Neogene stratigraphy and geologic history of the Apalachicola Embayment, Florida ( FGS: Bulletin 58)

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Material Information

Title:
Neogene stratigraphy and geologic history of the Apalachicola Embayment, Florida ( FGS: Bulletin 58)
Series Title:
Bulletin State of Florida, Bureau of Geology
Physical Description:
146 p. : ill., maps ; 23 cm.
Language:
English
Creator:
Schmidt, Walter, 1950-
Florida -- Dept. of Natural Resources
Florida -- Division of Resource Management
Florida -- Bureau of Geology
Publisher:
State of Florida, Dept. of Natural Resources, Division of Resource Management, Bureau of Geology
Place of Publication:
Tallahassee, Fla.
Publication Date:
Copyright Date:
1984

Subjects

Subjects / Keywords:
Geology, Stratigraphic -- Neogene   ( lcsh )
Apalachicola Embayment (Florida)   ( lcsh )
Genre:
bibliography   ( marcgt )
government publication (state, provincial, terriorial, dependent)   ( marcgt )
non-fiction   ( marcgt )

Notes

Bibliography:
Includes bibliographical references (p. 73-80).
Statement of Responsibility:
by Walter Schmidt.

Record Information

Source Institution:
University of Florida
Holding Location:
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:
ltqf - AAA1658
ltuf - AEH5063
alephbibnum - 000877378
oclc - 12626834
System ID:
UF00000238:00001


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Table of Contents
    Copyright
        Copyright
    Front Cover
        Front Cover 1
        Front Cover 2
    Letter of transmittal
        Page i
        Page ii
    Table of Contents
        Page iii
        Page iv
    List of Figures
        Page v
        Page vi
    Abstract
        Page vii
        Page viii
    Acknowledgement
        Page ix
    Main
        Page 1
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    Appendix
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Full Text

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TU NU .f
LIB. OF
FLA. HIST.


STATE OF FLORIDA
DEPARTMENT OF NATURAL RESOURCES
Elton J. Gissendanner, Executive Director

DIVISION OF RESOURCE MANAGEMENT
Charles W. Hendry, Jr., Director


BUREAU
Steve R.


OF GEOLOGY
Windham, Chief


BULLETIN NO. 58

NEOGENE STRATIGRAPHY AND GEOLOGIC HISTORY OF THE
APALACHICOLA EMBAYMENT, FLORIDA

by
Walter Schmidt













Published for the
FLORIDA GEOLOGICAL SURVEY

TALLAHASSEE
1984




r -,"


DEPARTMENT
OF
NATURAL RESOURCES



BOB GRAHAM
Governor


GEORGE FIRESTONE
Secretary of State


BILL GUNTER
Treasurer


RALPH D. TURLINGTON
Commissioner of Education


JIM SMITH
Attorney General


GERALD A. LEWIS
Comptroller

DOYLE CONNER
Commissioner of Agriculture


ELTON J. GISSENDANNER
Executive Director






LETTER OF TRANSMITTAL


Bureau of Geology
Tallahassee, Florida
December 31, 1984


Governor Bob Graham, Chairman
Florida Department of Natural Resources
Tallahassee, Florida 32301

Dear Governor Graham:

The Bureau of Geology, Division of Resource Management, Depart-
ment of Natural Resources is publishing as Bulletin 58 "Neogene
Stratigraphy and Geologic History of the Apalachicola Embayment,
Florida," prepared by Walter Schmidt with our Geologic Investigations
Section.

The panhandle of Florida will be experiencing rapid population growth
in the future. This report fulfills a need for information on the stratigraphy of
the area, which is the foundation for responsible growth in community
planning. Groundwater resource investigations, landfill siting, mineral
deposits mapping, and foundation design are but a few of the disciplines
rnuiring geologic data such as this.

In addition, interpretations of the geologic history of the area are
presented. This information will be useful to geologic researchers
throughout the State to aid in a better understanding of the prehistoric
development of Florida.

Respectfully yours,

Steve R. Windham, Chief
Bureau of Geology

















































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

Tallahassee
1984













TABLE OF CONTENTS

Page
Ab tr ................... ......................... .... ....II.. 1-.-.- .... .. .-,1I..... .'4. ix
Acknowled gements..... I ...- 4. .................... ...........I- ,4... -..I I.. .... ......... 4.J.J II xi
Introductlon..................... ..................... .......... .................................................... 1 i
Previous Investigations................................. ...-.... ........ ..... .. 3
ta Collection an Mr e of Anas... ............................. --6
G geologic Str e .re........................... ....... . I ................. I -- 1 ................. I .. ----- 7
ratigraphy .................. .. ................ ......... .. .........10........ 10
Intr oducton............................................................................... .................................. 10
Late Paleogene Units...... I ......... .. ............... .. ...................10
Oca G roup.... .. .... ................... ........... ....................................................... 10
Marianna and Suwannee Limestones................................................12
Neoge n FormationsL .... ...... .. ............................................. ................... 4.1. 3
Chattahoochee and St Marks Formaions............................................. 13
N0menclatural History.............. ............ ......................13
Lthology.......4................-..........-..'.4-... 13
Thickness and Disribution....... ................... .............4....14
Paleontology and Age.......................... I ..... r. 4-- -1 i......................... .I 4 19.15
Bruce Greek Lime one. .... ... .... ................................................................... 15
Nomenclalural History ........449..........'49.9.4 -.....-15
Nomeho n atura H.... ........ ........................................... ....... 1

Overlying and Underlying Units..... ................................................... .........16
Th meknes and Dlstrbutk. n....... ......................................... ..... .................17
Paleontology and Age................... .4.......4-... ............... .....................20
intracoastal Formationr ..................... .. ....................................................... 20
Norendalura Httoryl ......... .. l .. ......................................... ........... 20
I IUtht y .r......... ............9... ............ ........ ....... .... ....................... 21
Four-Mle Village Member........ .....................................21
Overlying and Underlying Units.......... .........4.................................. 21
Thickness and Distribulion ............ ......................................... .............. 24
Paleontology and Age................................ ...... ..... .......... ..... .......24
Chiproa Formation ..........................................................4-9....... 29
Nomenclatural History... ..................... .... .................... .29
L.thology ............... .... .... .............. ................ 30
Overlying and Underlying Unt ................. ........ ................... ......................31
Thickness and Ditribution........ .. ........................................... ................ .....31
Paleontology and Age........................................................... 32
Jackson Bluff Formation...................................................................- 32
Nomen u...c1 .l Htory.............................................. ...............33

Overlying and Underlying Units . .......................... ........... ...........-...... 33
Thickness and Distribution..... .. ........ ......... .................................. .... ......... 35
Paleontology and Age........................ .............. ...............................37
PlBestoone Sedl imenrts ......................4..4..................... .3.......7.................. -----.... 37
Undfferentiated Sands and Clays.. ...................................... 37
Nomenclatural HIstory..... ................... 44.................... -.. ............37
Lithology.... ..... ................ ..... ...........38
Overlying and Underlying Units ......................................................3.3
Thickness and Diatribution.. ............................................... ................................- 39
Paleontology and Age .............. .............. .......... ........ .........................39




I



Adjacent Stratlgraphic Units ........ ........... ...................... .... ...... ..... ......... .. .... ....... 48
Chickasawhay Llmestone .............4....................................................... ....................48
St. M arks Form ation...... ... ....................................................................................... 48
Pensaco la C lay................................................................................................... ......4
M iocene Coarse C lastics................................................ .. ........ ... ... ... ..........................49
H awthorn Form ation................... .............................................. ...............................49
Paeoenvironmental Analysis .......................................... ................................................ 49
Form national Observations.......................................................................................... 49
Ocala Group Limestones........................... ................................. ..........49
Marianna and Suwannee Limestones...... .................................................50
Chattahoochee and St. Marks Formations.........................................................51
Bruce Creek Limestone..................................d... 4...... ... ............................51
Clayey Dolosilt.............. ......................................... .. ....... ....................................... ..52
Intracoastal Formation................... ......................................... ....................52
C hipola Form ation............................ ...... .. ...................................... ........... 553
Jackson Bluff Formation..................... ................ .... ... ......................55
Massive Clays and Clayey Sands ................. .. .............. ... 56
Graded Quartz Sands............. .......... ........ ...... .............................. ............... 56
Quartz Sand Residuum and Soil Zone .......... ........ ........ ..........56
Discussion ... ........... ................. ................... ........... .... ..... ...... 56
Geologic History of the Apalachlcola Embaymenl Region..........................................59
Preliminary Structural Mapping .............................................................. ........... 59
Literature Review ..... ... .. 1 ...................... .................... ............ ... ..................... .. ... 59
Sequential Trends from the pre-Jurassic to the Recent.,,,...........,.................. 62
Structural HIstory of the Apalachlcola Embayment...............................................67
Tertiary Structural Movements.................. .................... .... ................. .........68
Conclusions................... .............. ........... . .. .... .................................. .. ............. ...70
R eferences... ..................... ........ ....... ............................... .......... .... ....... ............. 73
Appendices
Appendix I. Diatoms From The Pleistocene Clay Beds.................................................81
A ppendix II. X-ray Data Table ........................................................... ....... ............. ....... 9
Appendix III. Columnar Sections of Core Holes.............................................. ..... 105








LIST OF FIGURES


Page
Area of Study....... ................ ............................................ ............................. .. 4
Location of Stratlgraphlc Core Tests In the Vcinrty of the Study Area ....................... 5
G eologic Structures.................. ....... ....... .... ....................... .................................... ...8
Generalized North-South Geologic Cross Section ................................................ 11
Dolosilt. Algal Bed, Bruce Creek Limestone from Core W-14890, and Algal Bed,
Bruce Creek Limestone from Core W-14844 .......................... .......... ..... 18
Top of Bruce Creek Limestone ..4....4.. .. ......... ..........4.9 ..... .................... .... ....... 19
Intrecoastal Formaton from Core W-8873, and Four-Mile Village Member of
Intracoastal Formation.............. .......................................................... ...............22
Thickness of Intracoastal Formation.................................................. ........ .. ... 25
Top of Intracoastal Formation ...... .................................................. ............ 26
Top of Jackson Bluff Formation type sediments+. .......... .........................34
Bedded quartz sands from Core W-14925, and Jackson Bluff Formation Shell Bed
from Core W -14993.................................................................................. ....... 36
Location of Geologic Cross Sections..........................................................................41
Geologic Cross Section A-A'.......... ................ ................................ .............42
Geologic Cross Section B-B'...... ...... ... ..........................43
Geologic Cross Section C-C' and D-D'............ ............ ..........................44 44
Geologic Cross Section E-E' and F-F'.......................................... .... ......... .......... 45
Geologic Cross Section (-G' and H-H'... .................... ................................ 46
Geologic Cross Section 1-I' and J-J'..................... ............ ............... ....... 47
Generalized Paleoenvlronmental Trend .............. ............................... 54
Generalized Paleogeographic Trend, Eocene-Pleistocene.....................................58
Axis of "Low Area"................................................................................................. 61
Sequential Plots of the Axis of the Embayment........ ......... .............4.. ..... ........ .. 64
Simplified Structural History of the Apalachicola Embayment................................... 69
Well Cuttings and Cores From Which Diatoms Were Found in the Pleistocene Clay
Beds ....4 4..4.4.........4.4..... I-... ......................................... ........................................... 83


Number of Cores and Cuttings Sampled for X-ray Analyses........97
W-6599, Jackson Bluff Core.... .......... ..... ................... ..... 108


W-6611, Rock Bluff #1 Core. ................. .......... ............... 109
W-6901, Alum Bluff #1 Core .......... .............................. 110
W -7457, W all #1 Core.................. ......... ......................... 111
W-7524, CH-2 Core................................ .... ........ ....... 112
W-7574, St. George Island #1 Core....................................113
W-7616, Alum Bluff #2 Core ................ .... ..................... 114
W-8355, Ryan #1 Core.......................... ........115
W-8477, Fenton Jones #1 Core................... ...........,..... 116
W-8478, Bayvlew #1 Core,.................... ................... 117
W -8587, Mack #1 Core.................. ... ............ ............... ......... 118
W*8591. Price #1 Core............ .................................... 119
W-8592, Bruce #1 Core............................... ...............I..1.. 20
W-8865, Coffeen #1 Core.............. . ..... .. ... ............ 121
W-8873, Intracoastal #1 Core ......... ...... ....... ...... .............4-. 122
W -8876, Sam #1 Core........................... .. ...... -...............l L 123
W-8877, Lalonde #1 Core ............ ................. ..................... 124
W-11270, Ten Mile Creek #1 Core........ ..............................125
W-12051, St. Joe #1 Core ....... ...... ......... ........... .......... 126
W-13617, Schmldl #12 Core.............. ........................ ..127
W-13622, Schmidt #13 Core..................................... ........., 128
W-13965, Mejetle #1 Core.... ......................................1 29
W-14077, Williams Bay #1 Core............. ................................. 130
W-14101, Otter Creek #1 Core........ .............. .....................131
W-14106, Warmouth Pond #1 Core .................................,. 132


25 Location and "W"
26 Columnar Section,


Columnar
Columnar
Columnar
Columnar
Columnar
Columnar
Columnar
Columnar
Columnar
Columnar
Columnar
Columnar
Columnar
Columnar
Columnar
Columnar
Columnar
Columnar
Columnar
Columnar
Columnar
Columnar
Columnar
Columnar


Section,
Section,
Section,
Section,
Section,
Section,
section,
Section,
Section,
Section,
Section,
Section,
Section,
Section,
Sectldn,
Section,
Section,
Section,
Section,
Section,
Section.
Section,
Section,
Section,




-",9


Columnar
Columnar
Columnar
Columnar
Columnar
Columnar
Columnar
Columnar
Columnar
Columnar
Columnar
Columnar
Columnar
Columnar


Section,
Section,
Section,
Section,
Section,
Section,
Section,
Section,
Section,
Section,
Section,
Section,
Section,
Section,


W-14125,
W-14704,
W-14719,
W-14746,
W-14781,
W-14799,
W-14844,
W-14876,
W-14890,
W-14906,
W-14925,


Bee Bay #1 Core.................................................... 133
Luke Ford Creek #1 Core.......................................... 134
Indian Swamp #1 Core............. ,........ ...................135
Depot Creek #1 Core............. ................... ......... 136
Tates Hell #1 Core............................. .......... 137
States Hell #2 Core.............................................. 138
Tates Hell #3 Core....................................... ........ 139
Crooked River #1 Core.......................... ............ 140
Tates Hell #4 Core ................................................. 141
New River #1 Core...................................................142
Dead End #1 Core....................................................... 143


W-14969, Gregory MIIl Creek #1 Core........................... 144
W-14993, Jackson Camp #1 Core ,,.......................................145
W-14996, Queens Bay #1 Core ................. ............................. 146


LIST OF TABLES

Metric conversion factors for terms used in this report ..... .... .................................... 3
Partial list of Planktonic Foraminlfera Identified from the Intracoaslal Formation......... 27
Partial list of Calcareous Nannofossils identified from the Intracoastal Formation.......28
Partial list of Benthic Foraminifera Identified from the Intracoastal Formation.............29
Partial list of Diatoms Identified from the shallow clay beds within the undfferentiated
sands and clays unit. ....... ........................................................ .... ................ 40
Formation abbreviations from geologic cross sections A-A' to J-J..............................40
Names used to describe the structural "low" feature near the Big Bend of Florida.... 60


UST OF PLATES

Diatom s Plate 1 .......................................................................................................... 85
Diatom s Plate 2.................................................................... ........................................ 7
Diatom s Plate 3................ .................. ...... .... ................... .... ........... .......................
D iato m s Plate 4....... .............................................................. ........................................ 91
Diatoms Plate 5....................................................................................... ...............93
Diatom s Plate 6............. ............. ......... ... ...................................... ..............................95










ABSTRACT
Neogene units lie near the surface in the Florida panhandle in a narrow
band extending from 20 miles west of Tallahassee, Leon County, northwest
to Oak Grove in north-central Okaloosa County. These sediments are
primarily clayey, sandy (quartz), shell beds exposed along a number of
stream or river bluffs.
Downdip towards the Gulf of Mexico these units thicken and change in
lithologic character. Although subsurface units, these contemporaneous
Ilthologic packages can be defined and mapped throughout the region
using stratigraphic core tests, water-well cuttings, and geophysical well
logs. The Bruce Creek Limestone and Intracoastal Formation are two units,
predominantly subsurface, mapped from this area. It Is also noted that the
Chipola and Jackson Bluff formations are younger downdip in the
subsurface than where they are exposed updip. Pleistocene quartz sands,
gravels, and massive silty clay beds are mapped in Gulf, Franklin, and
southern Liberty counties. These units were deposited in brackish and
fluvial environments as the Apalachicola delta system advanced to the
south.
The Neogene and Pleistocene sequence of sediments thickens and
dips along a gently plunging axis that descends gulfward through central
Gulf County. This thickened sequence of sediments is called the
Apalachicola Embayment.
The lithologic and faunal characteristics of the formations, from the
Upper Eocene to the Pleistocene are, summarized. This information is then
used to suggest paleoenvironments for the various units. A generalized
paleoenvironmental sequence is postulated from the mid-Tertiary to
Recent.
Differing opinions on the nature and origin of the Apalachicola
Embayment have been expressed by numerous geologists. By incorporat-
ing interpretations from the Neogene (this paper) with sequential structural
contour maps from the Upper Cretaceous to the Lower Micoene
(unpublished maps by May and Schmidt, 1974), and Jurassic mapping by
Pontigo (1982), with the large volume of published literature on the area, a
geologic history has been synthesized.
The low feature (embayment) resulted from a graben which had its
origin in Triassic to Early Jurassic time. This graben slowly filled with
sediments until it ceased to exist as an embayment at the end of the Early
Cretaceous. From Early Cretaceous through Early Eocene a "low" or
depression occurred east of the Jurassic axis. During Early through latest
Eocene the axis of this "low" shifted to the northwest until the Oligocene,
when it was repositioned once again over the Jurassic axis. This Late
Cretaceous-Tertiary feature is considered to be due to slow deposition in a
current-swept strait similar to the present Florida Straits. During the Early







and Middle Miocene, the strait apparently began to fill in as carbonates from
the Florida platform on the southeast infringed on the shallow channel, and
clastics from the northwest spilled over onto the shallow shelf. From the
Late Miocene to Pleistocene the strait completely filled and the prograding
coastal plain migrated over the area. The feature does not currently exist as
a topographic low since the Apalachicola River Delta has prograded over
the area.









ACKNOWLEDGEMENTS


I would like to express my sincere gratitude to several people who
offered helpful suggestions and assistance throughout the course of this
research.
Assistance In microfauna identification and interpretation was gra-
ciously provided by Ronald W. Hoenstine and Bill Miller, who discussed the
diatom data; and Sharon Bolling, Murlene Clark, and Richard Hummell,
who identified planktonic and benthic foraminifera.
X-ray diffractograms were run by Jon Arthur, Sharon Bolling, and Adel
Dabous. Drafting and photographic reductions were prepared by Pauline
Hurst, Jim Jones, and Simmie Murphy. A special thanks goes to Julia Jones
and Josie Smith for typing and assisting with the manuscript.
Thanks go to several colleagues who offered numerous stimulating
discussions on stratigraphic correlations and paleogeography. They
include Paul Huddlestun, Muriel Hunter, Tom Kwader, John Meeder, Phil
Pontigo, Tom Scott, Richard Strom, Sam Upchurch, and Jeff Wagner. I
would also like to express my gratitude to Ramil Wright for his valuable
criticism and advice during the writing of the manuscript. Bill Burnett, Ken
Osmond, Bill Parker, and Sherwood Wise, all with the Florida State
University, also reviewed the text and offered helpful suggestions.
I also want to extend my appreciation to C, W. Hendry, Jr., of the
Florida Department of Natural Resources, Division of Resource Manage-
ment, who supported and encouraged the completion of this project.










NEOGENE STRATIGRAPHY AND GEOLOGIC HISTORY OF THE
APALACHICOLA EMBAYMENT, FLORIDA
By
Water Schmldt

INTRODUCTION
The geology of the Florida panhandle has been as thoroughly studied
by geologists as any comparable area in the state of Florida. No less than
eight of its counties have been singled out for study by the Florida Bureau of
Geology in its Bulletin Series. Five of the eight (Jefferson, Leon, Jackson,
Holmes, and Washington) are located where the older formations approach
the land surface (updip) and have significant surface relief and available
rock outcrops on which to base studies. Two of the counties (Santa Rosa
and Escambia) are located in the vicinity of active oil fields, and as a result, a
large amount of subsurface data in the form of well cuttings and geophysical
well logs is available. The most recently completed county study (Bay) was
prepared as a direct result of the first stages of research towards the
present regional study.
The Miocene and Pliocene deposits that crop out in the panhandle of
Florida have been studied since the late 1800's. They have frequently been
described and have received the greatest attention from paleontologists
who have been attracted to their well-preserved mollusk and foraminiferal
assemblages.
Bums (1889) and Langdon (1889) were the first to record descriptions
of the shell beds along the Chipola and Apalachicola rivers, respectively.
Since these initial reports, other authors have described or named these
units primarily based on their fossil assemblages. Stratigraphic correla-
tions, however, have been questionable due to poor, sporadic exposures
and lithologic heterogeneity of the various deposits. For a history of the
nomenclatural changes leading up to modern usage see Schmidt and Clark
(1980).
The Miocene-Pliocene deposits are exposed in a narrow band which
extends from 20 miles west of Tallahassee, Leon County, Florida,
west-northwest to DeFuniak Springs, Walton County, Florida, a distance of
about 90 miles. South of these exposures, toward the Gulf of Mexico,
stratigraphic interpretations have been based on relatively few sets of well
cuttings. It is no surprise that the coastal stratigraphy has never been well
understood since very few reliable data points exist on which correlations
may be based. Indeed, lithologic complexity is such that stratigraphic
problems of the outcropping units to the north remain unsolved. This
thickened sedimentary sequence downdip of the exposed region occurs
mainly in the subsurface and is known as the Apalachicola Embayment.
Many geologists in the past, when assigning formation names from





BUREAU OF GEOLOGY


well cuttings in the Apatachicola Embayment, would use the nearby outcrop
formational descriptions. This seemed logical since the subsurface unit
penetrated by the well would probably be exposed updip to the north. Thus,
formation names from exposed units in the north were applied to the
downdip rocks even though it was clear that these subsurface sediments
were dissimilar from the described, exposed material.
In the late-1960's, the Florida Bureau of Geology undertook a
stratigraphic coring program in Walton County. Twenty-five cores were
drilled from the surface down to the Oligocene or Eocene age sediments.
The cores were well-spaced throughout the county and extended from the
Florida-Alabama border to the coastal margin. The wide area extent of core
control offered a unique opportunity to describe and map the lithologic units
throughout the area of near-surface exposure as well as downdip where the
Neogene units are entirely subsurface. Hendry (1972) and Huddlestun
(1976a) utilized these data to map formation and chronostratrtigraphic units
throughout Walton County.
It became readily apparent to them that the downdip Neogene
sequence of sediments is an expanded section, thicker than the
contemporaneous updip units. These deposits also are more calcareous,
trending towards sandy (quartz) limestones and sandy (quartz) biocal-
carenites, whereas the updip units are dominantly argillaceous, sandy
(quartz), shell beds.This calcareous wedge of sediments contains, along
with common macrofossils, a prolific and diverse microfauna, dominated by
benthic and planktonic foraminifera and calcareous nannofossils.
Subsequent to the Walton County study, the downdip Neogene
stratigraphic mapping program was extended eastward into Bay County
(Schmidt and Clark, 1980) and westward into Okaloosa County (Clark and
Schmidt, 1982). Although relying primarily on water-well cuttings, the
stratigraphic sequence was definable and mappable, both east-west and
north-south (updip/downdip).
Recently, the Florida Bureau of Geology drilled 20 stratigraphic core
tests in Bay, Calhoun, Gulf, Franklin, and Liberty counties. These additional
data enables this regional mapping project to be extended to the eastern
terminus of these Neogene units.
This combined core coverage (66 cores in all, in or near the
Apalachicola Embayment), along with hundreds of sets of water-well
cuttings and geophysical well logs, has allowed the author to make regional
correlations and interpretations regarding the Neogene and Quatemary
sediments which fill in the Apalachicola Embayment (Figs. 1 and 2).

METRIC CONVERSION FACTORS
In order to prevent much awkward duplication of parenthetical
conversion of units in the text of reports, the Florida Bureau of Geology has
adopted the practice of inserting a tabular listing of conversion factors, For
the use of those readers who may prefer to use metric units rather than the
customary U.S. units, the conversion factors for terms used in this report
are given in Table 1.





BULLETIN NO. 58


TABLE 1,-Metric conversion factors for terms used In this report.
MULTIPLY BY TO OBTAIN
acres 0.4047 hectares
acres 4047.0 sq. meters
cubic yards 0.7646 cu. meters
feet 0.3048 meters
inches 2,540 centimeters
inches 0.0254 meters
miles 1.609 kilometers
sq. miles 2.590 sq. kilometers
PREVIOUS INVESTIGATIONS
Much of the previously applied nomenclature from the Miocene and
Pliocene of the Florida panhandle is confusing and commonly misleading.
Published stratigraphic names have included: deposits, beds, members,
formations, groups, marls, biofacies, magnafacies, parvafacies, zones, and
stages. This confusing situation was largely due to inadequate knowledge
of the stratigraphic and paleoenvironmental framework of the deposits.
Much of the confusion resulted from the fact that there was no detailed
mapping of these sediments, Most comprehensive descriptions of "facies"
were confined to the sediments in the immediate vicinity of the various type
localities, In addition to the lack of detailed studies, the inadvisable
procedure of using the term faces was used to refer to divisions which are in
actuality faunizones.
The nomenclatural history of these exposed deposits is too lengthy to
include here and the reader is directed to Schmidt and Clark (1980) for the
history of the Alum Bluff Stage (Middle Miocene) and the history of the
Choctawhatchee Stage (Upper Miocene).
Studies dealing with the shallow stratigraphy (within about 600 feet of
the surface) in the Apalachicola Embayment area are far less abundant and
will be summarized below.
Sellards and Gunter (1918) published two geologic reports, one on the
area between the Apalachicola and Ochlockonee rivers and a second on
the area between the Choctawhatchee and Apalachicola rivers. Their
reports described various geologic sections and they attempted to make
some downdip interpretations.
Cole (1938) reported on the stratigraphy and micropaleontology of a
well in Gulf County at Port St. Joe. His report identified species of
foraminifera from various depths from the well cuttings, and his
stratigraphic names conformed to prior usage from updip exposed
sections. The next year two Masters Theses were completed under Dr.
Cole's supervision. The first (Bemhagen, 1939) discussed the stratigraphy
and micropaleontology of a well in Calhoun County (W-7 of the Florida
Bureau of Geology's collection); and the second (Hobbs, 1939) discussed
the stratigraphy and micropaleontology of two wells in Bay County (W-140,
W-151) and one well in Franklin County (W-228). They also identified
species of foraminifera.


















































Figure 1. Area of Study.


_ _L _ _L __ __C _













16 a214


g1et9


r~\-~


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IT"RA-TIOAPIC COPE T~BTS m
t1 Vcltrr OF nT Tlry ASIA


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" v v w4 u / -." [- 4 4 7 1 -
Il s 04S _; I t



imust
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0146- so z
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F' -








Figure 2. Location of Stratigraphic Core
Tests in the Vicinity of the Study Area. m


- a I'( aI





BUREAU OF GEOLOGY


Schnable and Goodell (1968) published an excellent report on the
Pleistocene and Recent Stratigraphy, Evolution, and Development of the
Apalachicola Coast, Florida. Although their report emphasizes coastal
morphology, they do include some shallow geologic cross sections
(generally within 100 feet of the surface) and a "surface geology" map.
Huddlestun (1976a) compared the updip and downdip sections In
Walton County, which is located on the western-most fringe of the
Apalachicola Embayment. Cameron and Mory (1977) reported on the
mineral resources of Bradwell Bay, a small wilderness area in Wakulla
County on the eastern edge of the embayment. Also in 1977, Trapp
discussed an exploratory water well from St. George Island in Franklin
County. Schmidt (1978,1979) published two environmental geology maps
that cover the area on a 1:250,000 scale.
Schmidt and Clark (1980) published a geologic bulletin on Bay County,
Florida, located on the western side of the embayment. Patterson, Schmidt
and Crandell (1982) wrote on the geology and mineral resource potential of
a part of the Apalachicola National Forest in southern Liberty County.
Other geologic reports on the area include heavy mineral identification
of coastal and river deposits and sand-size analyses of present coastal
features and surficial deposits inland. One study by Tanner (1966)
commented on the Tertiary history of the Apalachicola River Region, as
inferred from physiographic and terrace evidence.
DATA COLLECTION AND MODE OF ANALYSIS
Because of the gentle dip (less than 0.5 degree) of the strata and the
thin veneer of Pleistocene terrace deposits throughout the coastal regions
of the Apalachicola Embayment, there are very few locations where rock
units crop out at the surface. This regional study is, therefore, based mainly
on subsurface information consisting of cuttings from water and oil test
wells, stratigraphic core tests, drillers logs, and down-hole geophysical
information (primarily gamma logs).
Surface exposures are usually found along the northern limits of the
Neogene sediments associated with river bluffs or stream cuts. The
Ochlockonee, Apalachicola, Chipola, Choctawhatchee, and Shoal rivers,
along with many of their tributaries, have cut numerous steep bluffs into
these clayey, sandy, shell beds. It is these surface exposures that have
been extensively described and cited in the geologic literature. Most of
these locations, in addition to other exposures such as road-cuts and
borrow pits, have been visited and sampled so that they can be tied-in with
the downdip subsurface data.
Water and oil test well cuttings are stored by the Florida Bureau of
Geology in Tallahassee, Florida. Hundreds of sets of cuttings from the
study area are available. Most have samples at 10-foot intervals; however,
irregular intervals are not uncommon. The cuttings were examined with a
binocular microscope, and such parameters as major rock type, color,
estimated porosity, grain type, grain size, induration, cement type,
sedimentary structures, accessory minerals, and fossils were described.




j





BULLETIN NO. 58


Stratigraphic core tests have been drilled throughout the area by the
Florida Bureau of Geology. Sixty-six cores have been recovered in the
vicinity of the embayment area, 26 of which are within the area of Neogene
sediment thickening. All cores were drilled with a Failing 1500 truck-
mounted core rig and are generally from 200 to 500-feet deep. Cores are
1% inches in diameter. Recovery varied from 100 percent to approximately
50 percent in the cavernous limestones. All but seven of the cores in Bay,
Calhoun, Gulf, Liberty, and Franklin counties were drilled for this regional
study. Drilling site locations were selected after assessing existing geologic
data along with stratigraphic trends.
Geophysical well logs were run in most of the core holes by the Florida
Bureau of Geology and/or the Northwest Florida Water Management
District. Other geophysical logs are on file at both these agencies from
scattered water wells located throughout the district. Although individual
wells or core holes may have had a complete suite of logs run on them
(including natural gamma, neutron, gamma-gamma, electric, caliper, and
others), the one which seemed most useful for stratigraphic correlation was
the natural gamma log. This is also the most commonly available well log.
The natural gamma logs respond to natural gamma radiation (U, Th, K)
present within the sediments. This is often associated with the mineral
components present within the various rock units. The specific reason for
the various activity levels present within the Neogene sequence of rocks in
the Florida panhandle has been investigated by Kwader (1982). These logs
proved useful in estimating the depth and thickness of the lithologic units
especially in areas where cuttings or core control was sparse.
Information from cores was relied on most heavily in stratigraphic
interpretations because cores offer a higher level of confidence for depth
correlation. Upon completion of the lithologic descriptions of the cores and
cuttings, formation contacts were picked and the lithologic package that
made up each unit was defined. In addition, the cores were sampled for
mineralogical and micropaleontological Information. Samples were col-
lected from the cores from major lithologic units. An x-ray diffraction study
was carried out on these samples to estimate the dominant minerals
present. Samples were also collected for smear slide analysis for
microfossil content. Calcareous nannofossils and diatoms were found to be
present in different formational units. This information, along with
foraminiferal data from Walton, Bay, and Gulf counties, was used to aid
both in the estimation of the time of deposition of the formations and in
constructing biostratigraphic correlations.
Thin sections were prepared from selected samples to aid in rock
descriptions and to assist in the assessment of depositional environment.
GEOLOGIC STRUCTURE
The Apalachicola Embayment (Pressler, 1947) is the dominant
geologic structure influencing the sediments in the central part of the Florida
panhandle. The shallow deposits are gently down-warped about an axis
that plunges to the south-southwest (Fig. 3).



















GULF OF MEXICO


APALACHICOLA
'M8EMBAYMENT


SEDIMENTARY


BASIN


LI


EOCENE


OUTCROPS


m OLIGOCENE OUTCROPS


FLORIDA
PENINSULA


SEDIME
PROVI


Figure 3. Geologic Structures.


Ur


4-


--Y ~ - ~' -- -- ----- ---- --- - -





BULLETIN NO. 58


A summary of the literature about this feature is given by Patterson and
Herrick (1971) and May (1977). The feature was first named the
Chattahoochee Embayment (Johnson, 1891), but has been referred to
most commonly as the Apalachicola Embayment and will be recognized as
such here. This embayment, which Is a relatively shallow basin between the
Ocala and Chattahoochee highs, is narrowest in the northeast and opens to
the south and southwest.
It has been estimated that the deeper parts of the embayment, together
with adjacent portions of the Gulf Basin, cover an area of approximately
30,000 square miles (Pressler, 1947). The magnitude of the basin appears
to increase with depth, which would indicate a long continued development.
However, the geologic history of the embayment appears to be a
complicated sequence of events.
The near-surface Quaternary and Neogene deposits are gently
downwarped, whereas the older Paleogene and Mesozoic rocks are
downwarped to a progressively greater extent. Correspondingly, the older
strata are thicker (Murray, 1961). As the embayment deepens toward the
Gulf, the sedimentary fill attains a thickness of nearly 15,000 feet. The
sediments, which range in age from Triassic to Recent (Applegate et a.,
1978; Schmidt and Clark, 1980) are very similar to those of southern
Mississippi and Alabama, except that the Tertiary formations become
progressively more calcareous to the east.
The sedimentary fill rests on metamorphic rocks of probable Paleozoic
Age (Applegate et a/., 1978). On the top of the Paleozoics, the Mesozoic
deposits reach a thickness of over 10,000 feet, white the Cenozoic
sediments are generally less than 3,000 feet in thickness.
To the north and northwest of this embayment is a positive structural
feature called the Chattahoochee Anticline (Veach, 1911; Puri and Vemon,
1964), a broad flexure mapped in the tri-state area of Alabama, Florida, and
Georgia. This "high" brings Oligocene and Eocene rocks to the surface,
while the younger units either pinch out or are truncated against
the high. The feature is an elongated anticline that trends northeast-
southwest, crests in Jackson County, and plunges to the southwest. It is this
southern extension of the Chattahoochee Anticline that separates the
Apalachicola Embayment from the more regionally extensive Gulf of
Mexico Sedimentary Basin to the west. This transition zone between two
negative features occurs in the Okaloosa County area (Clark and Schmidt,
1982) and corresponds to the western limit of the coastal Neogene
carbonates.
To the east of the Apalachicola Embayment is another relatively high
feature, the Ocala Arch. As the shallow sediments trend from the central
part of the embayment towards the Ocala Arch, they again truncate at the
surface as the older formations approach the more shallow depths. This
truncation, which marks the eastern extent of the shallow Neogene units in
the embayment, occurs in western Wakulla, eastern Liberty, and eastern
Franklin counties.





BUREAU OF GEOLOGY


The southern extent of the embayment is not studied here due to the
lack of off-shore data. However, it is postulated to continue to dip and
thicken gradually to the south-southwest.

STRATIGRAPHY

INTRODUCTION
The downdip, predominantly subsurface stratigraphy of the Neogene
sediments in the Apalachicola Embayment has never been well
understood. As the rock units trend into the deeper parts of the embayment
away from the two structural highs (the Ocala and Chattahoochee) their
lithologic character changes. This downdip relationship was first recog-
nized in Walton County by Hendry (1972) and Huddleston (1976a) and
subsequently described and mapped in Bay (Schmidt and Clark, 1980) and
Okaloosa counties (Clark and Schmidt, 1982), the latter of which is located
in the western transition zone between the Gulf of Mexico Basin
sedimentary infill and the more local Apalachicola Embayment sediments.
The present study maps and defines these Neogene units from
Okaloosa County on the west to Wakulla and Leon counties on the east.
The Paleogene formations down to the Upper Eocene Ocala Group
limestones are also identified in some cores and cuttings. These
correlations appear on geologic cross sections shown later as Figures
13-18, although these older units were not mapped or described in detail
because less data is available from these deeper horizons. A generalized,
north-south, geologic cross section is shown in Figure 4, to demonstrate the
updip-downdip stratigraphic relationships.
LATE PALEOGENE UNITS

Ocala Group
Upper Eocene (Jackson Stage) strata in Florida were divided by Purl
(1957), on the basis of a detailed, biostratigraphic study, into three
formations comprising the Ocala Group; they are, in ascending order, the
Inglis, the Williston, and the Crystal River. The literature pertaining to the
nomenclature of the Ocala Group leading up to the current usage is
extensive and has been adequately reviewed in previous publications; it will
not be repeated here. Summaries are contained in Vernon (1942), Cooke
(1945), Puri (1957), and Puri and Vernon (1964).
In the Florida panhandle, the Ocala crops out along the Alabama state
line (Figures 3 and 4) in Jackson and Holmes counties. This unit is brought
to the surface as a result of the Chattahoochee Anticline in which older,
deeper formations approach the ground surface. The Ocala in this area has
been described both from surface exposures (Vernon, 1942; Moore, 1955;
Schmidt and Coe, 1978) and downdip in core holes (Schmidt and Clark,
1980; Clark and Schmidt, 1982). In general, only two lithologic faces can be
recognized. A lower facies consists of greenish-gray, glauconitic, sandy




-I


10





NORTH
CHATTAHOOCHEE


ROCK
BLUFF


SOUTH


ALUM
BLUFF


ESTIFFANULGA
BLUFF


APALACHICOLA


GENERALIZED NORTH-SOUTH


SUWANNEEV z
0
0
tD
ri


Figure 4. Generalized North-South Geologic Cross Section.


mo mm mp r - - -__ - .1





BUREAU OF GEOLOGY


limestone and contains a lower Jackson fauna. The upper and more typical
faces Is a light-yellow to white, massive, porous, often silicified, abundantly
microfossillferous limestone (packed biomicrite or packstone to wackes-
tone).
Very few wells reach the top of the Ocala Group and even fewer
penetrate the entire thickness of the Ocala. As a result only a small number
of the northern cores or cuttings described for this study included any
Ocala. No formations or lithofacies could be ascertained for the unit. The
group was identified as a light orange to white packstone to wackestone
with high porosity In which both micrite and sparry calcite are common,
along with small amounts of glauconite, quartz sand, and abundant fossils.
Dominant fossils include foraminifera, mollusks, echinoids, bryozoans, and
corals.
Contours drawn on top of the Ocala Group in the central part of the
Florida Panhandle (Toulmin, 1952; Chen, 1965; Weaver and Beck, 1977;
and Gelbaum and Howell, 1979) show a distinct deflection northeastward
implying that the embayment feature existed atthe close of the Late Eocene
Series or that subsequent downwarping has occurred. Information
presented later will argue for the former.
MARIANNA AND SUWANNEE LIMESTONES
The Oligocene Series (Vicksburg Stage) in the Florida Panhandle
consists of the Chickasawhay, the Marianna, and Suwannee limestones
and the Bucatunna Clay. The Marianna and Suwannee limestones are
exposed in Jackson, Holmes, Washington, and Walton counties, (Vernon,
1942; Moore, 1955; Reves, 1961; Yon and Hendry, 1969; Schmidt and
Coe, 1978). Although the Chickasawhay Limestone was named for
exposures of limestone along the Chickasawhay River in Mississippi,
Marsh (1966) extended this limestone unit into the Florida Panhandle; it is
not however, exposed at the surface.
In addition to these three limestone formations Cooke and Mossom
(1929), and Puri and Vemon (1964) recognized an additional Oligocene
formation, the Byram Formation. Later authors, however, (Moore, 1955;
Vernon, 1942; and Schmidt and Coe, 1978) included the Byram with the
younger Suwannee Limestone because of its lithologic similarity. Marsh
(1966) did map a Bucatunna Clay Member of the Byram Formation in the
subsurface of Escambia and Santa Rosa counties in western Florida. Also
Clark and Schmidt (1982) were able to identify this clay member in a limited
number of well cuttings in western Okaloosa County. As is the case with the
older Ocala Group, the Oligocene Series limestones are only encountered
in the subsurface within the present study area. These deeper horizons are
penetrated rarely and only by updip (more northerly) wells.
The Bucatunna Clay and the Chickasawhay Lmestone do not occur
within the bounds of this study. They occur on the western flank of the
Chattahoochee Anticline and are, therefore, part of the eastern edge of the
sediment wedge thickening westward into the Gulf of Mexico Sedimentary
Basin (Figure 3). The Marianna and Suwannee limestones are often the



j





BULLETIN NO. 58


deepest formations penetrated in the northern limits of this study and their
lithology is briefly summarized here.
MARIANNA LIMESTONE-From the few sets of well cuttings that
contain the Marianna, it can be characterized as a light gray, massive,
chalky, fossiliferous, moderately to well-Indurated biomicrite or wackes-
tone. Commonly present are large foraminifera of the genera Lepidocy-
clina. Minor accessory minerals include glauconite, quartz sand, and pyrite.
One core (W-6901, Liberty County) also appeared to contain some
dolomite and a trace of montmorillonite, based on x-ray diffraction analysis.
SUWANNEE LIMESTONE-The Suwannee is present as the basal
unit penetrated in many cores and water wells. It consists of light gray to
yellow-gray, well indurated, chalky, sucrosic, fossiliferous biomicrite to
biosparite, or a packstone to wackestone. The limestone is often
dolomitized and contains highly altered, recrystallized fossils. X-ray
analysis identified calcite, dolomite, quartz sand, and a minor amount of
clay.
The top of the Suwannee, long considered the top of the Oligocene
Series (more recently the Oligocene-Miocene boundary has been placed
within the overlying Chattahoochee Formation by Poag, 1972; and
Huddlestun, 1976a), dips to the south-southwest towards the city of
Apalachicola (Toulmin, 1952; Weaver and Beck, 1977). The Suwannee
approaches the surface to the east, as the older formations onlap onto the
Ocala Arch, and to the north and northwest as the older formations again
onlap the Chattahoochee Anticline.
Contours drawn on top of the Suwannee Limestone show a northeast
deflection similar to the trend of the underlying Ocala Group (May and
Schmidt, 1974). This implies that throughout the Oligocene a southwesterly
opening embayment may have existed similar to that which is postulated for
the Eocene. This sequence of events will be expanded on in a later section.

NEOGENE FORMATIONS
Chattahoochee and St. Marks Formations
NOMENCLATURAL HISTORY-The Chattahoochee and St. Marks
formations are two limestone units of the Lower Miocene (Tampa Stage) as
defined by Purl (1953). The first to use the term Chattahoochee Formation,
however, was Dall and Stanley-Brown (1894).
It was not until Puri and Vemon (1964) published their comprehensive
Summary of the Geology of Florida that the Chattahoochee and St. Marks
formations were established. They included type localities for both
formations but did not attempt to map their area extent. A more complete
nomenclatural history of the Tampa Stage in Florida is given in Schmidt and
Clark (1960, pp. 33-35).
LITHOLOGY-Uthologic units that correspond to previous descrip-
tions of both of these formations were encountered in many cores and
cuttings throughout the study area. The St. Marks occurs along the south
and eastern parts of the embayment and the Chattahoochee occurs along
the north and western parts of the study area. Because the underlying


13






BUREAU OF GEOLOGY


Suwannee Limestone and the overlying Bruce Creek Limestone are also
both carbonates that have undergone a considerable amount of secondary
alterations due primarily to groundwater, these four formations occasionally
cannot be separated. This lithologic trend is shown later on the geologic
cross sections (Figures 13-18).
The Chattahoochee Formation can be summarized as follows: It is
generally a very pale orange to very light gray, moderately to well-indurat-
ed, dolomitic, calcilutltic, mudstone to fossiliferous micrite. Quartz sand is
often present, as are minor amounts of phosphorite. Some zones can be
described as a fine-grained, sucrosic dolomite.
This wide range of lithotypes has resulted in the Chattahoochee/
Suwannee formations and the Chattahoochee/St. Marks formations
sometimes being lumped into one undifferentiated unit (see Appendix III).
The St. Marks is a very pale orange to light gray to white, moderately to
well-indurated, fossiliferous, dolomitic, calcarenitic limestone, or a packed
biomicrite to a wackestone. Quartz sand is common, as are occasional
greenish, clay blebs. Fossils are common, generally as molds and casts.
The St. Marks is often Indistinguishable from the overlying, younger Bruce
Creek Limestone. These two formations are probably laterally equivalent in
the deeper parts of the embayment (Figure 15).
THICKNESS AND DISTRIBUTION-The type locality of the St. Marks
Formation is located about two miles south of Crawfordville in Wakulla
County, along the eastern edge of the Neogene embayment as defined In
this study.
The St. Marks is exposed throughout eastern Wakulla County and Is
generally associated with karst features such as sinks and springs. The
western-most exposures are common along the Sopchoppy River where
rock outcrops are found intermittently along the banks of the southern half
of the river. (This limestone was recently informally named the Sopchoppy
Limestone by Huddlestun and Hunter, 1980).
The thickness of the St. Marks ranges from zero east of Wakulla
County, where it rests on karst formed on the Suwannee Limestone, to over
200 feet near the axis of the Apalachicola Embayment in the Gulf County
area (Cameron and Mory, 1977). It dips towards the southwest from the
outcrop area. Elevations range from 10-20 feet above sea level in Wakulla
County to deeper than 600 feet below sea level in Gulf County.
Near the axis of the embayment the limestone of the St. Marks
becomes indistinguishable from the younger Bruce Creek Limestone that
has been described on the western flanks of the embayment. For this
reason, a structural map of the St. Marks could not be constructed.
The type locality of the Chattahoochee Formation is at the Jim
Woodruff Dam on the Apalachicola River. Here the Chattahoochee has an
elevation of 169 feet (Tampa Formation of Moore, 1955). To the south the
unit dips into the embayment and drops below present sea level in
Washington, Calhoun, and Liberty counties (Moore, 1955; Schmidt and
Coe, 1978). To the north the unit pinches out as the older Suwannee


14





BULLETIN NO. 58


Limestone nears the land surface approaching the axis of the Chattahoo-
chee Anticline (Figure 4).
Downdip in Bay, Gulf, and southern Liberty counties the Chattahoo-
chee Formation becomes locally indistinguishable from the St. Marks and
Bruce Creek limestones (Schmidt and Clark, 1980). As a result, a structural
map could not be constructed for the Chattahoochee.
PALEONTOLOGY AND AGE-Since Purl and Vernon (1964) defined
the Tampa Stage, Poag (1972) and Huddlestun (1976 a, b) raised the
Oligocene-Miocene boundary into the Chattahoochee Formation based on
planktonic foraminifera. The St. Marks, however, is still considered Lower
Miocene.
The fossils described from the Tampa Stage sediments (Chattahoo-
chee and St. Marks formations) are mostly found within the St. Marks; the
Chattahoochee has relatively few fossil remains. Mansfield (1937)
described the mollusks and Puri (1953) described the foraminifera and
ostracoda.

Bruce Creek Limestone
NOMENCLATURAL HISTORY-The Bruce Creek Limestone was
named by Huddlestun (1976a). He included it in a group of three subsurface
formations that he proposed from the southern half of Walton County. The
three formations, of which the Bruce Creek Limestone was the basal
formation, comprised his Coastal Group. Huddlestun explained that this
group was a new name for Alum Bluff equivalent carbonate units that
underlie the coastal area of Walton County and vicinity.
Huddlestun's (1976a) description of the Coastal Group states there are
two lithologic types within the group. The first type is usually a
well-indurated, coarsely calcarenitic, light colored, poorly microfossiliferous
limestone (the Bruce Creek Limestone); and the second type is a younger
(and therefore overlying), unconsolidated to moderately indurated,
extremely microfossiliferous, less coarsely calcarenitic, argillaceous,
glauconitic, and phosphatic limestone (his St. Joe and ntracoastal
limestones).
Lithologies from the Bruce Creek Limestone have been referred to
previously as a limestone faces of the Chipola Formation (Gardner, 1926;
Cooke and Mossom, 1929). Uimestones of similar description have been
reported by Sellards and Gunter (1918); Cooke and Mossom (1929), and
Vernon (1942) in southwestern Washington County near the Choctawhat-
chee River and in Walton County in White Creek.
The type locality of the Bruce Creek Limestone, as informally
designated by Huddlestun (1976a), is several hundred feet downstream
from the county road bridge over Bruce Creek in T1 N, R18W, north-half of
section 2, Walton County, Florida. At this location, one-to-two feet of pale
bluish-green, unconsolidated, soft, slightly argillaceous, sandy, slightly
macrofossiliferous limestone is exposed. It is primarily a subsurface unit
with the type locality being the only known exposure.


15





BUREAU OF GEOLOGY


More recently, the Bruce Creek Limestone has been mapped in the
subsurface in Bay County east of the type area (Schmidt and Clark, 1980)
and in Okaloosa County west of the type area (Clark and Schmidt, 1982).
Further mapping of this formation (Schmidt et al., 1982; and Boiling, 1982)
has shown the unit to be a wedge-shaped deposit and that its eastern extent
coincides with the eastem boundary of the Neogene Apalachicola
Embayment. As stated in a prior section, the Ilthology of the Bruce Creek
becomes Indistinguishable from that of the St. Marks Formation on the
eastern flank of the embayment.
LITHOLOGY-The Bruce Creek Limestone has proven to be an easily
recognizable stratigraphic unit and a useful marker. Samples from the type
outcrop on Bruce Creek In Walton County can be correlated lithologically
and stratigraphlcally with well cuttings and cores from areas east and west
of the type area.
Towards the west in Okaloosa County and vicinity, the Bruce Creek
Limestone is a white to light gray, moderately indurated, calcarenitlc
limestone. It ranges from a wackestone to a packstone or a sparse to
packed biomicrite. The Bruce Creek contains planktonic and benthic
foraminifera, echinoid fragments, ostracods, and mollusks. Fossils are
generally preserved as molds which can be observed from cores
throughout the unit. Common accessory minerals include quartz sand,
pyrite, phosphorite, mica, clay, and glauconite. Quartz sand ranges from
one to 20 percent with higher values coinciding with the northern limits of
the formation. Other accessory minerals occur in quantities less than one
percent. The Bruce Creek becomes dolomitic towards the south and west,
From the type area eastward towards the Apalachicola Embayment,
the Bruce Creek is a white to light yellow-gray, moderately indurated,
calcarenitic limestone. The Bruce Creek is dominated by macrofossll
molds; but microfossils are also present, including planktonic and benthic
foraminifera, ostracods, bryozoans, and calcareous nannofossils. Acces-
sory minerals are about the same in the west with the addition of some
heavy minerals. The limestone seems to become less indurated towards
the east, although In the area of Gulf County the unit is often highly
indurated and dolomitic (often sucrosic).
X-ray analyses of selected core samples showed the Bruce Creek to
be predominantly calcite with a trace of montmorillonite in the Walton
County area. To the east in Bay, Calhoun, Gulf, Liberty, and Franklin
counties, calcite is still dominant; however, dolomite, quartz and
montmorillonite are also common. Palygorskite and aragonite were also
present in minor amounts (see Appendix II). It should be noted here that
many accessory minerals observed under the microscope are not recorded
by the x-ray diffractometer because they occur in small amounts (less than
one percent). For this reason both the observed accessory minerals and the
x-ray results will be discussed.
OVERLYING AND UNDERLYING UNITS-The Bruce Creek Lime-
stone overlies the Chickasawhay Limestone near the western limit of the
unit in Okaloosa and Santa Rosa counties (Clark and Schmidt, 1982). In


16





BULLETIN NO. 58


Walton, Bay, Calhoun, and Gulf counties it overlies the Chattahoochee
Limestone or a Chattahoochee/Suwannee undifferentiated unit. In Liberty
and Franklin counties, the St. Marks Formation underlies the Bruce Creek,
although the Bruce Creek and St. Marks become difficult to distinguish from
each other east of the Apalachicola River.
In general, the Chickasawhay and Suwannee Limestone are well
indurated, sucrosic dolomites, commonly grayish-orange in color, whereas
the Bruce Creek is a white to gray, calcarenitic limestone and is much less
dolomitized. Quartz sand is rare in the Chickasawhay and Suwannee and
common in the Bruce Creek.
In central Okaloosa County, the Bruce Creek occurs as a tongue
extending northward from the coastal area into the sediments of the Alum
Bluff Group. The Bruce Creek, therefore, overlies and underlies this unit.
The Alum Bluff Group consists of quartz sands, clayey sands, and mollusk
shell beds.
The undifferentiated Alum Bluff Group overlies the Bruce Creek
Limestone in the northwestern comer of the study area in Santa Rosa,
Okaloosa, and Walton counties. The Intracoastal Formation overlies the
Bruce Creek throughout most of the embayment area. The Intracoastal is
easily distinguished from the Bruce Creek by the olive-green, poorly
indurated, foraminiferal, blocalcarenitic nature of the Intracoastal when
compared to the white to very pale orange, well to moderately indurated,
granular limestone of the Bruce Creek. The Intracoastal Formation also
contains greater quantities of quartz sand, phosphorite, and clay than does
the Bruce Creek.
In the central part of the Apalachicola Embayment, the basal part of the
Intracoastal consists of a massive, clayey, dolosilt (Figure 5, core 1). This
bed will be discussed with the Intracoastal Formation in a later section.
THICKNESS AND DISTRIBUTION-The Bruce Creek Limestone is a
wedge-shaped deposit that thins to the north and thickens to the south (see
geologic cross sections, Figures 13-18). It pinches out in north-central
Okaloosa and Walton counties (Clark and Schmidt, 1982; and Huddlestun,
1976a), in northern Bay County (Schmidt and Clark, 1980), in central
Calhoun and Liberty counties, and western Wakulla County (Figure 6). The
regional trend throughout the study area is a west-northwest to east
southeast strike, although on the eastern flank of the embayment it curves
to a north-south strike (Figure 6).
The highest elevations occur in Walton County where it lies more than
50 feet above sea level. The top of the formation is deepest, just over 600
feet below sea level, in southwestern Okaloosa County. The regional dip for
the unit is to the south-southwest at a gentle dip of approximately 12 feet per
mile (0.13 degrees). The Bruce Creek Limestone has been estimated to be
up to 86-feet thick in coastal Walton County (Huddleston, 1976a) and about
300-feet thick towards the axis of the embayment in southwest Bay County
(Schmidt and Clark, 1980). Because very few wells penetrate the entire
thickness of the Bruce Creek along the coast, an isopach map of the
limestone was not constructed.


17






BUREAU OF GEOLOGY


Figure 5. CORE 1: Dolosilt, algal bed; Bruce Creek Limestone from Core
W-14890, 176 feet to 188 feet. CORE 2: Algal bed; Bruce Creek
Limestone from Core W-14844, 55 feet to approximately 74 feet.
(The top of each core is towards the bottom of the page.) Core
diameter is 14 inches.


18










































ci f l a rr 41 rp 5 k L


- A "














4 ,. .-
,I C
















Figure 6. Top of the Bruce Creek Limestone.


___


_ _




--.ql


20 BUREAU OF GEOLOGY

PALEONTOLOGY AND AGE-The Bruce Creek Limestone contains
numerous fossils, mostly preserved as molds and casts of mollusk shells. In
addition, both benthic and planktonic foraminifera are present, as are
ostracods, bryozoans, echinoids, and algal remains. Calcareous nanno-
fossils have been reported (Schmidt and Clark, 1980); however, due to the
crystalline and moderate to well-indurated nature of the rock, their
preservation is poor.
Huddlestun (1976a) dated the time of deposition of the Bruce Creek
Limestone from the Walton County area as Middle Miocene, based on
planktonic foraminifera identified from a clay bed within the unit. In Bay
County, the fossiliferous clay unit is absent; but on the basis of the presence
of some Globigerlnoides sp., Schmidt and Clark (1980) also concluded the
unit was Middle Miocene. The same age (Middle Miocene) was also
assigned to the Bruce Creek in Okaloosa County (Clark and Schmidt, 1982)
and in Gulf County (Boiling, 1982) based on planktonic foraminifera.
The upper part of the Bruce Creek (a zone that varies in thickness from
less than one foot to about 20 feet) consists of an algal-rich limestone,
where algal oncolites are common to abundant (Figure 5, core 2). This may
suggest a permanently submerged shoal environment (Logan, et a/., 1964)
or at least a shallowing of water near the end of Bruce Creek deposition.
The fauna preserved in the deeper limestone (deposited prior to the algal
zone) seems to suggest an offshore shallow marine environment
associated with a shallow carbonate platform. This may represent a slight
shallowing from the marine carbonates of the warm shallow seas that
existed prior to the Miocene in the Oligocene and Eocene epochs (Yon and
Hendry, 1972).
Intracoastal Formation
NONMENCLATURAL HISTORY-The Intracoastal Formation was
first described by Huddlestun (1976a, b). He used the name Intracoastal
Limestone to describe a "soft, sandy limestone of Pliocene age that
underlies the coastal area of western Florida." His discussion pertained
mostly to the Walton County area. Huddlestun placed the Intracoastal
Limestone in his "Coastal Group." (For a historical account of the Coastal
Group, see the history section on the Bruce Creek Limestone in this paper).
Huddlestun took the name Intracoastal from the Intracoastal Waterway
#1 core (W-8873), located in Walton County, Florida, in T3S, R18W,
northeast quarter of the southwest quarter of sec. 11 (Figure 40).
Schmidt and Clark (1980) expanded the definition of the Intracoastal
Limestone to include lithologically indistlnquishable sediments underlying
the unit described by Huddlestun and named that sediment package the
Intracoastal Formation. Their mapping resulted in correlations between
Bay County and Walton County. Later, Clark and Schmidt (1982) mapped
the formation westward into Okaloosa County and named the Four-Mile
Village Member from the middle of the formation. Their Four-Mile Village
Member equates to the informal phosphatic sand unit described by
Huddlestun (1976a) from Walton County.



A





BULLETIN NO. 58


Finally, Schmidt et a. (1982) reported that the Intracoastal Formation
was mappable eastward to eastern-most Franklin and Liberty counties and
northward to central Calhoun and Liberty counties.
LITHOLOGY-The Intracoastal Formation is an easily recognizable
stratigraphic unit, with well-defined upper and lower contacts. The
formation is predominantly a subsurface unit with only two known surface
exposures, one in northern Bay County and another in central Franklin
County. As a result, the formation descriptions and mapping have been
carried out using water well cuttings, stratigraphic core tests, and
geophysical well logs.
The Intracoastal lithology varies only slightly throughout its area
extent. It is a very sandy, highly microfossiliferous, poorly consolidated,
argillaceous, calcarenitic limestone (Schmidt and Clark, 1980). The
dominant lithologic components include microfossil material, quartz sand,
clay, micrite, and phosphorite. It contains minor amounts (generally one
percent or less) of glauconite, pyrite, heavy minerals, and mica. It can
generally be referred to as a poorly consolidated wackestone or a packed
biomicrite. Unwashed samples of the Intracoastal Formation are yellow-
gray when dry and dark olive-green when wet. Washed samples are buff to
speckled gray in color.
X-ray analyses of selected core samples did not yield clear-cut trends
in mineral constituents (Appendix II). As a result, a lithofacies plot yielded
no interpretable patterns. As a general rule, calcite and quartz (sand) are
the dominant minerals present. Also present, but in lesser amounts are
aragonite, dolomite, montmorillonite, kaolin, and phosphorite (apatite).
Mineral grains that make up less than a few percent of the sample often are
not represented on the x-ray diffractogram; however, their presence is
observed through microscopic examination of the core samples (Figure 7).
FOUR-MILE VILLAGE MEMBER-A phosphatic sand unit that is
present within the Intracoastal Formation was informally described by
Huddlestun (1976a). This phosphatic sand has been designated the
Four-Mile Village Member of the Intracoastal Formation by Clark and
Schmidt (1982). The Coffeen #1 core (W-8865) was used by them as the
best example of the unit. The Four-Mile Village Member is a pale
yellow-brown to yellow-gray, poorly consolidated, calcareous, slightly
argillaceous, microfossiliferous, glauconitic, phosphoritic, quartz sand or
sandstone. The member extends from near the Bay-Walton county line
westward along the coast into central Okaloosa County. To the north in
Okaloosa and Walton counties, it pinches out (or loses definition) rapidly
and is rarely found north of Choctawhatchee Bay. West of the Fort Walton
Beach area, the member loses definition as the Intracoastal Formation
thickens and dips toward the Gulf of Mexico Sedimentary Basin (see
geologic cross sections Figures 13 and 14).
OVERLYING AND UNDERLYING UNITS-The Intracoastal Forma-
tion overlies the Bruce Creek Limestone throughout most of its areal extent;
and in the Liberty County area, it overlies a sedimentary section which
resembles the Hawthorn Formation. Overlying the Intracoastal are





BUREAU OF GEOLOGY


Figure 7.


CORE 1: Intracoastal Formation from Core W-8873, 85 feet to 92
feet. CORE 2: Four-Mile Village Member, Intracoastal Formation,
from Core W-8873, approximately 177 feet to 185 feet. (The top
of each core is towards the top of the page). Core diameter is 1%
inches.


22





BULLETIN NO. 58


Pliocene-Recent sands: the undifferentiated Alum Bluff Group sediments
and the Jackson Bluff or the Chipola Formation, both molluscan shell beds.
The olive-gray, poorly consolidated, clayey, sandy foraminiferal
biocalcarenitic nature of the Intracoastal differs from the white to pale
orange, well-indurated, granular limestone of the Bruce Creek, The upper
part of the Bruce Creek often contains an algal zone with many oncolites
which provides a marked contrast with the Intracoastal. In the east and
central part of the Apalachicola Embayment, specifically in Liberty, Gulf,
and Franklin counties, there is a dark gray, massive, plastic, dolosilt
between the base of the Intracoastal Formation and the Bruce Creek
Limestone. X-ray analysis shows the dominant minerals present in this thin,
massive "clay" bed to be dolomite, quartz, montmorillonite, and
palygorskite. Smear slides of this unit yield no microfauna, but do reveal
abundant dolomite rhombs in the very fine sand to silt-size range. This
horizon may be an important unit for its hydrogeologic implications as well
as for its paleoecologic interpretation. Hydrologically, it may hinder vertical
groundwater migration and, therefore, create artesian conditions in the
underlying Bruce Creek Limestone. The fine grained, clayey nature of the
unit with incorporated unetched, noncemented, dolomite rhombs may imply
a tidal flat with the in situ dolomite obtaining its magnesium from eroding
Oligocene and Early Miocene dolomitic limestones exposed just north or
east of the area in Jackson, Leon, or Wakulla counties. How this may fit into
the sequence of events that led to the present stratigraphic sequence will be
discussed in a later section.
Overlying the Intracoastal near the northwestern extent of the
Formation in Walton and Okaloosa counties is the undifferentiated Alum
Bluff Group. This is a clayey, fine-grained quartz sand unit with some mica
and small amounts of fossil material. Further updip, it becomes more clayey
and fossil mollusks are common. Along the coast from central Bay County
westward, an unconsolidated, fine to coarse-grained, relatively clean,
quartz sand unit overlies the Intracoastal. Its lack of fossil material, clay and
carbonate easily distinguishes it from the Intracoastal. To the east in the
Apalachicola Embayment, either the Jackson Bluff Formation or Chipola
Formation cover the Intracoastal. Both of these formations are predomin-
antly argillaceous, sandy, mollusk beds. The Chipola is normally a
well-indurated, molluscan shell bed, whereas the Jackson Bluff is
non-indurated and poorly consolidated. Both of these formations, with their
abundant lithified or unlithified molluscan shell material contrast sharply
. ith the medium grained, mollusk-poor, Intracoastal Formation.
Occasionally, when core data or well cuttings are not available, natural
gamma logs can be used to approximate upper and lower contacts of the
Intracoastal Formation (see Appendix III). In general, the units overlying the
Intracoastal are lower in gamma activity and logs record very low counts per
second (cps). In addition, the Jackson Bluff shelly clay beds have low
activity, although there are more counts per second than in the overlying
quartz sands. Gamma activity in the Intracoastal commonly increases
going down hole, until near the base of the formation where peak counts


23





BUREAU OF GEOLOGY


over 200 cps are often recorded. Highs and low peaks in the gamma trace
are common between the base of the Intracoastal and the top of the Bruce
Creek Limestone. Going below the Intracoastal into the Bruce Creek,
activity drops off again, but it is not as consistently low as in the cleaner
sands near the surface. This is probably due to pore space and cavity infill of
higher-count material from above. As a general rule, the limestone units
deeper than the Intracoastal are lower than It In gamma activity.
THICKNESS AND DISTRIBUTION-The Intracoastal Formation is a
low-angle, wedge-shaped deposit (see Figures 8 and 9). Its greatest
thickness occurs in the southwest part of Okaloosa County where it is just
over 400-feet thick. This occurs as the formation dips towards the Gulf of
Mexico Sedimentary Basin where most stratigraphic units expand as they
plunge westward. The Intracoastal, however, lithologially grades Into the
Pensacola Clay and/or the Miocene-Pliocene Coarse Clastics near the
Okaloosa-Santa Rosa county line. Along the axis of the Apalachicola
Embayment in southwestern Gulf County, the formation exceeds 300-feet
in thickness and appears to continue to thicken offshore. The unit pinches
out against the older units as they approach the surface. This up-dip limit
line is approximated in Figure 8.
The regional dip of the top of the Intracoastal is to the south-southwest.
Local changes occur in that regional trend, especially on the east flank of
the embayment (Figure 9). The regional dip is approximately eight feet per
mile (0.09 degree) in the Bay County area and less than three feet per mile
(0.03 degree) in Liberty and Franklin counties.
The Intracoastal is present in the subsurface from western-most
Okaloosa County eastward to the Ochlockonee River area in western
Wakulla County. The updip limit extends northward through northern
Liberty, central Calhoun, and northern Bay counties (Figure 8). It is
postulated to continue to dip and thicken offshore to the south and
southwest.
Mitchum (1976) reported Miocene-Pliocene unlithified dolomites in the
offshore area. His description of well-formed euhedral rhombs, varying in
size from microcrystalline to medium crystalline, and having sharp corners
showing no abrasion, is a good description of the dolosilt horizon at the
base of the Intracoastal from onshore cores. His published seismic profile
lines seem to verify this correlation.
PALEONTOLOGY AND AGE-Fauna from the Intracoastal Formation
is prolific and abundant. The two surface exposures of the Intracoastal,
along Econfina Creek in Bay County and near Carrabelle in Franklin
County, have been referred to as the Cancellaria zone and described by
Cooke and Mossom (1929), Cooke (1945), and Purl (1953). Their
descriptions generally refer to it as a shelly limestone.
The Intracoastal is a richly microfossiliferous calcarenite or wackes-
tone including calcareous nannofossils, planktonic and benthic foramini-
fera, echinoid fragments, spicules, mollusks, shark teeth, ostracods, and
relatively rare fossil fragments that appear to be parts of diatoms.
In Walton County, Huddlestun (1976a) identified numerous planktonic


24


































.-- UP L WLEc


Figure 8. Thickness of the Intracoastal Formation.

































Figure 9. Top of the Intracoastal Formation.





BULLETIN NO. 58


foraminifera from the Intracoastal Limestone; and, by using various
donation schemes (Berggren, 1973; Blow, 1969; and Lamb and Beard,
1972), dated the Intracoastal from late Early Pliocene to Late Pliocene
(Huddlestun's Intracoastal Limestone was only the upper half of the
presently defined Intracoastal Formation).
In Bay County, Schmldt and Clark (1980) zoned planktonic foramini-
fera using the schemes of Bolli (1957), Lamb and Beard (1972), and
Berggren (1973, 1977). Their estimated time of deposition began with the
late Middle Miocene (N11-N12) and ended in the early part of the Late
Pllocene (N18-N21). They point out that a hiatus occurs in the middle of the
formation. This was graphically displayed by Clark and Wright (1979), who
also estimated sediment accumulation rates above and below missing
planktonic foraminiferal zones from well cuttings in the Bay County area.
In Okaloosa County, Clark and Schmidt (1982), again using planktonic
foraminifera, dated the Intracoastal as late Middle Miocene to Pliocene.
They also noted the missing foraminiferal zones which indicate a probable
hiatus. Boiling (1982) also found that to be the case in Gulf County, although
she did state that, due to poor preservation, the exact timing of the hiatus
could not be conclusively established.




Table 2. Partial Ilst of planktonic foraminifera identified from the Intraooastal
Formation (from Schmidt and Clark, 1980).


Globigerina dutertrei
G. nepenthes
Globogerinoides conglobatus
G. obliquus
G. obliquus extremes
G. quadrillobatus sacculifer
G. quadrillobatus trilobus
G. ruber
Globorotafia acostaensis
G. continuosa
G. crassaformis
G. exllfs
G. fohsi fohsi
G. fohsi lobata
G. fohs/ peripheroronda
G. fohsi robusta
G, humerosa
G. inflata
G. lenguaensis
G. margarita


G. menardii
G. merotumida
G. mufticamercata
G. p/esiotumida
G. praemiocenica
G. praehirsulta
G. praemenardfi
G. puncticulata
G. ronda
G. scitula
G. siakensis
G. tumida
G/oboquadrina altispira
G. dehiscens
Hastigerina siphonifera
Orbu/ina bltobata
0. suturalis
0. universe
Sphaeroidinel/a dehiscens
Sphaeroidinellopsis seminulina
S. subdehiscens


27





BUREAU OF GEOLOGY


Wiggs and Schmidt (1978) and Schmidt and Clark (1980) listed some
stratigraphically significant discoasters and coccoliths from the Walton and
Bay County vicinity. Although they did not zone the various samples, the
general assemblage agreed with the planktonic foraminifera evidence.
West of the real extent of the Intracoastal Formation is the stratigraphically
equivalent Pensacola Clay. Clark and Schmidt (1982) identified Creta-
ceous nannofossils as well as Miocene forms from this unit. Cretaceous
limestones, presently exposed north of the area in Alabama, are the
apparent source of the reworked fauna. No older reworked forms have
been found from the Intracoastal.


Table 3. Partial list of the calcareou nannofosils identified from the Intracoatal
Formation (from Schmidt and Clark, 19W).
Braarudosphaera bigelowi D. quinqueramus
Catinaster coalitus D. surculus
Coccofithus pelagicus D. variabilis
Cyclosoccolithina macintyrel Discolithina sp.
Discoaster brouweri Hel/copontosphaera sp.
D. calcars Reticulofenestra pseu-
D. challenger doumbilica
D. kugleri Reticulofenestra sp.
D. neohamatus Spenolithus ables
D. pentaradiatus Spenolithus sp.



Faunal evidence points to a middle to outer shelf environment for the
Intracoastal Formation. Planktonic foraminifera commonly comprise about
50 percent of the foraminiferal fauna, the same percentage which occurs
today in the eastern Gulf of Mexico between depths of 100m 190m
(Wright, 1979). There are changes in the fauna in some cores near the top
of the formation. The proportion of planktonic tests decreases and
mollusks, echinoid spines, and shallow water ostracods increase. Benthic
foraminiferal data tends to yield more shallow depths (5 m to 100m) than the
planktonic proportion would indicate (Humrell, 1982).
Lithologic evidence, such as the presence of glauconite, phosphorite,
kaolinite, quartz sand, and heavy minerals also supports a near-shore,
open marine environmental interpretation.


28





BULLETIN NO. 58


Table 4. Partial List of benthic foramlnifera Identified from the Intracoastal
Formation (from Hummell, 1982).


Amphistegina lessonii
Anomamina sp.
Bigenerina floridana
. nodosaria textularoidera
Boivina perca
Bolivna sp.
B. marginata mu/ticosta
Buliminella elegantissima
B. carseyae
Bulinel/a curta
Cancris communis
Cibicidella variabilis
Cibicides lobatulus
Cibicidies sp.
Cibicides sp.
Dentalina pyrula
D. communis
Discorbis sp.
Discorbis subauracana
E. rolshauseni
F. punctata
Florilus grateloupi
Fursenkoina exifis
Globulina inaequalis
G. gibba
G. rotundata
Gyroidinoides sp.
Hormosina sp.
Lenticulina degolyeri


L. americana spinosus
L. vaughani
Marginulina dubla
M. howei
Massifina mansfieldi
Nonion sp.
Nonlonella scapha
Planu/ina sp.
Polymorphina sp.
Pseudopoly morphine rutila
Pullenia salisburyi
Recto bofiuina vicksburggensis
monssouri
Reyssella sp.
Reyssella miocenica
Rotalia beccari)
Siphogenerina lamellata
Siphonina jacksonensis
Textularia articulatus
T. gramen
T. flordana
T warren
T agglutinans
Uvigerina pitv/ata
U. lirettensis
U. subperegrina
U. auberiana
U. byramensis
Virgulina (virgu/lnefaa)
miocenica


Chipola Formation
NOMENCLATURAL HISTORY-The name Chipola Formation was
first suggested by Bums (1889, in Dall, 1892). He collected and described
mollusks from exposures on the Chipola and Apalachicola rivers. Dali and
Stanley-Brown (1894) later called these beds the Chipola shell marl.
Matson and Clapp (1909) included these beds as a member in their Alum
Bluff Formation, and Gardner (1926) later promoted the member to a
formation. Puri (1953) referred to the Chipola as a faces of the Alum Bluff
Stage which he placed within the Middle Miocene. It was redefined as a
formation once again by Puri and Vernon (1964).
The lithologic characteristics of the Chipola have not been well-de-
fined. In the type area, Purl and Veron (1964) described it as a blue-gray to
yellowish-brown, highly fossiliferous marl studded with molluscan shells.


29





BUREAU OF GEOLOGY


They further state that this marly faces exists only in the vicinity of the
Chipola and Apalachicola rivers. Cooke (1945) described two other faces:
a sandy limestone found primarily in the subsurface and a light colored,
coarse, sandy faces that contains clay. Huddlestun (1976a) stated that the
lithology at the type locality of the Chipola is atypical for the formation. He
further stated the Chipola lithology is varied and heterogeneous.
Huddlestun described three lithofacies for the Chipola Formation: an updip
shell bed, a downdip nonshelly calcareous sand, and a sandy limestone,
which lies even further downdip. This type of lithofacies mapping results in
the merging of contemporaneous depositional units, not lithologic
packages or formations.
The author has attempted in this study to establish a stratigraphic unit
by correlating nearby core holes with the type area, namely the exposure at
Alum Bluff. The Chipola Formation exposed at Alum Bluff has been
described by numerous authors; most of whom were interested in
paleontology as evidence of age and paleoecology (Gardner, 1926-1950;
Cushman and Ponton, 1932; Puri and Vernon, 1964; Banks and Hunter,
1973). As a result, the Chipola has been placed in the Middle Miocene,
Alum Bluff Stage; and it has become a chronostratigraphic or biostratigra-
phic unit rather than a lithostratigraphic formation.
The Chipola Formation, as defined in this paper, uses the lithotype and
stratigraphic position of the described Chipola at Alum Bluff in Liberty
County. From that area, correlations using cores and well cuttings are made
to the southeast and southwest into the deeper, thicker sequence of
sediments. As a result, the age of the Chipola Formation does not
correspond only to the Middle Miocene (the age near the type area) but
crosses time lines and is younger toward the Gulf Coast (Figure 4).
LITHOLOGY-As previously stated, the Chipola Formation has been
described by many authors. They were mostly interested in the
well-preserved mollusk and foraminiferal assemblages from exposures
along the Chipola and Apalachicola rivers. Because of the lithologic
variability described in the past literature, a well-defined, concise
description of the formation does not exist to the extent that it could be used
to identify and map the unit. The present definition, therefore, will utilize the
lithologic type described from the stratigraphic interval present at Alum Bluff
in Liberty County. The described lithology will be from that stratigraphic
horizon as it is mapped in cores and well cuttings throughout the subsurface
in the Apalachicola Embayment.
Near the type area, the Chipola is a very light gray to white, sandy
(quartz), fossiliferous calcarenite or wackestone. Mollusks, particularly
gastropods, and foramlnlfera are abundant. It is poorly to moderately
indurated and accessory minerals include quartz sand (10 to 50 percent),
micrite, and small amounts of heavy minerals, mica, and phosphorite.
Downdip towards the Gulf of Mexico some slight changes are noted which
may be due to different groundwater conditions. The most noticeable
difference is the slightly better indurated nature of the unit and a decrease in
sand content.


30





BULLETIN NO. 58


Cores from downdip commonly contain this Chipola unit, described as
a yellowish-gray to light gray, moderate to well-indurated sandy (quartz),
fossiliferous limestone. Although there is a considerable amount of plastic
material present, it could be classified as a wackestone or a packstone. The
fossil content and accessory mineral suite is the same as that described
updip. X-ray analyses of samples from cores identified calcite, aragonite,
quartz, dolomite, and some montmorillonite clay as the dominant minerals
present.
OVERLYING AND UNDERLYING UNITS-The Chipola Formation
overlies the Intracostal Formation throughout most of its area extent. Only
updip near the outcrop area where the Intracoastal is not present does the
Chipola overlie a different unit. There, it is underlain by the Chattahoochee
Formation.
The Chattahoochee Formation contrasts markedly with the Chipola in
that the former is a very pale orange to very light gray, moderate to
well-indurated, calcilutitic, dolomitic limestone or fossiliferous mudstone,
with fossils being present but not abundant. The Chipola is a more poorly
indurated, molluscan-rich, sandy, clayey calcarenite or wackestone. The
Intracoastal also is easily distinguished from the Chipola, although locally
the contact appears gradational. The Intracoastal is a yellow-gray to
olive-green, sandy (quartz), slightly phosphatic, biocalcarenite or wackes-
tone. It is poorly consolidated, and microfossils are abundant, with mollusks
being common but not abundant.
Overlying the Chipola Formation is the Jackson Bluff Formation or the
Hawthorn Formation. The Jackson Bluff, present throughout most of the
downdip sequence, is similar to the Chipola but differs in being much less
consolidated, more sandy (quartz), and clayey, and pelecypods are
dominant over gastropods. The difference in induration is the most obvious
difference in core samples. In the northern Liberty County area, the
Hawthom Formation overlies the Chipola. The Hawthorn is predominantly a
quartz sand with a clayey and micritic matrix, and phosphorite is also
present in trace amounts.
The gamma log signatures do not show a distinct enough change to
warrant their use for upper and lower picks of formation contacts. There are,
however, a few general trends (see Appendix III). The Intracoastal is
commonly higher in gamma counts than the Chipola, and the overlying
Hawthorn is commonly lower in activity. Where the Jackson Bluff overlies
the Chipola, there is no noticeable change in the gamma log.
THICKNESS AND DISTRIBUTION-The Chipola, as defined in this
study, is restricted within the Apalachicola Embayment in Bay, Calhoun,
Liberty, and Gulf counties. It Is not present in the Franklin County area. Near
the outcrop area north of Bristol in Liberty County, it averages 60 to 70 feet
in thickness. Downdip it is usually the same thickness, although it is
sporadically thinner and at times absent. When it is absent, the Jackson
Bluff shell beds are mapped as the entire mollusk-rich zone above the
Intracoastal.
Near the outcrop area, the Chipola is about 75 feet above present sea





BUREAU OF GEOLOGY


level; downdip the deepest recorded Chipola lies about 140 feet below sea
level in southern Gulf County and dips to the south at about 3.5 feet per mile
(0.04 degree) (see geologic cross sections for regional trends, Figures 13-
18),
PALEONTOLOGY AND AGE-As previously stated, the exposed part
of the Chipola has received a considerable amount of attention from
geologists and paleontologists. Burns in 1889 (in Dall, 1892) was the first to
record molluscan collections from the shell beds on the Chipola River.
Gardner (1926) collected samples from a number of outcrops throughout
the Florida Panhandle and published a comprehensive description of the
fauna. Vokes (1965) described the gastropods. A number of additional
reports on the fauna of the Chipola Formation have been published in the
Tulane Studies in Geology and Paleontology Series by E. H. Vokes and H.
E. Vokes (1969-1982).
The benthic foraminifera of the Chipola Formation were described by
Cushman (1920), Cushman and Ponton (1932), and Purl (1953). Puri also
included a list of identified ostracod species. Planktonic foraminifera were
described by Gibson (1967), Akers (1972), and Huddlestun (1976a). They
estimated the time of deposition to be in the Globigerinatella insueta Zone,
which is from the late part of the Early Miocene. Huddlestun suggested it
was transitional in age between the Early and Middle Miocene.
Akers (1972) reported the presence of calcareous nannofossils in
Chipola material. Coral species were described by Vaughan (1919) and
Weisbord (1971). Finally, Bender (1971) dated corals from the Chipola
using the He/U ratio method. He estimated a concordant age of 14-18
million years. This would put the Chipola in the late Early Miocene or early
Middle Miocene.
The present study did not identify fauna from the Chipola Formation;
fossils were used only as lithologic elements. There were, however, time
lines estimated for the underlying Intracoastal formation. The uppermost
Intracoastal near the coast was estimated to be early Late Pliocene. This
would probably put the downdip Chipola near the present coast in the Late
Pliocene. The Chipola was dated as Early to Middle Miocene where it is
exposed (see above). It can, therefore, be concluded that the presently
defined Chipola Formation is younger downdip near the present coast than
it is updip, where it is exposed. This relationship is displayed in Figure 21.

Jackson Bluff Formation
NOMENCLATURAL HISTORY-The Jackson Bluff Formation was
named by Purl and Vernon (1964). They combined the Ecphora and
Cancellaria biofacies of Purl (1953) into one formation because both are
exposed at Jackson Bluff in Leon County. This is the only exposure at which
more than one of Puri's four biofacies has been observed. Puri and Vemon
(1964) included the Jackson Bluff Formation in the Choctwhatchee Stage of
Purl (1953), which included all Miocene sediments of post-Alum Bluff age in
the Florida Panhandle and their equivalents in the central and western Gulf
states. This stage is approximately equivalent to the Upper Miocene Series.


32





BULLETIN NO. 58


The sequential changes in nomenclature leading up to the current
usage is extensive and will not be repeated here. For a complete history of
the use of the terms Jackson Bluff Formation and Choctawhatchee Stage,
see Schmidt and Clark (1980, pp. 41-44).
The type section, as designated by Puri and Vemon (1964), is in the
face of an old road-metal borrow pit, about 150-yards south of the dam at
Jackson Bluff along the Ochlockonee River (T1 S, R4W, S20, bbb). The site
is currently owned by the State of Florida, and is managed by the
Department of Natural Resources. The section exposed here is about 40
feet in thickness, of which the upper 12 feet are Jackson Bluff Formation
(except for a two-foot soil zone).
The Jackon Bluff Formation, like the Chipola, was also defined in the
past on the basis of its fauna and not on its lithologic characteristics. As a
result, the Jackson Bluff has been considered a paleoecological faces and
a chronostratigraphic unit.
As was the case for the Chipola Formation, the northern Liberty County
area (a geographic area between the "Type" at Jackson Bluff and the
exposed sediments at Alum Bluff along the Apalachicola River) is used to
identify the stratigraphic position and lithologic character of the unit. This
interval is mapped downdip in cores and well cuttings.
LITHOLOGY-The Jackson Bluff Formation at the type locality has
been described as consisting of three clayey, sandy, shell beds (Puri and
Vernon, 1964). The beds are differentiated on slight lithologic variation and
their mollusk assemblage.
This clayey, sandy, shell bed is exposed along a number of stream or
river bluffs throughout the Florida Panhandle. Sediments that are
lithologically similar lie near the surface in a narrow band extending from 20
miles west of Tallahassee, Leon County, northwest to the Oak Grove area
of north-central Okaloosa County, a distance of about 100 miles (Figure
10). The shell beds vary from tan to orange-brown to gray-green, sandy
clays and clayey sands with abundant mollusk shells. The outcrops are
generally poorly exposed and of limited extent. As a result, true
stratigraphic relationships have been poorly understood and most past
mapping has emphasized faunal or chronologic characteristics.
Well cuttings and core descriptions allow this unit to be mapped
downdip, where it is covered by younger sands and clays. These shell beds
have not previously been called the Jackson Bluff Formation west of the
Washington County area (it appears as undifferentiated Alum Bluff Group
on the geologic cross sections Figure 13-18). In the cores, the unit is
generally a light gray, poorly-consolidated, clayey, quartz sand with
abundant micro and macrofossils. Mollusk shells dominate the fossil
fauna; however, foraminifera, ostracods, bryozoans, echinoids and worm
tubes are also common. X-ray analyses show the common minerals to be
quartz, calcite, aragonite, montmorillonite, kaolinite, phosphorite, mica and
pyrite.
OVERLYING AND UNDERLYING UNITS-The Jackson Bluff type
sediments overlie the Chipola Formation in the central and western updip


33















UPIw
i.ILOW


TOP OrF 4JCKI M BLIFF FORMATIN TnP swBIm


Figure 10. Top of the Jackson Bluff Formation type sediments.


PnR





BULLETIN NO. 58


parts of the Apalachicola Embayment. In Wakulla and southern Liberty
counties, where the Chipola Is not differentiated from the Jackson Bluff, the
Intracoastal Formation is the underlying unit. In the updip eastern parts of
the embayment, the Hawthorn Formation underlies the Jackson Bluff
Formation.
The Chipola Formation is generally more consolidated, has less quartz
sand, and more carbonate than the Jackson Bluff. The Intracoastal is easily
distinguished by its olive-gray color, its lack of mollusks, and by being a
medium to fine-grained biocalcarenite or wackestone. The Hawthorn, only
present at the northeast comer of the study area, is a clayey, calcareous,
quartz sand. Fossils are not present in the Hawthorn except In localized
limestone beds further north in Gadsden County (outside the present study
area).
Unnamed clayey sands, clays, and coarse sands overlie the Jackson
Bluff Formation (Figure 11). In areas of higher elevations (updip), the
coarse sands and gravels are associated with the Citronelle Formation or
reworked Citronelle. In the east-central part of the embayment (downdip) in
southern Liberty and Franklin counties, there is a massive clay bed over the
Jackson Bluff; this bed appears to be locally mappable (Figure 18). Both the
poorly-sorted sands and the massive day bed are easily distinguished from
the shell-rich Jackson Bluff Formation.
Gamma logs do not offer much assistance in picking these formation
contacts. The overlying sands tend to have low activity (50 counts per
second or less) and the clay beds generally are higher (up to 100 cps). The
Jackson Bluff, however, exhibits variable gamma intensity. The contact is
often gradational and may be difficult to ascertain without samples.
Below the Jackson Bluff Formation, the Intracoastal Formation
generally has higher gamma counts, although this contact is also
gradational; and, therefore, only a zone of transition is evident. The Chipola
is also slightly higher in counts than the Jackson Bluff; but, again, the
change (or contact) Is subtle; and samples probably would be needed for
positive contact picks.
THICKNESS AND DISTRIBUTION-The Jackson Bluff Formation
type sediments, as defined in this study, include the undifferentiated Alum
Bluff Group from Okaloosa and Walton counties. Their lithologic similarity
and stratigraphic position is the basis for their being combined. As a result,
the areal extent of this formation extends from western Leon County to
northwestem Okaloosa County (Figure 10). The regional dip is to the
south-southwest and ranges from about three feet per mile (0.03 degree)
on the east side of the embayment to just over eight feet per mile (0.09
degree) In Okaloosa County. The unit ranges from a high of 220 feet above
sea level in Walton County to a low of 148 feet below sea level in Gulf
County. The greatest thicknesses occur downdip near the present Gulf
coast, where it approaches 150 feet in thickness. From this vicinity
northwestward, the unit thins, and in some locations is not present at all.
This is most likely caused either by Irregular deposition due to undulatory
bottom conditions, or by post-depositional erosion, or both.


35







36


BUREAU OF GEOLOGY


I .,
r. .
F ~
.; ..~
.....
~ .L~II
C~~~ ~1


'I,


Figure 11. CORE 1: Bedded quartz sands from Core W-14925, from about
11 feet to 18 feet. CORE 2: Jackson Bluff Formation from Core
W-14993, from about 40 feet to 48 feet. (The top of each core is
towards the bottom of the page). Core diameter is 1% inches.





BULLETIN NO. 58


PALEONTOLOGY AND AGE-Fossil mollusk shells are abundant
throughout the Jackson Bluff sediments and have been discussed
extensively in the literature (Mansfield 1930, 1932; Gardner 1926-1944;
Cooke and Mossom 1929; and others). Corals from the Jackson Bluff were
identified by Weisbord (1971). Microfossils are also abundant, with
ostracods having been reported by Howe (1935) and foraminifera having
been reported by Cushman (1920), Cushman and Ponton (1932), Purl
(1953) and Beem (1973). Akers (1972) and Huddlestun (1976a) examined
the planktonic foraminifera from the outcropping and downdip Jackson
Bluff. They both concluded that the Jackson Bluff Formation was deposited
in the middle to earliest Late Pliocene. Akers (1972) and Akers and Koeppel
(1973) also reported the presence of calcareous nannofossils from some
horizons within the Jackson Buff. Their age correlates well with the
planktonic foraminifera zones.
Downdip the fauna appears to include most of the previously reported
fossil types. Scattered planktonic foraminifera, however, reveal that the age
of the unit downdip may be latest Pliocene and may extend into the
Pleistocene. This is also expected because of the Late Pliocene age
obtained for the underlying Intracoastal Formation. This relationship is
expressed in Figure 4.
Paleoecologic interpretations from surface samples were published by
Dubar and Beardsley (1961) and Dubar and Taylor (1962). They concluded
that the lower part of the Jackson Bluff type sediment was deposited under
open marine conditions with a water depth of no more than 120 feet. Depth
of water near the top of the unit was less than 48 feet. Their interpretations
were made from comparison of fossil molluscan and foraminiferal
assemblages with extant communities in the Gulf of Mexico, western
Atlantic, and Caribbean. Beem (1973), using a modern species distribution
approach on 128 species of benthic foraminifera, estimated water depths to
have been less than 100 meters (328 feet).
PLEISTOCENE SEDIMENTS
Undifferentiated Sands and Clays
NOMENCLATURAL HISTORY-A wedge-shaped plastic unit of
quartz sands, gravels and clays overlies the shell beds of the Jackson Bluff
Formation. This unit includes some clayey sand and gravel, which probably
correlates with the Citronelle Formation (present along the northern edge of
the study area where elevations are higher). Other beds contain reworked
clayey sands, massive clay beds, coarse quartz sands, and Pleistocene to
Recent coastal sands. This plastic wedge of sediments extends to the
surface from the top of the Jackson Bluff Formation.
Because these deposits are relatively unfossiliferous and difficult to
stratigraphically correlate, few reports have emphasized Pleistocene to
Recent stratigraphy. The most comprehensive report (although of
restricted real extent) was that of Schnable and Goodell (1968). Their
report discusses the Pleistocene to Recent stratigraphy and development
of the coastal strip in Gulf and Franklin counties.


37





BUREAU OF GEOLOGY


Other studies that briefly mention the shallow clastics include Schmidt
and Clark (1980) and Clark and Schmidt (1982). In addition, several theses
(Huddlestun 1976a, Clark 1980, and Boiling 1982 from Walton, Bay,
and Gulf counties, respectively) mention this group of sediments.
LITHOLOGY-There are several different lithologic packages within
this undifferentiated sand and clay unit. Along the northem parts of the
study area, associated with higher elevations, the sediments can be
correlated with the Citronelle Formation. The type locality of the Citronelle
Formation lies near Citronelle, Alabama. In northwest Florida, it generally
consists of fluvial, crossbedded sands, gravels and clays, and post-depo-
sitional limonite. In the lower elevations towards the coast, reworked coarse
sands and gravels are common in Walton, Bay, Calhoun, and Gulf counties.
In southern Liberty, Gulf, and Franklin counties, there are massive clay
beds overlying the Jackson Bluff. These clay beds are locally interbedded
with graded, coarse, quartz sands (Figure 11). These clay beds are
generally greenish-gray to olive-gray, massive, plastic, and sandy (quartz).
The dominant clay mineral is kaolinite, with montmorillonite and
palygorskite also present. These clays are low in permeability and act as an
impediment to vertical groundwater migration. The clay beds and graded
sands are present in the central part of the Apalachicola Embayment. They
are not known from the area of Bay, Walton, or Okaloosa counties.
Quartz sands and gravels are present in southern Liberty, Gulf, and
Franklin counties. Mineralogically, they are predominantly quartz with
minor amounts of heavy minerals and organic material. These sands range
in size from very fine to gravel, and show cross-bedding and graded beds.
The unconsolidated nature of these poorly-sorted sands and gravels make
them an excellent local aquifer.
The lithologic unit that extends to the surface is a pale yellow-brown to
light gray, unconsolidated, medlum-grained clayey sand. The common
minerals are quartz, clay, heavy minerals, and mica, in order of abundance.
These clayey sands are usually unfossiliferous, although plant remains in
the form of wood fragments and soil-zone roots are common.
OVERLYING AND UNDERLYING UNITS-The various clastic units
that lie near the surface are easily distinguished from the underlying
formations. On the western flank of the embayment and farther west in the
study area, clayey sands overlie the Intracoastal Formation downdip near
the Gulf Coast. The calcareous and abundantly microfossilifeous nature of
the Intracoastal contrasts markedly with the rarely fossiliferous clastics
above.
In the updip areas and in the central part of the embayment, the
Jackson Bluff Formation type sediments underlie the clayey sands. The
molluskan-rlch nature of the Jackson Bluff is the major lithologic difference.
This contact is often gradational over several feet.
Gamma logs are only marginally useful for separating the main
lithologlc types within this unit. The massive clay beds generally produce
relatively high counts; however, the varying amounts of clay, mica, and
heavy minerals (mineral material that also produce high gamma counts)


38





BULLETIN NO. 58


scattered throughout the section make it difficult to obtain distinct lithologic
separations.
The coarse sands and gravel beds are usually low in gamma activity
with occasional spikes or high counts where thin clay stringers occur (see
Appendix III).
The contact with the underlying Jackson Bluff or Intracoastal
formations can general be approximated; however, the specific signature
varies from well to well. The base level of counts is usually higher in the
clayey carbonates below than In the classics above. The shallow clay beds
often have thin spikes of high counts.
THICKNESS AND DISTRIBUTION-The clayey sands, which repre-
sent reworked deposits, are present over the entire study area. In the
northern parts of the area, the Citronelle Formation comprises the hills of
higher elevations. Only in the central part of the embayment in southern
Liberty, Gulf, and Franklin counties can the massive clay beds and the
graded coarse quartz sands be found (see Figures 15 and 18).
The thickness of these beds varies from zero (where they have been
eroded updip in the highlands) to over 110 feet along the axis of the
embayment. The regional dip is to the south-southwest, although local
changes do occur.
Pleistocene sea level fluctuations have reworked and homogenized
these near surface sediments making outcrop localities similar.
PALEONTOLOGY AND AGE-The undifferentiated sediments are
generally unfossiliferous. There are, however, some mollusk shell
fragments within the unit near the present coast. Other fauna in these beds
include rare finds of foraminifera, ostracods, echinoids, and bryozoans.
In the graded coarse sands and gravels, wood fragments are
occasionally present. Rapid deposition in a fluvial or deltaic environment
may be the reason for their preservation. In some cores, this graded unit
seems to possess various sequences of forest beds. All cross-beds are
sloped south at approximately the same dip angle. This probably reflects
the prograding Apalachicola Delta in the Late Pleistocene.
Schnable and Goodell (1968) used numerous radiocarbon dates to
estimate the age of some shallow sediments (30-40 feet below present sea
level) along coastal Franklin and Gulf counties. Their data suggest dates of
27,000 to 34,000 years before present for some organic, clayey sand beds.
Most of the clayey beds from the core holes and well cuttings
throughout the study area were prepared for microfossil observation.
Smear slides showed that calcareous nannofossils were rare and poorly
preserved; however, diatoms were abundant in some shallow clay beds
(Figure 24).
A mixture of fresh water and marine diatoms were identified (Appendix
I). Certain species, such as Gomphonema parvuleum and Cyclotella
striata, are associated with nutrient-rich waters near river outlets. The
overall assemblage indicates a fresh water input into a marine environment.
This fits well with the prograding delta, as indicated by the stratigraphic
information.


39





BUREAU OF GEOLOGY


Most of the diatom species found in these beds are living today and
were common in the Pleistocene (W. Miller, personal communication,
1982). One location on St. George Island, where diatoms were recovered,
occurs in a clay bed above a horizon dated by Schnable and Goodell (1968)
as 27,620 to 40,340 years before present. This Late Pleistocene age fits
well with the diatom data.


Table 5. Partial list of diatoms Identified
Undifferentlated Sands and


from the shallow clay beds within the
Clays Units (Appendix I).


Actinocyclus octonarius
Actinoptychus australius
A. senarius
Biddulphia aurita
B. rhombus
Campyloneis grevillei
Cocconeis placentulia
Coscinodiscus sp.
Cyclotella strata
Cymbeila minute
Denticulia sp.
Diplonels smithii


Epithemia argus
E. ocellata
Eupodoscis radiatus
Gomphonema parvulum
Navicula lyra
Parafia sulcata
Podos/ra sp.
Pseudauliscus sp.
Rhapohoneis sp.
Rhoplodia gibba
Synedra ulua
Triceratum favus


Table 6. Formation abbreviations for geologic cross sections A-A' to J-J'.


A
AB
BC
CHATT
CHIP
CIT
CLAY
CS
CSDS
DS
4
GRAD
HAW
IC
JB
MAR
MB
OCALA
OY
SM
SDS
SW


-Algal Bed
-Undifferentiated Alum Bluff
-Bruce Creek Limestone
-hattahoochee Formation
-Chipola Formation
-itronelle Formation
-Clay Massive
-Clayey Sands
-Coarse Sands
-Dolosilt and Clay
-Four-Mile Village Member


SDS-Graded Sands
-Hawthorn Formation
-Intracoastal Formation
-Jackson Bluff Formation
-Marianna Limestone
-Mollusk Bed
-Ocala Group Undifferentiated
--Oyster Bed
-St. Marks Formation
-Sands (Quartz)
-Suwannee Limestone


40


















I Il' L.33 LEr


s--P "''rC-. .~-IL o -- -


LOCAnTI OF QOEOBIaC CoN SeCTKM "I LIBERTY 1 -



t___, ,. ,T,_ .- FRAML>--.
1z
a
COnE J ~
X W ELLLocatT o y gel i FcWAect KLWm


Figure 12. Location of geologic crss s ction,








Figure 12. Location of geologic cross sections.













SI



I- A-


N a
I I I
r. .r r.


MSL


-1204 400


Figure 13. Geologic cross section A-A'.


METERS CET
OT 0


-o0+ -I10


-200


-604-


A'


U1. .


-9- --300

















B








MErrTr FEET
O- 0 MSL



-3.0 -oo


-60-


-200


Figure 14. Geologic Cross Section B-B'.


z.1
00





















d
I
1z
Ix
aII


WETERS FEET
OTr o


MSL


-a30 o00


-90o 30


-L20- -400


- lSO -C


I IT 'W
a O I340:wi m


Figure 15. Geologic Cross Sections C-C' and D-D'.


IKTlRI FEET
OT 0


MSL


-3S+ 10


-400


-W$ -200


-So-_ 300


10 OLw"q
4 16 --ImjQMTV

















METERS FEET E
+60o- +200


+ -3




0.


* + 1




o MSL


-30+ -100


-60- 200


-90 -300


-120 -400


iD

I-i I-t L-
C m

r I i
a- -S Si Vt

I. I- I I-

I: IE IE0
a-, jn ,
*c 10 M f
I- I I
S S i?
r


METEMR FEET F
+60. +200




+30- +100


o- o MSL


-30+ -100


-. ,- -60'

I ,' -
', --.

i -90'


- -2WX


-300


-120- -400


S30 WFULONETE4R


I. I
I
-is \~


Figure 16. Geologic Cross Sections E-E' and F-F'.


















H'


"TERS FEET
+30 + 100


-0 MSL


-301 -o100


-601 -200


- 400


G




NETERS cri(





0 o MSL


-30+ -00


-60- z2


-sO- -300


-120 -L -400


Figure 17. Geologic Cross Sections G-G' and H-H'.


2 a



Cm
I -
r w


I tI


N X
f i
MS
rW -

I I


G'






a
1 -

W t
2 z
N
I-


METERS FEET
+6r + 200


+30


+100




0 MSL


-30+- o00


-60i -200


9-1- 300


-120-- 400


I Eo.. ILEB
IC !amKILQaO T- R


z0 Ir a 3,0 KILOlLETERS


Figure 18. Geologic Cross Sections I-I' and J-J'.


*lTIE S FEET
OT 0


MSL


-5 100


-60 200


-901- 300


-120- 400





BUREAU OF GEOLOGY


ADJACENT STRATIGRAPHIC UNITS
CHICKASAWHAY LIMESTONE-The Chickasawhay Limestone was
extended into the Florida Panhandle from its type exposure on the
Chickasawhay River in eastern Mississippi by Marsh (1966). The
Chickasawhay Limestone and the Chattahoochee Formation are lithologi-
cally indistinguishable in the Okaloosa County area. As a result, these
formations were combined in subsurface mapping by Clark and Schmidt
(1982).
The Chickasawhay Limestone is primarily a tan, sucrosic dolomite; it
may also occur as dolomitic, fossiliferous limestone. It extends from
Escambia County eastward to Walton County, where it grades into the
Suwannee Limestone. The Chickasawhay is confined to the subsurface in
Florida.
Marsh (1966) and Poag (1972) placed the Chickasawhay in the Late
Oligocene and correlated Rt chronostratigraphically with the lower
Chattahoochee Formation and upper Suwannee Limestone in northern
Florida.
ST. MARKS FORMATION-Puri (1953) revived the term St. Marks
Formation and applied It to the calcareous facies of his Tampa Stage (Early
Miocene). The type locality described by Puri and Vernon (1964) is in
central Wakulla County. The formation was described as a pale to
yellowish-gray, argillaceous, moderately-indurated massive limestone,
with casts and molds of mollusks and abundant Sorites sp.
The St. Marks dips southwest from the type area and becomes totally
subsurface in the Apalachicola Embayment. In cores and well cuttings, the
St. Marks and Bruce Creek are difficult to separate lithologically. Near the
axis of the embayment these two formations are indistinguishable in
shallow sections. In deeper sections, the St. Marks lithology appears to
predominate. On the west flank of the embayment, the Bruce Creek
lithology is dominant. These two formations are probably conformable with
a slight variation occurring from St. Marks (Lower Miocene) to Bruce Creek
(Middle Miocene).
PENSACOLA CLAY-The Pensacola Clay was originally described
by Marsh (1966) from three oil test wells in Baldwin County, Alabama. In
Escambia and Santa Rosa counties, Florida, Marsh described it as a
dark-to-light gray, silty clay, containing variable amounts of quartz sand,
carbonized wood, pyrite, and mica.
Clark and Schmidt (1982) mapped the Pensacola Clay eastward to the
western side of Okaloosa County. Their work correlates the Pensacola Clay
with the lower part of the undifferentiated Alum Bluff Group and the lower
part of the Intracoastal Formation.
The Pensacola Clay has been dated as Middle to Late Miocene by
Marsh (1966) using benthic foraminifera. An age of late Middle Miocene
was obtained by Clark and Schmidt (1982) using planktonic foraminifera.
They tentatively dated the top of the Pensacola Clay as latest Miocene
using calcareous nannofossils.
Wright and Clark (1982) noted the regional trend of increasing


48





BULLETIN NO. 58


thickness of plastics to the west during the Middle and Late Miocene. From
benthic foraminiferal studies, they interpret a depositional setting dominat-
ed by shallow water (40-60m), nearshore, mud-rich habitats. They interpret
depositional and faunal patterns to Indicate an isostatic downwarp to the
west of the present study area. Increased plastic sedimentation beginning
with the deposition of the Pensacola Clay may have triggered this
downwarp. The plastic material appears to have originated in the Alabama
piedmont and coastal plain.
MIOCENE COARSE CLASTICS-The informal term "Miocene coarse
clastics" was introduced in the western Florida Panhandle by Marsh (1966).
He described a deposit of sand, gravel, clay, and shell beds which he
believed to be Miocene in age.
Clark and Schmidt (1982) showed that the Miocene coarse plastics
lithologically grade into the undifferentiated Alum Bluff Group and the
Intracoastal Formation in the western Okaloosa County area. They further
note that because the underlying Pensacola Clay was dated as latest
Miocene, the Miocene coarse clastics may be Pliocene in part, especially
where the unit overlies the Pensacola Clay. This unit represents a
continuation of clastic deposition as the region isostatically adjusted to the
increased sediment load.
HAWTHORN FORMATION-The Hawthorn Formation is a series of
marine, deltaic, and prodeltaic beds of diverse lithology. The co-type areas
are in the Alachua and Bradford counties area (Scott, 1982).
Near the present study area, the Hawthorn has been mapped in Leon
and Gadsden counties, located north and northeast of the main part of the
embayment during the Neogene. In Leon County, it is composed of
fine-to-medium grained quartz sand, sand-size phosphorite, silt, kaolinite,
montmorillonite, palygorskite, and sandy, phosphoritic limestone (Hendry
and Sproul, 1966).
The Hawthorn Formation was encountered in cores from northern
Liberty and western Leon counties (Figure 18). It consists of light gray to
pale orange quartz sands and clays. Occasionally, sandy, dolomitic
calcilutite with minor amounts of phosphorite is recorded. This is consid-
ered a Middle Miocene formation, therefore it would correlate chronostrati-
graphically with the Bruce Creek and Intracoastal formations downdip.

PALEOENVIRONMENTAL ANALYSIS

FORMATIONAL OBSERVATIONS
OCALA GROUP LIMESTONES (Late Eocene)-Fossils from the
three formations of the Ocala Group (the Inglis, Williston, and Crystal River
formations) have been studied by many authors (Vernon, 1942; Applin and
Applin, 1944; Purl, 1957; Cheetham, 1963; and many others). A wide range
of marine fauna including mollusks, foraminifera, bryozoans and corals
have been described.
In peninsular Florida, where the type localities of these formations are
located, Cheetham (1963) suggested that water depths did not exceed 150


49





BUREAU OF GEOLOGY


feet and that the Late Eocene depositlonal environments were probably
lagoonal with shoal water, tropical climate, and exceptionally uniform
hydrographical conditions during the Late Eocene. In the Florida
Panhandle, he suggested water depths of 100 to 300 feet.
Chen (1965), using a lithofacles mapping approach along with
published faunal lists, reconstructed a regional pattern of sedimentary
environments during the Paleocene and Eocene in Florida. He stated
Florida was a stable carbonate platform bounded by submarine escarp-
ments on both the Atlantic and Gulf of Mexico sides and separated from the
continental shelf at the north by the "Suwannee Channel". The platform
was characterized by shallow water, with reefs along Its northern and
eastern margins. Chen noted that, in the latest Eocene, parts of the platform
may have been emergent based on the unconformable relationships
mapped. This is also suggested by Randazzo (1972a, 1980) from
perographic evidence.
Chen (1965) noted the absence of shallow-water types of larger
foraminifera and bryozoans in the "Suwannee Channel" area. He pointed
out that deeper-water types are dominant there. Although well control in this
deeper part of the section is poor, Chen suggested that a degree of
interfngering between the plastic faces from the northwest and the
nonclastic facies from the south must exist somewhere along the channel.
The nonclastic faces steadily spread north and northwest during the
Paleocene and Eocene. This occurred as a result of continued growth and
migration of the calcareous fauna towards the warm, shallow marine
current to the northwest.
Regional paleogeographic maps of the southeastern coastal plain
(Chen, 1965), show a marine current crossing the Big Bend of Florida into
southwest Georgia from southwest to northeast. The axis of this channel or
current shifts northwestward through the Eocene until it was situated near
the present-day Apalachicola River. Evidence for this current is also seen in
the Georgia coastal plain (Schmidt, 1977).
MARIANNA AND SUWANNEE LIMESTONES (Olgocene)-The
Marianna and Suwannee limestones are similar to the underlying Ocala in
that they are mostly calcium carbonate and are fossiliferous, chalky
calcarentes. Yon and Hendry (1972) and Randazzo (1972b) briefly
summarized some paleoenvironmental interpretations from the Suwannee
Limestone in Hemando and Pasco counties. They concluded from the
predominance of calcarenites, bedding characteristics, and paleontological
evidence that the sediments of the Suwannee Limestone were deposited In
a warm shallow sea. Petrographic observations showed a predominance of
low energy, shallow water and higher energy, shallow subtidal environ-
ments.
The Suwannee in the panhandle has a different foraminiferal fauna
than that in the peninsula. The two assemblages merge in the Tallahassee
area. A physical boundary, such as a deeper, current-swept strait would
have separated and isolated the fauna, creating the different assemblages
observed.


50





BULLETIN NO, 58


The Marianna Limestone is of much less areal extent than the
Suwannee. It is present in Jackson, Washington, and Holmes counties at
the surface. In the subsurface in Bay and Walton counties, identification is
difficult. The foraminiferal assemblage was considered to represent
"moderately deep water (60 feet or more)" by Todd (in Puri and Vernon,
1964). Chen (1965), however, interpreted the conditions to have been very
shallow water, nearshore marine. From petrographic evidence, Randazzo
(1972b), interpreted the type section at Marianna to represent a low energy,
shallow water environment followed by higher energy and, probably, a
marine transgression followed in turn by a regression at the top of the
section.
CHATTAHOOCHEE AND ST. MARKS FORMATIONS (Late Oligo-
cene-Early Miocene). The Chattahoochee and St. Marks formations were
deposited in a warm (20" -30C) inner neritic (between low tide and 50
meters depth) environment (Puri, 1953). Sediments of the Chattahoochee
Formation were considered by Puri (1953) to be nearer shore, based on a
"meager" number of foraminifera species.
Purl considered the Tampa Stage (Early Miocene) seas to be
transgressive over the eroded surface of Oligocene or older limestones. He
concluded that early in the transgressive period a "limy1" lithofacies (the St.
Marks) was deposited downdip; and late during this transgression and the
regression that followed, a more plastic (Chattahoochee) lithofacies was
deposited updip.
Gremilllon (1966) described the exposed section along the Apalachi-
cola River near the city of Chattahoochee. He also suggested a shallow
regressive sea and, from the presence of some rubble beds, thought that
the shoreline was not very far away during that time.
The Chattahoochee Formation commonly contains quartz sand and
some clay beds. The fossil assemblage is not abundant and generally only
poorly preserved molds are found. This formation represents the first plastic
influx into the embayment area after the regression of the warm carbonate
seas of the Eocene and Oligocene.
The St. Marks Formation described from the east side of the
embayment (Puri 1953; Puri and Vemon, 1964; Hendry and Sproul, 1966;
Yon, 1966) is a sandy (quartz) calcarenite. Fossils, mostly foraminifera and
mollusks, are abundant.
BRUCE CREEK LIMESTONE (Middle MIocene)-The Bruce Creek
Limestone is described as a white to light yellow-gray, moderately
indurated, granular to calcarenitic limestone (Schmidt and Clark, 1980).
Quartz sand is common, as are minor amounts of phosphorite, glauconite,
and pyrite. Fossil content is abundant and includes mollusks, bryozoans,
echinoids, benthic and planktonic foraminifera, ostracods, and calcareous
nannofossils. This wide array of marine fossils, along with the plastic
mineral content, implies that the environment of deposition for this
formation was shallow, nearshore marine. The upper few feet of the Bruce
Creek often contain an algal-rich limestone, where algal oncolites are
common. This suggests a permanently submerged shoal environment





BUREAU OF GEOLOGY


(Logan, et a., 1964) or at least a shallowing of the water depth near the end
of Bruce Creek deposition.
Many authors have postulated depositional environments for the
Miocene in north and northwest Florida (Pur, 1953; Tanner, 1966; Banks
and Hunter, 1973; Weaver and Beck, 1977; and many others). In general,
shallow marine carbonates dominated the Early Miocene. The Middle and
Late Miocene saw increased plastics (quartz sands and clays), less fossil
material, and some prodeltaic sediments.
In the panhandle Puri (1953) described environments of deposition for
the faces in the Alum Bluff Stage (Middle Miocene). The Hawthorn was
deposited in continental and deltaic environments, the Chipola in warm
marine waters in depths greater than 60 fathoms (360 feet). The Shoal
River and Oak Grove fauna were considered mostly brackish with a slight
influx of inner neritic forms.
CLAYEY DOLOSILT (Middle Miocene)-In the central and eastern
parts of the embayment a dark gray, massive, plastic, clayey dolosilt
overlies the algal zone of the Bruce Creek Limestone. The environment of
deposition for this unit is not as clearly understood as for some of the
underlying and overlying formations. The fine-grained, clayey nature of the
unit with incorporated unetched, non-cemented dolomite rhombs may
imply a supratidal or tidal flat environment. The dolomite seems to have
formed in situ because there is no abrasion evident, and it is all the same,
very fine-grain size. There are no fossils evident.
Mitchum (1976) reported the same type of well-sorted, microcrystalline
to medium crystalline, unetched dolomite, in approximately the same
stratigraphic position from offshore; in addition, he also interpreted these as
authigenic grains which replaced calcite sediments. He further stated that
most of the magnesium would have been derived from interstitial water or
from seawater during long exposure on the sea floor. These sediments are
correlateable to the dolosilt bed from the onshore cores.
INTRACOASTAL FORMATION (Middle Miocene and Pliocene)-The
Intracoastal Formation is a richly microfossiliferous calcarenite including
calcareous nannofossils, planktonic and benthic foraminifera, echinoid
fragments, spicules, mollusks, shark teeth, ostracods, and small unidenti-
fled fossil fragments that appear to be parts of diatom frustules.
With such a diverse group of marine organisms, it is no surprise that the
precise environment of deposition is difficult to ascertain because of the
varying environmental requirements for each fossil group. Because of the
apparent abundance of benthic and planktonic foraminifera, this group was
used to approximate water depths.
Planktonic/benthic ratios in the Bay and Walton counties area are
about 0.5. This proportion occurs today in the eastern Gulf of Mexico
between depths of 100m and 190m (Wright, 1979). Toward the upper half of
the formation, the proportion of planktonic tests decreases; this was
probably caused by a shallowing of the water depth. A brief study of the
benthic foraminifera from two cores by Hummell (1982) suggests depths
between 5m and 100m from the Gulf and Franklin counties area.


52





BULLETIN NO. 58


These data suggest that the depositional environment was deeper
than for the two lithologic units immediately below (Figure 19). This
interpretation would represent a short-term reversal in the trend of
shallowing water during late Bruce Creek deposition.
Lithologic evidence, however, points out that plastic input from the
north increases in the younger sediments. The Intracoastal contains
kaolinite, montomorillonite, palygorskite, heavy minerals, and abundant
quartz sand. All of these minerals are present in older sediments exposed
on the coastal plain to the north.
It is postulated here that the fluvial sources northward (during
Intracoastal time, still north of the study area) carried much of the plastic
load from the southern Appalachians and narrow coastal plain. Heavy
mineral analysis by Isphording (1971, 1977) pointed out that much of the
heavy detrital minerals in the Florida Miocene originated from the high
grade metamorphic rocks or from the igneous rocks of northern Georgia
and east-central Alabama.
These sediment-laden fluvial sources also carried nutrients into the
marine environment. It is probably this nutrient-rich, warm water that
caused the planktonic and benthic communities to flourish. The phos-
phorite may be a result of high organic production both in the water column
and in the bottom sediment. Riggs (1979, 1980) has reported on the
Miocene phosphorites from the peninsula of Florida and discussed their
mode of origin. He considered that the cold, upwelling water that moved
across the Florida platform brought bacterially precipitated microcrystalline
phosphorite mud to the shallow-water environment.
This microcrystalline phosphorlte mud was populated by a benthic
community that ingested and excreted the muds as fecal pellets. A shallow
water microorganism hash with pelletal phosphorite also typifies the
Intracoastal in Panhandle Florida. Riggs' interpretation seems valid; a
fluvial nutrient source from the north was added to this phosphorite mud
during the deposition of the Intracoastal Formation.
A hiatus exists in the middle of the Intracoastal Formation. This was
discovered by zoning the various planktonic foraminifera using the
schemes of Bolli (1957), Lamb and Beard (1972), and Berggren (1973,
1977). The entire Late Miocene and part of the Early Pliocene is absent
from the Intracoastal, at least in the area where it could be zoned. This
hiatus occurs in Bay and Gulf counties, as reported by Schmidt and Clark
(1980) and Bolling (1982). Missing biostratigraphic zones such as this could
Imply a brief drop in sea level corresponding in part to the world-wide
"Messinian event." This sea level drop has been further documented in
Florida by Huddlestun and Wright (1977) from the Florida Panhandle, and
by Peck et a/. (1977) from south Florida.
There is, however, no apparent lithologic change across the hiatus.
Why this occurs is not clear, although a rapid sea level decline and quick
recovery could account for it (Figure 19). Such a sea level drop and rise is
suggested by Vail and Hardenbol (1979).
CHIPOLA FORMATION (Middle Miocene to Late Pliocene)--Several


53








RELATIVE RELATIVE CANES OF SEA LEVEL
SERIES FORMATION/lithology INTERETATIO C WATER DEPTH (Modified from VatL t 41... 1977)
HIGH 4 TR ---I 1 0 - RT Lm .5 FALIGj -- 0
a ______, ________ I I ,


s
w




,2












0








u
a





0







..........
5
1U


qtz sards

graded, bedded
qtz atndp

- saive
organic clays


shell beds of
JACKSON BLUFF FM
CHIPOLA FM, (shell
and IHaatane)


INTRA0CASTAL

clayey
dolaosiL

algIl (oncolitic)
li estoane
BRUCE CREEK
LIMESTONE

ST. MARKS
FORMATION


CHATTAHOOCHEE
FORMATION

StrwvANNw
LIMESTONE

KARIANNA
LIMESTOKE


OCALA GROUP


RESIDMvLN

FLL'VIAL 51W
DELTAIC SDS

LAGOOKAL OR
I TERTI DAL


NEAR SKDRE
MARI RE
SKALLOVU
MARINE


OPEN MARINE

SUPRATIDAL?

I TRATIDAL
SUBTIDAL
MARI E

SHALLOW
MARINE


NEAR SHORE
MARINE

OPEN MARINE
CARB. PLATFORM

OPEN MARINE


OPEN MARTIE


MAJOR BT


UPDIP
PRESgr -NT
SEA LEVEL
Terrace Sdp
S



CITRONELLE FM




JACKSON BLUFF FM
I-#


ALUM BLUFF
GROUP



CHIPOLA FM

ST. IARKS PF


CHATTAfOOCHER FM

SWANNHEE LS

MARIANNA
LS




OCALA GROUP
r-


- MEN


DOWND IP

Fluvial Sds
Prodslt*ic
S4 & Clayv
ACKSON BLUFP PfM
CHIPOLA HF







IWTRACDASTAL FM






INTRACOASTAL FM
BRUCE CREEK
LIMESTONE

ST, MARKS FM





SUWRAMEE
LS







OCALA CROUP


Figure 19. Generalized paleoenvironmental trend, Late Eocene to Recent.


I i


f





BULLETIN NO. 58


authors have collected fossil material from the type area of the Chipola
Formation, namely the Alum Bluff in Liberty County and the Chipola River,
Ten Mile Creek, and Farley Creek in Calhoun County. The most
comprehensive faunal descriptions include Gardner (1926); Purl (1953);
Vokes (1965, 1972, 1977); and Weisbord (1971). Shallow marine fauna
such as foraminifera, ostracods, mollusks, and corals have been the most
common fossils recorded.
Purl (1953) stated that two-th ids of the foraminiferal species occurring
in the Chipola are known to be living today in shallow warm waters and are
generally restricted to a depth range of 60 fathoms (360 feet). He further
estimated the waters to have been between 20 and 30 C,
More recently Furlong (1980) interpreted the depositionaJ environment
of the Chipola from studying the detrital sand size sediments and their
distribution within the formation. He concluded that the Chipola Formation
was deposited in an unrestricted lagoon and nearshore bay environment
similar to Florida Bay, but with considerably deeper water, probably 200
feet or more. A general shoreline was projected eastward beyond Alum
Bluff in Liberty County and northward in the vicinity of Marianna in Jackson
County.
The general faunal assemblage reported from the Chipola along its
outcrops holds also for the subsurface samples recovered from cores and
cuttings. As a result, the environmental interpretations published also seem
to be applicable downdip.
There is one important difference worth emphasizing. The Chipola
Formation as mapped downdip into the Embayment crosses time lines and
appears to be Pliocene near the present coast. This would call for the
Chipola-type environment to migrate south as sea level slowly dropped.
JACKSON BLUFF FORMATION (Pliocene)-The Jackson Bluff
Formation, like the Chipola, has been subject to a number of faunal studies.
Some that include paleoecologic interpretations Include Purl (1953), Dubar
and Beardsley (1961), Dubar and Taylor (1962), and Beem (1973).
Dubar and Taytor (1962) specifically studied the "type" at Jackson
Bluff in Leon County, identified macro and microfossils, and did a grain-size
analysis of the sediments. They concluded that the sediments were
deposited in an open marine, near-shore, shallow to intermediate shelf
zone, at depths of less than 21 fathoms (126 feet). They went on to state
that the formation was not a simple depositional unit. It apparently was
transgressive near the bottom (representing maximum water depth for the
section), then was deposited under shoaling conditions, and finally the top
of the section became transgressive again, but was deposited at a depth of
less than 8 fathoms (48 feet).
The clayey, sandy shell beds of the Jackson Bluff Formation from the
exposed sections compare well with the unit as mapped downdip into the
embayment. As was the case for the Chipola Formation, the Jackson Bluff
Formation appears to cross time lines and become younger near the
present coast. The unit downdip is probably Pleistocene in age.
Both the Chipola and Jackson Bluff formations show a complete suite


55





BUREAU OF GEOLOGY


of shallow water marine fossils and the lithologic components of the
prograding coastal plain. They contain quartz sands, calcite, aragonite,
montmorillonite, kaolinite, muscovite, and some heavy minerals. It appears
that the shoreline was considerably closer to the study area than during the
deposition of prior formations. This, it is assumed, is a result of the
prograding clastics of the coastal plain and a general regressive trqnd
(Figure 19).
MASSIVE CLAYS AND CLAYEY SANDS (Pleistocene)-Overlying
the Jackson Bluff Formation in the central part of the Apalachicola
Embayment are several massive clay beds and clayey sand beds. Some of
the clay beds appear to be laterally continuous and, therefore, correlatable
between core holes (see geologic cross sections Figures 13-18).
The clay beds are dominated by kaolinite with montmorillonite and
palygorskite also present. Quartz sand, muscovite, and heavy minerals are
also common. The massive, dark gray to black nature of the clays, along
with commonly incorporated plant remains, implies a lagoonal or tidal flat
environment. Fossil material is not readily evident. However, diatoms were
found in abundance in several cores and well cuttings.
A mixture of fresh and marine water diatoms were identified from the
assemblage. This mixture of fresh and marine species, and species
associated with nutrient-rich waters near river outlets, fits well with the
environmental interpretation of a prograding delta slowly migrating over
and into the marine realm. These diatoms were only found near the present
coast at relatively shallow depths (Appendix I).
GRADED QUARTZ SANDS (Pleistocene ?)--n the central part of the
embayment in Franklin, Gulf, and southern Liberty counties, there is an
unconsolidated, poorly sorted, quartz sand and gravel unit. These sands
often exhibit graded bedding; and in some cores, forest beds are
apparent. There are sporadic, well-preserved wood fragments in these
gravel beds. Rapid deposition in a fluvial or deltaic environment is the
reason for the intact preservation.
This lithologic package represents the arrival of the clastic invasion
over the study area. The shallow water, brackish and marine environment
of the units deposited below this graded quartz sand have been displaced
south and southwest into the present Gulf of Mexico.
QUARTZ SAND RESIDUUM AND SOIL ZONE (Holocene)-The
clayey sands and silty sands that blanket the surface of the entire study
area represent reworked and winnowed sediments from the last retreat of
the sea. They are, generally, unconsolidated silty sands with recent root
accumulation in the present soil zone. They are terrestrial deposits with
coastal dunes and other coastal features which are common throughout the
near-shore area.

DISCUSSION
Due to poor preservation of marker species or the absence of zonable
fauna being present, time lines are not readily obtainable. As a result, a
direct correlation with the sea level curve of Vail et a]., (1977) and Vail and


56





BULLETIN NO. 58


Hardenbol (1979) cannot be attempted. There are, however, general trends
that can be observed because some stratigraphic horizons have been
zoned well enough to yield relative ages throughout the local geologic
section.
The Late Eocene Ocala Group limestones and the Oligocene
Marianna and Suwannee limestones represent a shallow, open marine
carbonate platform or shelf environment. From the elevation where they are
exposed in the panhandle, it can be concluded (without major tectonism)
that sea level was considerably higher than it is at present.
The Late Oligocene and Early Miocene Chattahoochee and St. Marks
formations seem to have a more prolific shallow water fauna than the older
units. A slight incidence of quartz sand and numerous shallow water
mollusks imply that the sea level may have dropped some from earlier
times.
The Bruce Creek Limestone (Middle Miocene) has much the same
fauna as the St. Marks Formation. There is a slight increase in quartz sand
and clay in the Bruce Creek. A very shallow environment near the end of
Bruce Creek deposition is suggested by the faunal evidence (including
abundant algal oncolites).
The Intracoastal Formation (Middle Miocene to Pliocene) represents a
reversal of this shallowing trend and was deposited in deeper water than
was the Bruce Creek. There is evidence that the coastal plain to the north
was highly eroded during Intracoastal time because there are abundant
elastic minerals present throughout the Intracoastal along with the open
marine fauna.
The Chipola and JacksoV Bluff Formations (Middle Miocene to latest
Pliocene) were probably deposited in near-shore, shallow marine
environments. Evidence for this are the numerous shallow water mollusk
assemblages and the abundance of plastics, including quartz sands, clays,
mica, and heavy minerals.
Overlying the Jackson Bluff are massive clays that were deposited in a
brackish or prodeltaic environment. Over the clays are fluvial or prodeltaic
sands and gravels. The sea level trend (although there have been several
Pleistocene fluctuations) is generally regressive after the Intracoastal
Formation.
This general trend is only a reflection of the regional lithologic
packages mapped throughout the embayment. There are numerous sea
level fluctuations recorded throughout the world from this time interval that
can only be observed through detailed paleontologic analysis which was
not attempted in this study.
Each of the cores taken near the central part of the Embayment
records the entire sequence of environmental changes that occurred in this
area from the Late Eocene to the Present. In moving up each core (going up
section), the pure limestone from the marine environment at the base of the
section becomes a slightly sandy limestone to a very clayey, sandy,
poorly-consolidated calcarenite, then to an unconsolidated, clayey shell
bed, to massive dark clays, and finally to fluvial or prodertaic sands. The


57






BUREAU OF GEOLOGY


MARINE
CURRENTS


EARLY
EOCENE


HOOCHEE


OLIGOCENE


APALACHICOLA v:::
EMBAYMENT



LATE
MIOCENE


". CLAST ICS
:CLASTICS! -t"""
, ,, ,.,


'I


II


________________________________________________________


'....^......J:.. ".:".''^


/ if
-4









LATE
EOCENE


EARLY
MIOCENE


PROGRADING '
DELTAIC INFILL





PLIO.
PLEIST.


Figure 20.


Generalized Paleogeographic Trend
(Eocene to Pleistocene).


58


m





BULLETIN NO. 58


plastic deltaic sequence can be observed to have slowly invaded the marine
environment and finally covered it, leaving the delta as we see it today
(Figure 20).

GEOLOGIC HISTORY OF THE APALACHICOLA
EMBAYMENT REGION

PRELIMINARY STRUCTURAL MAPPING
In preparing regional, structural contour maps of the top of the
Cretaceous, the Middle Eocene, the Late Eocene, the Oligocene, and Early
Miocene sediments, the author and Jim May (who was, at the time, on the
staff of the Northwest Florida Water Management District) noticed some
distinct recurring features. Two positive areas persisted throughout the
sequence. The first is the Ocala High east of the present study area in the
northwest part of the Florida peninsula and the other is in the
Chattahoochee Anticline in the Jackson, Holmes, and northern Washington
counties area.
Adjacent to each of these two positive or "high" areas are two low
areas. The first is in the western three-to-four counties of the state, along
the western flank of the Chattahoochee Anticline. This is the eastern-most
limit of the Gulf of Mexico Sedimentary Basin. The second is located
between the two relative high areas. In this region the typical southwesterly
dipping strata are slightly depressed, forcing the structural contour lines to
be deflected slightly northeastward. This feature is known as the
Apalachicola Embayment, and it is relatively minor in size when compared
to the more regional Gulf of Mexico Sedimentary Basin.
Mapping was generated from geologic well log and core descriptions
stored at the Florida Bureau of Geology in Tallahassee. There are many
problems inherent in using many different geologists' well log descriptions
(such as discrepancies in formation definitions, and formation contacts, age
assignments, etc.) as the data base for mapping. There were, however,
some noted differences in the various horizons mapped. The orientation
and placement of the gently plunging axis of the Apalachicola Embayment
shifts northwest higher in the section.
The discovery of this feature led to several questions relating to its
origin and its geological history. How did it originate? Was it a structural
feature (a graben)? Was it depressed from the thick sediment load, orwas it
due to non-deposition? The feature seemed to migrate. What was the
evidence for this? Why did its axis shift? Are there several different
structural elements present that are superimposed on each other,
compounding its interpretation? A literature search was carried out to
obtain as much information as possible.

LITERATURE REVIEW
The first point that becomes readily apparent in a literature review of
this topic is that many different names have been used in referring to this





BUREAU OF GEOLOGY


featuress. May (1977) addressed this norenclatural problem and
suggested the term Chattahoochee Embayment be used to refer to this
structural element in northwest Florida; May went on to summarize the
various names found in the literature, as shown in Table 7.

TABLE 7.-Nname used to describe the structural "low" feature near the Big Bend of
Florida (modified from May 1977).


AUTHOR
Johnson 1891
Dall and Harris 1892
Foerste 1893

Pressler 1947
Toulmin 1955
Braunstein 1957
Murray 1957
King 1961
Roberts and Vernon 1961
Herrick and Vorhis 1963
Sever 1966
Stringfield 1966


NAME
Chattahoochee Embayment
Suwanee Strait
Okefenokee Strait
Apalachicola Embayment of the Gulf
Basin
Apalachicola Embayment
Suwannee River Basin
Southwest Georgia Basin
Suwannee Basin
Southwest Georgia Embayment
Gulf Trough of Georgia
Gulf Trough
Apalachicola Basin


May (1977) preferred to use the term Chattahoochee Embayment
because it is the original name and should have priority. This author,
however, prefers to use the term Apalachicola Embayment for several
reasons: 1) Apalachicola Embayment is the term currently used by the
Florida Bureau of Geology, and it is used by most geologists familiar with
the area; 2) The oil and gas industry also uses this term and it is well
established in the literature; 3) Apalachicola (the city) is located
approximately on the axis of the embayment as it opens to the south; 4)
Chattahoochee (the city) is northwest of the embayment adjacent to a
positive structural feature; 5) The term Chattahoochee Anticline is used for
a positive structural feature next to the embayment; therefore, the use of the
same name for both an anticline and an embayment seems undesirable;
and 6) Chattahoochee is also the name of a local formation.
As would be expected with so many differing names and interpreta-
tions, there are also many differing opinions on the nature and origin of the
feature. Some have favored the hypothesis that a graben is responsible.
Others have preferred a downfaulted embayment, a syncline, a solution
valley, a submarine valley, or a current-swept strait. When several.axial
plots are combined from different authors (Figure 21), a wide range of
orientations and locations are apparent. The immediate question that
arises is: Are these various authors mapping different features, or do their
stratigraphic interpretations differ that much from one another? This type of
confusion has resulted in one paper being entitled Chattahoochee
Anticline, Apalachicola Embayment, Gulf Trough and Related Structural


60





BULLETIN NO. 58


I
C
,----- L.ii


*1*p


AXIS OF 'LOW AREA"
COMPILED FROM NUMEROUS
PUBLICATIONS


Figure 21. Axis of "Low Area" as interpreted by various authors.
a. Chen (1965), Applegate (1978), Pontigo (1982)
b. Herrick and Vorhis (1963), Cramer (1974), Arden (1974)
c. Toulmln (1952), Weaver and Beck (1977), May (1977)
d. Chen (1965)
e. Applin and Applin (1944, 1967), Hull (1962)
f. Applin and Applin (1967)
g. Chen (1965)



Features, Southwestern Georgia, Fact or Fiction (Patterson and Herrick,
1971).
Depending on which stratigraphic horizon was being mapped or what
geographic area was studied, various authors interpreted the origin and
geological history of the feature differently. Some (Outler, 1979; Pontigo,
1979; Applegate et a., 1978; Cramer, 1974; Arden, 1974; Herrick and
Vorhis, 1963; Hull, 1962; and Applin and Applin, 1944, 1967) studied the
Mesozoic sediments, placed an axis through Port St. Joe, and implied that a
graben caused the sediment thickening. Some (Gelbaum and Howell,
1979; Weaver and Beck, 1977; May, 1977; Chen, 1965; and Toulmin, 1952)
studied the Paleogene horizons and plotted their axes farther east and
interpreted that little or no deposition was due to a current-swept strait.
Finally, other authors studying the Neogene (Banks and Hunter, 1973;





BUREAU OF GEOLOGY


Toulmin, 1952; and Schmidt, this paper) discussed sediment infill of an
embayment or basin by a prograding, plastic deltaic sequence.
The variety of names used Is explained by the fact that differing
horizons were studied and various locations plotted. Each author chose a
surface feature in the vicinity of the low axis, as interpreted by that author to
name the subsurface feature. In addition, depending on the area extent of
their study, writers would choose to call the depressed sediments a basin,
embayment, strait, or trough.
This varied and confusing summary of geologic interpretations can be
sorted out and historical trends postulated, if the various data can be put in a
chronological sequence. Unpublished information from the Florida Bureau
of Geology files were used to verify and check the many formational
contacts.

SEQUENTIAL TRENDS FROM THE PRE-JURASSIC
TO THE RECENT
The earliest indication of a depression is evidenced by the top of the
pre-Jurassic surface. Arden (1974) shows a plunging axis (Figure 22) to dip
approximately southwest towards souther Gulf County from the southwest
corner of Georgia. Arden considered this feature a tensionally controlled
Late Triassic "down-warp" forming a broad basin. Subsequent to the
development of this "syncline", further crustal tension created high-angle
fractures, and a series of fault block basins appeared into which Triassic
sediments began to be deposited. This interpretation was developed by
Arden using seismic reflection surveys with associated gravity and vertical
magnetic field measurements. Pontigo (1982) seemed to agree with Arden
when he stated that the Apalachicola Embayment was initiated as a result
of rifting during Late Triassic to Early Jurassic times associated with the
opening of the Atlantic Ocean. Pontigo used well cuttings, geophysical well
logs, and seismic reflection lines as his data base. Seismic lines show
graben structures in basement reflections. A diabase intrusion in the Eagle
Mills Formation (Triassic), dated as 180-200 million years (Barnett, 1975),
provides a minimum age for the tensional features observed.
A structure contour map of the sub-Zuni erosional surface (approxi-
mately during the Early Jurassic) shows an embayment in the same vicinity
as Arden's map (Bamett, 1975). Barnett also plotted several faults on that
surface, including some in the Apalachicola area. Two of his faults which
form a graben have been further documented by Pontigo (1982), who used
better well control, In addition to seismic lines. Contour maps on top of the
Norphlet Formation and several lithofacies in the Smackover Formation
(both Late Jurassic) show the graben opening towards and centered
around Gulf County and cutting into these Upper Jurassic formations
(Pontigo, 1982). This may imply that structural activity continued through
the Jurassic. From petrographic studies of these units, Pontigo concluded
that the open sea was to the south with a possible exposed region to the
north.
The Late Jurassic in this area is represented by the Cotton Valley


62






BULLETIN NO. 58


group. This group consists of mudstones and coarse sandstones and, as
depicted on a structural cross section by Applegate et al. (1978), the
embayment still existed through the end of the Jurassic (Figure 22). Herrick
and Vorhis (1963) and Cramer (1974) mapped what was termed the
pre-Cretaceous in southwest Georgia. Their maps showed the same trend
of the embayment with its axis plunging towards the Gulf County area of
Florida (Figure 22).
The Lower Cretaceous in the Apalachicola Embayment consists of
sales and sandstones varying from about 4,200 feet to 5,800 feet in
thickness. A structural cross section prepared by Applegate et a. (1978)
shows the Lower Cretaceous thickest near the axis of the embayment. It
also shows the embayment was filled in by the end of the Early Cretaceous.
This is also shown by Outler (1979) and Pontigo (1979) on the structure
contour maps prepared on the top of the Lower Cretaceous. Their maps
show the regional dip of the beds to the south-southwest but do not have
deflections in the contours to form an embayment. It is inferred here that
subsidence had ceased or the sedimentation rate exceeded the rate of
subsidence due to either compaction or the structural graben below.
Applin and Applin (1967) mapped the pre-Gulf rocks (the top of the
Lower Cretaceous) throughout northern Florida, and their interpretation is
in agreement with Outler (1979) and Pontigo (1979) in that the embayment
is no longer present but apparently filled in. Applin and Applin (1967) do,
however, show an embayment shifted eastward from the prior feature
(Figure 22). The axis of this low also plunges towards southern Gulf County;
but instead of rising towards the southwest corner of Georgia, it rises nearly
due east, then turns northeast and runs along eastern Leon County,
Florida, into Georgia, then turns east again. There it plunges towards
southeast Georgia where geologists name the feature the Okefenokee
Embayment. Between the Apalachicola and Okefenokee embayments,
there is a relative high area (that separates the two low features) which the
Applins called the Suwannee Saddle. This low structure, that seems to
connect the northeast Gulf with the coastal Atlantic, was first noted by Dall
and Harris (1892) who named the feature the Suwanee Strait. They
concluded that this feature separated the continental border from the
islands representing Florida (Dall and Harris did, however, discuss this as
an Eocene and Miocene feature).
The top of the Upper Cretaceous sediments was mapped by Applin
and Applin (1944, 1967), Hull (1962) and Chen (1965) (Figure 22). Their
work not only showed the structure from contour mapping but they inferred
paleogeographic relationships with the addition of isopach maps and
lithofacles maps. Hull interpreted the thin Upper Cretaceous rocks as an
area of slow sedimentation. He felt this was an area that separated the
carbonate banks on the south from the source of terrigenous sediments on
the north. Hull further stated, "This thinness, which is generally attributed to
Post-Cretaceous erosion, can be explained as a result of differential
sedimentation during Late Cretaceous time, when the Suwannee strait was
a boundary between two distinct sedimentary facess"







BUREAU OF GEOLOGY


}


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Figure 22. Sequential plots of the axis of the Embayment, Pre-Jurassic to
Pleistocene. (Pattern on 10 and 13 represents area exposed
above sea level.)








BULLETIN NO. 58






















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BUREAU OF GEOLOGY


Applin and Applin (1967) offered an alternative interpretation. They
thought this area represented an upwarped barrier that separated the two
provinces during the latest Cretaceous time. During Tertiary time, tectonic
movements in Florida and Georgia brought about a relative depression of
the uplift area (the barrier), forming the synclinal feature now seen in the
stratigraphy.
The top of the Paleocene was mapped by Chen (1965) as part of his
regional lithostratigraphic analysis of Paleocene and Eocene rocks in
Florida. Chen showed a synclinal axis (termed the Suwannee Channel)
rising from the south Gulf County area towards the east-northeast, then
shifting northeast until reaching the Florida-Georgia state line, thereafter,
turning east-northeast again (Figure 22). Chen also showed, by use of a
Isopach map, the thin accumulation within the Suwannee Channel during
the Paeocene. The location of the syncline as mapped by Chen (1965) is
very close to the syncline as mapped by Applin and Applin (1967) from the
top of the Lower Cretaceous. This implies a long, stable presence of the
feature from Early Cretaceous through the Paleocene. Chen (1965)
suggests that this relatively thin deposition within the channel is from
continued strong current action during that time. The currents could have
considerably reduced the rate of sediment accumulation within the channel
and would have prevented the spread of terrigenous sediments over the
peninsula to the southeast.
The Eocene series has received more attention by geologists than the
older sees, partially because of an increased data base in the more
shallow sediments. Toulmin (1952), Chen (1965), Weaver and Beck
(1977), and Gelbaum and Howell (1979) all mapped Eocene horizons in
north Florida (Figure 22). Chen (1965) mapped contours on top of the
Lower Eocene, the Middle Eocene, and the Upper Eocene. From that data,
(isopach maps and lithofacies maps) Chen developed a regional
paleogeographic interpretation of the Suwannee Channel during Late
Cretaceous and Early Tertiary time. He stated that "... the Suwannee
Channel was a bathymetric depression and a natural barrier, both
sedimentational and ecologic, during Late Cretaceous and Early Tertiary
time." By Middle and Late Eocene time, the channel was no longer an
effective barrier in separating the plastic and nonclastic faces. The axis of
the channel and facies boundary shifted northwestward through the
Eocene (Figure 22). By the end of the Eocene, the axis shifted west and
plunged towards Gulf County from the southwest corner of Georgia. This
location and orientation is very close to the Triassic and Jurassic position of
the axis (Figure 22).
The upper surface of the Oligocene series was mapped by Toulmin
(1952), May (1977), Weaver and Beck (1977), and Gelbaum and Howell
(1979). The structural map of the Oligocene is based on the top of the
Suwannee Umestone by most authors. The structural maps show the
synclinal axis to be similar to that of the top of the Eocene in general
configuration. There does, however, appear to be a relative high in the
trough. The Apalachicola Embayment is separated from the "trough" in


66





BULLETIN NO. 58


southwest Georgia. This high or "sill" has also been projected higher in the
section into the Early Miocene (Tampa Stage) sediments by Weaver and
Beck (1977). There is no way to determine the width of the "sill" from
available well control.
If this relative high in the embayment-trough existed at the close of the
Oligocene and during the Early Miocene, it may have acted as a bridge to
transport clastics across the barrier channel. This was postulated by Banks
and Hunter (1973) (Figure 22), although their "land bridge" is considerably
farther south than would be called for by the interpretive stratigraphic data.
The post-Early Miocene sediments throughout the Florida peninsula are
dominated by terrigenous clastics, whereas prior sediments are predomin-
ately nonclastics (limestones, dolomites, and evaporites). This observation
seems to support a "bridging" of the barrier channel or at least a diminished
barrier effect by the Suwannee Current after Oligocene time.
The Miocene of the southeastern United States has been studied by
many authors (too numerous to list here). Studies by Weaver and Beck
(1977) and Riggs (1980) included regional paleogeographic maps of the
area. Weaver and Beck connect the Gulf of Mexico with the Atlantic Ocean
by means of a narrow trough near Gadsden County, Florida, that connects
the Apalachicola Embayment with the southeast Georgia area which they
call the Atlantic Embayment. The high "sill" in Gadsden County separates
the Apalachicola Embayment from the trough area of the Atlantic
Embayment.
Riggs (1980) also showed this same trough. Northwest of the trough is
a terrigenous system labeled the Apalachicola Delta. Southwest of the
trough are numerous shallow marine depositional basins.
The axis of the Apalachicola Embayment in the study area during
Middle Miocene Is shown on Figures 6 and 22.
The Late Miocene to Pliocene sediments have not been mapped
throughout the area prior to this study. The structure contours prepared on
the top of the Intracoastal Formation (Figure 9) and the Jackson Bluff
Formation (Figure 10) define the orientation and relief of the synclinal axis
on the respective horizons. It should be noted that the location of the axis
seems relatively permanent after the latest Eocene. Also, the relief of the
feature is less on the younger units, indicating that the embayment was
filling in. When the Ollgocene "sill" blocked the Suwannee Channel, the
marine current was impaired so that lower velocities allowed sediment
accumulation to take place. As more and more sediment filled in, the marine
communication ceased between the Gulf and the Atlantic. From the Middle
Miocene to the present, clastics filled in and began to prograde south. This
Is evident from the geologic cross sections and the geologic columnar
sections in Appendix III.

STRUCTURAL HISTORY OF THE
APALACHICOLA EMBAYMENT
From the preceding discussion, a generalized summary of the
structural history of the Apalachicola Embayment can be formulated. An


67





BUREAU OF GEOLOGY


embayment or low area existed in the Late Jurassic and Early Cretaceous
and originated as a basement graben. This low area filled with sediments
during the Jurassic and Early Cretaceous, and by the end of the Early
Cretaceous was completely filled. This is evident from the down-to-Gulf dip
of the overlying sediments with no deflection of the structural contours. The
top of the Lower Cretaceous shows a synclinal axis again but shifted
eastward. This feature is probably due to nondeposition in a current-swept
strait. The synclinal axis of this channel migrated westward until the
Oligocene when it became located in the central Gadsden County area and
dipped towards Gulf County. From Early Miocene until the Recent, the low
feature slowly filled in and, in Pleistocene to Recent times became covered
by the prograding Apalachicola River delta.
This simplified history is graphically illustrated in Figure 23. It seems
the Neogene axis was situated over the Jurassic axis, with no apparent low
or embayment in between. The deeper feature originated structurally,
whereas the Paleogene-Neogene feature was due to slow deposition from
a current-swept strait. It is probable, then, that the superimposition of the
Jurassic and Cenozoic axis is concidental,
TERTIARY STRUCTURAL MOVEMENTS
Some authors feel that a graben is responsible for the Late Tertiary
feature, although none have presented convincing evidence for the
existence of faulting on a downthrown central block. Moore (1955), on the
basis of a faunal discontinuity in three wells, postulated the Cypress Fault in
Jackson County, Florida. Schmidt and Coe (1978) did not include a fault in
their interpretation of the local stratigraphy. They did not rely on the faunal
assemblage and contoured the formational units without a fault in their
solution. Patterson and Herrick (1971) also reviewed the Cypress Fault and
felt proof of such a fault was inadequate.
Sever (1966) cited a fault in the Thomas County area of Georgia. The
Ochlockonee Fault, as named by him, was based on structure contour
maps of the Suwannee and Tampa limestones. The current writer redrew
these contour maps, using Sever's formation picks, and finds no reason to
include a fault in the interpretation. Patterson and Herrick (1971), also
looked at these data and stated "this fault is no more than a hypothetical
possibility."
Another fault, the Bainbridge-Chattahoochee-Blountstown Fault of
Tanner (1966), was also questioned by Patterson and Herrick (1971).
Tanner uses surface physiography and "llnears" as evidence for
"dislocations." Core and well cuttings described by the author do not
support offsets in the proposed areas.
Finally, Gelbaum and Howell (1979) hypothesize that "gravity faulting"
along with downwarping caused the sediment thickening. They also point
out that sediment infilling "healed" or "disguised" most fault traces. Their
conclusions also are highly interpretive.


68





BULLETIN NO. 58


RECENT


TERTIARY


MID
CRETACEOUS



LATE
JURASSIC


SPRE
JURASSIC


Figure 23. Simplified Structural History of the
Apalachicola Embayment.


69





BUREAU OF GEOLOGY


From the foregoing discussion it is obvious that the origin of the trough
in Tertiary times is not well-defined. The interpretations which rely on
faulting, although possible, can not be documented using available data. As
a result, the paleogeographic interpretation of a strait or Tertiary channel
comparable to the present Florida Strait is preferred.

CONCLUSIONS
1. The downdip Neogene lithologic units along the coast of Panhandle
Florida are different lithologic packages from the contemporaneous units
exposed undip.
2. These units can be defined and mapped using well cuttings, cores,
and geophysical well logs.
3. The Upper Eocene Ocala Group limestones identified are generally
penetrated only by deeper water wells. The three formations of the Ocala
Group cannot be differentiated, and, as a result, the unit is referred to as
Ocala Group undifferentiated.
4. Although not present along the coastal areas of West Florida, the
Oligocene Marianna Limestone is present in the northern, updip parts of the
Apalachicola Embayment.
5. The Oligocene Suwannee Limestone is present throughout the
study area. It is generally the deepest formation penetrated by water wells.
In the western part of the study area, the formation is undifferentiated from
the downdip Chattahoochee Formation.
6. The Chattahoochee Formation, an Oligocene-Miocene unit, is
present in the updip northern parts of the Embayment. In the western and
southern parts of the study area, it is indistinguishable from the Suwannee
Limestone.
7. The St. Marks Formation (Early Miocene) is present on the eastern
flank of the Apalachlcola Embayment. Downdlp towards Gulf County, the
St. Marks cannot be distinguished from the younger Bruce Creek
Limestone.
8. The Bruce Creek Limestone is a Middle Miocene formation, present
downdip throughout the embayment. The unit can be mapped using cores
and well cuttings. It is predominantly a subsurface unit. Faunal and
lithologic evidence suggest it was deposited under shallow, near-shore
marine conditions. The top of the Bruce Creek Formation contains a zone
rich in algal oncolites. This implies a shallowing of the water depth near the
end of Bruce Creek deposition.
9. A clayey dolosilt bed is present over the Bruce Creek Limestone in
the central and eastern parts of the embayment. This massive unit may
have been deposited In a supratldal or tidal flat environment. The massive,
clayey nature of this bed is probably important for its hydrologic
implications. This clay would act as an aquiclude and create artesian
conditions in the underlying Bruce Creek Limestone.
10. The Intracoastal Formation is a Miocene-Pliocene unit. It is
mappable throughout the embayment area and is the downdip equivalent of


70





BULLETIN NO. 58


the exposed Alum Bluff Group and Jackson Bluff Formation. The
Intracoastal is richly microfossiliferous and was estimated to have been
deposited under marine conditions in less than 623 feet of water. The
diverse group of marine organisms present, along with a significant amount
of quartz sand, heavy minerals, clays, glauconite, and phosphate, leads to
the conclusion that the Intracoastal was seaward (shallow shelf) of a fluvial
source. High amounts of nutrients from the exposed coastal plain to the
north may have contributed to the high biological productivity in the area.
11. The Chipola formation has been mapped into the subsurface,
downdip of the "type" area. It has been dated as Middle Miocene from
fossiliferous outcrops. Downdlp it is considered time-transgressive and is
estimated to be Late Pliocene.
12. The Jackson Bluff Formation has been mapped into the
subsurface, downdip of the "type" area. It has been dated Late Pliocene
from outcrops. Downdip It is estimated to extend into the Pleistocene.
13. Overlying the Jackson Bluff Formation are clay, clayey sand,
quartz sand, and gravel beds. These sediments represent the plastic
invasion of the fluvial delta over the shallow marine environment.
14. The massive clay beds appear to be correlative locally. They have
yielded diatoms near the present coast. The fauna includes fresh-water and
marine diatoms, and species associated with nutrient-rich waters near river
outlets. This indicates a prograding delta during the time of deposition.
Identified diatoms are found commonly in Pleistocene to Recent sediments.
15. Coarse quartz sands and gravels are common in the central part of
the embayment. This unit is locally correlative, and represents the final
stage in the fluvial elastic invasion over the shallow marine environment.
The sand and gravel beds exhibit coarsening-upward sequences and
unidirectional cross-bedding. The cross-bedding is tentatively correlated
with prodeltaic forest beds. The coarse sands and gravels may locally be a
shallow, fresh water source for domestic supplies. They also could be used
as source of aggregate for the construction industry, although at present the
area is considerably distant from population centers.
16. The synclinal axis for the embayment was established during
Middle Miocene, Early Pliocene, and Late Pliocene times.
17. The approximate updip limits of deposition for the Neogene
Formations were estimated.
18. Late Tertiary and Quaternary paleoenvironmental trends were
estimated. This was accomplished using the literature, identified fauna,
sedimentary characteristics, and lithologic components.
19. The nomenclatural history and interpretive history of the
Apalachicola Embayment was summarized. It was concluded that the
embayment originated from a graben during pre-Jurassic times. The low
area slowly filled with sediments and was filled by the end of the Early
Cretaceous. A synclinal axis re-appeared at the top of the Lower
Cretaceous series, but it was shifted eastward 50 or more miles. Through
the Tertiary, this axis migrated westward until the Oligocene when it was
once again aligned over the Jurassic-Cretaceous feature. The latter





72 BUREAU OF GEOLOGY

migrating feature is interpreted as a current-swept marine strait similar to
the present Florida Strait. During Miocene times, the strait was bridged or
"pinched off" due to the northwestward migration of the Florida carbonate
platform and the southeastward migration of the clastics from the north.
From Pliocene to Pleistocene times, the embayment slowly filled with
sediment, until at present it is completely filled again and, therefore, no
longer exists.





BULLETIN NO. 58


REFERENCES
Akers, W. H., 1972, Planktonic Foraminifera and Bistratigraphy of Some
Neogene Formations, Northern Florida and Atlantic Coastal Plain:
Tulane Studies in Geol. and Paleo. V. 9, 140 p.
and Koeppel, P. E., 1973, Age of Some Neogene Formations,
Atlantic Coastal Plains, United States and Mexico: in Symposium on
Calcareous Nannofossils, Proceedings, Gulf Coast Sect., Soc. Econ.
Paleontol. Mineral., Houston, Texas, pp. 8-93.
Applegate, A. V., Pontigo, F. A. Jr., and Rooke, J. H., 1978, Jurassic
Smackover Oil Prospects in the Apalachicola Embayment: The Oil and
Gas Journal, January, 1978, V. 76, N. 4, pp. 80-84.
Applln, Paul L., 1951, Preliminary Report on Buried Pre-Mesozoic Rocks in
Florida and Adjacent States: U.S. Geol. Survey Circular 91, 28 p.
and Applln, Ester R., 1944, Regional-Subsurface Stratigraphy
and Structure of Florida and Southern Georga: Am. Assoc. Petrol. Geol.
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pp. 199-421.


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Bolli, H. M., 1957, Planktonic Foraminifera from the Ofigocene-Miocene
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9, 147 p.


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1976b, The Neogene Stratigraphy of the Central Florida
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(abstract).


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Sand Hunter, Muriel E., 1982, Stratigraphic Revision of the
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Second Annual Report, pp. 25-173.


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May, J. P., 1977, The Chattahoochee Embayment: Southeaster Geology,
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Florida Panhandle: Fla. Geol. Survey Bull. 36, 345 p.


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_, 1957, Stratigraphy and Zonation of the Ocala Group: Fla. Geol.
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1-234.


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and Beck, Kevin C., 1979, Environmental Implications of
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p.


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APPENDIX I

Diatoms from the Pleistocene Clay Beds


81
















12177 2 40'-40
0 1 I13209 C

,2' 14 35 1-0




4928-WELL NUMBER
'-e8'-DEPTH BELOW SEA LEVEL
OF DIATOMACEOUS INTERVAL





Figure 24. Well cuttings and cores from which diatoms were found in the
Pleistocene clay beds. U





BUREAU OF GEOLOGY


PLATE 1
W-14535 90-100 ft.

1. 1200x Epithema argus
Marine calcium carbonate mode
2. 1200x Epithemia ocelata
Fresh water, moderately high conductance
3. 1200x Epithemia ocellata
4. 1200x Rhoptodia gibba
Water with high conductance
5. 1200x Rhoplodia gibba
Fragment


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' 4


PLATE 1.
Diatoms


_ _ __ ________ __ __


_ ________ ___ __________ ___


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BUREAU OF GEOLOGY

PLATE 2
W-14535 90-100 ft.


1. 1200x

2. 1200x

3. 1200x

4. 1200x


Cycotella strata
Fresh water, river washouts in marine environment
Synedra ulna
Fresh water
Actinocyclus octonarus
Marine waters
Dfpnels smithfi
Marine benthic


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BULLETIN NO. 58


PLATE 2.
Diatoms


__ __ _ _ I_ I __ ________ __1_


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PLATE 3
W-14535 140-150 ft.

1. 300x Actinocyclus octonarius
Marine waters
2. 1200x Cocconeis placentulia
Fresh to brackish waters
3. 1200x Gomphonema parvulum
Fresh, nutrient-rich waters
4. 1200x Cymbella minute
Fresh waters
W-7378 32.5 ft.

5. 300x Eupodiscus radiatus
Marine waters


88