Citation
Biostratigraphy of selected cores of the Hawthorn formation in northeast and east-central Florida ( FGS: Report of investigation 93 )

Material Information

Title:
Biostratigraphy of selected cores of the Hawthorn formation in northeast and east-central Florida ( FGS: Report of investigation 93 )
Series Title:
( FGS: Report of investigation 93 )
Creator:
Hoenstine, Ronald W
Place of Publication:
Tallahassee
Publisher:
State of Florida, Dept. of Natural Resources, Division of Resource Management, Bureau of Geology
Publication Date:
Language:
English
Physical Description:
viii, 68 p. : ill. (some col.) ; 23 cm.

Subjects

Subjects / Keywords:
Geology, Stratigraphic -- Miocene ( lcsh )
Micropaleontology -- Florida ( lcsh )
Geology -- Florida ( lcsh )
Hawthorn Formation ( lcsh )
City of Tallahassee ( local )
City of Ocala ( local )
Duval County ( local )
Sediments ( jstor )
Diatoms ( jstor )
Upwelling water ( jstor )
Geology ( jstor )
Species ( jstor )
Genre:
bibliography ( marcgt )
non-fiction ( marcgt )

Notes

Bibliography:
Bibliography: p. 37-40.
Statement of Responsibility:
by Ronald W. Hoenstine.

Record Information

Source Institution:
University of Florida
Rights Management:
The author dedicated the work to the public domain by waiving all of his or her rights to the work worldwide under copyright law and all related or neighboring legal rights he or she had in the work, to the extent allowable by law.
Resource Identifier:
022374171 ( aleph )
16684663 ( oclc )
AEW2268 ( notis )
86620719 ( lccn )

Full Text
STATE OF FLORIDA DEPARTMENT OF NATURAL RESOURCES
Elton J. Gissendanner, Executive Director
DIVISION OF RESOURCE MANAGEMENT Charles W. Hendry, Jr., Director
BUREAU OF GEOLOGY Steve R. Windham, Chief
REPORT OF INVESTIGATION NO. 93
BIOSTRATIGRAPHY OF SELECTED CORES OF THE HAWTHORN FORMATION IN NORTHEAST AND EAST-CENTRAL FLORIDA
By
Ronald W. Hoenstine
Published for the BUREAU OF GEOLOGY DIVISION OF RESOURCE MANAGEMENT
FLORIDA DEPARTMENT OF NATURAL RESOURCES TALLAHASSEE 1984




SCIENCE
LIBRARY
DEPARTMENT
OF
NATURAL RESOURCES
BOB GRAHAM Governor
GEORGE FIRESTONE JIM SMITH Secretary of State Attorney General
BILL GUNTER GERALD A. LEWIS
Treasurer Comptroller
RALPH D. TURLINGTON DOYLE CONNER Commissioner of Education Commissioner of Agriculture
ELTON J. GISSENDANNER
Executive Director
ii




LETTER OF TRANSMITTAL
)
Bureau of Geology Tallahassee
February 15, 1984
Governor Bob Graham, Chairman
Florida Department of Natural Resources
Tallahassee, Florida 32301
Dear Governor Graham:
The Bureau of Geology, Division of Resource Management, Departk' ment of Natural Resources, is publishing as Report of Investigation No.
93, "Biostratigraphy of Selected Cores of the Hawthorn Formation in Northeast and East-Central Florida'," prepared by Dr. Ronald W. Hoenstine, Bureau of Geology staff.
A knowledge of the paleoenvironmental conditions present during the
period of Hawthorn deposition is essential to an understanding of this important phosphate-bearing formation. This report identifies heretofore undescribed microflora and it attempts to both date Hawthorn sedimentation and to reconstruct environmental conditions present along Florida's
northeast coast during the Middle Miocene and Early Pliocene.
Respectfully yours,
Steve R. Windham, Chief Bureau of Geology
y
Jiii




Printed for the
Florida Department of Natural Resources
Division of Resource Management
Bureau of Geology
Tallahassee
1984
iv




TABLE OF CONTENTS
Page
introduction ........................................................... 1
Purpose of Study ....... ............................................ 1
Previous Work ................................ ..... .... .............. 5
Metric Conversion Factors ........................... ................. 6
M ethods .......... ................................ ................... 6
Sample Preparation.................................................. 6
C ounts ................ ............................................ 6
Study Area ........................................................... 7
Stratigraphy ......... ................................................. 7
Stratigraphic Relationships.................. ........................... 7
Lithology ........................... .... ............... ............ 10
Zonation .......... ................................................... 10
Microfossil Correlation......................................... 10
Distribution of Siliceous Microfossils .................................12
D iscussion .......... ................................................. 22
Zone Occurrences...................................... ........... 22
Delphinels penelliptica Zone ............................................ 22
Coscinodiscus pllcatus/Delphlnels penellptica Zone ................... .... 25
Cosclnodiscus plicatus Zone ............................ .............. 25
Upwelling/Cool Water Current .......................................... 28
Pilocene Data ............................................... 28
Diatom Molds .............................. .................. 34
Paralla sulcata ...................................................... 34
Summary and Conclusions ............................................. 35
References ................................................... 37
V




LIST OF FIGURES
Figure Page 1. Location of study area ............................................ 3
2. Location of core and well cuttings.................................. 4
3. Generalized Ibopach of the Hawthorn Formation in the study area, contoured in t ............................................... 8
4. Abbott's Atlantic Miocene Silceous Microfossil Zones showing the substitution of Rhaphonels anceufla and the marker diatoms, allicoflagellate species and
planktonlc diatoms found associated with the zones (Abbott, 1978) ......... 11
5 Coelation of diatom zones defined by Cavallero (1974); Schrader (1973); Andrews (1976); Planktonic Foraminiferal Zones of Blow (1969); Calcareous Nannofobell Zones of Martini and Worely (1970) and Siliceous Microfosil Zones
of Abbott (1979) (from Abbott, 1978) ................................. 13
6 Location of diatomaceous cores .................................. 14
7. Location of cores with diatom mold occurrences .................... 15
8. Chart showing the distribution of blostratigraphic zones, dissolution assemblage, foraminifera, diatom molds and formational contacts ......... 16
9. DIstribution of diatoms in terms of brackish, upwelling, and warm water indicators and numbers of species for the Cumberland Island Core ........ 20 10. OD stribution of diatoms in terms of brackish, upwelling, and warm water
indicators and numbers of species for W*670 ........................... 21
11. Dietibution of diatoms in terms of brackish, upwelling, and warm water
indicators and numbers of species for W-13751 .. ...................... 23
12. Distribution of diatoms in terms of brackish, upwelling, and warm water
indicators and numbers of species for W.13744 ......................... 24
I3 Major currents of the North Atlantic ................................. 28
14. Distribution of diatoms in terms of brackish, upwelling, and warm water
indicators and numbers of species for W-5906 ......................... 29
15. DOtistribution of diatoms in terms of brackish, upwelling and warm water indicators
and numbers of species for W-13958 ................................ 30
16. DIstribution of diatoms in terms of brackish, upwelling, and warm water
Indicators and numbers of species for the St. Lucle core ................ 31
vi




TABLE
1. Diatom species utilized as environmental indicators in this study ............ 19
PLATES
1. Actinocyclus octonarlus, Actinocyclus Ingens, and Actinocyclus elliptious ....... 43
2. Actinoptychus senarlus,% Actinocyclus level, Actinoptychus aft. A. mlnutus,
and Blddulphla rhombus ............................................ 45
3. Blddulphia tuomeyl, and Biddulphia reticulum ............. .............. 47
4. Cosclnodiscus aplculatus, CoscInodiscus vetustissimus, and Coscinodiscus
lewislanus .............. ................................ 49
5. Coscinodiscus pertoratus, and Coscinodiscus asteromphalus ................ 51
6. Cussla praepaleacea, and Cymatogonle amblyoceras ....... ........ 53
7. DelphInels penelliptica, Delphinels engustata, Delphinels surrella, Delphlnels
biserlata, Diplonels smith, and Diplonels bombus ....................... 55
& Navicula of. N. directs, Navicula pennata, and Navicula hennedyl ........... 57
9. Paralla sulcata, Melosira westil, and Podosira of. R stelliger .............. 59
10. Rhaphoneis amphiceras, Rhaphonels fatula, Rh.tphonels gemmifera,
Rhaphonels of. R. angularis, Rhaphonels lancetulla, and
Rhaphonels adamentea .............................................. 61
11. Tflceratum reticulum, Ticeratium condecorum, and Triceratium spinosum ...... 63 12. Xenthiopyxis sp., Thalasslothrlx longissima, Rachynels aspera, Thalassioneme
nltzscholdes, and Fragilarla sp........................................ 65
13. Distephanus stauracanthus, Mesocena circulus, Distephanus crux, Dictyocha
rhombica, and Distephanus C. D. bolivlensis............................ 67
vii




viii




BIOSTRATIGRAPHY OF SELECTED CORES OF THE HAWTHORN FORMATION IN NORTHEAST AND EAST-CENTRAL FLORIDA
By
Ronald W. Hoenstine
INTRODUCTION
PURPOSE OF STUDY
Historically, the Hawthorn Formation has been a catch-all for Miocene sediments in peninsular Florida, Georgia, and parts of South Carolina (Abbott and Andrews, 1979). This extremely complicated formational unit which consists generally of clay, carbonates (primarily dolomite), and clayey, quartzose, phosphatic sand, was named by Dall and Harris (1892) after the town of Hawthorne, Florida. During the last few years considerable interest has been focused on these sediments because of the formation's phosphate content.
Investigators have relied primarily on highly weathered surface outcrops, spoil banks, or auger holes for obtaining fossil specimens from the Hawthorn Formation. These outcrops are frequently so deeply weathered that even fossil molds have been obliterated. When present, common fossils include the oyster Ostrea normalls, a scallop Pectenacanlkas sp., and large heads of the colonial coral Siderastraea sp. (Cooke, 1945). In addition, the fullers earth mines at Quincy and Midway, Florida, have yielded bones identified as that of the dugong (manatee-like) Hesperobiren crataegens/s (Cooke, 1945). Primarily, the early Hawthorn studies were based on field observations that emphasized mineral identifications and geographic distribution with minimum attention given to microscopic examination and subsequent blostratigraphic analysis. Thus, very little work has been done on determining the age of the sediments or the paleoenvironmental conditions present during the period of Hawthorn deposition, except in relatively general terms.
Factors which hindered these early workers included the minimal biogenic carbonate content, extensive dolomitization, and in northeast Florida, the predominantly siliceous nature of the Hawthorn sediments. As a consequence, blostratigraphic information in this paper is tied to siliceous organisms whose stratigraphic value have been recognized and developed only in recent years. The presence of more widely understood groups such as foraminifera or coccoliths, are of secondary correlation value due to their sporadic occurrences in the Hawthorn. Another problem in past years was the paucity of core coverage that resulted in a strong dependence on well cuttings, which were usually taken at 10-foot intervals. Hence, biostratigraphic information, confined to a narrow interval, could be overlooked.
Recent advances in worldwide diatom and silicoflagellate blostratigraphic correlation, especially the sequence of events in the sediments of the Atlantic Coast for the Miocene (Abbott, 1978; Andrews, 1979), have




2 BUREAU OF GEOLOGY
now made possible comparative studies of such deposits as the Hawthorn Formation. The extremely close relationship found to exist between oceanic diatom assemblages and diatomaceous sediments of similar age from coastal regions has enhanced the value of coastal zonations in biostratigraphic studies (Abbott, 1978). Diatom blostratigraphic zonations developed for the Pacific Ocean (Burkle, 1972) and for the Indian Ocean (Schrader, 1973) have also proved invaluable.
Cores recently obtained by the Florida Bureau of Geology through a cooperative study with the United States Bureau of Mines represent a significant attempt in recent years to investigate the subsurface stratigraphy of the Hawthorn Formation. This augmented data base, in addition to numerous well cuttings on file at the Bureau of Geology, coupled with the recent advances in diatom stratigraphy, present an opportunity to undertake a detailed biostratigraphic study of selected cores from this complex and little understood formation. The study area for this report is shown in figure 1.
Located primarily in northeastern and east-central Florida, these cores were drilled through Hawthorn sediments into the underlying limestone (figure 2). The cores offered a number of unique opportunities: 1) to examine complete sections of Hawthorn sediments, 2) to observe and determine the sequence of diatom assemblages, and 3) to determine the existence, if any, of a relationship between microfossil occurrences and sediment types.
Well-preserved assemblages of diatoms and silicoflagellates were observed in five cores, and two sets of water well cuttings, occurring along the coast. In addition to these cores and wells, diatom molds were observed in several inland cores in Putnam and Clay counties. Two cores had co-occurrences of coccoliths, diatoms, silicoflagellates, and foraminifera which offered an opportunity to correlate marker species of diverse groups.
This paper presents an outline of new biostratigraphic data and its interpretation using Hawthorn microfossils. The intention is to shed light on the environmental conditions that existed during the deposition of Hawthorn sediments within the study area. A discussion of inferred paleoenvironmental changes which occurred during the period of Hawthorn deposition relative to modern conditions is presented with an explanation of assumptions.
This study is regarded as a preliminary investigation. Further microscopic examination and analysis of additional cores, especially in south Florida, is anticipated in order to determine the extent of the Pliocene age that has been newly assigned to some "Hawthorn-like" sediments.




REPORT OF INVESTIGATION NO. 93 3
NASSAU
CLAY 'PUTNA L fL AGLE VOLUSIA
F e INOLe ORANGE
' INDIAN s.. .... IVlER
ST. LUCIS 50 0 50 100MILES ....
50 0 -50 100KILOMETERS
Figure 1. Location of study area.




BUREAU OF GEOLOGY
CUMBERLAND ISLAND CORE
W-670
W-13815
/ W- 14619 W-14193
W-13751
a W-13769
W-14477
W-13744
W-14354
SCORES +CUTTINGS'
W-5906
W-13490
W-13551 j*** W-13881 W-13942 W-1 3957 W-13964 W- 13958
10 0 10 20 30 40 M
1 ID 102030400KM
-ST. LUCIE CORE
Figure 2. Location of cores and well cuttings.




REPORT OF INVESTIGATION NO. 93 5
PREVIOUS WORK
Dall and Harris (1892) referred to beds of phosphatic rock and greenish clays observed at Nigger Sink, Newnansville well, and Sullivan's Hammock as the "Hawthorne beds" after the town of Hawthorne, Alachua County, Florida. These same beds had been referred to earlier by L. C. Johnson (1888) in an unpublished report for the United States Geological Survey. Though Dall and Harris mentioned the mining of phosphatic limestone for use as fertilizer near Hawthorne, they did not erect a type section. Matson and Clapp (1909) included part of the underlying Cassidulusbearing limestone, now called the Suwannee Limestone, with the Hawthorne beds of Dall and Harris. Vaughan and Cooke (1914) felt that the Hawthorn was nearly synonymous with the Alum Bluff Formation as defined by Matson and Clapp (1909) and recommended that the name "Hawthorn" be dropped. Cook and Mossom (1929) redefined the Hawthorn Formation to include the Hawthorne beds and the Sopchoppy Limestone of Dall and Harris (1892), in addition to the Alum Bluff Formation and the Duplin Marl as defined by Matson and Clapp (1909).
More recently, Cooke (1945) transferred some Late Miocene age beds, recognized by Matson and Clapp (1909) as part of the Hawthorn, to the Duplin Marl. Bishop (1956) identified marine and nonmarine Hawthorn deposits in Highlands County. More recent contributions include: Ketner and McGreevy (1959), Carr and Alverson (1959), Reynolds (1962), Wilson (1977), Miller (1978), Riggs (1979a,b), Reik (1980), Leroy (1981), Scott and MacGill (1981), and Scott (1982, 1983). Although others have discussed this formation, the contributions of the above mentioned authors are especially significant in their attempts to define or redefine the Hawthorn Formation.
Fossils previously reported from the Hawthorn Formation in the study area (figure 1) include molluscs, benthic foraminifera, diatoms, and some well-preserved vertebrate remains. Sellards (1916) identified bones and teeth of Mesocyon (?) iamonensis Sellards (a dog), and Parahippus leonensis Sellards (a three-toed horse) found near Tallahassee in the Hawthorn Formation. The most notable investigations of molluscs are those of Gardner (1926) and Puri (1953).
Although no comprehensive microfossil investigations of the Florida Hawthorn Formation have been reported, several studies of Atlantic Coastal sediments have been undertaken. The first records of siliceous microfossils from the Atlantic Margin began with the diatom studies of Bailey (1841, 1844) and Ehrenberg (1844, 1854).
More recent studies of the Atlantic Coastal Plain include a discussion of diatom molds from opaline cristobalite (Wise and Weaver, 1973) and a sparse collection of fish teeth and diatoms (W. K. Posser in Johnson and Geyer, 1965) from the Coosawhatchie Clay occurring in South Carolina. Abbott (1974a) reported on the occurrence of a well-preserved diatom assemblage in the Coosawhatchie Clay of Jasper County, South Carolina.




6 BUREAU OF GEOLOGY
Ernissee (1976) identified a number of dinoflagellates from the same unit. Abbott and Andrews (1979) related the Coosawhatchie Clay in South Carolina and time equivalent strata at Berry's Landing, Georgia, to the North Pacific zonation of Schrader (1973) utilizing diatoms and silicoflagellates.
Specific siliceous zonations of Atlantic coastal sediments include: Cayallero (1974), Andrews (1979), and Abbott and Ernissee (1977). These attempts were influenced and in part derived from zonations developed earlier in the Pacific Ocean by Martini (1971), Burkle (1972), and Schrader (1973). Abbott (1978) published the first significant microfossil zonation of Miocene strata along the Atlantic Margin of North America using diatoms and silicoflagellates. This zonation, along with Andrews' (1979) correlation of Miocene strata of the Chesapeake Bay region of Maryland, was utilized in this study.
METRIC CONVERSION FACTORS
The Florida Bureau of Geology, in order to prevent duplication of parenthetical conversion units, inserts a tabular listing of conversion factors to obtain metric units.
Multiply by to obtain
feet 0.3048 meters
inches 2.5400 centimeters
inches 0.0254 meters
miles 1.6090 kilometers
METHODS
SAMPLE PREPARATION
Siliceous samples were prepared following procedures as recommended by Abbott (1978). Procedures for calcareous samples were similar except that HCI was not used and caedex was utilized as the mounting medium. A total of 780 slides mounted in either hyrax or caedex were made using this procedure. These were examined by making systematic traverses with a mechanical stage under a magnification of 600 X.
COUNTS
Frequencies of taxa were analyzed quantitatively using counts of 300 specimens whenever possible. Individual specimens were frequently noted by recording the coordinates of the mechanical stage. Recorded information included species identification and counts.




REPORT OF INVESTIGATION NO. 93 7
STUDY AREA
The area of investigation is located in northeastern and east-central Florida bounded to the north by the Florida-Georgia boundary, to the south by St. Lucie County, to the east by the Atlantic Ocean, and to the west by a centerline that approximates the center of the Florida peninsula (figure 1). Although cores and well cuttings were examined throughout the study area, a total of 17 cores and two well cuttings were found to be especially productive in terms of yielding biostratigraphic data from various microfossil groups including diatoms, silicoflagellates, foraminifera, coccoliths, and ostracoda (figure 2). This report is primarily concerned with diatoms and silicoflagellates. The most complete core coverage was in the northern part of the study area, reflecting in part the presence of thick Hawthorn sediments in that region.
STRATIGRAPHY
STRATIGRAPHIC RELATIONSHIPS
The Hawthorn Formation, which is present in the subsurface over much of the study area, is missing in parts of Flagler, Volusia, Seminole, and Lake counties. The thickness of this formation is extremely variable with maximum values occurring in Duval County in the northeastern part of the study area (figure 3). An observed thickness of at least 420 feet was present in Duval County (W-14619), a core which did not completely penetrate the Hawthorn. This may be compared to well cuttings from W-10920, located in Duval County, which penetrated through a Hawthorn section measuring 491 feet in thickness.
The noted absence or thinning of Hawthorn sediments in specific areas may be attributed in part to nondeposition or attenuation along the flanks of a past structural high. The occurrence of an apparently shallow water microfossil assemblage near the top of the Hawthorn in Brevard County (W-5906), in contrast to a deeper water assemblage southward, may be supportive of this premise. Alternatively, the missing sediments may be attributed to deposition and subsequent erosion. Deposition of the Hawthorn Formation beyond its present limits has been postulated by Scott and MacGill (1981) and Scott (1981).
Throughout the study area, the Hawthorn Formation is unconformably overlain by undifferentiated sands and clays of Plio-Pleistocene age, except for coastal areas of Flagler County, where the overlying sediments are those of the Anastasia Formation, a coquinoid limestone also of Pleistocene age. The contact between the undifferentiated sands and clays and the underlying Hawthorn is generally gradational with the top of the Hawthorn being placed at the first significant occurrence of phosphorite in conjunction with a sandy, clayey dolomite or dolomitic, clayey sand (Scott, 1983). A problem frequently encountered in the identification of this contact is the presence of phosphorite in amounts greater than 2 percent in the overlying sediments. This occurrence is




8 BUREAU OF GEOLOGY
' 400'
500'
400' 300'
00t
300'
200'
100'
100',
o
HAWTHORN ,, NOT PRESENT
II
O
100100
200' 200<)n 200' -- 300' S0 20 30 40 o 200
, o ,p 3001 400' 400
Figure 3. Generalized isopach of the Hawthorn Formation in the study area, contoured in feet.




REPORT OF INVESTIGATION NO. 93 9
primarily attributed to reworking of Hawthorn sediments. Within the study area, the top of the Hawthorn is usually a clayey, sandy, phosphatic dolomite or a clayey, dolomitic, phosphatic sand. In addition, the sediments lack shell material and are normally an olive-green color (Scott, 1983).
An additional problem in picking the Hawthorn top was encountered in the W-12958 and St. Lucie cores. These diatomaceous sediments which included diatoms of Early Pliocene age were more calcareous than the Middle Miocene diatomaceous sediments; an observation in part attributed to the absence of dolomitization which might remove included cooccurrences of calcareous nannoplankton and foraminifera. This was the primary observed difference in lithology. Clay analyses done by Dabous (personal communication, 1981) revealed the presence of montmorillonite and palygorskite, common constituents of the Middle Miocene Hawthorn Formation. Palygorskite has rare, sporadic occurrences in sediments younger than the Miocene. Phosphorite content, which averaged a few percent, was similar in abundance to that found in the Miocene age sediments in the northern part of the study area.
The formal stratigraphic classification of these sediments remains in question. These younger sediments may prove to be a new formation possessing many of the Hawthorn lithologic characteristics. However, Fogle (personal communication, 1981) identified the Hawthorn Formation in the St. Lucie core as occurring in the interval from 150 to 547 feet (below land surface). This would place the Pliocene assemblage described in this study (-282 to -387 feet) well within the Hawthorn. Therefore, considering the extreme variability of the Hawthorn sediments and the similarity in mineralogy, phosphorite content, and relative difficulty in distinguishing between the younger sediments and the Miocene Hawthorn, the writer has been inclined to treat these "Hawthorn-like" sediments as a lithofacies of the Hawthorn Formation (Huddlestun and others, 1982). Future drilling is planned which should more fully identify and delineate the areal extent of these sediments.
The Hawthorn Formation in the study area overlies unconformably the Ocala Group limestones of Late Eocene age. An exception occurs in Indian River and St. Lucie counties where Hawthorn sediments are underlain by limestone sediments that may be of Oligocene age based on foraminiferal occurrences.
In contrast to the contact separating undifferentiated sands and clays from the underlying Hawthorn, the boundary between the Hawthorn Formation and the underlying Eocene age limestones was readily apparent. This distinctive lithologic boundary offered a sharp contrast between the dolomitic sediments of -the lower Hawthorn and the underlying richly fossiliferous, white-to-cream colored Ocala Group limestones. The Avon Park Limestone is often distinguished from the younger Ocala Group by the occurrence of numerous conical-shaped foraminifera, such as Dictyoconus cookel (Applin and Jordan, 1945). The generally porous and permeable limestones comprising the Ocala Group and Avon Park




10 BUREAU OF GEOLOGY
Limestones and local permeable zones of the lower Hawthorn form the upper part of the Floridan Aquifer. Conversely, the clayey sands of the upper Hawthorn may act as an aquiclude retarding downward water seepage and in places (i.e., eastern Orange County) retarding the upward movement of water.
LITHOLOGY
Hawthorn sediments throughout the study area are extremely variable, ranging from phosphatic, clayey sands, and dolomitic, clayey silts to carbonates. In addition to common occurrences of clay or sand lenses, a basal dolomite is also present in the Hawthorn sediments, represented best in the northern cores (Scott, 1982; 1983).
Common to the Hawthorn Formation and an important lithologic guide to its identification is the presence of phosphorite. This constituent, with occasional occurrences in excess of 50 percent of the sediment sample, is generally disseminated throughout a sandy carbonate or silt-clay matrix. The phosphorite is present in variable amounts that commonly range from less than one percent to 35 percent of the sample with average values of approximately five percent (visual estimate).
A number of Hawthorn samples in the study area have been studied by x-ray diffraction in order to identify the clay components for paleoenvironmental inferences (Reik, 1980; 1982). These clay analyses indicated the presence of palygorskite, sepiolite, montmorillonite, chlorite, and kaolin. Palygorskite and montmorillonite were the most abundant clays.
ZONATION
MICROFOSSIL CORRELATION
The diatom correlation and zonation scheme used in this study was primarily based on Abbott's (1978) zonation of Miocene strata along the Atlantic margin of North America and Pilocene fauna described by Lohman (1938), Burkle (1972), and Jouse (1974). Additional emphasis was given to the stratigraphic ranges of various species of Rhaphonels developed by Andrews (1975) for the Chesapeake Bay area.
Diagnostic species utilized in the zonal correlations of the Florida diatomaceous sediments were numerous and especially resistant to dissolution. Consequently, flora with similar ranges to species in Abbott's zonation scheme are here utilized as index markers for the Florida Miocene correlation.
Diatomaceous sediments encountered in three cores and one set of cuttings from the northern half of the study area generally corresponded to three Atlantic Miocene siliceous microfossil zones proposed by Abbott (1978). These three Middle Miocene zones recognized in the cores include Abbott's Delphinels penelliptica, Delph/nels penellptical Coscitcus p/icatus, and Coscinodslacus pilcatus zones (figure 4).
Abbott's correlations were found to be generally applicable to diatoma-




REPORT OF INVESTIGATION NO. 93 11
MIOCENE
AGE
EARLY MIDDLE
Delphinls DeIlphinols Actinoptychus Delphinals ovota Delphinls penlliptlco Coinodiscua Z ONES heliopito ovoto Delphinels penelliptica Coscinodlicui plicatus ponelliptic plica tu
4 Actlinoptychus hellopelo
4 Novicutopsis spp.
DeIphinels ovoto Deolphina penelttiptico Coscinoadiscus plicatus Dilstophoanus stouroconthus S Actinocyclus elliptlcus Annollus colifornicus I Bruniopsis mirobills Cosclnodiscus lewislionus Cosclnodiscus prosyobel S Coscinodlscus yobiel S Gusslo proopoeoacea S Denticula hustedil Denticulo louto ............ Mactoro 1ello
Modiartio splendida
Raphidodiscus morylondicus Rhophonels fossil S Rouxio colifornico S Rouxlo diploneides Rouxio noviculoldes
Figure 4. Abbott's Atlantic Miocene Siliceous Microfossil Zones showing the substitution of Rhaphonels lancetulla and the marker diatoms, silicoflagellate species and planktonic diatoms found associated with the zones (Abbott, 1978).




12 BUREAU OF GEOLOGY
ceous sediments present in the northern half of the study area. However, his correlation scheme was modified in part to make it more adaptable to the observed flora (Abbott, personal communication, 1981). This departure from Abbott's zonation involved the substitution of Rhaphonels lancettulla for Coscinodiscus plicatus in Abbott's Cosclnodlscus plicatus/ Delphinels penelliptica and Coscinodiscus picatus zones. These species have a similar range; but possibly due to the environment of deposition and associated selective weathering related to structure, the diatom Coscinodiscus plicatus had an extremely sporadic occurrence in contrast to the more abundant Rhaphonels lancettulla. Many species, including Coscinodiscus plicatus, which belong to the genus Cosclnodlscus, are particularly susceptible to the effects of dissolution due to their fragile structure. Consequently, the utilization of Rhaphonels lancettulla, a species with some resistance to dissolution, was necessary in order to meet desired criteria ascribed to index species, that is, being both widespread and abundant.
Abbott's Miocene Atlantic margin zonation is shown in figure 5 along with a notation underscoring the substitution of Rhaphonels lancetulla for Coscinodiscus plicatus. Figure 5 is a correlation of planktonic foraminifera zones of Blow (1969) and calcareous zones of Martini and Worsley (1970) to Abbott's Atlantic Margin zones (Abbott, 1978).
DISTRIBUTION OF SILICEOUS MICROFOSSILS
The siliceous microfossil groups included diatoms, silicoflagellates, and dinoflagellate species. In addition, phytoliths were noted throughout the study area.
The distribution of diatomaceous cores in the study area was found to be limited to near the present coast (figure 6). However, nine cores, the majority of which were located further inland, contained diatom molds (figure 7). Several of the cores (W-13958, W-13751, W-13844) had diatom molds present in sediments below diatomaceous sediments. In all occurrences, the diatom molds were present in sediments of the middle or lower Hawthorn (figure 8). These molds were primarily circular structures belonging to the centrales group of diatoms. Diatom molds in W-14477, a core located in Putnam County, occurred in sediments consisting primarity of a poorly indurated, very fine-grained, clayey dolomite. Similarly, diatom molds in W-14354, another core located In Putnam County, were present in sediments consisting of a poorly indurated clay with associated dolomite.
Additional cores with sediments containing diatom molds occur in Clay, Duval, St. Johns, and Brevard counties. Miller (1978) has observed diatom molds in Columbia and Baker County cores. In general, these molds occurred in single short intervals in sediments ranging from moderately indurated clays to fine-grained dolomite. Hawthorn diatomaceous sediments were present in five cores and two sets of well cuttings (figure 6). These cores and well sites are all located within a few miles of the coast. W-13751 had special significance in that




REPORT OF INVESTIGATION NO. 93 13
EUROPEAN ABBOTT BLOW MARTINI a MY STANDARD U.S. EAST FORAMINIFERAL WORSLEY NANNOPLANKTON
STAGE COAST ZONES 1969 ZONES 1970
__________ __________ __________ ZONES 1970
Coscinodiscus N 12 plicoatus* NN6
Delphine ls
penalliptico
- Srrovllion Coscinodiscus
i" pllcotus N I I
W Delphineis
2Z NIO0
,, penelliptica N 10
0
"-NN5 13 Delphlnals
ovato N 9 Delphinols
penalllptlco
14 Longhlan
Delphinels N 8 ,. _ ovoto
W NN4
5I Burdigallon Actinoptychus N6 N7
heliopelto N N3
* Rhaphoneis lancetulla substituted for Coscinodiscus plicatus in this study.
Figure 5. Correlation of diatom zones defined by Cavallero (1974); Schrader (1973); Andrews (1976); Planktonic Foraminiferal Zones of Blow (1969); Calcareous Nannofossil Zones of Martini and Worsly (1970) and Siliceous Microfossil Zones of Abbott (1979) (from Abbott, 1978).




14 BUREAU OF GEOLOGY
,,-CUMBERLAND ISLAND CORE W-670
-- w-13751
--T"W-13844
CORES
CUTTINGS
1 \ --.. ...
W-5906
to o 10 ,20 30 40M .
oK L & W-13958
19212000OKM
ST. LUCIE
.. CORE
Figure 6. Location of diatomaceous cores.




REPORT OF INVESTIGATION NO. 93 15
" W- 14619
W -W-14193 ...-W I13751I
'- 3769
W-14477 W-14354
W-13744
7 W-13964
10 0 10 M W-13958 o o o 2d o ou '---10 0 10 20 30 40 50KM
Figure. Lctonof cores with diatom mold occurrences
-Flaure?.. Locationof cores with diatom mold occurrences. -




SAREDUC ION RATIO 12x




16 BUREAU OF GEOLOGY
10c
W-13815
. W-13751 .. W-14193 ," CUMBERLAND
ISLAND CORE W-14619
0-7
(MS L)
o- 5M RL)W....... i
-20 .70,
-20
-0
-250 L-60:u
-400-1 0 _401
-100)
-40 -0
-528 -510
-488
uL
Rigure 8. Chart showing the distribution of biostratigraphic zones, dissolution assemblages,. foraminifera. diatom molds and formational contacts.
L -- -:-275
I-I Il -II
--121
-4 L120 -sl t,
,- -488
Figur. e &. Chart showing the distribution of biostratigraphic zones, dissoIuticn assemblages,, foraminifera, diatom molds and formatilonal contacts.




REPORT OF INVESTIGATION NO. 93 17
,1-13769
W-13551 W-13942 W-13957 ,4 W-13957
+45 440 W-13744 W-13881 W-13964 W-13958 ST. LUCIE W-14477 W-14354 '2 W-13490 *20 -2 CORE
;11 37 -1 W-5906 W-s13881
0
m-80
-90.7 ~~~,.44 -591406 .4 .1. 26 2
112 -,-O-loc n1 a thrIk, e im ns a Mil iI
O 3138
484
Do m1.. mol ds0
*033
Molskfa o ls a g
S-547.1
on r ainiferalcts n
- -23 8 8 6 -145 .
-167 -162o 16
Pl Doo- lds7n 7
Hawthorn Formation contact (Top & Bottom)
*Well cuttings
. ZO -20
.3 .260 -104 m .1127
Cosilnodleous pllcatus zone .130
Cosclnodlacus pllcatus / Delphlneus penelllptlca zone .i137
FDolphinous penelllptlca zone-3614=31
I Diatom molds <.J
IMollusk frag,foram mlsadfrags burrows-5
SForaminiforal counts
IDissolution assemblage
Hawthorn Formation contact (Top a B~ottom)
- Well cuttings




18 BUREAU OF GEOLOGY
Pliocene-age diatoms were found in the overlying, undifferentiated sand and clays.
Diatomaceous sediments ranged in thickness from a minimum value of 13 feet (W-13744) to a maximum value of 150 feet in the St. Lucie core (figure 8). Diatomaceous sediments in the northern part of the study area were predominantly dolomitic, silty clays with minor amounts of sand and phosphorite. In contrast, the sediments with included diatoms in the southern cores consisted of dolomitic, clayey silts with calcareous sands present as important components (up to 40 percent).
The siliceous microfossils identified totaled 170 species of diatoms, 13 species of silicoflagellates, and two species of dinoflagellates. Diagnostic diatoms in Hawthorn sediments of the northern cores were of Middle Miocene age while diatoms in "Hawthorn-like" sediments of the southern two cores were entirely Pliocene in age.
Diatoms occurring in the northern cores and well cuttings (Cumberland Island, W-670, W-13751, W-13844) can be placed in one or more of Abbott's three late Middle Miocene zones. These biostratigraphic zones included the Delphinels penelllptica, Coscinodiscus plicatis/Delphinels penelliptica, and Coscinodiscus plicatus zones.
The distribution of fossiliferous intervals sampled in the cores and well cuttings is shown in figure 8. Several of the intervals with sparse assemblages (W-13958, 148-150 ft., and the St. Lucle core, 370-371 ft.) occurred between intervals of abundant diatoms, a circumstance for which no explanation was readily apparent based on lithology.
The diatoms in the northern cores could be divided into two distinct groups: a predominant temperate-to-warm-water assemblage and another group associated with cool, upwelling waters. The temperate-towarm-water assemblage was the only group present in the diatomaceous sediments of the southern cores.
The cool, upwelling species (table 1), which averaged approximately 12 percent of the total assemblage, attained a maximum value of 26.5 percent of the assemblage in the 223-foot interval of W-13751 (figure 11). These forms were completely absent from the Pliocene-age sediments of the southern two cores. Apparently, the conditions necessary for their presence were either absent or substantially diminished to a point that upwelling-water forms were totally absent in the Pliocene environment. Conversely, brackish water species (table 1) were present in both the Miocene and Pliocene sediments.
Other microfossil groups (phytoliths and dinoflagellates), although less abundant, are present throughout the study area, as noted in several cores. Their occurrence has been reported by Abbott (1974b) in diatomaceous clay units of the Hawthorn Formation of South Carolina and Georgia.
Dinoflagellate occurrences, though few, were widespread. Their biostratigraphic value has yet to be realized; however, a better understanding of the diversification experienced by this group beginning in the Middle Miocene may prove invaluable to future biostratigraphic studies.




REPORT OF INVESTIGATION NO. 93 19
Table 1. Diatom species utilized as environmental indicators
in this study, compiled from Abbott and Andrews (1978),
and Abbott (personal communication, 1981).
HIGH BRACKISH COOL WARM SPECIES SALINITY WATER UPWELLING WATER Biddulphla toumeyl X Coscinodiscus nodulifer X Coscinodiscus rothil X Diplonels crabro X Hemidiscus ovalls X Hyalodiscus laevis X Rhaphoneis amphiceros X Thalassionema nitzschoides X Tha/assiothrix longissima X Trachynels aspera aspera X




1 ---- .....t UPWELUNG SPECES o0.0, BRACKISH SPECES
***"" WARM WATER SPECES
Lzm
-Z C* EU. -w3m. C.p.
0 oA. Zone D.p. Zone 0 D.p. C
s&: **, ,**" ;
I-- "*... ..** 1 ....4 o
0- ... .. .'" ." : "
a.a
: ... * I i, ,o. ..* : LU m*** ** 0
470 *2o -290 -300 -10 -3 -330 -340 *50 -3o
CORE DEPTH (FEET, MSL)
Figure 9. Distribution of diatoms in terms of brackish, upwelling, and warm water indicators and numbers of species for the Cumberland Island Core.




50.0.. UPWELLING SPECorIiES / BRACKISH SPECES 0****'** WARM WATER SPECIES 2&0
-270 COE VEP E, MST. -SI -NoI
z o
M 200 C.p. 0
0 *p Zone D.p. Zone
D.p. 0 0 "1
CC... ... a
ILLe
15.0
z
0 0
z
CORE DEPTH (FEET, MSL) Figure 10. Distribution of diatoms in terms of brackish, upwelling, and warm water indicators and numbers of species for W-670.




22 BUREAU OF GEOLOGY
DISCUSSION
ZONE OCCURRENCES
The diatomaceous Hawthorn sediments present in cores in the northern part of the study area were all of late Middle Miocene age (figure 8). These dates and associated paleoenvironmental data were derived almost exclusively from diatoms. An important exception occurred In Nassau County (W-13815) where sediments near the base of the Hawthorn were determined to be of Early Miocene age on the basis of planktonic foraminifera.
In the Atlantic Coastal Plain, Abbott found that the Early and early Middie Miocene sediments were restricted, with one exception, to the shelf north of Cape Hatteras. The one exception was the occurrence of diatomaceous sediments belonging to the Delphineis ovata/Delphlnels penellipdica Zone (Middle Miocene) in Georgia. The Early and early Middle Miocene strata south of Cape Hatteras may be represented by unfossiliferous sediments.
These Early and early Middle Miocene zones were, with one exception (W-13815), entirely absent from sediments studied in Florida. This could be accounted for in a number of ways including: nondeposition, deposition and subsequent erosion and/or strata of this age being represented by unfossiliferous sediments. The presence and appearance of poorlypreserved diatoms in strata at the top of the diatomaceous Hawthorn sediments and in the overlying post-Hawthorn diatomaceous sediments of W-13751 (-33 to -43 ft.) are suggestive of dissolution. In like manner, the absence of flora below the Delphlnels penelliptica Zone in sediments, many of which were dolomitized, may be due to the total dissolution of diatoms in early Middle Miocene and older sediments.
DELPHINEIS PENELLIPTICA ZONE
.Numbers of species (figures 9, 10, 11) were high throughout the recognizable portion of the Delphinels penelliptica Zone for the three northern cores (Cumberland Island, W-670, W-13751). However, W-13744, which had the longest section of Delphinels penelliptica zonal sediments, had markedly fewer species for this zone relative to the other cores (figure 12). A similar trend was noted with respect to the upwelling assemblage (figures 9, 10, 11). Upwelling species had occurrences averaging more than 17 percent of the total assemblage in this zone; a trend analogous to total species numbers. In contrast, the upwelling species recorded in the DephieIs penelliptica Zone of W-13744, with one exception (seven percent), accounted for less than one percent of the assemblage (figure 12).
Brackish water species, which reached a maximum value of 11.6 percent in W-670, averaged less than four percent for all other cores in the Dephinels penelilptica Zone (figures 9, 10, 11, 12). Upwelling species (except for W-13744) greatly outnumbered brackish-water forms throughout this zone.




REPORT OF INVESTIGATION NO. 93 23
The above observations show a fluctuation in species numbers and a
distinct decline of upwelling forms in the Delphinels penelllptlca Zone for W-13744, the most southern core in which this zone was recognized. This is indicative of a stressed environment and associated reduced
assemblage.
Several explanations may account for the reduced flora at W-13744.
Specifically, the sharp decline in upwelling species at this site during the Middle Miocene suggests that the effects of a postulated offshore, coldwater current (Abbott and Andrews, 1979) may not have reached this far south or that it may have moved further seaward. Conversely, if upwelling was the source of these cool-water species, an alternate explanation would suggest a reduction in upwelling intensity due to locally shallow conditions as opposed to deeper water further north. It is also possible that the sediments represented by these cores were not deposited synchronously. Consequently, the period represented by a reduced flora in W-13744 and the noted absence of this assemblage in other cores may be due to synchronous sediments in the latter cores having been removed through erosion. Evidence supportive of this latter premise includes the higher elevation of -132 feet recorded for the top of the
00
********* UPWELLING SPECIES
30.0 BRACKISH SPECIES
N uman WARM WATER SPECIES
;,,.. iD. p.
COn DEPTH (FEE, M8L) A
5i I 0
1.0.
0 1 *0 0 C.p *4 *0. 0 .
C ORE DEPTH (FEET M ) D
-- ; C
iUD.P. . ... ..
I A ; ;* :* 0;:.
F10 . u l
t : sf
0 -- on ***IS
S160 Cfo -k 7 .h Io Iof
I.J. . .
CORE DEPTH (FEET, MSL) Figure 11. Distribution of diatoms in terms of brackish, upwelling, and
warm water indicators and numbers of species for W-13751.




00
30.0 ." UPWELLING SPECIES I,/" BRACKISH SPECIES
S"/ \ ******* WARM WATER SPECIES
0 G14 CORE DEPTH (FEET,MBL) -150 20.0.
CC
o '9* Zone 15 .o- s. Dop.
w *.0
OJ .
a- so~~oD *p.z Dp. onee
zon
I= 10.0 D.p. Zone 0 W 0
5.0 ..
* ...
0 Sl
0 __---_ _- -.. .--,** .,*
-126 -128 *130 -132 -134 -136 -138 -140 142 *144 146 .148 -150
CORE DEPTH (FEET, MSL)
Figure 12. Distribution of diatoms in terms of brackish, upwelling, and warm water indicators and numbers of species for W-13744.




REPORT OF INVESTIGATION NO. 93 25
Delphineis penelliptica zonal sediments present in W-13744 as compared to 168 feet at W-13751, 335 feet at W-670, and 342 feet at the Cumberland Island core to the north.
COSCINODISCUS PLICATUS/DELPHINEIS PENELLIPTICA ZONE
This zone has special significance in that sediments belonging to this zone in W-13751 appear to form a complete section; that is, continuous sedimentation without a break. If all sediments are present this gives a maximum calculated sedimentation rate at this site of 3.2 cm/1000 years.
Species numbers remained high throughout the Coscinodiscus plicatus/Delphineis penelliptica Zone in all cores except W-13751 (figure 11). This core experienced several major reductions in species numbers which were not observed in the other cores.
The cool, upwelling species in this zone made up 10 percent or more of the assemblage for sampled intervals in all cores except W-13751. This latter core recorded both maximum and minimum values for all cores in this zone. Of significance was the marked increase in upwelling species from one percent and lower values observed in the underlying Delphineis penelliptica Zone to over 15 percent in the Coscinodiscus plicatus/ Delphineis penelliptica Zone for W-13744.
Brackish-water forms reached values from five percent to a maximum of 11.6 percent at certain intervals in the Coscinodiscus plicatus/ Delphineis penelliptica Zone in all of the cores. These were maximum core values for the three northern cores (Cumberland Island, W-670, W-13751). In addition, a general reduction in brackish-water species counts occurred from W-670 southward to W-13744 in this zone.
The above data suggest that changes in the environment of deposition during the time represented by the Coscinodiscus plicatus/Delphineis penelliptica Zone were probably local in extent. Several of these changes in the environment were quite conspicuous as indicated by the sharp decline of all species in sedim ents of W-13751 in the middle part of the zone.
COSCINODISCUS PLICATUS ZONE
The Coscinodiscus plicatus Zone was recognized at only one site (W-13751, figure 11). This one occurrence in St. Johns County, with one exception at (-116 ft.), showed a general decrease of brackish species in going upcore, reaching a maximum value of 9.5 percent of the assemblage in that zone (figure 11). The absence of this zone both north and south of this core, may be attributed to erosion or non-deposition of these sediments atother core sites. Support for this premise includes the markedly higher elevation (-115 ft.) recorded at W-13751 for the top of the underlying Coscinodiscus plicatus/Delphineis penelliptica Zone as compared to -310 feet for W-670 and a closer value of 129 feet for W-13744.
In general, the Coscinodiscus plicatus Zone showed an increase in species numbers. The species present in this zone were suggestive of a restricted lagoonal assemblage.




26 BUREAU OF GEOLOGY
Upwelling/Cool Water Current
The co-occurrence of upwelling and temperate-to-warm-water species in all three Middle Miocene biostratigraphic zones is significant, suggesting the mechanism of upwelling or the existence and proximity of an offshore, cool-water current during the Middle Miocene. Supporting data include the presence of well preserved siliceous microfossils, benthic foraminifera, and appreciable concentrations of phosphorite (Haass and Schrader 1979).
Upwelling, as it occurs today off the coast of Peru, requires a narrow shelf and a continuous downwellng front. There is evidence for both a Peru-type upwelling and an arid climate during the early Middle Miocene for northwestern Africa (Haass and Schrader, 1979). As a consequence of upwelling, deeper cold water and associated cooler water diatom species are brought to the surface where they mix with temperate-to-warmwater, coastal diatoms.
Common arguments against the operation of this mechanism off the coast of Florida in the past include the following observations of modern day upwelling: the occurrence of upwelling is primarily off of the western sides of continents, presence of a narrow shelf, and wide circulation (Smith, 1968). Recent studies (Manheim and others, 1975; Burnett and Veeh. 1977) suggest that these arguments may not be as valid as once thought. These studies and observations reveal that the majority of upwelling off the coast of Peru occurs in water depths between 150 and 600 feet with minor upwelling operative in deeper water. In addition, intense upwelling occurs in shallow waters on the Agulhas Bank off South Africa (Summerhayes, 1970). Other evidence for upwelling off east coasts includes observations (Milliman and others, 1975; William Burnett, personal communication, 1981) of variable upwelling off the east coast of Brazil. In addition, Wells and Gray (1960) have observed variable upwelling off the coast of North Carolina. Riggs (1979a) postulates the existence and movement of upwelling waters across a shallow Florida platform during the Miocene. Taylor and Stewart (1959) reported present-day upwelling off the northeastern coast of Florida. Consequently, some of the arguments against the operation of upwelling off the east coast of Florida may be unfounded.
Recent data (Hathaway and others, 1970) point to the existence of a relatively broad shelf off this part of Florida during the Middle Miocene. Furthermore, the diatoms in these Middle Miocene sediments were predominantly benthic and nearshore forms, many of which occur today in water depths of 300 feet or less. Other factors present which are common to areas of upwelling include: the excellent preservation of diatoms and sillcoftagellates in coastal cores, a predominant benthic foraminiferal assemblage, and appreciable concentrations of phosphorite (Haass and Schrader, 1979).
Another factor normally associated with upwelling on the eastern side of oceans is an arid climate. This study noted the presence of phytoliths




REPORT OF INVESTIGATION NO. 93 27
of the Panicoid class in the Middle Miocene diatomaceous sediments. Sporadic in occurrence, this group of microfossils suggests the presence of grasslands or prairies in the region (Twiss and others, 1969). Such vegetation, if widespread, would be indicative of low rainfall, a characteristic of arid climates (Odum, 1959). Alt (1974) and Abbott (1974b) have found evidence for such a climate further north in the sediments of South Carolina.
A variation in specimen size of included species was observed in several of the cores. This was especially pronounced near the top of the Coscinodiscus pllcatus/Delphlne/s penell/ptica Zone of the Cumberland Island core (-285 ft.). This could be associated with an increase in coastal upwelling intensity. Larger planktonic diatom specimens, which are generally favored by high upwelling velocities and greater associated productivity, provide a means to estimate past upwelling velocities and productivity. Furthermore, studies by Richert (1976) have shown that coastal upwelling with velocities of less than 2 m/day and without a continuous downwelling front are undetectable in sediments based on opal content (diatoms). Consequently, the decrease in specimen size observed may indicate reduced upwelling Intensity. Such occurrences, as in the Cumberland Island core, coincided with periods or cycles of diminishing deposition of diatomaceous sediments or, in the case with the 50 to 52 ft. and 99 to 102 ft. Intervals of W-13744, with isolated occurrences of sparse floral assemblages (figure 8).
Alternatively, the attractiveness of an offshore, cool-water current as a source of both upwelling diatom species and phosphorite cannot be dismissed. Upwelling genera such as Thalass/onema, Thalasslos/ra, and Dent/cula may have been brought in by cool-water currents. Such a current (Ancestral Labrador Current) has been postulated by Abbott and Andrews (1979). This current may be extended as far south as the study area if, as Abbott suggests, the Cape Fear Arch east of North Carolina was subdued during the Middle Miocene (figure 13).
An open Isthmus of Panama was a major influence on circulation patterns (especially in equatorial Atlantic waters). A flow of Pacific nutrient-rich waters through this opening would result in increased diatom production in areas near to these currents (Ramsey, 1971).
The noted absence of upwelling species in the Pliocene diatomaceous sediments present in the southern part of the study area may be related to the closing of the Isthmus of Panama during Pliocene times (Stokes, 1966). Such an event would have a dramatic effect on currents, especially in the Caribbean Sea region. The cessation of strong westward flowing ocean currents would divert increasing amounts of warm water northward. Consequently, the presence of the course of Abbott's postulated cool-water current and associated upwelling diatoms off the east coast of Florida may have ceased or moved considerably offshore or northward; the net effect being minimal or no influx of upwelling species. In summary, an open Isthmus permitting the flow of Pacific nutrient-rich waters into Atlantic waters and a subdued Cape Fear Arch were real or postu-




28 BUREAU OF GEOLOGY
lated factors present in the Miocene that were either missing or significantly changed by Pliocene time.
Pliocene Data
Dates obtained from the diatom flora for the "Hawthorn-like" sediments south of Brevard County were unexpected. These diatomaceous sediments, which were present in two cores from Indian River and St. Lucle counties, had diatoms of post-Miocene age (figure 8). If these sediments are assigned to the Hawthorn Formation, this would represent a significant age extension of the Hawthorn Formation based on flora from the northern cores and heretofore accepted dates (Alt, 1974; Weaver and Beck, 1977).
The Middle Miocene flora present in the northern part of the study area is not present in these cores. Explanations for this noted absence include: nondeposition of Hawthorn sediments in this area during the MidFlur 1M renth
__North ClKtorial curent
Figure 13. Major currents of the North Atlantic.




10.0
/."-s, BRACKISH SPECES
0
Z s.o **\ *' WARM WATER SPECES
O0 / --.o
CORE DEPTH (FEET, MUL) -58 Uine.o
o
Z 4.0
Io z
p
0 4
-as -40 -42 -44 -46 -48 -50 -52 -54 -54 -5
CORE DEPTH (FEET, MSL)
Figure 14. Distribution of diatoms in terms of brackish, upwelling, and warm water indicators and numbers of species for W-590&6




sos
-I r^" \ WARM WATER SPECIES
Sa / ms ******BRACKISH SPECIES
z Lk
0 c
oo
0
a- 5a
I." -n
Z 4.0 LU m
0'0
A" 6
-00 -110 IIS 1 -I -125 -130r -135 -140 *-145
CORE DEPTH (FEET, MSL)
Figure 15. Distribution of diatoms in terms of brackish, upwelling and warm water indicators and numbers of species for W-13958.




"ne"on" BRACKISH SPECIES
10. WARM WATER SPECIES
o v
0 21 &0 U6 1V an
I
4.0- -420
UI
0
w: z Ma z a. p
* *. e V. =
-- - '-
-40 -2o -280 -300 -320 -340 -3i0 -3i0 .400 -420
CORE DEPTH (FEET, MSL)
Figure 16. Distribution of diatoms in terms of brackish, upwelling, and warm water indicators ana numbers of species for the St. Lucie core.




32 BUREAU OF GEOLOGY
die Miocene, deposition of Hawthorn sediments and subsequent erosion, or strata of this age being represented by unfossiliferous sediments. Although the first two explanations cannot be ruled out as possible causes, the close similarity of these unfossiliferous sediments in lithology to the Middle Miocene sediments in the northern cores and thickness (hundreds of feet) are supportive of their presence as unfossilized sediments. In addition, the absence of a Middle Miocene assemblage in these southern cores may be the result of secondary dissolution or a depositional environment inhospitable to their presence. The presence of carbonate below the Pliocene age flora, which invariably occurs as dolomite (Scott, personal communication, 1981), does lend support to the theory of alteration of initial sediments, erasing all evidence of included microflora.
These younger Pliocene sediments were more calcareous than the Middle Miocene diatomaceous sediments, an observation in part attributed to an increase of calcareous nannoplankton and foraminifera. This was the primary difference observed in the lithology. Clay analyses done by Dabous in 1981 revealed the presence of sepiolite and palygorskite, common constituents of the Middle Miocene Hawthorn Formation, in addition to montmorillonite. Sepiolite and palygorskite have rare sporadic occurrences in sediments younger than the Miocene. Phosphorite content, which averaged a few percent, was similar in abundance to that found in the Miocene sediments to the north.
The formal classification of these sediments remains in question. The younger sediments may prove to be a new formation possessing many of the Hawthorn lithologic characteristics. However, Fogle (personal communication, 1981) identified the Hawthorn Formation in the St. Lucie core as occurring in the interval from 150 to 547 feet. This would place the Pliocene assemblage described in this study (- 282 to 387 ft.) well within the Hawthorn. Therefore, due to the extreme variability of the Hawthorn sediments and the similarity in mineralogy, phosphorite content, and relative difficulty in distinguishing between these sediments and the Miocene Hawthorn, the writer is inclined to treat these sediments as a facies of the Hawthorn Formation (Huddlestun and others, 1982, in press). Planned future drilling should more fully identify and delineate the areal extent of these sediments.
A distinctively different assemblage was present in the Pliocene sediments of the southern cores. Upwelling species, which were so numerous in the Middle Miocene diatomaceous sediments, were missing from these sediments. The resultant assemblage indicates an environment of temperate-to-warm temperatures and relatively shallow coastal depths.
This assemblage had occurrences in sediments of increased dolomitic composition in which the effects of solution were apparent. The Indian River core (W-13958) had several depths (- 112 ft., 122 ft., 130 ft.) in which species displayed varying degrees of dissolution (figure 15). Diatom species such as Paralia sulcata and Navicula pennata as well as calcareous Discoaster species displayed partially dissolved rims or edges.




REPORT OF INVESTIGATION NO. 93 33
Similar changes were observed in the St. Lucie core to the south.
The presence of extinct species, including Rhaphoneis fatula and Goniothecium odontella, which made their first appearance in the Pliocene and Late Miocene respectively, were present in these sediments. The latter species range from the Late Miocene to Early Pliocene. The presence of Thalassiosira oestrupi in these sediments is significant, since the first appearance of this brackish-water species is generally accepted as the base of the Pliocene. The co-occurrence of Discoaster brouweri and the silicoflagellate Distephanus boliviensis is rare in Pliocene sediments; the latter species was formerly thought to have reached extinction by the late Early Miocene. Of further significance was the presence of Bogorovia tatsunokuchiensis, a diatom common to the Pacific and believed to range from 2.9 to 4.9 million years before present (Abbott, personal communication, 1981). Consequently, an Early Pliocene date for these sediments is strongly supported by the included flora.
Pliocene diatom assemblages examined in the cores from Brevard County and southward exhibited no discernible trends in numbers of warm-water species (figures 14, 15,16). Maximum recorded occurrences in these cores varied from a 1.0 percent peak encountered in W-5906 to a 2.2 percent peak observed in W-13958 near the southern end of the study area. Distinct maxima and secondary maxima peaks were present in the Indian River (W-13958) and St. Lucie cores.
Minimum occurrences generally coincided with minimum numbers of species and brackish-water species, a finding suggestive of increased environmental stress. Prominent minimum occurrences, which approached zero, were recorded in both cores in intervals between the maximum abundances of brackish-water species mentioned above.
Numbers of Pliocene brackish-water species were similar to those found in the diatomaceous Middle Miocene Hawthorn sediments (figures 14, 15, 16). These species included the Pliocene forms Trachyneis aspera aspera and Hemidiscus ovalis, in addition to Rhaphoneis amphiceras, species also present in the Miocene.
Brackish-water species, which averaged less than four percent of the Pliocene assemblage, had maximum occurrences greater than six percent of the total assemblage in W-5906, W-13958, and the St. Lucie core. Brackish flora in the two southern cores (W-13958 and St. Lucie) each exhibit similar maximum abundances that were separated by an interval reflecting a sharp decline in numbers. The similarities in distribution of brackish and warm-water species, abundances, and numbers of total species versus depth are remarkably close. Specifically, the general coincidence of two major brackish and warm-water species peaks (W-13958,
-117 ft., -137 ft., and St. Lucie core, -312 ft., -342 ft.) and minima (W-13958, -125 ft. and St. Lucie core -332 ft.) are suggestive of a regressive-transgressive sequence on at least a local scale. In general, the flora denotes a shallow coastal or estuarine environment. This type of environment has a range of depths at which a relatively minor drop in sea level could dramatically affect the assemblage. This may be indicated




34 BUREAU OF GEOLOGY
by the occurrence of sparsely fossiliferous samples between two major peaks in both cores.
Species diversity is extremely variable throughout the Pliocene diatomaceous sediments. In general, diversity is less than that observed in the Miocene sediments to the north. The reduction in numbers of included species and absence of cool-water upwelling species are supportive of significant environmental changes during the Early Pliocene.
Diatom Molds
Diatom molds were found at various intervals in eight of the cores (figure 8). These cores were located at both coastal and inland sites (figure 7). In general, these molds were present in the middle or lower part of the Hawthorn section.
The explanation for these molds is probably a matter of time-related kinetics since the opal-A which forms the diatom frustules is inherently unstable. Alternatively, an increase in pH to values near 8 or 9 as a result of groundwater action could enhance the dissolution process (Abbott, personal communication. 1981).
The absence of both diatoms and molds in many of the cores could be attributed to a general incompatibility of diatoms at the time of the deposition to such environmental factors as water temperature, salinity, and/or a nutrients deficiency (especially nitrate and silica). Alternatively, their absence could be a function of selective solution both in the water column and in the sediments.
The occurrence of only centrales-type molds may not represent the past living assemblage (biocoenose). Studies in the equatorial Pacific (Burkle. 1977) have shown significant alteration of the diatom death assemblage (thanatocoenose) by selective dissolution in both the water column and the enclosing sediments. Molds of the centrales would tend to be preserved due to their generally larger and thicker valves. Conversely, the occurrence of these centric forms, which tend to dominate the planktonic species, may not have lived in situ. Diatoms, in particular planktonic species, are susceptible to lateral transport and may have been brought inland by currents to waters less conducive to plant growth resulting in their subsequent burial and post-depositional alteration.
Paralla sulcata
The abundance of the diatom species Paralla sulcata in both Middle Miocene and Pliocene sediments was notable. Indeed, this species was usually the dominant member of both prolific and impoverished assemblages alike. The dominance of this species may be as Abbott suggests (personal communication, 1979), a function of initial abundance at the time of sediment deposition. However, the type and appearance of specimens (resistant species, dissolution rims) and particularly the appearance and abundances of Paralia sulcata in sparsely fossiliferous intervals are suggestive of dissolution assemblages. Consequently, this species may have value as a dissolution indicator.




REPORT OF INVESTIGATION NO. 93 35
SUMMARY AND CONCLUSIONS
1. Cores drilled during the late 1970's along Florida's east coast by the Florida Bureau of Geology contain the most complete suite of Florida Hawthorn microfossiliferous sediments currently available for biostratigraphic analysis. Hawthorn sediments in the northern part of the study area range in age from Early Miocene to late Middle Miocene, while the southern part of the study area from Brevard County southward contains "Hawthorn-like" diatomaceous sediments of Early Pliocene age overlying the "typical" Hawthorn sediments.
2. A diversity of microfossil groups including 170 species of diatoms, 13 species of silicoflagellates, in addition to a number of planktonic and benthic foraminifera and several coccolith species, can be identified in the Hawthorn sediments. Diatoms represent the most definitive group in terms of both age resolution and environmental interpretation.
3. Three biostratigraphic zones of Middle Miocene to late Middle Miocene age can be recognized in the Hawthorn sediments of three cores and one set of well cuttings (Cumberland Island, W-670, W-13751, W-13844). A departure from Abbott's zonation involved the substitution of Rhaphoneis lancettulla for Coscinodiscus plicatus in the Coscinodiscus plcatus/Delph/nels penelliptica and Coscinodiscus plicatus zones in order to make the Florida Hawthorn zonation more adaptable to the observed flora.
4. Upwelling species occur with a predominant temperate-water flora in the northern cores. The upwelling flora, which is believed here to be the result of coastal upwelling or influx from a postulated offshore, cool-water current (Ancestral Labrador Current), reaches a maximum value of 26.0 percent of the total assemblage in core W-13751.
5. The total absence of an upwelling flora in the Pliocene "Hawthornlike" sediments of the southern half of the study area may be related to changes in the paleo-oceanographic environment by Pliocene time. These changes may include the closing of the Isthmus of Panama during the Early Pliocene, cessation of upwelling, or both.
6. Core W-13751, located in St. Johns County, has the longest diatomaceous section which includes the Middle Miocene Coscinodiscus picatus, Coscinodiscus plicatus/Delphinels penelliptica and Delphineis peneliptica zones. Sediments belonging to the Coscinodiscus plicatus/ Delphinels penellptica Zone appear to form a complete section, from which a sedimentation rate of 3.2 cm/1000 years has been calculated. Although this rate is higher than present deep-sea sedimentation rates (2 cm/1000 yrs.), it may be compared to shelf deposits which typically have higher sedimentation rates.
7. In general, species diversity was less in the Pliocene sediments than the Middle Miocene sediments, a reduction attributed in part to changes in the depositional environment, degree of dissolution, and other external influences.
8. Fluctuations in productivity, as expressed in terms of species diver-




36 BUREAU OF GEOLOGY
sity and numbers of brackish-water species in both Middle Miocene and Pliocene assemblages, are probably the result of sea level changes. The degree of similarity of these fluctuations are especially pronounced in the Pliocene sediments of W-13958 and the St. Lucle core, an Indication of a transgressive-regressive sequence in at least a local area.
9. The diatomaceous sediments that are here described from Indian River and St. Lucie counties, are tentatively designated as "Hawthornlike" sediments on the basis of lithologic similarities. If these sediments are assigned to the Hawthorn Formation, this represents a significant upward extension of the Hawthorn Formation's age of deposition in eastern Florida.
10. The presence of the diatom Delphlnels blserlata, a highly definitive index species in the Middle Miocene Coscinodiscus plicatus Zone, represents an extension of the previously accepted range for this species.
11. The presence of Melosira granulata, a fresh-water diatom, near the top of the Hawthorn Formation in W-13744 may represent a lowering of sea level associated with an extreme regressive cycle, or it may be attributed to influx from a nearby fresh-water source, such as a river.
12. The diatomaceous Hawthorn sediments in the study area are biostratigraphically equivalent to the lower part of the Choptank Formation and the top of the Calvert Formation of the Chesapeake Bay Area as well as part of the Pungo River Formation of North Carolina.
13.a The presence of the planktic foraminifera Globlgerina chipolensis (Oligocene to earliest Miocene) and Globlgerinoldes quadrilobatus primordius (Early Miocene) in sediments near the bottom of the Hawthorn Formation in W-13815 offers strong support for the initiation of Hawthorn sedimentation in the deeper basins of north Florida during the Early Miocene.
14. The co-occurrence of important Pliocene marker species representing several different microfossil groups (foraminifera Globorotalla margaritae; coccoliths, Discoaster broweri and Discoaster surculus; silicoflagellates Mesocena circulus, and the diatom Rhaphonels fatula) in sediments of core W-13958 is significant in that this represents a rare, if not the only, recorded co-occurrence of diverse microfossil groups of Pliocene age along the Atlantic east coast.,
15. The appearance and abundance of the diatom Paralla sulcata in sparsely fossiliferous sediments suggests its utilization as a dissolution indicator.




REPORT OF INVESTIGATION NO. 93 37
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,1974b, Miocene opal phytoliths and their climatic Implications:
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,1978, Correlation and zonation of Miocene units along the Atlantic margin of North America utilizing diatoms and silicoflagellates:
Marine Micropal., v. 31, no. 1, pp. 15-23.
, and Ernissee, J.J., 1977, Blostratigraphy and paleoecology of
a diatomaceous clay unit in the Miocene Pungo River Formation of
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, and Andrews, G.W., 1979, Middle Miocene marine diatoms
from the Hawthorn Formation within the Ridgeland Trough, South Carolina and Georgia: Micropal. v. 25, no. 3, pp. 225-271.
Andrews, G.W., 1975, Taxonomy and stratigraphic occurrence of the marine
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, 1979, Marine diatom sequence in Miocene strata of the Chesapeake Bay region, Maryland: Micropal., v. 24, no. 4, pp. 371-406. Applin, E.R. and Jordan, L., 1945, Diagnostic foraminifera from surface
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modern drainage, southeastern United States, in Oaks, R.Q., and Dunbar, J.R., 1974, Post-Miocene stratigraphy, central and southern Atlantic Coastal Plain: Logan: Utah State University Press, pp. 21-29. Bailey, J.W., 1841, A sketch of the infusoria of the family Baclaria which
have been found in recent or fossil state in the United States: Amer.
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,1844, Account of some new infusorial forms discovered in the
fossil infusoria from Petersburg, Va., and Piscatway, Md.: Amer. Jour.
Sci., v. 46, pp. 137-141.
Bishop, E.W., 1956, Geology and ground-water resources of Highlands
County, Florida: Fla. Geol. Survey Bull. 15, p. 115.
Blow, W.H., 1969, Late Middle Eocene to Recent planktonic foraminiferal blostratigraphy: International Conf. Planktonic Microfossils, 1st, Geneva, 1967, Proc., v. 1, pp. 199-422.
Burkle, L.H., 1972, Late Cenozoic planktonic diatom zones from the eastern equatorial Pacific: Nova Hedwigia, v. 39, pp. 217-246.
, 1977, Pliocene and Pleistocene diatom datum levels from the
equatorial Pacific: Quat. Res., 7, pp. 330-340.




38 BUREAU OF GEOLOGY
Burnett, W.C. and Veeh, H.H., 1977, Uranium-series disequilibrium studies in phosphorite nodules from the west coast of South America:
Geochim. et Cosmochim. Acta, v. 41, pp. 755-764.
Carr, W.J. and Alverson, D.C., 1959, Stratigraphy of Middle Tertiary rocks
in part of West-Central Florida: U.S. Geological Survey Bull. 1092, p.
11.
Cavallero, G., 1974, Diatom zonation in Miocene sediments from Maryland: Unpublished Masters thesis, Hunter College, New York, p. 98. Cooke, C.W., 1945, Geology of Florida: Fla. Geol. Survey Bull. 29, p. 339.
, and Mossom, S., 1929, Geology of Florida: Fla. Geol. Survey
Ann. Rpt. 20, pp. 115-137.
Dall, W.H. and Harris, G.D., 1982, Correlation Paper-Neogene: U.S. Geol.
Survey Bull. 84, pp. 107-113.
Ehrenberg, C.G., 1844, Uber 2 neue Lager von Gebirgsmassen aus Infusorien als Meeres-Alsatz in Nord-Amerika and Kreida-Gebilden in Europa and Afrika: Kgl. preuss. Akad. Wiss. Berlin, Ber., pp. 57-97.
,1854, Mikrogeologie des Erden and Felsen-Schaffende Wirken des unsichtbar kleinen selbstandigen Lebens auf der Erde: Leipzig, Leopold Vos.
Ernissee, J.J., 1976, Endoskeletal dinoflagellates from the Coosawhatchie
Clay, Jasper County, South Carolina: South Carolina State Dev. Bd.,
Div. Geology, Geologic Notes, v. 20, no. 3, pp. 88-100.
Gardner, J.A., 1926, The molluscan fauna of-the Alum Bluff Group of Florida: U.S. Geol. Survey Prof. Paper 142, p. 491.
Haass, L.D. and Schrader, H.J., 1979, Neogene coastal upwelling history
off Northwest and Southwest Africa: Marine Geology, v. 29, pp. 39-53. Hathaway, J.C., McFarlan, P.F. and Ross, D.A., 1970, Mineralogy and origin of sediments from drill holes on the continental margin off Florida:
U.S. Geol. Survey Prof. Paper 581-E, p. 26.
Huddlestun, RE, Abbott, W.H. and Hoenstine, R.W., 1982, The stratigraphic definition of the Lower Pliocene Indian River Beds of the Hawthorn in South Carolina, Georgia, and Florida (Abstract) in Miocene of the Southeastern United States, T. Scott and S. Upchurch, eds: Fla.
Bureau of Geology Special Publication 25, pp. 184-186.
Johnson, L.C., 1888, The structure of Florida: Amer. Jour. of Sci. 3rd, v. 36. Johnson, H.S. and Geyer, V.R., 1965, Phosphate and bentonite resources,
Coosawhatchie district, South Carolina: Unpublished Open-File Report, South Carolina State Dev. Bd., Div. Geology, p. 27.
Ketner, K.B. and McGreevy, L.J., 1959, Stratigraphy of the area between
Hernando and Hardee counties, Florida: Washington, U.S. Govt. Print
Off., pp. 49-124.
Leroy, R.A., 1981, The Mid-Tertiary to Recent lithostratigraphy of Putnam
County, Florida: Unpublished Masters thesis, Florida State University.




REPORT OF INVESTIGATION NO. 93 39
Lohman, K.E., 1938, Pliocene diatoms from the Kettleman Hills, California:
U.S. Geol. Survey Prof. Paper 189-C, pp. 81-102.
Manheim, F., Rowe, G.T. and Jipa, D., 1975, Marine phosphorite formation
off Peru: Jour. Sed. Petrology, v. 45, pp. 243-251.
Martini, E., 1971, Standard Tertiary and Quaternary calcareous nannoplankton zonation: Proc. II Planktonic Conf., Roma, 1970, v. 2, pp.
739-785.
, and Worsley, T., 1970, Standard Neogene calcareous nannoplankton zonation: Nature, v. 225, pp. 289-290.
Matson, G.C. and Clapp, F.G., 1909, A preliminary report on the geology
of Florida: Fla. Geol. Survey Ann. Rpt. 2, pp. 69-74.
Miller, J.A., 1978, Geologic and geophysical data from Osceola National
Forest, Florida: U.S. Geol. Survey Open-File Rept. 78-799, p. 101. Milliman, J.D., Summerhayes, C.P. and Barrette, H.T., 1975, Oceanography and suspended sediment off the Amazon River: Jour. Sed. Petrology, v. 45, pp. 189-206.
Odum, E.P., 1959, Fundamentals of ecology: Philadelphia, Sanders, p.
546.
Puri, H.S., 1953, Contribution to the study of the Miocene of the Florida
Panhandle: Fla. Geol. Survey Bull. 36, p. 345.
Ramsey, A.T.S., 1971, Occurrence of biogenic siliceous sediments in the
Atlantic Ocean: Nature, v. 233, pp. 115-117.
Reik, B.A., 1980, The Tertiary stratigraphy of Clay County, Florida, with emphasis on the Hawthorn Formation: Unpublished Masters thesis, Florida State University.
,1982, Clay mineralogy of the Hawthorn Formation in northern
and eastern Florida; in Miocene of the Southeastern United States, T.
Scott and S. Upchurch, eds., Fla. Bureau of Geology Special Publication 25, pp. 247-250.
Reynolds, W.R., 1962, The ithostratigraphy and clay mineralogy of the
Tampa-Hawthorn sequence of peninsular Florida: Unpublished Masters thesis, Florida State University, p. 126.
Richert, R, 1976, Relationship between diatoms biocoenoses and
taphrocoenoses in upwelling areas off West Africa: Abstracts 4th Symposium on Recent and Fossil Diatoms, Oslo.
Riggs, R.R., 1979a, Phosphorite sedimentation in Florida-a model phosphogenic system: Econ. Geology, v. 74, pp. 285-314.
,1979b, Petrology of the Tertiary phosphorite system of Florida:
Econ. Geology, v. 74, pp. 195-225.
Schrader, H.J., 1973, Cenozoic diatoms from the northeast Pacific, Leg 18: Initial Rept. Deep Sea Drilling Project, v. 17, pp. 673-797.
Scott, T.M., 1981, The Paleoextent of the Miocene Hawthorn Formation in Peninsular Florida, Florida Scientist, v. 44, suppl. 1, p. 42.




40 BUREAU OF GEOLOGY
Scott, T.M., 1982, A Comparison of the Cotype Localities and Cores of the
Miocene Hawthorn Formation in Florida; in Miocene of the Southeastern United States; T. Scott and S. Upchurch, eds.: Fla. Bureau
of Geology Special Publication 25, p. 237.
S1983, The Hawthorn Formation of Northeastern Florida: Fla.
Bureau of Geology Rpt. of Inv. 94.
Scott, T.M. and MacGill, RL., 1981, The Hawthorn Formation of Central
Florida: Fla. Bureau of Geology Rpt. of Inv. 91, p. 107.
Sellards, E.H., 1916, Fossil vertebrates from Florida; a new Miocene fauna;
new Pllocene species; the Pleistocene fauna: Fla. Geol. Survey Ann.
Rpt. 8, pp. 77-119.
Smith, R.L., 1968, Upwelling: Oceanogr. Mar. Blo. Ann. Rev., v. 6, pp.
11-4&6.
Summerhayes, C.RP., 1970, Phosphatic deposits on the northwest Africa
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282.
Sverdrup, H.U., Johnson, M.W. and Fleming, R.H., The Oceans: PrenticeHall, Inc., p. 36.
Taylor, CB. and Stewart, H.B., 1959, Summer upwelling along the east
coast of Florida: J. of Geophys. Res., v. 64, pp. 33-40.
Twiss, P.C., Suess, E. and Smith, R.M., 1969, Morphological classification
of grass phytoliths: Soil Scl. Soc. America Proc., v. 33, pp. 109-115. Vaughan, T.W. and Cooke, C.W., 1914, Correlation of the Hawthorn Formation: Wash. Acad. Scl. Jour., v. 4, no. 10.
Vernon, R.O., 1951, Geology of Citrus and Levy counties, Florida: Fla.
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Weaver, C.E. and Beck, K.C., 1977, Miocene of the Southeastern United
States: A model for chemical sedimentation in a perimarine environment: Sediment, Geol., 17(l/), p. 234.
Wells, H.W. and Gray, I.E., 1960, Summer upwelling off the northeast
coast of North Carolina: Limnol. Oceanogr., v. 5, pp. 108-109.
Wilson, W.E., 1977, Simulated changes in ground-water levels resulting
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Wise, S.W. and Weaver, F.M., 1973, Origin of cristobalite-rich Tertiary
sediments in the Atlantic and Gulf Coastal Plain: Gulf Coast Assoc.
Geol. Trans., v. 23, pp. 304-323.




REPORT OF INVESTIGATION NO. 93 41
PLATES 1-13




42 BUREAU OF GEOLOGY
PLATE 1
Diatom photomicrographs; 400X Figure 1 Actinocyclus octonarius (Ehrenberg)
diameter 40 to 114 pm
Figure 2 Actinocyclus ingens (Rattray)
diameter 22 to 39 pm
Figure 3 Actinocyclus ellipticus (Grunow)
length 20 to 79 pm




,REPORT OF INVESTIGATION NO. 93 43
1
3
2
PLATE 1




44 BUREAU OF GEOLOGY
PLATE 2
Diatom photomicrographs; 400X
Figure 1 Actinoptychus senarius (Ehrenberg) Ehrenberg
diameter 22 to 77 pm
Figure 2 Actinoptychus clevei (Schmidt)
diameter 33 to 83 pm
Figure 3 Actinoptychus aff. A. minutus (Greville)
diameter 29 to 44 pm
Figure 4 Biddulphia rhombus (Ehrenberg) Smith
length 54 to 105 pm




REPORT OF INVESTIGATION NO. 93 45
312
4
PLATE 2




46 BUREAU OF GEOLOGY
PLATE 3
Diatom photomicrographs; 400X Figure 1 Biddulphia tuomeyi (J. W. Bailey) Roper
length 42 to 123 pm
Figure 2 Biddulphia reticulum (Ehrenberg) Boyer
length 35 to 95 pm




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ww
A~~4w 4 A%




48 BUREAU OF GEOLOGY
PLATE 4
Diatom photomicrographs; 400X
Figure 1 Coscinodiscus apiculatus (Ehrenberg)
diameter 74 to 117 pm
Figure 2 Coscinodiscus vetustissimus (Pantocsek)
diameter 58 to 67 pm
Figure 3 Coscinodiscus lewisianus (Greville)
length 30 to 106 pm, width about 2/5 of length in larger
specimens




REPORT OF INVESTIGATION NO. 93 49
1r
I~i~ji
JI
2 3
PLATE 4




50 BUREAU OF GEOLOGY
PLATE 5
Diatom photomicrographs; 400X Figure 1 Coscinodiscus perforatus (Ehrenberg)
diameter 57 to 102 pm
Figure 2 Coscinodiscus asteromphalus (Ehrenberg)
diameter 59 to 198 pm




REPORT OF INVESTIGATION NO. 93 51
1A
2
PLATE 5




52 BUREAU OF GEOLOGY
PLATE 6
Diatom photomicrographs; 400X
Figure 1 Cussia praepaleacea (Schrader) Schrader
diameter 30 to 55 pm, width 7 to 9 pm
Figure 2, 3 Cymatogonia amblyoceras (Ehrenberg.Hanna
length 35 to 55 pm .




REPORT OF INVESTIGATION NO. 93 53
PLATE 6 4 s:4sA.
U .
3
PLATE 6




54 BUREAU OF GEOLOGY
PLATE 7
Diatom photomicrographs; 400X Figure 1 Delphineis penelliptica (Andrews)
length 28 to 82 pm, width 10 to 12 um
Figure 2 Delphineis angustata (Pantocsek) Andrews
length 31 to 50 pm, width 7 to 8 pm Figure 3 Delphineis surirella (Ehrenberg)
length 15 to 46 pm
Figure 4 Delphineis biseriata (Grunow) Andrews
length 40 to 64 pm, width 6 to 9 pm Figure 5 Diploneis smithi (Brebisson) Cleve
length 50 to 77 pm
Figure 6 Diploneis bombus (Ehrenberg) Cleve
length 30 to 46 pm




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56 BUREAU OF GEOLOGY
PLATE 8
Diatom photomicrographs; 400x Figure 1 Navicula cf. N. directa (Wm. Smith) Ralfs in Pritchard
length 53 to 77 pm, width 12 to 15 pm Figure 2 Navicula pennata (Schmidt)
length 56 to 78 pm, width 13 to 18 pm Figure 3 Navicula hennedyi (W. Smith)
length 48 to 58 Im, width 23 to 40 pm




REPORT OF INVESTIGATION NO. 93 57
.2
irr
3
PLATE 8




58 BUREAU OF GEOLOGY PLATE 9
Diatom photomicrographs; 400X Figure 1, 2 Paralia sulcata (Ehrenberg) Cleve
diameter 26 to 40 pm
Figure 3 Melosira westii (W. Smith)
diameter 16 to 30 pm
Figure 4 Podosira cf. R stelliger (Bailey) Mann
diameter 31 to 62 pm




REPORT OF INVESTIGATION NO. 93 59
11
2
nPLE 4
.PLATE 9




60 BUREAU OF GEOLOGY
PLATE 10
Diatom photomicrographs; 400X Figure 1 Rhaphoneis amphiceras (Ehrenberg) Ehrenberg
length 29 to 100 pm, width 18 to 25 pm Figure 2 Raphoneis fatula (Lohman)
length 33 to 46 pm
Figure 3 Rhaphoneis gemmifera (Ehrenberg)
length 28 to 115 pm, width 15 to 20 pm Figure 4 Rhaphoneis cf. R. angularis (Lohman)
length 50 to 150 pm, width 17 to 21 pm Figure 5 Rhaphoneis lancetulla (Grunow)
length 38 to 114 pm, width 7 to 10 pm Figure 6 Rhaphoneis adamantea (Andrews)
length 36 to 80 pm, width 20 to 30 pm




1a;
0.~
**gs.
164'




62 BUREAU OF GEOLOGY
PLATE 11
Diatom photomicrographs; 400X Figure 1 Triceratium reticulum (Ehrenberg)
length of side 30 to 62 pm
Figure 2 Triceratium condecorum (Ehrenberg)
length of side 40 to 82 pm Figure 3 Triceratium spinosum (Bailey)
length of side 42 to 75 pm




REPORT OF INVESTIGATION NO. 93 63 e- -... ~ O 1
o o
2
PAEA
0-LATE' 11
PLATE 11




64 BUREAU OF GEOLOGY
PLATE 12
Diatom photomicrographs; 400X
Figure 1 Xanthiopyxis sp. (Ehrenberg)
length is generally less than 50 pm
Figure 2 Thalassiothrix longissima (Cleve and Grunow)
length of whole specimens unknown but fragments
observed reached a length of 175 pm, width 3 to 4 pm
Figure 3 Trachyneis aspera (Ehrenberg) Cleve var. aspera
length 44 to 180 pm, width 13 to 17 pm
Figure 4 Thalassionema nitzschoides (Grunow) Hustedt
length 30 to 126 pm, width 4 to 5 pm
Figure 5 Fragilara sp. (Lyngbye)
length 28 to 117 pm, width 3 to 4 pm




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II=
.#.9
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66 BUREAU OF GEOLOGY
PLATE 13
Silicoflagellate photomicrographs; 400X Figure 1 Distephanus stauracanthus (Ehrenberg) Figure 2 Mesocena circulus (Ehrenberg) Figure 3 Distephanus crux (Ehrenberg) Figure 4 Dictyocha rhombica (Ehrenberg) Figure 5 Distephanus cf. D. boliviensis (Frenguelli)




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xml record header identifier oai:www.uflib.ufl.edu.ufdc:UF0000128000001datestamp 2008-12-01setSpec [UFDC_OAI_SET]metadata oai_dc:dc xmlns:oai_dc http:www.openarchives.orgOAI2.0oai_dc xmlns:dc http:purl.orgdcelements1.1 xmlns:xsi http:www.w3.org2001XMLSchema-instance xsi:schemaLocation http:www.openarchives.orgOAI2.0oai_dc.xsd dc:title Biostratigraphy of selected cores of the Hawthorn formation in northeast and east-central FloridaFGS: Report of investigation 93dc:creator Hoenstine, Ronald W.dc:publisher U. S. Geological SurveyBureau of Geology, Florida Department of Natural Resourcesdc:date 1984dc:type Bookdc:identifier http://www.uflib.ufl.edu/ufdc/?b=UF00001280&v=00001000985852 (aleph)AAA0719 (ltqf)AEW2268 (ltuf)dc:source University of Florida