Ostracode Biostratigraphy 

of the Yorktown Formation 

(upper Miocene and lower 

Pliocene) of Virginia 

and North Carolina

GEOLOGICAL SURVEY PROFESSIONAL PAPER 704

Ostracode Biostratigraphy 

of the Yorktown Formation 

(upper Miocene and lower 

Pliocene) of Virginia 

and North Carolina

By JOSEPH E. HAZEL

GEOLOGICAL SURVEY PROFESSIONAL PAPER 704

Three ostracode assemblage zones are 

proposed for deposits assigned to the 

Yorktown Formation. The older two 

zones are considered to be late 

Miocene in age and the youngest 

early Pliocene

UNITED STATES GOVERNMENT PRINTING OFFICE, WASHINGTON : 1971
UNITED STATES DEPARTMENT OF THE INTERIOR

GEOLOGICAL SURVEY 

William T. Pecora, Director

Library of Congress catalog-card No. 76-610127

For sale by the Superintendent of Documents, U.S. Government Printing Office 

Washington, D.C. 20402 - Price 30 cents (paper cover)
CONTENTS

Page

Abstract.____________________________________________ 1

Introduction ________________________________________ 1

Acknowledgments.- - ____---_-__-______-_-__________-_ 2

Previous work_______________________________________ 2

Ostracode biostratigraphy______________________________ 2

Age of the Yorktown Formation.____________-----_-___ 8

Paleogeography.___-_____-______-__----__---___---___ 8

Localities. __________________________________________ 10

References.______________-__________---___----__-___ 10

ILLUSTRATIONS

FIGURE 1. Map showing location of collections-______---_______-_-____---_-___-__----_---------_--_----__-------_--__ 1

2. Q-mode dendrogram and trellis diagram based on calculation of Dice similarity coefficients._____________________ 3

3. Chart showing suggested biostratigraphic position of Yorktown samples used in Q-mode analysis.__.-____--_.____ 4

4. R-mode dendrogram for 80 ostracode species that occur in five or more samples. -______--__-__--___-_-.-________ 5

5. Map showing location of samples containing brackish-water elements_______-_-___----____--________----__---_ 9

6. Diagram showing general trend through time of the Yorktown transgression and regression______________________ 10

TABLE

TABLE 1. Occurrence of 84 Yorktown species that occur in four or more samples.________________________________________ 6

in

OSTRACODE BIOSTRATIGRAPHY OF THE YORKTOWN FORMATION

(UPPER MIOCENE AND LOWER PLIOCENE)

OF VIRGINIA AND NORTH CAROLINA

By JOSEPH E. HAZEL

ABSTRACT

The Yorktown Formation of Virginia and North Carolina is 

divided into three ostracode assemblage zones based on the occurrence of 230 species in 43 samples. The samples were compared in 

Q-mode using the Dice binary similarity coefficient and cluster 

analysis. From oldest to youngest, the three zones are the Pterygocythereis inexpectata, Orionina vaughani, and Puriana mesacostalis 

Zones. The first two are late Miocene in age and the last, which is 

poorly represented in Virginia, is considered to be early Pliocene 

in age.

The level of association (R-mode study using the Dice coefficient) between 80 of the more commonly occurring species is shown 

by means of a dendrogram; values for the biostratigraphic fidelity 

and constancy of each of these species for each of the zones are 

given.

A general trend through time from late Miocene to early Pliocene 

for the Yorktown transgression and regression is suggested, based 

on the occurrence of brackish-water ostracodes and bivalves, 

particularly Cyprideis and Corbicula. It is suggested that rapid 

transgression of the sea occurred during early Yorktown time to a 

maximum during the time represented by the middle Orionina 

vaughani Zone. A more or less steady regression of the sea followed 

during the remainder of Yorktown time.

INTRODUCTION

The Yorktown Formation (upper Tertiary) of North 

Carolina and Virginia is a very fossiliferous, lithologically heterogeneous unit with an exposed thickness 

(natural exposures or open-pit mines) of about 70-120 

feet. The sandy clays and clayey sands assigned to the 

Yorktown crop out discontinuously in a 16,800-squaremile area between the Rappahannock River in Virginia 

and the Neuse River in North Carolina (fig. 1). South 

of the Neuse River, deposits of the same general age 

as the Yorktown are usually mapped as Duplin Marl.

No microfossil zonation exists for the Yorktown. 

This report presents the results of a reconnaissance collecting program in conjunction with examination of existing museum collections, the object being to provide 

a regional ostracode zonation. Localities (fig. 1; p. 10) 

were chosen on the basis of geographic and stratigraphic spread. More detailed collecting will be done in 

locally complex areas such as the York-James peninsula 

where the distribution of numerous lithofacies within 

the Yorktown is being studied (Johnson, 1969; Coch, 

1968; Bick and Coch, 1969).

78

0 25 50 75 100 KILOMETERS 

i i i i 11 i I I

FIGURE 1. Location of collections; numbers correspond to those 

in locality list (p. 10). Dashed line encloses area in which 

Yorktown Formation crops out in natural exposures.

1
OSTRACODES, YORKTOWN FORMATION, VIRGINIA AND NORTH CAROLINA

ACKNOWLEDGMENTS

I am grateful to T. R. Waller, P. C. Valentine, and 

Druid Wilson for critically reading the manuscript and 

making suggestions for its improvement. Warren Blow, 

T. R. Waller, Druid Wilson, L. W. Ward, and T. G. 

Gibson made collections available for this study. The 

Texas Gulf Sulphur Co. allowed me access to exposures 

in their Lee Creek, N. C., mine. Mr. Blow also provided 

valuable technical assistance.

The calculations used in this paper were made on 

the U. S. Geological Survey IBM system 360/65. The 

program used is coded A243. I thank Paul Zabel and 

Nancy J. Cotner for their technical help and advice 

during this phase of the study.

PREVIOUS WORK

The only extant formal zonation for the Yorktown 

deposits is that of W. C. Mansfield (in Gardner, 1943) 

which is based on mollusks collected in the 1920's and 

1930's. Mansfield divided the Yorktown of Virginia into 

two zones. He placed the lower beds of the formation in 

the Pecten clintonius Zone (or Zone 1) which he said 

did not exceed 25 feet in thickness. He referred the remainder of the Yorktown of Virginia to the Turritella 

alticostata Zone (or Zone 2), which he divided into 

"beds" or "groups" of beds. As Mansfield defined and 

used them, these are neither lithic nor biostratigraphic 

units (see discussions by McLean, 1956; Johnson, 1969), 

and the correlations he proposed for some of the units 

of Zone 2 are of doubtful validity. Despite this and 

poor locality data for many of the species listed as indicators of either of the zones, Mansfield's two-zone 

scheme has been a workable macrofossil zonation for 

the Yorktown of Virginia.

Although the foraminifers of the Yorktown have 

been studied (see McLean, 1956, 1966, and references 

therein), no zonation based on them has been proposed. 

Ulrich and Bassler (1904), Malkin (1953), Swain (1951), 

Brown (1958), and McLean (1957, 1966) have studied 

the ostracodes, and only about 50 species occurring in 

the Yorktown have been reported by these authors. 

Malkin (1953) suggested a zonation for the Yorktown 

based on 30 species identified from 12 samples from 

three localities in the York-James peninsula area. She 

proposed two zones, a lower Hemicythere schmidtae 

Zone and an upper Hemicythere conradi Zone. Unfortunately, Malkin's zones are virtually impossible to delineate, partly because of taxonomic advances, but 

principally because she identified too few species from 

too few samples and localities.

OSTRACODE BIOSTRATIGRAPHY

Ostracodes were identified from 46 samples and 16 

localities (fig. 1). The Yorktown Formation contains a

large ostracode assemblage of 230 species. In 43 of the 

samples the species diversity was sufficiently high to 

allow sample comparison using binary similarity coefficients and cluster analysis. A discussion of the application of these techniques to biostratigraphy is in 

Hazel (1970).

Figure 2 is a Q-mode (samples compared on the basis 

of their species content) dendrogram (unweighted pairgroup method) and trellis diagram for 43 samples resulting from the calculation of Dice similarity coefficients 2C/Ni + AT2, where C = number of species in 

common between two samples, and Ni and AT2 are the 

number of species in the two samples; the similarity 

values are multiplied by 100 to remove the decimal 

point. There are three major clusters in the dendrogram, 

labeled A, B, and C. One of the samples, 31, clusters 

late; it will be discussed later. The three major clusters 

of faunally similar samples are interpreted as representing three ostracode assemblage zones here named 

from lowest to uppermost, the Pterygocythereis inexpectata Zone (cluster A), Orionina vaughani Zone (cluster B), and Puriana mesacostalis Zone (cluster C).

Correlation of certain samples within major clusters 

is not obvious from inspection of the dendrogram in 

figure 2. This is a result of environmental "noise" and 

species provinciality, because the samples within the 

clusters are spread over a wide area and may represent 

different environments. The trellis diagram of figure 2 

gives the similarities, in 20-point classes, among all the 

samples. Analysis of the trellis diagram (as well as the 

computer printout of the matrix of calculated coefficients of which the trellis diagram is a summary) and 

of the stratigraphic position of the samples results in 

the correlations suggested in figure 3.

Figure 4 is an R-mode (species compared to each 

other on the basis of the samples in which they occur) 

dendrogram for 80 of the more commonly occurring 

Yorktown species. The clusters represent groups of 

closely associated species. Opposite the endpoints in 

the dendrogram are numbers indicating the biostratigraphic fidelity (BF) and constancy (C) of that species 

for each of the proposed zonal units. Constancy is simply the percentage, expressed in tens, of samples from 

a zonal unit in which a species occurs. Biostratigraphic 

fidelity is calculated by

BF,-.t. = -^- X 10,

where j is the species (j = a, b, c . . . ri); and Pi is the 

percentage of occurrences in a biostratigraphic unit i 

(i = 1, 2, 3 ... p). The BF of a species for a particular 

biostratigraphic unit is therefore calculated by dividing
OSTRACODE BIOSTRATIGRAPHY

DICE SIMILARITY COEFFICIENT X 100

DICE COEFFICIENT 100 90

FIGURE 2. Q-mode (samples compared on the basis of the species content) dendrogram and trellis diagram 

based on calculation of Dice similarity coefficients for 43 Yorktown samples containing 230 ostracode 

species. The unweighted pair-group method was used in clustering for the dendrogram. Values in the 

trellis diagram are given in 20-point classes.

the percentage of occurrences of a species in a biostratigraphic unit by the sum of the percentage of occurrences 

of that species in all other biostratigraphic units within 

the limits of the problem. (See Hazel, 1970, for further 

discussion.) Biostratigraphic fidelity and constancy are 

expressed in tens to indicate the level of precision of the 

method and to remove the decimal point. Biostratigraphic fidelity can be considered a quantification of 

the guide-fossil concept, and the values listed in figure 

4 can be used as guides for monothetic biostratigraphic 

placement of samples. The values for C and BF may 

change as more data accumulate.

A list of the species used in the R-mode analysis is 

given in table 1. Representative specimens of the 80

species are deposited in the collections of the U.S. 

National Museum under Nos. 167376 through 167456. 

The specimens may be borrowed from the Museum for 

study.

The assemblage of the Pterygocythereis inexpectata 

Zone is smaller than those of the two upper zones; 52 

species have been identified, but relatively few of these 

characterize the assemblage. The forms with the highest 

BF and C values for this zone appear in figure 4 in the 

61-71 cluster. Species of the 22-31 cluster of figure 4 

also occur commonly in the Pterygocythereis inexpectata 

Zone, but have equal or higher values of BF for the Orionina vaughani Zone.
OSTRACODES, YORKTOWN FORMATION, VIRGINIA AND NORTH CAROLINA

o - =

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Mt.Gould, N.C. 

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Palmyra, N. C

(locality 2)

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OSTRACODE BIOSTRATIGRAPHY

Biostratigraphic fidelity

and zonal constancy

Pterygocythereis

inexpectata

Zone

BF

i

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

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0

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0

0

7

7

6

7

7

8

4

4

8

6

3

2

3

0

0

0

0

7

0

0

C

i

0

0

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0

0

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0

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0

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0

0

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0

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1

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6

4

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9

7

3

2

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3

2

2

1

0

0

0

0

3

0

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Orionina

vaughani

Zone

BF

3

2

0

0

1

1

0

2

1

2

0

0

1

2

2

7

7

7

6

10

7

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5

6

4

4

3

4

3

4

5

4

5

5

4

7

6

5

6

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4

4

4

5

6

6

3

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6

4

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4

6

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8

3

3

4

3

3

2

6

6

2

4

7

3

7

10

10

3

7

3

4

7

C

3

1

0

0

<1

<1

0

1

1

1

0

0

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2

1

5

6

5

5

5

6

8

9

9

9

9

9

9

8

7

7

8

9

8

7

9

9

8

8

7

8

6

6

7

6

5

5

3

4

5

4

3

3

3

3

3

4

2

5

4

4

3

3

4

3

2

4

3

1

2

4

3

2

2

2

1

2

1

3

2

Puriana

mesacostalis

Zone

BF

6

8

10

10

9

9

10

8

9

8

10

10

9

8

8

3

3

3

4

0

3

0

2

2

3

4

3

4

4

3

1

6

5

5

6

3

4

4

4

3

4

5

6

4

4

0

4

6

6

4

0

4

4

0

6

4

4

0

0

2

0

0

0

0

0

0

0

0

0

0

0

5

0

0

0

7

3

0

6

3

C

5

5

5

5

6

7

6

3

6

4

6

5

6

10

3

2

3

2

4

0

3

0

3

3

7

8

10

9

9

5

2

10

9

8

9

4

5

6

5

4

7

8

9

6

5

0

3

5

9

3

0

2

3

0

4

2

3

0

0

1

0

0

0

0

0

0

0

0

0

0

0

6

0

0

0

3

1

0

2

1

DICE SIMILARITY COEFFICIENT / 2C \

\N,+N2 /

X 100

100 90 80 70 60 50 40 30 20 10

FIGURE 4. R-mode (species compared with each other on the basis of the samples in which they occur) 

dendrogram (Dice coefficient; unweighted pair-group method) for the 80 Yorktown ostracode species 

that occur in five or more samples. The constancy, C, and biostratigraphic fidelity, BF, of each 

species for each zone are indicated on the left (see text for discussion). The BF and C values are 

based on the occurrences within the 43 samples used in Q-mode analysis (fig. 2); sample 31 was not 

used because it contains specimens reworked from the underlying bed (see text p. 7). The names 

and occurrences of the 80 species are shown in table 1.

415-720 O - 71 - 2
OSTRACODES, YORKTOWN FORMATION, VIRGINIA AND NORTH CAROLINA

TABLE 1. Occurrence of 84 Yorktown ostracode species that occur in four or more samples

[The species are listed in the order they appear in the It-mode dendrogram (fig. 4). The last four species were not used in the R-mode study]

Species

5 Cwhmanidea&p.I--. __ ... _ .. .. __ _ _

9 Radimella ftoridana (Benson and Coleman, 1963) __

13 Cytherurasp. N ______________ ... .....

14 "Haplocytheridea" bradyi (Stephenson, 1938). __ .

21 MueUerina sp. F ________ ___ _____

22 Radimetta eonradi (Howe and McGuirt, 1935) ......

27 Hulingsina ashermani (Ulrich and Bassler, 1904). 

37 Orionina vaughani (Ulrich and Bassler, 1904) ___ .

41 Puriana rugipunctata (Ulrich and Bassler, 1904). ...

44 Bensonocythere sp. B... _____________ ...

47 Bensonocythere sp. K. ______ . __ ..... .

49 Thaerocythere schmidtae (MaJkin, 1953).. __ . _

52 Cytherurasp. L ___________ ... .. ...

53 Cythervra howei (Puri, 1954)....... ........ 

55 Eucythere gibba Edwards, 1944 

61 Mudlerina aft. M. canadensis (Brady, 1870) ........ 

62 Adinocythereis cf. A. marylandica (Howe and Hough, 

1935) _ _ 

66 Echinocythereis planibasalis (Ulrich and Bassler, 

1904)........................................

68 Loxoconcha sp. M __________________ 

69 Bensonocythere sp. D._ ..........._....._........

71 Munayina barclayi McLean, 1957... . . . 

Samples

1

--

--

--

--

--

--

--

--

--

--

X

..

--

--

2

--

--

X

X

-'

--

--

--

X

X 

X

X 

X

3

--

--

--

X 

X 

X

X

--

--

--

X

--

--

--

--

X 

X

X

X 

X

4

X

--

X

X 

X 

X

X 

X 

X 

X

X

X 

X

X 

X

X

X

X

X

X 

X 

X

X 

X 

X 

X 

X

X

5

X

X

X 

X 

X 

X 

X 

X 

X 

X 

X 

X 

X

X

X

X

X

--

X

--

X

X 

X 

X

X 

X 

X

X

6

--

X

X 

X 

X 

X 

X 

X 

X 

X 

X 

X 

X

'-

-

X

-

X

--

-

--

X

X 

X 

X

X

X 

X

7

X

--

X

X 

X 

X

X 

X 

X 

X 

X 

X 

X

X 

X 

X 

X 

X

X 

X

X

X

--

X

X 

X 

X

8

X

X 

X 

X 

X 

X 

X

X

X

X 

X 

X 

X 

X

X 

X 

X 

X 

X 

X 

X 

X 

X

X 

X 

X

X

--

X

X

--

--

X

9

X

X 

X 

X 

X 

X 

X

X

X 

X 

X 

X 

X

X 

X 

X 

X 

X 

X 

X 

X

X 

X

X

--

X

y

--

--

--

X

10

X

X 

X 

X 

X 

X 

X

--

X 

X 

X 

X 

X

X

X 

X 

X 

X 

X 

X

X 

X

--

--

--

--

--

11

--

X 

X 

X 

X 

X

--

--

--

X

X

--

-

X

X

X

12

--

X 

X

X

X

X 

X

--

--

--

--

-

-

--

-

X

X

X

X

--

13

X

X

X 

X 

X 

X 

X 

X

X 

X 

X 

X

X

--

X 

X

X

X

--

--

14

X

--

X 

X 

X 

X 

X 

X 

X 

X 

X 

X

X 

X 

X 

X

X

--

X

--

X

15

X

X

--

X 

X

X

X 

X 

X

--

--

X 

X 

X

X

X

--

--

--

X

16

X 

X 

X 

X 

X 

X

X

X

--

X

X 

X 

X

X 

X

X

--

X

X 

X

X

X

X

--

X

--

--

17

X 

X 

X 

X 

X 

X

X

X

X

--

X 

X 

X 

X 

X 

X

X 

X

X

--

-

X

X 

X

X 

X 

X

--

--

--

--

X

X

18

X 

X 

X 

X 

X 

X 

X 

X 

X

X

--

--

X 

X 

X 

X 

X 

X

X 

X 

X 

X

X 

X 

X 

X 

X 

X 

X 

X

X

X

X

--

--

X

X 

X

19

X 

X 

X 

X 

X 

X 

X 

X 

X

X 

X

X

X

X

X 

X 

X 

X 

X 

X

X 

X 

X 

X

X 

X

X 

X 

X 

X 

X 

X

X 

X 

X

X

--

--

--

--

X 

X

20

X 

X 

X 

X 

X

X

X

--

X

X

X 

X

X 

X 

X 

X

X 

X 

X 

X 

X 

X 

X 

X 

X

X

X

--

--

--

--

X

X

21

--

--

X 

X

X 

X 

X 

X 

X

X

X

--

--

X 

X

X 

X

X

X

X

22

--

--

X

X

X 

X

--

--

;;

--

--

X 

X

X 

X 

X

X

X

23

--

--

X 

X 

X 

X

X 

X

--

--

--

--

--

X

X 

X 

X

--

--

24

--

-

X 

X

X 

X 

X

X 

X 

X

--

--

X 

X

X 

X

--

X

X 

X 

X 

X

X

X

X

X

25

--

--

--

X 

X

X

--

--

--

X

X

--

--

X 

X

X 

X

--

26

--

--

--

__

--

--

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XX V
OSTRACODE BIOSTRATIGRAPHY

Deposits considered to be in the Pterygocythereis inexpectata Zone include (fig. 3) the lower 10 feet of Yorktown at the Lee Creek open-pit mine on the Pamlico 

River, N. C. (loc. 1, p. 10) (also see Gibson, 1967); the 

fossiliferous beds overlying the granite at Halifax, N. C. 

(loc. 5); at least the lowermost bed of the Yorktown on 

the Roanoke River near Palmyra Landing, N. C. (loc. 

2); and the lower beds of the Yorktown on the James 

River near Mount Pleasant, Va. (loc. 13). The Pterygocythereis inexpectata Zone is approximately equivalent 

to the Pecten clintonius Zone of Mansfield (in Gardner, 

1943). However, some of the beds along the York and 

James Rivers assigned by Mansfield to the upper part 

of his Pecten clintonius Zone contain ostracode assemblages referable to the lower part of the Orionina 

vaughani Zone, for example, the beds assigned by Malkin (1953) to her Hemicythere schmidtae Zone.

Ostracodes are abundant and diverse in the Orionina 

vaughani Zone; 160 species have been identified from the 

21 samples assigned to this zone. The large cluster in 

figure 4 from species 16 through 60 contains forms 

which have high BF and C values for this zone.

In North Carolina the Orionina vaughani Zone assemblage occurs in the Lee Creek mine from about 13 feet 

to at least 33 feet above the base of the Yorktown 

(material from the interval between 33 and 53 ft above 

the base of the Yorktown could not be collected when 

the mine was visited in June 1969). All the samples 

studied from the Yorktown of Virginia except 31 and 41 

are assigned to the Orionina vaughani Zone. Malkin's 

(1953) samples from the area of the type Yorktown 

can be assigned to the Orionina vaughani Zone on the 

basis of the BF values for the species she lists.

In Virginia the Orionina vaughani Zone approximates 

the Turritetta alticostata Zone of Mansfield with some 

important differences. Mansfield (in Gardner, 1943) indicated that Yorktown beds at Suffolk and near Franklin (his Bigg's Farm locality) were the youngest Yorktown in Virginia. He correlated these beds with the 

Yorktown in the Colerain and Mount Gould areas on 

the Chowan River in North Carolina. In the present 

study the subaerially out-cropping beds at Colerain 

Landing as well as those at Mount Gould Landing are 

considered younger than any of the Yorktown of Virginia, except for that represented by sample 31. MacNeil (1938) on the basis of the distribution of certain 

Noetinae (bivalves) also concluded that the Chowan 

River, N. C., beds are younger than any of the Yorktown of Virginia.

The 1-15 cluster in figure 4 contains species with high 

BF and C values for the Puriana mesacostalis Zone. In 

addition, the 16-60 cluster contains many species with 

high C values for this zone. In the Puriana mesacostalis 

Zone are placed the beds in the bluffs on the Chowan

River at Mount Gould Landing (loc. 4) and at Colerain 

Landing (loc. 3), at least the upper 12 feet of the Yorktown at the Lee Creek open-pit mine (fig. 3), and sample 

31. Sample 31 was collected in a borrow pit near Yadkin, 

Va. (loc. 8), from an unconsolidated to indurated 3- 

foot-thick unit of dark-red iron-stained clayey sand 

containing sparse unstained clayey sand beds. The ironstained unit occurs stratigraphically below the marine 

Norfolk Formation (Pleistocene) (as used by Oaks and 

Coch, 1963; Oaks, 1964) and contains hematite nodules, 

indurated mudballs, much comminuted shell, whole 

specimens of the bivalve Corbicula densata (Conrad, 

1843), and 37 species of Ostracoda. Underlying this 

unit are exposed at least 10 feet of blue clayey sand 

packed with broken and whole mollusks (sample 30, 

placed in the Orionina vaughani Zone). Spencer and 

Rogers (1969) place the iron-stained bed in the basal 

Pleistocene and the blue fossiliferous clayey sand in 

the Yorktown.

The comminuted shell in the iron-stained bed is 

probably reworked from the underlying blue fossiliferous sand. Several of the ostracode specimens also 

appear to be reworked. The assemblage is a mixture of 

species that occur in both the Orionina vaughani and 

Puriana mesacostalis Zones with species otherwise restricted to either the Orionina vaughani or Puriana 

mesacostalis Zones. This is reflected in the late clustering 

of sample 31 in figure 2.

Five species occur in sample 31 that are known only 

from the Orionina vaughani Zone. Two of these occur 

commonly in that zone and in the blue fossiliferous beds 

below the iron-stained bed (sample 30); one of these 

species is represented in sample 31 by a single specimen 

and the other by three specimens. The presence of these 

species in sample 31 probably represents reworking from 

the beds below. The other three species occur rarely in 

the Orionina vaughani Zone in assemblages judged to 

represent environments similar to that of sample 31 

(samples 38 and 45, for example) and therefore may 

very well be part of the natural assemblage of the sample.

Also present in sample 31 are species such as Puriana 

mesacostalis (Edwards, 1944) (species 4), Bensonocythere 

sp. M (species 3), and Radimetta confragosa (Edwards, 

1944) (species 12) which are common in and restricted 

to the Puriana mesacostalis Zone and younger levels. 

The samples with which sample 31 has the highest similarity values are those from the Puriana mesacostalis 

Zone on the Chowan River (samples 16, 17). The ironstained bed is considered part of the Puriana mesacostalis Zone and not of Pleistocene age (so placed by Spencer and Rogers, 1969). This interpretation is corroborated by the presence of Corbicula densata which is not 

known to occur in deposits as young as Pleistocene
8 OSTRACODES, YORKTOWN FORMATION, VIRGINIA AND NORTH CAROLINA

(Gardner, 1943). The bed is the youngest Yorktown 

yet found in Virginia.

The nature of the contact between the iron-stained 

Corbicula-bearing bed and the blue bioclastic beds suggests a disconformity. If the biostratigraphic placement 

of samples 30 and 31 (fig. 3) is correct, the contact represents the upper part of the Orionina vaughani Zone 

and lower part of the Puriana mesacostalis Zone, suggesting erosion occurred during this time.

As mentioned above, it is this contact that Spencer 

and Rogers (1969) selected as the Yorktown-Pleistocene contact and presumably mapped in the subsurface 

of Norfolk County, Va. The northwest-southeast trending flexure which they consider the cause of the thinning 

of the "Pleistocene" in the Yadkin area may be the 

structural control for the disconformity within the 

Yorktown. See also the discussion of structural features 

by Oaks (1964, p. 70-80).

AGE OF THE YORKTOWN FORMATION

The Yorktown Formation has traditionally been considered the youngest Miocene unit in the Middle Atlantic Coastal Plain (Cooke and others, 1943). However, 

virtually no benthonic species which allow correlation 

with the late Miocene (Tortonian-Messinian) of the 

type areas in Italy occur in the Yorktown. Diagnostic 

planktonic foraminifers are rare in the Yorktown because most of the beds represent shallow water deposition under temperate conditions. However, Gibson 

(1967) reports a late Miocene planktonic foraminiferal 

assemblage from beds here assigned to the Pterygocythereis inexpectata Zone at the Lee Creek mine in North 

Carolina. Diagnostic foraminifers from other parts of 

the Yorktown are not known.

As pointed out above, Mansfield (in Gardner, 1943) 

correlated the upper part of his Turritella alticostata 

Zone of Virginia (this zone is approximately equivalent 

to the Orionina vaughani Zone) with the Yorktown exposed on the Chowan River near Colerain and Mount 

Gould, N. C. However, because the ostracode assemblages indicate that the latter deposits are clearly 

younger than those of the Yorktown of Virginia, except 

for that represented by sample 31, they are placed in 

the Puriana mesacostalis Zone,

The Puriana mesacostalis Zone is therefore younger 

than Yorktown deposits traditionally considered late 

Miocene in age; it is here tentatively considered to be of 

early Pliocene age. Even this heterodox view of the age 

of the Yorktown and its correlatives may be conservative. The occurrences of certain mollusks and ostracodes 

indicate that the Jackson Bluff Formation of Puri and 

Vernon (1964), containing the Ecphora and Cancellaria 

Zones, of western Florida is correlative with the upper 

Yorktown of Virginia (Orionina vaughani Zone). The

matrix from inside a bivalved specimen of Dosinia acetabulum (Conrad, 1832) collected from the type locality 

of the Ecphora Zone at Alum Bluff on the Apalachicola 

River (the specimen is from bed 4 of Puri and Vernon, 

1964, p. 204; USGS 2210) has yielded the following 

planktonic foraminifers (identified by Ruth Todd, U.S. 

Geological Survey):

Globigerina bulloides apertura Cushman, 1918

G. dutertrei d'Orbigny, 1839

Globigerinoides quadrilobatus sacculifer (Brady, 1879)

G. quadrilobatus trilobus (Reuss, 1850)

G. ruber (d'Orbigny, 1839)

Globorotalia acostaensis pseudopima Blow, 1967

G. miocenica Palmer, 1945

Sphaeroidinellopsis subdehiscens (Blow, 1959)

Turborotalita quinqueloba (Natland, 1938)

This assemblage suggests that the Ecphora Zone 

should be assigned to Blow's (1969) planktonic zones 

N18 or N19. The lower part of N18 is considered by 

Blow to be upper Miocene (Messinian); upper N18 and 

N19 are lower Pliocene (Zanclian). Thus, it may be 

that the upper Miocene-lower Pliocene boundary in 

the Atlantic and Gulf Coastal Plain eventually will be 

revised further downward to include in the Pliocene 

more of the deposits that have been traditionally assigned to the upper Miocene.

PALEOGEOGRAPHY

The ostracode genera Cyprideis and Perissocytheridea 

are primarily inhabitants of brackish water (see Sandberg, 1964a, b, Morkhoven, 1963). Also a brackish water 

inhabitant is the late Miocene-Holocene species Cytheromorpha curta Edwards, 1944. (See Darby, 1965). Modern species of the bivalve Corbicula live in fresh to brackish habitats (Zhadin, 1952,1965). In upper Miocene and 

Pliocene deposits of the Atlantic Coastal Plain, this 

genus is represented by Corbicula densata (Conrad, 

1843). Thus, in fossil assemblages the presence of the 

bivalve Corbicula or of the ostracodes listed above, particularly Cyprideis, indicates reduced salinity or at least 

proximity to a brackish water environment from which 

specimens could be transported into shallow marine 

habitats. Therefore, the presence of such forms as Cyprideis and Corbicula in fossil assemblages indicates nearness to shore.

Specimens of Cyprideis, Perissocytheridea, and Cytheromorpha curta occur in seven of the Yorktown samples studied. Corbicula densata occurs with these forms 

at four of the localities and has been reported from near 

the fifth locality.

The oldest Yorktown sample containing Cyprideis is 

No. 23 from Halifax, N. C. (loc. 5). Here the Yorktown 

overlies granitic basement, and sample 23 was collected
PALEOGEOGRAPHY

about 4 feet above the base of the Yorktown. There is 

about 40 feet of Yorktown exposed at locality 5, but 

only in the lower few feet are microfossils preserved.

Two species of Cyprideis occur in sample 38 from 

Lieutenant Run at Petersburg, Va. (loc. 12). Corbicula 

densata was originally described from Petersburg by 

Conrad (1843), but the exact locality is unknown.

Cyprideis, Perissocytheridea, Cytheromorpha curta, and 

Corbicula densata occur in sample 44 at Williamsburg 

(loc. 15).

Cyprideis, Cytheromorpha curta, and Corbicula densata 

occur together in the iron-stained bed in the borrow pit 

near Yadkin, Va. (sample 31 at loc. 8).

Sample 19 at locality 4 on the Chowan River contains 

Cyprideis; Corbicula densata was found in the same bed.

Cyprideis is present in sample 10 from the uppermost 

fossiliferous beds of the Yorktown at the Lee Creek 

mine; Corbicula densata occurs here also.

The geographic positions of the Cyprideis-Corbiculabearing samples are shown in figure 5. Their biostratigraphic positions are indicated in figure 3. These 

Cyprideis-Corbicula points are interpreted to represent 

approximate positions of the shoreline of the Yorktown 

sea.

Figure 6 shows the postulated general regional trend 

of the Yorktown transgression and regression. The 

Cyprideis-Corbicula points are plotted against the biostratigraphy (fig. 3) and the distance normal to the 

inferred depositional strike of about N. 20°-25° E., 

based on the azimuth of the inner edge of the outcrop 

belt. Positions of samples from Yorktown beds that 

immediately overlie older formations are also plotted; 

these are useful in delineating the pattern of transgression. The plane of figure 6 is normal to the inferred 

depositional strike.

The basal 1 foot of the Yorktown at the Lee Creek 

mine (loc. 1) contains quartz pebbles and cobbles, phosphate blocks, and cetacean bones. As Gibson (1967) 

points out, this bed represents a basal transgressive conglomerate. Placopecten clintonius and Pterygocythereis 

inexpectata are found in this bed of the Yorktown. This 

is the farthest downdip that the base of the Yorktown 

can be seen in outcrop; the contact with the underlying 

Pungo River Formation (middle Miocene) is about 100 

feet below present sea level.

A Yorktown bed of middle Pterygocythereis inexpectata 

Zone age overlies the Cretaceous near Palmyra Landing, 

N. C. (loc. 2), at about 20 feet above sea level. At Halifax, N. C. (loc. 5), 50 feet above sea level, a bed considered the same age as that near Palmyra Landing overlies Paleozoic (?) granite. Cyprideis occurs in sample 23 

about 4.0 feet above the granite. The shoreline was 

probably never very far west of this area during the

34°

0 i i

25 50 75 100 MILES 

_J I

0 25 50 75 100 KILOMETERS

FIGURE 5. Location of samples containing brackish-water elements, particularly Cyprideis (all samples indicated) and Corbicula (samples 10, 19, 31, 44). It is inferred that the shoreline of 

the Yorktown sea was very near these localities when the deposits represented by these samples were laid down.

time characterized by the Pterygocythereis inexpectata 

Zone.

At Petersburg, Va., beds of the middle Orionina 

vaughani Zone overlie St. Marys Formation and contain species of Cyprideis. The shoreline was no doubt 

nearby to the west. The maximum Yorktown transgression was during the time of the middle Orionina 

vaughani Zone, probably at about the time represented 

by the middle part of the Yorktown exposure at Petersburg. The Yorktown beds at Petersburg are about 100 

feet above sea level.

The Yorktown at the Trego Quarry (loc. 6) overlies 

granite at about 100 feet above sea level. The only sample yet processed from this locality may also be from the

415-720 O - 71 - 3
10 OSTRACODES. YORKTOWN FORMATION, VIRGINIA AND NORTH CAROLINA

DISTANCE, IN MILES, NORMAL TO DEPOSITIONAL STRIKE 

0 10 20 30 40 50 60 70 80

19 (+10) 

Cy.Co .

10 (-30) 

Cy,Co

.31 (-5) 

Cy,Cc,Co

Cy,Cc,P,Co

38 ( + 100) 

* Cy,?Co

23,(+54)

Cy 41 (+30)

 

21 (+50)"

11 (+20)

1 (-100)

FIGURE 6. General trend through time of the Yorktown transgression and regression. The plane of the figure is normal to the 

inferred general depositional strike of N. 20°-25° E. Samples 

(10,19, 31, 44, 38, 23) containing brackish Water ostracodes and 

Corbicula are plotted against the distance between the samples 

normal to the depositional strike and their biostratigraphic position (fig. 3). Also plotted are samples (1, 11, 21, 41) from Yorktown beds that immediately overlie older formations. The numbers within the parentheses indicate feet above or below present 

sea level. The abbreviations Cy, Co, P, and Cc stand for Cyprideis, Corbicula, Perissocytheridea, and Cytheromorpha curia 

(Edwards, 1944), respectively.

middle Orionina vaughani Zone. However, it clusters 

late (see fig. 2), and its exact position within the zone is 

equivocal.

Cyprideis-Corbicula-bearmg beds marking the regression of the Yorktown sea are present at Williamsburg, 

Va. (loc. 15), Yadkin, Va. (loc. 8), Mount Gould Landing, N. C. (loc. 4), and the Lee Creek mine (loc. 1). 

The Williamsburg sample represents the Orionina vaughani Zone; the last three samples represent the Puriana 

mesacostalis Zone.

The disconformity within the Yorktown at Yadkin, 

Va., (see p. 8) indicates that at least locally the sea 

readvanced over an eroded middle Yorktown surface 

during early Pliocene time.

LOCALITIES

Locality 1. Open-pit phosphate mine of the Texas Gulf Sulphur 

Co. on south shore Pamlico River at mouth of Lee Creek near 

Aurora, Beaufort County, N. C. (see Gibson, 1967). The following section was collected in the southwestern part of the pit in 

June 1968.

Unit and description

Thickness 

(feet)

Pleistocene:

10. Buff crossbedded sand._______________________ 10.0

Yorktown Formation:

9. Blue clayey sand, weathered; no macrofossils;

microfossil sample barren__________________ 2.0

8. Blue clayey sand; macrofossils very common; 

Corbicula densata present in upper part; sample 8 

(TJSGS 24886) in lower 1.0 ft, sample 9 (TJSGS 

24887) taken 7.0 ft above base, sample 10 

(TJSGS 24888) in upper 0.5 ft of unit. _________ 11.0

7. Covered or otherwise inaccessible_____________ 23.0

6. Bluish-gray clayey sand; Turritella molds and 

casts in lower 6 ft; sample 7 (TJSGS 24885) collected 10.0 ft above base; barren microfossil 

samples collected 1.0 ft and 5.5 ft above base.__ 13.0

5. Blue clayey sand, indurated; many Turritella___ 3.0

4. Blue clayey sand; Pecten and Turritella; contact 

with underlying unit irregular; sample 6 (TJSGS 

24884)____________________________________ l.O

3. Blue clayey sand; phosphate and quartz pebbles 

in lower part; macrofossils present; burrows in 

upper 1.0-2.0 ft; sample 5 (TJSGS 24883) in 

upper 0.5 ft between burrows; sample 4 (TJSGS 

24882) collected 12.0 ft above base; sample 3 

(TJSGS 24881) 7.0 ft above base; sample 2 

(TJSGS 24880) in lower 10 ft__-______________ 14.0

2. Blue clayey sand; phosphate pebbles and quartz 

cobbles and pebbles; bone; macrofossils, including Placopecten clintonius and Mercenaria; sample 1 (TJSGS 24879)._..________.___..___.__. 2.0

Pungo River Formation:

1. Phosphatic sands and diatomaceous clay________ 43.0

Total exposed__________________________ 122.0

Locality 2. Bluff on right bank of Roanoke River about 1.25 

miles below the landing 1.0 mile east of Palmyra, Halifax 

County, N. C. Sample 11 (TJSGS 24889) from blue clayey sand 

with Pecten in basal 1.0 foot of the Yorktown Formation where 

it overlies a 3-foot indurated sand containing fossil logs in the 

upper part. Collected by T. G. Gibson and Charles Buddenhagen, November 1965.

Locality 8. Landing at Colerain, Bertie County, N. C. About 16 

feet of Yorktown is exposed in bluffs 100-200 yards south of 

Colerain Beach Club, right (west) bank of Chowan River. In 

addition, in June 1969 a spoil pile of fossiliferous sediment (unit 

1 below) was present at a Mr. White's cabin. This material was 

collected by Mr. White from the river bottom some distance offshore at low spring tide after several days of offshore winds; it is 

not knowta how far stratigraphically this is below the base of 

the subaerial outcrop.

Thickness 

Unit and description (feet)

Pleistocene:

7. Sand, crossbedded-___________________________ 25.0

Yorktown Formation:

6. Clayey sand; weathered buff; macrofossils present;

Corbicula densata and Mercenaria present- _____ 6.0 

5. Clayey sand; weathered buff in upper part, mottled

in lower part; Pecten and Mercenaria present;

sample 15 (TJSGS 24892) taken 4 ft above base_ _ 6.0 

4. Greenish blue clayey sand; macrofossils present;

sample 14 (TJSGS 24891)______________.___._ 1.5
LOCALITIES 11

Thickness 

Unit and description (feet)

3. Greenish-blue clayey sand; macrofossils very common; Glycymeris and Pecten common; bed is at 

water level; sample 13 (USGS 24890) _________ 1.0

2. Normally below water level__________________ ?

1. Greenish-blue clayey sand; macrofossils very common; spoil collected from river bottom (see 

above); sample 12 (USGS 24911)___________._ ?

Total exposed__________________________ 39.5

Locality 1*. One-half mile below landing at Mount Gould, 

Bertie County, N. C.; bluffs on right (west) bank of Chowan 

River.

Thickness 

Unit and description (feet)

Pleistocene:

4. Sand, crossbedded-__.___-__________-__--_.___ 15.0

Yorktown Formation:

3. Gray to buff clayey sand; shell fragments.______ 1.0

2. Buff, clayey sand, slightly weathered; macrofossils 

very common; Pecten, Glycymeris, Corbicula 

densata, corals; sample 20 (USGS 24897) (from 

upper 1.0 ft; sample 19 (USGS 24896) 3.0 ft 

above base; sample 18 (USGS 24895) 1.5 ft 

above base_-_-__-____--___-_--__-__-______ 4.5

1. Green to buff mottled clayey sand; scattered shell 

fragments; sample 17 (USGS 24894) in upper 

1.0 ft; sample 16 (USGS 24893) in lower 1.0 ft_. 4.0

Total exposed__________________________ 24.5

Locality 5. Banks of a northward flowing tributary to Quankey 

Creek, north side of North Carolina route 561 0.5 mile west of 

railroad crossing over route 561 in Halifax, Halifax County,

N. C.

Thickness 

Unit and description (feet)

Pleistocene:

13. Sand _._ - __ - 6.0

Yorktown Formation:

12. Gray, clayey sand, unfossiliferous______________ 7.0

11. Greenish-gray clayey sand; casts and molds of 

aragonitic mollusks; scattered oysters and 

pectenids; elongated concretions in lower 2.0 ft; 

microsamples barren.______________________ 7.5

10. Clayey sand; indurated; macrofossils present;

forms waterfall---------------------------- 1.0

9. Greenish-gray clayey sand; scattered macrofossils; sample 26 (USGS 24903) 5.0 ft above base. 11.0 

8. Blue clayey sand; macrofossils very common;

sample 25 (USGS 24902)_-.__.__.. . _.__ 2.0 

7. Covered------------------------------------ 2.0

6. Blue clayey sand; macrofossils very common;

sample 24 (USGS 24901)._._-_._._.__ - 2.0 

5. Covered______--_-_____--____-__-_--_-_--- 1.5

4. Blue clayey sand; macrofossils very common;

sample 23 (USGS 24900)-_--_-___--____---- 2.0

3. Covered _ -__ . - 2.0 

2. Buff clayey sand; macrofossils very common; 

sample 22 (USGS 24899) in upper 1.0 ft and 

sample 21 (USGS 24898) in basal 0.5 ft_ - _ _ - _ 2.0 

Paleozoic (?):

1. Buff granite-.-.-.-------_..._._._.__.__ 2.0

Total exposed-__...____..___-._____. 48.0

Locality 6. Trego Stone Corporation quarry, 2.0 miles west of 

Skippers, Greenville County, Va. Sample 27 (USGS 24830) from 

upper 1.0 foot of 7.0-foot-thick outcrop of clayey sand with 

macrofossils, west side of road into quarry. Sample collected by 

Druid Wilson and Warren Blow.

Locality 7. Bluff on right (south) bank of Nansemond River, 

0.5 mile downstream from Virginia Routes 10 and 32 bridge, 

about 500 feet northwest of cemetery, city of Suffolk, Va.; about 

13 feet of Yorktown exposed near south end of outcrop. Sample 

28 (USGS 24811) from greenish-blue clayey sand in lower 0.5 

foot of exposure; sample 29 (USGS 24814) from buff clayey sand 

about 11.5 feet above beach. Samples collected by Richard H. 

Bailey and Warren Blow.

Locality 8. Borrow pits 0.5 mile southwest of Yadkin, Virginia, 

and 0.3 mile south of Norfolk and Western Railroad near intersection of Portsmouth Ditch and powerlines; U.S. Geological 

Survey Norfolk South 7 ^-minute quadrangle map, 1965; 

lat. 36°45'30" N., long. 76°22'00" W. Section measured in cut 

between north and south pits and in north pit.

Unit and description

(?) Sand Bridge Formation (of Oaks and Coch, 1963; Oaks, 1964):

4. Sand, crossbedded; clay and peat interbeds__--_- 4.0 

Norfolk Formation (of Oaks and Coch, 1963; Oaks, 1964):

3. Gray clayey sand; macrofossils present; ironcemented concretions and cobbles in lower part; 

bed with many Ensis in upper part-__________ 7.5

Yorktown Formation:

2. Red clayey sand; variably iron cemented; hematite 

nodules and indurated mudballs present; many 

worn broken shells; well-preserved bivalved 

specimens of Corbicula densata; contact with 

underlying unit irregular; sample 31 (USGS 

24905)-..-. ___-_ -__ .--. . _ 3.5

1. Blue clayey sand; macrofossils very common, unit 

packed with broken and whole mollusk shells; 

sample 30 (USGS 24904) in upper 4.0 ft---___- 10.0

Thickness 

(feet)

Total exposed,---_-----_-_.____-_-----___ 25.0

Locality 9. Lone Star Cement Co. open-pit mine, 0.5 mile north 

of Chuckatuck, Nansemond County, Va. Sample 32 (USGS 

24622) collected from very fossiliferous clayey sand 12.0 feet 

below present land surface and 2.5 feet below Pleistocene, west 

wall, 150 yards from northwest corner (in December 1967) 

of pit. Collected by Warren Blow.

Locality 10. Vertical 9.0 to 10.0 foot exposure of Yorktown 

Formation overlain by Pleistocene on south bank of ravine approximately 0.45 mile northwest of Tormentor Creek; 150 feet 

east of smaller of two abandoned Lone Star Cement Co. pits and 

0.2 mile south of Virginia Route 673, Isle of Wight County, Va.; 

U.S. Geological Survey Mulberry Island 7^-minute quadrangle 

map, 1965. Sample 33 (USGS 24823) collected 0.5 feet below 

top of Yorktown in brown sandy shell hash. Section measured 

and collected by Brian Dyer and Warren Blow.

Locality 11. Pit belonging to Mr. William Rice, just north of 

intersection of Fox Hill and Harris Creek Roads, Hampton City, 

Va.; U.S. Geological Survey Hampton 7^-minute quadrangle 

map, 1965. Section measured and collected by Warren Blow, 

Brian Dyer, and T. R. Waller.

Unit and description

Thickness 

(feet)

Pleistocene:

Sand and gravel. 6.0
12 OSTRACODES, YORKTOWN FORMATION, VIRGINIA AND NORTH CAROLINA

Unit and description

Thickness

(feet)

Yorktown Formation:

Buff to gray clayey sand; becoming more clayey and 

less fossiliferous toward bottom of pit; concentration 

of Ensis 1.5-2.5 ft below top; sample 37 (USGS 24805) 

from matrix inside delphinapterid whale skull collected just below Ensis bed; sample 36 (USGS 24907) 

about 7.0 ft below top; sample 35 (USGS 24906) about 

15.0 ft below top; sample 34 (USGS 24810) from 

matrix inside Echinocardium about 30.0 ft below top 

and 4.5 ft above bottom of pit-_----__-__-___---_- 34.0

Total exposed--_--_---___--------____------ 40.0

Locality 12. Banks of Lieutenant Run, a northeast-to northflowing tributary to the Appomattox River, in southern Petersburg, Va.; fossiliferous beds are east of the railroad crossing over 

Lieutenant Run and east and north of West Clara Drive, immediately behind (north) of houses on Marshall Court and 

Field Court.

Thickness 

Unit and description (feet)

Yorktown Formation:

4. Blue clay; casts and molds of mollusks, including

Yoldia; microfossil sample barren _____________ 3.0

3. Blue clayey sand with scattered blebs of clay

(possibly cross sections of burrows)___________ .5

2. Gray clayey sand; macrofossils very common; 

more clay toward top; Panopea in living position; sample 40 (USGS 24910) in very clayey 

sand in upper 1.0 ft of unit; sample 39 (USGS 

24909) collected 6.0 ft above base; sample 38 

(USGS 24908) collected 1.5 ft above base; contact with underlying unit irregular, with sediment of this unit filling burrows of underlying 

unit______________________________________ 10.0

St. Marys Formation:

1. Greenish-gray clayey sand grading downward to 

greenish-gray sandy clay; scattered macrofossils 

in upper 6.0 ft_____________________________ +6.0

Total exposed__________________________ +19.5

Locality IS. Right (south) bank of James River, first cliff exposure east of first low-lying point of land 1800 feet west of the 

colonial home on the Mount Pleasant Estate; 2.7 miles west of 

Jamestown, Va., lat. 37°12'20" N., long., 76049'50" W. U.S. 

Geological Survey Surry 7J^-minute quadrangle map, 1965; 

sample 41 (USGS 24717) from buff clayey sand about 26 feet 

above beach in lower Yorktown just above bed of Isognomen in 

St. Marys Formation. Sample collected by Warren Blow.

Locality 14.. Left (north) bank of James River at Camp 

Wallace Military Reservation, James City County, Va.; see U.S. 

Geological Survey Hog Island 7j^-minute quadrangle map, 

1965. The sample (42, USGS 24912) from this locality was from 

a slightly glauconitic gray clayey sand matrix adhering to mollusks in the S. F. Blake collection of the U.S. National Museum. 

The exact stratigraphic and geographic location are unknown; 

the lithology is similar to that of the lower beds of the Yorktown at nearby Carters Grove described by Malkin (1953, 

p. 763).

Locality 15. Campus of the College of William and Mary, 

Williamsburg, Va.; outcrop is at southeastern face of small knoll

in 15.0-foot-deep gully about 50.0 feet north of road which is 

normal to and directly behind center of west wall of Gary 

Stadium. Sample 45 (USGS 24819) from upper 1.0 foot of Yorktown in buff to orange fossiliferous coarse sand below contact 

with Pleistocene (?) sand with pebbles and cobbles; sample 44 

(USGS 24820) of same lithology from 2.0-3.0 feet below top of 

Yorktown. Corbicula densata and Rangia are present in the interval from which samples 45 and 44 were collected. Sample 43 

(USGS 24821) collected 4.5 feet below sample 44 in fossiliferous 

brownish-gray clayey sand. Collections made by Richard H. 

Bailey and Warren Blow.

Locality 16. Left (north) bank of Piankatank River 0.25 mile 

above mouth of Cores Creek, Middlesex County, Va. U.S. 

Geological Survey Wilton and Deltaville 7>£-minute quadrangle 

maps, 1964. Section measured and collected by L. W. Ward.

Unit and description

Thickness 

(feet)

Pleistocene:

3. Sand, mostly covered.--------________--______ 10.0

Yorktown Formation

2. Sandy coquina, partly indurated; shells broken;

sample 46 (USGS 24801)_________.__________ 2.0

1. Sand; macrofossils very common_______________ 3.0

Total exposed_-__-_______________________ 15.0

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REFERENCES 13

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U. S. GOVERNMENT PRINTING OFFICE : 1971 O - 415-720