The Neogene of Florida and adjacent regions

Material Information

The Neogene of Florida and adjacent regions proceedings of the third Bald Head Island Conference on Coastal Plains Geology : Hilton Head Island, November 4-8, 1992
Portion of title:
Proceedings of the third Bald Head Island Conference on Coastal Plains Geology
Zullo, Victor A., 1936-
Florida Geological Survey
Bald Head Island Conference on Coastal Plains Geology, 1992
Place of Publication:
Tallahassee, Fla.
Florida Geological Survey
Publication Date:
Physical Description:
x, 112 p. : ill., maps ; 28 cm.


Subjects / Keywords:
Geology, Stratigraphic -- Congresses -- Neogene ( lcsh )
Geology -- Congresses -- Florida ( lcsh )
City of Tampa ( local )
Sarasota County ( local )
Fauna ( jstor )
Coastal plains ( jstor )
Sediments ( jstor )
bibliography ( marcgt )
government publication (state, provincial, terriorial, dependent) ( marcgt )
non-fiction ( marcgt )
conference publication ( marcgt )


General Note:
Florida Geological Survey special publication number 37
General Note:
At head of title: State of Florida, Department of Environmental Protection, Division of Resource Management, Florida Geological Survey.
Statement of Responsibility:
edited by Victor A. Zullo, W. Burleigh Harris, Thomas M. Scott, Roger W. Portell.

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University of Florida
Holding Location:
University of Florida
Rights Management:
All applicable rights reserved by the source institution and holding location.
Resource Identifier:
32630108 ( OCLC )
95622279 ( LCCN )
0085-0640 ; ( ISSN )

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University of Florida


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c .2

Virginia B. Wetherell, Secretary

Jeremy A. Craft, Director

Walter Schmidt, State Geologist and Chief




Hilton Head Island, November 4-8, 1992

edited by:
Victor A. Zullo
W. Burleigh Harris
Thomas M. Scott
Roger W. Portell

Published for the



Governor Lawton Chiles
Florida Department of Environmental Protection
Tallahassee, Florida 32301

Dear Governor Chiles:

The Florida Geological Survey, Division of Resource Management, Department
of Environmental Protection, is publishing as its Special Publication 37, The Neogene
of Florida and Adjacent Regions Proceedings of the Third Bald Head Island
Conference on Coastal Plains Geology. This volume is a collection of papers by
geologists currently investigating the Neogene of this region. Knowledge of these
deposits allows geologists to better understand the geological resources of the state
and its geological history.

Respectfully yours,

Walter Schmidt, Ph.D., P.G.
State Geologist and Chief
Florida Geological Survey

Printed for the
Florida Geological Survey


ISSN 0085-0640



During the preparation of the Third Bald Head Island Conference proceedings volume, Vic Zullo passed
away unexpectedly. Vic was one of the driving forces behind the Bald Head Island Conferences and
was instrumental in involving others in the conference process. The Bald Head Island Conferences will
continue but Vic's enthusiasm and input will be greatly missed. The editors of this volume dedicate
the Florida Geological Survey's Special Publication 37, "The Neogene of Florida and Adjacent Regions"
to the memory of our colleague and friend Vic Zullo.

* -. .:

'. '. .- .. .-...


The Third Conference is dedicated to Charles L. Cahill, first Provost and Vice Chancellor for Academic
Affairs of The University of North Carolina at Wilmington, whose strong support and continued
encouragement made the concept of these Conferences a reality. This conference is also dedicated
to the memories of Juergen Reinhardt and Norman Sohl, friends, colleagues, and participants of the first
two conferences.

Financial support for the Third Bald Head Island Conference, a continuing program of The University
of North Carolina at Wilmington, was provided by The University of North Carolina at Wilmington and
the Florida Geological Survey.


W. Burleigh Harris
University of North Carolina
Wilmington, North Carolina

Thomas M. Scott
Florida Geological Survey
Tallahassee, Florida

Roger W. Portell
Fla. Museum of Natural History
Gainesville, Florida

Victor A. Zullo
University of North Carolina
Wilmington, North Carolina


Warren D. Allmon
Paleontological Res. Institute
Ithaca, New York

Donald J. Colquhoun
University of South Carolina
Columbia, South Carolina

John S. Compton
University of South Florida
Tampa, Florida

J. Mitchener Covington
Florida Geological Survey
Tallahassee, Florida

W. Burleigh Harris
University of North Carolina
Wilmington, North Carolina

Thomas M. Missimer
Missimer & Associates, Inc.
Cape Coral, Florida

Gary S. Morgan
Fla. Museum of Natural History
Gainesville, Florida

Edward J. Petuch
Florida Atlantic University
Boca Raton, Florida

Roger W. Portell
Florida Museum of Nal
Gainesville, Florida

Victor A. Zullo
University of North Carolina
Wilmington, North Carolina

Stanley C. Riggs
East Carolina University
Greenville, North Carolina

Thomas M. Scott
Florida Geological Survey
Tallahassee, Florida

Scott W. Snyder
East Carolina University
Greenville, North Carolina

Lauck W. Ward
Virginia Museum of Nat
Martinsville, Virginia

Sherwood W. Wise
Florida State University
Tallahassee, Florida

Victor A. Zullo
University of North Carolina
Wilmington, North Carolina




Paul F. Huddlestun
Georgia Geologic Survey
Atlanta, Georgia

Douglas S. Jones
University of Florida
Gainesville, Florida



D education . . .. . .. . . .. . .. . .. . .. . .. .. .. .. . . . . iv

Conference Dedication and Acknowledgements ............ ................ v

List of Participants and Contributors . ............. ...................... vi

Neogene lithostratigraphy of the Florida Peninsula problems and prospects, by
Thomas M. Scott . ........................ .................. 1

Problems in application of sequence stratigraphy to the Florida Neogene, by
W. Burleigh Harris and Victor A. Zullo ................................ 3

8Sr/86Sr geochronology of Oligocene and Miocene marine strata in Florida, by
Douglas S. Jones, Paul A. Mueller, David A. Hodell, and Laura A. Stanley ...... 15

The use of Strontium isotopes to sort out the complex diagenetic and depositional
history of phosphorite deposits on the Florida Platform, by John S. Compton,
David A. Hodell, and David J. Mallinson ............................. . 27

Pliocene stratigraphy of South Florida: Unresolved issues of facies correlation in
time, by Thomas M. Missimer ....................... .............. 33

Neogene nannofossils of Florida, by J. Mitchener Covington ................ 43

Neogene nannofossil biostratigraphic framework for the northwest Florida carbonate
ramp slope, by Sherwood W. Wise, Jr., Sandra Dee Weiterman, Anne F. Gardulski
and Henry T. Mullins ....... .......... ......... .......... ..... 45

Paleobiogeography of the late Cenozoic barnacle fauna of Florida, by
Victor A. Zullo and Roger W. Portell .................................. 47

Mammalian biochronology and marine-nonmarine correlations in the Neogene of
Florida, by Gary S. Morgan ......................... ............ 55

Do Florida's Plio-Pleistocene shell beds have large-scale paleobiological
significance? by W arren D. Allmon ................................. 67

Patterns of gastropod extinction in the Plio-Pleistocene Okeechobean Sea of
southern Florida, by Edward J. Petuch ............................... 73

Pliocene stratigraphy and biostratigraphy, Virginia to Florida, by
Lauck W W ard ...... ......................................... 87


An overview of the Neogene of Georgia, by Paul F. Huddlestun .............. 91

Observations of the petrology, depositional setting, stratigraphy and structure
of the Upland unit (Citronelle Formation of Doering, 1960, or Hawthorne Formation
of Siple, 1967), along the southeastern Atlantic Coast regional cross section (DNAG
E-5 Corridor) and near Charleston, Georgia and South Carolina, by Donald J.
Colquhoun, Arthur Cohen, Michael Katuna, James Rine, Marylin Segall and
M ichael W addell .............................................. 97

Translating biostratigraphic and high resolution seismic data into a sequence
stratigraphic framework insights gained from study of the North Carolina
Neogene, by Scott W. Snyder and Stephen W. Snyder .................. 103

Sr isotopic analysis of phosphate peloids through multiple sea-level cycles:
Testing the depositional model for the North Carolina continental margin,
by Stanley C. Riggs, Peter Stille, and Norbert Clauer ................... 107

Participants and Presentations, First and Second Conferences ........... 111-112



Florida Geological Survey, 903 W. Tennessee Street, Tallahassee, Florida 32304-7700

A dramatic shift in sedimentation patterns
marks the beginning of the Neogene in Florida.
Prior to the Neogene, carbonate sedimentation
dominated the depositional environments in
Florida and much of the southeastern United
States. Changes in the erosional rates in the
Appalachian Mountains, as a result of a broad
uplift in the late Paleogene, contributed a
tremendous influx of siliciclastic sediments.
This change in sediment supply coupled with
the final disappearance of the Gulf Trough
allowed the siliciclastic sediments to be
transported on to the Florida Platform,
eventually replacing carbonates as the dominant

Siliciclastic sediments first appear in the
Lower Miocene section of northern Florida inti-
mately mixed with carbonate sediments and as
thin, discrete beds. In southern Florida,
carbonate sedimentation continued to dominate
through much of the Miocene before giving way
to siliciclastic deposition. In the Keys,
siliciclastic sedimentation may not have become
dominant until early in the Pliocene.

Two important aspects of Florida's
Neogene section have focused the attention of
geologists on these sediments. First is the
occurrence of phosphate both as an
economically important deposit and as a
uranium-bearing mineral with important health
implications. Second is the occurrence of well
preserved, diverse mollusk faunas in Florida's
Pliocene sediments.

Phosphate, in the form of the mineral
francolite (carbonate fluorapatite), forms a
common accessory component of the Neogene
sediments in Florida including the formations of
the Hawthorn Group and the Tamiami
Formation and equivalents. In several areas of
the state, phosphate is sufficiently concentrated
by post-depositional reworking to be mined. As
a result of uranium incorporated in the
mineralogical structure of the francolite,
radioactive decay to radon can cause significant

health hazards for individuals living and working
in high radon concentration environments.

For many years the well preserved
molluscan faunas of the Florida Pliocene have
been cherished by paleontologists. Due to the
general lack of good exposures and the
availability of the mollusk faunas from canal
and dredge spoil and a few rivers, many
Neogene units were originally described based
upon the incorporated faunas. These units
were then equated with sediments found
elsewhere in the Coastal Plain and assigned an
age based solely on the fossils.

The Neogene stratigraphic section in
peninsular Florida remains poorly understood as
a result of the near complete lack of acceptable
exposures. The vast majority of our knowledge
of the Neogene section stems from subsurface
investigations; in particular from those inves-
tigations utilizing cores. Unfortunately, many
subsurface investigations focused on the
Floridan aquifer system and consider the
Neogene section simply overburden.

The most important problem facing those
who study the Neogene section in the Florida
peninsula is the scarcity of biostratigraphically
important microfossils. Within portions of the
Neogene section, fossils, if they were ever
present, have been obliterated by pervasive
diagenesis. In the fossiliferous sections,
microfossils are often the long ranging,
environmentally tolerant species of little to no
biostratigraphic significance. Obviously, this
has lead to some misinterpretations of the

A good example of the importance of the
microfossils in assisting in refining the
interpretation of the stratigraphic section occurs
with respect to the Venice Clay, a hydro-
stratigraphically important unit in southwestern
Florida. This unit was originally defined as the
lower portion of the Tamiami Formation which
is now recognized as Pliocene. Microfossil data


(McCartan, personal communication, 1992)
suggests that the Venice Clay is Early to Middle
Miocene. Based on the phosphatic carbonate
lithologies associated with the clay bed, the
Venice Clay should be interpreted as part of the
Arcadia Formation, Hawthorn Group.

Another major problem appertains to the
molluscan faunas upon which the Pliocene
"formation" and "members" are often based.
Historically, the Pliocene units in the coastal
plain have been based on the recognition of
specific faunas and "guide fossils". Beyond the
numerous problems associated with assuming
the continuities of faunas from Maryland, for
example, to southern Florida, acquiring a
representative sample for faunal analysis by
drilling is nearly impossible.

Attempts to define the Florida Neogene
section sequence stratigraphically have been
hampered by the paucity of biostratigraphically
significant faunal elements upon which
sequences can be dated (W. B. Harris and V. A.
Zullo, personal communication, 1992). Recent
paleontologic efforts have identified some
nannofossil zones present in cores from
southwestern Florida (J. M. Covington,
personal communication, 1992) which provide
an initial base for determining sequence ages.

The extended database of cores and
mining exposures in the Florida peninsula is
realistically quite limited, containing some 400
cores and, perhaps, several dozen pits. Cores
penetrating the Neogene section are
concentrated in the northeastern, central and
southwestern peninsula. In general, large areas
of southern Florida, where the Neogene section
is exceptionally thick (often exceeding 300 m),
lack core samples. Coring operations by the
Florida Geological Survey will focus on this area
in 1993 and 1994.

The combined efforts of paleontologists,
lithostratigraphers, sequence stratigraphers and
others are needed to further the understanding
of the Neogene section in peninsular Florida.
Many of the geologists attending the 3rd Bald
Head Island Conference are currently conduct-
ing research in this area and it is hoped that
these efforts will yield significant insight into
this problem.



Department of Earth Sciences, University of North Carolina at Wilmington,
Wilmington, North Carolina 28403


Sequence stratigraphic analysis of marine
sediments on passive continental margins is a
useful tool in unravelling complex temporal and
spatial facies relationships. In areas where
exposures and subsurface control are limited,
and facies changes rapid and repetitive,
mapping of lithostratigraphic units is virtually
impossible. Many mapped units, consequently,
are based on biostratigraphic criteria rather than
lithostratigraphic criteria. As the prime
concerns of stratigraphy are to determine the
succession, age relations, geographic
distribution, and temporal correlation of strata
(Schoch, 1989),chronostratigraphicsubdivision
of the rock record is imperative. The success
of such analyses is most often dependent on
the presence of age-diagnostic fossils.
However, because of provincialism, poor
preservation, or sampling hiatuses, the
widespread occurrence of age-diagnostic fossils
is seldom realized. This results in
biostratigraphic analyses suffering the same
failures as lithostratigraphic analyses.
Sequence stratigraphy, on the other hand,
emphasizes recognition of unconformity-
bounded sedimentary packages (Sloss, 1988).
Although certain aspects of sequence
stratigraphy have come under attack (Miall,
1992), the methodology stresses an integrative
approach of study that attempts to avoid some
of the problems encountered by more conven-
tional stratigraphic analysis.

Although most early "sequence strati-
graphers" relied upon sea level change to
explain genetically related sequences (see series
of papers in Payton, 1977), some workers
(e.g., Pitman, 1978) recognized that sea level
change alone was unacceptable, and that all
influences on sedimentation must be assessed.
Subsequently, sequences were interpreted as
forming in response to the interaction between
rates of eustasy, subsidence, and sediment
supply (Van Wagoner et al., 1988).

Sequence stratigraphic analysis has not
proved to be the panacea for all problems in
stratigraphy as it is difficult to apply in many
geologic settings, for example on active
converging margins. We also find that the
methodology is difficult to apply on a shallow
platform where similar depositional processes,
sediment types, fossil assemblages, and
environmental settings recur through time.
Compounding these problems is the recognition
that in any geologic setting, depositional
sequence development and preservation are
biased because of spatial variations in
accommodation (Jervey, 1988). For example,
along basin margins or on shallow platforms
where accommodation is less than that
basinward, relative sea level fall enhances
erosional processes and provides the overriding
control for sequence and systems tract pre-
servation. Basinward, where accommodation is
greater than that on the basin margin, relative
sea level fall has less effect on sequence and
system tract preservation because the
overriding control is a result of depositional

Recognition of individual systems tracts is
dependent on the location of the study area
within the basin of deposition (i.e., updip
versus down-dip) as well as the type and
spatial distribution of the data base.
Depositional sequences near the shelf break
tend to be preserved in their entirety, whereas
certain systems tracts and surfaces are absent
toward the basin margin and on shallow
platforms (Figures 1A, 1B). We find that the
record of depositional sequences in the Coastal
Plain is most often a record of basin margin or
platform deposits, and preserved sequences are
incomplete and, thus, often difficult to
distinguish. Conversely, unconformities
bounding depositional sequences are often best
developed and most easily recognized in these





M-- - - - - -- C ondensed






Figure 1A and 1B. Type 1 and type 2 sequences illustrating differences in coastal onlap signatures on
basin margins. SMF refers to the surface of maximum flooding.

basin margin or platform deposits, but the
resulting brevity of the rock record complicates
sequence identification and correlation. Figures
1A and 1B illustrate sediment packages repre-
senting depositional sequences near basin
margins or on platforms. These sequences
tend to lack well-defined condensed sections
and lowstand deposits developed above Type 1
unconformities, or shelf margin deposits above
Type 2 unconformities. However, as regional
differences in sedimentation rates and accom-
modation also play a role in the development
and preservation of systems tracts, the dis-
tribution patterns shown in Figures 1A and 1B
are only models. Our experience in the south-
eastern Atlantic Coastal Plain (Zullo and Harris,
1987; Harris et al., 1993) has shown that on
basin margins most depositional sequences are
incomplete and often are represented by thin
transgressive deposits separated by a marine
hiatus (surface of maximum flooding) from
thicker overlying highstand deposits. In these
cases the transgressive surface (first flooding
surface) is collapsed on the underlying uncon-
formity. We have also observed that in many
updip areas highstand deposits unconformably
overlie high-stand deposits of a previous
sequence. In these cases the first flooding
surface and the surface of maximum flooding

are collapsed on the lower bounding

Our goals in southern Florida are to
develop a sequence stratigraphic model for
Neogene and lower Pleistocene sediments
based on biostratigraphic and sedimentological
analysis. Through this analysis we hope to
correlate the resulting model to classic Neogene
and lower Pleistocene sections of the middle
Atlantic Coastal Plain and to the Global Coastal
Onlap Cycles proposed by Haq et al. (1987).
Initially, our work involved study of Pliocene
and lower Pleistocene marine deposits at
surface localities in southwestern Florida (Figure
2). This initial surface work resulted in our
(Zullo and Harris, 1992) proposal of a sequence
stratigraphic model consisting of three upper
Pliocene sequences (Figure 3). The oldest
sequence was assigned to the TB3.6 Cycle and
encompassed the lower Tamiami Formation and
the overlying lower Pinecrest beds. The lower
Tamiami Formation, including beds 10 and 11
of Petuch (1982) and the Murdock Station
Member of Hunter (1968) were interpreted to
represent deposits of the transgressive systems
tract, and the lower Pinecrest beds the
highstand systems tract. The next sequence
was assigned to the TB3.7 Cycle and included


Figure 2. Locations of pits and cores that have been examined: Surface locations 1/Leisey Shell Pit,
Hillsborough County, 2/APAC Pit, Sarasota County, 3/Quality Aggregates Pits, Sarasota County, 4/E
& E Pit, Sarasota County, 5/Rice Road Pit, De Soto County, 6/Schwabach Pit, Charlotte County,
7/Handy Phil Pit, Charlotte County, 8/Lomax-King Pit, Charlotte County, 9/Burnt Store Road Pit,
Charlotte County, 10/Harper Brothers Pit, Lee County, 11/Leheigh Acres Pit, Lee County: Cores -
1/Fudpucker #1 Core, Osceola County, 2/Ms. Caucus Core, Brevard County, 3/Phred #1 Core, Indian
River County, 4/Hogan #1 Core, De Soto County, 5/Quality Aggregates #3 Core, Sarasota County,
6/Babcock Deep Core, Charlotte County.





upper PINECREST beds
STB3.7 -------

lower PINECREST beds
S\ TB3.6 N19/20 -------
=6 lower TAMIAMI FM.


Figure 3. Proposed sequence stratigraphy of the marine Pliocene and lower Pleistocene units of
southern Florida; modified from Zullo and Harris (1992).

the upper Pinecrest beds, which were assigned
to the highstand systems tract. The last
Pliocene depositional sequence recognized was
the Caloosahatchee Formation which was
assigned to the TB3.8 Cycle. Figure 3, which
is modified from Zullo and Harris (1992)
illustrates the proposed sequence stratigraphic
model for these units.

This preliminary model was principally
developed from study of the Quality Aggregates
and APAC pits in Sarasota County and of
several smaller pits in Lee and Charlotte
Counties (Figure 2). Subsequently, we
expanded our investigation to other surface
localities and into the subsurface through
examination of five continuous cores (Figure 2).
Through this expansion we have been able to
recognize and map the upper Pliocene
sequences modeled on the surface; however,
we have found it difficult to apply the concepts
of sequence stratigraphic analysis to the
Miocene and early Pliocene parts of the section.


This paper discusses the problems that we
have encountered in application of sequence

stratigraphic concepts to Neogene and lower
Pleistocene sediments in southern Florida.
Problems that we have encountered are not
limited to Florida geology, and are typical of
other geologic settings worldwide. They are
organized for discussion as follows:

1) scalar distinction of stratal units
(sequences, parasequence sets, and
2) systems tracts identification and
3) separation oferosional unconformities from
non-depositional condensed sections;
4) local mapping (e.g. sequence or parase-
quence scale correlation); and
5) correlation to Global Coastal Onlap Cycles.

Distinction of Stratal Units

The stratal building blocks of sequences
are parasequence sets and parasequences (Van
Wagoner et al., 1990). The principle
differences between these three stratal units
are thickness, lateral extent, and range of time
of formation (Figure 4). Sequence has the
greatest thickness, lateral extent, and
represents the greatest period of time,


parasequence set less, and parasequence even
less. In addition, Van Wagoner et al. (1990)
illustrated that only sequences can be identified
paleontologically, because biostratigraphic
resolution has a resolving power limited to
sequence scale (106-10s years). In basin
margin and shallow platform depositional
settings we have found that biostratigraphic
analysis is generally unable to resolve the
different types of stratal units. In addition,
thickness, lateral extent, and lithology cannot
be used as criteria in distinguishing between
stratal units. Based on study of Neogene and
lower Pleistocene age sediments, we are only
able to make consistent chronostratigraphic
correlations using sequence concepts when
age-diagnostic fossils are present. Note that
we categorize depositional sequences as
chronostratigraphic units (Zullo and Harris,

1987) rather than lithostratigraphic units as
was done by Haq et al. (1988). Cycles serve
as the geochronologic units represented by the
chronostratigraphic referent. Preliminary results
of our sequence stratigraphic work on the
marine Pliocene and lower Pleistocene of
southern Florida were published earlier (Zullo
and Harris, 1992).

Identification of Systems Tracts

Systems tracts consist of a linkage of
contemporaneous depositional systems (Brown
and Fisher, 1977) that are defined by their
position within the sequence and by the
stacking patterns of parasequence sets and
parasequences (Van Wagoner et al., 1990).
Table 1 illustrates the distribution of systems
tracts within idealized type 1 and type 2




(Sq. Miles)

a s a4

1000 100 10 10 00 10100 10 10 10 1

Sequence Unconfannmable

Para -
sequence Surfaces

Para Marine-flooding
sequence surfaces

Figure 4. Distinction of sequence, parasequence set, and parasequence on the basis of boundaries,
thickness, extent, and length of time of formation (modified from Van Wagoner et al., 1990).





Highstand (Late)
Highstand (Early) Highstand (Late)
SYSTEMS Highstand (Late) Transgressive (Distal) Lowstand Wedge
TRACT Transgressive Shelf Margin Deposits or Lowstand Fan
Lowstand Wedge and
Lowstand Fan

INTRASEQUENCE Surface of Maximum Surface of Maximum Surface of Maximum
SURFACE Flooding (?) Flooding Flooding

Table 1. Spatial distribution of systems tracts and intrasequence surfaces in depositional sequences.
Note that under Shelf Margin, shelf margin deposits are restricted to type 2 sequences.

sequences deposited in a basin with a shelf
break. The variations in spatial distributions of
the tracts, e.g. lowstand in the basin and
highstand and transgressive above the shelf
break, are readily apparent. Separation and
distinction of systems tracts are generally
straightforward when the first flooding surface
and the maximum flooding surfaces) asso-
ciated with the condensed section are present.
This situation is seldom realized, particularly on
basin margins and platforms where only abbre-
viated sequences are preserved. Van Wagoner
et al. (1990, p. 39) emphasized the importance
of the marine-flooding surface when they
indicated that "often, the correlative surfaces in
the coastal plain or on the shelf can be
identified only by correlating updip or downdip
from a marine flooding surface." In southern
Florida transgressive surfaces in all Neogene
and lower Pleistocene depositional sequences
are collapsed on the underlying sequence
boundary. Therefore, the surface of maximum
flooding associated with the condensed section
is the only surface that provides distinction
between transgressive and highstand systems
tracts. Parasequence boundaries are defined by
marine flooding surfaces (Van Wagoner et al.,
1990) that sharply separate shallower water
rocks below from deeper water rocks above.
Vertically within parasequences, sediments may

coarsen or fine, bed sets may thicken or thin,
and sand/mud ratios may increase or decrease.
As a result, descriptive sedimentologic criteria
that allow distinction of transgressive from
highstand systems tracts at the parasequence
scale are elusive. In the case of shallow
platforms, the distinction at any one time
between shallower below and deeper above is
beyond resolution, and probably exceeds the
vertical change in water depth caused by
relative sea level rise and fall. When
parasequence sets are preserved, prograda-
tional, retrogradational, and aggradational
stacking patterns of parasequences can be
found in either transgressive or highstand
systems tracts. Therefore, by themselves,
parasequence sets are not definitive in
separating and identifying systems tracts. Our
observation in southern Florida is that parase-
quence sets generally have no unique sedimen-
tological characteristics that distinguish
transgressive from highstand systems tracts.

Unconformities vs. Condensed Sections

The spatial and temporal magnitude of un-
conformity and maximum flooding surface
development on basin margins and platforms is
controlled by base level which is a direct
function of relative sea level. On shallow


platforms such as the one that existed during
the Neogene and lower Pleistocene of southern
Florida, unconformities developed during minor
relative sea level fall (several meters maximum),
and maximum flooding surfaces developed
during minor relative sea level rise (also several
meters maximum). These changes are not
manifested at sequence boundaries or in
condensed sections by the classic charac-
teristics discussed by Loutit et al. (1988),
Posamentier and Vail (1988), and Van Wagoner
et al. (1990). In Neogene and lower
Pleistocene sediments of southern Florida
unconformities are generally characterized by
very minor grain size changes of siliciclastic
components, thin supratidal sediments, a few

land vertebrate and freshwater invertebrate
remains, and poorly developed duricrusts. Any
of these characteristics can easily be confused
with changes other than eustacy within the
process regime, including sediment supply,
source, or quantity. When age-diagnostic
fossils are absent, the lack of distinctive
sedimentologiccharacteristics makes separation
of sequence boundaries from surfaces of
maximum flooding difficult (Figure 5).

Condensed section characteristics include
pelagic to hemipelagic sediments, marine
hiatuses associated with thin continuous zones
of burrowed, slightly lithified sediments,
abundant and diverse planktonic and benthonic





In Literature Florida In Literature Florida

Thin Supratidal
Sediments Biostratigraphic A Few Land
Unconformities Onlap of Overlying Gaps Vertebrates &
Strata Poorly Developed Invertebrates
Duricrusts Sudden Changes
Downward Shift in Paleobathymetry Marsh Plants
in Coastal Onlap Minor Grain Size & Environment Biostratigraphic
Changes Gaps

Pelagic/Hemipelagic Minor Grain Size
Condemned Sediments Changes Diverse Planktonic
sense Marine Hardgrounds Shell Lags & Benthonic Planktonic
Sections Microfossils Microfossils
Secti o Glauconite, Phosphate, Epifauna
Organic Matter

Figure 5. Published sedimentologic and paleontologic characteristics of unconformities (sequence
boundaries) and condensed sections versus characteristics observed from study of Neogene and lower
Pleistocene sediments in southern Florida. Characteristics that are indicated as being in the literature
are from Loutit et al. (1988), Posamentier and Vail (1988), and Van Wagoner et al. (1990).


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microfossils, glauconite, phosphate, siderite,
organic matter, and bentonites (Loutit et al.,
1988). In our experience, these indicators are
frequently absent in the Neogene and lower
Pleistocene sediments that we have studied. In
southern Florida the surface of maximum
flooding represents a very slight water depth
increase as indicated by fossil type and
preservation, and is often accompanied by only
a slight decrease in the size of siliciclastic or
allochemical (phosphate) sediment. Occa-
sionally, the surface of maximum flooding is
marked by a lag of reworked or blackened fossil
shells. Commonly, the underlying transgressive
systems tract is discontinuous and has a
scoured or channelled upper surface. In rare
cases the surface of maximum flooding is
characterized by an epifauna or thin clay beds.
Marine hard-grounds and in most cases
characteristic condensed section sediments
within most sequences are absent and make it
difficult to distinguish condensed sections from
sequence boundaries.

Local Correlation

The lack of distinctive lithologic, sedi-
mentologic, or paleontologic criteria coupled
with limited control, makes it difficult to
correlate depositional sequences or parase-
quences. Although sequences or parase-
quences are generally thin to discontinuous,
supersequences contain distinctive sedimen-
tological patterns that allow gross subdivision
and correlation. For example, in our preliminary
analysis of Miocene age sediments in cores
from the east and west coasts of southern
Florida, supersequences could be correlated
(Figure 6).

Correlation to Global Coastal Onlap Cycles

As indicated by Haq et al. (1988), an
iterative process that reconciles biostra-
tigraphic, magnetostratigraphic, and radiometric
data leads to an integrated magnetobiochron-
stratigraphic framework that is combined with
sequence stratigraphic data from reference
sections to produce sea level (geochronologic
unit) charts. However, the utility of this
process is dependent upon the availability,
quantity and quality of the data. Without high
quality data, sequences cannot be correlated to
global cycles of coastal onlap. In southern

Florida, the available biostratigraphic,
magnetostratigraphic, Sr-isotopic (Jones,
1990), and radiometric data are limited for
much of the Neogene and lower Pleistocene.


Sequence stratigraphic analysis has proven
to be a powerful tool in assessing the geology
of marine sediments on passive continental
margins. Although we proposed a model for
the marine Pliocene based on study of surface
sections (Zullo and Harris, 1992), application
of the concepts to early Neogene sediments in
the subsurface of southern Florida has proved
difficult. Principal problems encountered
include distinction of stratal units, identification
of systems tracts, separation of sequence
boundaries from surfaces of maximum flooding,
and local, regional, and global correlation.
These problems, which are a result of the
recurrence through time of depositional
processes, sediment types, fossil assemblages,
and environmental settings, as well as
diagenetic alteration, are inherent to shallow
platforms. A cross-section from the east coast
to the west coast of Florida (Figure 6) illustrates
some of these problems in the Hawthorn


"The best stratigraphic correlations are
those that have a high degree of reproducibility
within increasing narrower temporal limits...";
therefore, " is important to identify and
employ multiple stratigraphic criteria con-
currently to maximize precision" (Haq et al.,
1988, p. 71). The problems that we have
experienced in application of sequence
stratigraphic concepts to the shallow platform
Neogene and lower Pleistocene sediments of
southern Florida, can only be resolved through
a multidisciplinary approach similar to that
employed by Jones (1990) and Jones et al.
(1991). Under the umbrella of sequence strati-
graphy, integration of invertebrate and
vertebrate biochronology, Sr-isotopic
chronostratigraphy, and magnetostratigraphy,
with sedimentology and seismic stratigraphy
affords the best opportunity of developing an
internally and externally consistent stratigraphic
framework. This is the same approach that has
been used in industry for the past 10 years.


Although the coastal onlap chart has received
criticism as an independent standard of
geologic time (Miall, 1992), an integrative
approach to study of sedimentary successions
on passive margins provides the best oppor-
tunity for unraveling complex stratigraphic
relations. Sequence stratigraphy stresses this
integrative approach.


We are grateful to the University of North
Carolina at Wilmington and the UNCW Center
for Marine Science Research for their generous
funding of this work. In addition, we thank
Thomas Scott and Roger Portell for their
support of our study of Florida Neogene and
Pleistocene stratigraphy, and their enlightening
discussions of Florida geology. Warren Allmon
and Thomas Missimer are also thanked for their
assistance in the field and their discussions of
problems in Florida stratigraphy. UNCW Center
for Marine Science Research Contribution
Number 089.


Brown, L. F., and Fisher, W. L., 1977, Seismic-
stratigraphic interpretation of depositional
systems: Examples from Brazil rift and
pull-apart basins; in Payton, C. E., ed.,
Seismic stratigraphy applications to
hydrocarbon exploration: American
Association of Petroleum Geologists
Memoir 26, p. 213-248.

Haq, B. U., Hardenbol, J., and Vail, P. R.,
1987, Chronology of fluctuating sea levels
since the Triassic: Science, v. 235, p.

Hardenbol, J., and Vail, P. P.,
1988, Mesozoic and Cenozoic chronstrati-
graphy and cycles of sea level change; in
Wilgus, C. K. et al., eds., Sea level
changes: An integrated approach:
Society of Economic Paleontologists and
Mineralogists, Special Publication 42, p.

Harris, W. B., Zullo, V. A., and Laws, R. A.,
1993, Coastal onlap stratigraphy of the
onshore Paleogene, southeastern Atlantic
Coastal Plain, U.S.A.; in Posamentier et
al., eds., Sequence stratigraphy and facies
associations: International Association of
Sedimentologists, Special Publication 18,
p. 537-561.

Hunter, M. E., 1968, Molluscan guide fossils in
late Miocene sediments of southern
Florida: Transactions, Gulf Coast
Association of Geological Societies, v. 18,
p. 439-450.

Jervey, M. T., 1988, Quantitative geological
modeling of siliciclastic rock sequences
and their seismic expression; in Wilgus, C.
K. et al., eds., Sea level changes: An
integrated approach: Society of Economic
Paleontologists and Mineralogists, Special
Publication 42, p. 47-70.

Jones, D. S., 1990, Geochemistry of the
Florida Plio-Pleistocene: An integrated
stratigraphic approach; in Allmon, W. and
Scott, T., eds., Plio-Pleistocene
stratigraphy and paleontology of south
Florida: Southeastern Geological Society,
Annual 1990 Field Excursion, p. 107-120.

MacFadden, B. J., Webb, S. D.,
Mueller, P. A., Hodell, D. A., and Cronin,
T. M., 1991, Integrated geochronology of
a classic Pliocene fossil site in Florida:
Linking marine and terrestrial bio-
chronologies: Journal of Geology, v. 99,
p. 637-648.

Loutit, T. S., Hardenbol, J., Vail, P. R., and
Baum, G. R., 1988, Condensed sections:
The key to age dating and correlation of
continental margin sequences; in Wilgus,
C. K. et al., eds., Sea-level changes: An
integrated approach: Society of Economic
Paleontologists and Mineralogists, Special
Publication 42, p. 183-213.

Miall, A. D., 1992, Exxon global cycle chart: an
event for every occasion?: Geology, v.
20, p. 787-790.


Payton, C. E., ed., 1977, Seismic stratigraphy -
Applications to hydrocarbon exploration:
American Association of Petroleum
Geologists Memoir 26, 516 p.

Petuch, E. J., 1982, Notes on the molluscan
paleontology of the Pinecrest beds at
Sarasota, Florida with the description of
Pyruella, a stratigraphically important new
genus (Gastropoda: Melongenidae):
Proceedings of the Academy of Natural
Sciences of Philadelphia, v. 134, p. 12-30.

Pitman, III, W. C., 1978, Relationship between
eustacy and stratigraphic sequences on
passive margins: Geological Society of
America Bulletin, v. 89, p. 1389-1403.

Posamentier, H. W., and Vail, P. R., 1988,
Eustatic controls on plastic deposition II -
sequence and systems tracts models; in
Wilgus, C. K. et al., eds., Sea-level
changes: An integrated approach:
Society of Economic Paleontologists and
Mineralogists, Special Publication 42, p.

Schoch, R. M., 1989, Stratigraphy, principles
and methods: New York, Van Nostrand
Reinhold, 375 p.

Sloss, L. L., 1988, Forty years of sequence
stratigraphy: Geological Society of
America Bulletin, v. 100, p. 1661-1665.

Van Wagoner, J. C., Posamentier, H. W.,
Mitchum, R. M., Vail, P. R., Sarg, J. F.,
Loutit, T. S., and Hardenbol, J., 1988, An
overview of the fundamentals of sequence
stratigraphy and key definition; in Wilgus,
C. K. et al., ed,, Sea-level changes: An
integrated approach: Society of Economic
Paleontologists and Mineralogists, Special
Publication 42, p. 39-45.

Mitchum, R. M., Campion,
K. M., and Rahmanian, V. D., 1990,
Siliciclastic sequence stratigraphy in well
logs, cores, and outcrops: Concepts for
high-resolution correlation of time and
faces: American Association of Petroleum
Geologists, Methods in Exploration Series,
No. 7, 55 p.

Zullo, V. A., and Harris, W. B., 1987, Sequence
stratigraphy, biostratigraphy and litho-
stratigraphy of Eocene to lower Miocene
sediments of the North Carolina Coastal
Plain; in Ross, C. A., and Haman, D., eds.,
Timing and depositional history of eustatic
sequences: Constraints on seismic stra-
tigraphy: Cushman Foundation for
Foraminiferal Research, Special Publication
24, p. 197-214.

and Harris, W. B., 1992,
Sequence stratigraphy of the marine
Pliocene and lower Pleistocene deposits in
southwestern Florida: Preliminary
assessment; in Scott, T. M., and Allmon,
W. D., eds., The Plio-Pleistocene
stratigraphy and paleontology of southern
Florida: Florida Geological Survey Special
Publication 36, p. 27-40.




'Florida Museum of Natural History and 2Department of Geology, University of Florida,
Gainesville, FL 32611


Florida boasts a rich Neogene stratigraphic
record which has attracted the attention of
geologists and paleontologists since the middle
of the last century. Despite this long history of
investigation, correlation of these deposits is
often difficult because of poor and sporadic
exposures combined with a lack of age-
diagnostic index taxa (particularly planktic
micro- and nannofossils) in predominantly
shallow-water paleoenvironments. We believe
that strontium (Sr) isotope stratigraphy
represents a unique tool for correlating Florida's
shallow-marine units with similar deposits of
the Atlantic and Gulf Coastal Plains as well as
to deep-sea reference sections and the
Geomagnetic Polarity Timescale. Sr isotope
stratigraphy is one of the few techniques that
offers promise of worldwide correlation because
the Sr isotopic composition of seawater is
constant at any point in time due to rapid ocean
mixing. As a result, it is independent of ocean
basin, latitude, or water depth, an attribute
particularly relevant for correlating and dating
the shallow-water sequences of Florida.

Within the last decade, 87Sr/86Sr chrono-
stratigraphy has emerged as an important
geochronologic technique in sedimentary
systems. Investigations of well dated marine
carbonates throughout the Phanerozoic have
demonstrated significant and regular variations
in the 87Sr/86Sr ratio of seawater throughout
geologic time (Burke et a., 1982; Veizer,
1989). During intervals characterized by rapid
Sr isotopic change with respect to time, the
"Sr/86Sr ratio allows rather precise relative and
absolute age determination of unaltered marine
carbonates and phosphates. Fortunately for
geologists interested in Florida, the Sr isotopic
ratio of seawater increased (often rapidly)
through much of the Cenozoic (Elderfield,
1986; Hess et a., 1986). In fact, the best
temporal resolution is offered in the Early

Miocene, between about 23 and 16 Ma, when
the Sr seawater curve is steepest. Refinements
to the global seawater Sr isotope curve for
segments of the Paleogene and the Neogene
(Miller et a., 1988, 1991; Hess et a., 1989;
Capo and DePaolo, 1990; Hodell et al, 1991;
Oslick eta., 1992) indicate that high-resolution
chronostratigraphy should be possible for strata
deposited from the latest Eocene through the
Middle Miocene (as well as from the Late
Pliocene through the Pleistocene). In this
investigation we apply Sr isotope geo-
chronologic techniques to selected strata from
the Oligocene and Miocene of Florida to help
resolve chronostratigraphic uncertainties and
provide a better temporal framework for future
stratigraphic and paleontologic work.

Several recent studies in Florida have
successfully incorporated Sr isotopic analyses
to help unravel age relationships in Pliocene and
Pleistocene (Webb et a., 1989; Jones et a.,
1991) as well as Miocene sediments (Bryant et
aL, 1992; Compton et a., 1993). These
investigations, along with others from the
Atlantic Coastal Plain Province (Denison et a.,
1993; Sugarman etal., 1993), demonstrate the
clear potential for 8Sr/86Sr isotopic analyses to
provide independent age information for
shallow-marine strata. In this study we extend
these techniques to Oligocene and Miocene
units in Florida whose chronostrat-igraphic
position or age assignments have often proven
controversial. We are especially interested in
resolving the age relations of fossiliferous
marine units which contain the remains of ter-
restrial vertebrates so that marine-nonmarine
correlations within the Florida Neogene may be


Twenty-four samples of well preserved
biogenic carbonates, in all cases the skeletal
remains of marine invertebrates, were selected


from the stratigraphic collection at the Florida
Museum of Natural History (FLMNH), University
of Florida (UF), Gainesville, FL. The samples
came from a suite of 10 stratigraphic intervals
at 12 localities within the Oligocene and
Miocene of Florida (Table 1 and Figure 1). All
were molluscan shells except for irregular
echinoids (Rhyncholampas gouldii) and sea star
ossicles (Goniodiscaster sp.) from the
Suwannee Limestone. The Shoal River and
Chipola specimens were composed of aragonite
while all of the remaining specimens were
calcitic. Only specimens with detailed
stratigraphic provenance data were used. All of
the fossils were collected by Muriel Hunter,
Joseph Banks, or Florida Geological Survey or
FLMNH staff and some represent sites which
are no longer accessible.

Each specimen was examined microsco-
pically for evidence of alteration or recrystal-
lization. In addition, X-ray diffraction and
analysis of Sr/Ca ratios by atomic absorption
spectrophotometry were performed on
specimens to assess potential diagenetic effects
which were found to be minimal (Stanley,
1992). All samples were analyzed for
strontium isotopic composition (7Sr/86Sr) in the
Department of Geology at UF using standard
techniques of dissolution, centrifugation,
evaporation, cation exchange chemistry, and
mass spectrometry (Hodell et a., 1991). A
total of 29 separate analyses were made on the
24 samples with five duplicate analyses
performed on separate aliquots of material from
a single specimen in order to estimate
reproducibility (Table 1). In all cases but one,
reproducibility on separate aliquots from the
same sample was 11 X 10-6 or less. 7Sr/e6Sr
ratios were normalized to 86Sr/8Sr = 0.1194.
The NBS standard SrCO3 (SRM-987) was
measured at 0.710244 during the course of this
study with a long-term analytical precision (2s)
of 15 X 10'8. The ratios reported in Table 1
are corrected to SRM-987 = 0.710235 so that
they may be directly correlated to the Sr-
seawater curves of Hodell et a. (1991).

Measured Sr-isotope ratios (or mean values
in the case of duplicated samples) were con-
verted to age estimates using the regression
equations of Miller et a. (1988, 1991), Hess et
al. (1989), Hodell etaL. (1991), and/or Oslick et
al. (1992) for the appropriate interval of time

(Table 1). Discrepancies between age
estimates are generally minimal, except for the
late Middle Miocene where the Hodell et al.
(1991) curve departs from those of Oslick etal.
(1992) and Miller et a. (1991), and the late
Early Miocene where the Hess et a. (1989)
curve diverges from the previous three.
Detailed discussions of errors associated with
Sr ages can be found in Hodell et a. (1991)
and Miller et a. (1991). For the time interval
considered here, errors about single sample Sr
age estimates typically fall into the range of
0.5 to 1.0 m. y. at the 95% level of


Age Estimates

The results of the Sr isotopic analyses are
contained in Table 1. Values for 7Sr/86Sr range
from 0.70785 (Early Oligocene) to 0.70886
(late Middle Miocene). The oldest samples are
from the Suwannee Limestone and when age
estimates calculated from the appropriate
regression equations are averaged together,
they yield a mean age of 34.8 Ma (Early
Oligocene). Samples from the Marianna
Limestone produce a slightly younger Early
Oligocene age of 33.4 Ma. The next youngest
unit, the Tampa Member of the Arcadia
Formation, yielded a Late Oligocene age of 25.4

Nearly identical, latest Oligocene ages
(near the Oligocene/Miocene boundary), were
calculated for samples from the Penney Farms
Formation in Marion County (24.6 Ma) as well
as the Parachucla Formation at White Springs in
Hamilton County (24.4 Ma). Strata along the
upper Suwannee River at the latter site have
been correlated with the Porters Landing
Member of the Parachucla Formation described
from exposures on the Savannah River in
Effingham County, Georgia (T. M. Scott,
personal communication, cited in Huddlestun,
1988, p. 47). However, one sample from the
type locality of the Porters Landing Member in
Georgia yielded a substantially younger age,
20.2 Ma.

An Early Miocene mean age of 19.6 Ma
was calculated for a suite of six samples
collected from the lowermost beds of the


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1 Shell Bluff (along Shoal River)
2 Tenmile Creek (at Bailey's Ferry) S so--
3 Sopchoppy (along Sopchoppy Ck.,
2 miles N of town) LAKE
4 Taff Pit (3 miles S of Crawfordville) \C ( 1
5 White Springs (near SR 136 bridge LEE -ENDY
over Suwannee River)
6 Porters Landing (Savannah River,
Effingham County, Georgia) C
7 Martin-Anthony (road cut near
US 441 and Martin-Anthony Rd.) -
8 Tampa (pit N of Rte. 60 at 78th St.) O
9 Marianna (road cut along US 90)
10 Cabbage Grove (pit in Cabbage Grove
east of Aucilla River)
11 Live Oak (quarry north of Live Oak
along US 129, S of 1-10)
12 Terramar (limerock pit about 6 miles
NW of Socrum) o

Figure 1. Location map for Sr isotopic samples described in Table 1.


Torreya Formation (Pododesmus Zone) at the
Taff Pit in Wakulla County. One sample from
the younger, Sopchoppy Limestone Member of
the Torreya Formation gave an age of 17.4 Ma.
For two specimens from the Chipola Formation
exposed along Tenmile Creek, a mean age of
18.7 Ma (Early Miocene) was calculated from
the age estimates Miocene) was calculated
from the age estimates derived from the
equations in Hodell et al. (1991), Oslick et a.
(1992), and Miller et al. (1991). The slightly
young age estimates calculated from the Hess
et a. (1989) equation were not included in this
average. Similarly, ages calculated from the
Hodell et al. (1991) curve were not incor-
porated into the average age estimate of the
Shoal River Formation samples which was 12.4
Ma (Middle Miocene).


Chronostratigraphic Implications

With a few interesting exceptions, the Sr
isotopic data basically confirm age and strati-
graphic correlations for Florida Oligocene and
Miocene strata based upon biostratigraphic and
lithologic criteria. These correlations and the
refinements offered by 87Sr/86Sr geochronology
are discussed in this section, from youngest to

The Shoal River Formation of the Florida
Panhandle contains a rich record of molluscan
fossils, portions of which have been described
throughout this century (e.g., Gardner, 1926-
1950). Yet, its precise age assignment has
often been debated. Based upon the molluscs
and its stratigraphic position within the Alum
Bluff Group, the Shoal River Formation is
normally assumed to be of Middle Miocene age
(Vokes, 1989). On his Miocene-Holocene
correlation chart, Huddlestun (1988) indicates
that this unit is of Serravallian age, between
about 15-12 Ma. The mean Sr isotopic age
calculated here, 12.4 Ma, agrees well with the
younger age.

Of all the formations within the Alum Bluff
Group of northwestern Florida, the Chipola
Formation is probably best known because of
its spectacular molluscan fauna which may
contain over 1,000 species (Vokes, 1989).

This fauna has been documented by Gardner
(1926-1950) and more recently by E. and H.
Vokes and others who have noted its
Burdigalian (Early Miocene) age affinities. Once
again, however, the precise age of the Chipola
Formation is unclear. Akers (1972) favored a
correlation with planktonic foraminiferal zone
N7 or possibly N8, but this assessment is
largely based on negative evidence. He/U dates
on Chipola corals averaged 16.1 1.0 Ma
(Bender, 1973).

More recent work, however, indicates a
slightly older age for the Chipola. Bryant et al.
(1992) analyzed four samples from the Chipola
Formation at the familiar Alum Bluff section
which yielded Sr isotopic ages of 18.3-18.9 Ma
(Figure 2). The two Chipola samples analyzed
in this study were recovered from Tenmile
Creek in neighboring Calhoun County. Never-
theless, age estimates for these samples show
considerable overlap with those of Bryant et al.
(1992) and argue strongly for an older (ca. 18-
19 Ma) age assignment.

Bryant et a. (1992) also addressed the
stratigraphic relationship between the Chipola
and the Torreya Formation. Challenging the
traditional view that the Chipola is younger than
the Torreya, and despite the observation that
the Chipola overlies the Torreya in the
subsurface at Alum Bluff (Scott, 1988;
Huddlestun, 1988), the only place where these
units occur together, Bryant et a. (1992)
concluded that there is considerable
chronologic overlap between the lower Torreya
Formation and the upper Chipola Formation.
The Sr isotopic data presented here support this
conclusion (cf., Figures 2 and 3) and provide
additional temporal resolution for the Torreya.

Based on Sr isotopic samples from several
localities as well as other geochronologic
evidence, Bryant et a. (1992) estimated an age
range of ca. 17-15.3 Ma for the Dogtown
Member of the Torreya Formation. One sample
from the Seaboard locality in Tallahassee,
within the Pododesmus Zone and probably near
the base of the Torreya (Hunter and
Huddlestun, 1982), yielded an age of 18.4 Ma.
Bryant et al. (1992) speculated that the lower
boundary of the Torreya had an age of ca. 19
Ma. Ten years earlier Hunter and Huddlestun






_________________________....._ - ...... .t







- 0

18.3 18.9 Ma


CH1, CH2 1
18.4-18.9 Ma

Figure 2. Sr isotopic ages for the Chipola Formation based on samples from Alum Bluff (left) and
Tenmile Creek (right). Lithostratigraphic section at Alum Bluff from Bryant et al (1992) showing
sample horizon and age range of four Sr isotopic samples (C1-4). Shell samples (CH1, CH2) tor 1:nis
study came from Tenmile Creek, located approximately 25 km to the northwest in Calhoun County, and
show remarkable age consistency.


Geochronology of the Torreya Formation

Bryant et al. (1992)

m1 5.3 Ma



17 Ma

18.4 Ma

?19 Ma

This study

17.4 Ma

Six Sr
19.6 Ma

Figure 3. Geochronology of the Torreya Formation based on Sr isotopic analyses from this study
(shown on the right) and a variety of methods (including Sr isotopes) used by Bryant et al. (1992)
shown on the left. SB stands for Seaboard Coast Line railroad yard site in Tallahassee. Vertical arrows
associated with this and the Sopchoppy sample indicate uncertainty in stratigraphic position.
Relationship between molluscan biozones (Chlamys nematopleura Local Assemblage Zone, Carolia
floridana Local Range Zone, Pododesmus scopelus Assemblage Zone) and lithostratigraphic units
modified from Hunter and Huddlestun (1982) and Bryant et al. (1992).


(1982) had proposed 19-20.5 Ma. These pre-
dictions are supported here by six samples from
the lowest beds of the Torreya Formation at the
Taff Pit which gave a mean Sr isotopic age of
19.6 Ma. Additionally, one sample from the
Sopchoppy Limestone Member (Carolia Zone)
yielded a somewhat younger age, 17.4 Ma
(Figure 3).

Along the upper reaches of the Suwannee
River in the vicinity of White Springs, strata of
the Hawthorn Group overlie the Oligocene
Suwannee Limestone. These basal Hawthorn
beds represent the initial Tertiary influx of
siliciclastic sediments onto the Florida Platform
which had been a predominantly carbonate
environment since the Mesozoic. The basal
Hawthorn unit in the White Springs area has
been identified as the Porters Landing Member
of the Parachucla Formation (Huddlestun,
1988). Exposed more extensively in Georgia,
this represents the only occurrence of the
Parachucla Formation in Florida where its
downdip, lateral equivalent is the Penney Farms
Formation (Scott, 1988, 1989). Morgan (1989)
reports earliest Miocene vertebrate fossils from
this site (the White Springs Local Fauna) which
belong to the late early or early late Arikareean
North American Land Mammal Age, between
about 25 and 21 Ma. Invertebrate fossils from
the same site were less age diagnostic (Portell,
1989). The age of the Porters Landing Member
in Georgia is considered to be Early Miocene
(Aquitanian, probably upper Zone N4 or lower
N5) based on planktonic foraminifera
(Huddlestun, 1988); no planktonic foraminifera
have been found in the White Springs area.

Sr isotopic analyses of two fossil shells
from Unit 1 at the White Springs locality
(Portell, 1989) gave similar ratios and yielded a
latest Oligocene-earliest Miocene age estimate
of 24.4 Ma. In contrast, the Sr isotopic age
calculated for a specimen from the type locality
at Porters Landing, Effingham County, Georgia
was significantly younger, 20.2 Ma. These
initial results signal the need to re-evaluate the
correlation of the basal Hawthorn sediments
near White Springs with the Porters Landing
Member of the Parachucla Formation.
Huddlestun (1988, p. 47) notes that the Porters
Landing Member is thin near White Springs and
is not recognized elsewhere in the Suwannee
area. Perhaps the unit is diachronous to the

south. Alternatively, the correlation could be
wrong. Clearly more detailed sampling will be
required to resolve this issue.

The Penney Farms Formation, as men-
tioned above, was erected by Scott (1988) to
include Early Miocene (Aquitanian) sediments in
Florida equivalent to the Parachucla Formation
in Georgia (Huddlestun, 1988). However, the
Penney Farms contains few biostratigraphically
useful fossils and generally lacks chronologic
resolution. Except for a few foraminifera from
a core in Nassau County, the only other site
yielding datable fossils is the Martin-Anthony
site in northern Marion County (Scott, 1988).
Here MacFadden (1980) reported an oreodont
jaw of late Arikareean age, just slightly older
than the Martin-Anthony Local Fauna collected
a bit higher in the section. Hunter and
Huddlestun (1982) suggest that this oreodont
dates from 22-21 Ma. Morgan (this volume)
supports this correlation, indicating that the
oreodont is about 2 m.y. younger than the
oreodonts from the White Springs Local Fauna.
Nevertheless, Sr isotopic ratios from shells
collected from sediments ("Unit 9" ?) above the
underlying Eocene Ocala Limestone are identical
to those measured from White Springs,
suggesting a latest Oligocene-earliest Miocene
age of 24.6 Ma. These Sr data strongly
support the temporal correlation of the Penney
Farms Formation in Marion County with the
Parachucla Formation at White Springs.

The age and stratigraphic position of the
Tampa Limestone, now included in the Tampa
Member of the Arcadia Formation (Scott,
1988), have been debated for over a century.
The Tampa Member crops out only around the
Tampa region (it is recognized more extensively
from core material) and fossils from this unit
have caused some authors to place it in the late
Oligocene and others in the Early Miocene.
Both Hunter and Huddlestun (cited in Scott,
1988, p. 72) believe that the Tampa Member
straddles the Oligocene/Miocene boundary and
equates with part of the Parachucla Formation
in Georgia. The Tampa Member is also
correlated with part of the Penney Farms
Formation in northern Florida (Scott, 1988).
Two Sr isotopic samples from shells collected
near the type locality at Sixmile Creek in Tampa
yielded similar isotopic ratios and an age
estimate of 25.4 Ma. This date would seem to


fix the (more restricted) Tampa Limestone
portion of the Tampa Member in the Late
Oligocene. Errors associated with the Sr-
derived ages do not exclude the possibility of
temporal overlap with the Parachucla and
Penney Farms Formations.

In the southeastern U.S. Oligocene strata
(and their associated faunas) are normally sub-
divided into two stages, an older Vicksburgian
Stage and a younger Chickasawhayan Stage.
This subdivision works well in the Gulf Coastal
Plain but correlations break down as one moves
eastward into the purer, shallow-marine
carbonate units of southern Georgia and
Florida. Consequently, the correlation of
Oligocene units within Florida frequently has
proven difficult. For example, the Suwannee
Limestone has often been placed in the
Chickasawhayan Stage, but there is strong
faunal and stratigraphic evidence to suggest
that it is predominantly (if not entirely)
Vicksburgian (Bryan, 1991). In such cases
where shallow-marine units lack age-diagnostic
microfossils and lithologies change from a type
area so that key macroinvertebrate fossils
useful for correlation are excluded, Sr isotope
chronostratigraphy is particularly valuable.

We sampled two well known Oligocene
carbonate units from Florida, the Marianna
Limestone and the Suwannee Limestone. The
Marianna is a fully marine, shelf carbonate unit
interpreted by sequence stratigraphers as a
highstand deposit (Bryan, 1991). It has been
correlated with lower portions of the Suwannee
Limestone (Braunstein et a., 1988; Bryan,
1991). Two molluscan shells from the type
locality in Marianna gave a mean Sr isotopic
age of 33.4 Ma (Vicksburgian, Early Oligocene).
The Suwannee Limestone is interpreted as
having formed in a very shallow, carbonate
platform to backreef setting (Bryan, 1991).
Coral thickets or patch reefs occur at several
localities, including two of the three sites
sampled here. We analyzed four samples (all
echinoderms) from three widely spaced
localities representing most of the geographic
range in Suwannee outcrop distribution (Figure
1). In general the samples all yielded similar
ratios except the Terramar sample which was
more similar to the ratios of the Marianna
samples. The mean Sr isotopic age of 34.8 Ma
for the Suwannee samples is only slightly older

than the age estimate for the Marianna. No
Late Oligocene (Chickasawhayan) samples were
encountered in either unit.

Correlation with Sea-level History

Both the Suwannee Limestone and the
Marianna Limestone seem to correspond to the
sea-level highstand from 35-30 Ma (TA4, cycle
4.4 and possibly 4.5 of Haq et al., 1988). The
major sequence boundary at 30 Ma, corre-
sponding with one of the most rapid and
significant eustatic falls in the Cenozoic,
ushered in a new sedimentary regime for the
Florida Platform. The unconformable contact
between these Oligocene carbonates and the
overlying siliciclastics of the Hawthorn Group
may represent exposure or non-deposition
during the ensuing relative lowstand in sea level
(TB1, 1.1-1.3) between about 30-25 Ma
(Compton et al., 1993). During this interval
and on into the Early Miocene, the Gulf Trough
barrier to the north filled and siliciclastics
flooded across the platform. The geologic
history of these Hawthorn Group sediments is
directly related to fluctuations of global sea
level (Scott, 1988).

The basal units of the Hawthorn Group,
the Parachucla Formation in Georgia, the
Penney Farms Formation in northern Florida,
and the Arcadia Formation in southern Florida,
represent this transition from carbonate to
siliciclastic environment while the Sr-derived
ages calculated here confirm the timing as
latest Oligocene/earliest Miocene (ca. 25-24
Ma). The Late Oligocene Tampa (Limestone)
Member (in the vicinity of Tampa) of the
Arcadia Formation occurs at an elevation not
significantly different than modern sea level and
formed about 25 Ma, probably early in the sea-
level highstand from 25-21 Ma (TB1, 1.4-1.5).
This same interval corresponds to the earliest
episode of phosphogenesis on the south-central
Florida Platform based on Sr ages of phos-
phorites and carbonates from a core penetrating
the Arcadia Formation (Compton et al., 1993).

Upper units of the Hawthorn Group and
units within the Alum Bluff Group in
northwestern Florida accumulated later in the
Miocene. The Torreya and Chipola Formations,
for example, display significant chronologic
overlap and probably were deposited during the


relative sea-level high between the sequence
boundaries at 21 and 15.5 Ma (TB2, 2.1-2.3).
Sr-derived ages from the Middle Miocene Shoal
River Formation indicate that it corresponds
with cycles TB2, 2.5-2.6. This unit is
temporally equivalent to much of the Peace
River Formation (upper Hawthorn Group) which
is considered to range from at least the early
Middle Miocene into the Early Pliocene (Scott,
1988) and where Sr ages from benthic foram-
inifera confirm a span of 11-5 Ma (Compton et
al., 1993).


This preliminary investigation clearly
demonstrates that Sr isotope stratigraphy has
great potential 'for placing Florida Cenozoic
sequences into a firmer temporal framework. In
this study only a few samples were measured
from selected Oligocene and Miocene forma-
tions. There was no attempt to constrain the
ages of formational boundaries. We plan to
continue this work by expanding sample
distributions both within these and other Florida
units, aiming for broader geographic and
stratigraphic coverage, focusing particularly on
the tops and bottoms of formational

More Sr isotopic analyses on samples from
elsewhere in Florida will enhance chronostra-
tigraphic resolution and assist in correlating the
marine sedimentary record with the Geomagne-
tic Polarity Timescale. The improved temporal
framework will allow geologists to address
questions of broader significance. For example,
Sr isotopes have been useful for delineating the
relationship between global eustatic changes,
marine 6"1C excursions, and phosphogenesis on
the Florida Platform (Compton et al., 1993). In
addition, Sr stratigraphy may allow paleon-
tologists to study the influence of global climate
change upon shallow marine organisms, rela-
tionships between Florida faunas and temporal
equivalents elsewhere, patterns of evolution
and extinction, and to correlate biotic and
climatic changes in the sea with those in the
terrestrial realm.


We thank Muriel Hunter and Roger Portell
for help in sample acquisition and Jose Garrido

and Ann Heatherington for assistance with Sr
isotopic analyses. This research was supported
by NSF Grant BSR-9002689 and the Donors of
the Petroleum Research Fund administered by
the American Chemical Society. This paper
represents University of Florida Contribution to
Paleobiology no. 430.


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and Mallinson, D. J., 1993, Origin and age
of phosphorite from the south-central
Florida Platform: Relation of
phosphogenesis to sea-level fluctuations
and 613C excursions: Geochimica et
Cosmochimica Acta, v. 57, p. 131-146.

Denison, R. E., Hetherington, E. A., Bishop, B.
A., Dahl, D. A., and Koepnick, R. B.,
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1988, Mesozoic and Cenozoic chrono-
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eds., Sea-level changes An integrated
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1986, Evolution of the ratio of strontium-
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present: Science, v. 231, p. 979-984.

Stott, L. D., Bender, M. L., Kennett, J.
P., and Schilling, J-G., 1989, The
Oligocene marine microfossil record: Age
assessments using strontium isotopes:
Paleoceanography, v. 4, p. 655-679.

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1991, Variations in the strontium isotopic
composition of seawater during the Neo-
gene: Geology, v. 19, p. 24-27.

Huddlestun, P. F., 1988, A revision of the
lithostratigraphic units of the coastal plain
of Georgia: The Miocene through
Holocene: Georgia Geological Survey
Bulletin 104, 162 p.

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Formation in Florida, in, Scott, T. M., and
Upchurch, S. B., eds., Miocene of the
southeastern United States: Florida
Geological Survey Special Publication 25,
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Jones, D. S., MacFadden, B. J., Webb, S. D.,
Mueller, P. A., Hodell, D. A., and Cronin,
T. M., 1991, Integrated geochronology of
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'Department of Marine Science, University of South Florida, St. Petersburg, FL 33701, and
2Department of Geology, University of Florida, Gainesville, FL 32611

The strontium isotopic ratio ("Sr/86Sr) of
phosphorite and carbonate grains has proved
extremely useful in sorting out the complex
diagenetic and depositional history of the
Hawthorn Group of Florida. The Sr-derived
ages are useful in determining the relation of
phosphogenic episodes and sediment reworking
events on the Florida Platform to fluctuations in
global sea-level and the carbon isotopic
composition of seawater. The Sr-derived ages
are most useful when combined with available
biostratigraphy. Before Sr isotopes can be used
for deriving age dates the elemental and
isotopic composition of the phosphorite must
be determined to evaluate possible alteration.
Our preliminary results indicate that the most
useful Sr ratios are from relatively unaltered
phosphorite, dolomite, and in-situ (or at least
not extensively reworked) biogenic carbonate.
The amount of Sr contributed by other HCI-
soluble minerals should be insignificant because
of the high Sr content of the francolite and of
the predominance of francolite in the samples
analyzed. However, it is important to remove
phosphorite from carbonate samples before Sr
analysis because the Sr content of phosphorite
is an order of magnitude greater than the Sr
content of dolomite and calcite. Benthic
foraminifers appear to be the best in-situ
biogenic carbonate to age date final sediment
deposition. Dolostone beds also provide useful
ages of sediment that has not been significantly
reworked. Mollusk and other shell material and
shark's teeth are generally older and reworked,
and their Sr-derived ages are not particularly
useful. Phosphorite grains of similar type
(mostly dark colored, rounded peloidal grains)
from an individual sample generally give the
same age date within the resolution of the Sr
isotope technique. However, some samples
show a wide range of ages among phosphorite
grains. Samples with a wide range of ages
usually coincide with condensed intervals that

appear to correspond to long-term sea-level
lowstands (Compton et al., 1993).

The Sr isotopic ratio of the phosphorite is
interpreted to represent the Sr isotopic ratio of
seawater at the time of its formation. The Sr
incorporated in francolite is assumed to be in
isotopic equilibrium with the pore water Sr as
documented for modern francolite from the
Peruvian and South African margins (McArthur
et al, 1990). Pore-water Sr is most likely
derived from seawater originally buried with the
sediment and Sr released from dissolution of
aragonitic shell material. The isotopic
composition of Sr from these two sources
should be the same and reflect the seawater Sr
value at the time of deposition. The amount of
older, reworked aragonitic shell material is
assumed to be negligible because aragonite is
highly soluble and unlikely to survive reworking.
The Sr isotopic composition of the pore water
is not expected to change significantly during
early burial diagenesis (McArthur et al., 1990).

The Sr-derived ages of the benthic
foraminifers are interpreted to represent final
sediment deposition because the predominant
foraminifer, Buliminella elegantissima, is
considered in-situ and too fragile to survive
reworking in high-energy environments (V.
Waters, personal communication, 1991).
Recrystallization of the benthic foraminifers is
expected to decrease the Sr content, but may
not necessarily alter the Sr(87/86) ratio. The
assumption that the Sr isotopic composition of
the benthic foraminifers is unaltered is
supported by the good agreement between the
Sr-derived ages of the benthic foraminifers and
independent biostratigraphic ages. The oxygen
isotopic composition of the foraminifers also
indicates minimal alteration.

The Sr(87/86) isotopic ratio of phosphorite,


benthic foraminifers, shell fragments, dolomite,
and shark's teeth in the Miocene Hawthorn
Group from southwest and northeast Florida
ranges from 0.708111 to 0.709005. These Sr
ratios correspond to a range in Sr-derived ages
of Late Oligocene (27-25 Ma) to latest
Miocene/Early Pliocene (5-4 Ma). The age of
these grains was derived from the regression
equations of seawater Sr187/86) presented by
Hodell et al. (1991) and Oslick et a. (1992).
The Sr-derived ages using these two regression
equations are in good agreement for samples
older than 17 Ma. For samples younger than
17 Ma the ages agree within the estimated
error, but ages calculated using the regression
equation of Oslick etal. (1992) are consistently
older than ages calculated using the regression
equation of Hodell etal. (1991). Age resolution
using Sr isotopes is greatest (0.74 m.y.) for
samples that formed between the Late
Oligocene and the end of the Early Miocene (16
Ma) because this is the steepest interval of the
seawater Sr'87/86) curve; the curve is less steep
for the Middle and Late Miocene (Hodell et al.,

The Sr'871861 ratios tend to increase
upsection, as predicted by the seawater Sr(87186)
curves, as shown, for example, in Figure 1 for
samples analyzed from the Babcock Deep core
in southwest Florida. Although the Sr'87/86)
ratios tend to increase upsection, phosphorite
in the Babcock Deep core of the same age can
occur over 30 m thick stratigraphic intervals
and phosphorite from the same depth can differ
in age by as much as 3.6 m.y. The calcareous
benthic foraminifer Buliminella elegantissima is
consistently younger than phosphorite from the
same sample. Calcareous shell fragments tend
to be older than benthic foraminifers but
younger than phosphorite. Dolomite is
approximately the same age as associated
phosphorite. Shark's teeth are approximately
the same age or older than phosphorite from
three samples (Figure 1).

The Sr isotopic composition of the samples
analyzed in this study has probably not altered
since phosphorite formation because the fran-
colite does not appear to have been signifi-
cantly altered despite the physical reworking of
many of the grains. The uniformly high Sr, Na,
Mg, SO4, and CO3 contents of the francolite,
the oxygen isotopic values of the francolite CO3

(-0.2 to -4.2 %o PDB), and the inclusion of
pyrite and organic matter in phosphorite grains
of this study suggest that the francolite has
had minimal chemical alteration. Therefore, the
Sr ratio of the unaltered phosphorite should
reflect the Sr ratio of the pore waters during
early burial diagenesis. Francolite in peloidal
phosphorite from the Babcock Deep core of
southwest Florida is highly substituted with an
average composition of:
(Ca4.61 Nao.22 Mg0.14 Ko.o5 Sro.02) (P04)2.23
(C03)0.62 (SO4)o.12 (F)1.04
The combined carbon and sulfur isotopic
compositions of substituted CO3 and S04 ions
in the francolite indicate that the phosphorite
formed during the early diagenesis of organic-
rich sediment probably within a meter of the
sediment-seawater interface. Carbon isotopic
values of -1.0 to -7.8 %o PDB of the francolite
CO3 indicate a substantial contribution of
carbon from an organic source. The sulfur
isotopic composition of francolite SO4 is
depleted to slightly enriched relative to Miocene
seawater and suggests that phosphogenesis
occurred during early burial diagenesis in
organic-rich sediments above or in the zone of
sulfate reduction.

The consistently younger age of relatively
fragile calcareous benthic foraminifers than
associated hard, tightly-cemented phosphorite
supports textural evidence that much of the
phosphorite is reworked. The age of the host
sediment ranges from Early Miocene to Pliocene
and its depositional history is related to sea-
level fluctuations. The cycle of organic-rich
deposition, phosphorite formation during early
diagenesis, and organic carbon removal and
phosphorite concentration during sediment
reworking was repeated as the shoreline
migrated in response to sea-level fluctuations.
Approximately three-quarters of the total
phosphorite in the Babcock Deep core formed
during or within 2 m.y. before the major Early
to mid-Miocene positive carbon isotopic shift as
recorded at DSDP Site 588 (southwest Pacific)
(Figure 2). These results indicate that reworked
phosphorite deposits may provide a proxy of
organic carbon cycling on continental shelves
that correspond to sea-level fluctuations and to
variations in the marine carbon isotopic record
(Compton et a., 1990).


87Sr/ Sr

0.7080 0.7084 0.7088 0.7092
20 I I I I I I i I I I


ca 60
| -



M 100-
&. ,

0 -



IBabcock Deep Core

+ +


+X -46 M

A A + +

x ++ C+


+ phosphorite

* benthic foraminifers

0 shell fragments
X dolomite
A shark's teeth

TI 1 U H I 1 U I II H' 1 U I 'I I' I

Figure 1. The Sr (87/86) ratios of phosphorite, benthic foraminifers, shell fragments, dolomite, and shark's
teeth vs. depth in the Babcock Deep core.

+ x


0.7090 --

0.7088 -8% I

0- --


0.7082 2%
11% age unknown

00 0.7080- I-
III PERCENT OF TOTAL -- 5 1125 32 6 2


c 13C

-- 81 3C

100 200 300 s13 400
DEPTH (meters below sea floor)
Figure 2. Comparison of the Sr (87/86 ratios of phosphorite from the Babcock Deep core (W-10761) to
the strontium and carbon isotopic compositions of benthic foraminifers from DSDP Site 588 (Lord Howe
Rise, southwest Pacific Ocean) (Kennett, 1986). The numbers in the shaded regions represent the
percent of the phosphorite in the Babcock Deep core that has that range of Sr isotopic values. The
intersection of the range in Sr isotopic values with the Sr isotopic curve of Site 588 is projected onto
the corresponding 613C record to show the correlation of phosphogenesis on the Florida Platform to the
early to mid-Miocene positive 6'3C excursion.



Compton, J. S., Snyder, S. W., and Hodell, D.
A., 1990, Phosphogenesis and weathering
of shelf sediments from the southeastern
United States: Implications for Miocene
613C excursions and global cooling:
Geology, v. 18, p. 1227-1230.

Hodell, D. A., Garrido, J. R.,
and Mallinson, D. J., 1993, Origin and age
of phosphorite from the south-central
Florida platform: Relation of
phosphogenesis to sea-level fluctuations
and '13C excursions: Geochimica et
Cosmochimica Acta v. 57, p. 131-146.

Hodell, D. A., Mueller, P. A., and Garrido, J. R.,
1991, Variations in the strontium isotopic
composition of seawater during the Neo-
gene: Geology, v. 19, p. 24-27.

Kennett, J. P., 1986, Miocene to Early Pliocene
oxygen and carbon isotope stratigraphy in
the southwest Pacific, Deep Sea Drilling
Project Leg 90, in Kennett, J. P., et al.,
eds., Initial Reports of the Deep Sea
Drilling Project 90: Washington, D.C.,
U.S. Government Printing Office, p. 1383-

McArthur, J. M., Sahami, A. R., Thirwall, M.,
Hamilton, P. J., and Osborn, A. O., 1990,
Dating phosphogenesis with strontium
isotopes: Geochimica et Cosmochimica
Acta, v. 54, p. 1343-1351.

Oslick, J. S., Miller, K. G., and Feigenson, M.
D., 1992, Lower to Middle Miocene Sr'87/86I
reference section: Ocean Drilling Program
Hole 747A (abstract): EOS, v. 73
Supplement, p. 171-172.




Rosenstiel School of Marine and Atmospheric Science, University of Miami,
4600 Rickenbacker Causeway, Miami, Florida 33149


It is proposed to include the lower portions
of the Caloosahatchee and Anastasia Forma-
tions, the Tamiami Formation, and the Peace
River Formation of the Hawthorn Group in the
Pliocene of southern Florida. Mapping of
regional disconformities and rock stratigraphic
units has been combined with existing age data
to define the boundaries of the Pliocene. There
are remaining difficulties in the exact location of
the Plio-Pleistocene boundary in the Caloosa-
hatchee Formation and in the definition of the
Anastasia Formation. The exact position of the
Mio-Pliocene boundary may change based on
some new data currently being collected.


Lack of absolute age data has presented a
continuing problem in the correlation and
analysis of the Neogene sediments of southern
Florida. For many years, the ages of named
formations, such as the Caloosahatchee
Formation and the Tamiami Formation, have
been repeatedly redefined in terms of absolute
time. Each new age assigned was based on
molluscan evolution (Dall, 1890-1903; Olsson,
1964; Ketcher, 1992), microfossils (Akers,
1974; Peck et al, 1979a; Klinzing, 1987),
vertebrate fossils (DuBar, 1958) or a more or
less arbitrary selection (Parker et al, 1955).
During the period from about 1955 to the early
1970s, Pliocene-age sediments were unrecog-
nized in southern Florida based on belief that
the Caloosahatchee Formation was Pleistocene
in age (DuBar, 1958, 1962) and the Tamiami
Formation was Late Miocene in age (Parker et
al., 1955). In fact, stratigraphy courses taught
in Florida in the early 1970s commonly
explained the "absence" of Pliocene-age
sediment by deep erosion which occurred
during the glacial stages of the Pleistocene.

Changes in the geologic time scale used to
define the absolute time boundaries between
periods also contributed to the problem. The
most current defined age range for Pliocene
time is 1.64 to 5.2 Ma (Harland et al., 1990).


Based on the stratigraphic work accomp-
lished by many investigators and new age data,
a general model of the Pliocene stratigraphic
units in southern Florida is herein proposed
(Figure 1). There are four named formations
included within Pliocene time in southern
Florida, including the lower parts of the
Caloosahatchee and Anastasia Formations, the
Tamiami Formation, and the Peace River
Formation of the Hawthorn Group. All of the
proposed Pliocene formations are separated
from each other and from younger and older
units by regional unconformities. A summary
of the basis of the age dates is given in Table 1
with correlating locations on Figure 1.

The unconformity defining the base of the
system is well documented in the central part
of the Florida platform (Missimer, 1978;
Missimer and Gardner, 1976; Boggess,
Missimer and O'Donnell, 1982), where it is a
probable exposure surface. This disconformity
tends to become less pronounced from west to
east across the platform passing from exposure
to shallow water to deeper water. Although
there is continuous sedimentation across the
proposed Mio-Pliocene boundary on the eastern
margin of the platform, there is a significant
increase in the plastic component of the
sediment, which is interpreted as shedding of
sediment from the erosion of the underlying
Arcadia Formation and the southward move-
ment of plastic sediment along the platform















@0 QE_)


3.6 -

3.8 -

4.0 -

4.2 -
4.4. -

4.8 -

5.0 -

Figure 1. Proposed Pliocene Stratigraphic Units in Southern Florida. Letters refer to fossil assemblages
in Table 1.


Table 1. Summary of age data for Pliocene formations in Florida

A. Peck, 1976; Peck et al., 1979a; Peck et al., 1979b Tamiami Formation (Cape Coral Clay Member)
(Note: current terminology, Hawthorn Group, Peace River Formation, Cape Coral Clay Member)

Miocene planktonic foraminifera and nannofossils become extinct at the Unit 2 Unit 3 boundary
(base of Cape Coral Clay)

Calcareous nannofossils Beds 1 and
Coccolithus pelagicus
Cyclococcolithus leptoporous
Reticulofenestra pseudoumbilica
Planktonic Foraminifera Beds 1 and
Globigerina bulloides bulloides
Globigerinoides quadrilobatus quadrilobatus
Hastigerina siphonifera siphonifera
Calcareous nannofossils Beds 3-8 Pi



eace River Formation

(assumed to be Miocene)
Diocoaster brouweri
D. berggreni
D. quinqueramus
D. varibilis
Coccolithus pelagicus
Cyclococcolithus leptoporous
Helicopontosphaera kamptneri
Planktonic foraminifera
Globigerina bulloides apertura
G. bulloides bulloides
G. druryi decoraperta
G. nepenthes
Globigerinoides obliquus extremus
G. obliquus obliquus
G. quadrilobatus quadrilobatus
G. ruber
Globorotalia acostaensis humerosa
Hastigerina (H.) siphonifera siphonifera
Sphaeroidinellopsis seminulina seminulina
S. subdehiscens subdehiscens
B. Jones etal., 1991
Fossil land mammals (Blancan assemblage)
from Unit 4 at APAC Pit

Tadarida sp.
Holmesina floridanus*
Dasypus bellus*
Megalonyx leptostomus

Sylvilagus sp.

Geomys cf. G. propinetis
Neochoerus dichroplax*
Sigmodon medius
Trigonictis macrodon

Procyon sp.

Rhyncotherium sp.

Nannippus peninsulatus
Cormohipparion emsliei
Equus (Asinus) advanced sp.
Platygonus bicalcaratus

Mylohyus floridanus

Hemiauchenia blancoensis
Bovinae indet.


Units 10-5 age younger than 3.5 Ma
Puriana mesacostalis 3.0-3.5 Ma
Actinocythereis captionis
Catiuella navis
Puriana convoluta
Puriana floridana
Puriana mesacostalis
Puriana carolineusis
Units 4-2
Acuticythereis n. sp.
Climacoidea (Reticulocytheris) sp.
Climacoidea (Proteoconcha) n. sp.
Strontium isotope ("Sr/86Sr) chronostratigraphy
Unit 1 1.5-2.0 Ma
Units 2-11 2.0-5.0 Ma*
*Flat area of Sr isotope curve
All samples show reversed polarity (probable
C. Bender, 1973
Helium-uranium age dates
Caloosahatchee Formation
Sample No. Location in Section Correcte

21954 SPH
21955 M
21955 CM


co-occurence range
3.0-3.5 Ma

1.8-2.5 Ma est.


d Age


Pinecrest Formation

Sample No.
23463 MN
23463 MT

Corrected Age

D. Akers, 1974
Unit: Tamiami Formation
Pinecrest Member
Planktonic foraminifera
Globigerina bulloides
Globorotalia inflata
Calcareous nannoplankton
Braarudosphaera bigelow Gran and Braarud
Coccolithus doronocoides Black and Barnes
Coccolithus pelagicus Wallich
Cycloccolithina leptopora Murray and Blackman
Cyclotithelia annula Cohen
Gephyrocapsa caribbeanica Boudreaux and Hay
Gephyrocapsa reticulata Nishida
Helicopontosphaera kamptneri Hay
Reticulofenestra pseudoumbilica Gartner
Sphenolithus abies Deflandre


Syracosphaera pulchra Lohmann
Umbilicosphaera mirabilis Lohmann
Concurrence of Gephyrocapsa caribbeannica, Reticulofenstra, pseudoumbilica, and
Sphenolithus abies in Blow (1969) Zone 20 indicates a middle Pliocene age.
E. Klinzing (1987)
Core W-14072
Diatoms, Unit: Hawthorn Group, Peace River Formation, Cape Coral Clay Member
Species Age Range
Actinocyclus ehrenbergii Ralfs (1861) M. Miocene to U. Pliocene
Actinocyclus octonarius Ehrenberg M. Miocene to Recent
Actinoptychus senarius Ehrenberg Cretaceous to Recent
Actinoptychus splendens Ralfs Pliocene to Recent
Auliscus caelatus var. constricta Rattray L. Miocene to M. Pliocene
Biddulphia rhombus Smith L. Miocene to Recent
Biddulphia tuomeyi Roper L. Cretaceous to Recent
Coscinodiscus gigas var. diorama Grunow M. Miocene to Recent
Coscinodiscus nitidus Gregory L. Cretaceous to Recent
Coscinodisucs nodulifer Schmidt U. Miocene to Recent
Coscinodiscus oculusiridis Ehrenberg L. Eocene to Recent
Coscinodiscus radiatus Ehrenberg Eocene to Recent
Cussia paleacea Schrader M. Miocene to Recent
Cussia tatsunokuchiensis Schrader Pliocene to Recent
Diploneis crabo Ehrenberg L. Miocene to Recent
Diploneis ornata var. spinifera L. Miocene to Recent
Melosira weistii Smith Miocene to Recent
Navicula hennedyi Smith L. Miocene to Recent
Navicula Dennata Schmidt Miocene to Recent

Nitzschia imperforata Andrews
Opephora schwartzii Petit
Paralia sulcata Cleve
Podosira stelligera Mann

Thalassiosira oestrupii Proschikina-Laurenko
G. S. Morgan, personal communication
Caloosahatchee Formation
Blancan vertebrate assemblage 2.0-2.2
J. M. Covington, personal communication
Core W-16242
E. Pliocene calcareous nannoplankton range

L. Miocene to Recent
Cretaceous to Recent
Miocene to Recent
Pliocene to Recent



The exact placement of the Mio-Pliocene
boundary has been open to debate for many
years. Current data show that all or part of the
Peace River Formation is Early Pliocene in age
based on calcareous nannofossils (J. M.
Covington, personal communication), diatoms
(Klinzing, 1987), and some questionable
forminifera (Peck, et al., 1979a; Peck et al.,
1979b). The question open to debate involves
the placement of the entire Peace River
Formation into the Pliocene. The reasoning
used to place the entire formation in the
Pliocene is that the major disconformity
separating the Peace River Formation from the
underlying Arcadia Formation appears to be the
discontinuity that correlates to the regression of
sea level at the end of Messinian time. There is
a possibility that some lower units within the
Peace River Formation may be Late Miocene in
age east of the platform center.

Twenty preliminary strontium isotope ages
have been measured on calcitic shells collected
from core W-16242 located at Captiva Island
on the Florida west coast. The ages were
calculated from laboratory determined strontium
isotope ratios using the regression method of
Hodell etal., (1990) and Hodell etal., (1991).
As shown in Figure 2, the Tamiaimi Formation
has a strontium isotope age range of 2.79 to
4.70 Ma. Caloosahatchee Formation strontium
isotope ages range from 1.71 to 2.35 Ma.
Although no shell samples were collected
within the Peace River Formation (single shell at
291 feet is assumed to be reworked) for age
determination, nannofossil ages determined by
J. M. Covington (personal communication)
show an early Pliocene age for the entire unit.
Strontium isotope ages determined in the
Arcadia Formation have an average age of
15.95 Ma. Therefore, a major hiatus occurs
across the disconformity with over 10 million
years of time missing at this location. A similar
hiatus was also found by Compton et al. (this
volume) in core W-10761 in Charlotte County
to the north of core W-16242.

The top of the Pliocene has been placed
within the Caloosahatchee and Anastasia
Formations based on the most current definition
of the Pliocene/Pleistocene time boundary
(Harland et al., 1990). The basal part of the
Caloosahatchee Formation contains a Blancan
vertebrate assemblage at several locations in

South Florida, including the MacAsphalt Pit in
Sarasota County and the Lehigh Acres Pit in
Lee County. Age determinations at the
MacAsphalt Pit (Jones et al., 1991) and at the
Lehigh Acres Pit (G. S. Morgan, personal
communication) confirm that the basal part of
what is considered to be the Caloosahatchee
Formation has an age range of 2-2.5 Ma. The
upper part of the Caloosahatchee Formation is
known to contain Pleistocene vertebrate fossils
(DuBar, 1958). Therefore, the Plio-Pleistocene
boundary lies on one of the intraformational
disconformities. Unfortunately, there are many
disconformities contained in the formation and
it is not possible to ascertain which discon-
formity correlates to the boundary. The same
type of problem occurs within the Anastasia
Formation along the east coast of Florida. The
upper part of this formation is late Pleistocene
in age, but it is a thick, poorly defined unit. It
will be necessary to properly define the vertical
boundaries of this unit, which may exclude the
lower section from the formation and leave only
the upper Pleistocene unit.

The Tamiami Formation is the primary
Pliocene formation in southern Florida. A
formal definition of the formation based on
separation of the unit by disconformities has
been suggested with some general correlation
of named and unnamed facies (Figure 2;
Missimer and Banks, 1982; Missimer, 1992).
Based on the global sea level curve proposed by
Vail et al., (1977), the age dates of Jones et al.
(1991), and the stratigraphic relationships, it is
suggested that the Tamiami Formation was
deposited between 2.8 and 4.7 Ma. In the
central platform area, there appears to be some
significant time missing at both the top and
bottom of the formation, evidenced by the
bounding disconformities.

Correlation of the nine or more defined
"members" of the Tamiami Formation is pro-
blematical in terms of horizontal continuity and
real time. There are some distinct discon-
formities observed between some of the
members or facies. At several locations, the
Buckingham Limestone Member is separated
from overlying units by a disconformity, such
as the contact with the Unnamed Limestone at
Lehigh Acres in Lee County. In southern Lee
County and northern Collier County, the Bonita
Springs Marl Member separates the Pinecrest






0 -

50 -

100 --



150 -

200 -

-- 0

- 100



- t?

- 400

-- 500

- 600


CORE W- 16242
















1__ 15 20 M ( M. COVINGTON )
.L__ ....... 4 ... .. . .

t --4-----




Figure 2. Preliminary Log of Core W-16242 and Chronologic Data.



- 700

232 - 760

........... .... .---.----










Vl '39V







0 V)





from the Ochopee. However, the composition
of each unit is quite variable and some lateral
grading occurs, particularly between quartz
sand units lying near the paleo-shoreline and
shallow marine carbonates on the middle of the
shelf. As additional stratigraphic data are
assembled in southern Florida, detailed cross-
sections will be prepared to revise the
relationships of the sediment facies.


Akers, W. H., 1974, Age of the Pinecrest
beds, South Florida: Tulane Studies in
Geology and Paleontology, v. 11, no. 2, p.

Bender, M. L., 1973, Helium-uranium dating
of corals: Geochimica et Cosmochimica
Acta, v. 37, p. 1229-1247.

Boggess, D. H., Missimer, T. M., and
O'Donnell, T. H., 1982, Hydrogeologic
sections through Lee County and adjacent
areas of Hendry and Collier counties,
Florida: United States Geological Survey
Water Resources Investigation Open-File
Report 81-638 (one sheet).

Dall, W. H., 1890-1903, Contributions to the
Tertiary fauna of Florida, with especial
reference to the silex-beds of Tampa and
the Pliocene beds of the Caloosahatchee
River: Transactions of the Wagner Free
Institute of Science of Philadelphia, v. 3,
parts 1-6, 1654 p.

DuBar, J. R., 1958, Stratigraphy and
paleontology of the late Neogene strata of
the Caloosahatchee River and southern
Florida: Florida Geological Survey Bulletin
40, 267 p.

1962, Neogene biostratigraphy of the
Charlotte Harbor area in southwestern
Florida: Florida Geological Survey Bulletin
43, 83 p.

Harland, W. B., Armstrong, R. L., Cox, A. V.,
Craig, L. E., Smith, A. G., and Smith,
D.G., 1990, A geologic time scale, 1989:
Cambridge University Press, Cambridge,
United Kingdom, 263 p.

Hodell, D. A., Meed, G. A., and Mueller, P. A.,
1990, Variation in strontium isotopic com-
position of seawater (8 Ma to present):
Implications for chemical weathering rates
and dissolved fluxes to the oceans:
Chemical Geology, v. 80, p. 291-307.

Mueller, P. A., and Garrido, J. R.,
1991, Variations in the strontium isotopic
composition of seawater during the
Neogene: Geology, v. 19, p. 24-27.

Jones, D. S., MacFadden, B. J., Webb, D. S.,
Mueller, P. A., Hodell, D. A., and Cronin,
T. M., 1991, Integrated geochronology of
a classic Pliocene fossil site in Florida:
Linking marine and terrestrial
biochronologies: Journal of Geology, v.
99, no. 5, p. 637-648.

Ketcher, K. M., 1992, Stratigraphy and environ-
ment of Bed II of the "Pinecrest" beds at
Sarasota, Florida, in Scott, T. M., and
Allmon, W.D., eds., The Plio-Pleistocene
stratigraphy and Paleontology of Southern
Florida: Florida Geological Survey Special
Publication 36, p. 167-178.

Klinzing, S. L., 1987, The LaBelle Clay of the
Tamiami Formation: Unpublished M.S.
thesis, Department of Geology, Florida
State University, 74 p.

Missimer, T. M., 1978, The Tamiami Formation
Hawthorn Formation contact in South-
west Florida: Florida Scientist, v. 14, p.

1992, Stratigraphic rela-
tionships of sediment facies within the
Tamiami Formation of Southwest Florida:
Proposed intra-formational correlation: in
Scott, T. M., and Allmon, W.D., eds., The
Plio-Pleistocene stratigraphy and
Paleontology of Southern Florida: Florida
Geological Survey Special Publication 36,
p. 167-178.


and Banks, R. S., 1982,
Miocene cyclic sedimentation in western
Lee County, Florida, in Scott, T. M., and
Upchurch, S. B., eds., Miocene Geology of
Southeastern United States: Florida
Bureau of Geology Special Publication 25,
p. 285-299.

and Gardner, R. A., 1976,
High-resolution seismic reflection profiling
for mapping shallow aquifers in Lee
County, Florida: U.S. Geological Survey
Water Resources Investigations INTIS, WRI
76-45, 30 p.

Olsson, A. A., 1964, Geology and stratigraphy
of southern Florida, in Olsson and Petit,
Some neogene mollusca from Florida and
the Carolinas: Bulletin of American Paleon-
tology, v. 47, No. 217, p. 509-574.

Parker, G. G., Fergus, G. E., and Love, S. K.,
1955, Water resources of southeastern
Florida: United States Geological Survey
Water Supply Paper 1255, 965 pp.

Peck, D. M., 1976, Stratigraphy and paleo-
ecology of the Tamiami Formation in Lee
County, Florida: M.S. Thesis, Dept. of
Geology, Florida State University, 249 p.

Missimer, T. M., Slater, D. H.,
Wise, S. W., Jr., O'Donnell, T. H., 1979a,
Late Miocene glacial-eustatic lowering of
sea level: Evidence from the Tamiami
Formation of South Florida: Geology, v. 7,
p. 285-288.

Slater, D. H., Missimer, T. M.,
Wise, S. W., Jr., and O'Donnell, T. H.,
1979b, Stratigraphy and paleoecology of
the Tamiami Formation in Lee and Hendry
counties, Florida: Transactions of the Gulf
Coast Association of Geological Societies,
v. 29, p. 328-341.

Vail, P. R., Mitchum, R. M., Jr., Thompson, S.,
III, 1977, Global cycles of sea levels
changes in Payton, C. E., ed., Seismic
stratigraphy Applications to Hydrocarbon
Exploration: American Association of
Petroleum Geologists Memoir 26, p. 83-



Florida Geological Survey, Tallahassee, Florida

Cores from various geographic provinces in
Florida have been examined for nannofossils.
While biostratigraphic control in some cores is
inhibited by poor preservation and/or paleo-
environmental constraints, other cores contain
a sufficient amount of adequately preserved
nannofossils to provide good biostratigraphic
resolution. As may be expected, wells from
coastal areas yielded significantly more
abundant and diverse assemblages of nanno-
fossils than those further inland. Wells from
the eastern coastal areas adjacent to the
Atlantic Ocean generally yielded better
assemblages than those adjacent to the Gulf of
Mexico. It is unclear at this time how
nannofossil preservation has been affected by
ground-water circulation, but obliteration of
nannofossils from dissolution and recrystal-
lization may have been significant.


Nine southwestern Florida wells were
studied from Charlotte and Lee Counties,
including Charlotte Harbor. In general, the
cores may be characterized as containing
nannofossils of Early to Late Pliocene age at or
near the surface. At various depths above
150', nearly all cores in this area contained the
bioevent delimited by Reticulofenestra
pseudoumbilica and Sphenolithus abies. The
(roughly coinciding) extinction of these species
marks the top of Zone CN11 (Okada and Bukry,
1980), which also coincides with the boundary
between the Early and Late Pliocene. This
bioevent is among the more reliable datums
used by nannofossil biostratigraphers in the
Gulf of Mexico area.

Only sporadic additional age determinations
can be made in these wells. In one core from
eastern Lee County, a sample from 160' yielded
nannofossils identified as Discoaster bollii, D.
neohamatus, D. hamatus, and D. calcaris. This
assemblage indicates an age of CN7 of the
earliest Late Miocene. The deepest sample

(312') from a core from central Charlotte
County yielded an assemblage including
Sphenolithus heteromorphus, which occurs in
Zones CN3-4 of the latest Early to earliest
Middle Miocene. Another core taken from
southernmost Lee County yielded a sample
from 504' containing Helicosphaera ampliaperta
which ranges through Zones CN2-3 of the late
Early Miocene.


Three wells from the coastal area of
Walton County in the panhandle of Florida all
contain sufficiently abundant nannofossils to
provide good biostratigraphic information. As
in the wells of southwestern Florida described
above, the bioevent delimited by the extinction
of Reticulofenestra pseudoumbilica and
Sphenolithus abies is consistently present,
providing a solid assignment of the boundary of
the Early and Late Pliocene (Zones CN11/12).

A hiatus is evident in these wells, with
sediments assigned to Zone CN11 directly over-
lying sediments assigned to Zone CN4-6 ages.
Species used to determine ages of the lower
sediments include Coccolithus miopelagicus,
Discoaster deflandrei, and Sphenolithus


One well from the eastern coastal Indian
River County yielded abundant and diverse
nannofossils and thus several reliable age
determinations. Available samples began at
126' and at 128' the samples contain nanno-
fossils of Early Pliocene age. The Late Miocene
nannofossil Discoaster quinqeramus was
encountered at 188'. The range of this species
is restricted to CN9. The sample from 221'
contained several important species whose
extinction defines CN8 of the early Late
Miocene. These species include Discoaster
bollii, D. neohamatus, D. neorectus, and D.
prepentaradiatus. After a long barren interval
beginning at 230', the sample from the bottom


of the well (332') yielded Cyclicargolithus
abisectus, C. floridanus, and Sphenolithus
distentus. While the first two of these species
may be found in the earliest Miocene, the
extinction of S. distentus occurs in CP19 of the
latest Oligocene.


Okada, H., and Bukry, D., 1980, Supplemen-
tary modification and introduction of code
numbers to the low-latitude coccolith
biostratigraphic zonation: Marine
Micropaleontology, v. 5, n. 3, p. 321-325.



of Geology, Florida State University, Tallahassee 32306, 2Tufts University, Medford,
Massachusetts 02155, 3Syracuse University, New York 13244

The west Florida continental slope in the
northeast Gulf of Mexico is an area of interest
to researchers from both industry and academia
for several reasons. It is situated within the
same latitudinal belt that has seen active
industry exploration in the northern Gulf. In
contrast to the greatly expanded, predominantly
plastic sedimentary sequences that characterize
the Cenozoic strata of the petroleum province
to the west where salt movements create struc-
tural traps, the west Florida slope provides a
much thinner but more continuous pelagic
carbonate sequence on a tectonically stable
margin. As such, the oceanic sequences along
the Florida slope can be used to establish
standard biostratigraphic and chemostrati-
graphic reference sections for the region as well
as a monitor of sea level fluctuations and
paleoceanographic changes.

Neogene calcareous nannofossils have
been studied from seven core holes emplaced
along the west Florida ramp slope by a
consortium of petroleum companies headed by
Exxon. The holes were interval cored and tied
together by seismic networks (see summaries
by Mitchum, 1978 and Mullins et al., 1988).
Nannofossils are generally well preserved in
the Pliocene/Pleistocene sections, which are
largely continuous. Preservation is pristine in
the Upper Miocene but diminishes to moderate-
ly good in the Lower Miocene.

Our core study indicates that considerably
more Neogene section is present on the slope
edge than reported by Mitchum (1978), who
used primarily seismic stratigraphy and micro-
fossil age determinations made during the mid-
1960s; however, the Oligocene turns out to be
absent in our core CH 30-43.

Stratigraphic discontinuities were delin-
eated in the Middle and/or Upper Miocene of
EXXON coreholes CH 29-42, CH 30-43, CH

31-44, CH 32-45, CH 35-46, CH 34-47, and
CH 33-48. Seismic stratigraphic analysis
suggests that a Middle to Late Miocene hiatus
was caused primarily by the invigoration of the
Florida Loop Current, perhaps due to the
closure of the Isthmus of Panama. This
resulted in a marked change in style of the
construction of the ramp from progradational to
aggradational, as seen in seismic profiles, as
illustrated by the change from Unit I to Unit II
on the profile in Figure 1.

This study has been used to support an
Ocean Drilling Program proposal for future
drilling. It is hoped that the entire Cenozoic
section can be captured to establish a contin-
uously cored reference section for the northern
Gulf Coast Region.


Mitchum, R. M., Jr., 1978, Seismic strati-
graphic investigation of west Florida slope,
Gulf of Mexico: in Bouma, A. H., Moore,
G. T., & Oil-Trapping Characteristics of the
Upper Continental Margin: American
Association of Petroleum Geologists
Studies in Geology, v. 7, p. 193-223.

Mullins, H. T., Gardulski, A. F., Hine, A. C.,
Melillo, A. J., Wise, S. W., Jr., Applegate,
J., 1988, Three-dimensional sedimentary
framework of the carbonate ramp slope of
central west Florida: a sequential seismic
stratigraphic perspective: Geological
Society of America Bulletin, v. 100, p.



West Florida Slope Stratigraphic Framework
Physiographic Provinces

Outer Slope I

I liatis

(Modified from Mitchum, 1978)

Figure 1. Profile across the northwest Florida carbonate ramp slope.



Department of Earth Sciences, University of North Carolina at Wilmington 28403; and Florida
Museum of Natural History, University of Florida, Gainesville 32611


Of the 19 barnacle species currently recog-
nized in the Florida Neogene, less than one-
third are known to occur outside of the state.
The high degree of endemism suggested by
these numbers is probably an artifact resulting
from our incomplete knowledge of Neogene
faunas in Florida and adjacent regions. The
near absence of exposed Neogene marine depo-
sits in the Gulf Coastal Plain, the virtual
absence of data on the Neogene barnacle fauna
of the Caribbean Basin, and the current gaps in
our knowledge of the composition of the Florida
fauna, limit our ability to develop a meaningful
biogeographic synthesis. Nevertheless, the
known fauna poses some interesting biogeo-
graphic problems, some of which have been
recognized in other, much better known
invertebrate groups, such as the Mollusca and
the Echinodermata.

The present discussion focuses on three of
these problems:
1) The Florida Miocene fauna has more in
common with the eastern Atlantic-western
Tethyan fauna than it does with the
Atlantic Coastal Plain fauna;
2) The Florida Pliocene fauna includes
genera that were also present in the
Pliocene of the Pacific Coast of North
America and are now restricted to the
eastern Pacific; and
3) The Florida Neogene fauna has little in
common with the modern faunas of the
Floridian and Carolinian provinces.


Only a few barnacles have been described
from the Florida Miocene, and these are either
from the Lower Miocene (Aquitanian) Para-
chucla and Penney Farms Formations of north-
ern Florida, or the Lower Miocene (Burdigalian)
Chipola Formation of the Florida Panhandle.

The Aquitanian species include Balanus
reflexus, one of the earliest members of the
modern and diverse B. amphitrite complex, and
Concavus crassostricola, otherwise known from
the Aquitanian of North Carolina (Zullo, 1984;
Zullo and Portell, 1991). Balanus reflexus is
related to Balanus halosydne, recently described
from the upper Oligocene (Chattian) of North
and South Carolina and the Lower Miocene
(Aquitanian) of North Carolina (Zullo et al.,
1992). Concavus crassostricola is the only
known Western Hemisphere representative of
this Late Oligocene to early Pleistocene Tethyan

The two Chipola species, Actinobalanus
floridanus and the coral barnacle Ceratoconcha
n. sp. 1, are particularly interesting because
their closest relatives are found in the Lower
Miocene of western Europe (Zullo and Perreault,
1989; Zullo and Portell, in press). Actino-
balanus, like Concavus, is a Tethyan genus,
ranging from the Early Miocene (Burdigalian) to
the early Pleistocene. Actinobalanus floridanus
is most similar to A. collins from the
Burdigalian of Belgium. Species similar to the
Chipola species of Ceratoconcha are found in
the Miocene of western Tethys and Paratethys,
the Caribbean Miocene, and the Miocene and
Pliocene of Florida. Ceratoconcha n. sp. 1 is
most similar to C. rangifrom the lower Miocene
of the Aquitaine basin and C. sanctacrucensis
from the Polish middle Miocene.



Present knowledge of the Florida Pliocene
fauna is based almost exclusively on collections
from the Jackson Bluff Formation in the Florida
Panhandle, and the various named and un-
named facies of the Tamiami (broad sense) and
Caloosahatchee Formations in southwest
Florida. For the purpose of this discussion, we


are using the nomenclature and correlations
based on the preliminary sequence stratigraphic
analysis proposed by Zullo and Harris (1992).

The nomenclature applied to the Tamiami
Formation is an outgrowth of the stratigraphic
revisions proposed by Hunter (1968) and
Petuch (1982). The formation is divided into
lower and upper parts. The lower Tamiami
includes Petuch's (1982) units 11 and 10 in
Sarasota County, and is equivalent to the
Murdock Station Member of Hunter (1968).
The upper Tamiami includes Petuch's (1982)
beds 9 through 2 in Sarasota County, and is
essentially equivalent to Hunter's (1968)
Pinecrest Member. The upper Tamiami is
further subdivided into the lower and upper
Pinecrest beds at, an unconformity that is
readily observed between Petuch's (1982) units
4 and 3 in quarry exposures in Sarasota
County. Zullo and Harris (1992) assigned the
lower Tamiami Formation and the lower
Pinecrest beds to Coastal Onlap Cycle TB3.6 of
Haq etal. (1987), and the upper Pinecrest beds
to Cycle TB3.7. The overlying Caloosahatchee
Formation, represented by Petuch's unit 1 in
Sarasota County, was assigned to the upper-
most Pliocene Cycle TB3.8. Based on biostrati-
graphic evidence, the Jackson Bluff Formation
was correlated with the lower Tamiami-lower
Pinecrest interval and assigned to Cycle TB3.6.

Earlier Pliocene cycles (TB3.4, TB3.5) of
Zanclean age have not been recognized in
southwestern Florida. Cycle TB3.6, the oldest
recognized cycle, spans the Zanclean-
Piacenzian boundary, and Cycles TB3.7 and
TB3.8 are Piacenzian in age. To the north, in
North Carolina and Virginia, Cycles TB3.6 and
TB3.7 are represented by Zone 2 of the York-
town Formation, and Cycle TB3.8 by the
Chowan River Formation. The proposed
nomenclature and sequence stratigraphic model
are graphically depicted in Figure 1.

Lower Tamiami Formation (TB3.6)

Five species are known from the lower
Tamiami Formation, including three concavines,
one species of Balanus, and a species of
Ceratoconcha. The concavines are: Arossia
glyptopoma, also known from Zone 2 of the
Yorktown Formation (TB3.6 Cycle) in North
Carolina and Virginia; Chesaconcavus

tamiamiensis, which is closely related to a
species from Zone 2 of the Yorktown; and
Tamiosoma advena, the only eastern North
American species of a genus that is otherwise
known only from the middle Miocene through
Recent of the Pacific Coast of North America.
Balanus newburnensis is a member of the B.
amphitrite complex, and is related to the latest
Pliocene-Recent western Atlantic-Caribbean
species B. venustus. Ceratoconcha n. sp. 2,
found in Septastrea, is the last survivor of the
widespread and diverse tropical Atlantic
Miocene subgroup of Ceratoconcha.

Lower Pinecrest beds (TB3.6)

Five species, including one balaninae, one
concavine, and three coral barnacles occur in
the lower Pinecrest beds of Sarasota County.
Balanus newburnensis, which is relatively rare
in the underlying lower Tamiami, is abundant in
the lower Pinecrest. Paraconcavus sara-
sotaensis, the characteristic red barnacle of the
lower Pinecrest, is definitely known only from
this unit, but may occur in the underlying lower
Tamiami, and is closely related to Paraconcavus
ta/quinensis of the Jackson Bluff Formation.

Hermatypic and ahermatypic corals are
abundant at some horizons in the lower Pine-
crest of Sarasota County, and have yielded
three genera of coral barnacles. Eocerato-
concha weisbordi, occurring in the hermatypic
coral Solenastrea, is the youngest known
representative of a six-plated genus that was
widely distributed throughout the Caribbean
during the Miocene. A new genus and species
of coral barnacle, a four-plated form found in
the hermatypic coral Diploria, is known only
from the lower Pinecrest in Sarasota County.
Ceratoconcha prefloridana, found in
Siderastrea, is the earliest known representative
of the modern tropical western Atlantic-
Caribbean subgroup of Ceratoconcha.

Upper Pinecrest beds (TB3.7)

No species have been identified from the
upper Pinecrest, although shells of balanines
are present in the unit.




-----.- N19/20 ----- ------------
condensed interval TB3.6 -
transgressive lower TAMIAMI FM. BLUFF FM.

Figure 1. Sequence stratigraphy and correlation of Pliocene units in southern Florida and the Florida
Panhandle (after Zullo and Harris, 1992).


lae Balanus venustus
Piacenzian Ceratoconcha prefloridana
Chelonibia testudinaria





Tamiosoma advena
Arossia glyptopoma
Paraconcavus sarasotaensis
Paraconcavus talquinensis
Chesaconcavus tamiamiensis
Balanus newburnensis
Balanus ochlockoneensis
Ceratoconcha n. sp. 2
Eoceratoconcha weisbordi
pyrgomatid n. gen and sp.
Scalpellum multangulatum

no current record for middle ar
SActinobalanus floridanus
SBurdigalian Ceratoconcha n. sp. 1
0 ian Balanus reflexus
Aquita Concavus crassostricola


:ene barnacle fauna



Figure 2. Biogeographic affinities of the Neogene barnacle fauna of Florida.


Caloosahatchee Formation (TB3.8)

Barnacles are common in the Caloosa-
hatchee, but few species have been identified.
Ross and Newman (1967) recognized three
species in this unit, including the earliest record
of the extant balanine species Balanus
venustus, the coral barnacle Ceratoconcha
prefloridana, originally described from Manicina
(Brooks and Ross, 1960) and now known to
occur also in Dichocoenia as well, and the
extant, cosmopolitan turtle barnacle Chelonibia

Jackson Bluff Formation (TB3.6)

Eight species hpve been described or iden-
tified from the Jackson Bluff Formation in the
Florida Panhandle (Ross, 1965; Weisbord,
1966; Ross and Newman, 1967; Spivey,
1977). Preliminary results of a re-study of this
fauna suggest that only four or five may be
valid. Scalpellum multangulatum, the only
stalked barnacle known from the Florida
Neogene, occurs in the Jackson Bluff. This
extant western Atlantic-Caribbean species was
a common element of the nearshore shelf fauna
during the Late Pliocene, and is additionally
known from localities in North and South
Carolina and Virginia. Two concavines are
present in the Jackson Bluff fauna. As
indicated above, Paraconcavus ta/quinensis is
closely related to P. sarasotaensis from the
lower Pinecrest. "Balanus" leonensis
specimens attributed to the Zone 2 Yorktown
species Chesaconcavus proteus may represent
the lower Tamiami species Chesaconcavus
tamiamiensis. Balanus ochlockoneensis is the
only Florida Neogene representative of the
extant, cosmopolitan B. trigonus group, and is
related to the extant, warm water, amphi-
American species B. calidus. Of the remaining
barnacles attributed to the Jackson Bluff fauna,
two are nomina dubia, based on shells without
opercular plates, and one is considered to have
affinities with B. improvisus, an extant brackish
water species known from the Pleistocene of
the Atlantic Coastal Plain and Florida.


Early Miocene Transatlantic Connection

Although the Early Miocene faunal sample

is small, the marked affinity of the known
species to the European Early Miocene fauna is
striking (Figure 2). With the exception of
Concavus crassostricola, Late Oligocene
(Chattian) and earliest Miocene (Aquitanian)
faunas of the middle Atlantic Coastal Plain are
quite distinct from their European counterparts.
Burdigalian faunas of the middle Atlantic
Coastal Plain are also distinct, but one extant
eastern Atlantic species, Fistulobalanus
pallidus, is abundant in the Kirkwood Formation
of Delaware, and has been reported from the
French Burdigalian (Davadie, 1963).

Similarities in the generic composition of
Tethyan and Floridian-Caribbean Miocene
faunas have long been recognized for other in-
vertebrate groups, including the hermatypic
corals (Vaughan and Wells, 1943) and the
echinoids (Gregory (1891). More specifically,
transatlantic affinities within the Chipola
molluscan fauna have been noted on several
occasions (see Vokes, 1989). Although it is
relatively easy to invoke transatlantic current
and climate patterns to explain similarities
between Miocene faunas of western Tethys and
the Caribbean, it is difficult to understand what
special hydroclimatic conditions existed during
the Burdigalian that enhanced this transatlantic
connection. Thus, the short-lived presence of
taxa such as Fistulobalanus pallidus and
Actinobalanus in the western Atlantic is not
readily explained.

Later Pliocene Eastern Pacific Connection

Pliocene invertebrate faunas of Florida and
the Caribbean exhibit considerable affinity to
Pliocene faunas of the eastern Pacific (Figure
2). Mansfield (1932) concluded that several
bivalves and an echinoid from the Florida
Pliocene were remarkably similar to species in
the upper Miocene to lower Pliocene Imperial
Formation in the Salton Trough at the head of
the Gulf of California. Woodring (1966) and
Smith (1991) emphasized the strong affinities
of the Caribbean and eastern Pacific Neogene
faunas, noting particularly the high percentage
of species in the Imperial Formation that were
the same as or closely related to Caribbean
taxa. The Imperial barnacle fauna is no
exception, and includes a species of Arossia
similar to A. glyptopoma, one of Tetraclita that
is probably conspecific with the tropical


western Atlantic-Caribbean species T.
stalactifera, and a species of Ceratoconcha
similar to Ceratoconcha n. sp. 2.

The affinities of the later Pliocene barnacle
fauna of Florida are, thus, quite different from
those of the Miocene fauna. Several taxa, in-
cluding the concavine genera Arossia,
Tamiosoma, and Paraconcavus, and the coral
barnacle subgenus Ceratoconcha are present in
the Pacific Coast Neogene, particularly in
southern California, Baja California, and the
Gulf of California. Others, including the
concavine genus Chesaconcavus and the coral
barnacles Eoceratoconcha, the members of the
western Atlantic subgroup of Ceratoconcha,
and the new genus and species of coral
barnacle, are not known outside of the western
Atlantic-Caribbean region. With the exception
of Ceratoconcha, all of these genera became
extinct in the western Atlantic during the Late
Pliocene and early Pleistocene, but Arossia,
Tamiosoma, and Paraconcavus survive in the
modern fauna of the eastern Pacific.

Similar relationships between the Florida
Pliocene fauna and the modern fauna of the
eastern Pacific have been discussed previously.
Olsson and Petit (1964) noted the presence of
two extant eastern Pacific bivalves, Raeta
undulata and Anadara tuberculosa, in the
Pinecrest beds, and species of the eastern
Pacific gastropod genera Malea, Perplicaria, and
Trochita, in the Pinecrest beds and Caloosa-
hatchee Formation. Jones and Portell (1988)
reported the presence of the extant eastern
Pacific asteroid Heliaster microbrachius in the
Tamiami Formation (Pinecrest beds equiva-

Although the Caribbean and Pacific
(Panamic province) faunas of the Neogene
tropical amphi-American province were never
homogeneous, major differentiation of the two
faunas occurred only after the development of
the Central American land barrier (3.5 3.1 Ma,
from references in Smith, 1991). Restriction of
Atlantic equatorial currents to the Caribbean
Basin, and the onset or enhancement of
upwelling along the Pacific Coast of Central
America and Mexico drastically altered
hydroclimatic conditions in the two regions.
The coral reef habitat virtually disappeared from
the Panamic province, together with a large

measure of the coralophilic fauna. On the other
hand, shallow water epibenthic forms, particu-
larly those in moderate to high energy environ-
ments flourished and continued to diversify in
the Panamic province. These changes may
explain the paucity of coral-inhabiting barnacles
and the survival of the concavines in the
Panamic province, but does not explain the
extinction of the concavines in the tropical
western Atlantic and Caribbean.

A Pliocene Atlantic Coast Barrier?

Later Pliocene barnacle faunas of south-
western Florida and the Florida Panhandle have
little in common with those of the middle and
southeastern Atlantic Coastal Plain, suggesting
that a major biogeographic barrier existed
between the two regions. Only three species,
Scalpellum multangulatum, Chelonibia
testudinaria, and Arossia glyptopoma, are
common to both areas and, with the exception
of A. glyptopoma, are extant forms. On the
other hand, free genetic exchange between
southern Florida and the middle Atlantic region
must have been possible during the Late
Miocene or Early Pliocene, as several later
Pliocene species in the two regions are
geminates, including Chesnconcavus
tamiamiensis/C. proteus and P. talquinensis/P.
sarasotaensis/P. prebrevicalcar. Although little
is known of the pre-Late Pliocene fauna of
Florida, the Late Miocene and Early Pliocene
faunas of the middle Atlantic Coastal Plain
contain precursors of these Late Pliocene
geminate species.

The nature and position of the barrier are
unknown, in part because of the absence of
data from northern Florida and Georgia.
Because of cooling trends in the North Atlantic
basin related to the buildup of ice in the Arctic,
it is likely that temperature was a major factor
in limiting species ranges. The later Pliocene
faunas of Virginia and North Carolina are
essentially identical, and that of South Carolina
is more northern than Floridian in composition,
suggesting that the provincial boundary is south
of South Carolina.

The Extant Fauna

A major, unresolved problem is the origin
of the modern barnacle fauna of the Floridian


and Carolinian provinces. The majority of
species in the modern fauna are either not
known from the fossil record, or present only in
Pleistocene deposits. For example, common,
large, and readily preservable shallow water
Floridian barnacles such as Tetrac/ita
stalactifera and Megabalanus tintinnnabulum
are unknown as fossils in Florida, but do occur
in upper Pleistocene deposits of northern South
America. The extant and widely distributed
Atlantic species, Balanus improvisus, B.
eburneus, and B. venustus make their first
appearance in upper Pleistocene deposits of the
Atlantic Coastal Plain and Florida and, with the
exception of B. venustus, have no recognizable
precursors in Neogene deposits of the region.

The apparent sudden appearance of the
modern fauna in the Pleistocene is probably a
function of our lack of knowledge concerning
Neogene faunas in the Caribbean and along the
margins of the Gulf of Mexico. However,
Florida is not the only area where the Neogene
fauna differs markedly from that of the
Pleistocene and Recent (e.g., Pacific Coast of
North America, Japan). This major shift is a
boon for the biostratigrapher, but a vexing
problem for the biogeographer.


Brooks, H. K., and Ross, A., 1960, Pyrgoma
prefloridanum, a new species of cirriped
from the Caloosahatchee Marl (Pleistocene)
of Florida: Crustaceana, v. 1 p. 353-365.

Davadie, C., 1963, Etude des Balanes d'Europe
et d'Afrique. Syst6matique et structure
des Balanes fossiles d'Europe et d'Afrique.
Editions du Centre National de la
Recherche Scientifique, Paris, 146 p.

Gregory, J. W., 1891, The relations of the
American and European echinoid faunas:
Geological Society of America Bulletin, v.
3, p. 101-108.

Haq, B. U., Hardenbol, J., and Vail, P. R.,
1987, Chronology of fluctuating sea levels
since the Triassic: Science, v. 235, p.

Hunter, M. E., 1968, Molluscan guide fossils in
late Miocene sediments of southern Florida:
Transactions, Gulf Coast Association of
Geological Societies, v. 18, p. 439-450.

Jones, D. S., and Portell, R. W., 1988,
Occurrence and biogeographic significance
of Heliaster (Echinodermata: Asteroidea)
from the Pliocene of southwest Florida:
Journal of Paleontology, v. 62, p. 126-

Mansfield, W. C., 1932, Pliocene fossils from
limestone in southern Florida: United
States Geological Survey Professional
Paper 170-D, p. 43-51.

Olsson, A. A., and Petit, R. E., 1964, Some
Neogene mollusca from Florida and the
Carolinas: Bulletins of American
Paleontology, v. 47, no. 217, p. 505-574.

Petuch, E. J., 1982, Notes on the molluscan
paleoecology of the Pinecrest beds at
Sarasota, Florida with the description of
Pyruella, a stratigraphically important new
genus (Gastropoda: Melongenidae):
Proceedings of the Academy of Natural
Sciences of Philadelphia, v. 134, p. 12-30.

Ross, A., 1965, Scalpellum gibbum Pilsbry
(Cirripedia) in the Florida Miocene:
Crustaceana, v. 9, part 2, p. 219-220.

__ and Newman, W. A., 1967, Eocene
Balanidae of Florida, including a new genus
and species with a unique plan of "turtle-
barnacle" organization: American Museum
Novitates, no. 2288, 21 p.

Smith, J. T., 1991, Cenozoic marine mollusks
and paleogeography of the Gulf of
California: in Dauphin, J. P., and Simoneit,
B. R. T., eds., The Gulf and Peninsular
Province of the Californias: American
Association of Petroleum Geologists
Memoir 47, p. 637-666.

Spivey, H. A., 1977, Cirripedia from the
Jackson Bluff Formation (Miocene) of
Florida with the description of a new
species of Balanus: Proceedings of the
Academy of Natural Sciences of
Philadelphia, v. 128. p. 127-132.


Vaughan, T. H., and Wells, J. W., 1943,
Revision of the suborders, families, and
genera of the Scleractinia: Geological
Society of America, Special Papers, no. 44,
363 p.

Vokes, E. H., 1989, An overview of the Chipola
Formation, northwestern Florida: Tulane
Studies in Geology and Paleontology, v.
22, p. 13-24.

Weisbord, N. E., 1966, Some late Cenozoic
cirripeds from Venezuela and Florida:
Bulletins of American Paleontology, v. 50,
no. 225, 145 p.

Woodring, W. P., 1966, The Panama land
bridge as a sea barrier: American
Philosophical Society Proceedings, v. 110,
no. 6, p. 425-433.

Zullo, V. A., 1984, New genera and species of
balanoid barnacles from the Oligocene and
Miocene of North Carolina: Journal of
Paleontology, v. 58, p. 1312-1338.

and Harris, W. B., 1992, Sequence
stratigraphy of marine Pliocene and lower
Pleistocene deposits in southwestern
Florida: preliminary assessment: in Scott,
T. M., and Allmon, W. D., eds., The Plio-
Pleistocene stratigraphy and paleontology
of Southern Florida: Florida Geological
Survey Special Publication 36, p. 27-40.

and Perreault, R. T., 1989, Review
of Actinobalanus Moroni (Cirripedia,
Archaeobalanidae), with the description of
new Miocene species from Florida and
Belgium: Tulane Studies in Geology and
Paleontology, v. 22, p. 1-12.

and Portell, R., W., 1991, Balanoid
barnacles from the early Miocene
Parachucla and Penney Farms Formations,
northern Florida: Tulane Studies in
Geology and Paleontology, v. 24, p. 79-86.

and Portell, R. W., in press,
Revised classification and phylogeny of
coral-inhabiting barnacles (Cirripedia:
Archaeobalanidae and Pyrgomatidae) with
emphasis on the late Cenozoic fauna of the
Americas and Western Tethys: Journal of

_, Katuna, M. P., and Herridge, K. C.,
1992, Scalpellomorph and balanomorph
barnacles (Cirripedia) from the upper
Oligocene Ashley Formation, Charleston
County, South Carolina, South Carolina
Geology, v. 34, p. 57-67.




Florida Museum of Natural History, University of Florida, Gainesville, FL 32611-2035

Mammalian biochronology is an important
methodology in the correlation of Neogene
marine and terrestrial geologic units on the
Atlantic and Gulf Coastal Plains of the south-
eastern United States (Tedford and Hunter,
1984). Neogene land mammals are common in
Florida where there is a fairly complete
sequence of faunas dating from the Early
Miocene to the Late Pliocene (MacFadden and
Webb, 1982). This paper expands upon the
work of previous authors by incorporating many
newly discovered Miocene and Pliocene faunas,
in particular those that occur in predominantly
marine geological units. Vertebrates often play
a significant role in dating Neogene near-shore
marine deposits in Florida because many of
these geologic units lack microfossils and
macroinvertebrates and are unsuitable for
radioisotopic dating. Florida has the richest
Neogene land mammal faunas in eastern North
America, representing each of the seven
Miocene and Pliocene North American Land
Mammal Ages (NALMA). The nearest com-
parable sequence of Miocene land mammal
faunas occurs on the Gulf Coastal Plain in
southeastern Texas (Tedford etal., 1987). The
closest region where similar Pliocene land
mammal faunas can be found is the Great
Plains of Kansas, Nebraska, and west Texas
(Lundelius et al., 1987).

North American Land Mammal Ages are
biochrons characterized by a composite
assemblage of land mammals that co-existed in
North America during a particular interval of the
Cenozoic (Tedford et al., 1987; Woodburne,
1987). The characteristic mammalian
assemblage for each NALMA contains genera
and/or species that are restricted to, or have
their first or last appearance during, that age.
The relative age of Neogene mammalian faunas
in Florida and elsewhere in the southeastern
United States has been determined by biochro-
nological comparisons with faunas from
western North America, many of which have
been dated using radioisotopic methods (Ar/Ar,

K/Ar, etc.) and/or magnetic polarity strati-
graphy. Faunal heterochrony does not appear
to be a significant problem in the correlation of
Neogene land mammal faunas throughout the
North American continent (Flynn et al., 1984).
The temporal resolution available using the
North American land mammal biochronology is
currently about 0.5 to 1.0 Ma for the Neogene.

The definitions and chronology of the
Miocene and Pliocene NALMA follow Tedford et
al. (1987) and Lundelius et al. (1987). The
subdivisions and chronology of the Neogene
epochs and ages follow Berggren et a. (1985).
The Miocene (23.3-5.2 Ma) NALMA include
(from oldest to youngest): late Arikareean,
Hemingfordian, Barstovian, Clarendonian, and
early Hemphillian. The Pliocene (5.2-1.6 Ma)
NALMA include: late Hemphillian, Blancan, and
early Irvingtonian.

Scott (1988) noted that very few datable
fossil assemblages were known from the
Hawthorn Group in northern Florida. Miocene
land mammals are now known from five forma-
tions in the Hawthorn Group of northern
peninsular Florida and the eastern panhandle,
including the Parachucla Formation, Penney
Farms Formation, Torreya Formation, Marks
Head Formation, and Statenville Formation, as
well as two Hawthorn Group units in central
Florida, the Arcadia Formation and Bone Valley
Formation (= Bone Valley Member of the Peace
River Formation of Scott, 1988). The upper
Bone Valley Formation is the only unit in the
Hawthorn Group that is Pliocene in age. Figure
1 is a map of Florida showing the location of
the Miocene and Pliocene vertebrate fossil sites
discussed in the text.

About ten land mammal faunas from penin-
sular Florida are referable to the Late Oligocene
and Early Miocene Arikareean NALMA (29-20
Ma), three of which occur in marine deposi-
tional environments. The Parachucla Forma-
tion, exposed along the Suwannee River near


v 0
t 6



Figure 1. Outline map of Florida showing location of Neogene vertebrate faunas discussed in text.
Sites are listed in order by North American Land Mammal Age from oldest to youngest. early Ariareean
(latest Oligocene or earliest Miocene): 1. White Springs Local Fauna (LF), Columbia and Hamilton
Counties, Parachucla Formation; 2. Cowhouse Slough LF, Hillsborough County, Tampa Member of the
Arcadia Formation; late Arikareean (Early Miocene): 3. Oreodont Site, Marion County, Penney Farms
Formation; 4. Martin-Anthony Roadcut, Marion County, Penney Farms Formation; early Hemingfordian
(late Early Miocene); 5. Seaboard LF, Leon County, Torreya Formation; 6. Griscom Plantation LF, Leon
County, Torreya Formation; 7. Thomas Farm LF, Gilchrist County; late Hemingfordian (latest Early
Miocene); 8. Midway LF, Gadsden County, Dogtown Member of the Torreya Formation; 9. Brooks Sink
LF, Bradford County, Marks Head Formation; early Barstovian (early Middle Miocene); 10. Willacoochee
Creek Fauna, Gadsden County, Dogtown Member of the Torreya Formation; 11. Bird Branch LF, Polk
County, Arcadia Formation; 12. Sweetwater Branch LF, Polk County, Arcadia Formation (?); late
Barstovian (Middle Miocene); 13. Ashville LF, Jefferson County, Statenville Formation (?); 14. Roaring
Creek LF, Hamilton County, Statenville Formation; 15. Bradley Fauna, Polk County, Bone Valley
Formation (=Bone Valley Member of the Peace River Formation); early Clarendonian (late Middle
Miocene); 16. Occidental Fauna, Hamilton County, Statenville Formation; 17. Agricola Fauna, Polk
County, Bone Valley Formation; latest Clarendonian/early Hemphillian (Late Miocene); 18. Gainesville
Creeks Fauna, Alachua County, undifferentiated Hawthorn Group; (Sites 19-21 are included in the
Archer Fauna, "Alachua Formation") 19. Love Bone Bed LF, Alachua County, 20. McGehee Farm LF,
Alachua County; 21. Mixon LF, Levy County; late early Hemphillian (latest Miocene): 22. Moss Acres
Racetrack LF, Marion County; 23. Withlacoochee 4A LF, Marion County; (Sites 24-28 are included in
the Manatee Fauna, Bone Valley Formation?); 24. Leisey 1C, Hillsborough County; 25. Port Manatee
LF, Manatee County; 26. Manatee Dam, Manatee County; 27. Braden River LF, Manatee County; 28.
Lockwood Meadows, Sarasota County; late Hemphillian (Early Pliocene): 29. Palmetto Fauna, Polk
County, Bone Valley Formation; late Blancan (Late Pliocene): 30. Macasphalt Shell Pit LF, Sarasota
County, Pinecrest Beds of the Tamiami Formation; earliest Irvingtonian (latest Pliocene): 31. De Soto
Shell Pit LF, De Soto County, Caloosahatchee Formation.


White Springs in Columbia and Hamilton
Counties in northernmost peninsular Florida,
has been considered very early Miocene
(Aquitanian) in age on the basis of planktonic
foraminifera from correlative subsurface strata
in Georgia (Huddlestun, 1988). The White
Springs Local Fauna (LF) is derived from the
Parachucla Formation and contains several land
mammals typical of the early Arikareean,
including the rodents Arikareeomys and
Leidymys, the rabbit Palaeolagus, and the horse
Miohippus (Morgan, 1989). The White Springs
LF compares most closely with late early
Arikareean faunas (25-23 Ma), indicating that
the Parachucla Formation may be in part latest
Oligocene (late Chattian). Figure 2 is a
correlation chart showing tle age and strati-
graphic relationships of the Florida Neogene
vertebrate sites discussed in this paper.

The Cow House Slough LF, collected from
a karst feature in the Tampa Member of the
Arcadia Formation (=Tampa Limestone, see
Scott, 1988) near Tampa, Hillsborough County
in central Florida, is also early Arikareean in
age. The Cow House Slough and White
Springs local faunas are similar in age based on
the co-occurrence of Arikareeomys,
Palaeolagus, and Miohippus. The Cow House
Slough land mammals suggest that at least a
portion of the Tampa Member is Late Oligocene
in age and support the correlation of the Tampa
Member with the Parachucla Formation (Scott,

Two small vertebrate faunas occur in strata
referred to the Penney Farms Formation at the
Martin-Anthony road cut in Marion County
(MacFadden, 1980; Tedford eta., 1987; Scott,
1988). A marine limestone unit of the Penney
Farms Formation at this locality contained the
oreodont Phenacocoelus luskensis (see
MacFadden, 1980), a primitive artiodactyl
typical of the early late Arikareean NALMA
(very early Miocene, late Aquitanian or early
Burdigalian, 23-21 Ma). A small vertebrate
assemblage collected somewhat higher in this
same stratigraphic section, the Martin-Anthony
LF, is also late Arikareean age (Tedford and
Hunter, 1984). The Penney Farms Formation
has been correlated with the Parachucla
Formation and the Tampa Member of the
Arcadia Formation (Scott, 1988). The land
mammal faunas indicate that the late

Arikareean Oreodont Site and Martin-Anthony
LF are slightly younger than the early
Arikareean White Springs and Cow House
Slough local faunas.

Five Florida land mammal faunas from
deposits of marine origin are referable to the
Early Miocene Hemingfordian NALMA (20-16.5
Ma). Three of these Hemingfordian sites, the
Seaboard, Griscom Plantation, and Midway
local faunas, occur in the Torreya Formation in
the eastern Florida panhandle. The Seaboard
LF, collected from the lower Torreya Formation
in Tallahassee, Leon County, compares very
closely in age with the late early Hemingfordian
(Early Miocene, middle Burdigalian, 19-18 Ma)
Thomas Farm LF derived from a sinkhole
deposit in Gilchrist County in northern
peninsular Florida. Thomas Farm is one of the
best known Miocene vertebrate faunas in
eastern North America. The Seaboard and
Thomas Farm local faunas share the horses
Anchitherium clarencei, Archaeohippus
blackbergi and Parahippus leonensis, the
rhinoceros Menoceras, the protoceratid
artiodactyl Prosynthetoceras, and the
heteromyid rodent Proheteromys. A second
fauna from the lower Torreya Formation, the
Griscom Plantation LF in Leon County, is also
early Hemingfordian in age, as it shares
Parahippus leonensis and the small dog
Cynodesmus iamonensis with Thomas Farm
(Bryant et a., 1992). The late Hemingfordian
Midway LF, collected from a fuller's earth mine
in Gadsden County, was derived from the
Dogtown Member in the upper Torreya
Formation (MacFadden et al., 1991; Bryant et
al., 1992). The Midway LF contains the
horses, Anchitherium clarencei, Archaeohippus
blackbergi, and Merychippus gunteri, the
dromomerycid artiodactyl Aletomeryx, and the
rodents Proheteromys and Mesogaulus,
indicating a late Hemingfordian age (late Early
Miocene, late Burdigalian, 18-16.5 Ma).

Strata referred to the Marks Head Forma-
tion from Brooks Sink, Bradford County in
northern peninsular Florida (Scott, 1988) have
produced a predominantly marine vertebrate
fauna that also includes land mammals (Morgan
and Pratt, 1988). The association of the horses
Archaeohippus blackbergi and Merychippus
gunteri and the rodents Proheteromys and
Mesogaulus in the Brooks Sink LF indicates a


NORTH 0 ()
iCaloosahatchee Fm::- IRVINGTONIAN n S
De Soto S. P LF
Macasphalt S. P LF L z
"IPinecrest Beds" j111 r
Z< _J
Tuca Lee Creek Palmetto F 5
Hills LF. LA: LF, NC L
Citronelle Frn Yorktown Fm :::::::::::::::::::::::: ::::::: W ;
--- Bone Valley Fm. -
Withlacoochee 4A LF Manatee F E
--- ::::::::::::::: :::::::::::: : : Bone Valley Fm (?) -
Mobile LF, ALcGee Mixon LF ... -..-- -
( Mobile LF.L j Gamiesville Cr F]: Farm LF 0
Hawthorn Gp undiff. Love Bone Bed LF
...........;...... .. F..:.. !. "Alachua Clays" i 10iiiiii.iiiiiiiii iiiiiiiI

Occidental F Agrcola F

| Statenville LF. GA L Ashlle LF | 1 Bradley F -
l,- _. .- : ............... ................L.........

Roaring Creek LF
tatenvillei ::::::::::::::::::::::::::::::F::: I

CalverVChoplank Fm l BARSTOVIAN O
Dogtown Mem 11111 Arcadia Fm 5 0
1111 l i Sweetwater Branch LF E S
Willacoochee Cr F BirdBranch LF |||||
Porters Landing LF, GA Midway LF Brooks Sink LF
Marks Head Fm L z
Griscom Plantation LF
Farmingdale F. NJ LF Thomas Farm LF HEMINGFORDIAN |

IIIKrkwood Fm i1IIIIIll:llTorreya Fm c
Martin-Anthony LF 2

Oreodont Site

IIPenne1y Farms Fm.
white Springs LF ii Cowhouse Slough LF
:;;;: ParachuciaFm.:::;:l Tampa Mem
Arcadia Fm 111:1111 25 ARIKAREEAN

E 8


Figure 2. Correlation chart showing the age and stratigraphic relationships of selected Florida Neogene
land mammal faunas discussed in the text, in particular faunas that occur in marine geological units.
Correlative land mammal faunas from the Atlantic and Gulf Coast Plains, exclusive of Florida, are shown
in the left hand column. Radiometric ages and duration of the North American Land Mammal Ages are
from Tedford et al. (1987). Radiometric ages of the Epochs and Standard European Stages/Ages are
from Berggren et al. (1985). Abbreviations used in the chart are: Fauna (F); Local Fauna (LF); Mega-
anna (Ma)=millions of years; Group (Gp.); Formation (Fm.); Member (Mem.); undifferentiated
(undiff.) =geological unit unknown; Shell Pit (S. P.); and Creek (Cr.). The patterns used for the
geological units (dots and vertical lines) are not intended to reflect lithology.


late Hemingfordian age and a close similarity
with the Midway LF. Correlation of the Marks
Head Formation with the Torreya Formation
(Huddlestun, 1988) is corroborated by evidence
from land mammals.

The Middle Miocene Barstovian NALMA
(16.5-11.5 Ma) is represented by vertebrate
faunas from the eastern Florida panhandle and
the northern and central regions of the
peninsula. The early Barstovian Willacoochee
Creek Fauna, collected from a series of fuller's
earth mines in Gadsden County in the eastern
panhandle, is derived from the Dogtown Mem-
ber in the upper Torreya Formation (Bryant,
1991; Bryant et a., 1992). The Willacoochee
Creek Fauna is early Barstovian in age (early
Middle Miocene, Langhian, 16-15 Ma) based on
the presence of the rodents Copemys, Perog-
nathus, and Mylagaulus, three merychippine
horses, and the oreodont Ticholeptis. The age
of the Willacoochee Creek Fauna is corro-
borated by evidence from paleomagnetic strati-
graphy and strontium isotope chronology
(MacFadden et al., 1991; Bryant et al., 1992).

Late Barstovian land mammal faunas occur
in the Statenville Formation at the type locality
in Statenville, Echols County in southernmost
Georgia (Voorhies, 1974) and in the Roaring
Creek LF from the nearby Occidental Phosphate
Mine in Hamilton County, northernmost penin-
sular Florida (Morgan, 1989). The late
Barstovian Ashville LF occurs in supposedly
correlative strata in Jefferson County in the
easternmost panhandle (Olsen, 1963; Tedford
and Hunter, 1984). The Statenville LF contains
species of the horses Calippus, Cormohip-
parion, and Merychippus and the beaver
Eucastor, indicative of an early phase of the
late Barstovian (Middle Miocene, late Langhian
or early Serravallian, 14.5-13.5 Ma). Late
Barstovian land mammals from the Roaring
Creek LF, including the horses, Archaeohippus
sp., a small species of Merychippus, and
Calippus proplacidus, presumably were derived
from the lower unit of the Statenville
Formation. The majority of land mammals from
the Occidental Mine, comprising the Occidental
Fauna (Morgan, 1989), occur in the upper
Statenville Formation and are early Claren-
donian in age (late Middle Miocene, late
Serravallian, 11.5-10.5 Ma). Characteristic
early Clarendonian horses from the Occidental

Fauna include Calippus martini, Cormohipparion
occidentale, Pliohippus pernix, and Pseud-
hipparion curtivallum.

The Arcadia Formation and the overlying
Bone Valley Formation in central Florida have
produced at least six different vertebrate faunas
ranging in age from Middle Miocene (early
Barstovian) to Early Pliocene (late Hemphillian).
The Bird Branch LF from the Nichols Mine in
Polk County was collected high in the Arcadia
Formation. This fauna is early Barstovian in age
(early Middle Miocene, Langhian, 16.5-15.5
Ma) based on the presence of the equid
Merychippus cf. M. isonesus (Hulbert and
MacFadden, 1991) and an early species of the
rodent Copemys, one of the defining genera for
the Barstovian NALMA (Tedford et al. 1987).
The Bird Branch LF is similar to the
Willacoochee Creek Fauna from the Torreya
Formation (Bryant, 1991). The Sweetwater
Branch LF from the Phosphoria Mine in Polk
County was derived from the top of the Arcadia
Formation or the base of the Bone Valley
Formation, and appears to be slightly younger
than the Bird Branch LF. Hulbert and
MacFadden (1991) regarded the Sweetwater
Branch LF as early Barstovian in age (early
Middle Miocene, Langhian, 15.5-14.5 Ma)
based on the presence of the horses
Parahippus, Merychippus cf. M. brevidontus,
and Merychippus goorisi.

Land mammal faunas from the Bone Valley
Formation (= Bone Valley Member of the Peace
River Formation of Scott, 1988) include the
Middle Miocene Bradley and Agricola faunas
derived from the lower Bone Valley Formation
and the Early Pliocene Palmetto Fauna from the
upper pebble phosphate beds (Webb and
Hulbert, 1986). The Bradley Fauna is late
Barstovian (Serravallian, 12.5-11.5 Ma) based
on the occurrence of the horses Calippus
proplacidus, Megahippus, Pliohippus mirabilis,
and Protohippus perditus (Hulbert 1988), as
well as the dromomerycid Procranioceras cf. P.
skinneri and one of the earliest North American
proboscideans, the gomphothere Gompho-
therium cf. G. calvertense (Webb and Cris-
singer, 1983). The Bradley Fauna appears to
be slightly younger than the late Barstovian
faunas from the lower Statenville Formation in
northern Florida and southern Georgia. The
early Clarendonian (late Serravallian, 11.5-10.5


Ma) Agricola Fauna is characterized by the
horses Hypohippus affinus, Protohippus
supremus, Calippus martini, Cormohipparion
occidentale, and Pseudhipparion curtivallum
(Hulbert, 1988). The last three of these horses
also occur in the correlative early Clarendonian
Occidental Fauna from the upper Statenville
Formation in the Occidental Mine in northern
Florida (Morgan, 1989).

Land mammals occur in undifferentiated
sediments of the Hawthorn Group exposed in
creeks in the vicinity of Gainesville, Alachua
County, in northern Florida. Although the
Gainesville Creeks Fauna is primarily marine, a
rather diverse sample of horses is known from
Hawthorn sediments in the Gainesville area,
notably Coffrin Creek (Hulbert, 1988), including
Calippus elachistus, Calippus hondurensis,
Neohipparion trampasense, and Pseudhipparion
skinneri. The equids from the Gainesville
Creeks Fauna compare closely in age with
those from the Archer Fauna, a diverse land
mammal assemblage of latest Clarendonian and
early Hemphillian age (Late Miocene, middle
Tortonian, 9-8 Ma). The Archer Fauna incor-
porates a well known series of local faunas
derived from the "Alachua Clays," including the
Love Bone Bed and McGehee Farm in Alachua
County and the Mixon LF in Levy County
(Webb et al., 1981; Webb and Hulbert, 1986;
Hulbert, 1988).

Land mammals of late early Hemphillian
age (Late Miocene, late Tortonian, 8-7 Ma)
occur in a series of five sites located along the
southwestern Gulf Coast of Florida. These five
sites, collectively named the Manatee Fauna,
include Leisey 1C in Hillsborough County
(Hulbert, 1988; Hulbert and Morgan, 1989),
Braden River, Manatee Dam, and Port Manatee
in Manatee County (Webb and Tessman, 1968;
Hulbert, 1988), and Lockwood Meadows in
Sarasota County (MacFadden, 1986; Hulbert,
1988). Where these faunas have been
collected in place, the sediments resemble the
pebble phosphates of the upper Bone Valley
Formation (Webb and Tessman, 1968;
MacFadden, 1986; Hulbert and Morgan, 1989).
Based on the co-occurrence of certain equids,
including Cormohipparion ingenuum, Dino-
hippus sp., Nannippus minor, Neohipparion
eurystyle, and Pseudhipparion skinneri, Hulbert
(1988) correlated the Manatee Fauna sites with

the better known late early Hemphillian
Withlacoochee River 4A and Moss Acres Race-
track local faunas from Marion County in
northern Florida. The late early Hemphillian age
of the land mammals from the Manatee Fauna
sites, as well as their location near or slightly
above present sea level, suggests they were
deposited just prior to the Messinian (6.7-5.2

The late Hemphillian (earliest Pliocene,
early Zanclean, 5.2-4.5 Ma) Palmetto Fauna is
the most diverse of the vertebrate faunas from
the Bone Valley Formation. Characteristic late
Hemphillian land mammals in the Palmetto
Fauna include the bear Agriotherium
schneideri, the sabercat Megantereon hesperus,
the wolverine Plesiogulo marshall, the horses
Dinohippus mexicanus and Pseudhipparion
simpsoni, the artiodactyls, Hexameryx simpsoni
and Kyptoceras amatorum, and the probo-
scidean Rhynchotherium simpsoni. Pseudhip-
parion simpsoni, Kyptoceras amatorum, and the
borophagine dog, Osteoborus (=Borophagus)
dudleyi, are shared with the correlative Lee
Creek LF from the Yorktown Formation at the
Lee Creek Phosphate Mine in North Carolina
(Tedford and Hunter, 1984).

Following a gap of about 2 million years in
the Pliocene (4.5-2.5 Ma) during which no
terrestrial vertebrates are known from Florida,
a number of Late Pliocene (late Blancan and
earliest Irvingtonian) land mammal faunas occur
in the classic shell bed sequence of southern
Florida. Although the predominantly marine
Pinecrest Beds and Caloosahatchee Formation
are best known for their tremendously diverse
molluscan faunas, both of these units also
produce diagnostic Late Pliocene land mam-
mals. Several late Blancan (late Piacenzian,
2.5-1.9 Ma) land mammal faunas occur in the
Pinecrest Beds, the uppermost unit of the
Tamiami Formation, the best known of which is
the Macasphalt Shell Pit LF from the APAC Pit
in Sarasota County (Hulbert, 1987; Morgan and
Ridgway, 1987; Jones et al., 1991). The
Macasphalt Shell Pit LF is characterized by the
association of the three-toed horses Nannippus
and Cormohipparion with a suite of South
American mammals, including the ground sloth
Glossotherium, the armadillos Dasypus and
Holmesina, and the capybara Neochoerus.
These Neotropical immigrants entered North


America as participants in the Great American
Faunal Interchange following the closure of the
Panamanian Isthmus at about 2.5 Ma. Based
on several well-dated sequences from the
southwestern United States (Galusha et al.,
1984), the association of Nannippus and the
earliest South American immigrants defines a
restricted interval of time in the Late Pliocene
(late Blancan) between 2.5 and 1.9 Ma.

The Caloosahatchee Formation exposed in
the De Soto Shell Pit in De Soto County in
southern Florida has produced an earliest
Irvingtonian (latest Pliocene, late Piacenzian,
1.9-1.6Ma) land mammal fauna (Morgan and
Hulbert, in press). An earliest Irvingtonian age
for the De Soto Shell Pit LF is suggested by the
lack of purely Blancan genera, the absence of
the mammoth Mammuthus, and the presence of
the glyptodont Glyptotherium arizonae, the
coyote-like canid Canis edwardii, the hyaena
Chasmaporthetes ossifragus, the pronghorn
antelope Capromeryx arizonensis, and the
rodents Ondatra idahoensis and Sigmodon
curtisi. The earliest land mammal faunas in
Florida containing Mammuthus, which first
appears in North America near the base of the
Pleistocene at about 1.6 Ma, occur in the
Bermont Formation which overlies the Caloosa-
hatchee Formation in southern Florida. The
Leisey Shell Pit LF of late early Irvingtonian age
(early Pleistocene, early Calabrian, 1.6-1.0 Ma)
is the best known vertebrate fauna from the
Bermont Formation (Hulbert and Morgan, 1989;
Webb et al., 1989).

Although the Neogene terrestrial vertebrate
record in eastern North America is dominated
by Florida sites, Miocene and Pliocene land
mammals do occur elsewhere on the Atlantic
and Gulf Coastal Plains from New Jersey to
Louisiana. The best known eastern Neogene
land mammal faunas exclusive of Florida are the
Hemingfordian Farmingdale Fauna from the
Kirkwood Formation in New Jersey (Tedford
and Hunter, 1984), the late Barstovian
Chesapeake Bay Fauna from the Calvert and
Choptank formations in Maryland (Gazin and
Collins, 1950; Tedford and Hunter, 1984;
Wright and Eshelman, 1987), the late
Hemphillian Lee Creek LF from the Yorktown
Formation in North Carolina (Tedford and
Hunter, 1984; Eshelman and Whitmore, in
press), a Hemingfordian fauna from the Marks

Head Formation at Porters Landing on the
Savannah River in southeastern Georgia (Pratt
and Petkewich, 1989), the early Hemphillian
Mobile (=Mauvilla) LF in Alabama (Isphording
and Lamb, 1971; Tedford and Hunter, 1984),
and a late Hemphillian fauna from the Citronelle
Formation in the Tunica Hills of Louisiana
(Manning and MacFadden, 1989).


Despite Florida's rich Neogene vertebrate
record, there are several time periods during
which land mammals are either unknown or are
represented by small faunas that do not permit
precise biochronologic assessment. Significant
gaps occur during the Late Miocene, including
the late early and late Clarendonian (10.5-9.0
Ma) and the early late Hemphillian (6.7-5.2 Ma),
and much of the Pliocene, comprising the early
and middle Blancan (4.5-2.5 Ma). Furthermore,
very early Miocene (23-19 Ma) marine geologic
units are represented by only a few sparse land
mammal faunas. The Florida Clarendonian
faunal gap corresponds to the very early
Tortonian, while the Hemphillian hiatus
coincides with the Messinian. Both the early
Tortonian and Messinian were characterized by
low sea level (Haq et al., 1987), and apparently
correspond with periods of nondeposition and
erosion on the Florida peninsula. The Florida
middle Pliocene hiatus occurs during a period of
generally high sea level in the southeastern
United States (Dowsett and Cronin, 1990).
Marine vertebrate faunas are known from
Florida during the middle Pliocene, but the
reason for the absence of early and middle
Blancan land mammals is unknown.

An inherent problem with the North
American land mammal biochronology is the
possibility that some faunal differences may be
related to biogeographic, climatic, and
ecological factors. Modern mammal faunas
across the North American continent exhibit a
distinct provincialism, especially among small
mammals. For instance, modern and late
Pleistocene mammal faunas from Florida have
a Neotropical component that is generally
absent elsewhere in the continental United
States. Accurate correlation between Neogene
land mammal faunas from the south-eastern
United States and better known western faunas


is dependent upon the recovery of samples that
are diverse enough to contain widespread age-
diagnostic taxa, in particular carnivores, horses,
and rodents.

Preliminary correlations between Neogene
geologic units in Florida and elsewhere on the
Atlantic and Gulf Coastal Plains based on the
North American land mammal biochronology
have yielded promising results (Tedford and
Hunter, 1984). For example, the upper Bone
Valley Formation in central Florida has a diverse
assemblage of marine, freshwater, and terres-
trial vertebrates of late Hemphillian (earliest
Pliocene) age, but is virtually devoid of marine
microfossils and macroinvertebrates. The lower
Yorktown Formation at the Lee Creek Mine in
North Carolina contains several diagnostic taxa
of late Hemphillian land mammals, as well as
rich samples of marine vertebrates, macro-
invertebrates, and microfossils. The correlation
of these two units based on land mammals
provides a unique opportunity to compare the
land mammal biochronology with biochrono-
logies based on several groups of marine
organisms, including foraminifera, ostracodes,
calcareous nannoplankton, and molluscs.
Furthermore, correlation of predominantly
marine units, such as the Bone Valley and
Yorktown Formations, using the land mammal
biochronology permits comparisons with ter-
restrial geologic units from the interior of the
continent that contain similar land mammal
faunas and have been dated using radioisotopic
methods and/or magnetic polarity stratigraphy.

Stratigraphers and invertebrate paleon-
tologists conducting field work on the Atlantic
and Gulf Coastal Plains of the southeastern
United States would be well advised to collect
vertebrate fossils whenever possible. Neogene
formations on the Coastal Plain are predo-
minantly marine, and therefore sharks, rays,
bony fish, sea turtles, pelagic birds, pinnipeds,
sirenians, and whales are the most commonly
encountered vertebrates. Although there is
currently no formal biochronology for any of
these groups, some taxa of sharks, birds, seals,
and whales do have restricted chronologic
ranges. Diagnostic land mammals can provide
important chronologic data for Neogene
geologic units in this region, as well as allowing
for the possibility of correlation with well-dated
terrestrial geologic units in western North

America. For obvious reasons, terrestrial
vertebrates are generally rare in marine
sediments. Nonetheless, land mammals fre-
quently are encountered in Florida deposits that
clearly represent nearshore marine environ-
ments. The Florida record indicates that land
mammals probably are rather widely distributed
in nearshore marine geologic units throughout
the Gulf and Atlantic Coastal Plains.


I am grateful to Thomas Scott and Victor
Zullo for asking me to participate in the Third
Bald Head Island Conference, and to the
University of North Carolina at Wilmington and
the Florida Geological Survey for providing the
financial support that made the conference
possible. I wish to express my gratitude to the
numerous professional and avocational paleon-
tologists who collected the extensive samples
of Neogene vertebrate fossils from Florida that
form the basis for this review. Particular thanks
are due Rick Carter, Donald Crissinger,
Raymond Dykeman, Steven Emslie, Richard
Hulbert, Dale Jackson, Arthur Poyer, Ann Pratt,
Eric Taylor, John Waldrop, and David Webb.
This is University of Florida Contribution to
Paleontology Number 429.


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van Couvering, J. A., 1985, Cenozoic
geochronology: Geological Society of
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Bryant, J. D., 1991, New early Barstovian
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MacFadden, B. J., and Mueller, P.
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Pliocene: Evidence from the southeastern
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Eshelman, R. E., and Whitmore, F. C., Jr., in
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Gazin, C. L., and Collins, R. L., 1950, Remains
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lithostratigraphic units of the Coastal Plain
of Georgia: The Miocene through
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Pliocene (latest Hemphillian and Blancan) of
Florida: Journal of Vertebrate Paleon-
tology, v. 7, p. 451-468.

1988, Cormohipparion and
Hipparion (Mammalia, Perissodactyla,
Equidae) from the Late Neogene of Florida:
Bulletin of the Florida State Museum,
Biological Sciences, v. 33, no. 5, p. 229-

and MacFadden, B. J., 1991,
Morphological transformation and
cladogenesis at the base of the adaptive
radiation of Miocene hypsodont horses:
American Museum Novitates, no. 3000, p.

and Morgan, G. S., 1989,
Stratigraphy, paleoecology, and vertebrate
fauna of the Leisey Shell Pit Local Fauna,
early Pleistocene (Irvingtonian) of
southwestern Florida: Papers in Florida
Paleontology, no. 2, p. 1-20.

Isphording, W. C., and Lamb, G. M., 1971, Age
and origin of the Citronelle Formation in
Alabama: Geological Society of America
Bulletin, v. 82, p. 775-780.

Jones, D. S., MacFadden, B. J., Webb, S. D.,
Mueller, P. A., Hodell, D. A., and Cronin,
T. M., 1991, Integrated geochronology of
a classic Pliocene fossil site in Florida:
linking marine and terrestrial
biochronologies: Journal of Geology, v.
99, p. 637-648.

Lundelius, E. L., Jr., Churcher, C. S., Downs,
T., Harington, C. R., Lindsay, E. H.,
Schultz, G. E., Semken, H. A., Webb, S.
D., and Zakrzewski, R. J., 1987, The North
American Quaternary sequence: in
Woodburne, M. O., ed., Cenozoic
mammals of North America: Geochrono-
logy and biostratigraphy: Berkeley,
California, University of California Press, p.

MacFadden, B. J., 1980, An early Miocene land
mammal (Oreodonta) from a marine lime-
stone in northern Florida: Journal of
Paleontology, v. 54, p. 93-101.

1986, Late Hemphillian
monodactyl horses (Mammalia, Equidae)
from the Bone Valley Formation of central
Florida: Journal of Paleontology, v. 60, p.

Bryant, J. D, and Mueller, P.
A., 1991, Sr-isotopic, paleomagnetic, and
bio-stratigraphic calibration of horse
evolution: Evidence from the Miocene of
Florida: Geology, v. 19, p. 242-245.


and Webb, S. D., 1982, The
succession of Miocene (Arikareean through
Hemphillian) terrestrial mammalian localities
and faunas in Florida: in Scott, T. M., and
Upchurch, S. B., eds., Miocene of the
southeastern United States: Florida Bureau
of Geology Special Publication 25, p. 186-

Manning, E. M., and MacFadden, B. J., 1989,
Pliocene three-toed horses from Louisiana,
with comments on the Citronelle
Formation: Tulane Studies in Geology and
Paleontology, v. 22, no. 2, p. 35-46.

Morgan, G. S., 1989, Miocene vertebrate
faunas from the Suwannee River Basin of
North Florida and South Georgia: in
Morgan, G. S., ed., Miocene paleontology
and stratigraphy of the Suwannee River
Basin of North Florida and South Georgia:
Southeastern Geological Society,
Guidebook 30, p. 26-53.

and Hulbert, R. C., Jr., in press,
Overview of the geology and vertebrate
biochronology of the Leisey Shell Pit Local
Fauna, Hillsborough County, Florida.
Bulletin of the Florida Museum of Natural
History, Biological Sciences.

and Pratt, A. E., 1988, An early
Miocene (late Hemingfordian) vertebrate
fauna from Brooks Sink, Bradford County,
Florida: Southeastern Geological Society,
Guidebook Number 29, p. 53-69.

and Ridgway, R. B., 1987, Late
Pliocene (late Blancan) vertebrates from the
St. Petersburg Times Site, Pinellas County,
Florida, with a brief review of Florida
Blancan faunas: Papers in Florida
Paleontology, no. 1, p. 1-22.

Olsen, S. J., 1963, An upper Miocene fossil
locality in north Florida: Quarterly Journal
of the Florida Academy of Sciences, v. 24,
p. 308-314.

Pratt, A. E., and Petkewich, R. M., 1989, Fossil
vertebrates from the Marks Head Formation
(lower Miocene) of southeastern Georgia:
Journal of Vertebrate Paleontology, v. 9
(suppl. to n. 3), p. 35A (abstract).

Scott, T. M., 1988, Lithostratigraphy of the
Hawthorn Group (Miocene) of Florida:
Florida Geological Survey Bulletin 59, 148

Tedford, R. H., Galusha, T., Skinner, M. F.,
Taylor, B. E., Fields, R. W., Macdonald, J.
R., Rensberger, J. M., Webb, S. D., and
Whistler, D. P., 1987, Faunal succession
and biochronology of the Arikareean
through Hemphillian interval (late Oligocene
through earliest Pliocene Epochs) in North
America, in Woodburne, M. O., ed., Ceno-
zoic mammals of North America: Geochro-
nology and biostratigraphy: Berkeley,
California, University of California Press, p.

and Hunter, M. E., 1984,
Miocene marine-nonmarine correlations,
Atlantic and Gulf Coastal Plains, North
America: Palaeogeography, Palaeocli-
matology, Palaeoecology, v. 47, p. 129-

Voorhies, M. R., 1974, Late Miocene terrestrial
mammals, Echols County, Georgia:
Southeastern Geology, v. 15, p. 223-235.

Webb, S. D., Baskin, J. A., and MacFadden, B.
J., 1981, Geology and paleontology of the
Love Bone Bed from the late Miocene of
Florida: American Journal of Science, v.
281, p. 513-544.

and Crissinger, D. B., 1983,
Stratigraphy and vertebrate paleontology of
the central and southern phosphate
districts of Florida, in Central Florida
Phosphate District: Field Trip Guidebook,
Geological Society of America, South-
eastern section, p. 28-72.

and Hulbert, R. C., Jr., 1986,
Systematics and evolution of Pseudhip-
parion (Mammalia, Equidae) from the late
Neogene of the Gulf Coastal Plain and the
Great Plains: Contributions to Geology,
University of Wyoming, Special Paper 3, p.


Morgan, G. S., Hulbert, R. C., Jr.,
Jones, D. S., MacFadden, B. J., and
Mueller, P. A., 1989, Geochronology of a
rich early Pleistocene vertebrate fauna,
Leisey Shell Pit, Tampa Bay, Florida:
Quaternary Research, v. 32, p. 1-15.

and Tessman, N., 1968, A
Pliocene vertebrate fauna from low
elevation in Manatee County, Florida:
American Journal of Science, v. 266, p.

Woodburne, M. 0., 1987, A prospectus of the
North American Mammal Ages: in
Woodburne, M. O., ed., Cenozoic
mammals of North America: Geochro-
nology and biostratigraphy: Berkeley,
California, University of California Press, p.

Wright, D. B., and Eshelman, R. E., 1987,
Miocene Tayassuidae (Mammalia) from the
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Coast and their bearing on marine-
nonmarine correlation: Journal of
Paleontology, v. 61, p. 604-618.



Paleontological Research Institution, 1259 Trumansburg Road, Ithaca, NY 14850


It is a well-known but little acknowledged
generality about scientists (and probably others)
that each believes that the problem or area of
their own research is of greater than average
importance. Even while a scientist may have
first been drawn to a topic by its peculiarity,
beauty, or by simple personal curiosity, what
we think of as "good science" is that it
illuminates some more general principle, that it
can help solve some larger problem. For any
given research question, however, there is no
guarantee, however, that this will be the case.
Each of us is therefore compelled at some point
to think about what (if any) the general utility
of our research is. This is a healthy thing to do
on general intellectual grounds, but it is made
even more pressing in a world of limited and
very competitive funding opportunities.

The Plio-Pleistocene shell beds of the
southern half of the Florida peninsula are well-
known for their abundant, diverse and well
preserved fossils, especially mollusks. If one is
interested in mollusks for their own sake, either
scientifically or aesthetically, these beds are
among the most spectacular and fascinating of
sights. Furthermore, as is the case for other
dense and diverse fossil deposits, the very
character of these beds begs the question of
their environment and mode of formation; we
simply want to know where such extraordinary
geological phenomena came from. There are
thus valid and "interesting" reasons to study
these beds.

The question I wish to address here,
however, is: do these deposits have the
potential to inform us about any more general
topic, or to contribute to the solution of any
more general problem? Put simply, why should
anyone not particularly interested in Neogene
mollusks or dense shell beds care about these

My answer to this question is two-fold: 1)
because changes in biological productivity
appears to have played a significant role in the
formation of these beds, and because marine
biological productivity is often tied to other
oceanographic environmental parameters, such
as temperature, investigation of the role of
productivity in shell bed formation may
illuminate reconstruction of other paleoenvi-
ronmental variables; 2) these variables may be
especially important because Florida occupied
a biologically and oceanographically important
position during the dramatic climatic changes
that occurred during the Plio-Pleistocene.


In seeking the origin of any dense fossil
accumulation ("shell bed"), we may divide the
search for causal factors into the search for
biological, physical or sedimentological, and
diagenetic factors (Kidwell et al., 1986). An
additional set of factors that falls between (i.e.,
includes both) biological and physical includes
those environmental processes and conditions
that affect rate of production of biogenic
hardparts by affecting biological productivity
(sensu Odum, 1971, p. 43), such as nutrient
supply, temperature, light, pH, etc.

Because taphonomic and paleoenviron-
mental analyses frequently illuminate each
other, investigations into shell bed origin usually
require independent paleoenvironmental
reconstructions; without such knowledge it is
difficult to judge which of these several
taphonomic processes are most important.
Shallow marine environments, for example, are
typically more subject to physical reworking by
storms. Similarly, paleoenvironments are
sometimes reconstructed in part from
taphonomic data or conclusions. Taphonomic
evidence for abundant reworking or transport,
for example, might support an interpretation of
active currents.




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In the case of the Plio-Pleistocene shell
beds of southern Florida, adequate independent
interpretations of potentially relevant paleoenvi-
ronmental variables (e.g., depth, temperature,
current energy, productivity) that might be
applied as checks of taphonomic interpretations
have been largely lacking. Since we do not, for
example, have independent indications about
the depths in which the shell beds were depo-
sited, it is difficult to determine whether
observed high bioclastic densities were more
likely a result of physical accumulation (by
storms or currents) or of high organismal
abundance (perhaps caused by high nutrient
levels). Neither do we know whether evidence
for lower-than-modern water temperatures
indicates cooler climates, deeper water, or
upwelling of cool, high-nutrient water into
shallow depths, which could promote greater
biological productivity. The latter conclusion
might, in turn, be consistent with an important
role for high biological productivity in
generating shell beds, and thus a potentially
lesser role for physical/sedimentological
mechanisms of allochthonous or parauto-
chthonous hardpart accumulation.

A complex set of interactions thus exists
among the variables we can determine and
those we wish to know (Figure 1). The
observation that molluscan diversity and
abundance seem to show disconnected his-
tories in the Florida Plio-Pleistocene allows
construction of a simple model of shell bed
formation. To the degree that diversity and
abundance may both be controlled by both
biological and physical factors in the
environment, two extremes can be considered:
1) On one extreme, diversity is due primarily to
high biological productivity (associated with
high nutrient levels); abundance is not strongly
affected by levels of productivity (or nutrients)
and is due principally to physical accumulation
by sedimentological processes of time- and
habitat-averaging. 2) On the other extreme,
abundance is due primarily to high biological
productivity (associated with high nutrient
levels); diversity is not strongly affected by
productivity, and is altered principally in
response to changes in temperature. Evidence
for significant physical reworking and time-
and/or habitat-averaging may be seen as
circumstantial evidence for an important role for
productivity in affecting diversity (possibility 1,

above). Evidence for changes in nutrient status
coincident with diversity changes would also
support this scenario. Evidence for temperature
change coincident with diversity changes
would, on the other hand, be circumstantial
evidence for a role for nutrient levels in
affecting abundance.

As is commonly the case (e.g., Allmon,
1992a), a key to successful paleoecology lies in
breaking into these catch-22s, often by
obtaining information from a previously unex-
ploited source. Herein may lie a potentially
fruitful field of interaction between taphonomy
and paleoenvironmental reconstruction.


Productivity may affect not only abundance
but also diversity (Allmon, 1992a, b and refe-
rences therein; Rosenzweig and Abramsky, in
press). This potentially dual effect may be of
substantial importance for analysis of the role
of productivity in formation of these shell beds.
Lithologically, the shelly sands that comprise a
large proportion of the Plio-Pleistocene
stratigraphic column are very similar; that is,
shells are equally abundant. Alpha-diversities
of gastropods within individual faunal units,
however, appear to have declined since the
Late Pliocene, although regional mollusk
diversities appear to have been uniformly high
(Table 1); there have, in addition, been several
episodes of substantial faunal turnover
characterized by increased rates of speciation
and extinction (Allmon et al., in press).

These changes are of particular interest
because of their timing and geography. The
Plio-Pleistocene of southern Florida contains
diverse faunas that lived at a time of crucial
change in world climates (Cronin, 1991;
Dowsett and Poore, 1991), and at relatively
low latitudes, where biological activity should
have been high. Late Pliocene faunas lived and
died during the final closure of the Central
American Isthmus and the changes in oceanic
circulation that accompanied this event
(Allmon, 1992a and references therein). These
faunas would thus appear to be positioned in
time and space in a way that can allow for
examination of the effects of profound
environmental change on a thriving biota.


Table 1. Number of gastropod species recorded from the three principal Plio-Pleistocene shell bed units
in southern Florida and Recent habitats < 100 m depth on the coast of Florida (from Allmon et al., in

Age/"Formation" Species richness
Local Total

Recent 42-1811 5452
Pleistocene/Bermont 2613 304
Caloosahatchee 425 495
Pliocene/Pinecrest 3335 500

1 -- Alpha-diversities of gastropods based on data in Hopkins et al. (1977) [Florida Middle Grounds,
northeastern Gulf of Mexico, 42 species], Reed and Mikkelsen (1987) [coral reefs, east coast of Florida,
155 species], Lyons (1989) [Hutchinson Island, east coast of Florida, 181 species].

2 --total recorded species on the west coast of Florida based on Recent database compiled by
G.Rosenberg (Allmon et al., in press).

3 -- Belle Glade quarry, Palm Beach County, Florida (Hoerle, 1970)

4 -- Leisey shell pit, Hillsborough County, Florida (Allmon et a., in press)

5 -- APAC quarry, Sarasota County, Florida (Allmon et a., in press)

Table 2. Summary of available information on the age, environment and mode of formation of the
upper Pliocene "Pinecrest Sand", based largely on studies in quarries near Sarasota, Florida (see Allmon,
1993 for details).

Age 3.0-3.5 Ma (units 10-5 of Petuch, 1982)
2.0-2.5 Ma (units 4-2 of Petuch, 1982)
depth variable from 30-50 m to 1-2 m
temperature at least 2-3 OC cooler than at present
current variable; storms occasionally important;
energy not significantly different from present
productivity generally higher than at present in this
area, probably due largely to upwelling
Taphonomic signature
fabric densely packed, poorly sorted
(sensu Kidwell and Holland, 1991)
surface mixed; pristine and worn/encrusted found
condition together (e.g., Geary and Allmon, 1990)
ostracodes density higher inside articulated bivalves
(Kamiya and Allmon, 1990, in prep.)
sediments fining and coarsening upward sequences;
finer inside bivalves (Nocita and Allmon,
1991, in prep.)


Integrating these perspectives and carrying
out such studies will require a great deal more
information about these faunas than we have at
present, including especially basic systematics,
taphonomy and paleoenvironmental reconstruc-
tion. Information currently available on the age,
taphonomic signature and environment of one
of the most important of southern Florida's
fossil shell beds, the "Pinecrest Sand" is
summarized in Table 2 (see Allmon, 1993 for
details). This information indicates that the
Pinecrest shell beds formed as a result of both
physical accumulation and high biological
productivity. There is strong evidence for both
phenomena, and neither can be excluded as
having played a major role. It remains to be
determined which process was dominant and at
what times during the deposition of the beds.
This will require more detailed bed-by-bed
taphonomic and paleoenvironmental analysis;
this work is currently underway. The
maintenance of high abundance and diversity
throughout much of the Florida Plio-Pleistocene,
punctuated by episodes of faunal turnover, is
consistent with a scenario of intermittent
disruption of otherwise relatively high-
productivity conditions.

In order to judge the relative role of
biological productivity on mollusk abundance
and diversity, comparable data for
faunal/stratigraphic units above the Pinecrest
are needed. If subsequent paleoenvironmental
analysis of, for example, the overlying
Caloosahatchee shell beds yields little or no
indication of high nutrient levels, and
taphonomic analysis of the same beds shows
similar or higher degrees of physically-mediated
accumulation and time-averaging, then a
change in nutrient levels may be implicated in
the high rates of extinction and speciation
between the Pinecrest and the Caloosahatchee
(Allmon, 1992a; Allmon etal., in press). If, on
the other hand, there is also evidence for high
nutrient levels in at least some Calooshatchee
beds, then some other process, such as tempe-
rature change, may have been more important
in this and other turnover episodes.


The Plio-Pleistocene shell beds of southern
Florida could have formed under a regime of
productivity not much different from that which
exists off the coast of Florida today, solely by
the action of some combination of physical
sedimentological processes. But I doubt it.
There is evidence that temperature and produc-
tivity conditions, at least in the Late Pliocene,
were substantially different from those that
occur today. It could be the case that changes
in productivity were important in the formation
of these beds, but that this has little signi-
ficance beyond Florida. The role of biological
productivity in shell bed formation has not been
emphasized, however, and Florida may be a
place to explore this problem in general terms.
More importantly, productivity changes, of the
type that may have affected shell bed forma-
tion, appear to have been at least partly
responsible for at least some of the faunal
changes (especially extinction and origination)
that occurred in Florida during this time. Florida
was then, as it still is, located at the juncture
between temperate and tropical realms. The
biological changes that occurred in southern
Florida during the Plio-Pleistocene may tell us
something about changes in other places, at
other times.


Almon, W. D., 1992a, Role of temperature and
nutrients in extinction of turritelline
gastropods, Cenozoic of the northwestern
Atlantic and northeastern Pacific: Palaeo-
geography, Palaeoclimatology, Palaeoeco-
logy, v.92, p. 41-54.

1992b, A causal analysis of
stages in allopatric speciation: Oxford
Surveys in Evolutionary Biology, v. 8, p.

1993, Age, environment and
mode of deposition of the densely fossili-
ferous Pinecrest Sand (Pliocene of Florida):
implications for the role of biological
productivity in shell bed formation:
Palaios, v. 8, no. 2, p. 183-201.


Rosenberg, G., Portell, R. and
Schindler, K., in press, Diversity of
Pliocene-Recent mollusks in the Western
Atlantic: extinction, origination and
environmental change: in Jackson, J.B.C.,
Coates, A. G. and Budd, A. F., eds.,
Evolution and environment in tropical
America over the last ten million years:
University of Chicago Press, Chicago.

Cronin, T. M., 1991, Pliocene shallow water
paleoceanography of the North Atlantic
ocean based on marine ostracodes:
Quaternary Science Reviews, v. 10, p.

Dowsett, H. J. and Poore, R. Z., 1991, Pliocene
sea surface temperatures of the North
Atlantic Ocean at 3.0 Ma: Quaternary
Science Reviews, v. 10, p. 189-204.

Geary, D. H., and Allmon, W. D., 1990,
Biological and physical contributions to the
accumulation of strombid gastropods in a
Pliocene shell bed: Palaios, v.5, p.259-

Hoerle, S. E., 1970, Mollusca of the "Glades"
unit of southern Florida: Part II; list of
molluscan species of the Belle Glade Rock
pit, Palm Beach County, Florida: Tulane
Studies in Geology and Paleontology,
v.8(2), p.56-68.

Hopkins, T. S., Blizzard, D. R., and Gilbert, D.
K., 1977, The molluscan fauna of the
Florida Middle Grounds with comments on
its zoogeographical affinities: Northeast
Gulf Science, v. 1, no. 1, p. 39-47.

Kamiya, T., and Allmon, W. D., 1990,
Ostracode morphology and populations
structure: taphonomic and environmental
indicators in the Pliocene of Florida:
Geological Society of America, Abstracts
with Programs, v.22, no. 7, p. A82.

Kidwell, S. M., Fursich, F. T. and Aigner, T.,
1986, Conceptual framework for the
analysis and classification of fossil
concentrations: Palaios, v.1, p.228-238.

and Holland, S. M., 1991, Field
description of coarse bioclastic fabrics:
Palaios, v.6, no. 4, p.426-434.

Lyons, W. G., 1989, Nearshore marine ecology
at Hutchinson Island, Florida: 1971-1974,
XI. Mollusks: Florida Marine Research
Publications, no. 47, 131 p.

Nocita, B. W., and Allmon, W. D., 1991,
Sedimentological parameters as paleoenvi-
ronmental and taphonomic indicators in a
Pliocene shell bed: Geological Society of
America, Southeastern Section, Abstracts
with Programs, v. 23, p. 109.

Odum, E. P., 1971, Fundamentals of ecology.
3rd ed., W.B.Saunders Company,
Philadelphia, 574 p.

Petuch, E. J., 1982, Notes on the molluscan
paleoecology of the Pinecrest Beds at
Sarasota, Florida with the description of
Pyruella, a stratigraphically important new
genus (Gastropoda: Melongenidae):
Proceedings of the Academy of Natural
Sciences of Philadelphia, v. 134, p.12-30.

Reed, J. K. and Mikkelsen, P. M., 1987, The
molluscan community associated with the
scleractinian coral Oculina varicosa:
Bulletin of Marine Science, v. 40, p. 99-

Rosenzweig, M. L. and Abramsky, Z., in press,
How are diversity and productivity
related?: in Ricklefs, R. and Schluter, D.,
eds., Historical and geographical
determinants of community diversity:
University of Chicago Press.



Department of Geology, Florida Atlantic University
Boca Raton, Florida 33431


At present, the stratigraphic nomenclatural
scheme for southern Florida is in a chaotic and
unstandardized form. Such classic and well-
known geological names as the "Caloosa-
hatchee Formation", "Fort Thompson Forma-
tion", "Bermont Formation", and others, were
all based upon faunal differences and are, in
reality, biozones and not described lithostra-
tigraphic units. Facies shifts of these
"formations" across the state, particularly if
unfossiliferous, make correlations difficult if not
impossible. To exacerbate matters, the surficial
formations (0 50 m depth) of southern Florida
all exhibit convergent lithologies, with facies
shifts often occurring in only a few meters
distance. Because of this diachronous con-
vergence pattern, widely-separated strati-
graphic columns, particularly those derived from
wells, often have few, if any, correlative

While undertaking a long-term study of
Neogene molluscan extinction patterns on the
Floridan peninsula, I uncovered a biostrati-
graphic methodology that may be useful for
local correlations, regardless of similarities in
lithologies. In this study, eight superfamilies of
ecologically-dominant macrocaenogastropods
(the Cerithioidea, Cypraeoidea, Tonnoidea,
Muricoidea, Buccinoidea, Volutoidea,
Cancellariodea, and Conoidea, altogether
comprising 37 families and 208 genera and
listed here in Appendix 1) were used to
investigate the frequency of episodes of
extinction within the late Neogene fossil beds
of the Everglades Basin and adjacent areas.
Based upon the combined percentages of
extinction and regional extinction, four
extinction events were found within the Late
Pliocene-Pleistocene sequence, and these
separate five discrete molluscan faunas. The
faunal fluctuations resulted in a pattern that
mirrors the traditional stratigraphic nomen-

clatural sequence of "formations". These
faunas and the intercollated extinction events,
demarcate sharply-defined chronological hori-
zons which appear to be constant across the
state. The disappearance, not the presence,
then, of certain key taxa within faunas may
prove to be a powerful, pragmatic tool for
accurately determining the relative age of any
fossiliferous unit, regardless of facies


As an artifact of chronoendemism at the
generic level, four main types of molluscan
faunas can be differentiated for the late
Neogene of the Okeechobean Sea region (see
Petuch, 1990; 1992). These are shown, along
with the traditional "formational" nomenclature,
in Figure 1.

1. Kissimmean Faunas (named for the
Kissimmee River) containing key index genera
such as the muricids Acantholabia (Figure 34),
Trossulasalpinx, Pterorhytis, and Vitularia
(Figures 17, 18), the ecphorine thaidid
Latecphora (Figure 5), the cypraeid
Siphocypraea (Figures 30, 31), the buccinids
Calophos (Figure 6), Cymatophos (Figure 23),
Hesperisternia (Figure 7), and Celatoconus
(Figure 9), the melongenids Pyruella (Figure
37), Echinofulgur, and Tropochasca (Figure 8),
the marginellids Bullata and Microspira, the
turbinellid Hystrivasum (Figure 35), and the
conid Contraconus (Figures 28, 29).

2. Bellegladean Faunas (named for Belle
Glade, Palm Beach County) containing key
index genera such as the melongenid
Miccosukea (Figures 39, 40, 45), and the now-
relictual genera Cerithioclava (Cerithiidae)
(Figure 53), Jenneria (Ovulidae) (Figures 60,
61), Malea (Tonnidae) (Figures 51,51),
Vokesinotus (Muricidae)(Figure 46), and
Eurypyrene (Columbellidae)(Figures 49,50).










Everglades Peat

Lake Flirt Marl

Pamlico Sand

Ft. Thompson Fm. Key Largo Fm. Miami Fm.

Bermont Fm.

Holey Land Unit

Caloosahatchee Fm.

Pinecrest Beds

Sarasota Unit

Buckingham Fm.

Tamiami Fm.




Figure 1. Diagram showing the relationship of the molluscan faunas of the Okeechobean Sea with the
traditional stratigraphic nomenclature of southern Florida. Roman numerals designate faunistic dynasties,
showing their chronological placement.


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f j




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Figures 2-11. Characteristic Kissimmean gastropod genera that became extinct at the end of Dynasty I.
2. Ecphora s.s. (E. guadricostata (Say, 1824), length 53 mm); 3. Leptarius (L. metae Petuch, 1991,
length 18 mm); 4. Ecphora s.s. (E. floridana Petuch, 1989, length 92 mm); 5. Ecphora (Latecphora) (E.
bradleyae Petuch, 1987, length 66 mm); 6. Calophos (C. wilsoni Allmon, 1990, length 64 mm); 7.
Hesperisternia (H. filicata (Conrad, 1843), length 27 mm); 8. Tropochasca (T. petiti Olson, 1967, length
68 mm); 9. Celatoconus (C. nux (Dall, 1890), length 18 mm); 10. Rhipophos (R. metajonesae Petuch,
1991, length 19 mm); 11. Mansfieldella (M. gladeensis (Mansfield, 1931), length 19 mm).



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i O








Figures 12 27. Characteristic Kissimmean gastropod genera that became regionally extinct at the end
of Dynasty I. 12. Extractrix (E. hoerlei Olsson, 1967), length 23 mm); 13,14. Pusula (P. miamiensis
Petuch, 1991, length 12 mm); 15,16. Panamurex (P. clarksvillensis (Mansfield, 1937), length 19 mm);
17,18. Vitularia (V. linguabison E. Vokes, 1967, length 49 mm); 19. Conus (Virgiconus) (C. miamiensis
Petuch, 1986, length 32 mm); 20. Nodicostellaria (N. jonesae Petuch, 1991, length 9 mm); 21,22
Decoriatrivia (D. miccosukee Petuch, 1991, length 19 mm); 23. Cymatophos (C. lindae Petuch, 1991,
length 50 mm); 24,25. Parametaria (P. hertweckorum Petuch, 1991, length 20 mm); 26,27. Parametaria
(P. lindae Petuch, 1986, length 22 mm).












17 \


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\-J 35


Figures 28 38. Characteristic Kissimmean gastropod genera that became extinct or regionally extinct
at the end of the Dynasty II. 28. Contraconus (C. tryoni Heilprin, 1886, length 158 mm); 29. Contraconus
(C. osceolai Petuch, 1991, length 89 mm); 3031. Siphocypraea (S. problematic Heilprin, 1886, length
51 mm); 32. Pleioptygma (P. lineolata (Heilprin, 1886), length 80 mm); 33. Terebraspira (T. scalarina
(Heilprin, 1886), length 168 mm); 34. Acantholabia (A. floridana Olsson and Harbison, 1953, length 24
mm); 35. Hystrivasum (H. cf. horridum (Heilprin, 1886), length 85 mm); 36. Solenosteira (S. mengeana
(Dall, 1890), length 20 mm); 37. Pyruella (P. eismonti Petuch, 1991, length 83 mm); 38. Conus
(Ximeniconus) (C. waccamawensis Smith, 1930, length 30 mm).







/ i




48 50

Figures 39 50. Characteristic Bellegladean gastropod genera and species complexes that became
extinct at the end of Dynasty II. 39. Lindoliva (L. spengleri Petuch, 1988, length 110 mm); 40. Lindoliva
(L. spengleri Petuch, 1988, length 103 mm); 41. Conus (un-named subgenus) (C. evergladesensis
Petuch, 1991, length 28 mm); 42. Conus (un-named subgenus) (C. evergladesensis Petuch, 1991, length
30 mm); 43. Miccosukae (M. cynthiae (Petuch, 1990), length 46 mm); 44. Miccosukea (M. holeylandica
(Petuch, 1990), length 35 mm); 45. Lindoliva (L. diegelae Petuch, 1988, length 51 mm); 46. Vokesinotus
(V. griffin Petuch, 1991, length 33 mm); 47. Miccosukea (M. cynthiae (Petuch, 1990), length 57 mm); 48.
Miccosukea (M. holeylandica (Petuch, 1990), length 40 mm); 450. Eurypyrene (E. miccosukee Petuch,
1991, length 20 mm).





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Figures 51 61. Characteristic Bellegladean gastropod genera and species complexes that became
regionally extinct at the end of Dynasty III. 51. Malea (M. petiti Petuch, 1989, length 10 mm); 52. Malea
(M. spring Petuch, 1989, length 172 mm; from the Kissimmean Caloosahatchee Formation, but illustrated
here to show characteristic apertural morphology (missing on M. petiti)); 53. Cerithioclava (C. garciai
Houbrick, 1986, length 71 mm); 54,55. Conus (Magelliconus) (C. griffini Petuch, 1990, length 18 mm);
56. Melongena (Rexmela) (bispinosa species complex) (M. bispinosa (Philippi, 1844), length 40 mm);
57,58,59. Cypraea (Pseudozonaria) (C. portelli Petuch, 1990, length 25 mm); 6061. Jenneria (J.
loxahatchiensis M. Smith, 1936, length 28 mm).







Y- |

S70 64


68 69


70 71

Figures 62 71. Characteristic Bellegladean (Lake Okeelanta) and Lakeworthian gastropod genera that
became extinct or regionally extinct at the ends of Dynasties III and IV. 62. Turbinella (T. hoerlei E.
Vokes, 1996, length 93 mm); 63. Pyrazisinus (P. roseae Petuch, 1991 subspecies Ft. Thompson
Formation length 55 mm); 64. Strioterebrum (S. vinosum (Dall, 1890), length 19 mm); 65-71. Examples
of Lake Okeelanta Seminolina radiation; 65. S. new species, length 24 mm; 66. S. roseae Petuch, 1991,
length 9 mm; 6768. S. lindae Petuch, 1991, length 27 mm; 69. S. knepperi Petuch, 1991, length 12 mm;
70. S. clewistonense (Baker, 1940), length 26 mm; 71. S. wilsoni (Taylor, 1966), length 24 mm.


3. Lakeworthian Faunas (named for Lake
Worth, Palm Beach County) essentially a
modern fauna with some relictual genera such
as Pyrazisinuis (Potamididae) (Figure 63),
Melongena s.s. (Melongenidae), and Turbinella
(Turbinellidae) (Figure 62).

4. Recent Fauna of Coastal Southern
Florida used as a reference standard and basis
for comparison with the paleofaunas.


Each faunal category, in turn, contained
separate discrete subsets in chronoendemics
that are here referred to as "dynasties". The
Kissimmean Faunas encompassed Dynasty I
(with 195 genera in total) and Dynasty II (with
137 genera in total), which contain faunas that
correlate with those found in what have been
called the "Pinecrest Beds" and "Caloosa-
hatchee Formation", respectively.

The Bellegladean Faunas encompassed
Dynasty III (with 117 genera in total), which
contains faunas that correlate with those of the
"Holey Land Unit" (Petuch, 1990) and "Ber-
mont Formation". The Lakeworthian Faunas
take into account Dynasty IV (with 61 genera
in total), which correlates with the faunas of
the "Fort Thompson", "Coffee Mill Hammock"
(Member?), "Miami", and "Key Largo" "forma-
tions". Dynasty V (with 129 general in total)
refers to the Holocene and sub-Recent marine
fauna of coastal southern Florida. Each
dynasty represents a separate series of
speciation events that demarcates a fixed
geochronological horizon within the regional
lithostratigraphic sequence.


All dynasties are separated by extinction
events of varying intensities. The most severe
collapse events took place during the time of
the Kissimmean Faunas with the extinction
between Dynasties I and II (late Piacenzian
Pliocene) resulting in an 18% generic loss, and
Dynasties II and III (early Pleistocene, probably
"Nebraskan Stage") resulting in a 23% generic
loss. The Bellegladean Faunas with several
new endemic radiations, were terminated by
the extinction between Dynasties III and IV
(middle-late Pleistocene, probably "Illinoisan

Stage") which resulted in a 7% generic loss.

Lakeworthian Faunas, although even more
depauperated than the Bellegladean types,
contained the most cold-tolerant and
eurythermal genera by virtue of survivorship
from previous cooling-induced extinction
events. As a result, only 5% of the genera
disappeared during the extinction event
between Dynasties IV and V ("Wisconsin
Stage" Pleistocene). Faunal lists for these
analyses were compiled from Olsson and
Harbison, 1953; Olsson and Petit, 1964;
Olsson, 1967; Petuch, 1988, 1989, 1990, and

Although not belonging to a marine fauna,
another important geoghronological marker is
the fresh water Seminolina (Planorbidae)
radiation of Pleistocene Lake Okeelanta (some
examples shown here in Figures 65-71; see
Petuch, 1988, 1992). This large freshwater
lake occupied the Everglades Basin during a
major early-to-middle Pleistocene sea level drop
("Kansan Stage"?), and its sediments are
stratigraphically intercollated between two thick
marine beds of the "Bermont Formation". The
thick bed of Okeelantan fresh water marl, along
with its unique gastropod fauna (particularly
unique, bizarre index species such as
Seminolina lindae Petuch, 1991; Figures 67,
68) may prove to be useful in trans-Everglades
correlations. The Okeelantan Seminolina
radiation should be included within the
collection of faunas that comprises Dynasty III.


Several interesting anomalies that relate to
extinction patterns were also uncovered during
these analyses. Among these are:

1. The basal unit of the "Pinecrest Beds",
Petuch Unit 11 ("Sarasota Member" of Petuch,
1989) (Dynasty I), recently dated as early
Piacenzian, was found to contain a relictual,
older late Zanclian-type fauna.

2. The upper part of the "Caloosahatchee"
fauna (Dynasty II), recently dated as earliest
Pleistocene, contains a relict Pliocene fauna
that has survived only within the enclosed
Okeechobean Sea of the Everglades Basin.
Contemporaneous faunas in central and


northern Florida ("Nashua Formation") lack 1992, The Edge of the Fossil Sea:
almost all key Kissimmean genera. The Baily-Matthews Shell Museum,
Sanibel, Fla., 148 p.
3. The land-locked Okeechobean Sea
acted as an isolated speciation center,
producing, often rapidly, unique and
geographically-restricted taxa such as the
Kissimmean Echinofulgur, Tropochasca,
Liochlamys, and Acantholabia, and the
Bellegladean Miccosukea and Lindoliva.


I thank Mrs. Cynthia Mischler, Department
of Geology, FAU, for patiently typing the
manuscript and Ms. Cindy Collier, Florida
Geological Survey for entering the manuscript
into WordPerfect.


Olsson, A.A., 1967, Some Tertiary Mollusks
from South Florida and the Caribbean.
Paleontological Research Institute, Ithaca,
N.Y., 161 p.

Olsson, A. A., and Harbison, A., 1953,
Pliocene Mollusca of southern Florida.
Monographs of the Academy of Natural
Science of Philadelphia, 361 p.

Olsson, A. A., and Petit, R. E., 1964, Some
Neogene Mollusca from Florida and the
Carolinas: Bulletins of American
Paleontology, v. 47, no. 217, p. 556-561.

Petuch, E. J., 1988, Neogene History of
Tropical American Mollusks: Biogeography
and Evolutionary Patterns of Tropical
western Atlantic Mollusca: The Coastal
Education and Research Foundation,
Charlottesville, VA, 217 p.

1989, Field Guide to the
Ecphoras: The Coastal Education and
Research Foundation, Charlottesville, VA,
140 p.

1990, New Gastropods from the
Bermont Formation (Middle Pleistocene) of
the Everglades Basin. The Nautilus, v.
104, no. 3, p. 96-104.



Southern Floridan Neogene Gastropod Genera (Arranged By Superfamily, Family and Subfamily) Analyzed
For Patterns of Extinction. E=Extinct; R=Regionally Extinct; P=Paciphilic.

Cerithioclava (R) (Figure 53)
Clypeamoris (P)
Ochetoclava (P)
Cerithidea s.s.
Cerithidea (new subgenus c. xenos
complex) (E)
Pyrazisinus (E) (Figure 63)
Apicula (E)
Bactrospira (E)
Eichwaldiella (E)
Petaloconchus (E)
Pseudozonaria (P) (Figures 57,58,59)
Siphocypraea (R) (Figures 30, 31)
Ovulidae Ovulinae
Ovulidae Eocypraeinae
Jenneria (P) (Figures 60, 61)
Decoriatrivia (P) (Figures 21, 22)
Pusula (P) (Figures 13, 14)
Trivia s.s.

Cymatium s.s.
Malea s.s. (P) (Figures 51. 52)
Muricidae Muricinae
Acantholabia (E) (Figure 34)
Murex ("Haustellum" of E. Vokes)
Panamurex (R) (Figures 15, 16)
Muricidae Ocenebrinae
Neurarhytis (P)
Pterorhytis s.s. (E)
Trossulasalpinx (E)
Vokesinotus (E) Figure 46)
Muricidae Muricopsinae
Pygmaepterys (R)


Subpterynotus (R)
Vitularia (P) (Figures 17, 18)
Muricidae Typhinae
Thaididae Thaidinae
Ecphora s.s. (E) (Figures 2, 4)
Latecphora (E) (Figure 5)
Buccioidae Buccininae
Buccinidae Cantharinae
Hesperistemia (E) (Figure 7)
Solenosteira (P) (Figure 36)
Buccinidae Engininae
Buccinidae Metulinae
Celatoconus (E) (Figure 9)
Metula (R)
Buccinidae Phosinae
Cymatophos (P) (Figure 23)
Rhipophos (E) (Figure 10)
Strombinophos (P)
Columbellidae Columbellinae
Eurypyrene (E) (Figures 49, 50)
Microcythara (P)
Parametaria (P) (Figures 24,25,26,27)
Columbellidae Anachinae
Macgintopsis (E)
Columbellidae Aesopinae
Columbellidae Strombininae
Sincola (P)
Strombina (P)
Nassariidae Nassariinae
Ilyanassa s.s.
llyanassa (new subgenus i. porcina
complex) (E)
llyanassa (new subgenus /.
scalaspira complex) (E)
Leptarius (E) (Figure 3)
Paranassa (E)

Nassariidae Bulliinae
Calophos (E) (Figure 6)
Nassariidae Trajaninae
Trajana (R)
Fasciolariidae Fasciolariinae
Fasciolaria s.s.
Liochlamys (E)
Terebraspira (E) (Fig. 33)
Fasciolariidae Fusinae
Fasciolariidae Peristerniinae
Latirus s.s.
Melongenidae Melongeninae
Echinofulgur (E)
Melongena s.s.
Miccosukea (E) (Fig. 43,44,47,48)
Rexmela (Fig. 56)
Tropochasca (E) (Fig. 8)
Melongenidae Busyconinae
Busycon s.s. (R)
Busycotypus s.s. (R)
Busycotypus (n. subgen.1
amoenum complex) (E)
Busycotypus (n. subgen.2
libertiensis complex) (E)
Pyruella (E) (Figure 37)
Nodicostellaria (R) (Figure 20)
Harpidae Moruminae
Bullata (P)
Eratoidea (E)
Leptegouana (E)
Microspira (E)


- B.


Olividae Olivinae
Cariboliva (R)
Lindoliva (E) (Figures 39,40,45)
Porphyria (P)
Olividae Olivellinae
Mansfieldella (E) (Figure 11)
Olivella s.s.
Toroliva (E)
Pleioptygma (R) (Figure 32)
Pleioptygma (n. subgen. -
complex) (E)
Turbinellidae Turbinellinae
Turbinella (R) (Figure 62)
Turbinellidae Vasinae
Hystrivasum (E) (Figure 35)
Volutidae Scaphillinae
Conomitra (R)
Conus (un-named subgen
(Figures 41, 42)
Contraconus (E) (Figures 28,29)
Magelliconus (R) (Figures 54,55)
Virgiconus (R) (Figure 19)
Ximeniconus (R) (Figure 38)
Terebridae Terebrinae
Terebridae Hastulinae
Terebridae Strioterebrinae
Strioterebrum (Figure 64)
Turridae Turrinae
Turridae Turriculinae
Knefastia (R)
Turridae Clavinae
Buchema (P)

P. lindae

us) (E)

Cymatosyrinx (P)
Sedilia (E)
Splendrillia s.I.
Turridae Mangeliinae
Tenaturis (P)
Turridae Cochlespirinae
Turridae Daphnellinae
Turridae Mitrolumninae
Bivetopsia (R)
Cancellaria s.s.
Extractrix (P) (Figure 12)
Massyla (P)
Narona (P)
Perplicaria (P)
Trigonostoma s.s. (P)