The Lithostratigraphy of Nassau County in relation to the superconducting supercollider site investigation ( FGS: Open file report 15 )

FLRD GEOLOSk ( IC SUfRiW

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Tom Gardner, Executive Director

Division of Resource Management
Jeremy Craft, Director

Florida Geological Survey
Walt Schmidt, State Geologist and Chief

Open File Report 15

The Lithostratigraphy of Nassau County in Relation
to the Superconducting Supercollider Site Investigation

by

Thomas M. Scott

Florida Geological Survey
Tallahassee, Florida
1987

3 1262 04543 6259

LIBRARY

THE LITHOSTRATIGRAPHY OF NASSAU COUNTY IN RELATION
TO THE SUPERCONDUCTING SUPERCOLLIDER SITE INVESTIGATION

.BY

Thomas M. Scott
Florida Geological Survey

OPEN FILE REPORT NO. 15

1987

The Lithostratigraphy of Nassau County in Relation to the
Superconducting Supercollider Site Investigation

INTRODUCTION

The State of Florida is currently conducting the initial site investi-

gation in Nassau County for the proposed superconducting supercollider.

Geologic parameters played a key role in the selection of several sites

throughout the State. The final selection was made based on geological,

environmental and socioeconomic factors with Nassau County being judged the

most favorable location (Figure 1).

The Florida Geological Survey provided the initial site proposals

based on the geological data available from Survey publications, personnel

and files. The Nassau County site was included based upon the occurrence

of a thick confining section above the Floridan aquifer system, the lack of

potentially cavernous carbonates within the confining beds, and the exis-

tence of a surficial or shallow aquifer system that produces relatively

limited quantities of water. The current Nassau County data base on file

at the Florida Geological Survey is limited to lithologic samples from 30

wells (including 2 cores) and geophysical logs of 21 wells. These are

listed in the appendicies.

STRUCTURE

Nassau County, the northeastern most county in Florida, lies on the

northern and northwestern flank of the Jacksonville Basin of the Southeast

Georgia Embayment (Figure 2). The Jacksonville Basin represents a localized

thickening of the stratigraphic section within the Southeast Georgia Embay-

ment. Figure 1 indicates the relationship of the Nassau County area to the

other major structural features in Florida.

1 __

I / I

*-A-

-- -L

- U, -

-I

Study area and location of cross-section

Figure 1

I____ __________
_~_

0

JACKSONVILLE

NASSAU NOSE

N

0 50 100 MILES

SCALE

"p,,,~~

Structures affecting the Hawthorn Group

Figure 2

No faults have been recognized or postulated to occur in the county.

Leve (1966.) and Fairchild (1977) suggested the existence of faults in Duval

County. If these faults exist, they do not appear to have cut through the

Hawthorn Group sediments indicating that they have not been active since at

least the late Middle Miocene.

Topography and Geomorphology

The topography of the Nassau County area characteristically consists

of higher elevations with greater relief in the western one third of the

county and lower elevations and little relief in the remaining area. The

western area has elevations of as much as 107 feet above MSL near Boulogne;

however, the average elevation in this area ranges from 70 to 80 feet above

MSL. The lowlands surrounding the St. Marys River, generally the lowest

points in the area, range in elevation from near 50 feet above MSL in the

southwest to less than 5 feet above MSL along the northern boundary of the

county. The eastern two-thirds of the county average less than 25 feet

above MSL with the lowlands generally below 10 feet above MSL.

The topographic quadrangles covering Nassau County include, from west

to east: Folkston, Boulogne, Kings Ferry, Kingsland, Toledo, Hillard,

Hillard NE, Gross, St. Marys, Fernandina Beach, St. George, Hillard SW,

Callahan, Italia, Hedges, Amelia City, McClenny NE, Bryceville, and

Dinsmore.

Nassau County lies in the Northern or Proximal Zone of White (1970).

The high areas of the western part of the county are part of the Duval Up-

lands. Most of the remainder of the county falls in the St. Marys Meander

Plain. The east coast of Nassau County, the "Sea Islands", are part of the

Atlantic Beach Ridges and Barrier Chain (Figure 3).

*-J

ST. MARYS RIVER

DUVAL UPLAND

GEORGIA

S ATLANTIC OCEAN

ST. MARS MEANDER PLAIN

SCALE
0 5 10 15 20 25 Mi

0 8 16 24- 32 40Km

Geomorphology of Nassau County
*

GEORGIA

Figure 3

LITHOSTRATIGRAPHY

Thin lithostratigraphic discussion of the supercollider site in Nassau

County is limited to the carbonates of the upper part of the underlying

Floridan aquifer system, the mixed carbonates and siliciclastics of the

intermediate confining system and the sediments of the surficial or shallow

aquifer system. This includes the Upper Eocene Ocala Group, the Miocene

Hawthorn Group, the Pliocene Nashua Formation, and the undifferentiated

Plio-Pleistocene and Holocene sediments (Figure 4). Total thickness of

these sediments ranges from 400 to 500 feet within the county. Construc-

tion of the proposed supercollider will most likely occur in the upper 150

feet of this section within the Hawthorn Group.

Ocala Group

The Ocala Group consists of very pure limestones with limited occur-

rences of thin dolostone near the base of the group. The limestones are

characteristically calcarenitic with varying amounts of carbonate mud in

the matrix (grainstone to packstone). The grains are composed of fossil

fragments, foraminifera, and biogenic debris. The limestones are generally

tan or very light brown to white and range from soft, poorly consolidated

to hard, well indurated and recrystallized. The dolostones are hard, gene-

rally well indurated, gray to moderate brown and crystalline.

The Ocala Group occurs throughout the county at elevations ranging

from approximately 400 feet below mean sea level (MSL) in the western por-

tion to greater than 500 feet below MSL along the east coast, dipping in a

general west to east direction (Leve, 1966) (Figure 4). The thickness of

the Ocala Group in this area ranges from approximately 350 feet to greater

than 500 feet, thickening from west to east (Leve, 1966). Cooke (1945),

Vernon (1951), Herrick and Vorhis (1963), Purl land Vernon (1964) and
Stringfield (1966) provide more information on the Ocala Group. Therela-
Stringfield (1966) provide more information on the Ocala Group. The rela-

Figure 4 Lithostratigraphic units of the Hawthorn Group
in north Florida

tionship of the Ocala Group to the overlying sediments can be seen in

Figures 6 and 7.

The carbonates of the Ocala Group are part of the upper Floridan aqui-

fer system and are capable of producing vast quantities of water. Leve

(1966) indicates flow rates measured in zones of the Ocala Group often ex-

ceeded 3,000 gallons per minute. The sediments of the Floridan aquifer

system will not be encountered during the construction of the supercollider.

The construction activity will be separated from the Floridan aquifer sys-

tem by as much as 300 feet of low permeability to relatively impermeable

sediments of the Hawthorn Group.

Hawthorn Group

The Hawthorn Group sediments represent a dramatic deoositional change

from the carbonates of the Eocene (Oligocene is absent) to the siliciclas-

tic dominated section in the Miocene. The Miocene sediments exhibit tre-

mendous variability both laterally and vertically. In a general sense, the

Hawthorn sediments contain more carbonate beds in the lower portion of the

section. Carbonates decrease in abundance higher in the section. Research

by Scott (1987) in Florida and Huddlestun (1987) in Georgia provides the

lithologic framework and formational breakdown of the Hawthorn Group in

this area. In ascending order the formations include: the Penney

Farms/Parachucla Formations, the Marks Head Formation and the Coosawhatchie

Formation including the Charlton Member (Figure 4). These units are

recognized in cores (Figure 7). However, in well cuttings it is difficult

to separate the units due to the loss of fine grained sediments and the

inclusion of material caving from above. If enough core control is

available, cuttings can be utilized in a detailed study. The data pre-

I EXPLANATlON

-25- Z ,lou -er- 25 Feet
Lfl''t C! N3,Unrn Fm
Fooryt fdoed .?,e ferrej,
Wells
G E 0 R i A 0r7cos

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.33- 5 .7 .~ .....
-a
Is

-U -350 -3, '0-~j~,
0
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-325
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0.~
~-250

ED.
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f 04s-5
srlc'7 _,7~

IT C

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Figure 5
*

Top of Ocala Group in.Northeast Florida

Lan
-l r~51*C*3 .53r( C .% *5I

Cross section C-C' (see figure 1 for location)
(See Scott (1983) for discussion of faults)

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OCALs. 0*0.

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Figure 6

W-13I 15

CLRY
HfNVTY HIMS.
"SHY, TN,1H.

*UNDIFFERENTIATED

-180

-190

-200

-210

-220

-230 -

Jll7'

O.....-

~i^
.* 7. ... 7

S HAWTHORN GROUP
SRNO

CALCT CHARLTON MEMBER
CALCITE

PHOSPHATE DilOiilE
PHOSPHATE OOLCOITE
PHOSPHATE COLONTTE
PHOSPHATE
PHOSPHATE
PHOS PATE
PHOSPHATE
PHOSPHATE
PHOSPHATE
PHOSPHATE
PHOSPHATE
PHOSPHATE
PHOSPHATE
PHOSPHT11
PHOSPHATE
PHOSPHATE
PHOSPHATE
PHOSPHAIE
PHOSPHATE

PHOSPHATE SA
PHOSPHATE SO
PHOSPHATE
PHOSPHATE
PHOSPHATE
PHOSPHATE
PHOSPHATE
PHSPHATE
PHOSPHATE
PHOSPHATE
PHOSPHATE
PHOSPHATE A
SE0H tOLMOITE
PHOSPHATE DOLOMITE
PHOSPHATE OOLOMAIE

PHOSPHATE OOLOMIT6
PHOSPHATE DOLOMITE
OOLOHITE CLTA

-280 -

-290 -

-300

-310 -

-320

-330

-30 -

-350

-360 _

-370 _

-380. -

-390

-400 _

-410 -

SANO CLRY
OOLONITE

PHOSPHATE DOLOAITE
PHOSPHATE DOLOMITE
PHOSPHATE COLOSIIE
PHOSPHATE OOLOLIE E
_e=.U.TCr MIK.IIC

-420 -

PHOSPHATE

Z
0

c-

PHOSPHATE 00CLOITE
PHOSPHATE
PHOSPHATE SR
PHOSPHATE S
PHOSPHATE SRAO
PHOSPHATE SAND 0)
PHOSPHATE SANO
PHOSPHAIE SANO ODLOIITE Y
PHOSPHATE 0LOAHITE CLAY
PHOSPHRIE CLRY 4
PHOSPHATE CLRAY
PHOSPHATE
PHOSPATIE

imne*Pnllc FCcI

-. -- -- --
/ /
y- -^ ^
1[-4-4-4-4

[- C
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-. -...

:-.
., .. ..

.7 z

.... ,-..-. -... ..-. '
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= 4

/ / /
/ / /; /

PHOSPHATE
PHOSPHATE
PHOSPHATE
PHOSPHATE
PHOSPHATE
PHOSPHATE
PHOSPHATE
PHOSPHATE
SILT PHOSPHATE SANH
PHOSPHATE
PHOSPHATE
PHOSPHATE CLAY
PHOSPHATE
SHND CLAY
CLAY
CLAY
PHOSPHATE
CLAY
PHOSPHATE
PHOSPHATE
PHOSPHATE
PHOSPHATE
PHOSPHATE
PHOSPHATE
PHOSPHATE CLAY
PHOSPHATE
PHOSPHATE CLRAY
PHOSPHATE
PHOSPHATE
PHOSPHATE CLAY
PHOSPHRAE SRND
PHOSPHATE SADO
PHOSPHATE SAND
PHOSPHATE SAIND
CLAY
CLAY
CLAY
CLAY

CLRI
SAHO
SANO
CRLCITE CLAY
CLAY
CLRAY
SANO CLARY

SA CLA' HAWTHORN GROUP
SPAS

OCALA GROUP

CRYSTAL RIVER FORMATION

Reference core for the Charlton Member of the

Coosawhatchie Formation, Cassidy #1, Nassau

County (Lithologic legend Appendix B)

..

..-* -*-*.*-*
.-*y-*/-*,--7
.. <. .7. ..
-_ -

-50

-60

-70

-80

-90

-100

-110

-120

-130

-150 _

-170 -

-176-

z
0
r-

c4

LU

z
z
I

Figure 7

-250 -

CLAY

-

sented below on the formations of the Hawthorn Group is excerpted from

Scott (1987) with only minor changes.

Penney Farms/Parachucla Formation

The Penney Farms Formation, introduced by Scott (1987), occurs through-

out much of northern Florida as a subsurface unit (Figures 3 and 4). It is

the lateral equivalent of the Parachucla Formation in southeastern Georgia

as defined by Huddlestun (1987). The faces transition between the Penney

Farms and the Parachucla occurs in northern Nassau County and into Charlton

and Camden counties, Georgia. As a result, cores taken in Nassau County

may contain either Penney Farms or Parachucla. The primary difference be-

tween the two units is the amount of carbonate present as discreet beds,

with the Penney Farms containing more carbonate.

The carbonates are variably quartz sandy, phosphatic, clayey dolo-

stones. Sand content is variable to the point that the sediment may become

a dolomitic sand. Phosphate grains may comprise twenty-five (25) percent

or more with an average of approximately five (5) to ten (10) percent.

Clay percentages are generally minor [below five (5) percent] but often

increase in the dolostones of the upper portion of the formation. The

dolostones are medium gray to pale yellowish brown. They are generally

moderately to well indurated and finely to coarsely crystalline in the

lower part. The dolostones of the upper portion are generally less indu-

rated. Thicker, more massive beds predominate in the lower zone while

thinner beds are most common in the upper section. Mollusk molds are

common in the dolostones, particularly in the more coarsely crystalline

type.

Zones of intraclasts are common in the hard, finer grained dolostones

of the lower part of the Penney Farms. The intraclasts are composed of

dolostone that is essentially the same as the enclosing matrix. The

intraclasts are recognizable due to a rim of phosphate replacement along

the edges of the clasts. Edges of the clasts vary from angular to sub-

rounded indicating very little to no transport of the fragments. They also
may be bored, indicating at.least a semi-lithified state prior to being re-

deposited.

Limestone, in the basal portion of the Penney Farms Formation, occurs

sporadically. When it does occur, it is generally dolomitic, quartz sandy

and phosphatic.

The quartz sands are fine to coarse grained, moderately to poorly

sorted, variably phosphatic, dolomitic, silty and clayey. The phosphate

grain content varies considerably, sometimes to the point of being classi-

fied as phosphorite sand [fifty (50) percent or greater phosphate grains].

In general, however, the phosphate grain content averages between five (5)

and ten (10) percent. The sands are typically olive gray or grayish olive

to medium light gray. Clay content varies considerably in the sands.

Clay beds in the Penney Farms Formation are typically quartz sandy,

phosphatic, silty and dolomitic. The proportions of the accessory minerals

vary from nearly zero to more than fifty (50) percent. Nearly pure clay

beds are uncommon. Dolomite is very common in the clays, often being the

most abundant accessory mineral. Olive gray and grayish olive green

colors generally predominate, but colors may range into the lighter shades.

Smectite typically dominates the clay mineralogy of this unit, with paly-

gorskite, illite and sepiolite also present. X-ray analyses by Hetrick and

Friddell (1984) indicate that palygorskite may become predominant over

smectite in some samples. Reik (1982) indicated that palygorskite domina-

tes in the lower part of the Penney Farms while smectite dominated in the

upper portion in Clay County. Other minor mineralogic constituents include

mica, K-feldspar and opal-ct. Clinoptilolite has been identified ih a few

sample es.

When abundant silt-sized, unconsolidated dolomite occurs, difficulty

arises in.determining whether the actual rock type is a very dolomitic clay

or a very clayey dolostone. Insoluble residue analysis is the only accu-.

rate method of determining the clay and dolostone contents. Rough analysis

indicates that, in general, the lighter the color of the sediment, -the

higher the dolomite content. This method was employed'for determining the

sediment type in these situations.

The plastic beds of the Penney Farms Formation are lithologicaly very

similar to those in the Parachucla Formation in southeastern Georgia

(Huddlestun, 1987). As the Penney Farms Formation begins to lose its

carbonate units northward and northwestward into Georgia, the characteris-

tic lithologies are no longer apparent and the formation can no longer be

identified as the Penney Farms. These sediments in Georgia are included in

the Parachucla Formation (Huddlestun, 1987).

The Penney Farms Formation unconformably overlies limestones of the

Upper Eocene Ocala Group in Nassau County. The unconformity is very appa-

rent due to the drastically different lithologies of a pure limestone below

to a sandy, phosphatic dolostone or dolomitic, clayey phosphatic sand

above. The Marks Head Formation unconformably overlies the Penney Farms

Formation throughout Nassau County.

The overlying Marks Head Formation consists of interbedded fuller's

earth type clays, sands and dolostones which are generally lighter colored

than the sediments of the Penney Farms. The top of the Penney Farms is

placed at the break between the lighter colored sediments of the Marks Head

and the darker colored sands and clays of the upper part of the Penney

I I

Farms.' Occasionally, a rubble zone marks the break between the Marks Head

and the Penney Farms formations. When it occurs, the rubble consists of

clasts of phosphatized carbonate. The relationship of the Penney Farms

Formation to the underlying and overlying sediments can be seen in the

cross section (Figures 5 and 6).

The Penney Farms Formation of the Hawthorn Group occurs as a subsur-

face unit in Nassau County. The top of the Penney Farms Formation ranges

in cores from -333 feet MSL in Carter #1, W-14619, Duval County to +80 feet

MSL in Devils Millhopper #1, W-14641, Alachua County. In Nassau County,

the top of the Penney Farms Formation occurs at approximately -250 feet MSL

in the northwestern area to an estimated -350 feet MSL in the southeastern

to eastern area (Figure 8). The Penney Farms Formation dips in a general

easterly to southeasterly direction in Nassau County toward the Jacksonville

Basin with an average dip of 4 feet per mile. Locally, both the direction

and angle of dip may vary.

The Penney Farms Formation varies in thickness from zero on the crests

of the Ocala Platform and Sanford High (Figure 2) to more than 155 feet in

Carter #1, W-14619, Duval County in the Jacksonville Basin (Figure 2). The

total thickness of this unit was not determined in this core as the core

terminated in the Penney Farms Formation after penetrating 155 feet. This

author estimates that the base of the Penney Farms should occur near.-575

feet MSL based on nearby water wells. This suggests that approximately 230

feet of the unit should be present in the deepest portion of the Jackson-

ville Basin. The observed thickness of the Penney Farms in Cassidy #1,

W-13815, Nassau County is 150 feet (Figure 9).

The Hawthorn Group sediments of northern Florida yield very few

datable fossils or fossil assemblages. Diagenetic overprinting on the

-r-----

A iC. T
%%

C. Y
7 Cj

-4-
5 ----FE-T--

S C A L E N s o ,| IT -I -

S0o RIOMETERS

LEGEND
coMIS
CutIohGS
~J UMITSl Of HAWTHORN GROUP

Figure 8

Top of Penney Farms Formation (shaded area
indicates undifferentiated Hawthorn Group)

fV-r-- -l---- ---'i "1--

..~,

50 175
+- -- .. .

oi- r A100

LC a ST i A o
*" J L ._ 75

I OF I ~ '-j-- A--, -- -i
DIC I

LEGEND
SCUTTINGSt
Lii E V

1 01L O HAT SHOR AGO

S I OOUGH I T US

Figure 9 Isopach of Penney Farms Formation (shaded
area indicates undifferentiated Hawthorn Group)

sediments has obliterated the vast majority of fossils leaving mainly molds

and casts. Diatom and mollusk molds are the most frequently encountered

fossil remains. Nt the present time, a date has been obtained from the

Cassidy 1 core, W-13815, Nassau County in the interval from -370 to -375
MSL. The sediment, a calcareous, quartz sandy clay, contained benthic and

planktonic foraminifera, ostracods, spicules (sponge?-), echinoid fragments

and hryozoans. The planktonicc foraminifera indicate an Aquitanian, upper

Zone .4 or lower M.S.of Blow (1969)) for this interval (Huddlestun, per-

sonal communication, 1983).
The Penney Farms Formation of the Hawthorn Group is older than the

commonly accepted age for the Hawthorn Formation as described by Purl and

Vernon (1964). Purl and Vernon used a Middle Miocene age only for their

Hawthorn Formation. This has been the accepted age for the Hawthorn Forma-

tion by the Florida Geological Survey for sometime. Armstrong and Wise

(1985) suggested a latest Oligocene age for the base of the Hawthorn in

southeastern Florida. The data presented here indicate this should further

be revised.
The carbonate section of the Penney Farms Formation has often been

referred to as the basal Hawthorn dolostone in northern Florida. The

gamma-ray signature is quite distinctive, consisting of a number of very

high counts per second (cps) peaks (see section on gamma ray logs).

Marks Head Formation

Huddlestun (1987) reintroduced the Marks Head Formation in Georgia and

included it as part of the Hawthorn Group. The Marks Head Formation is

extended into northern Florida as the middle unit of the Hawthorn Group.

The lithologic similarities between the Marks Head Formation in southeast

Georgia and in north Florida warrants the use of the same nomenclature.

The Marks Head Formation in Florida consists of interbedded sands,

clays and dolostones throughout its extent. Carbonate beds are more common

in the Marks Head Formation in Florida than in Georgia; the proportion of

carbonate, both as a rock type and an accessory (matrix) mineral, gradually

increases into Florida. This unit is the most lithologically variable for-

mation of the Hawthorn Group in north Florida. Miller (1978) defined his

Unit 0 (equivalent to the Marks Head Formation) in the Osceola National

Forest in Columbia and Baker counties, Florida as being "complexly inter-

bedded shell limestone, clay, clayey sand and fine grained sandstone."

The carbonate portion of the Marks Head Formation is typically dolo-

stone; limestone is uncommon but does occur sporadically as is the case

throughout the Hawthorn Group. The Marks Head dolostones are generally

quartz sandy, phosphatic and clayey. The dolostones vary in induration

from poorly consolidated to well indurated. The induration varies in

inverse relationship to the amount of clay present within the sediment.

Phosphate grains normally comprise up to five (5) percent; however occa-

sional beds may contain significantly higher percentages. Quartz sand con-

tent varies from less than 5 percent to greater than 50 percent where it

grades into a dolomite cemented quartz sand. The dolostones range from

yellowish gray to olive gray in color. Crystallinity varies from micro-to

very finely crystalline with occasional more coarsely crystalline zones.

Molds of mollusk shells are often present.

The occurrence of limestone within the Marks Head Formation in Florida

is quite rare. The majority of the "limestone" reported from this part of

the section by other workers is actually dolostone. The limestone that

does occur is characteristically dolomitic, quartz sandy, phosphatic,

clayey, and fine grained.

I R

The quartz sands from the Marks Head Formation are generally fine to

nediumi grained (occasionally coarse grained), dolomitic, silty, clayey and

phosphatic. The dolomite, silt and clay contents are highly variable and

gradational with the other lithologies. Phosphate grains are usually pre-

sent in amounts ranging from one (1) to five (5) percent; however, phos-

phate percentages may range considerably higher in thin and localized beds.

The quartz sands are typically light gray to olive gray in color. Indu-

ration varies from .poor .to moderate.

Clay beds are quite common in the Marks Head Formation, occasionally

comprising a large portion of the section. The clays are quartz sandy,

silty, dolomitic and phosphatic. As is the case in the underlying Penney

Farms Formation, the Marks Head clays contain highly variable percentages

of accessory minerals; relatively pure clays do occur but are not common.

The clays range from greenish gray to olive gray in color and are typically

lighter colored than the clays of the underlying unit.

Phosphate grains are present virtually throughout the Marks Head For-

mation. They characteristically occur as brown to black, sand-sized grains

scattered throughout the sediments. The phosphate grains are rounded and

often in the same size range as the associated quartz sands. Phosphate'

pebbles occur rarely.

Mineralogically, the Marks Head Formation clays contain palygorskite,

sepiolite, smectite and illite; kaolinite is present only in the weathered

section (Hettrick and Friddell, 1984). Hettrick and Friddell (1984) indi-

cated that palygorskite is often the dominant clay mineral in this unit;

smectite is the second most abundant clay mineral. Smectite becomes the

most abundant clay mineral when palygorskite content decreases. Other

minor mineralogic constituents include mica, opal-ct and feldsoar.

Huddlestun (in press) reports the occurrence of zeolite in the Marks Head

Formation.

The Marks Head Formation is underlain disconformably throughout Nassau

County by the Penney Farms Formation. The upper part of the Penney Farms

Formation consists predominantly of darker, olive gray colored sands and

clays with occasional dolostone beds. The base of the Marks Head Formation

is placed at the contact between the darker colored sands and clays of the

upper Penney Farms and the generally lighter colored, more complexly inter-

bedded sands, clays and dolostone of the Marks Head. Occasionally, the

contact is marked by a rubble zone containing phosphatized carbonate clasts

but the unconformity is often difficult to recognize. The Coosawhatchie

Formation disconformably overlies the Marks Head Forma-tion throughout

Nassau County. The Coosawhatchie-Marks Head contact is generally placed at

the top of the first hard carbonate bed or light colored clay unit below

the darker colored clayey, dolomitic, quartz sands and dolostones of the

basal Coosawhatchie Formation. Occasionally, the contactappears grada-

tional in a sequence of dolostone and interbedded sands. In this case the

top of the Marks Head is placed at the uppermost hard dolostone bed in the

interbedded sequence. A rubble bed sometimes marks the unconformity. The

relationship of the Marks Head Formation to the underlying and overlying

units is graphically illustrated in Figures 6 and 7.

The Marks Head Formation of the Hawthorn Group occurs as a subsurface

unit in Nassau County. The top of the Marks Head Formation in the subsur-

face varies from -260 feet MSL in Carter #1, W-14619, Duval County to +114

feet MSL in Devil's Millhopper #1 W-14641 in Alachua County. The top of

the Marks Head in Nassau County varies from -100 feet MSL in the south-

western most corner to -250 feet MSL on the east coast (Figure 10).

A

Top of the Marks Head-Formation (shaded area
indicates undifferentiated Hawthorn Group)

Figure 10

V\ 5IF -

SLT.
AL OT O0

i O 0

0A OP HAWTHORN GROU-150

ILCHI STH .

,-50

SCL N CI 8 so A

.EGIN-L
20 doImug
t 5
20 !a K= IEa

e

The Marks Head Formation in Nassau County dips to the northeast and

east with an average dip of 4 feet per mile. The direction and angle of

dip may vary locally.

The thickness of the Marks Head Formation varies from zero on the

crest of the Ocala and Sanford highs to 130 feet in the core N.L. #1,

W-12360, Bradford County. In northwestern Nassau County, it is 80 feet

thick (Figure 11).

Datable-fossil assemblages within the Marks Head Formation have not

been found in north Florida. The only fossils noted were scattered molds

of mollusk shells and occasional diatom molds. Lithologic correlation be-

tween these sediments and those in Georgia, where fossiliferous sediments

are found, indicates that the Marks Head Formation is late Early Miocene

(Burdigalian) age (Huddlestun, personal communication, 1983). Planktonic

foraminifera in Georgia indicate Zone N.6 or early N.7 of Blow (1969).

As is the case for the Penney Farms Formation, the Marks Head Forma-

tion is older than the previously accepted age for the "Hawthorn Formation"

in Florida as interpreted by Cooke (1945) and Puri and Vernon (1964).

Cooke (1945) and Purl and Vernon (1964) suggested a strictly Middle Miocene

age for their "Hawthorn Formation".

Coosawhatchie Formation

The Coosawhatchie Formation of the Hawthorn Group .is used the upper

unit of the group in much of north Florida. Huddlestun (1987) proposed the

Coosawhatchie as a formal lithostratigraphic unit in Georgia. It extends

into north Florida with only minor lithologic changes (Scott, 1987).

The Coosawhatchie Formation in Florida consists of quartz sands, dolo-

stones and clays. Characteristically, clayey, sandy to very sandy dolo-

_ ~ II~-SPI~IY4~

'-.

25

S-50
7 A I

a7 .. 50

A 0A

S

CAL! 0 MrLS

I R0 40 1

LEGEND -
coams

j tIS DF MAwTHORN jaouP A -
...... .. --.

o

^ --------- L 0----- -

Figure 12 Top of Coosawhatchie Formation (shaded area
indicates undifferentiated Hawthorn Group)

0

'AA D 'S 0.-
'n ? 'IsoN i ~' L 7 C
T LTC

W

I -

tC L -A Yl

II -

GIRCHftsST J.!

* I
A tc H
o I~I~iP! 14 AIM -J, m-5
;ji I,8 n~~i-0

F AGL

I F I J v ,

1 '

SCALE N C 5 FEET IT
0 20 40 MILES
0 0 40 KILMETERS -- U MT R
LEGEND
CORES HERIIANDO
CUTTINGs I
AL UIMITS OF HAWTHORN GROUP r-

P -A S -C

.O
*.II/-.,A| ^ m~liB~ilU M

0 -,4^ S"S Ag ^*

v-^- ^ .-250
6 \ e A T \~~~R -200

-150

i.~.l-100

-I ii
Ni

Figure 12 Top of Coosawhatchie Formation (shaded area
indicates undifferentiated Hawthorn qroup)

L

I, ILU 1S A

E M N 01 E

nn a

1 j F j I

stone and dolomitic, clayey sands are the most common lithologies in the

upper part. In the lower part, the quartz sands and clays predominate with

interbedded dolostones.

The quartz sands are dolomitic, clayey and phosphatic. The sand

grains are fine to medium grained, poorly to moderately sorted, and

subangular to subrounded. The proportions of accessory materials vary

greatly. The sands grade into the dolostones and clays in many instances.

Phosphate content is quite variable ranging from a trace to more than 20

percent. Clay content varies from less than 5 percent to greater than 30

percent. The sands are often lighter colored in the upper part where there

is more carbonate in the matrix and darker in the lower part. Colors range

from greenish gray and light gray to olive gray. Induration is generally

poor.

The dolostones of the Coosawhatchie Formation are quartz sandy, clayey

*and phosphatic. The percentages of quartz sand and clay vary widely and

may be as much as 50 percent in transitional zones. Phosphate is quite

variable also, but is generally less than 10 percent. The dolostones are

micro-to finely crystalline, poorly to moderately indurated and occasionally

contain nolds of fossils. They range in color from light gray and greenish

gray to light olive gray. The dolostones of the upper part appear to

become more calcareous in the Jacksonville Basin.

The clays in the Coosawhatchie Formation are typically quartz sandy,

silty, dolomitic and phosphatic. The clays are light olive gray to olive

gray. Clay beds are most common in the lower member (Scott, 1983). The

clay mineralogy is dominated by smectite (Hettrick and Friddell, 1984).

The clay beds often contain diatoms (Hoenstine, 1984).

The phosphate grains present in the Coosawhatchie Formation are nor-

*mally amber colored to brown or black; lighter colors occur near the land
*

surface. The phosphate grains are usually well rounded and in the same

size range as the associated quartz sands. Coarser phosphate sands and

phosphate pebbles or rubble are not common but are present.

The Coosawhatchie Formation disconformably overlies the Marks Head

Formation but the disconformity is often not readily apparent. It is,

however, recognized biostratigraphically in Georgia (Huddlestun, personal

communication, 1983). The contact often occurs in a thin gradational

sequence of interbedded sands and dolostones. Occasionally, the contact is

marked by a rubble bed.

The Coosawhatchie is overlain by undifferentiated Plio-Pleistocene

deposits in most of northern Florida. In much of Nassau County, the

Coosawhatchie is overlain disconformably by the Pliocene Nashua Formation.

The relationship of the Coosawhatchie to the underlying and overlying units

is indicated in Figures 6 and 7.

The Coosawhatchie Formation occurs throughout much of north Florida.

The top of the Coosawhatchie ranges from -93 feet MSL in Bostwick #1,

W-14477, Putnam County to +168 feet MSL in Devils Millhopper #1, W-14641,

Alachua County. In Nassau County, the top of the Coosawhatchie ranges from

near sea level -in the southwestern corner edge to greater than -50 feet MSL

along the east coast (Figure 12). It attains a maximum thickness in

Florida (including the Charlton Member) of 222 feet in Carter #1, W-14619,

Duval County (Figure 13). Huddlestun (1987) indicates that the Coosawhat-

chie attains a maximum thickness of 284 feet in the southeast Georgia

Embayment in Georgia. The Coosawhatchie Formation dips in a northeasterly

to easterly direction in Nassau County. The average dip is approximately 4

feet per mile. The angle and direction of dip is variable throughout the

region.

150

125
-o200

S125

A 075
50

"I A

*S C IT N s 1 -So FE M as

+-- _.-- k+' i : ..---.

SOLEGENO C O '" -

l ouGH -I 1

Figure 13 Isopach of Coosawhatchfe Formation (shaded area
Indicates undifferentiated Hawthorn Group)
0 CUTING$
OFMATOA 5OP G

P ;A S
e_ I hL
r ~-.-I-Oqb

q -r r F r iI
00 s r

Fiue 3 Ispcho CoawacheFomtin(saedae
indiatesundfferntiaed awthrn Goup

The Coosawhatchie Formation is not known to occur over the Ocala and

Sanford highs or in the immediately surrounding areas. This is thought to

be due primarily to erosion; nondeposition may also have played a role.

The Coosawhatchie extends from Georgia southward into central Florida.

Huddlestun (1987) suggests a Middle Miocene (Early Serravallian.age)

for the Coosawhatchie Formation based on planktonic foraminifera.

Huddlestun placed it in Zone N.11 of Blow (1969). Hoenstine (1984) studied

diatoms from a few selected cores through the Hawthorn. He recognized a

Middle Miocene assemblage in Florida sediments assigned in this paper to

the Coosawhatchie Formation in northeastern Florida.

The Coosawhatchie Formation is widespread in northern Florida and

throughout most of this area the Coosawhatchie is the uppermost Hawthorn

sediment encountered. In limited areas, it is shallow enough to be exposed

in some foundation excavations. The Coosawhatchie Formation in the Jack-

sonville Basin contains a lower clay bed of variable thickness. This clay

bed correlates with the Berryville Clay Member of the Coosawhatchie

Formation in southeastern Georgia.

Charlton Member Of The Coosawhatchie Formation

Huddlestun (1987) redefined the "Charlton Formation" of Veatch and

Stephenson (1911) as a formal member of the Coosawhatchie Formation in

Georgia. He found that the Charlton Member is a lithofacies of the upper

part of the Coosawhatchie in south Georgia and north Florida. Huddlestun

(1987) discussed the reference localities in some detail. A reference sec-

tion for the Charlton Member of the Coosawhatchie Formation in Florida is

the Cassidy #1 core, W-13815, Nassau County (NWV4, NWI4, Sec. 32, T3N, R24E).

The surface elevation is 80 feet MSL. The Charlton Member occurs from +3

-L I- II I I -~*

feet MSL to -43 feet MSL.

The Charlton Member characteristically consists of interbedded carbo-

nates and clays. It is less sandy than the upper part of the Coosawhatchie,

into which it grades. It is typically low in sand and phosphate

(Huddlestun, 1987). Huddlestun (1987) states that the clay component is

often very conspicuous in the cores. This has been found to be true in

Florida also.

The carbonates of the Charlton Member are often dolostones but range

into limestone. They are slightly sandy, slightly phosphatic to non-

phosphatic and clayey. They often contain abundant molds of fossil

mollusks. The dolostones are finely crystalline, light olive gray and

poorly to moderately indurated. The limestones are characteristically very

fine grained, slightly sandy, clayey, poorly to moderately indurated, and

yellowish gray.

The clays are dolomitic to calcareous, with poor to moderate indura-

tion, silty, and light gray to greenish gray. The clay minerals present

include smectite, palygorskite, illite and kaolinite (Hettrick and

Friddell, 1984).

The Charlton Member both overlies and interfingers laterally with the

upper portion of the undifferentiated Coosawhatchie Formation. The Charl-

ton is simply a distinct faces of the upper Coosawhatchie. It is overlain

by the sediments discussed as overlying the Coosawhatchie Formation. The

upper contact is unconformable.

Sediments assigned to the Charlton occur at Brooks Sink (SWl/4, SWl/4,

Sec. 12, T7S, R20E, Bradford County) at an elevation of +145 feet MSL. The

highest elevation for the top of the Charlton in a core was in Wainwright

41, W-14283, Bradford County where it occurred at +109 feet MSL. The

deepest that the top of the Charlton Member was found is in Carter #1,

W-14619, Duval County where it is -38 feet MSL. The top is very near MSL

to Nassau County (Figure 14).

The Charlton Member of the Coosawhatchie Formation reaches its maximum

recognized thickness in Florida in Cassidy #1, W-13815, Nassau County,

where it is 70 feet thick (Figure 7 and 15). It is very spotty in its

occurrence.

The Charlton Member, as originally defined by Veatch and Stephenson

(1911), was considered Pliocene. Huddlestun (1987) postulates that, based

on his observations of the molluscan fauna and the lithostratigraphy of the

unit, it is Middle Miocene (Seravallian) in age.

Nashua Formation

The Nashua Marl of Matson and Clapp (1909) was reintroduced by

Huddlestun (1987) as the Nashua Formation. The name Nashua Marl had been

abandoned by Cooke and Mossom (1929) who replaced it with the Caloosahatchee

Marl, a presumed south Florida equivalent. The Florida Geological Survey,

in following the recommendation of Huddlestun (1987), utilizes the Nashua

Formation in northern Florida for the shelly sands, clays and some coquina.

In Florida, the Nashua is primarily shelly sands and clay. Data on the

extent of the Nashua and it's thickness in northern Florida is limited.

Huddlestun (1987) indicates that the Nashua underlies most of Nassau

County. The Florida Geological Survey core hole Cassidy #1, W-13815 in

west-central Nassau County, encountered the Nashua at 27.5 feet above MSL

with a thickness of approximately 50 feet.

Lithologically, the Nashua contains fine to medium quartz sands with

varying percentages of calcilutite, clay and shell. The occurrence of

shell, both whole and fragmented, occasionally becomes the dominant litho-

logic component. Colors range from light gray to light olive gray.

SCALE N a ""
0 20 40 ILSS

LEGENO
cons
a CUTTINGS
A>I LUMITS OF HAWTHORN GROUP

Figure 14

Top of the Charlton Member (dashed line indicates
extent of Charlton)

_) _

LEGEND
cORES
CUTTINGS
.AXJ'4IUMITS OF HAWTHORN GROUP

Figure 15

Isopach of the Charlton Member (dashed line indicates
extent of Charlton)

Plio-Pleistocene Undifferentiated and Holocene Sediments

The Plio-Pleistocene undifferentiated sediments mantle the Nassau
County area with a blanket of fine to medium quartz sands. These sediments

contain variable amounts of heavy minerals, silt, clay, iron staining and

organic matter. Data on the thickness of these sediments is very limited,

however, a thickness of 52.5 feet is recognized in W-13815. Holocene sedi-

ments occur along the modern coastline and in association with the present

day rivers and streams.

HAWTHORN GROUP GAMMA-RAY LOG INTERPRETATION
Gamma-ray logs are of particular importance to the investigator

studying the complex section of the Hawthorn Group. The gamma-ray activity

in the Hawthorn Group sediments is generally significantly higher than sub-

Jacent or suprajacent formations, thus allowing the delineation of this

unit. Also, since these sediments are often partially or entirely cased

off during well construction, the ability of gamma-ray probe to obtain

information through casing is most important. In the course of this study

gamma-ray logs were the only geophysical logs used. For a discussion of
resistivity logs of the Hawthorn Group sediments see Johnson (1984).

The Hawthorn Group of northern Florida consists of a complex sequence

of clastics and carbonates containing varying percentages of uranium-

bearing phosphate minerals. The resultant gamma-ray log shows widely

varying peak intensities (Figure 16). The patterns of peaks are similar

throughout much of the area from Duval County west to western Hamilton

County and from Nassau County south to southern Putnam County. The

Hawthorn thins and the gamma-ray signature changes somewhat south of Putnam
County in Marion, Lake and northwestern Orange counties. This is due to

CLAY COUNTY
W-14219
FEET

UNDIFFERENTIATED

-100

COOSAWHATCHIE
FFm.

-200- MARKS HEAD
2-00 Fm.

-300

PENNEY
FARMS
Fm.

-400

OCALA
GROUP

0 I0 PS 200

Figure 16 Gamma ray log, Jennings #1, W-14219, Clay County

both erosional removal of the upper sediments and less deposition in the

area between the Ocala Uplift and the Sanford High.

4 typical gamma-ray log from the north Florida area (Figure 16) con-

sists of five generalized zones. This gamma-ray signature is generally

present in north Florida. However, the pattern may show significant

variation in the intensities of peaks and thicknesses of peak groups.

Formational correlation with the gamma-ray signature is relatively con-

sistent. The upper, high intensity zone and part of the subjacent lower

intensity zone correlate with the Coosawhatchie Formation. The Marks Head

Formation correlates with part of the low intensity zone, the underlying

higher intensity zone, and the upper portion of the second low intensity

zone. The Penney Farms Formation incorporates the remainder of this low

intensity zone and the basal, high to very high intensity zone. The

underlying Ocala Group has significantly lower generalized signatures than

the sediments of the Hawthorn Group. The formational correlations with the

gamma-ray signature are shown in Figure 15. The upper and lower boundaries

of the Hawthorn Group are generally easily picked on the gamma-ray logs.

However, caution must be exercised in making formational identifications

based solely on the signatures.

_ ~---~----I~-~-

TABLE 1. GEOLOGISTS LOGS/CUTTINGS NASSAU COUNTY

Location
(T.R.Sec)

Well

Elevation

Depth

4N, 24E, 19, SE4
3N, 28E, 14
Ft. Clinch/Amelia Is.
3N, 28E, 24
3N, 28E, 24
3N, 28E, 30, NE4
3N, 28E, 24, NE4
5N, 24E, 27
30-43-10/81-37-50
2N, 27E, 42, SW4
Hilliard
Fernandina Beach
Hilliard
2N, 28E (Fer. Bch)
3N, 24E, 9, SW4
4N, 23E, 26
3N, 27E, 50
2N, 28E, 22
2N, 28E, 39
2N, 28E, 39
3N, 27E, 50
2N, 27E, 44
3N, 24E, 22, NW4
4N, 23E, 27, NE4

99'
15'
5'
15'
11'
20'
25'
10'
5'
37'

55'

70'
95'
40'
lot
10'
10'-

80'
60'

4,824'
900'
800'
750'
1,060'
2,130'
1,205'
60'
45'
905'
821'
1201'
700'
1200'
803'
98'
990'
1016'
95'
700'
580'(?)
624'
490'
905'

Geol. Log

336
371
391
343
670
890
2918
1030
1026
2964
3586
4310
4875
6265
6532
10482
10715
11100
12315
12317
13074
13563
13815
15662

Yes
Drillers
Yes
Partial
Yes
Yes
Drillers
Yes
Drillers
Drillers
Yes
Drillers
Drillers
Drillers
Yes
Core
Yes
Drillers
Yes
Yes

Drillers
Core

p -

GEOPHYSICAL LOGS NASSAU COUNTY

Geol. Loq #

Location
(T.R.Sec)

Elevation

I Ft. Below LSD

I Charl.

Coosa. M. Head P. Farms Ocala

3N, 28E, 30
- elect. only -
M M
u N

Ft. Clinch 543 10
3N, 28E, 24 40
Caliper only 12
3N, 28E, 35
3N, 24E, 32 (core) 80
Same as #9
SE Callahan 26
Fernan. Bch. CCA9 32
Same as #5
Fernan. Bch
(Test Well) 3
CCA #6 4
CCA #10 17
2N, 28E, 5 11
4N, 23E, 27 60
2N, 28E, Gulf Coarse ?
3N, 28E, 24 11
3N, 28E, 23 9
2N, 25E, 29 20

90
47?

-- 107
77 123

77

?

75?

827
?
--

119
?

119
74
?
98
129
118
111
113?
50

228?
223?

308?
252

170?
?

302?
?
?
298?
304?
310?
308?
?
?

360
384

366
332

258
387

380
380
394
357
359
366
373
390
237

529
536

545
482

421
535

546
532
558
533
307
540
547
545
388

*These are located west of Amelia Island; remainder are located in or near Fernandina
Beach.

20.1

295

404

560

5
6
7
8
9
*10
*11
12
13
14

15
16
17
*18
19
20
21
*22

TABLE 2.

200

190 _

180

170 _

160

150
IBO

130

120

110

100

90

80

70

60

50

T -T

7- 7/

2 ~-
,I,,* /*,. o

- -/--2_ -/.

- .
P ... ..
- P
HK\I

quartz sand

clayey quartz sand

calcareous quartz sand

dolomitic quartz sand

clay

sandy clay

calcareous clay

dolomitic clay

shell bed

dolomite

clayey dolomite

sandy. dolomite

calcareous dolomite

limestone

sandy limestone

clayey limestone

dolomitic limestone

phosphorite

chert

silt

no sample

Appendix B

BIBLIOGRAPHY/SELECTED REFERENCES

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origin of the "Pleistocene" sand mantle in
central Florida uplands and its bearing on
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Geological Survey, Professional Paper .400-B,
p. B202-B207.

Cathcart, J. B., and Young, E.
J., 1964, Geology and geochemistry of the Bone
Valley Formation and its phosphate deposits,
west central Florida.: Geological Society of
America Field Trip #6, Gelogical Society
of America 1964 Meeting, 68 p.

Assefa, G., 1969, Mineralogy and petrology of
selected rocks from the Hawthorne Formation,
Marion and Alachua counties, Florida:
(unpublished M. S. thesis), University of
Florida, p. 88.

Badiozamani, K., 1973, The Dorag dolomization model
application to the Middle Ordovician of Wis-
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Banks, J. E., and Hunter, M. E., 1973, Post-Tampa,
pre-Chipola sediments exposed in Liberty,
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Trans., Gulf Coast Association Geological
Society v.23, p. 355-363.

Bentor, Y. K., 1980, Phosphorites the unsolved
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and Mineralogists, Special Publication 29, p.
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Bergendal, M. H., 1956, Stratigraphy of parts of
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Bermes, B. J., 1958, Interim report on geology and
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Bishop, E. W., 1956, Geology and ground water re-
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n. 15, 115 p.

Blow, W. H., 1969, Late middle Eocene to Recent
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First Int. Conf. Planktonic Microfossils
(Geneva, 1967): E. J. Brill, Leiden,
Holland, v. 1., p. 199-421.

Brooks, H. K., 1966, Geological history of the
Suwannee River: Southeastern Geological
Society 12th Annual Field Conference Guidebook,
p. 37-45.

1967, Miocene-Pliocene problems of
peninsular Florida: Southeastern Geological
Society 13th Field Trip Guidebook, p. 1-2.

Gremillion, L. R., Olson, N. K., and
Puri, H. S., 1966, Geology of the Miocene and
Pliocene Series in the north Florida-south
Georgia area: Southeastern Geological Society
12th Annual Field Conference, 94 p.

Brown, D. W., Kenner, W. E., Crooks, J. W. and
Foster, J. B., 1962, Water resources of Brevard
County, Florida: Florida Geological Survey,
Report of Investigation n. 28, 104 p.

Burnett, W. C., 1977, Geochemistry and origin of
phosphorite deposits from off Peru and Chile:
Geological Society of America Bulletin v. 88,
p. 813-823.

Burnett, W. C., Veeh, V. H., and Soutar, A., 1980,
U-series, oceanographic and sedimentary evi-
dence in support of recent formation of
phosphate nodules off Peru: in Y. K. Bentor,
(ed.) Marine Phosphorites geochemistry,
occurrence and genesis, Society of Economic
Paleontologists and Mineralogists, Special
Publication n. 29, p. 61-72.

Carr, W. J.. and Alverson, D. C., 1959, Strati-
graphy of middle Tertiary rocks in parts of
west central Florida: U. S. Geological Survey
.Bulletin 1092, 111 p.

Cathcart, J. B., 1950, Notes on the land pebble
phosphate deposits of Florida: in Proceedings,
Symposium on mineral resources of the south-
eastern United States: University of Tennessee
Press, p. 132-151.

1963a, Economic geology of the
Keysville Quadrangle, Florida: U. S. Geologi-
cal Survey Bulletin 1128, 82 p.

,1963b, Economic geology of the
Chicora Quadrangle, Florida: U. S. Geological
Survey Bulletin 1162-A, 66 p.

,1964, Economic geology of the
Lakeland Quadrangle, Florida: U. S. Geologi-
cal Survey Bulletin 1162-G, 128 p.

1966, Economic geology of the
Fort Meade Quadrangle, Polk and Hardee coun-
ties, Florida: U. S. Geological Survey
Bulletin 1207, 97 p.

and Davidson, D. F., 1952, Distribu-
tion and origin of phosphate in the Land
Pebble Phosphate District of Florida: U. S.
Geological Survey TEI-212, 14 p.

and McGreevy, L. J., 1959,
Results of geologic exploration by core
drilling, 1953 Land Pebble Phosphate District,
Florida: U. S. Geological Survey Bulletin
1046-K, 77 p.

Chen, C. S., 1965, The regional lithostratigraphic
analysis of Paleocene and Eocene rocks of
Florida: Florida Geological Survey Bulletin
n. 45, 105 p.

Clark, D. S., 1972, Stratigraphy, genesis, and
economic potential of the southern part of the
Florida Land Pebble Phosphate Field: unpubl.
Ph.D. dissertation, University of Missouri -
Rolla, 182 p.

Colton, R. C., 1978, The subsurface geology of
Hamilton County, Florida with emphasis on the
Oligocene age Suwannee Limestone: unpubl. M.S.
thesis, Florida State University, 185 p.

Cooke, C. W., 1936, Geology of the Coastal Plain of
South Carolina: U. S. Geological Survey
Bulletin 867, 196 p.

1943, Geology of the Coastal Plain of
Georgia: U. S. Geological Survey Bulletin
-941,'' 1-21-p.

___, 1945., Geology of Florida: Florida
Geological Survey Bulletin n. 29, 339 p.

and Mossom, S., 1929, Geology of
Florida: Florida Geological Survey Annual
Report 20, p. 29-228.

Dall, W. H., 1896, Descriptions of Tertiary fossils
from the Antillean region: U. S. Natural
Museum, v. XIX, n. 1110, p. 303-305.

and Harris, G. D., 1892, Correlation
papers-Neocene: U. S. Geological Survey
Bulletin n. 84, p. 85-158.

Day, D. T., 1886, Phosphate rock: U. S. Geological
Survey, Mineral Resources of the United States
for 1885, p. 445-454.

Eldridge, G. H., 189,8, Preliminary sketch of the
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and models of dolomitization an introduc-
tion: in Zenger, D., Dunhan, J., and Ethington,
J., (eds.), Concepts and models of dolomitiza-
tion: Society of Econonomic Paleontologists
and Mineralogists, Special Publication n. 28,
p. 1-10.

	Main
	Front Cover
	Title Page
	Introduction and structure
	Lithostratigraphy
	Hawthorn group gamma-ray log...
	Bibliography

MILLISECOND	CLASS.METHOD	MESSAGE
0	sobekcm_page_globals.constructor
0	sobekcm_page_globals.constructor	Application State validated or built
0	sobekcm_database.verify_item_lookup_object
0	sobekcm_page_globals.constructor	Navigation Object created from URI query string
0	sobekcm_database.verify_item_lookup_object
0	sobekcm_page_globals.display_item	Retrieving item or group information
0	sobekcm_page_globals.get_entire_collection_hierarchy	Retrieving hierarchy information
0	sobekcm_assistant.get_entire_collection_hierarchy
0	cached_data_manager.retrieve_item_aggregation
0	cached_data_manager.retrieve_item_aggregation	Found item aggregation on local cache
0	item_aggregation_builder.get_item_aggregation	Found 'all' item aggregation in cache
0	system.web.ui.page.page_load (ufdc.page_load)
0	sobekcm_page_globals.constructor.on_page_load
0	html_echo_mainwriter.add_style_references	Adding style references to HTML
0	html_echo_mainwriter.add_text_to_page	Reading the text from the file and echoing back to the output stream
38	html_echo_mainwriter.add_text_to_page	Finished reading and writing the file