Citation
Stratigraphy and paleontology of the late Neogene strata of the Caloosahatchee River area of southern Florida ( FGS: Bulletin 40 )

Material Information

Title:
Stratigraphy and paleontology of the late Neogene strata of the Caloosahatchee River area of southern Florida ( FGS: Bulletin 40 )
Series Title:
Florida Geological Survey: Bulletin
Creator:
Florida Geological Survey
DuBar, Jules R
Place of Publication:
Tallahassee
Publisher:
Published for the Florida Geological Survey
Publication Date:
Language:
English
Physical Description:
267 p. : illus. tables, 12 pl. ; 24 cm.

Subjects

Subjects / Keywords:
Geology -- Florida ( lcsh )
Caloosahatchee River ( local )
Hendry County ( local )
Glades County ( local )
City of Miami ( local )
Alligator Creek ( local )
Charlotte County ( local )
Marl ( jstor )
Species ( jstor )
Eggshells ( jstor )
Fossils ( jstor )
Fauna ( jstor )
Genre:
non-fiction ( marcgt )

Notes

Funding:
Geological bulletin (Tallahassee, Fla.)
General Note:
Series Statement: ( FGS: Bulletin 40 )
Statement of Responsibility:
[by] Jules R. DuBar.

Record Information

Source Institution:
University of Florida
Holding Location:
Government Documents Department, George A. Smathers Libraries, 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:
021333215 ( aleph )
01728190 ( oclc )
AKM4760 ( notis )

Full Text









STATE OF FLORIDA
STATE BOARD OF CONSERVATION

Ernest Mitts, Director


FLORIDA GEOLOGICAL SURVEY

Robert 0. Vernon, Director







GEOLOGICAL BULLETIN NO. 40





STRATIGRAPHY AND PALEONTOLOGY OF
THE LATE NEOGENE STRATA OF THE
CALOOSAHATCHEE RIVER AREA
OF SOUTHERN FLORIDA





JULES R. DuBAR









Published for
THE FLORIDA GEOLOGICAL SURVEY
Tallahassee
1958















FLORIDA STATE BOARD

OF

CONSERVATION








LeROY COLLINS

Governor


R. A. GRAY
Secretary of State



J. EDWIN LARSON
Treasurer



THOMAS D. BAILEY
Superintendent Public Instruction


RICHARD ERVIN
Attorney General



RAY E. GREEN
Comptroller



NATHAN MAYO
Commissioner of Agriculture


ERNEST MITTS
Director of Conservation




4 ?




2


q , ,, /,-/ 5










LETTER OF TRANSMITTAL


�JCoriaa qeoloqical Survey

'aakussee
May 27, 1958

MR. ERNEST MITTS, Director FLORIDA STATE BOARD OF CONSERVATION TALLAHASSEE, FLORIDA
DEAR MR. MITTS:
The Florida Geological Survey is publishing as Geological Bulletin No. 40, a report that was prepared by Dr. Jules R. DuBar and presented by him to the University of Kansas in partial fulfillment for the requirements of a Doctor of Philosophy degree. The report covers the geology of the Caloosahatchee River area in southwest Florida, including the Caloosahatchee marl and the Fort Thompson formation, geologically. These beds are important sources of water in the South Florida area and the report contributes a great deal of additional knowledge on the occurrence and distribution of these beds.
The Geological Survey appreciates your continued interest and cooperation in accomplishing the work delegated to it by the Florida Legislature.
Respectfully yours,
ROBERT 0. VERNON, Director







3


6 0 5 2




























































Completed manuscript received
February 28, 1957
Published for the Florida Geological Survey by
E. 0. Painter Printing Company
DeLand, Florida
May 27, 1958










ABSTRACT


This report describes late Neogene (post-Oligocene) deposits in the Caloosahatchee River area in southwestern Florida. Detailed stratigraphic relationships, relative age, and environments of deposition of the Caloosahatchee marl and the Fort Thompson formation are established. Both of these stratigraphic units are considered to be of Pleistocene age.
Examination of 60 insoluble residues and detailed quantitative and qualitative analyses of molluscan assemblages contained in 65 samples of sediments one cubic foot or less in volume have provided criteria helpful in recognition of members and facies, and interpretation of depositional environments. Comparison of fossil molluscan, echinoid, and coral assemblages with living communities in the Gulf of Mexico, Caribbean, and western Atlantic regions has yielded valuable data concerning the ecological factors, such as salinity, depth of water, temperature of water, and turbidity, which probably prevailed during the time in which the Caloosahatchee marl and Fort Thompson formations were deposited.
In southern Florida the Caloosahatchee marl rests unconformably on the Tamiami formation (upper Miocene). In most places the Caloosahatchee marl is less than 40 feet thick, but east of Ortona Locks it reaches a thickness in excess of 60 feet. The formation is composed of a succession of shallow-water marine and brackish-water marl, sandstone and limestone, and a few intercalated thin beds of fresh-water marl. Most of the beds were formed close to shore on the inner continental shelf or in bays and inlets, but the Bee Branch limestone (named for exposures near Bee Branch in Hendry County) represents a relatively deep water (15-20 fathoms deep) outer shelf environment. The Bee Branch member can be traced for many miles along the Caloosahatchee River.
Typically, the Fort Thompson formation, which overlies the marl unconformably, is represented by a sequence of alternating and intertonguing fresh-water and marine beds deposited along a fluctuating shoreline. The uppermost marine bed, the Coffee Mill Hammock marl, is the most extensively developed unit and was deposited in the shallow water (depth five fathoms) of a bay or inlet. The lower marine bed probably was deposited in a shallow bay (depth one fathom).







The Caloosahatchee marl, heretofore considered Pliocene in age, is assigned to the Pleistocene epoch. The most compelling evidence supporting a Pleistocene classification is derived from fresh-water, marine, and terrestrial vertebrate remains contained in the upper beds of the Caloosahatchee marl. Most of the vertebrate species have never been recorded from beds older than Pleistocene. The presence of Equus (Equus) cf. E. (E.) leidyi and Holmesina septentrionalis in the formation is regarded as strong evidence of a post-Kansan (probably Sangamonian) age. Paleoecological and paleogeographical studies indicate that the Caloosahatchee marl was deposited under tropical conditions suggestive of an interglacial period, and that the deposition of the formation should be, at least in part, correlated with the making of the Wicomico shoreline (100 feet above sea level) generally regarded to be Sangamonian in age.
The Fort Thompson formation is classified as Wisconsinan in age and it may have been deposited during a temporary recession of the Wisconsinan glaciers. Paleogeographical and paleoecological studies suggest that the formation should be correlated at least in part with the making of the Pamlico shoreline (25 feet above sea level).
The overlying Pamlico sands may represent, in part, littoral sediments deposited from the retreating Fort Thompson sea. The Lake Flirt marl, which overlies the Pamlico formation, is a Recent deposit.









ACKNOWLEDGMENTS


Gratitude is expressed to Dr. R. C. Moore, University of Kansas, who directed the research and criticized the manuscript. The Florida Geological Survey, under the direction of Dr. Herman Gunter, paid field expenses, and supplied an able field assistant, Roy Staton, and later paid expenses to compare the present collection with type collections at the U. S. National Museum in Washington, D. C., and the Philadelphia Academy of Sciences. At the U. S. National Museum, type collections and laboratory facilities were made available to the writer by Harald Rehder, David Nicol, and Druid Wilson. At the Philadelphia Academy of Sciences H. G. Richards made type collections available. David Nicol, Druid Wilson, and A. A. Olsson identified some molluscan species. John Wells identified the corals. Herbert Winters identified the terrestrial vertebrate fauna. Valuable ecological data concerning molluscan assemblages were furnished by T. E. Pulley. The writer's wife, Phyllis, assisted in the field and with the laboratory work, and also helped type the manuscript.


































TABLE OF CONTENTS
Page
Letter of Transmittal Abstract .. 5 Acknowledgm ents ---------------------------------------------------..---------------------------- - --.......... 7
P a r t I S tr a tig ra p h y ----- - -------------------------- ----------------------------------------------------- ------ 1 1
Part II Systematic Paleontology - 151 A ppendix -------- -------.-.---.----------------------------------------------......................--- - - - - - - - - - - - - - - - - - - 216























PART I

STRATIGRAPHY AND PALEONTOLOGY OF THE LATE NEOGENE STRATA OF THE CALOOSAHATCHEE RIVER AREA
OF SOUTHERN FLORIDA

STRATIGRAPHY













PART I



TABLE OF CONTENTS

Page
Introduction - - 19
Location and description of area - -- - -- 19
Geography -- - 19 Topography - 19
Purpose of investigation - -- - -- 22
Previous work - ----- 23
Present investigation -------------- ---- 25
Stratigraphy of southern Florida --------------------------- ........................-------------------- 27
G e n e r a l d is c u s s io n ........... . ..... . ..... . ................ . ...................... . .......... . .............- 2 7
L a te M io c e n e d e p o s its ---------------------------. ..- ---------. --........... ........... ........... ....... 2 9
Buckingham marl 29 Tam iam i form ation -------------------------------------------.-.--------- .................-- - - - - - - - - -- 29
D efi n ition - ---. --.-------.---------------- .............-- - - - ----------------- --------------------- 29
Lithologic character ---------30 Age-------------------- 31
Thickness --------------------------------- ...----.-...................---------------------------------. 31
O ld e r P le is t o c e n e d e p o s it s ................... . .........................................................- 3 4
Caloosahatchee m arl --------.--.--.......................------ ------------------------- - -- - 34
D e fi n it io n --- . . ....-------------------------------- ....... ..- - . .......... . ...-- - - .............. -.. . 3 4
Lithologic characteristics ---------------------------------------- --------------- ----------- 34
A g e ---- ------------------------------------------------------ - ---------- ---- - ---------------- - 3 5
T h ic k n e s s ---------------------------------------------------------- ---------------------- - ------ --- 3 5
D is t r ib u t i o n ... . ........................ . ............. . .................................... . .........- 3 5
Younger Pleistocene deposits -------------........................-------------- .- ------- --- --- 38
General discussion ---------------------------------------.-.---- ........................-- - - - - - - - - - - - - - -- 38
F ort T h om p son form a tion .................................................................--. 3 8
A nastasia form ation --------- ..............-----------.- --- .-- - - ----------------------. - ---- - 38
Key Largo limestone ---...----- ..---.-........................--------------------------------------- 39
M iam i oolite ------------------------------------------------------------------------------------------------ -- 39
P a m lic o f o r m a t io n ................................................. . .......................... - ------ 3 9
L a k e F l i r t m a r l ...... ..... ...... .. .... ..... ...... ... ...... . . . .. .. . ... ... ... . .... . ... ... ..... .- . ... ... . . 4 0
Stratigraphy of the upper Caloosahatchee River area west of Ortona Locks 40
G eneral observations -------------------------------------...................------ - ---------- ------ - 40
T a m ia m i f o r m a tio n ---------------------------------------------------------------------------..............-- 4 7
E xposures w est of F t. D enaud --------------------------------------------------------- 47
E xposures east of F t. D enaud ---------------------------- -------------------------------- 48
Nature of the Tamiami-Caloosahatchee contact -------------------------- - 49
Caloosahatchee marl -------------------------------------------------------.------------------------- 50
General discussion ---------------------------------------------------------------------------------------- 50
Lower Caloosahatchee beds ---------------------------------------------------------- ..---------- 50
General discussion ---------------------------------------------------------------------------------- 50








Cyrtopleura costata faunizo Basal oyster biostrome --------Fresh-water marls ----------------Bee Branch member
Upper Caloosahatchee shell bed
Fort Thompson formation ---------- -General discussion ----------------------Fresh-water deposits ------------------Marine deposits --------------.
General statement ................
Chlamys bed
Coffee Mill Hammock marl
Pamlico formation
Lake F lirt m arl -----------------------Stratigraphy of the Ortona Locks area
General observations ----------------------Caloosahatchee marl
Lower beds (units 1, 2, 3, 4) Lower limestone bed (unit 5)
Middle shell marl (unit 6)
Upper limestone (unit 7) --------Panope faunizone (unit 8)
Fort Thompson formation
Fresh-water marl (unit 9)
Coffee Mill Hammock marl (un
Subsurface stratigraphy along the Cal
General observations
Tamiami formation
Caloosahatchee marlFort Thompson formation ...............
Pam lico form ation -----------------------------P a leo ecolog y ---------------------------------------------G eneral discussion ...........................
Caloosahatchee marl-----------Cyrtopleura costata faunizone
General statement
Brackish-water facies
High-salinity shallow-water
Turritella facies
Lower oyster biostrome and rela
Oyster biostrome
Brackish-water beds -------------Bee Branch member --................
Upper Caloosahatchee shell bed
Invertebrate faunas .............
Vertebrate fauna ----- --------------


n e ------------------------------------------------------------ 5 3
. . ...... . .. . .... . . ........ . ............................ -... 5 5
..... ............. ....... . ......... ...............-----... .. .. .. 5 8
-- ---- - 58
---------------------------------------------------------------- 6 1
-. .-------- .--- - - ----------------------------------------- 6 4
---- ---- --- --- -- - ---------- --- ----- ---- - -- -- ----- ---- -- ------ - -. 6 4
.. ........ .... ...... ... ... ..... .. ... .......... .. ..... .. ..... .... . 6 6
- 70
- - - - -- - - - - -- - -- - - - - - - - - - - - - - - --- 7 0
--- - - - - - - - - - - - - - - - - - - - - - - - - ---- - --- 7 0
... ........... ............-- --....... ......... ...... ... ........ 7 1
-- -- -- - -- -- - -- -- - -- -- - --- - - - - - - --- ---- 7 1
- 74
---------------------------- -- - - - - - - -------------------------- 74
a ---------------- ---------------------------- --------- --------- 7 4
------- ----- --- ------ -. - .- .--- -- ---- -- --- -- - --- --- ---- -- ---- --- -- 7 4
76
76
------------------------------- - --- 80
-- -80
-- 80
S 81
82

it 10) 83
oosahatchee River ------------------------------ 83
88
--- 83

S 85
-------* ---------------- - - - - -- -- ------ 86
--- - -- ----- --- -- . - ---- -- - ---- --- -- --- ---- -- -----.- - ----- - -- - - 8 5


------------------------------ - - - -- -- 86


89
S~89
--------------------------------89
-- 90
bay facies - - - ---- 9
-- - -- -- - -95
ted strata -------- 97
---------- -------------------- --- 105 8
ba -ac e ---- - ------------ --- 107

te s r ta -- - ----------- ---- ------- 114
---------------. . ..------------------- ....--------------- ---- 1 0 5
--------------- - -------------- - ---------- - --- ------- - -------... 1 0 7
---------------------------------- -------- -- ---- -------- -------- 1 1 4
............................................................... 114
-------. -. -.--------------------- ------ ---------------------- ---- 1 2 2


F ort T h om p son form a tion ------------------------------------------------------------------............
C h la m y s b e d ----------------. .-----------------------------------..........-- ------------ ----------...
Coffee Mill Hammock marl ---------------------------------------------------------------........
G e n e r a l sta tem e n t .................................................................................
Type locality -------------.- .......................------------------------------------------Deposits west of the type locality ------------------------------------------------------








A g e r e la t io n s h ip s --------------------------------------------------------- ----------------------------------Age of the Caloosahatchee marl -----------------------------------.- --------------------G e n e r a l d iscu ssio n ------------------------------------------------.-.----------.................
Evidence of the invertebrate fauna -- -
Evidence of the vertebrate fauna ------------------------ ------------------------Relationship to Pleistocene marine shorelines
Correlation with other units -- - -
C o n c lu s io n s ----------------------- . ------------------------------------------------------------------------A ge of the Fort Thom pson form ation --------.-..-.---................................
Evidence of the fauna --------- ...------.-.-.-.- .......................------------------Relationship to the glacial and interglacial stages
Conclusions -------------------------------------------------------------------------------------Age of the Pamlico formation ----------------Sum m ary ------------------------------------------ - - - - -- ------------------.- ----------------------------------R eferen ces -----------------------------------------------------------------------------------------------------


-....... 136
--------- 136
.........- 13 6
137
------- 138
140
-- - 140
---------- 14 2
----- ---- 142
----- ---- 142
142
-- ----- 144
-- 144
---------- 14 4
---------- 14 6


ILLUSTRATIONS


Figure
1 Map of Florida showing location of area studied --2 Principal geographic features of southern Florida
3 View of the Caloosahatchee River west of the Atlantic Coast Line
Railroad bridge near Ortona Locks
4 Marl of the Tamiami formation exposed in a phosphate pit near Buckingham ----.-.---- ..............--- ----------------------- ..........................-- - --- - --- -5 Pool, located along Alligator Creek in Charlotte County, being drained to expose unconformable Tamiami-Caloosahatchee contact ---6 Unconformable contact between the Caloosahatchee marl and the Tamiami formation exposed along Alligator Creek in Charlotte
County ----- - -
7 Generalized stratigraphic section of the Caloosahatchee marl, Fort
Thompson formation, and the Pamlico formation in the area along the Caloosahatchee River between Coffee Mill Hammock and a point
approximately one mile west of Ft. Denaud ---------------8 Ind ex to geologic m ap p arts .......................................................................
9 Geology of the area adjacent to the Caloosahatchee River. Part A --10 Geology of the area adjacent to the Caloosahatchee River. Part B ---11 Geology of the area adjacent to the Caloosahatchee River. Part C ---12 Geology of the area adjacent to the Caloosahatchee River. Part D ---13 Argillaceous marl of the Tamiami formation exposed on the north
bank of the Caloosahatchee River near Alva .................. ......-........
14 Cyrtopleura costata faunizone near station A31 showing valves of
Cyrtopleura costata oriented in their burrows ----15 Caloosahatchee marl at station A27 showing oyster biostrome above
a local lens of lim estone ----------------------------------- ------------.. . -- - -------------------








16 Specimen of the Bee Branch limestone from the type locality -------- 59 17 Upper Caloosahatchee shell bed at station A35, one mile upstream f r o m F t. D e n a u d ----- -----------.----------------------------------------------------------............... 6 2
18 Specimen of upper Caloosahatchee shell bed from station A34, approximately 2.0 miles upstream from Ft. Denaud 63 19 Exposure of the Fort Thompson formation near the type locality ---- 65 20 Generalized cross section of Neogene beds exposed along the Caloosahatchee River east of La Belle - -- 67 21 Exposure of Fort Thompson and Pamlico deposits along Banana C r e e k --------------------------------------------------------------------- ...----- ......--- - --------------.- -- - 6 9
22 The Coffee Mill Hammock marl exposed near Fort Thompson ---------- 72 23 Correlation of strata exposed in the Ortona Locks area -- - - 75 24 Lower Caloosahatchee beds exposed near Ortona Locks 77 25 A specimen composed of the twisted shells of Vermicularia recta
from the Vermicularia faunizone near Ortona Locks - -- 78 26 Sample of marl from the Vermicularia faunizone near Ortona Locks 79 27 Specimen of marine marl (unit 4) from above Vermicularia
faunizone near Ortona Locks -- 79 28 Upper Caloosahatchee beds exposed near Ortona Locks - 81 29 Correlation of subsurface sections along the Caloosahatchee River
between Olga and Lake Hicpochee - -- 84 30 Relative abundance of the most common gastropod species included
in the principal facies of the Cyrtopleura costata faunizone -------------- 90
31 Relative abundance of the most common gastropod species included
in the principal facies of the Cyrtopleura costata faunizone -------------- 91
32 Relative abundance of the most common pelecypod species included
in the principal facies of the Cyrtopleura costata faunizone ----.........92
33 Relative abundance of the most common pelecypod species included
in the principal facies of the Cyrtopleura costata faunizone ------....... 93
34 Marl sample representing the Turritella facies of the Cyrtopleura
costata faunizone (station A 23) ------------------------ ---------------------- -- --------- 94
35 Relative abundance of the most common pelecypod species in beds
of the Caloosahatchee marl at station A23 on the Caloosahatchee
River about 1.5 miles downstream from La Belle ----------------------- ----- 96
36 Relative abundance of most common gastropod species in beds of
the Caloosahatchee marl at station A23 on the Caloosahatchee River,
about 1.5 miles downstream from La Belle -----.........................- --------- 97
37 Relative abundance of common pelecypod species in beds of the
Caloosahatchee marl at station A17 on Caloosahatchee River approxim ately 1.0 m ile upstream from La Belle --------------------------------------------- - - 101
38 Relative abundance of common gastropod species in beds of the
Caloosahatchee marl at station A17 on Caloosahatchee River,
approximately 1.0 mile upstream from La Belle ----------- ---------------------- 102
39 Brackish-water marl collected from station A35, approximately 1.0
mile upstream from Ft. Denaud ------ .....................---------- -------------------- 106
40 Relative abundance of most common pelecypod species in beds of









the Caloosahatchee marl at station A36 on Caloosahatchee River,
approximately 1.0 mile upstream from Ft. Denaud 108
41 Relative abundance of most common gastropod species in beds of
the Caloosahatchee marl at station A36 on Caloosahatchee River,
approximately 1.0 mile upstream from Ft. Denaud ------------------------------ 109
42 Sample of the upper Caloosahatchee shell bed collected from exposures approximately 1.0 mile upstream from Ft. Denaud ---------------- 114
43 Geographic distribution of several pelecypod species common in the upper Caloosahatchee shell bed -- ---- ------ - 115
44 Geographic distribution of several gastropod species common in the upper Caloosahatchee shell bed - - ---- 116
45 Relative abundance of most common pelecypod species in lower, middle, and upper portions of the upper Caloosahatchee shell bed at station A28 on the Caloosahatchee River about 1.7 miles downstream
from L a B elle ----------------------------------------------------------------------------- - - - - -- - 117
46 Relative abundance of most common gastropod species in the lower,
middle, and upper portions of the upper Caloosahatchee shell bed at station A28 on the Caloosahatchee River about 1.7 miles downstream from L a B elle -----....---------------------.-.--- ....--- ........................-- - - - - - - . . 118
47 Sample of the Coffee Mill Hammock marl collected from an exposure
at Old Lock N o. 3 ------ ------------------------ ......... ..-- - - - - ---------------- ----------- 126
48 Generalized geologic cross section near station A33 - -- 134
49 Vertebrate fossils being removed from Fort Thompson deposit (sand facies of the Coffee Mill Hammock marl) at station A33 on Caloosahatchee River approximately 2.0 miles upstream from Ft. Denaud --- 136
Plate
1 Correlation of stratigraphic sections along the Caloosahatchee River:
part A - ---------------- -- In pocket
2 Correlation of stratigraphic sections along the Caloosahatchee River:
part B ----------------------------.--------.-------..--------................----------------- ----- In pocket
3 Correlation of stratigraphic sections along the Caloosahatchee River:
part C ----------------------.-----.----. ---------------... .............--------- ---- ------------- - In pocket
4 Correlation of stratigraphic sections along the Caloosahatchee River: part D ----------.-.-------------.-.-.....................----------------------------- -------------- - In pocket
Table
1 Correlation of Neogene deposits of southern Florida -- - -- - 28
2 Insoluble residue analyses of several lower Caloosahatchee marl
samples collected at stations located between Ortona Locks and
F t. D enaud -----------------------------.-.-.-.------------ ....---------- ....- .... ........--------- - - - - -- 52
3 Insoluble residue analyses of several Bee Branch rock samples
collected at stations located between Ortona Locks and Ft. Denaud ---- 60
4 Insoluble residue analyses of several upper Caloosahatchee shell bed
rock samples collected at stations between Fort Thompson and
Ft. D enaud -----------------.-.------------------ .................-------------------------- - ---- ------.64
5 Recent Gulf of Mexico oyster reef faunal assemblages collected off
the coast of T exas --------------------------- ...------------- --------------------------. - ----------- - 103
6 Species of the Continental Shelf in the Mississippi Delta Region
identical with or similar to species of the Bee Branch member ---------- 112








7 Vertebrate fossils from the upper Caloosahatchee shell bed - 122
8 Most abundant marine molluscan species of the Chlamys bed compared with those of the type Coffee Mill Hammock marl 124 9 High-salinity bay and inlet molluscan species from the Texas coast -_ 132 10 Most common Coffee Mill Hammock marl molluscan species at several
localities along the Caloosahatchee River --------------- - ------------------------------ 133










Part I


STRATIGRAPHY AND PALEONTOLOGY OF
THE LATE NEOGENE STRATA OF THE
CALOOSAHATCHEE RIVER AREA
OF SOUTHERN FLORIDA

STRATIGRAPHY

INTRODUCTION

LOCATION AND DESCRIPTION OF AREA GEOGRAPHY
The area investigated for this study lies in southwestern Florida (fig. 1, p. 20; fig. 2, p. 21) between latitudes 270 N. and 26� N.; it is bounded on the west by the Gulf of Mexico and extends eastward approximately to longitude 810 W. This is an area of more than 3,000 square miles that includes large parts of Charlotte, Glades, Lee, Hendry, and Collier counties. Field studies mostly were in narrow strips bordering highways, canals, and streams where exposures are best developed and most accessible.
From the north the area can be reached by U. S. highways 41, 17, and 27. State highways 78 and 80 cross the area in a general east-west direction, more or less paralleling the Caloosahatchee River. Bridges span the Caloosahatchee River at Moore Haven, La Belle, Ft. Denaud, Alva, Olga, and Ft. Myers. From the south the area is accessible by means of the Tamiami Trail (U. S. Highway 41) and by U. S. Highway 27 to the east, and State Highway 29 to the west. Alligator and Shell creeks, both in Charlotte County, can be reached on U. S. Highway 41. There are few secondary roads in southwestern Florida; consequently many localities were visited by using a small boat.

TOPOGRAPHY

Physiographically the area investigated is a part of the Coastal Lowlands and is a nearly featureless plain everywhere less than 71 feet above sea level. The highest elevations, 25 to 70 feet above sea level, are northeast and east of Charlotte Harbor and south of the Caloosahatchee River on the Talbot and Penholoway terraces.







FLORIDA GEOLOGICAL SURVEY-BULLETIN FORTY


Figure 1
Map of Florida showing location of area studied.
Along the Caloosahatchee River the elevation seems nowhere to exceed 25 feet above sea level (Parker and Cooke, 1944).
The area is drained principally by the Caloosahatchee River (fig. 3, p. 22), its tributaries, and canals. The river, which originally headed in Lake Hicpochee, has been lengthened artificially and now heads in Lake Okeechobee. The river empties into the Gulf of Mexico behind Sanibel and Pine islands near Punta Rassa. The lower part of the river between its mouth and Tice is drowned. Tides are detectable upriver as far as Ortona Locks in Glades County.
Another drowned drainage system centering on Charlotte Harbor lies north of the Caloosahatchee. This system includes the Myakka River and Peace, Shell, and Horne creeks. In places, along


0 60 120
Miles


80







LATE NEOGENE STRATA OF SOUTHERN FLORIDA


Figure 2
Principal geographic features of southern Florida.
Shell and Alligator creeks in Charlotte County, 15 to 20-foot sections of Neogene sediments have been exposed.
According to Parker and Cooke (1944, pl. 8) three topographic divisions are in the study area. These include portions of the sandy flatlands, Big Cypress Swamp, and the Everglades. The sandy flatlands are defined as "low-lying, defectively drained lands, generally flat though parts on higher terraces are gently rolling." This division covers extensive areas both north and south of the Caloosahatchee River. Many shallow depressions in the sand are ponds and much of the land is flooded during rainy seasons.
A part of the Everglades occurs along the south and southwest borders of Lake Okeechobee and surrounds old Lake Hicpochee.







FLORIDA GEOLOGICAL SURVEY-BULLETIN FORTY


Figure 3
View of the Caloosahatchee River west of the Atlantic Coast Line Railroad bridge near Ortona Locks.
This division is described as an "almost dead flat surface, generally wet throughout the year except where drained." The area is underlain by peat, muck, and marl. The division is mostly treeless, but is covered with a tall sedge (Mariscus jamaicensis). The Everglades-Okeechobee depression and the local basins therein probably represent original sea floor irregularities and depressions subsequently modified by ground water solution.
The Big Cypress Swamp occupies much of Collier County, and the southern half of Hendry County south of the Caloosahatchee River. The area is described (Parker and Cooke, 1944, pl. 8) as "flat, poorly drained, with thin marly or mucky and sandy soils and bare areas of solution riddled limestone." Palmetto and pine covered dry areas, termed hammocks, are scattered throughout the swamp. The wet areas are characterized by small cypress, sedges, and typical swamp plants.
The divisions are transitional one to the other and consequently boundaries are indistinct.
PURPOSE OF INVESTIGATION
The aim of this report is to present a stratigraphic and paleontological analysis of some of the late Neogene beds and faunal







LATE NEOGENE STRATA OF SOUTHERN FLORIDA


assemblages that occur in southwestern Florida. Special emphasis is placed on the Caloosahatchee and Fort Thompson formations in the Caloosahatchee River area. The river area was selected for detailed study because it affords the best, thickest, and laterally most extensive exposures of these strata in southern Florida. Due to the excellent state of preservation of the fossils, which are abundant in these sediments, they are used in this report to interpret the paleoecology of these rocks. Many of the species are extant in Floridan waters and could be used as ecologic indicators.
Former studies in this area were mostly paleontologic; other biological aspects were usually neglected. Long lists of species from the area have been compiled by several workers (Dall, 18951903; Mansfield, 1939) but the precise stratigraphic significance of the species was never established. An attempt is made here to determine individual species or assemblages that can serve as guides to formations or faunizones.

PREVIOUS WORK

Until 1886, when Angelo Heilprin explored the Caloosahatchee River, few geological observations had been made in peninsular Florida, especially in its southern half where not even the broader geological aspects were known before that time.
Agassiz (1852) and Le Conte (1857, 1878) theorized that the peninsula was constructed almost entirely of Recent coral reef material. Le Conte (1857, p. 48) thought that coral islands such as the Florida Keys rose above sea level as a result of the piling of broken coral heads and sand by hurricane produced waves.
Timothy Conrad's descriptions in 1846 of fossils from the Tampa limestone near Tampa may have been the earliest critical observations on the geology of the State.
In 1879 J. L. Meigs, a United States Government engineer, led an exploratory expedition up the Caloosahatchee River. At that time little was known even of Lake Hicpochee and Lake Okeechobee. Meigs and several members of his crew penetrated the swamps to within one-fourth mile of Lake Okeechobee, but were forced by adverse conditions to turn back.
Sailing aboard a schooner in 1886, Heilprin (1887) completed the first geological study of the "Okeechobee wilderness." He collected fossils from along the Caloosahatchee River and concluded, on the basis of the ratio of extinct to extant molluscan species, that the lower beds should be assigned to Pliocene age. These beds he designated the Floridan. The upper shell beds, now known as the







24 FLORIDA GEOLOGICAL SURVEY-BULLETIN FORTY

Fort Thompson formation, he called the "Venus cancellata bed." His studies resulted also in a complete refutation of the "coral reef hypothesis" for the origin of the Floridan peninsula.
William Healy Dall (1887) visited southern Florida in 1887 and made studies along the Caloosahatchee River, Shell Creek, and other streams. He assigned a Pliocene age to the lower strata, but described them under the name "Caloosahatchie beds." In his great monograph, "Tertiary Fauna of Florida" (1895-1903) he described and pictured many of the fossils of the Caloosahatchee formation.
Matson and Clapp (1909) published the first geologic map of the State. In the same paper (p. 123-128) they described the Caloosahatchee formation.
Sellards (1919a) made geologic studies in the Everglades along newly cut drainage canals. He described (p. 71-74) the Fort Thompson beds, Coffee Mill Hammock marl, and the Lake Flirt marl.
Cooke and Mossom (1929), who were the first geologists to cross the Tamiami Trail, published an account of the geology of Florida and a geologic map of the State on a scale of 1:1,000,000. Cooke (1945) completely revised the earlier edition and the map. The later edition includes a correlation table of Florida formations and maps indicating hypothetical shorelines for the various Cenozoic stages.
A correlation chart of Cenozoic formations of the Atlantic and Gulf Coastal Plains was published in 1943 by Cooke, Gardner, and Woodring.
The work of Parker and Cooke (1944) presents a valuable summary of late Cenozoic geology of southern Florida. In addition to a discussion of all formations of the region, it includes descriptions of stratigraphic sections occurring along the Caloosahatchee River, logs of test wells drilled in southeastern Florida, cross sections of subsurface geology, and maps depicting geology, topography, ecology, surficial deposits, etc.
Several papers by Mansfield (1931, 1932, 1939) appeared in the decade 1930-1940. They represent important contributions to Neogene (post-Oligocene) stratigraphy and paleontology. Included are descriptions of new fossil species, faunal checklists, and opinions on the paleoecology. Also he proposed the name Buckingham limestone for beds believed to be uppermost Miocene, and the name Tamiami limestone for beds in Collier and Monroe counties thought by him to be lowermost Pliocene.







LATE NEOGENE STRATA OF SOUTHERN FLORIDA


Richards (1938) studied the Pleistocene stratigraphy and paleontology. ,
The foraminiferal fauna has been studied by Cole (1931), Cushman and Ponton (1932), and more recently by Schroeder and Bishop (1953), and Puri.1
Marine Pleistocene terraces of Florida have been discussed by several authors (Cooke, 1930, 1931, 1935, 1941; Flint, 1942; MacNeil, 1949).
In the past five years several papers have been published (Parker, 1951; Hoy and Schroeder, 1952; Schroeder and Klein, 1954) that are more or less concerned with problems of southern Florida stratigraphy.
A major contribution to the revision of the taxonomy of Caloosahatchee mollusks was made by Olsson and Harbison (1953) in their paper on the Pliocene mollusks of the St. Petersburg area.

PRESENT INVESTIGATION

The summer of 1953 was spent in the field for the purpose of studying the Caloosahatchee, Fort Thompson, Pamlico, Lake Flirt, and Tamiami formations. One hundred exposures, which include 70 measured sections, were examined. Five-foot samples from 18 auger holes drilled in this area in 1954 were also examined. Some work was done on spoil banks, along canals, and drainage ditches. Every effort was made to deduce the stratigraphic sequence from the type and position of materials in the piles.
Samples of the faunal remains were taken from a number of localities. These collections were of two types. In the case of hard limestones or marls, or where detailed collecting was not considered necessary, only selected forms were taken. In many instances, especially where softer marls were encountered, an attempt was made to obtain a quantitatively representative fauna. To accomplish this about 0.5 to 1 cubic foot of matrix was shoveled or otherwise dug from the desired bed, sacked and labeled. To reduce shipping bulk and weight, some of the large samples were "rough washed" in the field.
Continuous exposures along the Caloosahatchee River from Ortona Locks, Glades County, to a point about one mile downstream from Ft. Denaud in Hendry County were studied.
To obtain as complete a section as possible, critical exposures were studied at low tide. The, rainy season and subsequent high


'Personal communication, 1955.







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water hampered work in the lower reaches of the river. Whenever possible, samples of submerged beds were obtained by diving. All drainage canals and large cutoff meanders confluent with the Caloosahatchee located between Moore Haven and Olga were explored.
About 60 bulk samples, each approximately 0.5 cubic foot in volume, were analyzed in detail. The first step usually consisted in washing and then drying the samples. Generally, it was found sufficient to boil the materials in plain water or a sodium hydroxide solution. This process released and cleaned the shells for additional study. Once dried, the mollusks were identified and counted. The larger specimens were identified and tabulated first. The remaining material was divided into four or eight equal parts. Everything in the aliquot portion was then identified and counted. These totals were then multiplied by four or eight and added to the count of the larger specimens. Later, percentages were calculated for all species.
The faunas were also analyzed stratigraphically and paleoecologically. Ecologic data were obtained from available literature. The writer studied Recent mollusks found on the beaches and in shallow water along the coast of North Carolina near Beaufort, and along the southwest coast of Florida. This data is used in deducing the paleoecology of the Neogene sediments. Insoluble residue analyses were made of about 60 samples. The rock was first broken and 20 g. were placed in a beaker. Commercial hydrochloric acid diluted to 20 percent was slowly poured over the sample. After effervescence had ceased, acid was added to make certain that all soluble material had been digested. After a period of 24 hours, the acid was decanted and the residue washed. The residue was then introduced into a 1,000 ml. beaker and permitted to settle for 4 minutes and 46 seconds through a five-inch column of water. Under these conditions sediment with a maximum diameter greater than 1/64 mm. would have settled to the bottom. The water was decanted and the process repeated to catch smaller particles which previously had been carried to the bottom. After drying, the samples were weighed. In each case the weight of the beaker was subtracted from that of the beaker plus sediment. Thus the volume by weight of the coarse fraction (larger than 1/64 mm.) and the fine fraction (smaller than 1/64 mm.) was determined. The total weight of the residue subtracted from 20 g. gives the weight of the soluble material. Percentages of the three fractions indicating volume by weight were calculated.







LATE NEOGENE STRATA OF SOUTHERN FLORIDA


STRATIGRAPHY OF SOUTHERN FLORIDA


GENERAL DISCUSSION


Beds older than Miocene are not known to outcrop in southern Florida; however, deep wells have penetrated the Cretaceous (Cooke, 1945, p. 23) at several localities in the Everglades. The Neogene beds comprising Miocene and younger strata, are relatively thin; the thickness of most formations may be measured in tens of feet, although the Hawthorn formation is several hundred feet thick. Most of the region is covered by a thin veneer of late Pleistocene sands, marls, and muck, and several marine terraces have been recognized.
The beds of the southern part of the Peninsula are little deformed. The dominant surface structure in Florida is the Ocala uplift where the Ocala group (upper Eocene) is exposed at the surface. According to Parker and Cooke (1944, p. 18), sediments of this group lie 150 feet above sea level in Marion County and 1,200 feet below sea level in Monroe County, 250 miles to the south. This represents a dip of about five feet to a mile. Parker and Cooke (1944, p. 19) believed that the asymmetry of the Florida plateau suggests deformation. The eastern portion of the plateau extends under the water of the Atlantic only a short distance, whereas the western half extends approximately 100 miles into the Gulf of Mexico. As a result southern Florida actually represents only the southeastern portion of the plateau. Shallow depressions, such as the basin occupied by Lake Okeechobee and the undulations observed in the beds along the Caloosahatchee River, probably represent irregularities in the old sea floor.
With some exceptions, general accord prevails concerning application of Neogene formational terminology in Florida. However, there is no general agreement regarding correlation of the formations. This is partly due to scarcity of exposures and of subsurface data in critical areas. Many so-called facies of formations, for instance, have not been observed to grade into one another.
A correlation chart of Cenozoic formations of the Atlantic and Gulf Coastal Plains (table 1) has-been prepared by Cooke, Gardner and Woodring (1943). The classification of Neogene deposits of southern Florida as used in this report appears on table 1 (p. 28).









TABLE 1
CORRELATION OF NEOGENE DEPOSITS OF SOUTHERN FLORIDA
Cooke, Gardner and Woodring, 1943


Present study


Wisconsinan


Sangamonian



Illinoian Yarmouthian Kansan Aftonian Nebraskan


Peorian Iowan


Lake Flirt marl Pamlico sand


Miami Key Largo Anastasia Talbot fin. oolite Is. fm. Penholoway fm.
Wicomico fm.


Lake Flirt marl Pamlico sand Fort Thompson Anastasia
fm. fm.


Caloosahatchee
marl


Miami Key Largo oolite ls.


Talbot fm. ? Penholoway fm. Wicomico fm.


No record Sunderland fm. No record No record No record


No record


No record


Upper Caloosahatchee marl Tamiami limy
(Astian) sandstone facies No record

Lower Buckingham marl member
(Plaisancian) No record


Upper No record Tamiami fm. Bone Valley fm.?


I I


1-. -1








LATE NEOGENE STRATA OF SOUTHERN FLORIDA


LATE MIOCENE DEPOSITS

BUCKINGHAM MARL

The name Buckingham limestone (fig. 4, p. 29) was proposed by Mansfield (1939, p. 8) for a "limestone cropping out in Lee County, Florida." The type locality is a quarry near State Highway 25, half a mile west of Orange River, Lee County, Florida (sec. 5, T. 44 S., R. 26 E.). Mansfield considers the formaion to be uppermost Miocene. These beds were assigned to the Choctawhatchee formation by Matson and Clapp (1909). Parker and Cooke (1944) revived the Buckingham marl which they -consider Pliocene in age, and defined it to comprise an argillaceous deeper-water facies of the Caloosahatchee formation. Parker (1951, p. 823) included the Buckingham limestone of Mansfield in the Tamiami formation, and considers it to be of upper Miocene age.

TAMIAMI FORMATION

Definition
Mansfield (1939, p. 3) proposed the name Tamiami "limestone" for a bed found in ditches along State Highway 41 in Collier and


Figure 4
Marl of the Tamiami formation exposed in a phosphate pit near Buckingham.







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Monroe counties. He described its lithology " . . . mainly dirty white to gray, rather hard, porous, non-oolitic limestone with inclusions of clear quartz." The fauna, as reported by Mansfield, included species of foraminifers, bryozoans, barnacles, six genera of gastropods, 15 genera of pelecypods, and two genera of echinoids. On the basis of the fauna, he tentatively placed the formation at the base of the Pliocene, just below the Caloosahatchee marl.
Sanford (1909, p. 222-224) earlier had noted the same rocks, naming them the Lostmans River limestone, from exposures near the headwaters of that stream. He considered the formation to be older than the Miami oolite (Pleistocene). Cooke and Mossom (1929, p. 207) rejected this name and placed the sediments referred to Lostmans River limestone into the Caloosahatchee marl in the north and Miami oolite in the south.
Parker and Cooke (1944, p. 64) changed the name to Tamiami formation because the rock contains too much sand to be considered a limestone. Parker (1942, p. 64-66) correlated the Tamiami formation with the highly permeable rocks, previously assigned to the Pleistocene or Pliocene, which underlie the Miami oolite on the Atlantic Coastal Ridge and considered that the Tamiami beds overlie the Caloosahatchee formation.
Parker (1951, p. 823) redefined the Tamiami formation to include the "Tamiami limestone," the "Buckingham limestone" of Mansfield, and the upper portion of the Hawthorn formation as delimited by Parker and Cooke (1944, p. 98-122). As a result, all Miocene beds exposed in southern Florida are now included in the Tamiami formation. This classification is followed here.
The upper beds found in the subsurface of Broward and Dade counties, which had been previously assigned to the Tamiami formation (Parker and Cooke, 1944, p. 62-63) were referred to the Fort Thompson formation by Hoy and Schroeder (1952, p. 283286).

Lithologic Character

The Tamiami formation is represented by several facies in southern Florida. Along the Tamiami Trail it is a light colored hard limestone with poorly preserved fossils. At Buckingham, in Lee County, it is a phosphatic, argillaceous shell marl (fig. 4, p. 29) ; along Alligator Creek, in Charlotte County, it is a relatively unconsolidated sandy shell bed composed in large part of remains of the echinoid Encope macrophora tamiamiensis and clusters of a large species of Balanus. At Sunniland, Collier County, the







LATE NEOGENE STRATA OF SOUTHERN FLORIDA


Tamiami formation is represented by a soft, gray limestone which contains an excellent echinoid fauna and abundant molds, casts, and shells of mollusks. In subsurface along the Caloosahatchee River in Glades and Hendry counties, the formation contains beds of olive green clay and sand, most of which are almost devoid of megafossils.
The insoluble residue of a sample of the Tamiami formation where it is exposed near Buckingham, Florida, is 11.5 percent by weight, of which 73.9 percent by weight is coarser than 1/64 mm. The sand is composed of quartz grains of which most are very fine and angular, but a few grains are well rounded and greater than 2 mm. in diameter. Grains of intermediate size have not been observed.

Age

Schroeder and Klein (1954, p. 4) stated that in the western Everglades, the Tamiami formation overlies the Hawthorn formation where the Hawthorn has been penetrated. Well records show this relationship to be true also for the Buckingham area and Dade County. The nature of the contact is generally assumed to be unconformable. Along Alligator Creek in Charlotte County (fig. 5, p. 32; fig. 6, p. 33), the Tamiami formation can be seen to be unconformably overlain by the Caloosahatchee formation.
According to Schroeder and Klein (1954, p. 4), ". . . the faunal assemblage of the Tamiami formation commonly contains the mollusks Ostrea disparilis, Chione ulocyma, and Turritella pontoni, which F. Stearns MacNeil (1951, personal communication) states ' . . . are not only characteristic upper Miocene species, but they represent groups that have no known post-Miocene relatives, at least in this part of the world.'" The echinoid Encope macrophora tamiamiensis, according to Cooke (1942, p. 20-21), is not known in any beds other than those now called Tamiami formation. One specimen of Ecphora quadricostata umbilicata (Wagner) was found in the Tamiami formation along Banana Creek in Hendry County. This is a typical upper Miocene gastropod which is common in the Ecphora facies of the Choctawhatchee in West Florida.

Thickness

The thickness of the Tamiami formation ranges from approximately 40 to 100 feet. At Buckingham it is about 40 feet thick (Parker and Cooke, 1944, p. 61) and according to Schroeder and









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Figure 5
Pool, located along Alligator Creek in Charlotte County, being drained to
expose unconformable Tamiami-Caloosahatchee contact.








































Figure 6
Unconformable contact between the Caloosahatchee marl and the Tamiami formation exposed along Alligator Creek in Charlotte County. Pointed finger marks the base of Caloosahatchee marl.


J4







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Klein (1954, p. 4), it is about 50 feet thick at Sunniland, Collier County, and 100 feet in Dade County. Test holes drilled along the Caloosahatchee River show the maximum thickness to be at least 60 feet.

OLDER PLEISTOCENE DEPOSITS

CALOOSAHATCHEE MARL

Definition

Lower shell beds exposed along the upper portion of the Caloosahatchee River were assigned to the Pliocene by Heilprin (1887, p. 32) and termed the Floridan beds. Dall (1887, p. 161170) considers the deposits to be Pliocene, but refers to them as the Caloosahatchee beds or marls. Matson and Clapp (1909, p. 123) adopted the name Caloosahatchee marl, and subsequently this designation has been generally accepted and used.
Beds of the Caloosahatchee marl exposed along Shell Creek, Myakka River, and Alligator Creek were noted by Dall (1892, p. 140-149; 1903, p. 1603-1605). Recognition of the Caloosahatchee marl was extended by Cooke and Mossom (1929, p. 152) northward from the type area into Volusia and Putnam counties where it was defined to include beds called the Nashua marl. Earlier, Mansfield (1924, p. 34-35) had noted the strong similarity of the Nashua mollusks to those of the Caloosahatchee marl. Of 28 identified species from the Nashua marl, Mansfield found that 25 percent occur in the Caloosahatchee and 59 percent in the Recent fauna.
All the dominantly marine strata of southern Florida which are younger than the Tamiami formation and older than the Fort Thompson formation are placed in the Caloosahatchee formation. At most localities the formation can be recognized easily by its diagnostic faunal assemblage.

Lithologic Characteristics

Typically, beds of the Caloosahatchee formation consist of marls composed primarily of quartz sand, silt, and shells. Most of the strata are soft or only slightly indurated, but some are calcareous and very hard, so as closely to approach the nature of true limestone. Most layers are moderately to abundantly fossiliferous, although some, especially sands, are almost or completely barren. Fresh exposures are generally light colored with white, light gray, cream and buff predominating. In the subsurface many







LATE NEOGENE STRATA OF SOUTHERN FLORIDA


sand layers are light green to olive green. Weathered marls are usually medium to dark gray.

Age

The Caloosahatchee marl is here assigned to the Pleistocene. This is done primarily on the basis of the vertebrate fauna and to a lesser degree on the molluscan fauna and stratigraphic relationships. The age of the formation is discussed in detail later in the paper.

Thickness

The base of the Caloosahatchee formation is not exposed in many places, and subsurface data are not abundant. Well records show that the thickness of the Caloosahatchee marl is less than 50 feet in most areas investigated. In many places it is completely absent, having been eroded away, or at some localities never deposited. The typical Caloosahatchee beds were deposited in a shallow sea. The Tamiami formation seems to have been eroded and well dissected by subaerial agents; consequently the Caloosahatchee deposits are thickest where they fill the depressions and tend to thin over high areas. At several localities along the Caloosahatchee River Caloosahatchee strata transgressively wedge out on the flanks of Tamiami hills. Probably many islands and peninsulas composed of older sediments rose above the level of the Caloosahatchee sea.

Distribution

According to the geologic map of Florida (Cooke, 1945), the Caloosahatchee marl is exposed throughout much of southern Florida in the approximate latitude of Lake Okeechobee, and extends in patches along the east coast as far north as Putnam County, slightly beyond latitude N. 290 30'. On the west coast the marl has been traced only to the Tampa area in Pinellas County, at approximately latitude N. 280. Actually, the Caloosahatchee marl does not crop out in many places and is generally covered by 10 to 20 feet or more of younger marine and fresh-water beds. Well records indicate that the Caloosahatchee formation lies at shallow depth in subsurface throughout most of southeastern Florida.
The type exposures of the Caloosahatchee marl are found along the Caloosahatchee River between Ft. Denaud and Ortona Locks







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(fig. 2, p. 21) and, according to Cooke (1945, p. 221), the formation underlies most of Hendry County. He indicates on his map that the beds crop out throughout most of the area. The writer found few exposures immediately south of the river and none along State Highway 833 that leads to the Big Cypress Seminole Indian Reservation in the southeastern corner of the county. All along this route the surface is underlain by a thin silty solution-riddled limestone and thin beds of clay, unconsolidated sands, and shell beds, that closely resemble those of the Fort Thompson formation.
A series of 43 test holes, extending from Lake Hicpochee on the north, along the western edge of the Everglades in Hendry and Dade counties to the Tamiami Trail on the south, were drilled by the U. S. Corps of Engineers. The cuttings were analyzed by Schroeder and Klein (1954) and cross sections were prepared to show the subsurface stratigraphic relationships. The cross sections indicate that in the northeastern part of Hendry County the Caloosahatchee marl is covered by five to thirty feet of younger sediments and is not exposed anywhere. In the south, along parts of Hendry County, the Tamiami formation is overlain by Fort Thompson beds and the Caloosahatchee marl is absent.
Cooke stated (1945, p. 224) that no exposures of Caloosahatchee marl are known in Palm Beach County but Parker and Cooke (1944, p. 96) report that a well at Bean City, just south of Lake Okeechobee, was drilled to the Caloosahatchee marl and limestone at about 25 feet below the surface. In another well at Fifty-TwoMile Bend the drill entered the formation at about 25 feet below the surface. At both places the overlying beds belong to the Fort Thompson formation and in neither area was the bottom of the formation reached. The penetrated thickness was about 25 feet.
From their study of well cores, Parker and Cooke (1944, p. 97-101) reported that the Caloosahatchee is known from the subsurface of Broward County. In that area the thickness appears to be about 10 feet. The underlying beds have been identified as belonging to the late Miocene Tamiami formation. Schroeder and Klein (1954, p. 3) described five to 15 feet or more of Caloosahatchee sands, sandstone, and marls from subsurface studies in the northwest corner of Broward County. These beds lie at or slightly below sea level and are overlain by the Fort Thompson formation and underlain by beds of the Tamiami formation.
In Martin County, Cooke (1945, p. 223) reported the occurrence of Caloosahatchee fossils from spoil piles along the banks of the St. Lucie Canal between Port Mayaca and Indiantown. The







LATE NEOGENE STRATA OF SOUTHERN FLORIDA


exposed beds belong to the Anastasia formation. He also reported (1945, p. 223-224) Caloosahatchee fossils from shallow wells in Orange and Osceola counties.
Good exposures of the Caloosahatchee formation are found in the vicinity of Charlotte Harbor, the best being located along the banks of Shell Creek and Alligator Creek in Charlotte County. Cooke reported (1945, p. 216) that a pit at the head of Prairie Creek in DeSoto County has yielded specimens of Strombus leidyi, Arca wagneriana, and Anadara rustica. The author was unable to find any typical Caloosahatchee fossils from the spoil piles at this location; the pit is now filled with water.
A pit at Acline in Charlotte County has yielded a peculiar fauna which has been considered equivalent to the Caloosahatchee formation by some workers but is thought to be late Miocene by Druid Wilson.2 The fauna includes species not found elsewhere and some which have been recorded most commonly or exclusively from the Caribbean region. Unfortunately, the pit is now filled with water and the exposures are no longer accessible.
Along Shell Creek there are shell beds 10 to 15 feet thick, which contain an excellently preserved Caloosahatchee fauna. Dall (1903, p. 1604) listed 256 molluscan species from this locality of which 59 percent are extant and seven percent are not found elsewhere. These same beds are seen in a ditch along the upper stretch of the south fork of Alligator Creek to overlie the Tamiami formation unconformably (fig. 6, p. 33). The uppermost beds contain mostly extant species and perhaps should be included in the Anastasia formation.
In Polk and Hillsborough counties a phosphatic marl and conglomerate known as the Bone Valley formation occurs. Cooke (1945, p. 206) regarded it as an estuarine-deltaic deposit formed in a sea which opened to the south. He concluded that it is a facies of the Caloosahatchee and Pliocene in age. Vertebrates constitute the dominant faunal elements and considerable doubt may be expressed concerning their true chronological significance. Probably the formation is Miocene, and there seems to be no convincing evidence that it is a facies of the Caloosahatchee formation.
Cooke (1945, p. 231) considered the so-called Citronelle formation of the lakes region of central Florida as a near-shore and beach facies of the Caloosahatchee formation, but this view remains to be proved.


2Personal communication, 1955.







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YOUNGER PLEISTOCENE DEPOSITS
GENERAL DISCUSSION
Late Pleistocene deposits constitute a thin but nearly continuous blanket of sediment over most of southern Florida. Several formations are recognized, though only the Fort Thompson and Pamlico formations and the Lake Flirt marl are found along the Caloosahatchee River in the area investigated.
Other southern Florida Pleistocene formations include the Miami oolite, Key Largo limestone, Anastasia formation, and various terrace formations recognized by Cooke (1945).
FORT THOMPSON FORMATION
Sellards (1919a, p. 71) proposed the name Fort Thompson beds for ". . . deposits consisting of alternating fresh- and brackishwater and marine marls and limestones . . . ." The type locality is along the Caloosahatchee River at Fort Thompson, about 1.5 miles upstream from La Belle. According to published records, the first geologist to see this formation was Angelo Heilprin when he visited the area in 1886. Heilprin referred to the uppermost marine unit as the "Venus cancellata bed" which he considered post-Pliocene but he seemingly included the lower fresh-water units in the Pliocene. Dall (1887, p. 143) also referred to the upper marine rocks as post-Pliocene, but regarded the "Planorbis beds" below as Pliocene in age.
The most typical fossil in the marine layers is Chione cancellata, and Helisoma scalare is characteristic of the fresh-water beds.
Although best exposed along the Caloosahatchee, the Fort Thompson formation extends beyond the river area throughout much of the southern Lake Okeechobee region, and Palm Beach and Broward counties and seems to grade laterally into the Anastasia formation and Miami oolite.
The formation is thin; it does not exceed 30 feet in thickness and usually bears an unconformable relationship to the beds below and above. Most commonly the underlying strata belong to either the Caloosahatchee marl or the Tamiami formation. The formation is overlain by the Pamlico formation or Lake Flirt marl in areas where no outcrops exist.
ANASTASIA FORMATION
Sellards (1912, p. 18) applied the name Anastasia formation to exposures of coquina ". . . on Anastasia Island opposite St. Augustine, which extend along the coast south from this point a distance







LATE NEOGENE STRATA OF SOUTHERN FLORIDA


of 150 miles or more." He described the lithology as consisting of more or less water-worn shells which may or may not be cemented to form a firm rock. He considered the formation contemporaneous, or partly so, with the Miami oolite and other Pleistocene deposits of the southern coast of Florida. Cooke and Mossom (1929, p. 199) add that ".... the coquina includes almost everywhere a little quartz sand, and at some places quartz sand may be almost the sole constituent of the Anastasia formation."
Deposits along the west coast between Marco Island and Tampa Bay have been included in the Anastasia formation by Parker and Cooke (1944, p. 66). The formation is thin (10 feet or less) and according to Parker and Cooke (1944, p. 66) merges with the upper marine member of the Fort Thompson formation in the Caloosahatchee River valley west of Denaud, although this relationship was not observed by the writer.

KEY LARGO LIMESTONE

Sanford named and described the Key Largo limestone in 1909 (p. 214-218). It consists primarily of reefs of dead corals located between Bahia Hondo and Miami, Florida. Cooke (1945, p. 263) states that "... it is contemporaneous with the Miami oolite."

MIAMI OOLITE

Cooke (1945, p. 256) stated that the name Miami oolite was first used by Sanford in 1909 to describe a limestone in the southeastern Florida mainland and is a thin, pure, light colored oolitic limestone best developed in the counties of Dade and Monroe. According to Cooke (1945, p. 259), the bottom rests on the Tamiami formation in the Everglades. This formation does not occur in the Caloosahatchee River area, but Cooke (1945, p. 259) thinks that it merges with the Coffee Mill Hammock marl.

PAMLICO FORMATION

The name Pamlico was given by Stephenson (1912, p. 286-290) to a deposit of sand, clay, and other unconsolidated sediment found at Pamlico Sound, North Carolina. Parker and Cooke (1944, p. 7475) included in the Pamlico formation all marine Plesitocene deposits of Florida that are younger than the Anastasia formation. Generally the Pamlico formation lies at an elevation of 25 feet or less above sea level. Most characteristically it is a barren quartz sand but locally may include a molluscan faunal assemblage.







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The Pamlico formation, in most places only a few feet thick, is widespread in southern Florida, especially around Lake Okeechobee and constitutes the uppermost bed at most localities along the Caloosahatchee River.
Cooke (1945, p. 117) thought that the formation was approximately middle Wisconsin in age, and thus the youngest of the terrace deposits recognized by him.

LAKE FLIRT MARL

Sellards (1919a, p. 73-74) introduced the name Lake Flirt marl for a fresh-water "calcareous mud" overlying the Coffee Mill Hammock marl along the Caloosahatchee River near Fort Thompson. He suggested that the marl is Recent and that deposition continued until a few years ago when the lake was drained. Typically the marl contains abundant gastropod remains, of which Helisoma is characteristic.


STRATIGRAPHY OF THE UPPER CALOOSAHATCHEE RIVER AREA WEST OF ORTONA LOCKS

GENERAL OBSERVATIONS

This section of the report deals primarily with upper Neogene beds exposed along and near the Caloosahatchee River between Coffee Mill Hammock in Glades County and a point approximately one mile west of Ft. Denaud in Hendry County. Within this area the exposed beds belong to the Caloosahatchee marl, Fort Thompson formation, Pamlico formation, Lake Flirt marl, and in a few places to the Tamiami formation. A diagram showing the generalized stratigraphic section of the Caloosahatchee marl, Fort Thompson formation, and Pamlico formation is given below (fig. 7, p. 41). A map of the geology of the upper Caloosahatchee River area is presented in four parts (fig. 9-12, p. 43-46) and is preceded by an index map showing the location and relationship of the four parts (fig. 8, p. 42). An analysis of 12 test holes drilled along the river between Olga and Lake Hicpochee is also included.
The exposures are mostly confined to the river banks and usually do not exceed 10 feet in thickness. The beds are undulatory and alternately rise above and dip below water level. Many sections were measured and studied, and the descriptions of some of


















isel-


1I-


5r


2 -


LATE NEOGENE STRATA OF SOUTHERN FLORIDA


VERTICAL SCALE
,,19 -


FORMATIONS


0I ..,..,,,.. ,

Figure 7
Generalized stratigraphic section of the Caloosahatchee marl, Fort Thompson formation, and the Pamlico formation in the area along the Caloosahatchee River between Coffee Mill Hammock and a point approximately one mile west of Ft. Denaud.

















GLADES COUNTY


HENDRY COUNTY


SCALE IN MILES

1 0 1 2 3 4


Figure 8
Index to geologic map parts (fig. 9, 10, 11, 12).












HENDRY COUNTY


FORT THOMPSOI VERTEBRATE
LOCALITY


HENDRY COUNTY


0


SCALE


Figure 9


GEOLOGY OF THE AREA

ADJAGENT TO THE

CALOOSAHATCHEE RIVER

PART A














































Figure 10



















OLD LOCK NO. 3


GLADES COUNTY


GLADES COUNTY


HENDRY COUNTY


1 MILE


SCALE


Figure 11


GEOLOGY OF THE AREA

ADJACENT TO THE

CALOOSAHATOHEE RIVER

PART C















GLADES COUNTY


GLADES COUNTY


SCALE


Figure 12


-GEOLOGY OF THE AREA

ADJACENT TO THE

CALOOSAHATCHEE RIVER


PART D







LATE NEOGENE STRATA OF SOUTHERN FLORIDA


the most significant sections are included in the appendix. Charts (pl. 1-4) showing proposed correlation are included in a folder attached to the inside of the back cover of the report. Location of the stratigraphic sections may be ascertained from the geologic map (fig. 9-12).

TAMIAMI FORMATION

EXPOSURES WEST OF FT. DENAUD

The Tamiami formation (fig. 13, p. 47) rises above water level approximately 0.5 mile downstream from Ft. Denaud in Hendry County. Most beds of the Caloosahatchee marl pinch out on the flank of the Miocene exposure, but the Bee Branch member can be traced for a mile or more downstream to a point where it, too, appears to wedge out. If the upper shell bed or higher Caloosahatchee units were ever deposited over the Tamiami formation west of Ft. Denaud, they have been removed by erosion.
Most of the Tamiami beds exposed west of Ft. Denaud are relatively hard light colored calcareous sandy clays or argillaceous


Figure 13
Argillaceous marl of the Tamiami formation exposed on the north bank of
the Caloosahatchee River near Alva.







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marls. Fossils are abundant in some beds but are usually preserved as casts and molds. Most beds contain shells of species of Chlamys, Ostrea, Anomia, and Balanus.
The following is a list of mollusk species identified by Mansfield (1939, p. 46-58) from Tamiami beds exposed west of Ft. Denaud:

Pelecypoda
Nuculana sp.
Navicula occidentalis Philippi?
Navicula umbonata Lamarck?
[Anadara] lienosa Say
[Anadara] scalaris Conrad var.?
Ostrea meridionalis Heilprin
Ostrea disparilis Conrad
Pecten ochlockonegnsis legnis Mansfield
Pecten wendelli olgensis Mansfield
[Chlamys] caloosensis Mansfield
[Chlamys] eboreus buckinghamensis Mansfield
[Chlamys] nodosus floridensis Tucker and Wilson
Lima (Mantellum) carolinensis Dall
Anomia simplex d'Orbigny
Placunanomia plicata Tuomey and Holmes
Thracia (Cyathodonta) sp.
Venericardia olga Mansfield
Phacoides chrysostoma (Meusehen) Philippi
Chione ulocyma Dall
Chione latilirata athleta Conrad

EXPOSURES EAST OF FT. DENAUD

Upstream from Ft. Denaud clay beds form three arch-like exposures along the banks of the Caloosahatchee River. All three exposures are located between Ft. Denaud and Fort Thompson and are considered to represent erosional remnants of the Tamiami formation. In each of the areas, beds of the Caloosahatchee marl transgressively pinch out on the flanks or become thin and change facies over the crest of the underlying Tamiami deposits.
The largest of the Tamiami exposures occurs in the vicinity of La Belle. A greenish-gray plastic sandy clay is visible in the river banks between station A19 (one mile upstream from La Belle bridge) and station A22 (0.75 mile downstream from La Belle bridge). No megafossils were collected from the exposed clays, and only a few fragments of mollusks and barnacles were observed in the auger hole samples. All units of the Caloosahatchee marl wedge out on the flanks of this Tamiami exposure except a sandy, sparsely fossiliferous facies of the Bee Branch member.
A much smaller exposure of Tamiami deposits barely rises above low-water level in the immediate vicinity of station A24 (approximately 1.75 miles downstream from La Belle bridge). The exposed







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beds consist of a gray arenaceous clay from which the author collected a few specimens of Ostrea subdigitalina Olsson and Harbison and Ostrea cf. 0. tamiamiensis Mansfield. No oysters similar to these species were collected from the Caloosahatchee beds. Olsson and Harbison (1953, p. 51) record 0. tamiamiensis from Ortona Locks but do not give the stratigraphic position. All other records of 0. tamiamiensis and its subspecies appear to be from the Tamiami formation. The type specimen of 0. subdigitalina was collected from the Tamiami formation on Hickey's Creek near Olga, Lee County, Florida, and Olsson and Harbison (1953, p. 47) report specimens from Snell Island, St. Petersburg. The lower Caloosahatchee beds transgressively wedge out on the flanks of the exposure, but the Bee Branch member, considerably reduced in thickness, and the upper shell bed pass over the top without interruption. A test hole drilled close to station A24 penetrated Tamiami sediments 30 feet beneath the surface.
A third small remnant of the Tamiami formation is exposed in the vicinity of station A34 (approximately three miles downstream from La Belle bridge). The bed consists of nonfossiliferous cream colored sandy clay. Its maximum thickness above low-water level is three feet, but it extends underwater for at least five additional feet. A test hole drilled nearby penetrated Tamiami deposits at a depth of 15 feet beneath the surface.
East of Fort Thompson where the beds of that name and the Caloosahatchee beds dip below low-water level, test holes reveal that both formations thicken considerably. Where they rise again at Ortona Locks the base of the Caloosahatchee formation apparently lies 17 feet beneath the surface and rests on a coarse sand which probably represents the Tamiami formation. East of Ortona Locks, Tamiami beds, if present, are deep beneath the surface. Between Citrus Center and Lake Okeechobee the Caloosahatchee marl has a minimum thickness of 60 to 65 feet and test holes have not penetrated the Tamiami formation.

NATURE OF THE TAMIAMI-CALOOSAHATCHEE CONTACT

The contact between the Caloosahatchee marl and the Tamiami formation is unconformable. The conclusion of Parker and Cooke (1944, p. 61) that the contact between the two formations is transitional is unwarranted and is supported neither by field evidence nor subsurface studies. It is clear that the Tamiami formation was subjected to considerable subaerial erosion and dissection before being inundated by the Caloosahatchee sea. Most of the undulations







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in the beds exposed along the Caloosahatchee River probably reflect irregularities of the Tamiami erosional surface. The Caloosa-. hatchee and younger beds tend to rise in arch-like form over the old buried hills and dip downward over the sites of valleys. Some of the Tamiami hills probably formed low islands in the Caloosahatchee sea, while others rose close enough to the surface to be affected by wave action and to be swept relatively clear of sediments by marine currents. In general, the deeps were areas of greatest deposition, and the Caloosahatchee deposits gradually filled in the old Tamiami valleys. During the latter part of the Caloosahatchee epoch we may infer a rise in sea level which resulted in the deposition of the Bee Branch member and the upper shell bed over most of the sea floor in the upper Caloosahatchee River area.

CALOOSAHATCHEE MARL

GENERAL DISCUSSION

The Caloosahatchee marl is exposed almost continuously in the banks of the Caloosahatchee River between Ft. Denaud and Fort Thompson. The thickness of the exposed beds is generally less than 10 feet, but the base of the formation is visible only in a few places. Test holes have shown that the formation has a thickness of 30 feet or less west of La Belle but reaches a thickness of 50 to 65 feet or more east of La Belle.
The exposed beds have been divided into several stratigraphic units (fig. 7, p. 41). Several beds in the lower part of the section for convenience are classified together as the "lower Caloosahatchee beds." These include the Cyrtopleura costata zone, the basal oyster biostrome, and the brackish-water beds. The lower beds are overlain by the Bee Branch limestone member, and the uppermost unit in the section has been termed the upper shell bed. The section at Ortona Locks is discussed under a separate heading.

LOWER CALOOSAHATCHEE BEDS

General Discussion

At many places along the banks of the Caloosahatchee River the lower Caloosahatchee strata rise above low-water level. However, during periods of high tide or flood stage, most of these beds are submerged. Exposures of the lower beds are most typically developed along a stretch of the river extending between points







LATE NEOGENE STRATA OF SOUTHERN FLORIDA


0.5 mile and 3.5 miles upstream from Ft. Denaud in Hendry County. Here the beds rise higher above the water level than elsewhere, are usually thicker, and are laterally more extensive. The exposed thickness rarely exceeds five feet and commonly is less, although locally it may reach as much as eight feet.
The base of the lower beds can be observed only where the Caloosahatchee marl laps onto the erosional remnants of the Tamiami formation. Throughout most of the upper reaches of the Caloosahatchee River the lower units are overlain conformably by the Bee Branch member. Where erosion has been intense the overlying beds are unconformable and belong either to the Fort Thompson or Pamlico formation. The lower Caloosahatchee beds were nowhere observed to form the top of a section.
Typically the lower beds are light colored, with cream, white, and light gray predominating, although some units are mottled yellow-brown by "limonite" staining and all are some shade of gray on weathered surfaces. At almost all localities the beds are comprised of sandy and silty marls. Locally the percentages of sand-sized particles is high enough to warrant describing the rock as calcareous sandstone. Generally the sand is rather fine-grained (1/8-1/2 mm.), but coarser grains, up to two mm., are present in varying amounts. In the insoluble residues (table 2, p. 52), sand and coarse silt are shown not to comprise more than 62 percent by weight of the sample and may be as low as eight percent (station A30). The carbonate fraction usually exceeds 50 percent but the maximum is 89 percent at station A30 and the minimum figure of 33.5 percent was obtained from a sample at station A23 about a mile downstream from La Belle. Clastics finer than 1/64 mm. were not observed to exceed nine percent by weight and average about four to five percent.
Mineralogically the sand consists almost exclusively of quartz grains. A relatively few grains of phosphorite and white mica (sericite) were observed in some residues. The quartz grains are usually subangular and clear, but most of the larger grains and a small percentage of the smaller grains are well rounded, spherical, and frosted. The residue from each of the beds and facies is similar and the differences are largely related to the average size of the quartz grains, and to the clastic-nonclastic ratio. In some localities the sand residue is either notably coarser or finer than the typical samples, and some samples are considerably more or less calcareous than average.
Small solution holes (one foot or less in diameter) and pockmarks are common and conspicuous. In many areas the holes have








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TABLE 2
INSOLUBLE RESIDUE ANALYSES OF SEVERAL LOWER CALOOSAHATCHEE MARL SAMPLES COLLECTED AT STATIONS
LOCATED BETWEEN ORTONA LOCKS AND FT. DENAUD
(Numbers represent percentage by weight of total sample)
Carbonate
Station Fraction Residue

Greater than Less than
1/64 mm. 1/64 mm.

Cyrtopleura costata
zone
A 16 ----------------------------------------- 54 .0 4 3 .0 3 .0
A17 ----------------------------------------------------- --- 49.5 47.5 3.0
A23 -- - ---------- 51.5 43.5 5.0
A35 - 88.0 7.5 4.5 A36 -- -- 78.0 13.0 1.8
Oyster biostrome
A15 - 76.0 21.5 2.5 A23 -- 46.5 44.5 9.0 A36 --------------------------------45.0 50.0 5.0
Brackish-water marl
A23 ----------------------------- 33.5 60.0 6.5
A36 79.5 11.5 9.0
Undifferentiated lower marls
A4-1 --- 70.5 25.5 4.0 A4-2 35.0 62.0 3.0 A4-3 --- 84.0 10.5 5.5 A 5 - 3 ...................................................... . ..... 7 2 .5 2 3 .0 4 .5
A15 ---- -- 64.0 32.5 3.5
A16-1 - 45.0 52.0 2.5 A16-2 --- - -- - 46.0 50.5 4.0
A17 59.5 34.0 6.5 A23 --------------.-.- ..........------------------------ 56.5 39.0 4.5
A30 - 89.0 8.5 2.5 A34 - 77.5 15.5 7.0 A39 - - 75.0 20.0 5.0







LATE NEOGENE STRATA OF SOUTHERN FLORIDA


been filled with sediment and fossils from overlying beds. This presents a serious problem in stratigraphic collecting and in designating stratigraphic units in the field, but the hazard can generally be avoided if care is taken.
Calcareous concretions of various sizes and shapes are abundant. Many are small irregular fossiliferous nodules that occur in random manner scattered in a bed, whereas some are joined so as to form an arborescent network extending throughout an entire bed. This is especially well shown in bed 2 at station A26 where pockets of soft marl occur between branches of hard calcareous concretions.
Characteristically the marls and sands are soft and relatively unconsolidated. Most may be easily broken when gently pressed between the fingers. Most samples can be disaggregated by soaking in cool water. Some beds are firmly cemented with calcium carbonate, are hard, and tend to form ledges along the banks of the canal. Near Ortona Locks in Hendry County a thin hard calcareous sandstone almost barren of fossils forms a slight ledge at or below the water level.
Many of the beds are fossiliferous. Almost every facies and all units carry an abundant, varied and well preserved fauna. Mollusks are dominant but foraminifers are well represented, and ostracodes, barnacles, and bryozoans are common, at least locally. Corals and echinoids are generally lacking at the localities visited.
Stratigraphic units are discontinuous and variable in appearance. They are difficult to trace even by actually "walking out" the contact. In the field stratigraphic units were differentiated on the basis of the criteria that are listed below in decreasing order of their significance.
1. Faunal composition (key species, dominant forms)
2. Lithology (sandstone, sandy marl, shell marl)
3. Degree of induration and cementation
4. Bedding planes
5. Special features (concretions, phosphate grains, alignment of fossils)
6. Color of sediment and fossils
Several units (zones) and numerous facies are recognized. Two units are fairly persistent and can be used with caution as minor marker beds to which the other beds may be related. The lower of these is the Cyrtopleura costata faunizone and the upper is the basal oyster biostrome.
Cyrtopleura costata Faunizone
This zone, noted by Parker and Cooke (1944) consists of soft sandy calcareous marl, in which are found colonies of the large







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Figure 14
Cyrtopleura costata faunizone near station A31 showing valves of Cyrtopleura costata oriented in their burrows. The deposits of this zone are those
adjacent to the hammer in the lower part of the photograph.
pholadid clam, Cyrtopleura costata Linn. The specimens are oriented in their burrows as in life (fig. 14).
The zone is thin, usually not exceeding 1.5 feet in thickness and in many sections gradational to the beds above and especially to those below. The basal oyster marl overlies it at most localities. In most places the underlying beds are submerged or occur in the subsurface but they can be observed in the most pronounced arches. At station A31 (about 2.25 miles upstream from Ft. Denaud) the underlying unit is a white fine-textured argillaceous fossiliferous marine marl of the Caloosahatchee formation. At station A34 (approximately three miles downstream from La Belle bridge) the zone overlies a nonfossiliferous clay of the Tamiami formation. At A17 (about 1.25 miles upstream from La Belle) the underlying Caloosahatchee unit carries a brackish-water fauna, and at station A15 (near Fort Thompson) the underlying bed is a Caloosahatchee fresh-water marl.
Field studies have definitely established that these beds extend laterally from station A14 (about 2.25 miles upstream from La Belle) to station A39 (about 0.25 mile downstream from Ft. Denaud in Hendry County). It is possible, but not proved, that one







LATE NEOGENE STRATA OF SOUTHERN FLORIDA


of the lower beds exposed near Ortona Locks in Glades County is an extension of this unit. If this is true, then the total lateral distribution of the beds along the river is at least 15 miles.
The zone is typically developed between stations A30 and A38 in Hendry County where several large colonies of Cyrtopleura costata can be observed. Elsewhere only scattered specimens of this pelecypod are found and recognition of the zone must be based on the associated faunal elements or position in the stratigraphic sequence. Several distinct facies differ from the type. These include a Turritella facies near station A23, a shallow-water highsalinity facies, a brackish-water facies, a barren sandy facies (near La Belle), and possibly a facies represented by one of the lower beds at Ortona Locks.
In the vicinity of Ft. Denaud the zone in some places includes distinct upper and lower beds with thin oyster marls overlying each. Cyrtopleura costata was not recorded by the writer from the upper Caloosahatchee beds or from any Fort Thompson bed in southern Florida, despite the fact that it occurs as a Recent species in Floridan waters. The species is characteristically a relatively deep burrower. It is logical, then, to assume that sediments in which specimens of C. costata are naturally oriented in their burrows are not exactly contemporaneous with the fossils but are in part, at least, somewhat older. The time difference represented, nevertheless, is probably slight.
Analysis of insoluble residue of the sediment at station A17 shows that the bed is comprised of 49.5 percent by weight of calcium carbonate and 50.5 percent of clastic material, of which 47.5 percent exceeds 1/64 mm. in diameter. The sand and silt consists almost entirely of quartz grains. The coarser grains are typically rounded and frosted, whereas most of the finer grains are subangular and clear. The analysis of the Turritella facies of station A23 is nearly identical to that of the sediment just described but that of the Vermicularia zone at Ortona is much more calcareous.

Basal Oyster Biostrome

A thin marl overlies the Cyrtopleura costata faunizone and in some places is sharply set off from the bed below, but in others bears a transitional relationship to it. At many localities the biostrome consists almost entirely of large shells of Crassostrea virginica and Ostrea sculpturata, which are oriented as in life (fig. 15, p. 56). Several similar oyster beds can be observed in the








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Figure 15 Caloosahatchee marl at station A27 showing oyster biostrome above a local lens of limestone.







LATE NEOGENE STRATA OF SOUTHERN FLORIDA


outcrop area but only the lower one is laterally extensive. The basal oyster biostrome is separated from the beds above and below almost entirely on the basis of faunal criteria. It generally grades upward to a bed which carries a brackish-water fauna but which typically lacks abundant oysters.
The unit rarely exceeds one foot in thickness and usually is less. In some areas the oyster valves are small and immature and seem to have been somewhat disturbed by wave or current action; typically the valves average seven to nine inches long and are thick and heavy, as can be seen upstream from La Belle in the vicinity of stations A16, A17, and A18. Both Crassostrea virginica and Ostrea sculpturata are present in the area. Associated with the oyster valves and commonly serving as an attachment for the oysters are large valves of Chlamys solarioides. This relationship is also recorded by Olsson and Harbison (1953, p. 49).
The lateral extent of the bed is essentially identical to that of the underlying Cyrtopleura costata faunizone, and can be traced from station A14 for 2.25 miles upstream from La Belle to Ft. Denaud. The bed does not occur in the Ortona Locks area, however. Generally, the oyster biostrome is gradational upward to a sandy marl that bears a brackish-water fauna. Where that bed is missing, the overlying unit is the Bee Branch member. At some places, as at stations A30 and A31, the oyster marl is separated into upper and lower units by an intercalated marine marl that carries an exceedingly well preserved assemblage of larger gastropod species, such as Strombus leidyi and Fasciolaria scalarina. This bed reaches a maximum thickness of 1.5 feet at station A30 (about 200 yards upstream from the old La Belle picnic grounds). The soft marl occupying spaces between the oyster valves is generally cream or gray in color when fresh, but weathers to a dark drabgray.
At station A23 the insoluble residue is 53.5 percent by weight and the coarse fraction comprises 83.1 percent of the residue. The sand consists of fine to medium-sized quartz grains with only a few grains that exceed one mm. in diameter. The larger grains are subrounded and frosted as in the beds below but the finer grains are mostly subangular and clear.
The insoluble residues of the overlying brackish-water bed are very similar to those of the beds just described but at station A35 the soluble fraction constitutes 88 percent by weight and a sample of the conch-bearing bed at station A30 possesses 89 percent by weight of calcium carbonate and the clastic fraction is very fine grained.







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Fresh-Water Marls

Beds of fresh-water origin apparently never before have been recorded from the Caloosahatchee formation. According to Schroeder and Klein (1954, p. 5), ". . . fresh-water beds have not been reported in the Pliocene of the Atlantic Coastal Plain and do not occur in the Caloosahatchee marl (Pliocene) in the outcrop area, although fresh-water shells are found, in places, mixed with the marine forms." In subsurface correlation in southeastern Florida Hoy and Schroeder (1952, p. 283-285) consider the presence of fresh-water limestones good evidence of the Pleistocene age of beds penetrated by the drill.
Fresh-water mollusks are abundant in many of the lower Caloosahatchee beds and locally comprise over 95 percent of all specimens present. These beds are almost certainly of freshwater origin. One such unit was observed in the lower Caloosahatchee beds, just below the Cyrtopleura costata faunizone at station A15, the type locality of the Fort Thompson formation. At the time the writer visited the area this bed formed a slightly submerged ledge of hard dense gray calcareous marl about 10 inches thick. It is very fossiliferous and includes mostly small freshwater snails such as "Fontigens" and several species of the land snail, Polygyra, including P. sayi peninsulae Pilsbry; P. septemvolva Say, and P. septemvolva volvaxis (Pfeiffer). This bed seems to grade laterally into one bearing a brackish-water fauna at stations A16 and A17.
The insoluble residue is 37 percent by weight. The sand consists of fine to medium grains of quarts which are strikingly similar to those occurring in most other lower Caloosahatchee beds.
It seems perfectly logical to postulate the occurrence of additional fresh-water beds of Caloosahatchee age in the outcrop area or at least in subsurface. Such beds cannot arbitrarily be considered to belong to the Fort Thompson formation although they are Pleistocene in age.
BEE BRANCH MEMBER
The name Bee Branch member is here proposed to designate a relatively hard solution-riddled marine limestone or marl unit of the Caloosahatchee marl. It is typically exposed along the Caloosahatchee River in Hendry County near its confluence with the tributary called Bee Branch.
With one or two exceptions it conformably overlies the lower Caloosahatchee beds described above, and is in turn conformably







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overlain by the upper Caloosahatchee shell beds. Wherever erosion has been considerable, the overlying beds may belong either to the Fort Thompson or the Pamlico formation and the contact is unconformable.
This bed has been definitely traced along the river from station A13 in Glades County to a point in Hendry County about two miles downstream from Ft. Denaud. It has been identified on several tributary drainage canals within the area, including a canal near Clewiston, and from spoil piles along the river between station A13 and Old Lock No. 3. It may be represented at Ortona Locks by the lower limestone unit and possibly can be extended to Shell Creek in Charlotte County. It is the most important marker bed exposed along the river.
The thickness of this unit ranges from a maximum of about five feet to a minimum of a few inches, but the average is probably close to 2.5 feet. In the vicinity of the type locality between stations A22 and A26 the thickness is two to four feet.
Two principal facies of the Bee Branch member and many minor variations of each have been recognized. One facies is represented by the Bee Branch deposits of the type locality which form a massive, hard calcareous bed (fig. 16, p. 59). It forms a





















Figure 16
Specimen of the Bee Branch limestone from the type locality. The rock
belongs to the hard massive facies of the member.







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nearly vertical wall on both sides of the stream, juts out over the softer beds below, and above the bed forms a distinct ledge, in places several feet wide. It is riddled with large and small solution holes that are filled with matrix from overlying beds. Commonly small pockets of softer marly material occur within the bed but are not related to solution holes above. The exposed vertical surfaces are pockmarked where these small patches of marl have been flushed out at flood stage. Most of the weathered surfaces are dark gray or black, but fresh surfaces are buff or cream colored. Yellow-brown mottling by limonite stain is common.
The insoluble residue (table 3, p. 60) of a sample from the type locality is 9.0 percent by weight. The coarse clastic fraction consisted of fine to medium quartz sand. The coarser grains are rounded and frosted, whereas most grains less than one mm. in diameter are subangular and clear. The sand and silt are nearly identical with that of the lower beds.
The other dominant facies differs from that of the type locality in being much softer, less consolidated, more arenaceous, and more distinctly concretionary. Generally it does not form prominent ledges. The concretions contained in it are hard, dense calcareous nodules which locally occur in isolated manner but more commonly form an arborescent network extending throughout the entire bed.
TABLE 3
INSOLUBLE RESIDUE ANALYSES OF SEVERAL BEE BRANCH ROCK
SAMPLES COLLECTED AT STATIONS LOCATED BETWEEN
ORTONA LOCKS AND FT. DENAUD
(Numbers represent percentage by weight of total sample)

Carbonate
Station Fraction Residue
Greater than Less than
1/64 mm. 1/64 mm.

A5 (Ortona Locks) - 60.5 35.0 4.5 A15 (Fort Thompson) 79.5 18.5 2.0 A16 (Typical marly facies) ---------------- 59.0 38.5 2.5
A70 (Type locality) 91.0 5.5 3.5 A 2 6 ..... . ... . . ......... ....... . ..................... ..- - 8 5 .0 1 1 .0 4 .0
A 3 3 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .-9 3 . 0 4 . 5 2 . 5
A 3 4 ------------------------------------------------------------ 9 1 .5 6 .5 3 .0
A 3 5 ------------------------------------------------------------ 8 5 .0 1 0 .0 5 .0
A36 -73.5 15.5 11.0 A39 (1 mile west of Ft. Denaud) ------ 82.0 15.0 3.0







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The insoluble residue at station A16, near Fort Thompson, is 41 percent by weight (table 3, p. 60), of which approximately 94 percent possesses a diameter greater than 1,/64 mm. The sand consists of fine to medium, subangular to rounded quartz grains which differ from those described from the type locality in being slightly more coarse.
At stations A13 and A14 the Bee Branch member is represented by a thin hard layer of limestone. This bed is fluted by solution channelways that give it a peculiar lineated appearance. Over the La Belle clay arch, the member is represented by a sandy concretionary facies, but downstream from Ft. Denaud the bed becomes argillaceous. At Ortona Locks the member has not been positively recognized. The lowest marine limestone at Ortona Locks seems to occupy the same stratigraphic position as the Bee Branch member but neither it nor the beds beneath it seem to be similar to those found downstream. The insoluble residue of a sample of this bed is 39.5 percent by weight. The sand fraction is generally more coarse than at the type locality, but otherwise it seems nearly identical.
The fauna of the Bee Branch member is distinctive. The two principal facies carry a large echinoid fauna, which includes several species of regular forms as well as cassiduloids and numerous well preserved specimens of Clypeaster rosaceus. Among the most typical mollusk species are Chlamys nodosus, Amusium mortoni, and Mulinia caloosaensis. All three species are rarely found in any other Caloosahatchee bed. Varicorbula caloosae is abundant but not restricted stratigraphically. The fauna of the marly facies contains the typical forms but otherwise more nearly approaches that of the beds above.

UPPER CALOOSAHATCHEE SHELL BED

At many places between La Belle and Ft. Denaud an interesting shell bed overlies the Bee Branch member conformably (fig. 17, p. 62). That bed is interpreted to constitute the uppermost unit of the Caloosahatchee formation in the area; the molluscan assemblage shows it to be of Caloosahatchee age. Neither this bed nor correlative units have been recognized certainly upstream from Fort Thompson, although one or more of the upper beds at Ortona may represent a facies of the unit. The upper shell bed on Shell Creek possibly is an extension of the unit. Downstream from Ft. Denaud the bed was not observed by the writer.








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Figure 17
Upper Caloosahatchee shell bed at station A35, one mile upstream from Ft. Denaud. A large bone of a terrestrial vertebrate can be seen near the lower end of the hammer.
At several localities an oyster bed and one or more thin, freshwater limestones lie near the top of the shell bed. At a few places the uppermost fresh-water limestone is overlain by a marine marl that contains a typical Fort Thompson molluscan assemblage.
The best exposures of the shell bed occur along the Caloosahatchee River in Hendry County between stations A26 and A35, and this is considered to be the type locality. The bed is discontinuous, being absent or greatly thinned over the arches. It reaches greatest thickness in the troughs of undulations of the underlying beds. In one of these troughs, at station A28 (about 2.5 miles upstream from Ft. Denaud) the bed is 8.5 feet thick, and near station A35 (about 1.5 miles downstream) it reaches 10 feet in thickness. Most of the better exposures are two to four feet in thickness. Erosion concentrated on the arches seems to be mainly responsible for these differences in thickness and it probably accounts for the absence of this unit upstream from La Belle, although it is possible that deposition over the arches may not have been as great as in the troughs.
At many localities the bed is very arenaceous and the calcium carbonate content is mainly in the form of mollusk shells. Thick







LATE NEOGENE STRATA OF SOUTHERN FLORIDA


Figure 18
Specimen of upper Caloosahatchee shell bed from station A34, approximately
2.0 miles upstream from Ft. Denaud.

beds are generally only slightly consolidated and are easily eroded. The sands are usually tan to yellow-brown, but the fossils are nearly white. At some localities the unit is better consolidated, much more calcareous, concretionary, and finer grained (fig. 18, p. 63). The color is usually light to buff, but weathers dark gray. Both facies are massive, and generally without stratification.
An insoluble residue analysis of a sample from station A28 shows a coarse clastic residue greater than 1/64 mm. of 30 percent by weight and a fine clastic residue of less than 1/64 mm. of 5.5 percent (table 4, p. 64). Upstream at station A23 (about 1.5 miles downstream from La Belle) the coarse fraction constitutes only 7.0 percent of the total weight, and the fine fraction makes up 8.0 percent. Downstream, at station A35, the coarse fraction is 39 percent and the fine fraction 5.5 percent of the total weight. The sand itself does not seem to differ appreciably from that of the lower beds. It consists mostly of fine to medium-grained, subangular to moderately well-rounded quartz grains. The larger grains are frosted and most of the finer ones are clear.
At all localities the member is fossiliferous. The faunal remains







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TABLE 4
INSOLUBLE RESIDUE ANALYSES OF SEVERAL UPPER CALOOSAHATCHEE SHELL BED ROCK SAMPLES COLLECTED AT
STATIONS BETWEEN FORT THOMPSON AND FT. DENAUD
(Numbers represent percentage by weight of total sample)

Carbonate
Station Fraction Residue
Greater than Less than
1/64 mm. 1/64 mm.
A17 31.5 65.5 3.0 A23 85.0 7.0 8.0 A28 ----------------------- 64.5 30.0 5.5
A35 ------------------- 42.0 56.0 2.0
A36 (lower) - 77.0 11.0 12.0 A36 (upper) 65.5 22.0 12.5

consist mostly of mollusk shells but corals, foraminifers, ostracodes, barnacles, and bryozoans are common. This appears to be the only bed along the river that contains a large coral fauna. Chione cancellata (Linn6) is the dominant marine species at nearly all localities, reaching its climax in individual size and relative abundance in the upper Caloosahatchee. The megafossils are well preserved but show random orientation suggesting moderate reworking by wave action subsequent to death.
In the vicinity of stations A34, A35, and A36, Hendry County, the member contains a sparse vertebrate fauna which includes teeth of Equus Equus cf. E. (Equus) leidyi, a Pleistocene horse.
Fresh-water mollusks are less abundant than in the lower Caloosahatchee beds but locally thin beds occur near the top of the section and appear to be of fresh-water origin; other beds clearly represent a brackish-water environment.
No good reason is apparent for regarding the fauna of this member as transitional between that of the lower Caloosahatchee beds, and the later Fort Thompson fauna. It is definitely more closely related to the Caloosahatchee faunas below than to the faunas of overlying deposits.
FORT THOMPSON FORMATION
GENERAL DISCUSSION
The Fort Thompson formation is represented along the Caloosahatchee River by a thin succession of alternating fresh-water and marine marls that bear an unconformable relationship to the







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Figure 19


Exposure of the Fort Thompson formation near the type locality. The hammer is resting against the lower fresh-water marl. The overlying beds include the Chlamys bed, upper fresh-water marl, Coffee Mill Hammock marl, the
Pamlico quartz sands, and the Lake Flirt marl.

underlying Caloosahatchee marl. Downstream from Ft. Denaud, where the Caloosahatchee formation is absent, the Fort Thompson beds rest on the Tamiami formation. The overlying beds also are unconformable on the Fort Thompson formation and belong either to the Pamlico formation or to the Lake Flirt marl. The thickest and most continuous deposits lie along the Caloosahatchee River between La Belle and Ortona Locks (fig. 19, p. 65) where these deposits reach a maximum thickness of approximately eight feet, with several fresh-water and marine members well developed. Downstream from La Belle the Fort Thompson formation is usually a foot or less in thickness; however, at many localities the formation has been entirely removed by erosion.
Discussion of the Fort Thompson formation has been divided into sections devoted respectively to fresh-water and marine deposits. The marine sediments are subdivided into the Chlamys bed and Coffee Mill Hammock marl. The fresh-water deposits are interbedded with the marine sediments.







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FRESH-WATER DEPOSITS

Several thin, laterally discontinuous beds of fresh-water origin have been recognized in the Fort Thompson formation. Dall (1892, p. 143) considered those beneath the Coffee Mill Hammock marl to be Pliocene in age, but Sellards (1919a, p. 71-73) apparently correctly regarded them as Pleistocene.
Generally the beds are light cream colored to buff or tan marls, which are only slightly or moderately consolidated. At several localities the marls are relatively well indurated, or even may be casehardened. A few limestone beds occur in the outcrop area and some of these are cherty. Nearly all are somewhat sandy, as shown by insoluble residue analysis.
Most strata are fossiliferous and the fossils are characteristically well preserved. A majority of the forms are fresh-water gastropods but some terrestrial snails are found and locally, marine shells reworked from underlying beds may be included with the others. The most characteristic species is Helisoma scalare (Jay), which occurs in great numbers in some beds.
A relatively persistent stratum of fresh-water marl extends upstream from station A21 (about 0.75 mile east of La Belle bridge) to a point just beyond station A10, a distance along the river of approximately 2.7 miles. Typically this bed lies unconformably on the Bee Branch member of the Caloosahatchee formation but locally it rests on the upper Caloosahatchee shell bed (near station A17).
At the Fort Thompson type locality and elsewhere between stations A17 and A10 the fresh-water marl is divided into upper and lower units by a thin tongue of a marine shell marl (Chlamys bed). Thus, an intertonguing relationship appears to exist between marine and nonmarine beds developed along a fluctuating shoreline. This relationship is diagrammatically shown below (fig. 20, p. 67).
The lowermost subdivision of the fresh-water marl, which typically overlies the Caloosahatchee formation, averages about two feet in thickness, while the upper subdivision is about 1.5 feet thick. Where the two coalesce their combined thickness rarely exceeds two feet.
All phases of the fresh-water marl disappear a short distance downstream from the point (station Al) where the La Belle clay first rises above the water level. The fresh-water marl pinches out between layers of marine marl at station A17 but reappears as isolated small patches or lenses between this locality and station A21. Downstream from station A21 no fresh-water marls were






LEGEND
LAKE FLIRT MARL FORT THOMPSON FORMATION CALOOSAHATOHEE MARL (D
COFFEE MILL HAMMOCK MARL UPPER SHELL BED S.FRESH-WATER SANDY MARL BEE BRANCH LIMESTONE
PAMLI-WATO LIMESATONNE
PAMLICO FORMATION FRESH-WATER MARL OYSTER BIOSTROME


111QUARTZ SAND m CHLAMYS BED /CCYRTOPLEURA COSTATA ZONE
12 -g 1.5 MILES ' W E o o11
z

1o 0

9

0


o 7







u0, 3

2





A19 AI8 A17 A16 A15 A14 STATIONS








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observed in the banks of the Caloosahatchee River. At a road metal pit along State Highway 80 a few yards west of its intersection with the old La Belle road, large pieces of a nonmarine marl were collected from spoil piles. The nonmarine bed underlies the Coffee Mill Hammock marl and probably represents an extension of the upper fresh-water stratum.
A section exposed about 125 yards upstream along Banana Creek, sec. 21, T. 43 S., R. 28 E., Hendry County, includes a well developed fresh-water marl (fig. 21, p. 69). At this place the freshwater marl is divided into upper and lower parts by a thin layer of marine marl which contains a fauna almost identical with that of the Chlamys bed exposed in the vicinity of Fort Thompson.
Near station A14 the upper and lower beds of nonmarine marl are exceptionally well developed and this area should be considered their type locality. In this area the lower stratum is two feet thick and is capped by a casehardened undulatory surface upon which the Chlamys bed is developed. The insoluble residue of a sample from the lower part of this fresh-water bed is 32.5 percent by weight. The coarse fraction constitutes 84.6 percent of the residue. The sand consists almost entirely of fine to medium-sized, subangular to well rounded quartz grains, which are surprisingly similar to most of the sand in marine beds of the Caloosahatchee formation.
At this same locality (station A14) the upper bed is also approximately two feet thick and its surface is casehardened. No difference in the physical appearance or mineral composition between the sand of the upper and lower beds is apparent. The insoluble residue of a sample is also 32.5 percent by weight and the coarse fraction constitutes 27.0 percent of the total weight, or 80.3 percent of the residue.
At several localities between La Belle and Ortona Locks and in a few places between La Belle and Alva, a thin nonmarine limestone lies immediately under the Coffee Mill Hammock marl. Laterally it is discontinuous, and near Fort Thompson the bed is riddled by small solution holes that have become filled with sediment from overlying beds. At Fort Thompson this bed reaches a maximum thickness of approximately two feet. Here the unit is a gray sandy limestone with only a few fossil remains.
Upstream from station A10 the fresh-water beds dip beneath water level. Where the Fort Thompson formation again rises high above water level about 0.3 mile downstream from the Atlantic Coast Line bridge, only one fresh-water bed is present in the section.








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Figure 21
Exposure of Fort Thompson and Pamlico deposits along Banana Creek. The white sand bed is the basal unit of the Pamlico formation and the hammer is imbedded in the upper fresh-water marl of the Fort Thompson formation.








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MARINE DEPOSITS

General Statement

Most of the Fort Thompson marine beds may be classified as poorly consolidated tan or cream-colored sandy shell marl. Chione cancellata Linn6 is the most characteristic fossil of these beds. It occurs in great profusion and generally comprises 23 to 38 percent of the total pelecypod fauna.
At and near the type locality two marine shell beds are exposed (fig. 20, p. 67). They alternate vertically with beds of freshwater origin. This relationship has been discussed at length by Parker and Cooke (1944, p. 73-74, 87, 94-96). The uppermost bed is the Coffee Mill Hammock marl and the lower unit comprises the so-called "Chlamys bed."
Downstream from La Belle the alternating relationship is not well developed and at many places all traces of the Fort Thompson formation have been removed by erosion.
There seems to be no good reason for assigning any marine shell bed exposed along the river to the Anastasia formation.
Chlamys Bed
Between stations A13 and A17 in Hendry County and along Banana Creek in Glades County, the fresh-water marl is divided into upper and lower units by a four to eight-inch thick marine shell bed. Because it is characterized by numerous valves of Chlamys gibbus irradians, it has been designated as the Chlamys bed. The unit is sharply separated from the undulatory casehardened surface of the fresh-water unit below, and it grades into the nonmarine bed above.
The matrix is buff or cream on the fresh surfaces but generally weathers gray. It is a poorly consolidated mixture of sand and mollusk shells. The insoluble residue of a sample is 46.0 percent by weight. The coarse fraction of the residue comprises 87.0 percent of the total. The sand consists of subangular to subrounded quartz grains much as in the Coffee Mill Hammock marl.
The Chlamys bed was noted by Parker and Cooke (1944, p. 90) at Fort Thompson and was correlated by them with the Yarmouthian interglacial stage. It is judged by the writer to represent a minor sea level fluctuation of short duration which occurred during the same interglacial period in which the other Fort Thompson beds were deposited.
In addition to Chlamys gibbus irradians, the species Helisoma scalare, Cerithium muscarum, Anomalocardia caloosana,







LATE NEOGENE STRATA OF SOUTHERN FLORIDA


Laevicardium mortoni, and Transennella cf. T. conradina are common to abundant. The fauna of the Chlamys bed exposed along Banana Creek closely resembles that near Fort Thompson. This similarity is shown in table 8, p. 124, which lists the percentages of the most common species at each station.
At the mouth of Banana Creek, where it enters the Caloosahatchee River, there is only a trace of a fresh-water marl and the Chlamys bed is not present. Between Banana Creek and the Fort Thompson area the Chlamys bed was not observed to be exposed along the banks of the Caloosahatchee River. Judging from the Banana Creek section, however, it is possible that a few yards from the banks of the Caloosahatchee River the bed extends, in subsurface, over a relatively wide area.

Coffee Mill Hammock Marl

The uppermost marine marl, that is the thickest and most extensive in the area, was named by Sellards (1919a, p. 73) from exposures near Coffee Mill Hammock, located on an abandoned meander north of the Caloosahatchee canal about 0.25 mile west of the Atlantic Coast Line bridge at Ortona Locks.
At the type locality and at most other river localities the Coffee Mill Hammock marl conformably overlies a fresh-water marl or limestone and is, in turn, overlain unconformably by sands of the Pamlico formation or by Lake Flirt marls. The marl is three to six feet thick at the type locality; in some other areas it does not form an actual bed but is preserved only as fillings in solution holes and pockets in the limestone below.
The member is typically light colored and consists of cream to white mollusk shells imbedded in a loosely indurated tan to light gray sand (fig. 22, p. 72). At the type locality the insoluble residue of a sample is 79.5 percent by weight, of which about 97 percent is included in the coarse fraction. The sand is composed primarily of fine to medium-sized, subangular to rounded quartz grains. Most of the grains are subangular and clear. Only a small percentage of grains, mostly the larger ones, are well rounded and frosted. The sand appears to be almost identical with the sands of the Caloosahatchee formation and most other beds in the area. At station A14, where the unit is only about 2.5 feet thick and has been subjected to some erosion, the residue of a sample was determined to be 58.0 percent by weight. The coarse fraction comprises 90.4 percent of the total weight of the residue. The sand is essentially identical to that of the type locality. In all samples








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Figure 22
The Coffee Mill Hammock marl exposed near Fort Thompson. The hammer rests on the Bee Branch limestone.







LATE NEOGENE STRATA OF SOUTHERN FLORIDA


studied the calcium carbonate fraction is derived mainly from included shells.
The fauna of the Coffee Mill Hammock marl is abundant, well preserved, and distinct from any Caloosahatchee fauna studied. The most common and typical forms at the type locality are Chione cancellata, Transennella conradina, Bulla occidentalis, and Olivella mutica. Collectively these four species were represented by 5,795 individuals in a 0.75 cubic foot sample.
The Coffee Mill Hammock marl has been recognized by the writer and other workers at many localities along the river between Ortona Locks and Ft. Denaud. Also, it has been observed along many canals and tributaries of the river and in pits and ditches in the area between Moore Haven and Olga. Undoubtedly it is to be found in the subsurface throughout much of Lee, Hendry, Charlotte, and Glades counties. Similar, if not identical, beds extend along the west coast of Florida at least from Naples, in Collier County, to St. Petersburg, in Pinellas County, but comparable shell beds exposed along Joe's Creek in St. Petersburg are considered by Winters3 to be Pamlico or possible Silver Bluff in age.

PAMLICO FORMATION
Sands of the Pamlico formation were observed at nearly all Caloosahatchee River localities. In the area adjoining the Caloosahatchee River, Shell Creek, and Alligator Creek, the Pamlico f ormation forms an almost continuous blanket of sand at elevations less than 25 feet above sea level. Generally the Pamlico sand rests unconformably on a member of the Fort Thompson, Caloosahatchee, or Tamiami formation. Between La Belle and Ortona Locks it usually overlies the Coffee Mill Hammock marl and may be overlain in turn by the Lake Flirt marl, or lie exposed at the surface. Downstream from La Belle as far as Ft. Denaud the sands in many places rest directly on the Caloosahatchee formation. At stations A23, A31, and A35, the Pamlico formation lies on the upper Caloosahatchee shell bed. At station A22 a one-foot layer of Pamlico sand lies unconformably on the Bee Branch member. At some localities it overlies the Coffee Mill Hammock marl. Downstream from Ft. Denaud the Pamlico sand generally lies on Fort Thompson beds, but where erosion has been deep enough it may be observed resting unconformably on the Tamiami formation.
Typically the Pamlico formation is represented by unconsolidated sands of nearly pure quartz. The grains are fine to medium
3Personal communication, 1956.







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in size and subangular to subrounded. Variation in color from place to place and bed to bed is usually due to organic stain on the quartz grains. The color is commonly gray, tan, or buff. No invertebrate fossils were observed in Pamlico exposures but at several places remains of terrestrial vertebrates have been found by the writer.

LAKE FLIRT MARL

The name Lake Flirt marl was first used by Sellards (1919a, p. 73) to designate fresh-water sediment deposited in Lake Flirt, which formerly existed east of La Belle in Glades County. The lake has been drained by the Caloosahatchee canal. Deposits similar to those of the type locality are found in many shallow depressions throughout the Everglades.
Along the Caloosahatchee River the bed is best developed between stations A14 and A57 but is found in patches at least several miles east of Ortona Locks. The formation nowhere was observed to exceed five feet in thickness and is usually less.
Typically it overlies the Pamlico formation unconformably but reworking of the sediments at many localities makes separation of the two formations difficult. Beds containing abundant freshwater mollusks were definitely assigned to the Lake Flirt marl.
The formation is typically sandy but differs from the Pamlico in the high percentage of organic matter. In places it is best described as a black muck.

STRATIGRAPHY OF THE ORTONA LOCKS AREA

GENERAL OBSERVATIONS

In the vicinity of the Coffee Mill Hammock a few hundred feet downstream from the Atlantic Coast Line bridge, beds of the Caloosahatchee marl and Fort Thompson formation rise above lowwater level and are well exposed from there to the base of the locks. A generalized stratigraphic section of the Ortona Locks area and correlation of the strata with those of the Fort ThompsonFt. Denaud area are shown below (fig. 23, p. 75). The numbers of the units in the Ortona Locks section are used for reference in the subsequent discussion. The stratigraphic sequence near Ortona Locks is strikingly unlike that anywhere downstream, for the basal Caloosahatchee oyster biostrome is absent and the Cyrtopleura costata faunizone cannot be recognized certainly. Two







LATE NEOGENE STRATA OF SOUTHERN FLORIDA


Figure 23
Correlation of strata exposed in the Ortona Locks area.
marine limestones are included in the section and neither can be definitely correlated with the Bee Branch member.
The lowermost beds in the section are of undoubted Caloosahatchee age, and the uppermost beds definitely belong to the Fort Thompson and Pamlico formations. The intermediate beds were placed in the Fort Thompson formation by Parker and Cooke (1944, p. 93) but apparently they were in doubt about classification of the lower limestone because they included it in the Caloosahatchee marl at station 341 and in the Fort Thompson formation at station 343.
Several molluscan species occur commonly in the Ortona Locks area that are rare or not recorded from the beds downstream. A few of those species range through the Ortona sequence from the lowest Caloosahatchee bed to the fresh-water marl at the base of the Coffee Mill Hammock marl. A list of these species is given below. The numbers correspond to those used in the generalized







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section (fig. 23, p. 75) and denote that the species was recorded from the bed indicated.

Characteristic Species of the Caloosahatchee Formation at Ortona Locks
Pelecypoda

Species Units
Glycymeris americana 1, 2, 6, 8
Plicatula cf. P. marginata 1, 3, 8 Chama gardnerae 1, 3, 8
Chione latilirata athleta 1, 3, 6, 8 Venus campechiensis 1, 3, 6, 8 Eucrassatella gibbesii 3, 4, 6, 8
Juliacorbula scutata 3, 8 Gastropoda
Vermicularia recta 1, 3, 6, 8

The fresh-water marl is regarded as the basal Fort Thompson unit in the area. The fresh-water marl appears to unconformably overlie the beds below (units 7 and 8), and there is a great difference in the composition of the marine molluscan assemblages below as compared with that above (unit 9) the contact. In addition, the fauna of the Panope zone (unit 8) seems to represent the end member of a transitional series beginning with a basal bed (unit 1) which bears a typical Caloosahatchee molluscan fauna. The entire Caloosahatchee series at Ortona Locks apparently developed on the continental shelf, whereas the Coffee Mill Hammock marl probably was deposited either in an inlet or a bay.

CALOOSAHATCHEE MARL

LOWER BEDS (UNITS 1, 2,3,4)

The lower beds in the Ortona Locks area definitely belong to the Caloosahatchee marl. There are four distinct units with a combined thickness ranging from three to six feet. Three of the beds are light colored soft marine marls similar to the beds of the Cyrtopleura costata faunizone downstream. The second bed (in upward sequence from the base) is a thin solution-riddled tan calcareous sandstone which contains a few poorly preserved marine and fresh-water mollusks. The insoluble residue of a sample from this bed is 65.0 percent by weight of which 95.3 percent is included in the coarse fraction. The quartz grains of the sandstone are more frosted and rounded than in any of the associated marls. The insoluble residue data for all the lower beds are shown in table 2.







LATE NEOGENE STRATA OF SOUTHERN FLORIDA


The marine marl (fig. 24, p. 77) which overlies the sandstone was designated the Vermicularia faunizone by Parker and Cooke (1944, p. 93) because of its content of large colonies of this gastropod, now known as V. recta Olsson and Harbison. The concentration of Vermicularia shells in the bed is not uniform throughout the area, however. In the vicinity of the Atlantic Coast Line bridge the shells are small and scattered, but nearer to the locks this species forms dense colonies of large specimens which during life became twisted about one another (fig. 25, p. 78; fig. 26, p. 79). The colonies are two or more feet in height and extend upward through the overlying marl (unit 4, fig. 27, p. 79) and at least into the lower part of the overlying limestone (unit 5). The fauna associated with the Vermicularia colonies includes such characteristic Caloosahatchee species as Arca wagneriana, Bothro-, corbula willcoxiana, Phacoides disciformis, Cerithium caloosaense, Hanetia mengeana, and Mitra heilprini.
Although the lower Caloosahatchee beds differ in detail from any that crop out downstream, judging from their position in the sequence, they probably represent a continental shelf facies of


Figure 24
Lower Caloosahatchee beds exposed near Ortona Locks. The handle of the hammer is leaning against the Vermicularia faunizone. The overlying massive bed is the Bee Branch limestone.








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Figure 25
A specimen composed of the twisted shells of Vermicularia recta from the
Vermicularia faunizone near Ortona Locks.








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Figure 26
Sample of marl from the Vermicularia faunizone near Ortona Locks.


Figure 27 Specimen of marine marl (unit 4) from above Vermicularia faunizone near Ortona Locks.







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the lower Caloosahatchee oyster biostrome, Cyrtopleura costata faunizone, and brackish-water units of downstream stations.

LOWER LIMESTONE BED (UNIT 5)

The lower Caloosahatchee beds are overlain by a hard thin dense light gray to tan marine limestone (fig. 28, p. 81). It ranges in thickness from one to two feet or more and contains many small solution holes filled with marls from the overlying beds. The limestone is moderately fossiliferous but with the exception of Anadara rustica only long-ranging species like Chione cancellata could be identified. The insoluble residue of a sample of this rock is 38.5 percent by weight, of which 91.0 percent is contained in coarse fraction (greater than 1/64 mm.). The sand consists of subrounded fine to medium quartz grains. The bed is very persistent in the Ortona Locks area and offers a major obstacle to the drilling of deep water wells.
If it is assumed that the lower four beds represent a lateral extension of the lower Caloosahatchee units of downstream stations, then it would seem from its position in the sequence that the lower Ortona limestone represents a facies of the Bee Branch member.

MIDDLE SHELL MARL (UNIT 6)

A thin discontinuous cream to tan, moderately consolidated sandy marine marl overlies the lower limestone throughout much of the area (fig. 28, p. 81). The bed is fossiliferous and contains characteristic Caloosahatchee mollusks, including Arca wagneriana, Anadara rustica, Phacoides disciformis, Scaphella floridana, and Pyrazus scalatus. If the underlying limestone is a facies of the Bee Branch member, then this bed represents a facies of the upper Caloosahatchee shell bed of downstream stations.

UPPER LIMESTONE (UNIT 7)
Overlying the middle Caloosahatchee shell marl (unit 6) is a thin gray to tan sandy marine limestone (unit 5) which resembles the lower Caloosahatchee limestone (fig. 28, p. 81). It is relatively nonfossiliferous although it contains some fresh-water species such as Helisoma scalare, and such nondiagnostic marine species as Anomia simplex, Brachidontes exustus, Chione cancellata, and Crassostrea virginica.
The insoluble residue of a rock sample is 16.5 percent by weight, of which 72.5 percent is contained in the coarse fraction







LATE NEOGENE STRATA OF SOUTHERN FLORIDA


Figure 28
Upper Caloosahatchee beds exposed near Ortona Locks. Solution holes in the upper limestone (unit 7) are filled with marl from the overlying Panope faunizone (unit 8). Unit 6 is a soft marine marl and it is underlain by the Bee Branch limestone (unit 5).
(greater than 1/64 mm.). The sand fraction consists of fine to medium subrounded quartz grains similar to that of the lower limestone (unit 5).
Because the upper limestone and all overlying beds lack diagnostic Caloosahatchee fossils, the limestone might be considered to belong at the base of the Fort Thompson formation. However, no evidence of an unconformity between the limestone (unit 7) and the underlying marl (unit 6) is seen. In addition, the fauna of the overlying Panope faunizone contains some of the same peculiar species found in all the underlying marls and differs from the fauna of the Coffee Mill Hammock marl or any other bed that the writer assigned to the Fort Thompson formation. The limestone and rocks of the Panope faunizone form the upper part of a single formation and probably are genetically related to the underlying beds.
PANOPE FAUNIZONE (UNIT 8)
Parker and Cooke (1944) applied the name Panope faunizone to a discontinuous marine shell marl that overlies the upper limestone (unit 7) and fills solution holes in the limestone. The







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Panope faunizone was so named because of the abundance of large specimens of Panope floridana Heilprin that occur oriented as in life in the bed.
In some characteristics the fauna of the Panope faunizone seems to be more closely related to the typical Caloosahatchee assemblages than the fauna of the Coffee Mill Hammock marl. It is true that none of the diagnostic Caloosahatchee species is present in the Panope faunizone, but many species common in the typical Caloosahatchee beds are equally common in the Panope faunizone.
Some of the common fossils of this bed that are also common or characteristic in the typical Caloosahatchee are listed below:

Pelecypoda
Anadara lienosa (Say)
Anadara campyla (Dall)
Glycymeris arata floridana Olsson and Harbison
Ostrea cf. 0. sculpturata Conrad
Chlamys fuscopurpureus (Conrad)
Chlamys anteamplicostatus (Mansfield)
Plicatula cf. P. marginata Say
Chama gardnerae Olsson and Harbison
Echinochama cornuta Conrad
Phacoides multilineatus (Tuomey and Holmes)
Phacoides waccamawensis Dall
Phacoides nassula caloosana Dall Anomalocardia caloosana (Dall) Caryocorbula leonensis Mansfield
Juliacorbula scutata Gardner
Panope floridana Heilprin
Gastropoda
Melongena corona Gmelin (Caloosahatchee variety)
Fasciolaria apicina Dall

The disappearance of some of the more characteristic Caloosahatchee species, especially gastropods, may reflect a gradual cooling of the climate as another glacial stage began.

FORT THOMPSON FORMATION
FRESH-WATER MARL (UNIT 9)

The Panope faunizone is apparently unconformably overlain by a thin hard fresh-water marl. Where the Panope faunizone is absent, the fresh-water marl rests directly on the upper marine limestone (unit 7). This marl underlies the Coffee Mill Hammock marl and probably represents a facies of the fresh-water limestone or marl at Fort Thompson.
The insoluble residue of a sample is 9.5 percent by weight, of which 55.5 percent is included in the coarse fraction (coarser than 1/64 mm.).







LATE NEOGENE STRATA OF SOUTHERN FLORIDA


COFFEE MILL HAMMOCK MARL (UNIT 10)

The Coffee Mill Hammock marl is present throughout most of the area. This member of the Fort Thompson formation is discussed in detail above.


SUBSURFACE STRATIGRAPHY ALONG THE
CALOOSAHATCHEE RIVER

GENERAL OBSERVATIONS
A series of 18 auger holes were drilled along the Caloosahatchee River between Olga in Lee County and Lake Hicpochee in Glades County. Twelve of the holes penetrated 50 to 75 feet beneath the surface, but the remaining six had to be abandoned within a few feet of the surface where the auger encountered hard limestone. The diameter of the holes was four inches. Samples were taken at five-foot intervals, so that mixing of the beds within these intervals was inevitable. In addition, some cave-ins also resulted in mixing of sediments and fossils.
A log of the 12 deepest holes is included in the appendix. The lithologies are described, fossil species listed, and stratigraphic subdivisions indicated. A diagram showing correlation of the sections is included below (fig. 29).
The materials penetrated by the test holes range in age from late Miocene to late Pleistocene or Recent. The formations recognized are the Tamiami, Caloosahatchee marl, Fort Thompson, and Pamlico.
Many beds are very fossiliferous and thus are readily assigned to formations. Some beds lack diagnostic fossils, however, so that their classification (in a few localities) has been left doubtful.

TAMIAMI FORMATION

The Tamiami formation was identified in all the holes drilled between La Belle and Olga. Its penetrated thickness ranges from 35 to 62 feet, but the base was not reached in any of the holes. West of Ft. Denaud the overlying beds belong either to the Fort Thompson or the Pamlico formation but east of Ft. Denaud the Tamiami formation is overlain by either the Caloosahatchee marl or the Fort Thompson formation.
The upper beds of the formation are usually light colored clays, argillaceous marls, or sands. Fossils are rare and usually consist











UU

co - [ t W r, oN1_ E



- W oAI to FO RM ATO
') r: V \
0







10MIAM FO TORT THMSO OMAIN 50 I 0 60 "
20 'n


30





T FPA MLICO FORMATION
60













BASE OF THE CALOOSAHATCHEE MARL


Figure 29
Correlation of subsurface sections along the Caloosahatchee River between Olga and Lake Hicpochee. Data for sections Si, S2, and SS were taken from Schroeder and Klein, 1954.







LATE NEOGENE STRATA OF SOUTHERN FLORIDA


only of fragments of barnacles, a few pelecypods (such as Chlamys sp. and Ostrea sp.), and echinoid spines. Several typical late Pleistocene species were identified from a few samples, but their presence was accounted for by caving from above.
In most places the lower beds are dark olive green sands, arenaceous clays, or marls. The entire sequence tends to become more arenaceous toward the west. Many of the lower, as well as upper, beds are slightly or moderately phosphatic. Fossils are rare and most of them are the same species that occur in the upper units.

CALOOSAHATCHEE MARL
The Caloosahatchee marl was identified in all the holes east of Banana Creek except number 12 located south of La Belle. In the La Belle area and westward the formation ranges in thickness from five to 25 feet and the base was reached in all the holes. East of La Belle the base of the Caloosahatchee marl was not reached, its penetrated thickness ranging from 45 to 65 feet. West of La Belle the overlying beds belong to the Pamlico formation and to the east the Caloosahatchee marl is overlain by the Fort Thompson formation.
Most of the Caloosahatchee beds are poorly consolidated light colored sandy marls and almost all the units contain abundant megafossils. West of Ortona most of the lower beds are light to dark gray or green sands or sandy marls that carry an exceptionally abundant well preserved marine molluscan fauna. Fresh-water species are rare in those beds. Several molluscan species that are rare in the exposed strata occur commonly in the sandy subsurface beds east of Ortona Locks. These species include Donax fossor, Anachis camax, and Terebra concava. The presence of Donax fossor suggests a shallow-water near-shore continental shelf environment.
As pointed out by Schroeder and Klein (1954, p. 4) and the writer, the surface of the Tamiami formation is uneven and the Caloosahatchee marl is deposited on top, and along the flanks, of the erosional remnants.
FORT THOMPSON FORMATION
The Fort Thompson formation was identified in all the holes drilled east of La Belle. The only beds of the formation recorded west of La Belle are at Olga. The thickness of the formation ranges from five to 25 feet or more. The lower 40 feet of the section at







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old Lock No. 3 is tentatively assigned to the Caloosahatchee marl on the basis of one diagnostic Caloosahatchee fossil in an assemblage that otherwise seems most closely related to the typical Fort Thompson fauna. The upper 25 feet of the section definitely is Fort Thompson; therefore, in this one area the Fort Thompson formation possibly reaches 65 feet in thickness.
All along the river the Fort Thompson formation is overlain by Pamlico sands and is underlain by Caloosahatchee marl or, in a few places, by the Tamiami formation.

PAMLICO FORMATION

Light gray to brown quartz sands of the Pamlico formation were identified from all the cores. At several localities the sands were mixed with Recent soils and muck similar to the Lake Flirt deposits. At most localities the thickness of the sands is five feet or less, but at Olga the thickness is approximately 10 feet.
The sands lie unconformably on the underlying surface which locally may be composed of any one of the lower formations discussed above.

PALEOECOLOGY

GENERAL DISCUSSION

The highly fossiliferous beds of the Caloosahatchee marl and Fort Thompson formation are ideal subjects for paleoecological interpretation. The fossils are almost perfectly preserved, easily extracted from the matrix, and many species still live in Floridan waters. The marine pelecypods and gastropods are most abundant, so the interpretations were based, for the most part, on those groups but some data also were drawn from study of the echinoids, corals, fresh-water gastropods, and the vertebrates. Faunal evidence was supplemented by study of the various associated sediments.
Wherever possible, ecological data derived from present day species were used in the interpretations. Especially helpful were papers published recently by Parker (1956), Shepard and Moore (1955), Puffer and Emerson (1953) and others. Much useful information concerning the distribution and ecology of Recent mollusks was derived from papers by Bartsch (1936), Dall (18891903), Gunter (1951), Ladd (1951), Maury (1920, 1922), Perry (1940), Pulley (1952), and others.







LATE NEOGENE STRATA OF SOUTHERN FLORIDA


Despite some good papers on the ecology of Recent mollusks, little has been published on assemblages from the Gulf of Mexico, Caribbean and Atlantic slope areas, and there are no published accounts of detailed paleoecological studies of Floridan Neogene molluscan assemblages.
Dall (1903, p. 1604) records 639 species of mollusks from the Caloosahatchee marl. The writer has identified 272 species of gastropods, 163 species of pelecypods, and several species of scaphopods, echinoids, and barnacles from the Caloosahatchee and Fort Thompson formations. In addition, six species of corals were identified by Dr. John Wells, and several species of vertebrates were identified by Walter Auffenberg and Herbert Winters. The microfauna is presently being studied by Dr. Harbans Pur.
The molluscan assemblages of approximately 65 samples were analyzed. The average volume of the samples was 600 cubic inches. The number of mollusks present in each of the samples ranges from 60 to 9,847, and the average is about 3,000 specimens. The total number of molluscan specimens contained in these samples is more than 200,000. Pelecypods outnumber gastropods in most of the assemblages, even though two pelecypod valves were always counted as one individual.
After the number of individuals of each species contained in a sample had been determined, data were converted into percentage of the total number of individuals in the class to which the species belongs. It was found that some of the small species occur in great numbers and, in terms of percentage of the total assemblage, appear to be of much greater importance than larger, more conspicuous elements of the fauna. To this extent the figures are somewhat misleading. In the following discussion two groups of species usually are listed for each facies or bed. The first group includes the most abundant species (usually small forms) and the second includes common species (usually large forms), the presence of which seems important despite the fact that they may comprise less than one percent of the total fauna.
Numerous facies and biotopes are represented in the Caloosahatchee marl and the Fort Thompson formations. These suggest varied environmental conditions in close proximity and also frequent changes in environmental conditions within any given area. Because of these many variations, detailed stratigraphic and paleoecological studies are made difficult but none the less intriguing.
This study reveals that almost all of the deposits of the Caloosahatchee marl and the Fort Thompson formation were formed in shallow water. The chief exception is the Bee Branch member of







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the Caloosahatchee marl; probably it was deposited on the continental shelf in water that was at least 15 fathoms deep (discussion on p. 107). The upper Caloosahatchee shell bed may have formed on the shallow continental shelf, and it seems that some of the subsurface sands east of Ortona were deposited in such an environment. Many of the remaining Caloosahatchee beds seem to have developed in protected inlets, bays, and lagoons. Some beds contain a predominance of high-salinity shallow-water bay species such as Chione cancellata; others are characteristically brackish in composition, and some transitional beds contain high-salinity and brackish-water forms in equal abundance. Several small and one large oyster biostrome are present in the Caloosahatchee marl, but these are not known in the Fort Thompson formation. The marine beds of the Fort Thompson formation typically alternate with fresh-water marls and probably have formed in protected inlets and bays. The upper Caloosahatchee marine beds of the Ortona Locks area, however, were probably deposited offshore in deep water.
Apparently at no time during the deposition of the exposed Caloosahatchee and Fort Thompson beds of the Caloosahatchee River area did land lie far to the north. At times, especially in Fort Thompson time, and at the close of Caloosahatchee time, the area was at least partly emergent. During this entire period the land is inferred to have been low-lying sandy and swampy much as Florida is today. Gastropods thrived in great numbers in the fresh water and alligators, turtles, and fish lived in abundance in the rivers and lakes. Elephants, deer, and the horse Equus (Equus) cf. E. (E.) leidyi were common on the land at that time. Storms and floods washed the remains of land and fresh-water snails and many of the fresh-water and terrestrial vertebrates into the nearby sea where they became mixed with the shells of marine invertebrates.
The water of the Caloosahatchee sea was warm. The minimum temperature seems to have been no lower than 650 F. Many of the typically tropical species of the Caloosahatchee marl are absent in the Fort Thompson beds suggesting a general but probably slight lowering of the average annual sea water temperature. Both formations appear to have been deposited during warm interglacial stages.







LATE NEOGENE STRATA OF SOUTHERN FLORIDA


CALOOSAHATCHEE MARL
CYRTOPLEURA COSTATA FAUNIZONE General Statement
The pholadid clam Cyrtopleura costata Linn6 is rare in most of the faunas of southern Florida. Along the Caloosahatchee River the species is usually confined to the lower beds. Most specimens occur in colonies in a single thin bed situated at or near the base of the section. A few specimens were observed in the overlying units, but none were recorded from the Fort Thompson formation. In nearly all places the specimens underlie the lowermost oyster biostrome and the bed in which they are contained may grade up into the oyster marl with no pronounced lithologic break.
Most specimens are oriented erectly in their burrows as in life. They are large, about five to six inches long, and are well preserved (fig. 14).
The zone is most typically developed downstream from La Belle, between stations A30 and A38 where there is a large concentration of specimens. The beds are undulatory within this area, so that the zone dips below water level in several places.
In many localities few or no specimens of Cyrtopleura costata are found and so the zone must be recognized by its associated forms, by its relationship to overlying and underlying units, or by lateral tracing.
Present day colonies of Cyrtopleura costata are distributed from Massachusetts through the Gulf and north coast of South America to Brazil. The species live in the shallow neritic zone in mud or sandy mud where they form burrows as much as two feet in depth. Commonly many of these clams live together in colonies.
On the larger West Indian Islands Cyrtopleura costate lives only in high salinity bays and in shallow water immediately offshore; usually in mud or sandy mud bottom4 Its minimum temperature tolerance is about 350 F. Turner (1954, p. 38) recorded specimens from Delaware Bay (four fathoms), Chesapeake Bay (one-half fathom), and Sanibel Island, Florida (no bathymetric data given).
Inasmuch as the species is a deep burrower, specimens found oriented in their burrows must be younger than the surrounding sediments and fossils. This age difference is, as pointed out earlier in the paper, slight and. as there seems to be only one bed or layer of these clams, the period of time when an environment
4Pulley, T. E., personal communication, 1954.







90 FLORIDA GEOLOGICAL SURVEY-BULLETIN FORTY

favorable to their development existed must have been extremely short. Most colonies are overlain by a dense mat of oysters which succeeded them in the area, and which probably indicate a reduction in the average salinity of the water.
When the Cyrtopleura costata faunizone is traced laterally, it can be seen that several facies exist. At least three of the facies are distinct enough to be worthy of note:

1. Brackish, shallow-water facies
2. High-salinity bay facies
3. Turritella facies

The lateral distribution of the most common species is analyzed below (fig. 30-33).
The data used in these figures are based on collections from the area of most typical development for each of the three facies.

Brackish-Water Facies

In the vicinity of stations A31, A33, and A36 located upstream from Ft. Denaud, the fauna of the Cyrtopleura costata faunizone


Figure 30
Relative abundance of the most common gastropod species included in the principal facies of the Cyrtopleura costata faunizone. Percentage figures are
based on the total gastropod fauna for each station.


KEY TO GASTROPOD SPECIES
E Acteoina �onoliculoto



et-n-tica p-41.l
Culyptwea centrails


I- FACIES OF THE CYRTOPLEURA
COSTATA ZONE







LATE NEOGENE STRATA OF SOUTHERN FLORIDA


KEY TO GASTROPOD SPECIES
100 FACIES OF THE CYRTOPLEURA Cmpidlo fo,.
COSTATA ZONE B] i 90
0
70
r60'
(Z4 50
U

1O1
o4
CL.40
20
20
10
A3 117 A23
BRACKISH-WATER HIGH SALINITY BAY TURRITELLA

Figure 31
Relative abundance of the most common gastropod species included in the principal facies of the Cyrtopleura costata faunizone. Percentage figures are
based on the total gastropod fauna for each station.

is characterized by an abundance of such species as Mulinia sapotilla, Mytilopsis lamellata, Rangia nasuta, Acteocina canaliculata, Bittium podagrinum, and Neritina sphaerica. Such a faunal assemblage is judged to be indicative of a brackish, shallowwater, near-shore environment. Typical high-salinity forms and deep-water species are absent or represented by only a few specimens. Fresh-water species such as Helisoma conanti, H. disstoni, and Fontigens plana are numerous and suggest that the deposit formed close to shore where the shells were washed out to sea by streams or storm-produced waves. The absence of Crassostrea virginica might be attributed to a wide annual range in chlorinity due to the influx of fresh water from streams during periods of heavy rainfall.
Lithologically, the facies is represented by a poorly consolidated, cream colored marl. The insoluble residue of a sample from station A35 is only 10.5 percent by weight, of which about 71.4 percent by weight is composed of fine quartz sand and silt.
This facies seems nearly identical with that of the Caloosahatchee brackish-water beds that overlie the lower oyster biostrome. The fossil assemblages and lithologies of each are similar. Of the sedimentary environments recognized by Shepard and Moore









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KEY TO PELECYPOD SPECIES
E Nucula proxima Nuculana acuta WGlycymeris crata floridana Mytilopsis lamellate Cardita tridentata Phacoides multilineatus Phacoides waccamawensis
80--------


0 L ..... . ...--------A35 A17 A23
BRACKISH-WATER HIGH SALINITY BAY TURRITELLA


FACIES OF THE CYRTOPLEURA COSTATA ZONE

Figure 32
Relative abundance of the most common pelecypod species included in the principal facies of the Cyrtopleura costata faunizone. Percentage figures are
based on the total pelecypod fauna for each station.








LATE NEOGENE STRATA OF SOUTHERN FLORIDA 93


KEY TO PELECYPOD SPECIES
- Trigoniocardia willcoxi Chione cancellara EM Parostarte triquetra W] Tellina suberis Mulinia sapotilla Rangia nasuta

-- Caryocorbula leonensis Varicorbula caloosae




8 0 . . .. .
80------60V

50 \

E-4
z
U









0
A35 A17 A23
BRACKISH WATER HIGH SALINITY BAY TURRITELLA

FACIES OF THE CYRTOPLEURA COSTATA ZONE

Figure 33
Relative abundance of the most common pelecypod species, included in the principal facies of the Cyrtopleura cos tata faunizone. Percentage figures are
based on the total pelecypod fauna for each station.







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(1955) in the Gulf of Mexico off the coast of central Texas, the "Bays near rivers" is most closely related to the brackish-water beds of the Caloosahatchee marl.

High-Salinity Shallow-Water Bay Facies

A facies near Fort Thompson is thought to represent an environment intermediate between the brackish-water and Turritella facies (fig. 34, p. 94). Judging from the percentage of highsalinity species present, this bay facies is more closely related to the Turritella facies of station A23. The high-salinity bay facies does include, however, a higher percentage of brackish-water and fresh-water forms than the Turritella facies. This mixing of ecologic types may have resulted from an overlapping of the extremities of the ranges of the high-salinity and brackish-water species, or it may be partly the result of wave and current action after death of the organisms. The low percentage of specimens of Turritella may be evidence of greater turbidity and more shoalwater conditions than obtained when the beds of the Turritella facies were deposited.


Figure 34
Marl sample representing the Turritella facies of the Cyrtopleura costata faunizone (station A23).








LATE NEOGENE STRATA OF SOUTHERN FLORIDA


Molluscan remains are abundant in the high-salinity bay facies. A 700-cubic inch collection from station A17 yielded 3,000 individuals of 60 species of pelecypods and more than 1,500 individuals of 54 species of gastropods.
Lithologically, the facies is a cream to white, slightly indurated sandy marl. The insoluble residue of a sample from station A17 is 49.5 percent by weight, of which approximately 96.0 percent is more coarse than 1/64 mm. The sand consists primarily of quartz with a small percentage of mica. The diameter of most of the quartz grains is 1/4 mm. or greater. The larger grains are generally well rounded, and most of those one mm. or more in diameter are frosted. The finer sand fraction consists characteristically of subangular clear grains of quartz.
This facies probably developed in a bay, perhaps near an inlet, where the water was shallow (less than five fathoms), where wave and current action was moderate, and where the average annual salinity exceeded 30 parts per thousand. Shoreward, the environment was gradational to a shallow brackish-water environment and toward deeper water, to a high-salinity marine environment where the bottom waters were relatively quiet and where Turritella apicalis thrived in great numbers.
Turritella Facies
The Turritella facies was recognized by Mansfield (1939, p. 20). He considered it to represent a deep-water environment but does not elaborate on this observation. The facies is known from only a small area at and near station A23 (fig. 35, p. 96; fig. 36, p. 97) about two miles downstream from La Belle. Lithologically the facies consists of a poorly consolidated sandy marl (fig. 30, p. 90). The most diagnostic facies fossil is Turritella apicalis, which is abundant in the Cyrtopleura costata faunizone at station A23, but is generally rare or altogether absent in other facies of the zone. Specimens of T. perattenuata are also common but T. subannulata, abundant in many other Caloosahatchee beds, was not recorded.
Turritella apicalis and T. perattenuata are extinct species, therefore no direct evidence of their environmental requirements is available from living specimens. Merriam (1942, p. 1-213) made a detailed study of present day North American species of Turritella in which he analyzed the ecology of the genus in some detail. He concluded, from studies of many species, that the genus is not characteristically an inhabitant of the littoral zone but is more or less confined to the neritic belt (low water to a depth of 100








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1 5 3
LOWER MARL CYPTOPLEURA COSTATA OYSTER BIOSTROME UPPER SHELL IED ZONE
CALOOSAIATCHEE BEDS (SIATION A.3)
Figure 35
Relative abundance of most common pelecypod species in beds of the Caloosahatchee marl at station A23, on the Caloosahatchee River about 1.5 miles downstream from La Belle. Percentage figures are based on the total pelecypod fauna in each bed.

fathoms). He observed also that the genus seems to form densely populated colonies where the wave and current action is moderate.
Most species associated with Turritella in this facies are suggestive of a high-salinity bay or offshore environment. Species judged to be typical of a brackish-water environment such as Rangia nasuta and fresh-water forms are relatively rare. Deepwater shelf forms such as Amusium are absent, but others like Calyptraea centralis are common.
The insoluble residue of a sample from station A23 is 48.5 percent by weight. The coarse fraction (greater than 1/64 mm.) constitutes approximately 90.0 percent by weight of the residue. The sand is comprised predominantly of quartz and seems not to differ from that found in the intermediate facies described above (A16 and A17).


KEY TO PELECYPOD SPECIES

"E 'ojJ C.o ii ....00 .....F,~








LATE NEOGENE STRATA OF SOUTHERN FLORIDA 97


KEY TO GASTROPOD SPECIES



1. .,o -,




90




W 0
70







30
IA




0 -------- S
LOWER MARL CYRTOPLEURA COSTATA ZONE OYSTER BIOSTROME UPPER SHELL BED STATION A23

Figure 36
Relative abundance of most common gastropod species in beds of the Caloosahatchee marl at station A23 on the Caloosahatchee River about 1.5 miles downstream from La Belle. Percentage figures are based on the total gastropod fauna in each bed.

The facies developed where the salinity was high and fairly stable. Depth of the water probably was less than 10 fathoms. That the bottom was not affected by heavy wave or current action is strongly indicated by the nearly perfect preservation of the shells.

LOWER OYSTER BIOSTROME AND RELATED STRATA Oyster Biostrome
Several beds of oysters are, exposed along the Caloosahatchee River and all are confined to the Caloosahatchee formation. The lowest bed, which overlies the Cyrtopleura costata faunizone, is







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the best developed and laterally most extensive. Since it is doubtful that the oysters anywhere formed a ridge or mound-like formation rising noticeably above the surrounding substrate, the term reef is not employed to describe the bed. The most accurate designation is probably "oyster biostrome" where reference is made to the entire unit including the oysters, associated organisms, and the sediments. The term "colony" is applied to the accumulation of oyster shells, which are considered to be essentially or actually in place.
The oyster colony is not equally developed everywhere. Physical factors conducive to oyster growth seemingly were not uniform throughout the entire extent of the biostrome. At some localities the unit contains mostly large naturally oriented valves of Crassostrea virginica (Linn6). At other localities most valves of this oyster are small and may be thoroughly scattered and mixed with the sediment and abundant remains of other organisms. The oysters are rare in some places and the fauna has a more normal marine appearance. There is also variation in the shape of the oyster valves. In the largest colonies the valves of adult specimens of Crassostrea virginica are generally six to nine inches long, rather smooth, and straight or sickle-shaped. At some stations they are smaller, relatively broad, and more crenulated. These differences in communal and individual structure and faunal composition reflect the variety of physical and biological factors existing in close proximity on the sea floor at the time the biostrome was formed.
Dall (1898, p. 675-676) discussed the variations observed in Crassostrea virginica as follows:
"When a specimen grows in still water it tends to assume a more rounded or broader form, like a solitary tree compared with its relatives in a crowded grove. When it grows in a tideway or strong current the valves become narrow and elongated, usually also quite straight. Specimens which have been removed from one situs to another will immediately alter their mode of growth, so that these facts may be taken as established.
When specimens are crowded together on a reef, the elongated form is necessitated by the struggle for existence, but instead of the shells being straight they will be irregular and more or less compressed laterally. When the reef is dry at low stages of the tide, the lower shell tends to become deeper, probably from the need of retaining more water during the dry period .... When an oyster grows in clean water on a pebble or shell, which raises it slightly above the bottom level, the lower valve is usually deep and more or less sharply radially ribbed, acquiring, thus a strength







LATE NEOGENE STRATA OF SOUTHERN FLORIDA


which is not needed when the attachment is to a perfectly flat surface which acts as a shield on that side of the shell. Perhaps for the same reason oysters which lie on a muddy bottom with only part of the valves above the surface of the ooze
are less commonly ribbed."
In addition to Crassostrea virginica, Ostrea sculpturata is common at most stations studied. In places this species even exceeds Crassostrea virginica in number of specimens. The ecologic significance of this relationship is not known.
Maury (1920, p. 25) reports the present day distribution of Crassostrea virginica Linn6 to be ".... Canada to Mexico and the Gulf of Mexico." It is extremely abundant and one of the world's most prolific species. Because of the economic aspect, its life habits have been more closely studied than most other marine mollusks.
The species is capable of occupying numerous ecologic niches. Where conditions are optimum it may form large reefs on which many other organisms find lodging and food. Most reefs have developed in inner bays and estuaries where wave action is slight, and the supply of fresh water from streams is not excessive (Price, 1954, p. 491).
Crassostrea virginica is typically a brackish-water or estuarine species. It must live where there is a proper mixture of salt water with fresh water. It will survive within a wide salinity range but near the extremities it becomes much impoverished in size and abundance. Butler (1954) reported that ". . . permanent communities establish themselves and flourish within a salinity range of 10 to 30 parts per thousand." He pointed out that the population density on an oyster reef is greatest where the salinity ranges between 10 and 20 parts per thousand with an annual average of about 15 parts per thousand.
According to Parker (1956, p. 372) if the chlorinity is reduced below 11 parts per thousand due to small streams emptying into the bay, reefs of Crassostrea virginica develop.
Crassostrea virginica lives in shallow water from a foot or so above mean low water to a depth of 30 to 40 feet (Butler, 1954, p. 479). Sinuous passageways through tidal fiats in southern Florida have been reported by Bartsch (1936, p. 18) as a habitat of Crassostrea virginica and Cyrtopleura costata.
Large colonies develop best where the bottom is stable. If the bottom is too soft to support the weight of an adult oyster, spat may settie and grow on shells lying on the surface. This apparently was the case in the Caloosahatchee beds where the oysters are commonly attached to large, flat valves of Chlamys solarioides.








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In the shallows of San Carlos Bay, located just south of the mouth of the Caloosahatchee River, Haas (1940, p. 372) reported the presence of reefs of Crassostrea virginica built over a relatively hard bottom of coquina and dead coral. Adjacent areas of similar depth, but with a loose sand bottom, lack these reefs and in their place are found Atrina rigida, Chlamys gibbus dislocatus, and Venus campechiensis.
In the Mississippi delta region Parker (1956, p. 317), found extensive reefs of living Crassostrea virginica in the large bays of the delta. This environment was termed the "Delta front and lower distributaries." It is characterized by ". . . low chlorinity (2-10 0/00), wide range of temperature, fine, clayey silt substrata, shallow water, and proximity to the marshes (and) is also characterized by a scarcity of species and individuals of macroorganisms."
The geographic range of Crassostrea virginica suggests that its temperature tolerance is great. Butler (1954, p. 484) stated that the species is found where the annual range is as much as minus 20 C to plus 300 C. Temperature varies more in shallow water near shore than in deeper water offshore.
Some of the most abundant small species associated with the Caloosahatchee oysters are listed below:

Pelecypoda

Nuculana acuta (Conrad) Cardita tridentata (Say)
Phacoides multilineatus (Tuomey and Holmes)
Chione cancellata (Linn6)
Mulinia sapotilla Dall
Varicorbula caloosae (Dall)

Gastropoda

Acteocina canaliculata (Say)
Nassarius bidentatus (Emmons)
Calyptraea centralis (Conrad)
Turritella subannulata Heilprin
Turritella apicalis Heilprin

Other small marine species, that locally occur abundantly, are Bittium podagrinum, Neritina sphaerica, Crepidula fornicata, and Parastarte triquetra (fig. 37, 38).
Fresh-water species, including Helisoma conanti, H. disstoni, and "Fontigens" sp., are abundant at most localities.
Among the larger marine species the following are relatively common or abundant:




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