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 Title Page
 Letter of transmittal
 Abstract
 Acknowledgement
 Table of Contents
 Part I: Stratigraphy
 Part II: Systematic paleontolo...














Stratigraphy and paleontology of the late Neogene strata of the Caloosahatchee River area of southern Florida ( FGS: Bul...
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Permanent Link: http://ufdc.ufl.edu/UF00000241/00001
 Material Information
Title: Stratigraphy and paleontology of the late Neogene strata of the Caloosahatchee River area of southern Florida ( FGS: Bulletin 40 )
Series Title: ( FGS: Bulletin 40 )
Physical Description: 267 p. : illus. tables, 12 pl. ; 24 cm.
Language: English
Creator: Florida Geological Survey
DuBar, Jules R
Publisher: Published for the Florida Geological Survey
Place of Publication: Tallahassee
Publication Date: 1958
 Subjects
Subjects / Keywords: Geology -- Florida   ( lcsh )
Genre: non-fiction   ( marcgt )
 Notes
Statement of Responsibility: by Jules R. DuBar.
Funding: Geological bulletin (Tallahassee, Fla.)
 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: aleph - 002037000
oclc - 01728190
notis - AKM4760
System ID: UF00000241:00001

Table of Contents
    Title Page
        Page 1
        Page 2
    Letter of transmittal
        Page 3
        Page 4
    Abstract
        Page 5
        Page 6
    Acknowledgement
        Page 7
        Page 8
    Table of Contents
        Page 9
        Page 10
    Part I: Stratigraphy
        Page 11
        Page 12
        Table of contents
            Page 13
            Page 14
        List of illustrations
            Page 15
            Page 16
            Page 17
            Page 18
        Introduction
            Page 19
            Page 20
            Page 21
            Page 22
            Page 23
            Page 24
            Page 25
            Page 26
        Stratigraphy of southern Florida
            Page 27
            Page 28
            Page 29
            Page 30
            Page 31
            Page 32
            Page 33
            Page 34
            Page 35
            Page 36
            Page 37
            Page 38
            Page 39
        Stratigraphy of the upper Caloosahatchee River area west of Ortona Locks
            Page 40
            Page 41
            Page 42
            Page 43
            Page 44
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            Page 70
            Page 71
            Page 72
            Page 73
        Stratigraphy of the Ortona Locks area
            Page 74
            Page 75
            Page 76
            Page 77
            Page 78
            Page 79
            Page 80
            Page 81
            Page 82
        Subsurface stratigraphy along the Caloosahatchee River
            Page 83
            Page 84
            Page 85
        Paleoecology
            Page 86
            Page 87
            Page 88
            Page 89
            Page 90
            Page 91
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            Page 131
            Page 132
            Page 133
            Page 134
            Page 135
        Age relationships
            Page 136
            Page 137
            Page 138
            Page 139
            Page 140
            Page 141
            Page 142
            Page 143
        Summary
            Page 144
            Page 145
        References
            Page 146
            Page 147
            Page 148
            Page 149
            Page 150
    Part II: Systematic paleontology
        Page 151
        Page 152
        Page 153
        Page 154
        Page 155
        Page 156
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        Plates 1-12
            Page 243
            Page 244
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Full Text








STATE OF FLORIDA
STATE BOARD OF CONSERVATION
Ernest Mitts, Director


FLORIDA GEOLOGICAL SURVEY
Robert O. 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









.0;?


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






452
2i


{- j- -' '










LETTER OF TRANSMITTAL


Jloriaa ceolocical Survey

Callakassee
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 Bul-
letin 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 O. VERNON, Director






3


60452




























































Completed manuscript received
February 28, 1957
Published for the Florida Geological Survey by
E. O. 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. De-
tailed stratigraphic relationships, relative age, and environments of
deposition of the Caloosahatchee marl and the Fort Thompson for-
mation are established. Both of these stratigraphic units are con-
sidered 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 pro-
vided criteria helpful in recognition of members and facies, and
interpretation of depositional environments. Comparison of fossil
molluscan, echinoid, and coral assemblages with living communi-
ties in the Gulf of Mexico, Caribbean, and western Atlantic re-
gions has yielded valuable data concerning the ecological factors,
such as salinity, depth of water, temperature of water, and tur-
bidity, which probably prevailed during the time in which the
Caloosahatchee marl and Fort Thompson formations were de-
posited.
In southern Florida the Caloosahatchee marl rests unconform-
ably 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 for-
mation is composed of a succession of shallow-water marine and
brackish-water marl, sandstone and limestone, and a few inter-
calated 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 Caloosa-
hatchee 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 verte-
brate species have never been recorded from beds older than Pleis-
tocene. 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. Paleo-
ecological and paleogeographical studies indicate that the Caloo-
sahatchee 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 Wi-
comico 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 paleoeco-
logical 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 Kan-
sas, 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 col-
lection 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 facili-
ties 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 ---_-.------------- -- 3
Abstract ..._ ..... ..... 5
Acknowledgments ....------...------------...---... ------- -.--.. 7
Part I Stratigraphy --_ ..-. -------_...-------.--------... 11
Part II Systematic Paleontology __ --- -----..- ------ 151
Appendix ..---.. -- --...------ ...-. ---..----..-...--- .. 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
General discussion --...---........- --------- ----- 27
Late Miocene deposits ---- __-..- --.....-.-.. ...-....- ...--.-..... 29
Buckingham marl --. ---------- -------29
Tamiami formation -.. --------........ .. ------------- 29
Definition -__..- ----------- .--...-- ------ 29
Lithologic character --..----- ------ 30
Age ------------ ------- 31
Thickness -......------ --------------- .. .-.- 31
Older Pleistocene deposits --..__-----------------.-... 34
Caloosahatchee marl --- ----_----- -.--.....-....----- 34
Definition ....--_ -------- .---------. 34
Lithologic characteristics -..--------------------------.. 34
Age ..----- ...-- ---- ---------...-...-. 35
Thickness ---------- -- ----- .--.- .--..--.. 35
Distribution ---------------- -.------- --35
Younger Pleistocene deposits ------.-----------.---.. ..--- -- 38
General discussion ..-- ..--. --...__ ..----- ---- 38
Fort Thompson formation -.__---------..........- -... --..-- 38
Anastasia formation .. ---------.---.-----.- --.------ 38
Key Largo limestone -_.... --------------_----------------.- 39
Miami oolite .... -----------. --------------------- 39
Pamlico formation ..---------..-- --.........- 39
Lake Flirt marl ....- --------------. ------------- 40
Stratigraphy of the upper Caloosahatchee River area west of Ortona Locks 40
General observations .---.----..---.---- ... ---40
Tamiami formation ---- ---....-...---- .--------- 47
Exposures west of Ft. Denaud .------...---- --------- 47
Exposures east of Ft. Denaud .----------------.- -- ..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 Flirt marl ---_..-..----_....-
Stratigraphy of the Ortona Locks areas

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 marl ----_-_--

Fort Thompson formation ---__--...

Pamlico formation -....-.......--------.

Paleoecology ...--..- .........---. .._- ....

General discussion ...-----

Caloosahatchee marl ----.------
Cyrtopleura costata faunizone
General statement ------
Brackish-water facies
High-salinity shallow-water
Turritella faces --...---
Lower oyster biostrome and rela
Oyster biostrome ---__
Brackish-water beds ...._----
Bee Branch member --..-__.- ..._. ..
Upper Caloosahatchee shell bed
Invertebrate faunas .....
Vertebrate fauna ----- -...-----


ne .----..---.. ------.. 53
-- ----..--- ....-....----- 55
58
------ 58
---.......-------------.........................-. .-- ---- ------- 68
---.-- ....- ....-----. ---- 61

---- ---.. .. --- .----- 64
--- ------------ 64
--...---------- ----- ..-- 66
--.---.-.--------- 70
--. . ..--------- --- 70
-..- .-70
.---. ...-.......- -- ----.. .. ..-----------.. 71
-------------------- 71
73
.-----.. .----.. ----. -----.------- 74
i .-.- -----...--------------------------------------- ------..... 74

---..--------..----- .----- 74

76
76
------80
80
.....-. .--.-.-- -...-..........................------- --.. -..-. 80
------- 80
81
82
--------------- 82
it 10) 8-------.---- 83

oosahatchee River -...88-----------. .-- 83

83
.-- 83

85
--- ..-.- .......-------....- 85
- _--- -- -- --- -- -- -- -- -- ------ 8 5


-------------- 86
.-. ... ..... .... ...- -- -- 86

-- ------ ---- 86
--- _---- -------------------------- ----_- --- 89

----......... ... ..-- ....- .......... ...... ...... ....... ........- 89
89
89
---- --------- --------- 89
90
bay facies ------ ----- 94
- -- ---- 95
ted strata ----- ----- -- 97
97
----------------------- ---- 105
---........ ..............-- ...-- ...... .............. ........... 107
--- -----------.. --------- ... .... .. 107

..--.. .... ..... -- --. .--... ... 114
---- ------ ..... ....-- ...---......-- 122


Fort Thompson formation -- ----------- ...... ...
Chlamys bed ---------- -..--..
Coffee Mill Hammock marl __.-------------------------.-.
General statement ....- -- ---------------............
Type locality -..-..-- ---_-. _------._... .- ........--------------
Deposits west of the type locality .--------.... ------...__...........








Age relationships .---.---.....-........---.--.- ------------
Age of the Caloosahatchee marl ..----...--.------- ---..-----..---
General discussion --.----.-.---------- ----------
Evidence of the invertebrate fauna _-- .._ --- ----
Evidence of the vertebrate fauna --...------------ -----------.-
Relationship to Pleistocene marine shorelines ---- ---
Correlation with other units ._--.----___ -----
Conclusions ---------------------... ...---------
Age of the Fort Thompson formation ---------------.-...--..--..
Evidence of the fauna ----___._... ---------..----------
Relationship to the glacial and interglacial stages -----
Conclusions .-----------------.----------- ..- ------
Age of the Pamlico formation---- ------------ -
Summary __--._--. --_ --...------..--_______ .---.------ -----
References -..--.. ------..--------- .


---. 136
-- 136
.--- 136
--- 137
--- 138
140
140
---.-- 142
-- -._- 142
.-- 142
-- 142
------. 144
-- 144
-..- 144
--- 146


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 Index to geologic map parts ----.....------------.. ..
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 limestone ....--- --.....------- ---- --.--








16 Specimen of the Bee Branch limestone from the type locality ...--..----- 59
17 Upper Caloosahatchee shell bed at station A35, one mile upstream
from Ft. Denaud ----- --------- -...-----.-------. .....-... .. 62
18 Specimen of upper Caloosahatchee shell bed from station A34, ap-
proximately 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 Caloosa-
hatchee River east of La Belle ---------------_-------- ..__________ 67
21 Exposure of Fort Thompson and Pamlico deposits along Banana
Creek ----------------------. -- ---------- ---- --..-.------ -----.--....... 69
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 A23) ------- -. --. 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 approxi-
mately 1.0 mile 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 ex-
posures 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 La Belle --____--___. ....._--..----_---- ... _-7__. ......- .- 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 down-
stream from La Belle .--_.. ---- -_ -----..........----- 118
47 Sample of the Coffee Mill Hammock marl collected from an exposure
at Old Lock No. 3 _-- ---____..-_-_-.. ----- -- ----..... 126
48 Generalized geologic cross section near station A33 ---- --. __ 134
49 Vertebrate fossils being removed from Fort Thompson deposit (sand
faces of the Coffee Mill Hammock marl) at station A33 on Caloosa-
hatchee River approximately 2.0 miles upstream from Ft. Denaud --_ 136
Plate
1 Correlation of stratigraphic sections along the Caloosahatchee River:
part A -_____ -------_-- ---- -__ I ..p._____k 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
Ft. Denaud ....._----_--_...__ --_ ----.. -_- .. ........------- 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. Denaud .----........._._-... ----. ---_ _-- -_- ....._.----------..-_ 64
5 Recent Gulf of Mexico oyster reef faunal assemblages collected off
the coast of Texas ..... -----------..-. ... ...-... --. ... -- 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 com-
pared 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 Flor-
ida (fig. 1, p. 20; fig. 2, p. 21) between latitudes 270 N. and 260 N.;
it is bounded on the west by the Gulf of Mexico and extends east-
ward 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. High-
way 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 Har-
bor lies north of the Caloosahatchee. This system includes the
Myakka River and Peace, Shell, and Home creeks. In places, along


0 60 120
Miles








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 topo-
graphic 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.







ZZ 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, gen-
erally wet throughout the year except where drained." The area
is underlain by peat, muck, and marl. The division is mostly tree-
less, 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 paleon-
tological 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 in-
terpret 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, 1895-
1903; 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 ma-
terial. 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 Okeecho-
bee. 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 col-
lected 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 Ceno-
zoic 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 sum-
mary of late Cenozoic geology of southern Florida. In addition
to a discussion of all formations of the region, it includes descrip-
tions of stratigraphic sections occurring along the Caloosahatchee
River, logs of test wells drilled in southeastern Florida, cross sec-
tions of subsurface geology, and maps depicting geology, topog-
raphy, 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 opin-
ions 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 Caloo-
sahatchee 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, es-
pecially where softer marls were encountered, an attempt was
made to obtain a quantitatively representative fauna. To accom-
plish this about 0.5 to 1 cubic foot of matrix was shoveled or other-
wise dug from the desired bed, sacked and labeled. To reduce ship-
ping 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 down-
stream 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


1Personal communication, 1955.







FLORIDA GEOLOGICAL SURVEY-BULLETIN FORTY


water hampered work in the lower reaches of the river. When-
ever 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 ex-
plored.
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 hy-
droxide solution. This process released and cleaned the shells for
additional study. Once dried, the mollusks were identified and coun-
ted. 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 identi-
fied and counted. These totals were then multiplied by four or
eight and added to the count of the larger specimens. Later, per-
centages were calculated for all species.
The faunas were also analyzed stratigraphically and paleo-
ecologically. 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 deduc-
ing 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 rela-
tively thin; the thickness of most formations may be measured
in tens of feet, although the Hawthorn formation is several hun-
dred feet thick. Most of the region is covered by a thin veneer of
late Pleistocene sands, marls, and muck, and several marine ter-
races have been recognized.
The beds of the southern part of the Peninsula are little de-
formed. 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 Flor-
ida plateau suggests deformation. The eastern portion of the
plateau extends under the water of the Atlantic only a short dis-
tance, whereas the western half extends approximately 100 miles
into the Gulf of Mexico. As a result southern Florida actually rep-
resents only the southeastern portion of the plateau. Shallow de-
pressions, 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 ap-
plication of Neogene formational terminology in Florida. How-
ever, 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 forma-
tions, 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 fm.
oolite Is. fm. Penholoway fm.
Wicomico fm.


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


Caloosahatchee
marl


Miami Key Largo
oolite Is.


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) q No record



(Sahelian?)
B


I


I. 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 High-
way 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 Choctaw-
hatchee 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) in-
cluded the Buckingham limestone of Mansfield in the Tamiami for-
mation, 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


TV,
c;* -


.**


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







FLORIDA GEOLOGICAL SURVEY-BULLETIN FORTY


Monroe counties. He described its lithology mainly dirty
white to gray, rather hard, porous, non-oolitic limestone with in-
clusions of clear quartz." The fauna, as reported by Mansfield, in-
cluded 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 re-
ferred 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 in-
clude 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 for-
mation (Parker and Cooke, 1944, p. 62-63) were referred to the
Fort Thompson formation by Hoy and Schroeder (1952, p. 283-
286).

Lithologic Character

The Tamiami formation is represented by several faces 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 forma-
tion 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 mol-
lusks Ostrea disparilis, Chione ulocyma, and Turritella pontoni,
which F. Stearns MacNeil (1951, personal communication) states
S. 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 com-
mon in the Ecphora facies of the Choctawhatchee in West Florida.

Thickness

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









FLORIDA GEOLOGICAL SURVEY-BULLETIN FORTY


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
















z
-' .. :~tieT i














0 I




z






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.
~~~ ~ ~ r ,. ,'

:s -1 : 1.,a
.., ; i r. I..; ..I

i 1 .ir


..-.,,,. '; 'g :...




Figur 61
Unonomalecntctbtwente aloahthe mr ad h Tmim frmtonc
exposed1 aln liao re nCalteC t. Pone igrmrstebs
ofi Caooahce mar.







FLORIDA GEOLOGICAL SURVEY-BULLETIN FORTY


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. 161-
170) 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) north-
ward 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 identi-
fied 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 cal-
careous and very hard, so as closely to approach the nature of
true limestone. Most layers are moderately to abundantly fossil-
iferous, 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 relation-
ships. 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 de-
posited. The typical Caloosahatchee beds were deposited in a shal-
low sea. The Tamiami formation seems to have been eroded and
well dissected by subaerial agents; consequently the Caloosa-
hatchee deposits are thickest where they fill the depressions and tend
to thin over high areas. At several localities along the Caloosa-
hatchee 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 Caloosa-
hatchee 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 ex-
tends 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







FLORIDA GEOLOGICAL SURVEY-BULLETIN FORTY


(fig. 2, p. 21) and, according to Cooke (1945, p. 221), the forma-
tion 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-Two-
Mile 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 sub-
surface 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 Caloosa-
hatchee 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 occur-
rence 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,
Area wagneriana, and Anadara rustic. 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 forma-
tion 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 con-
glomerate 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 ex-
pressed concerning their true chronological significance. Probably
the formation is Miocene, and there seems to be no convincing evi-
dence that it is a facies of the Caloosahatchee formation.
Cooke (1945, p. 231) considered the so-called Citronelle for-
mation of the lakes region of central Florida as a near-shore and
beach facies of the Caloosahatchee formation, but this view re-
mains to be proved.


2Personal communication, 1955.








FLORIDA GEOLOGICAL SURVEY-BULLETIN FORTY


YOUNGER PLEISTOCENE DEPOSITS
GENERAL DISCUSSION
Late Pleistocene deposits constitute a thin but nearly continu-
ous 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 brackish-
water 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 Plio-
cene. Dall (1887, p. 143) also referred to the upper marine rocks
as post-Pliocene, but regarded the "Planorbis beds" below as Plio-
cene in age.
The most typical fossil in the marine layers is Chione cancel-
lata, 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. Augus-
tine, 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 Caloosa-
hatchee 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 south-
eastern 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. 74-
75) included in the Pamlico formation all marine Plesitocene de-
posits 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.








FLORIDA GEOLOGICAL SURVEY-BULLETIN FORTY


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 approxi-
mately 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 Ham-
mock 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 Thomp-
son formation, Pamlico formation, Lake Flirt marl, and in a few
places to the Tamiami formation. A diagram showing the gener-
alized 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 relation-
ship 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 in-
cluded.
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 sec-
tions were measured and studied, and the descriptions of some of









LATE NEOGENE STRATA OF SOUTHERN FLORIDA 41



VERTICAL SCALE
,I's- FORMATIONS

e '. O
0 0

QUARTZ SAND -J
I :s 2



L COFFEE MILL
1 HAMMOCK MARL 2
U U
U,' U ___
14- a.
UPPER O
13 FRESH-WATER MARL
L _______________ I.
12 Ctr- CHLAMYS BED

II LOWER O
FRESH-WATER MARL L

W lo-

9 S, .
Sn UPPER SHELL BED

_j
n rt "__
a
7 4l

Si i I BEE BRANCH MEMBER W
'U
SI | I o
^.-^ ^---------------- -
---- BRACKISH-WATER MARL <
4 --_ _ _
4

3 OYSTER BIOSTROME 0
-j
2 0
CYRTOPLEURA
SCOSTATA ZONE

LOWER MARINE MARL


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 approxi-
mately 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).












HENRY COUNTY


FORT THOMPSOI
VERTEBRATE
LOCALITY


HENDRY COUNTY


20
C)
N
N'~


SCALE


Figure 9


GEOLOGY OF THE AREA

ADJACENT TO THE

CALOOSAHATCHEE RIVER

PART A















































Figure 10


















OLD LOCK
NO. 3


GLADES COUNTY


GLADES COUNTY


CALOOSAHATCHEE
BED DIPS BELOW
SURFACE A


HENDRY COUNTY


1 MILE


SCALE


Figure 11


GEOLOGY OF THE AREA

ADJACENT TO THE

CALOOSAHATCHEE RIVER

PART C














'GLADES COUNTY


GLADES COUNTY


SCALE


Figure 12


-GEOLOGY OF THE AREA

ADJACENT TO THE

CALOOSAHATCHEE RIVER


PART 0







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 Caloosa-
hatchee 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 rela-
tively 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.








FLORIDA GEOLOGICAL SURVEY-BULLETIN FORTY


marls. Fossils are abundant in some beds but are usually pre-
served 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 (Meuschen) Philippi
Chione ulocyma Dall
Chione latilirata athlete 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 (approxi-
mately 1.75 miles downstream from La Belle bridge). The exposed







LATE NEOGENE STRATA OF SOUTHERN FLORIDA


beds consist of a gray arenaceous clay from which the author col-
lected 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 in-
terruption. 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 Caloosa-
hatchee 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 tran-
sitional 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







FLORIDA GEOLOGICAL SURVEY-BULLETIN FORTY


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 Caloosa-
hatchee sea, while others rose close enough to the surface to be
affected by wave action and to be swept relatively clear of sedi-
ments 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 re-
sulted 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 Caloosa-
hatchee 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. How-
ever, 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 else-
where, are usually thicker, and are laterally more extensive. The
exposed thickness rarely exceeds five feet and commonly is less, al-
though 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 faces 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 pock-
marks are common and conspicuous. In many areas the holes have









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TABLE 2
INSOLUBLE RESIDUE ANALYSES OF SEVERAL LOWER CALOOSA-
HATCHEE 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
A16 .._.. ..-------.--- ...- -------- 54.0 43.0 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
A5-3 ..-........-----------------.-- 72.5 23.0 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 abun-
dant. 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 cal-
careous 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 car-
bonate, 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 appear-
ance. 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 (ap-
proximately 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 in-
clude a Turritella facies near station A23, a shallow-water high-
salinity 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 bur-
rows 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 cal-
cium carbonate and 50.5 percent of plastic material, of which
47.5 percent exceeds 1/64 mm. in diameter. The sand and silt con-
sists 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 sta-
tion A23 is nearly identical to that of the sediment just described
but that of the Vermicularia zone at Ortona is much more cal-
careous.

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 bio-
strome 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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a p


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 up-
ward 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; typi-
cally 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, how-
ever. 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 gastro-
pod 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 drab-
gray.
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 per-
cent by weight of calcium carbonate and the plastic 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 fresh-
water origin. One such unit was observed in the lower Caloosa-
hatchee 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 sub-
merged ledge of hard dense gray calcareous marl about 10 inches
thick. It is very fossiliferous and includes mostly small fresh-
water snails such as "Fontigens" and several species of the land
snail, Polygyra, including P. sayi peninsula 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 con-
sists 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 addi-
tional fresh-water beds of Caloosahatchee age in the outcrop area
or at least in subsurface. Such beds cannot arbitrarily be con-
sidered 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 Caloosa-
hatchee River in Hendry County near its confluence with the tribu-
tary called Bee Branch.
With one or two exceptions it conformably overlies the lower
Caloosahatchee beds described above, and is in turn conformably








LATE NEOGENE STRATA OF SOUTHERN FLORIDA


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 un-
conformable.
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 sta-
tions A22 and A26 the thickness is two to four feet.
Two principal faces of the Bee Branch member and many
minor variations of each have been recognized. One faces 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.








60 FLORIDA GEOLOGICAL SURVEY-BULLETIN FORTY

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 solu-
tion holes that are filled with matrix from overlying beds. Com-
monly small pockets of softer marly material occur within the
bed but are not related to solution holes above. The exposed ver-
tical surfaces are pockmarked where these small patches of marl
have been flushed out at flood stage. Most of the weathered sur-
faces 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 plastic 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 lo-
cality in being much softer, less consolidated, more arenaceous, and
more distinctly concretionary. Generally it does not form promi-
nent ledges. The concretions contained in it are hard, dense cal-
careous 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
A26 ---------------------- 85.0 11.0 4.0
A33 _---- -- ---------------------.------ 93.0 4.5 2.5
A34 ....... ---------------------- 91.5 6.5 3.0
A35 -___.----------.......------- 85.0 10.0 5.0
A36 --------- -------------------- 73.5 15.5 11.0
A39 (11 mile west of Ft. Denaud) --.. 82.0 15.0 3.0








LATE NEOGENE STRATA OF SOUTHERN FLORIDA


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 concre-
tionary 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 mem-
ber 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 typi-
cal 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.








62 FLORIDA GEOLOGICAL SURVEY-BULLETIN FORTY


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, fresh-
water 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 Caloosa-
hatchee 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 great-
est 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 elastic residue greater than 1/64 mm. of 30 percent
by weight and a fine plastic 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, sub-
angular 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 CALOOSA-
HATCHEE 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, ostra-
codes, 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 re-
working 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 Caloosa-
hatchee River by a thin succession of alternating fresh-water and
marine marls that bear an unconformable relationship to the








LATE NEOGENE STRATA OF SOUTHERN FLORIDA


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 be-
tween La Belle and Ortona Locks (fig. 19, p. 65) where these de-
posits 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 forma-
tion has been entirely removed by erosion.
Discussion of the Fort Thompson formation has been divided
into sections devoted respectively to fresh-water and marine de-
posits. The marine sediments are subdivided into the Chlamys bed
and Coffee Mill Hammock marl. The fresh-water deposits are inter-
bedded 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 cor-
rectly 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 characteris-
tically 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 uncon-
formably on the Bee Branch member of the Caloosahatchee forma-
tion but locally it rests on the upper Caloosahatchee shell bed (near
station A17).
At the Fort Thompson type locality and elsewhere between sta-
tions 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 typi-
cally 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







LAKE FLIRT MARL


7 I. FRESH-WATER SANDY MARL

PAMLICO FORMATION

lI QUARTZ SAND
---


LEGEND
FORT THOMPSON FORMATION CALOOSAHATCHEE MARL

' COFFEE MILL HAMMOCK MARL UPPER SHELL BED

It 1 FRESH- WATER LIMESTONE E BEE BRANCH LIMESTONE
' iFRESH- WATER MARL OYSTER BIOSTROME

SCHLAMYS BED CYRTOPLEURA COSTATA ZONE
S1.5 MILES 'I


W









Li L/ '. j' '.
V..





U U.,%) V ~


L; o L) r L.


A19 A18


A17 A16


A15 A14 All
STATIONS


12 r-








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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 inter-
section 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 fresh-
water 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, subangu-
lar to well rounded quartz grains, which are surprisingly similar
to most of the sand in marine beds of the Caloosahatchee forma-
tion.
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 be-
tween the sand of the upper and lower beds is apparent. The in-
soluble 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 lime-
stone 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 sedi-
ment 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.










LATE NEOGENE STRATA OF SOUTHERN FLORIDA


anI -.
r.


V*(
*


a


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 ex-
posed (fig. 20, p. 67). They alternate vertically with beds of fresh-
water 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 case-
hardened 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 gen-
erally weathers gray. It is a poorly consolidated mixture of sand
and mollusk shells. The insoluble residue of a sample is 46.0 per-
cent by weight. The coarse fraction of the residue comprises 87.0
percent of the total. The sand consists of subangular to sub-
rounded 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 Yar-
mouthian 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 Thomp-
son 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 Caloosa-
hatchee 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 sub-
surface, over a relatively wide area.

Coffee Mill Hammock Marl

The uppermost marine marl, that is the thickest and most ex-
tensive 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 resi-
due of a sample is 79.5 percent by weight, of which about 97 per-
cent 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 de-
termined to be 58.0 percent by weight. The coarse fraction com-
prises 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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A -


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 in-
cluded 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, Char-
lotte, 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 con-
sidered 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 Caloosa-
hatchee River, Shell Creek, and Alligator Creek, the Pamlico for-
mation 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, Caloosa-
hatchee, 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 unconsoli-
dated 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 in-
vertebrate 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 simi-
lar 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 fresh-
water 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 de-
scribed 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 low-
water 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 Thompson-
Ft. 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 Cyrto-
pleura 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 Caloosa-
hatchee 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 Caloosa-
hatchee 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 athlete 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 dif-
ference 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 Ham-
mock 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 cal-
careous 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 gastro-
pod, now known as V. recta Olsson and Harbison. The concentra-
tion 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 up-
ward 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 Area 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.








78 FLORIDA GEOLOGICAL SURVEY-BULLETIN FORTY






















"14






























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








LATE NEOGENE STRATA OF SOUTHERN FLORIDA


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.







80 FLORIDA GEOLOGICAL SURVEY-BULLETIN FORTY

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 per-
sistent 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 ex-
tension 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 wagner-
iana, 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 lime-
stone (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








82 FLORIDA GEOLOGICAL SURVEY-BULLETIN FORTY

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 Caloosa-
hatchee 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 faces of the fresh-water lime-
stone 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 dis-
cussed 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 inter-
vals 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 sec-
tions 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 recog-
nized 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













W EE




S2 3 7 9 10 12 13 14 16 17 18 Sl S S3





40
PAMLICO FORMATION -
5 0 / '. FORT THOMPSON FORMATION


20 MARL :

SCALOOSAHATCHEE
30













e H D f i SeMARL
H Klei, 1954.
TAMIAMI FORMATION

3 7 10 12 13 14 16 17 18 S1 S S3
0












BASE OF THE PAMLICO FORMATION BASE OF TH FORT THOMPSON FORMATION
20 MARL n












BASE OF THE CALOOSAHATCHEE MARL
30 *

80-
BASE OF THE PAMLICO FORMATION BASE OF THE FORT THOMPSON FORMATION







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 sub-
surface 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 assem-
blage 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 dis-
cussed 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 abun-
dant, 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 as-
sociated 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 mol-
lusks was derived from papers by Bartsch (1936), Dall (1889-
1903), 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 scapho-
pods, 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 Puri.
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 percent-
age 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 assem-
blage, 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 pres-
ence 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 Caloosa-
hatchee marl and the Fort Thompson formations. These suggest
varied environmental conditions in close proximity and also fre-
quent changes in environmental conditions within any given area.
Because of these many variations, detailed stratigraphic and paleo-
ecological studies are made difficult but none the less intriguing.
This study reveals that almost all of the deposits of the Caloosa-
hatchee 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 conti-
nental 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 environ-
ment. Many of the remaining Caloosahatchee beds seem to have
developed in protected inlets, bays, and lagoons. Some beds con-
tain 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 near-
by sea where they became mixed with the shells of marine inverte-
brates.
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 inter-
glacial 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 con-
centration 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 costata lives
only in high salinity bays and in shallow water immediately off-
shore; usually in mud or sandy mud bottom4 Its minimum tempera-
ture 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 reduc-
tion 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 Acleocino conoliculato
SOlivella. mulk
M oarginelo pordolis
Nassorius bidentatus

I T ctonatico pusillo
Colyptroe centralis


FACIES OF THE CYRTOPLEURA
COSTATA ZONE








LATE NEOGENE STRATA OF SOUTHERN FLORIDA


KEY TO GASTROPOD SPECIES
100 FACIES OF THE CYRTOPLEURA C. pidulo fo,rc.t
COSTATA ZONE Bi podgri
90 Bilfiu- podo.rdnum
STun rritell. subomula o
E]i Tritella apicolis




50
70urrill e nu
60 Nerino sphaerico







10
0
A35 A17 AZ3
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, shallow-
water, near-shore environment. Typical high-salinity forms and
deep-water species are absent or represented by only a few speci-
mens. Fresh-water species such as Helisoma conanti, H. disstoni,
and Fontigens plan 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 consoli-
dated, 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 Caloosa-
hatchee 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









FLORIDA GEOLOGICAL SURVEY-BULLETIN FORTY


KEY TO PELECYPOD SPECIES
Nucula proxima

Nuculana acuto

| | Glycymeris arata floridana

Mytilopsis lamellate

SCardita tridentata

Phacoides multilineatus

SPhcoides woccomowensis
80----------------


70- ------- ------ -- .


60
50 ------------ -- -






Z3 -




10

0 -- -
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
STrigoniocardia willcoxi

Chione cancellata

Parastarte triquetra

LZ Tellina suberis

SMulinia sapotilla

E-3 Rangia nasuta

i Caryocorbula leonensis

Varicorbula caloosae


80-

70 -.. .

60 ---


50- .




i 30 -


20--- ---




S -- 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 costata faunizone. Percentage figures are
based on the total pelecypod fauna for each station.








94 FLORIDA GEOLOGICAL SURVEY-BULLETIN FORTY

(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 Turri-
tella facies (fig. 34, p. 94). Judging from the percentage of high-
salinity 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 shoal-
water 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 indi-
viduals 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 gener-
ally 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 environ-
ment 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, there-
fore 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 Turri-
tella 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








FLORIDA GEOLOGICAL SURVEY-BULLETIN FORTY


oL .. mm mmm ^---------n-F-a--
I5 3 5
LOWER MARL CYRTOPLEURA COSTATA OYSTER BIOSTROME UPPER SHELL BED
ZONE
CALOOSAHATCHEE BEDS (STATION 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 sug-
gestive 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. Deep-
water 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
EO TFi j..j. Ph-efd-

'""F~ -----Q









LATE NEOGENE STRATA OF SOUTHERN FLORIDA 97



KEY TO GASTROPOD SPECIES

IAdaocine conticujloe Colyperno cnfrois


M obrginllo pardas ^ BittiumS pdgrinu
I saNoorius Wbdentatus I Turitello subomuloat


| I |Tur ill. pero.l nua.
90
90 -


so ------- -- -- -- --------------------------- ---









0 ---- ------------- ----------- -----
W 0 ...- ......-.....







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







FLORIDA GEOLOGICAL SURVEY-BULLETIN FORTY


the best developed and laterally most extensive. Since it is doubt-
ful that the oysters anywhere formed a ridge or mound-like forma-
tion rising noticeably above the surrounding substrate, the term
reef is not employed to describe the bed. The most accurate desig-
nation 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. Physi-
cal factors conducive to oyster growth seemingly were not uni-
form throughout the entire extent of the biostrome. At some
localities the unit contains mostly large naturally oriented valves of
Crassostrea virginica (Linn)). 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 com-
position reflect the variety of physical and biological factors exist-
ing 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 an-
other 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 be-
come 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 rea-
son 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 com-
mon at most stations studied. In places this species even exceeds
Crassostrea virginica in number of specimens. The ecologic sig-
nificance 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 com-
munities establish themselves and flourish within a salinity range
of 10 to 30 parts per thousand." He pointed out that the popu-
lation 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 flats 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 settle 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 ex-
tensive 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 charac-
terized by a scarcity of species and individuals of macro-
organisms."
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, Crepidulac 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: