The Fishburne Formation (Lower Eocene), 

a Newly Defined Subsurface Unit in the 

South Carolina Coastal Plain

GEOLOGICAL SURVEY BULLETIN 153 7-C

The Fishburne Formation (Lower Eocene), 

a Newly Defined Subsurface Unit in the 

South Carolina Coastal Plain

By GREGORY S. GOHN, JOSEPH E. HAZEL, LAUREL M. BYBELL, and 

LUCY E. EDWARDS

CONTRIBUTIONS TO STRATIGRAPHY

GEOLOGICAL SURVEY BULLETIN 153 7-C

Stratigraphy of the newly 

defined Fishburne Formation, a thin lower Eocene 

limestone unit in the South 

Carolina Coastal Plain

UNITED STATES GOVERNMENT PRINTING OFFICE, WASHINGTON: 1 983
UNITED STATES DEPARTMENT OF THE INTERIOR 

JAMES G. WATT, Secretary

GEOLOGICAL SURVEY 

Dallas L. Peck, Director

Library of Congress Cataloging in Publication Data

Main entry under title:

The Fishburne formation (lower Eocene).

(Geological survey bulletin. Contribution to stratigraphy) (U.S. Geological Survey

bulletin ; 1537-C) 

Bibliography: p.

Supt. of Docs, no.: I 19.3:1537-C 

1. Geology, Stratigraphic Eocene. 2. Geology South Carolina. I. Gohn, Gregory S.

II. Series: Contributions to stratigraphy. III. Series: Geological Survey bulletin ;

1537-C.

QE75.B9 no. 1537-C 557.3S [551.7'84'09757] 83-600119 

[QE692.2]

For sale by the Distribution Branch, U.S. Geological Survey, 

604 South Pickett Street, Alexandria, VA 22304
CONTENTS

Abstract 

Introduction and previous work 

Distribution, thickness, and adjacent units 

Type section in Dorchester County 

Section in southern Charleston County 

Section in Beaufort County 

T? GfGT"GTi CGS Cited ________ _______________________ 

Page

 Cl

 1

 3

 5

 10

 12

 15

ILLUSTRATIONS

FIGURE 1.

2.

3.

4.

5.

Page

Map showing the locations of wells and cross sections C2 

Cross section showing the type section of the Fishburne Formation and

distribution of the unit in southern Dorchester County 7 

Generalized correlation chart indicating the chronostratigraphic and

biostr atigraphic position of the Fishburne Formation 9 

Cross section showing the distribution of the Fishburne Formation in

southern Charleston County 11 

Cross section showing the distribution of the Fishburne Formation in

Beaufort County 14

TABLE

TABLE 1. List of drill holes used in this report 

Page 

-C4

m

CONTRIBUTIONS TO STRATIGRAPHY

THE FISHBURNE FORMATION

(LOWER EOCENE),

A NEWLY DEFINED SUBSURFACE UNIT IN 

THE SOUTH CAROLINA COASTAL PLAIN

By GREGORY s. GOHN, JOSEPH E. HAZEL/ LAUREL M. BYBELL,

and LUCY E. EDWARDS

ABSTRACT

The Fishburne Formation is herein defined as the glauconitic, clayey, finely crystalline limestone that occurs below the middle Eocene Santee Limestone and above the 

Paleocene Black Mingo Formation in the subsurface of the South Carolina Coastal 

Plain. Calcareous nannofossils, ostracodes, dinoflagellates, foraminifers, and pollen indicate an early Eocene age for the Fishburne Formation in its type section and in other 

wells in South Carolina. The interval between 416 and 440 ft (depths from kelly 

bushing) in U.S. Geological Survey Clubhouse Crossroads No. 1, Dorchester County, 

is designated the type section. The Fishburne Formation is a relatively thin but 

laterally persistent subsurface unit southwest of the Charleston-Summerville, S.C., 

area; it does not occur northeast of those cities and is not known in outcrop. Calcareous 

quartz sand that occurs immediately above typical Fishburne sediments in wells in 

Beaufort County, S.C., is provisionally assigned to the Fishburne Formation.

INTRODUCTION AND PREVIOUS WORK

A relatively thin but widespread subsurface sequence of impure 

fine-grained limestone that occurs in parts of Dorchester, Charleston, 

Colleton, and Beaufort Counties, S.C., is herein described and defined 

as the Fishburne Formation. The unit is differentiated from vertically adjacent units by differences in glauconite and carbonate content, 

in grain size, and in signatures on geophysical logs. In several wells, 

the Fishburne contains ostracodes, calcareous nannofossils, 

dinoflagellates, foraminifers, and other fossils that indicate an early 

Eocene age.

'Now at Amoco Production Company, Research Center, P.O. Box 591, Tulsa, OK 74102.

Cl
C2 CONTRIBUTIONS TO STRATIGRAPHY

Stratigraphic studies of subsurface Eocene sediments in the coastal 

counties of southern South Carolina have been limited to short 

descriptions in ground-water reports, regional syntheses, and reports 

on individual wells. In the U.S. Government-Parris Island No. 2 well 

(fig. 1, well 8), beds assigned in this report to the Fishburne Formation 

have been grouped with underlying beds and assigned an early 

Eocene (Wilcoxian) age by Siple (1969, fig. 2) and Maher and Applin 

(1971). In the same well, McLean (1960) recognized the glauconitic 

limestone of the Fishburne and assigned it to the base of his middle 

Eocene (Claibornian) section, although he noted the absence of 

diagnostic fossils in samples from the interval. Counts and Donsky 

(1963) included these beds in U.S. Government-Parris Island No. 2 in 

their middle Eocene Lisbon Formation. Zupan and Abbott (1976) in80°45' 30' SOW 79°45'

DORCHESTE

Summerville

FIGURE 1. Locations of wells and cross sections that illustrate the distribution of the 

Fishburne Formation in South Carolina. Table 1 gives names of numbered wells.
FISHBURNE FORMATION, S.C. COASTAL PLAIN C3

eluded this unit in a Paleocene-lower Eocene section in several 

coastal wells.

Sediments of the Fishburne Formation were first recognized as a 

distinct lithologic unit by Gohn and others (1977) and Hazel and 

others (1977) in their studies of the continuously cored section in U.S. 

Geological Survey (USGS)-Clubhouse Crossroads No. 1 (CC1), Dorchester County (fig. 1, well 3). They provisionally assigned this unit 

to the top of their Black Mingo Formation, and Hazel and others 

(1977) suggested an early Eocene (late Sabinian, Ypresian) age on the 

basis of data from several fossil groups.

Gohn and others (1978) identified this thin limestone unit in the 

CC1 core as their informal unit Tej. These authors attempted to trace 

the distribution of Te^ and other Tertiary units throughout the subsurface in coastal areas of South Carolina. However, away from Clubhouse Crossroads, because of the lack of detailed biostratigraphic control, they incorrectly correlated Te\ with a middle Paleocene clay 

unit, which has similar signatures on geophysical logs, and carried 

this erroneous correlation through several wells in Charleston County and in southern Georgetown County to the northeast. Their correlations in Beaufort County (their wells 10, 11, and 13), with minor 

revision, are consistent with the correlations used in the present 

paper.

Acknowledgments. Cuttings from the Fripp Island water well and 

a copy of the driller's log for the Kiawah Island water well were supplied by the South Carolina Geological Survey. Geophysical logs for 

the Stal 1 and Stal 3 drill holes were run by the South Carolina Water 

Resources Commission; cuttings from these holes were logged in the 

field by Earl M. Lemon, Jr. (USGS). We thank the Westvaco Company for the use of their land as drilling sites for Stal 1, Stal 3, and CC1. 

Drilling operations by the USGS near Charleston, S.C., are supported 

by the U.S. Nuclear Regulatory Commission, Office of Nuclear 

Research, under Agreement No. AT(49-25)-1000. We are grateful to 

R. Z. Poore, USGS, for identifying and interpreting the planktic 

foraminifers from the Fishburne Formation in CC1.

DISTRIBUTION, THICKNESS, AND ADJACENT UNITS

Data gathered for the present report (table 1) and reexamination of 

the correlations by Gohn and others (1978) indicate that sediments 

defined herein as the Fishburne Formation occur only in the subsurface southwest of the Charleston-Summerville area (fig. 1). In 

southern South Carolina, the Fishburne is a thin but laterally persistent unit that can be traced to wells near the Georgia border. The unit
C4 CONTRIBUTIONS TO STRATIGRAPHY

TABLE 1. List of drill holes used in this report 

[* denotes U.S. Geological Survey stratigraphic test holes; remaining drill holes are water wells]

Drill-hole 

number Drill hole County Total depth

(in feet) Sources of data

1 Stall* Dorchester 526

2 Stal 3* do 484

3 Clubhouse do 2,599 

Crossroads 

No. 1*.

4 Charleston Charleston 2,078 

Medical Center.

5 Kiawah Island do 2,287

6 Edisto Beach do 970

7 Fripp Island Beaufort 3,168

8 Parris Island do 3,454 

No. 2.

Cuttings 

Fossils 

Gamma log

Cuttings 

Fossils 

Gamma log

Core 

Fossils 

Gamma and electric logs

Gamma and electric logs

Do. 

Driller's log

Fossils 

Gamma log

Cuttings 

Fossils 

Gamma and electric logs

Gamma and electric logs 

Published data

is 24 ft thick in the type section in CC1 and reaches a maximum observed thickness of 74 ft in the Fripp Island water well in Beaufort 

County.

Grohn and others (1977) and Hazel and others (1977) assigned 

dominantly quartzose or clayey Paleocene sediments below the Fishburne Formation in CC1 to the Black Mingo and Beaufort(?) Formations, although traditional practice has been to assign all Paleocene 

sediments in South Carolina to the Black Mingo Formation (see, for 

example, Van Nieuwenhuise, 1978). Because sediments assigned to 

the Beaufort(?) Formation are now known to be lithologically and biostratigraphically equivalent to outcropping sediments of the lower 

part of the Black Mingo Formation in its type area, Williamsburg 

County, S.C. (Van Nieuwenhuise, 1978), the entire Paleocene section 

below the Fishburne Formation is herein assigned to the Black 

Mingo Formation. A laterally continuous marker bed (gamma peak 

labeled "middle Paleocene marker") within the Paleocene section is 

shown on figures 2, 4, and 5.
FISHBURNE FORMATION, S.C. COASTAL PLAIN C5

Middle Eocene limestone above the Fishburne is typically assigned 

to the Santee Limestone (see, for example, Gohn and others, 1977; 

Hazel and others, 1977; Ward and others, 1979). According to the 

stratigraphy of Ward and others (1979), the Santee consists of two 

members: an upper Cross Member consisting of finely crystalline 

limestone and a lower Moultrie Member consisting of megafossiliferous limestone. The distribution of these members, where known, is 

shown on the cross sections in this report. On these sections, upper 

Eocene and upper Oligocene sediments in Dorchester and Charleston 

Counties are assigned to the Harleyville, Parkers Ferry, and Ashley 

Members of the Cooper Formation, following Ward and others (1979), 

and upper Eocene limestone in Beaufort County is assigned to the 

Ocala Limestone, following Counts and Donsky (1963). [An alternative stratigraphy to that used herein for middle and upper Eocene 

limestone is given by Baum and others (1980)].

TYPE SECTION IN DORCHESTER COUNTY

The interval between depths2 of 416 and 440 ft in CC1 is designated 

the type section for the Fishburne Formation. The formation name is 

taken from Fishburne Creek, which drains the area in southern Dorchester County between CC1 and Stal 3.

In CC1, there is a sharp contact between coarse-grained, bryozoanmollusk limestone of the Santee Limestone and underlying finer 

grained, clayey limestone of the Fishburne. No phosphate-glauconite 

bed, which is typical of the other major contacts in the core (Gohn and 

others, 1977, p. 63), occurs at the base of the Santee. The basal contact 

of the Fishburne is also sharp but irregular between glauconitic, finegrained limestone above the megafossiliferous, highly porous, quartzose limestone in the top of the underlying Paleocene section. 

Glauconite from the basal Fishburne bed is piped down about 3 ft into 

the Paleocene limestone.

In the type section, the Fishburne Formation consists of nodular, 

glauconitic, clayey limestone, which shows only minor variation in 

lithology. The limestone typically is greenish gray to pale olive in 

color (dry) and shows little evidence of stratification. This lack of bedding is probably due to bioturbation, which is represented by subtle 

mottling produced by minor differences in sediment color and texture. Secondary calcite nodules as large as 4.0 in. in maximum 

diameter occur throughout the unit.

"Depths used in this report are measured from geophysical logs. For CC1, subtract 5 ft (difference 

between elevation of ground level and kelly bushing) from stated depths in this report to get depths 

measured from the top of the core as used by Gohn and others (1977) and Hazel and others (1977).
C6 CONTRIBUTIONS TO STRATIGRAPHY

Petrographically, the limestone is a clayey, microfossil-mollusk biomicrite. It contains common to abundant sand-sized and larger mollusk fragments, particularly in the upper half and the basal 2 ft, and 

abundant microfossils, principally ostracodes and benthic foraminifers. The carbonate (acid-soluble) fraction of the unit decreases progressively downward from about 75 percent in the top 5 ft of the formation to 40 or 50 percent in the lowest 5 ft. Insoluble residues 

consist of nearly equal parts of clay and silt-sized to fine-sand-sized 

glauconite and quartz.

The Fishburne Formation has a distinctive signature on electric 

logs and natural gamma logs run in the type well and in other wells 

(fig. 2). On electric logs, the Fishburne has a "necked" pattern produced by low values on the resistivity log and a positive deflection on 

the spontaneous potential log. This signature reflects the generally 

low porosity and permeability of the fine-grained Fishburne sediments and contrasts with the signatures of permeable limestones and 

sands in the overlying and underlying sections. The relatively high 

glauconite and clay content of the Fishburne Formation produces a 

high-value signature on gamma logs that contrast with the 

signatures of the less glauconitic, nonclayey lithologies in the adjacent parts of the bounding formations.

From the 417- to 439-ft interval in CC1, the following microfossils 

were obtained.

Calcareous nannofossils (partial list) Depth below kelly bushing (in ft) 

Discoaster barbadiensis Tan Sin Hok, 1927 426,436 

Transversopontis duocavus (Bramlette and Sullivan, 1961) Locker, 1972 -426 

T. pulcher (Deflandre, 1954) Hay, Mohler, and Wade, 1966 426, 436 

T. pulcheroides (Sullivan, 1964) Perch-Nielsen, 1971 426 

Zygodiscus herlyni Sullivan, 1964 426, 436

The presence of Z. herlyni, which last occurs at or near the top of the 

Discoaster diastypus Zone of Bukry (1973), and the species T. 

pulcheroides and D. barbadiensis, which first occur in the Discoaster 

diastypus Zone, indicate placement of the Fishburne Formation at 

this locality in the lower Eocene (Ypresian) in the Discoaster 

diastypus Zone [coded CP9 in the system of Bukry (1981) and NP9 or 

NP10 in the system of Martini (1971)].

Planktic foraminifers (partial list) Depth below kelly bushing (in ft) 

Morozovella subbotinae (Morozova, 1939) 439 

M. marginodentata (Subbotina, 1953) 439 

Planorotalites aff. P. chapmani (Parr, 1938) (These specimens are

morphologically close to Pseudohastingerina wilcoxensis.) 429 

Pseudohastigerina wilcoxensis (Cushman and Ponton, 1932) 439 

Chiloguembelina crinita (Glaessner, 1937) 439

The occurrences of Morozovella subbotinae, M. marginodentata, and 

Pseudohastigerina wilcoxensis without M. aragonensis or M. velascoensis
Top of Santee

Limestone . . ^Spontaneoa

Gamma| potential! 

300l

Drill-hole no. 3 Drill-hole no. 2 

FEET METERS FEET METE

50 Undifferentiated Parkers Ferry 

and Harleyville Members 

of Cooper Formation 200

Lateral Cross Member 

l resistivitv of Santee Limestone

Moultne Member 

of Santee Limestone^

300

50 

Beaufort(?) Formation 

of Gohn and others (1977)

100 OHMxM'/M

AMERICAN 

PETROLEUM MILLIINSTITUTE VOLTS 

UNITS

FIGURE 2. Cross section A-A' (fig. 1) showing the type section 

(in CCI) and distribution of the unit in southern Dorchester C

drill hole no. 2, Stal 3; drill hole no. 3, CCI.
C8 CONTRIBUTIONS TO STRATIGRAPHY

indicates that this sample (from 439 ft below kelly bushing) is within 

the Morozovella subbotinae Zone of Stainforth and others (1975). This 

zone is early Eocene in age.

Ostracodes (partial list) Depth below kelly bushing (in ft) 

Ouachitaia broussardi (Howe and Garrett, 1934) 420, 439 

Hazelinaaff. H. pauca (Schmidt, 1948) 439 

Buntonia alabamensis (Howe and Garrett, 1934) 439 

Acanthocythereis hilgardi (Howe and Garrett, 1934) 417, 420, 439 

Cytherelloidea montgomeryensis of Pooser (1965) 417, 439 

Haplocytheridea wallacei (Howe and Garrett, 1934) 417, 420 

Phractocytheridea cf. P. veatchi (Howe and Garrett, 1934) 420 

Konarocythere blackmingoensis (Pooser, 1965) 420 

Opimocythere aff. O. martini (Murray and Hussey, 1942) 417, 420

This assemblage is indicative of the provincial Sabinian Stage (upper 

Paleocene and lower Eocene). The presence of an Opimocythere 

related to O. martini, a common Claibornian form, the abundance of 

Haplocytheridea wallacei, and the absence of early Sabinian indicators common in the Paleocene Black Mingo Formation (Van 

Nieuwenhuise, 1978) suggest a late Sabinian (early Eocene) Age. The 

ostracode assemblage also suggests deposition at inner-sublittoral 

depths in a warm-temperate or warmer climate.

Dinoflagellates and acritarchs Depth below kelly bushing (in ft) 

Ascostomocystis hydria Drugg and Loeblich, 1967 439 

Cordosphaeridium multispinosum Davey and Williams, 1966 439 

Fibrocysta lappacea (Drugg, 1970) Stover and Evitt, 1978 439 

Senegalinium dilwynense (Cookson and Eisenack, 1965) Stover and

Millioudodinium tenuitabulatum (Gerlach, 1961) Stover and 

Evitt, 1978 439

Wilsonidium cf. W. tabulatum (Wilson, 1967) Lentin and 

Williams, 1975 418, 439

Ascostomocystis hydria and Fibrocysta lappacea are known only from 

upper Paleocene and lower Eocene deposits. Senegalinium dilwynense also last occurs in the early Eocene. The genus Wilsonidium 

first appears in lower Eocene deposits (Costa and Downie, 1979). Thus 

the dinoflagellates indicate an early Eocene age.

Pollen. Frederiksen (1980) and Frederiksen and Christopher 

(1978) have reported on the sporomorphs from the type section of the 

Fishburne Formation. The abundance of Platycarya platycaryoides 

(Roche, 1969) Frederiksen and Christopher, 1978, and Platycaryapollenites swasticoidus (Elsik, 1974) Frederiksen and Christopher, 1978, 

as well as the joint occurrences of Nuxpollenites spp., Thomsonipollis 

magnifica (Pflug in Thomson and Pflug, 1953) Krutzsch, 1960, and 

Pseudoplicapollis limitata Frederiksen, 1978, in the Fishburne clearly indicates a late Sabinian (early Eocene) Age.

In summary, all the above fossil groups indicate an early Eocene 

age for the type Fishburne Formation. The Fishburne Formation cor-
FISHBURNE FORMATION, S.C. COASTAL PLAIN C9

relates with the Potapaco Member of the Nanjemoy Formation in 

Virginia (Gibson and others, 1980) and, on the basis of foraminiferal 

data presented in Enright (1969), with the lower part of the Manasquan Formation of New Jersey (fig. 3).

The Fishburne Formation also was encountered in another drill 

hole, Stal 3, in southern Dorchester County (figs. 1, 2). In this hole,

CHRONOSTRATIGRAPHIC UNITS

t?

CO 

Q.

O>

C

o> 

o 

o

LLJ

tT

CO 

Q.

O>

O> 

O 

O

C 

<D CO 

_l

C 

CO

£

Q.

Thanetian

c

CO

Et

O CO 

-Q Q.

CO

c

CO

_c

CO 

CO

CO

c

CO 

CO

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ZONES

NANNOFOSSILS

NP15(part)

NP14

NP13

NP12

NP10/11

NP9

NP7/8

NP6

NP5

FORAMINIFERS

P10 

7

P9

 7 

P8

P7

P6

P5

P4

P3 

(part)

NEW JERSEY

Shark River 

Formation

Manasquan 

Formation

Vincentown 

Formation

Hornerstown 

Formation

VIRGINIA c

Formation mjemoy 

z

Woodstock 

Member

Potapaco 

Member fT\I

 > 1 1 r

Marlboro Clay

A Bl Aquia p 

Formation

SOUTH 

AROLINA

ishburne^1- 

ormation ^

7 \ 1 1 ill

ack Mingo 

ormation 

(part)

FIGURE 3. Generalized correlation chart indicating the chronostratigraphic and biostratigraphic position of the Fishburne Formation. New Jersey data from Enright 

(1969), Loeblich and Tappan (1957a, b), and Olsson (1960). The position of the base 

of the Vincentown Formation follows Owens and Minard (1964), who included all 

the Olenothryris harlani beds in the Vincentown. The Virginia column is based 

primarily on data in Gibson and others (1980) and in Hazel (1969); unpublished information on calcareous nannofossils, ostracodes, and dinoflagellates was also 

used. The South Carolina column is based on data given herein and in Gohn and 

others (1977), Hazel and others (1977), and studies in progress. The Fishburne and 

Black Mingo Formations are equivalent to part of the Black Mingo Formation as 

used in Gohn and others (1977) and Hazel and others (1977). The coded calcareous 

nannofossil and planktic foraminifer zones are after Martini (1971), Stainforth and 

others (1975), and Hardenbol and Berggren (1978).
CIO CONTRIBUTIONS TO STRATIGRAPHY

cuttings between depths of 326 ft and about 390 ft consist of microfossiliferous, glauconitic fine-grained limestone. Ostracodes and benthic foraminifers are abundant in these samples (5-15 percent), and 

some mollusk fragments (5 percent) also are present. Glauconite content averages 5 to 15 percent, but glauconite may constitute as much 

as one-third of individual samples of cuttings. The limestone cuttings 

are typically grayish yellow green or yellowish gray when dry. Unfortunately, caving of the hole prevented geophysical logging of this part 

of the section.

In the Stal 3 hole, cuttings from the interval between 324 and 394 ft 

contained the same ostracodes as does the Fishburne in its type section, plus several other forms, including Phractocytheridea moodyi 

(Howe and Garrett, 1934), Haplocytheridea stuckeyi of Pooser (1965), 

and an undescribed Acanthocythereis that is also known from the 

Hatchetigbee Formation of Alabama. This is a Sabinian, most probably late Sabinian, assemblage. The dinoflagellate flora from the cuttings between 354 and 364 ft contains many middle Eocene through 

late Oligocene contaminants, but it also contains Wilsonidium sp., 

Fibrocysta lappacea (Drugg, 1970) Stover and Evitt, 1978, and 

Kallosphaeridium brevibarbatum De Coninck, 1975, which together 

indicate an early Eocene age.

The Fishburne Formation cannot be recognized in logs or cuttings 

from Stal 1 (fig. 2). In that hole, at a depth of 345 ft, nonglauconitic, 

fine-grained limestone of the Cross Member of the Santee Limestone 

(Ward and others, 1979) appears to directly overlie quartz sand that 

contains an early Sabinian (late Paleocene) ostracode fauna. In particular, that fauna includes (at 357 ft) Triginglymus dictyolobus of 

Pooser (1965), which appears to be a good regional marker for sediments of early Sabinian Age. However, the Sabinian species 

Haplocytheridea wallacei (Howe and Garrett, 1934), a distinctive and 

dominant element of the Fishburne ostracode assemblage, occurs 

commonly in cuttings from depths of 364 to 374 ft and 404 to 414 ft. 

This occurrence suggests that a thin, lithologically unrecognized bed 

referrable to the Fishburne Formation is present between the upper 

Paleocene sand and the Cross Member. Stal 1 is probably very near 

the updip limit of the Fishburne Formation.

SECTION IN SOUTHERN CHARLESTON COUNTY

Water wells drilled at Charleston, Kiawah Island, and Edisto 

Beach (figs. 1, 4) illustrate the distribution of the Fishburne Formation in southern Charleston County. The gamma log for the Edisto Beach 

well went to a depth of 653 ft (total depth of hole is 970 ft) and recorded 

at least the upper part of the Fishburne Formation between depths of 

626 ft and the bottom of the log (fig. 4). The high-value signature of
FISHBURNE FORMATION, S.C. COASTAL PLAIN Cll
C12 CONTRIBUTIONS TO STRATIGRAPHY

that unit can be correlated with a similar signature in the Kiawah 

Island well, as can the gamma peak at the top of the Santee Limestone (fig. 4). Lithologic information from cuttings was not available 

for the Edisto Beach well; however, ostracodes in a sample collected 

by G. E. Siple (USGS) in 1962 indicate a late Sabinian Age for the 

Fishburne in this hole. In the sample interval between 627 and 700 ft, 

which includes the Fishburne Formation and perhaps some small 

but unknown thickness of underlying Paleocene sand, cuttings contained the diagnostic Sabinian species Haplocytheridea wallacei 

(Howe and Garrett, 1934).

In the Kiawah Island well, the gamma log has a high-value signature between depths of 530 and 576 ft that contrasts with lower values 

for overlying and underlying sediments. However, the "necked" 

electric-log signature of the Fishburne is less obvious in this well 

than in CC1. On the driller's log, the interval between 532 and 565 ft 

is described as "fine black sand." These data are interpreted to represent beds of glauconitic fine-grained limestone similar to those of the 

Fishburne Formation in the type section, and the Kiawah section 

from 530 to 576 ft is assigned to that formation. The driller's log lists 

"soft rock" (Santee) above the Fishburne and "light gray or gray 

sand" (Black Mingo) below. No fossil data are available from the 

Kiawah well.

In Charleston County, the Fishburne Formation probably does not 

extend any great distance northeast of the City of Charleston. As 

shown on figure 4, a thin section of Fishburne sediments (less than 10 

ft) is interpreted from the logs for drill hole no. 4 in Charleston City, 

and the section there is similar, with the addition of the Moultrie 

Member, to that encountered in Stal 1 near Summerville (fig. 2). Accordingly, the approximate updip limit of Fishburne Formation 

is drawn as the dashed line on figure 1.

SECTION IN BEAUFORT COUNTY

Approximately 60 to 70 ft of subsurface Eocene sediments in Beaufort County is provisionally assigned to the Fishburne Formation. 

There, the sediments of the lower half of the formation resemble 

Fishburne sediments found in the wells to the northeast and contain 

early Eocene calcareous nannofossils. However, sediments provisionally assigned to the upper half of the unit are not found to the 

north and northeast.

Glauconitic, fine-grained, clayey limestone occurs in cuttings from 

the Fripp Island and Parris Island No. 2 water wells (figs. 1, 5). 

Descriptions of sediments in the Parris Island No. 2 well given by 

McLean (1960) and listed in unpublished USGS data files indicate
FISHBURNE FORMATION, S.C. COASTAL PLAIN C13

that light-gray or light-yellowish-gray, fossiliferous limestone containing locally common quartz sand and glauconite occurs between 

depths of 670 and 970 ft. A sample at 946 ft contains abundant 

glauconite, and a sample at 970 ft is almost exclusively glauconite. 

However, the electric log for this well shows the characteristic 

"necked" signature of the Fishburne Formation only between depths 

of 895 and 955 ft (fig. 5). The gamma log shows a highly radioactive 

section between depths of 928 and 958 ft but no significant feature at 

895 ft. From these data, the Fishburne Formation is interpreted to occur between depths of 895 and 958 ft in the Parris Island No. 2 well.

The lower half of the formation consists of glauconitic fine-grained 

limestone similar to the typical Fishburne lithology in Charleston 

and Dorchester Counties. The presence of abundant glauconite in the 

sample at 970 ft is attributed to caving from a glauconite bed at the 

base of the Fishburne (950-958 ft). The upper half of the formation 

consists of less glauconitic (and less clayey) limestone that is not present at the Dorchester and Charleston sections. The upper contact at 

895 feet is distinctive on the electric log but lacks a significant gamma peak, as is true of this contact in the sections to the northeast.

In the Fripp Island water well (fig. 5), a 74-ft-thick section (816- to 

890-ft interval) that is similar to the Fishburne section in Parris 

Island No. 2 is also provisionally assigned to the Fishburne Formation. However, in the Fripp Island well, the upper nonglauconitic bed 

appears as an uncharacteristically permeable unit on the spontaneous potential log, and the upper and lower contacts are marked 

by distinct gamma peaks (fig. 5). Between depths of 858 and 890 ft, 

the characteristic "necked" electric log pattern and high gamma 

values are compatible with cuttings consisting of moderately 

glauconitic, silty and clayey, microfossiliferous fine-grained limestone. Common phosphate and glauconite in the cuttings from 890 to 

900 ft represent the basal gamma peak at 890 ft. The upper half of the 

formation, between 816 and 858 ft, consists of medium-grained, wellsorted quartz sand containing some macrofossil fragments. 

Phosphatic and glauconitic limestone in cuttings between 797 and 

816 ft (and below as cavings) represents the lithology producing the 

high gamma values in the basal beds of the overlying Santee Limestone.

Calcareous nannofossils were examined in several Tertiary 

samples from the Fripp Island well. In the lower half of the Fishburne 

Formation, cuttings of Fishburne lithology from 867 to 880 ft contain 

Transversopontis pulcheroides and Toweius craticulus Hay and 

Mohler, 1967, which became extinct in the early Eocene. The 

presence of these two species and the absence of exclusively 

Paleocene species suggest an early Eocene age for at least the lower 

half of the Fishburne Formation in this well. A bulk sample of cut-
Top of Santee

Drill-hole no. 8

150

1100

1200

-20+

u 

MILLIVOLTS

Ocala Limestone 

Gamma

Top of Claibornian

250

300

350

of Maher and Applm (1971) 

Santee Limestone

J

20 OHM x M'/M

Fishburne Formation

Black Mingo 

Formation

FIGURE 5. Cross section C-C' (fig. 1) showing the distribution of the Fish

hole no. 7, Fripp Island; drill hole no. 8, Parr
FISHBURNE FORMATION, S.C. COASTAL PLAIN C15

tings from the upper half of the Fishburne at 824 to 837 ft contains 

only middle and late Eocene species. However, the medium-grained 

sand in this interval does not have an appreciable fraction of finegrained sediment, from which nannofossils are normally obtained. In 

addition, this sand may represent a near-shore environment of 

deposition that was too shallow for many nannofossil species. Hence, 

these middle and late Eocene species may represent down-hole contamination from more fossiliferous units into a nannofossil-poor interval. Although a middle Eocene age cannot be discounted for the 

upper part of the unit, the Fishburne Formation is assigned an early 

Eocene age in the Fripp Island well.

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