGY OF- URANIUMMatson, G. C., and Sanford, Samuel, 1913, Geology and ground waters of fla,:

U. S. Geol. Survey Water-Supply Paper 319. 

Parker, G. G., 1951, Geologic and hydrologic factors in the perennial yieid of the

Biscayne aquifer: Am. Water Works Assoc. Jour., v. 43, no. 10, p. 817-833. 

Parker, G. G., and Cooke, C. W., 1944, Late Cenozoic geology of southern Florida,

with a discussion of the ground water: Florida Geol. Survey Bull. 27, p. 56-64. 

Richards, H. G., 1938, Marine Pleistocene of Florida: Geol. Soc. America Bull.,

v. 49, p. 1267-1296. 

Schroeder, M. C., and Bishop, E. W., 1953, Foraminifera of late Cenozoic in

southern Florida: Am. Assoc. Petroleum Geologists Bull., v. 37, no, 9, p.

2182-2186. 

Sellards, E. H., 1915, The pebble phosphates of Florida: Fla. Geol. Survey

7th Ann. Rept. 

 1916, Fossil vertebrates from Florida; a new Miocene fauna; new Pliocene

species; the Pleistocene fauna: Florida Geol. Survey 8th Ann. Rept., p.

91-95, 144.

1919, Geologic sections across the Everglades of Florida: Fla. Geol.

Survey 12th Ann. Rept., p. 67-76. 

Simpson, G. G., 1929, The extinct land mammals of Florida: Fla. Geol. Survey

20th Ann. Rept., p. 229-279. 

 1930, Tertiary land mammals of Florida: Am. Mus. Nat. History Bull.,

v. 59, art. 3, p. 149-211.
INDEX

Alum Bluff beds............

Anadara gunteri. . .... .... .

lienosa _________ .

sp... ....................

Anomia simplex. _____ .

Apheloj}&--- .- --- - ---- -

uflcetts; S&ewffeKa. ..........

arafa, CttrtHfa. ... .... .. ... .

Arta^wayfteriana

Area zone __ .. _ -.... _ .

arcinella, Echinochama ...... .

athleta, Chione _ . _ __ .

Balanus sp.._. __ ._.... ....

buckinghamenis, Chlamys

eboreut ...... . ...

caloosaensis, Phaeoides..- ...

Caloosahatchee marl, fauna.

lithologie character. _ .

origin........ _ .........

stratigraphic relations. ..

Campeldma sp. . . f *. _ ."..:.

Cancettaria macneili ...... ....

st>...... .................

eancettata, Chione. ... .... ..

Cardita arata .... ........ .....

sp...... .................

Cardium malacum.... ......

sp

Cardium (Trachycardium) sp

cereolus floridana, Polygyra..

Chattahoechee formation ....

Chione athletf ____ . __ .

can#Kl%jjf. -.---.---.. ....

chipolana ... .. ... ... .... .

sellardsi............. .....

sp............. ...... _ .

Chipolabeds __ ... ___ .

chipolana, Chione ... .... . ...

CWamjws<Bfe»toiBfe ...... ...

eboreus watson&nsis- . . ...

hanist.. ........... ... ...

nicolsi. ... . ... ..... .... ..

sp.. ....................

Chlamys (Plagioctenium)

hamensis.........

(Plagioctenium) sp .......

contractus, Phaeoides.... ... ..

Conussp. .... ..... ..... ...

densata, Plicatula ..... ... ....

disparilis, Ostrea...... ...... .

Dosinia sp. ____ . _ ....

duryi, Helisoma (Seminolina)

Page

 ... -...-... 69,70

 .. 73

. . ..... 86

 ... 72

. ............. 86

...-..... ..... 88

 .. . .. 85,86

. . . 86

. ............... 85

. . .-..... 72

 -.. -....... 85

 .. 85

 .. -..... 76,77,85

(Plagioctenium)

................. 85

 . . - 86

. .. 85,86

84

 ....... 86

 . . 84,85-86

89

................. 72

72

.. ....... 85,86

 . ......- 86

. . .. ... 78

................. 72

. ........-.., 73,78

.. . 72

......--.-..-.... 89

69

.. ............ 85

 .... .-...., 85,86

_ _ . . 73

-....-.-.-.-..-. 72

..... -... . 72,73

 ..-. ....... 69,70

................. 73

 . .. .. 76

...... ........... 76

................. 86

................. 73

.-. . . 72,. 73, 78

eboreus Lucking-

................. 85

 . ..-. 76

................. 73

- . . 86

 .. .... 73

....... .......... 76

....... .......... 73

89

Page

eboreus buckinghnmensis, Chlamys 

(Plagioctenium)............................. 85

Echinochama arcinella......................... 85,86

Fconomic importance Of mineral resources.... 94-95

Ecphora n. sp.____.____._ . 76

floridana, Polygyra cereolus. 89

gedrgianvs, Viviparus......................... 89

Cftycymeris subovdta........................... 72

sp... . . - - . 72,73

gunteri, Anadttra. 73

hadra, Venericardia........................... 72

harrtti, Chlamyt.............................. 86

Hawthorn formation, fauna.____ . ... 71-73 

history of name_ _ 69-70 

lithologic character.._ .. 70-71 

origin.._ - ---- 73

stratigraphic relations __ - __ 69-70,71,72f 73 

Helisoma (Seminolina) duryi. 89 

himerta, Venericardia...............j 72

Jacksonville limestone. 69

Laevicardiumsp.... 76

leidyi, Strombus..... 85

limota, Anadara......... 86

Location of the area.. 65,66,67

macneili, Cancettaria.......................... 72

malacum, Cardium...................... .--. 72

Manatee River marl 69 

Mechanical analyses of sediments- 91-92 

Merychippvssv ............ 79

Miocene epoch, geologic history 92-93 

monroensis, Ostreatamiamiensis........... 76

Neohipparionsv .... . 79,88 

nicolsi, Chlamys............. ...... ...... 73

Onfc 0ra?«.aaad. 69

Oliva say ana.................................. 86

Ostreadisparilis. 76

meridionalis.. .......................... 76

puelchana...... 78

tamiamiensis monroensis.................. 76

virgrnica.................................. 86

sp......... -. - 78

perattenuata, Turritella........................ 85,86

Phaeoides caloosaensis......................... 86

contractiM...................... .... 73

sp ..................................... 73

97
98 INDEX

Page

Phosphate resources, economic importance__ 94,95

Phosphatic sand and clay, fauna..__ -..- _ 81

lithologic character..-.._________ 80

origin.....:____ ____,___ 83-84

stratigraphic relations.... _____ 79-80,81-83

(Plagioctenium) eboreus buckinghamensis,

Chlamys......................... 85

Pleistocene deposits, fauna. _________ 88-89 

lithologic character ____________. 87-88 

marine terraces_____________ 86-87 

origin...._________________ 90

Pleistocene epoch, geologic history_____. 93-94 

Plicatula densata.............................. 73

sp._----- .... . . .__ 73

Pliocene epoch, geologic history...._____ 93

Pododesmus n. sp...._.. _________ 76

Polygyra cereolusfloridana.................... 89

sep'emvolva oolvexis........................ 89

puelchana, Os>rea............................. 78

Purpose of the investigation.. _______ 67

Rangia sp. ____________________ 89 

Rapana...................................... 76

Recent epoch, geologic history________ 94 

Recent sediments.. __ ______ 90-91

Sand of late Miocene age, fauna...____ 75-76,78 

lithologic character....___________ 75

origin. ._._.________________ 78-79

stratigraphic relations...______ 73-75,76-78

sayana, OHva................................. 86

sculpturata. Ostrea............................ 86

sellardsi. Chime. ............................. 72

Semicassis.................................... 72

(Seminolina) duryi, Helisoma................. 89

Page

septemvolsa volvcxis, Polygra................... 89

Serridentinus floridanus....................... 75

Shoal River formation_____._____ _. 69

simplex, Anomia.............................. .86

Sopchoppy limestone. .. 69

Spisula....................................... 78

Stratigraphic section, on Horse Creek, near

Arcadia.. .... . . 91

on Peace River, near Wauchula.. __ 82

Stratigraphy, summary___--..-..__ 70

Strombusleidyi.-- ....................... 85

subanniUata, Turritetta ..........,____ 86

subovata, Olycymeris... ___________.. 72

Succinea campestris........................... 89

tamiamiensis mmroensis, Ostrea............... 76

Tampa beds__________.________ 69,70 

Teleoceras fossiger............................. 79

Tetrabelodm.................................. 79

( Trachycardium )sp., Cardium................ 72

Turritetta apiealis..............-.._._ 85,86

perattenuata..........................- -.. 85,86

subannulata. 86

Uranium resources, economic resources... 94-95

Venericardia hadra............................ 72

himerta................................... 72

sp. 72,73

Venus sp _____ . 73,78 

eirginica, Ostrea............................... 86

Viriparus georgianus.......................... 89

volvoxis, Polygyra septemvolva.. ............... 89

wagneriana, Area. 85

U. S. GOVERNMENT PRINTING OFPICEl I9»»