Stratigraphic Revision of 

Upper Miocene and 

Lower Pliocene Beds 

of the Chesapeake Group, 

Middle Atlantic Coastal Plain

GEOLOGICAL SURVEY BULLETIN 1482-D

Stratigraphic Revision of 

Upper Miocene and 

Lower Pliocene Beds 

of the Chesapeake Group, 

Middle Atlantic Coastal Plain

By LAUCK W. WARD and BLAKE W. BLACKWELDER

CONTRIBUTIONS TO STRATIGRAPHY

GEOLOGICAL SURVEY BULLETIN 1482-D

UNITED STATES GOVERNMENT PRINTING OFFICE, WASHINGTON: 198.0
UNITED STATES DEPARTMENT OF THE INTERIOR 

CECIL D. ANDRUS, Secretary

GEOLOGICAL SURVEY 

H. William Menard Director

Library of Congress Cataloging in Publication Data

Ward, Lauck W

Stratigraphic revision of upper Miocene and lower Pliocene beds of the Chesapeake 

group-middle Atlantic Coastal Plain.

(Contributions to stratigraphy) (Geological Survey bulletin ; 1482-D) 

Bibliography: p.

Supt. of Docs. no. : I 19.3:1482-D

1. Geology, Stratigraphic-Miocene. 2. Geology, Stratigraphic-Pliocene. 3. GeologyMiddle Atlantic States. I. Blackwelder, Blake W., joint author. II. Title. III. Series. IV. 

Series: United States.

Geological Survey. Bulletin ; 1482-D.

QE694.W37 551.7'87'0975 80-607052

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

Washington, D.C. 20402
CONTENTS

Abstract __ 

Introduction

ILLUSTRATIONS

Page

Dl

1

Acknowledgments ____________________________ 4

Discussion ____________________________________ 4

Chronology of depositional events ______________________ 7

Miocene Series _________________________________ g

Eastover Formation ___________________________ 8

Definition and description ___________________ g

Stratigraphic relationships __________________ 12

Claremont Manor Member ___________________ 12

Cobham Bay Member ______________________ 19

Pliocene Series _________________________________________ 28

Yorktown Formation __________________________ 28

Previous work __________________________ 28

Redefinition and description _________________ 29

Stratigraphic relationships __________________ 29

Paleogeography _________________________ 31

Age and correlation ______________________ 31

Paleoenvironment ________________________ 32

Sunken Meadow Member ____________________ 32

Rushmere Member __________________________ 35

Morgarts Beach Member ____________________ 40

Moore House Member _____________________ 43

Summary of depositional and structural history _____________ 4g

Locality register __________________________________ 54

References cited ________________________________

[Plates follow "References Cited"]

Plate 1. Mollusks from the Claremont Manor Member.

2. Mollusks from the Cobham Bay Member.

3. Mollusks from the Cobham Bay Member.

4. Mollusks from the Sunken Meadow Member.

5. Mollusks from the Rushmere, Morgarts Beach and Moore House 

Members.

Ill
IV CONTENTS

Page 

Figure 1. Selected outcrops that are listed in the "Locality Register"

D2

2. Correlation chart showing stratigraphic relationship 

of the members of the Eastover and Yorktown 

Formations __________________________ 3

3. Location of type section of the Eastover Formation ___ 9

4. Type locality of Eastover Formation ____________ JQ

5. Location of the type section of the Claremont Manor 

Member of the Eastover Formation and the Sunken 

Meadow Member of the Yorktown Formation _____ 13

6. Type locality of the Claremont Manor Member, 

Eastover Formation, and of the Sunken Meadow 

Member, Yorktown Formation ______________ 14

7. Basin configuration of the Claremont Manor Member,

Eastover Formation ____________________ 17

8. Location of the type section of the Cobham Bay

Member, Eastover Formation _______________ 20

9. Type locality of the Cobham Bay Member, Eastover

Formation __________________________ 21

10. Basin configuration of the Cobham Bay Member,

Eastover Formation ____________________ 26

11. Yorktown Formation overlying laminated clays of the

Eastover Formation 30 12. Piankatank River, Va., near Martiau showing shelly

beds of the Sunken Meadow Member ___________ 33

13. Extent of outcrops of the Sunken Meadow Member of

the Yorktown Formation _________________ 34

14. Location of Yorktown Formation lectostratotype 

near Rushmere, Isle of Wight Co., Va. Type 

locality of the Rushmere Member ____________ 36

15. Lectostratotype of the Yorktown Formation and type

locality of the Rushmere Member ____________ 37

16. Extent of outcrops of the Rushmere and Morgarts

Beach Members of the Yorktown Formation ______ 39

17. Location of the type section of the Morgarts Beach

Member, Yorktown Formation __________________ 41

18. Type locality of the Morgarts Beach Member _______ 42

19. Location of the type section of the Moore House

Member, Yorktown Formation ______________ 43

20. Type locality of the Moore House Member ________ 44

21. Extent of outcrops of the Moore House Member of

the Yorktown Formation _________________ 46

22. Schematic sections along major Virginia rivers ______ 49

23. View of the cliffs just below Wilmont Wharf on the

Rappahannock River ____________________ 50

24. Location of structural features in part of the Virginia

Coastal Plain ________________________ 51

25. View of the cliffs at Burhans Wharf on the

Rappahannock River ____________________ 53
CONTRIBUTIONS TO STRATIGRAPHY

STRATIGRAPHIC REVISION OF UPPER MIOCENE AND 

LOWER PLIOCENE BEDS OF THE CHESAPEAKE GROUP, 

MIDDLE ATLANTIC COASTAL PLAIN

By LAUCK W. WARD and BLAKE W. BLACKWELDER

Abstract

The Eastover Formation, a newly recognized upper Miocene marine 

unit within the Chesapeake Group, is herein named and described. The 

Eastover Formation is divided into two members: a lower, burrowed, silty, 

fine-grained sand - the Claremont Manor Member - and an upper, shelly, finegrained sand - the Cobham Bay Member. The Eastover Formation extends 

from southern Maryland to North Carolina and as far inland as Richmond. 

Although beds of the Eastover Formation have previously been assigned to the 

Yorktown Formation, the Yorktown is a distinct unit that can be divided into 

four members: the Sunken Meadow, Rushmere, Morgarts Beach, and Moore 

House. Sediments assigned to the Eastover Formation have also been assigned 

erroneously to the Calvert, Choptank, and St. Marys Formations.

INTRODUCTION

The Eastover Formation is herein named and described 

for a 5- to 28-m-thick sequence of upper Miocene sediments 

underlying the Coastal Plain of Virginia and the adjacent areas 

of North Carolina and Maryland (fig. 1). Some sediments 

previously included in the Calvert, Choptank, St. Marys, and 

Yorktown Formation (Clark and Miller, 1906, 1912; Olsson, 1917; 

Mansfield, 1928, 1931, 1943) are now included in the Eastover 

and Yorktown Formations. Although superficially resembling 

parts of the Calvert, Choptank, St. Marys, and Yorktown 

Formations, the Eastover Formation is a lithologically distinct 

assemblage of sediments occupying a unique depositional basin 

and containing a characteristic fossil assemblage. The Eastover 

Formation unconformably overlies Cretaceous, Paleocene, 

Eocene, Oligocene, and Miocene marine units as well as preMesozoic Piedmont metamorphic rocks. Contacts are sharp and

Dl
D2 CONTRIBUTIONS TO STRATIGRAPHY

.21 "'44^... 2«4,^-< 

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0 10 20 30 40 MILES

Figure 1. Selected outcrops that are listed in the "Locality Register."
CHESAPEAKE GROUP, MIDDLE ATLANTIC COASTAL PLAIN D3

well-defined. The Eastover Formation is 28 m thick in the 

Claremont area of Surry County, Va., and is approximately 5 to 

10m thick in exposures over much of its outcrop belt across the 

central Virginia Coastal Plain. The Eastover Formation is 

composed of a lower unit, the Claremont Manor Member that is 

a silty burrowed sand, and an upper unit, the Cobham Bay 

Member that is a shelly fine sand. These members of the 

Eastover Formation are of Tortonian (late Miocene) Age.

Some earlier workers (for example Clark and Miller, 

1906, 1912; Gibson, 1970, 1971) included sediments of the 

Eastover Formation in the Yorktown Formation. Therefore, the 

Yorktown is redefined and divided into four members: the 

Sunken Meadow, Rushmere, Morgarts Beach, and Moore House 

Members. A correlation chart (fig. 2) shows the stratigraphic 

succession of these units. These formations, the Eastover and 

the Yorktown, are part of the Chesapeake Group.

ACKNOWLEDGMENTS

Appreciation is expressed to J. E. Hazel, N. F. Sohl, T. M. 

Cronin, and R. M. Forester, all of the U.S. Geological Survey, 

for technical assistance and help in the field. G. B. Lawrence 

and J. B. Green, Jr., Richmond, Va., C. H. Lee, University of 

South Carolina, S.C., Thor Hansen, Washington, D.C. and C. E. 

Mason, the George Washington University, Washington, D.C., 

assisted in various phases of field and laboratory work. C. E. 

Ray, Smithsonian Institution, provided valuable advice.

DISCUSSION

Early stratigraphic studies in Virginia included sediments, 

herein assigned to the Eastover Formation, within the 

"Appomattox" or "Lafayette" Formation. McGee (1888) placed 

the "orange-colored sands and clays" at Petersburg, Va., in his 

Appomattox Formation. In 1891, McGee rejected the name 

Appomattox and, with Barton (1891), revived the name 

Lafayette Formation. Later work showed that these orange 

sands, included earlier in the Appomattox Formation and later in 

the Lafayette Formation, were of various ages and represented 

the weathered residuum of many different marine units. The 

term Lafayette Formation has since been abandoned (Wilmarth, 

1957, p. 1129).

Beds herein assigned to the Eastover Formation were 

placed in the Calvert, Choptank, St. Marys, or Yorktown 

Formations by Clark and Miller (1906, 1912). The exposure of 

the Eastover Formation below Bowlers Wharf on the 

Rappahannock River, Va. (loc. 2, fig. 1 of this report) was called 

Calvert (Clark and Miller, 1912, p. 135) and the sections listed
D4 CONTRIBUTIONS TO STRATIGRAPHY

EPOCH

PLEISTO- CENE

PLIOCENE

MIOCENE

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Formation Lowe

-15 

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VIRGINIA c

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(upper 

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Figure 2. Correlation chart showing stratigraphic relationship of the

members of the Eastover and Yorktown Formations. The lower part of the 

Yorktown Formation consists of the Sunken Meadow Member and the upper 

part consists of the Rushmere, Morgarts Beach, and Moore House 

Members. The "Little Cover Point" unit is an informal unit recognized only 

in Maryland. On this chart, the Eastover Formation is represented by the 

Claremont Manor and the Cobham Bay Members. Age shown in millions of 

years.
CHESAPEAKE GROUP, MIDDLE ATLANTIC COASTAL PLAIN D5

(1912, p. 143-145) from the Rappahannock River were assigned 

to the St. Marys Formation. Part of the section given for the 

Yorktown Formation at Yorktown, Va. (1912, p. 161), belongs to 

the Eastover Formation. This section was described in reverse 

stratigraphic order, and the oldest bed was listed first (1912, p. 

161). This first bed mentioned belongs to the Eastover 

Formation. Clark and Miller also assigned a St. Marys age to 

the exposures of shell marl along the Blackwater River, Va.; this 

shell marl is herein placed in the Yorktown Formation. 

Although Clark and Miller named the Yorktown Formation, they 

assigned Yorktown sediments at. Petersburg, Va. (1912, p. 139), 

to the Calvert Formation, apparently because they expected 

beds to the west to be progressively older than those to the east. 

Olsson (1917) recognized that some sediments in 

southeastern Virginia and northeastern North Carolina were 

older than Yorktown and younger than St. Marys. For these 

intermediate-age beds he introduced the term "Murfreesboro 

stage." Olsson listed five localities where sediments of his 

Murfreesboro cropped out. In this list, the Miocene at 

Murfreesboro, N.C., was included (1917, p. 156). Field work by 

the present authors showed that the Cobham Bay Member of the 

Eastover Formation and the Yorktown Formation (Sunken 

Meadow, Rushmere, and Morgarts Beach Members) are present 

at that locality. The Pamunkey River near West Point, Va., was 

also listed (1917, p. 156) as a Murfreesboro locality. The 

exposures there are herein assigned to the Eastover Formation 

(Claremont Manor and Cobham Bay Members). Beds of blue clay 

(along the James River) herein considered to be Yorktown 

Formation, were assigned to the Murfreesboro by Olsson (1917,

p. 157). Beds exposed at Petersburg, Va., were placed in the 

Murfreesboro (1917, p. 157), but, as mentioned above, these beds 

are referable to the Yorktown Formation. In North Carolina, 

beds that can be correlated with the Yorktown Formation were 

placed in the St. Marys Formation by Clark and Miller (1912) and 

later assigned by Olsson (1917, p. 158) to the Murfreesboro. 

Mansfield (1928) suggested that the term Murfreesboro may not 

be available as a rock stratigraphic term because of the 

Murfreesboro Limestone in Tennessee.

On the basis of the molluscan assemblage, Mansfield 

(1928, p. 2) concluded that Olsson's Murfreesboro Stage belonged 

to the lower part of the Yorktown Formation. In 1931, 

Mansfield (p. 94) recognized two faunal horizons at the type 

locality of the "Murfreesboro stage" and assigned the lower unit 

to his zone 1 of the Yorktown and the other to zone 2 of the 

Yorktown. Mansfield (1928) proposed a stratigraphic scheme for 

the Virginia Coastal Plain in which sediments, now included in 

the Eastover Formation, were placed in the St. Marys 

Formation. Mansfield (1931) provided a more detailed
D6 CONTRIBUTIONS TO STRATIGRAPHY

stratigraphic outline including a description of the lithology, 

distribution, and fossils of the St. Marys and Yorktown 

Formations. All the localities that Mansfield called Stratum A, 

Zone 1 and Zone 2 of the St. Marys belong to the Eastover 

Formation.

The Mt. Folly Formation of Weems (1968) is not 

adequately defined as a lithostratigraphic unit and includes parts 

of several different formations. The Mt. Folly is based on 

"yellow sand" at a leached marine section in which the lower 

boundary is placed at a change to less weathered material, and 

the upper part apparently includes beds belonging to the 

Yorktown Formation. Mt. Folly on the York River is only 5 km 

(8 miles) below West Point, whereas the section given by Weems 

(1968, p. 15) is stated to be "twenty miles below West Point," 

which would place it near Yorktown, Va. We propose that the 

name "Mt. Folly Formation" be rejected for the above reasons.

Johnson (1969) recognized two distinct lithologies in the 

St. Marys Formation (Eastover Formation of this report). The 

"lowermost beds of the St. Marys" were called the "silty sand" in 

Johnson's figure 5 and the "uppermost beds of the St. Marys" 

were called the "sandy shell" unit. These units correspond to the 

Claremont Manor and Cobham Bay Members of the Eastover 

Formation.

Gibson (1970) described basin migration and formational 

distribution of the Miocene and Pliocene from New Jersey to 

North Carolina. His isopach map of the St. Marys Formation 

(1970, fig. 5) showed limited St. Marys deposition south of the 

Potomac River. Later, Gibson (1971, p. 12) indicated that "no

unquestionable pockets of strata of Maryland St. Marys age are 

found in Virginia." He concluded that the St. Marys Formation 

is virtually absent south of the Potomac River. However 

Gibson's (1975, fig. 5) stratigraphic chart indicates the presence 

of the St. Marys in both Maryland and Virginia.

Teifke (1973), in an attempt to establish a rockstratigraphic framework for the Virginia Coastal Plain, included 

all beds above the Calvert Formation and below the Columbia 

Group Pleistocene within the Yorktown Formation.

A consistent stratigraphic framework is obviously lacking 

for upper Miocene and lower Pliocene beds underlying the 

Virginia Coastal Plain. Early work by Clark and Miller (1912), 

Olsson (1917), and Mansfield (1928, 1931, 1943) showed a 

confusing mixture of lithostratigraphic, chronostratigraphic, and 

biostratigraphic units and more modern work has failed to 

eliminate the confusion.

Because of the general similarity of these clastic 

deposits, the first inclination is to group the various units 

together. However, such a grouping obscures the regional 

geologic history. Study of outcrops, quarries, and drill data,
CHESAPEAKE GROUP, MIDDLE ATLANTIC COASTAL PLAIN D7

together with biostratigraphic research, has resulted in the 

recognition of several new units. Lithologic differences, 

although subtle in places, are persistent, and the lateral as well 

as vertical expressions of the formations are discernible. 

Mapping of lower and upper contacts reveals that each of the 

named units occupies a unique basin. This paper describes these 

extensive, mostly fossiliferous, marine units deposited during 

late Miocene and early Pliocene time. On the margins of these 

basins, gravel beds were deposited which, in some places, may 

be related to particular marine sequences. Over most of the 

study region, marine units overlie marine units and no beds of 

intervening fluvial gravel are present.

CHRONOLOGY OF DEPOSITIONAL EVENTS

After a brief marine transgression during the late 

Oligocene (unnamed unit), the Maryland and Virginia Coastal 

Plain became emergent until the middle part of the early 

Miocene. At this time, a series of marine transgressions began 

in Maryland and Virginia that were to leave a relatively 

complete stratigraphic record through the early Pliocene. 

Lower and middle Miocene lagoonal and shallow shelf deposits 

(Calvert and Choptank Formations) stretch from the Eastern 

Shore of Maryland south to Richmond, Va. In the middle 

Miocene, a series of small embayments occupied the 

southeastern corner of Maryland while the Virginia Coastal Plain 

was largely emergent. From late middle to early late Miocene 

time, deposition shifted southward to the Rappahannock River 

area in Virginia. The transgress;ion resulted in accumulation of 

fine shelly sand of the St. Marys Formation in northeastern 

Virginia and southeastern Maryland. During the late Miocene, 

marine sedimentation was virtually terminated in Maryland, 

except in small areas where the Claremont Manor and Cobham 

Bay seas overlapped that section. Sedimentation continued in 

Virginia throughout the late Miocene, and the Claremont Manor 

sea covered the northern two-thirds of the Coastal Plain. The 

later Coham Bay sea overlapped slightly into Maryland and 

North Carolina.

In early Pliocene time the Yorktown sea covered eastern 

Virginia, and large numbers of warm temperate mollusks 

flourished. During maximum transgression, the Yorktown sea 

transgressed older post-Paleozoic sediments onto the 

Piedmont. Regressive sediments of the late Yorktown sea 

occupy only a small area in southeastern Virginia.

The Eastover and Yorktown Formations are considered to 

belong to the Chesapeake Group. The name "Chesapeake 

Formation" was originally proposed for strata of Miocene age by 

Darton (1891). DaU (1892) changed Darton's term to
D8 CONTRIBUTIONS TO STRATIGRAPHY

"Chesapeake Group" and included all the rocks of Miocene age 

from the Chesapeake Bay area to Florida. Rocks in Florida and 

Georgia subsequently were omitted from the Chesapeake Group.

The Yorktown Formation of Virginia and North Carolina 

was also placed in the Chesapeake Group by these early workers 

and was considered to be of Miocene age. The Yorktown 

Formation is closely related to the same series of events and 

geographical controls influencing the deposition of the other 

formations. It is herein retained in the Chesapeake Group. 

However, various evidence leads to the conclusion that the 

Yorktown is entirely of early Pliocene age. (J. E. Hazel, written 

commun. 1977).

The Eastover Formation is related to similar depositional 

conditions and basins, such as those in the Yorktown and earlier 

St. Marys deposits, and it is also considered part of the 

Chesapeake Group.

Also included in the Chesapeake Group are the deposits 

of the Chowan River Formation (upper Pliocene). The Chowan 

River is found in southeasternmost Virginia and in North 

Carolina. Basin configuration suggests that this was the last of 

the large inland basins that had been present almost 

continuously since early Miocene time. Chowan River molluscan 

assemblages represent the last occurrence of many elements 

common in earlier Chesapeake Group assemblages and indicate 

that the Chowan River was one of the last of the warm 

temperate seas to inundate major parts of the eastern Atlantic

Coastal Plain. Deposits of the Chowan River are, in part, 

lithically very similar to other units in the Chesapeake Group.

MIOCENE SERIES

EASTOVER FORMATION 

Definition And Description

The Eastover Formation is named for a series of beds of 

silty sand, clay, and shelly fine sand in the Maryland, Virginia, 

and North Carolina Coastal Plain. This formation is weU 

exposed at the type locality along the right bank of the James 

River near Eastover, Surry County, Va., loc. 1 (fig. 3 and 4). It 

is divided into two members. The lower member, the Claremont 

Manor, consists of greenish-gray (5Y5/2) (Goddard, 1948), finegrained clayey sand or sandy clay. The sand-sized fraction is 

typically glauconitic (usually 5 percent or less) and poorly 

sorted; fine-grained mica is rare. The overlying Cobham Bay 

Member consists of units of fine-grained, well-sorted, shelly 

sand. The Eastover Formation differs from the underlying St.
CHESAPEAKE GROUP, MIDDLE ATLANTIC COASTAL PLAIN D9

500 1000 METERS 

_I

0 1000 2000 3000 FEET

CONTOUR INTERVAL 10 FEET

NATIONAL GEODETIC VERTICAL DATUM OF 1929

DEPTH CURVES IN FEET-BATUM IS MEAN LOWER LOW WATER

SHORELINE SHOWN REPRESENTS THE APPROXIMATE LINE OF MEAN HIGH WATER

Figure 3. Location of type section of the Eastover Formation, Claremont and 

Surry quads., Va.

Marys in that the sand fraction in the parts lower of the 

Eastover are generally less well sorted and lower parts of the 

Eastover are diatomaceous. In addition, deposits of the St. 

Marys Formation, particularly in Virginia, contain abundant 

mollusks that thrived in the well-sorted, fine silty sand.

Locality 1. Type section of the Eastover Formation, 5.1 km east 

of Eastover; measured 0.8 km above Mount Pleasant, right bank 

of the James River, (Surry County, Va.). (Surry 7 1/2-min. quad.- 

1965)

Thickness Grn7~ 

Pleistocene(?)

Orange sand and gravel ..................... 5.0
DIG CONTRIBUTIONS TO STRATIGRAPHY

Figure 4. Type locality of Eastover Formation showing silty Claremont 

Manor Member overlain by shelly Cobham Bay Member.

Pleistocene(?)--Cont inued 

Yorktown Formation 

Rush mere Member

Tan shelly fine sand . . 2.0
CHESAPEAKE GROUP, MIDDLE ATLANTIC COASTAL PLAIND11

Sunken Meadow Member

Tan, moderately sorted, phosphatic,

glauconitic, shelly sand; bedding

obscured by large volume of bivalves

(mostly Chesapecten).

Lower contact ........................ 2.0

Eastover Formation

Cobham Bay Member

Tan fine shelly sand. Bivalves

abundant and dominated by

Chesapecten and Isognomon. Massive shell

bed showing some bedding; lower contact

undulating and, in areas, cutting across

shell bands of the Claremont Manor ......... 2.0

Claremont Manor Member

Greenish-gray, poorly sorted, fine silty

sand that is weathered to light tan in

the upper half. Mollusks fairly abundant

but concentrated in thin shell ............. 5.0

 Approximate mean low-tide level 

The Eastover differs from the overlying Yorktown by the 

presence of pearlaceous bivalves (Isognomon) in the silty, shelly 

sand of the upper part of the Eastover. They also differ in the 

presence of the better sorted shelly fine sand in much of the 

Yorktown. Where the Yorktown overlies the lower member of 

the Eastover, lithologic differences are very pronounced because 

the lower member is very clayey, not as well-sorted, and tends 

to lack the abundant shells of the Yorktown. Lithologies vary 

over the large area that these basins occupy, but at most 

localities, lithologic differences between formations are very 

apparent. Contacts between units are very sharp and many are 

marked by phosphate, bone, and burrowing of the older units. 

Regionally, some contacts indicate angular unconformities.

The dip of the Eastover varies locally according to 

underlying structural conditions. Along the Rappahannock 

River, in the vicinity of Bowlers Wharf (loc. 2) and Laytons 

Landing (loc. 3), Essex County, Va., the Eastover dips to the 

northwest (upriver) at a rate of 2 m/km. From Bayport (loc. 4) 

to Urbanna (loc. 5), Middlesex County, Va., the Eastover 

resumes the normal seaward dip at a rate of about 0.6 m/km. 

These structural anomalies, that locally affect the dip, also 

affect the formation's thickness. In the vicinity of Bottoms 

Bridge, New Kent County, Va. (loc. 6), the Eastover Formation 

is only 6 m thick, whereas to the southeast at Claremont (loc. 7) 

it is 24 m thick, and to the west at Richmond, Va., (loc. 8) it is 

14 m thick. The Eastover Formation is considered to be late 

Miocene in age and correlates with the Tortonian Stage in 

Europe.
D12 CONTRIBUTIONS TO STRATIGRAPHY

Stratigraphic Relationships

In the outcrop area, the Eastover Formation overlies 

progressively older sediments from north to south. In the 

Potomac River area it overlies the Choptank Formation (loc. 24) 

and St. Marys Formation (loc. 10). South of this, along the 

Mattaponi River (loc. 11) and Pamunkey River, Va., (loc. 12) it 

overlies the Calvert Formation. Farther south, the Eastover 

overlies upper Oligocene sands which crop out along the 

Chickahominy River (loc. 6). Near Hope well, Va. (loc. 13, 20), 

the Eastover Formation overlies beds of the Nanjemoy 

Formation (lower and middle Eocene). At Colonial Heights, Va. 

(loc. 14), the Eastover overlies Cretaceous sandstone. Near 

Murfreesboro, N.C. (loc. 15), the Eastover overlies Cretaceous 

clayey sand. These relationships are discussed in the description 

of the two members. In the western half of the Eastover basin, 

sediments are considerably more clayey, and in some areas, near 

Richmond (loc. 8) and Petersburg (loc. 16), diatomaceous clays 

were deposited. In the eastern and central parts of the Eastover 

basin, both members become increasingly sandy, which makes 

their lithologic separation difficult, even though the contact 

between them is sharp.

Evidence for subsurface flexures may be found in the 

irregular depositional patterns within the Eastover basin. 

During the Claremont Manor transgression, a thick (24 m) 

sequence of silty sands and clays was deposited in the Claremont 

area (loc. 7). After the Claremont Manor regression, the area 

was locally uplifted so that the Cobham Bay sea apparently 

deposited only a thin bed in this area, while at the same time 

thicker beds were deposited to the east, west, and north. The 

Claremont area was still positive during the Yorktown 

transgression and in some areas the Cobham Bay Member was 

removed by erosion so that the Yorktown lies directly on the 

Claremont Manor (loc. 17).

Claremont Manor Member

Definition and Description. The Claremont Manor 

Member is named for the extensive exposures along the James 

River below Upper Chippokes Creek near Claremont Manor. The 

type locality is 1.3 km below the mouth of Sunken Meadow 

Creek, Surry County, Va. (loc. 42) (fig. 5, 6). The Claremont 

Manor consists of beds of poorly sorted, coarse to fine, silty and 

clayey sand that fine upward in many areas to clay. These clay 

sequences generally mark the perimeter of the Claremont Manor 

basin; toward the center or eastern parts of the basin the sand 

content increases. Where fresh, most of these beds are
CHESAPEAKE GROUP, MIDDLE ATLANTIC COASTAL PLAIN Dl 3

500 1000 METERS

0 1000 2000

\ 

3000 FEET

CONTOUR INTERVAL 10 FEET

NATIONAL GEODETIC VERTICAL DATUM OF 1929

DEPTH CURVES IN FEET DATUM IS MEAN LOWER LOW WATER

SHORELINE SHOWN REPRESENTS THE APPROXIMATE LINE OF MEAN HIGH WATER

Figure 5. Location of the type section of the Claremont Manor Member of 

the Eastover Formation and the Sunken Meadow Member of the Yorktown 

Formation. (Claremont 7.5-min quad.).

greenish-gray (5 YR 5/2) (Goddard, 1948), but weather to an ironstained tan (10 YR 8/6). The Claremont Manor transgression 

covered much of the Virginia Coastal Plain and overlapped 

slightly into southeastern Maryland. The thickest known 

sequence of Claremont Manor is at Claremont (loc. 7) where 24 

m occur in the subsurface and in outcrop. The strike is 

approximately north-south, and the dip varies according to local 

structural peculiarities but averages approximately 0.5 mAm. 

The Claremont Manor is an open-marine deposit containing a 

variety of mollusk species that are generally confined to thin 

beds within the member. The poorly sorted, coarse, basal sand 

of the Claremont Manor differs from the underlying finegrained, well-sorted shelly sand of the St. Marys Formation.
D14 CONTRIBUTIONS TO STRATIGRAPHY

Figure 6. Type locality of the Claremont Manor Member, Eastover Formation, 

and of the Sunken Meadow Member, Yorktown Formation.

Where it overlies the Choptank, the same differences are 

evident. The Claremont Manor differs sharply from the 

diatomaceous silty clay of the Calvert and from the glauconitic 

sands of the upper Oligocene (unnamed), the lower and middle 

Eocene (Nanjemoy), and Paleocene (Aquia). The Cobham Bay
CHESAPEAKE GROUP, MIDDLE ATLANTIC COASTAL PLAIN Dl 5

Member, which overlies the Claremont Manor, differs from the 

latter in being well-sorted, less silty or clayey, and in having an 

abundance of well-preserved mollusks in thick beds.

Locality 42. Measured section at the type locality of the 

Claremont Manor Member of the Eastover Formation and type 

locality of the Sunken Meadow Member of the Yorktown 

Formation. 1.3 km below mouth of Sunken Meadow Creek, right 

bank of the James River, Surry Co., Va., Claremont 7 1/2 min 

quad.

Thickness

Pleistocene(?)

Red and orange sand and gravel ............... 4.5

Yorktown Formation (in part):

Rushmere Member:

Tan fine sandy oyster and barnacle

shell hash .......................... 1.5

Tan fine shelly sand; Chesapecten madisonius 

common ........................... 1.0

Sunken Meadow Member:

Tan shelly sand ranging from poorly sorted 

to sorted in different layers; phosphatic, 

glauconitic; sand dollar spines, ostracodes, 

and foraminifers abundant, Chesapecten 

jeffersonius abundant .................. 2.5

Eastover Formation:

Cobham Bay Member:

Isognomon abundant, sand dollar spine common, 

sand-size phosphate present ............. 0.5

Claremont Manor Member

Weathered tan clayey fine sand, sparsely

fossiliferous, shells decayed and

soft .............................. 1.5

Clayey sand, sparsely fossiliferous; sand

fraction somewhat poorly sorted .......... 3.0

Green-gray sandy clay containing scattered shell

(decayed) and concretions (sand fraction

poorly sorted to sorted in different beds);

sand dollar spines abundant in certain

layers ............................. 4.5

 mean low-tide level 

Stratigraphic relationships. The Claremont Manor 

overlaps unconformably a wide range of lithologic units of 

varying ages. In the Petersburg (loc. 19) and Hopewell (loc. 20) 

areas, the Claremont Manor overlies the Nanjemoy (lower and
D16 CONTRIBUTIONS TO STRATIGRAPHY

middle Eocene). At the end of Chesterfield Avenue in Colonial 

Heights (loc. 14), it rests on coarse, cross-bedded Cretaceous 

sand. At Richmond, the Claremont Manor is exposed behind the 

city jail (loc. 8), where it overlies the diatomaceous clay of the 

Calvert Formation. To the east of Richmond, at Bottom's 

Bridge (loc. 6), in an area that apparently has been 

intermittently postive throughout the Tertiary, the Claremont 

Manor overlies unnamed beds of late Oligocene 

(Chickasawhayan) age. To the north of Bottom's Bridge, at 

Elsing Green (loc. 12) on the Pamunkey River, the Claremont 

Manor may again be seen to overlie the Calvert Formation. 

Similar exposures of the contact with the Calvert Formation 

may be seen at Gravatts Mill east of Hanover Court House, in 

King William County (loc. 21) and at Rickahock on the left bank 

of the Mattaponi River below Walkerton, King and Queen 

County (loc. 11). A short distance downstream from Rickahock, 

the Claremont Manor overlies a thin remnant of the St. Marys 

Formation at Mantua Landing (loc. 23) and at White Oak Landing 

(loc. 22), both in King William County. In the Tappahannock 

area, Essex County (loc. 67), the Claremont Manor directly 

overlies the St. Marys, but farther upstream at Fones Cliffs (loc. 

9) it rests on the Choptank Formation. This same relationship 

may be seen in the series of bluffs along the Potomac River 

from Westmoreland State Park to Currioman Bay, Westmoreland 

County (loc. 24). At Mt. Airy Mill Pond in Richmond County 

(loc. 68), the fining-upward sequence of the St. Marys is overlain 

unconformably by the poorly sorted basal sand of the Claremont 

Manor.

The lower contact of the Claremont Manor is sharp in 

most places, and phosphate nodules, bone, teeth, and pebbles are 

present at the boundary. The member generally consists of a 

basal conglomerate and poorly sorted clayey sand and grades 

upward to a clay or silty fine sand. This fining-upward trend 

enables easy recognition of the basal transgressive sand. In 

Petersburg (loc. 16), Richmond (loc. 8), Henrico County (loc. 6) 

and many other localities, the shelly sands of the Cobham Bay 

Member overlie, in sharp contrast, the clay or silty clay of the 

Claremont Manor. The Cobham Bay apparently overlaps the 

entire extent of the Claremont Manor so that in only one area, 

Claremont (loc. 17) does the Yorktown rest directly on the 

Claremont Manor. This relationship was probably caused by 

local uplift and transgressive beveling.

Paleogeography.- The Claremont Manor basin covered 

most of the Virginia Coastal Plain and overlapped slightly into 

Maryland (fig. 7). The basin was open to the sea in the east but 

was bounded by an emerged part of southeastern Maryland to 

the north, and by the Virginia Piedmont to the west. It is
CHESAPEAKE GROUP, MIDDLE ATLANTIC COASTAL PLAIN D17

38°,

^T

'4 Cj_ .-7 -7 _ "ASHINGJ5N WASHINGTON i«*ijr.TirRF >nST:ySRELLT'a ? h-fe^-^'f ^ -^

0 10 20 30 40 50 60 KILOMETERS

I I I I I I

I I I I 

0 10 20 30 40 MILES

Figure 7. Basin configuration of the Claremont Manor Member, Eastover 

Formation. Extent of outcrops of the Claremont Manor Member 

(westernmost line) and locations where the lower contact (center line) 

and upper contact (easternmost line) reach sea level.
D18 CONTRIBUTIONS TO STRATIGRAPHY

bordered on the south by a technically active, high area in 

North Carolina that had been emergent since the deposition of 

the Pungo River Formation (upper lower to lower middle 

Miocene).

South of the James River, the Claremont Manor is 

present in the subsurface in the vicinity of Dendron, Va., but 

outcrops are lacking and it has not been found as far south as 

the Nottoway River. A thick sequence (9 m) is present at 

Petersburg (loc. 16, 19), but just below Baileys Creek on the 

right bank of the James River (loc. 13) it is entirely absent on 

the apex of the "Hopewell High" area. Only a short distance to 

the east of this "High," in the Tar Bay area (loc. 20), the 

Claremont Manor is again well represented. The member is 

present at Richmond (loc. 8) and extends northward into 

Carolina County (loc. 26). At least 9 m of Claremont Manor is 

present at Stratford Hall (loc. 24) on the Potomac, and the unit 

may be present overlying the St. Marys in St. Marys County, Md. 

(loc. 10). On the Eastern Shore of Maryland, Claremont Manor 

guide fossils were found in a well at Crisfield (loc. 27) at the 40- 

to 46-m interval.

Age and Correlation. The Claremont Manor is probably 

of early Tortonian Age, early late Miocene (Berggren and Van 

Couvering, 1974). The lower part of the overlying Cobham Bay 

member has been dated radiometrically (K/Ar) from glauconite 

at 8.7 + 0.4 million years. Beds on the St. Marys River in 

Maryland that have been traditionally assigned to the middle of 

the underlying St. Marys Formation have yielded glauconite 

dated at 12.0 + 0.5 million years (Krueger Enterprises Inc., 

Geochron Laboratories). Although various authors have 

indicated dissatisfaction with glauconite as a basis for 

radiometric dating and the dates may be too young, a Tortonian 

Age seems probable at present.

Paleo environ m ent. The Claremont Manor sea is 

believed to have been open marine, but the molluscan species 

diversity is substantially lower than that of the preceding St. 

Marys Formation or of the later Cobham Bay Member. This 

condition may be a function of both lower temperature and 

chemical conditions in the embaymnent. The large percentage 

of silt and clay characteristic of the Claremont Manor may also 

have been an inhibiting factor to molluscan proliferation. Near 

the center of the embayment and in its easternmost exposures, 

diversity increases as does the sand content. The increase in 

sand content toward the basin center reflects the facts that the 

dip is low and that parts of the eastern and central basin were 

relatively postive and were apparently influenced by currents. 

Also, the easternmost beds are younger, and water conditions 

apparently changed to higher current energy. As a whole, the 

Claremont Manor's fossil assemblages are poorly preserved and
CHESAPEAKE GROUP, MIDDLE ATLANTIC COASTAL PLAIN Dl 9

at many localities consist only of molds and casts. The best 

preserved fossils are found along the James River in Surry 

County from Claremont to Cobham Wharf and consist mainly of 

mollusks. In the Petersburg and Richmond area, large 

accumulations of diatoms are present in the clay, indicating that 

the area was a protected part of the embayment.

Molluscan Assemblage The following mollusks are commonly

found in the Claremont Manor Member:

Scapharca carolinensis (Dall. 1897)

Scapharca clisea (Pall, 1898)

Scapharca sp.

Scapharca virginiae (Dall, 1897)

Glycymeris virginiae (Dall,1897)

Isognomon sp.

Chesapecten middlesexensis (Mansfield, 1836)

Ostrea sp.

Lucinoma contracta (Say, 1824)

Crassatella surryensis (Mansfield, 1928)

Cardium laqueatum ssp.

Euloxa latisulcata (Conrad, 1839)

Glossus~fraterna TSay, 1824)

Dosinia acetabulum (Conrad, 1832)

Lirophora dalli (Olsson, 1914)

Mercenaria sp. nov.

Pleiorytis sp. nov.

Panopea goldfussii (Wager, 1839)

Turritella sp. aff. T. plebeia Say, 1824

Ecphora sp.

Cobham Bay Member

Definition and Description. The Cobham Bay Member is 

named for exposures along the James River at Cobham Bay (fig. 

8, 9). The type section is 0.8 km below Cobham Wharf, Surry 

County, Va. (loc. 28). At Cobham Bay, the member reaches a 

thickness of 3.7 m and crops out from below Claremont Wharf to 

Lower Chippokes Creek. The Cobham Bay Member consists of a 

fine-grained well-sorted shelly sand throughout most of its 

geographic extent. Only locally, where structural or 

depositional features created barriers, have clays accumulated. 

One such location is found along the Rappahannock River from 

Bayport (loc. 4), Middlesex County, to Bowlers Wharf (loc. 2), 

Essex County. Sandy laminae increase in thickness to the east 

and clay laminae correspondingly thin in that direction. Near 

the apex of the structure at Bayport, only a trace of clay 

laminae remains in the fine sand. However, these features are 

local and the Cobham Bay retains its clean, sandy,
D20 CONTRIBUTIONS TO STRATIGRAPHY

500 1000 METERS

0 1000 2000 3000 FEET 

CONTOUR INTERVAL 10 FEET

NATIONAL GEODETIC VERTICAL DATUM OF 1929

DEPTH CURVES IN FEET DATUM IS MEAN LOWER LOW WATER

SHORELINE SHOWN REPRESENTS THE APPROXIMATE LINE OF MEAN HIGH WATER

Figure 8. Location of the type section of the Cobham Bay Member, 

Eastover Formation.

characteristics over most of the basin. This member contains 

large numbers of fossil mollusks, which are indicative of an 

open-marine, subtropical shallow embayment. Grayish blue (5 

PB 5/2) where fresh, the Cobham Bay sediments weather to a 

yellowish orange (10 YR 8/6). The Cobham Bay varies in 

thickness from 1.0 m in the area of Murfreesboro, N.C. (loc. 29), 

to 3.6 m at Wilcox Lake in Petersburg (loc. 16), 3.6 m at 

Richmond (loc. 8), 12 m at Bayport on the Rappahannock River 

(loc. 4), and 3 m in St. Marys County, Md. (loc. 10). In the type 

area (loc. 28), the Cobham Bay is 3.7 m thick. The strike is 

approximately north-south, but the dip varies with local 

structural features.

In the previously mentioned Bowlers Wharf-Bayport area 

along the Rappahannock River, the Cobham Bay dips to the 

northwest (upriver) at a rate of 2.0 m/km. To the east of 

Bayport, which is the apex of the structure, the Cobham Bay 

resumes the normal seaward dip, but at only 0.3-0.6 m/km.
CHESAPEAKE GROUP, MIDDLE ATLANTIC COASTAL PLAIN D21

Figure 9. Type locality of the Cobham Bay Member, Eastover Formation.

Throughout most of the basin, the normal seaward dip is 

maintained at a rate of approximately 1.0 m/km. The locus of 

deposition seems to have been in the York River area. Most of
D22 CONTRIBUTIONS TO STRATIGRAPHY

the Cobham Bay overlies the Claremont Manor, and its wellsorted, less clayey sand, and its sandy shell beds differ from the 

units of the Claremont Manor. Sediments of Cobham Bay 

lithology containing Cobham Bay guide fossils have been found 

by the authors in the vicinity of New Bern, N.C., near the mouth 

of the Trent River. These deposits appear to be erosional 

remnants but indicate an extensive basinal area in North 

Carolina. The Cobham Bay basin is bounded to the north by the 

uplifted coastal plain of southeastern Maryland that it slightly 

overlapped, to the west by the Virginia Piedmont, and to the 

south by a structural high in the Neuse River area.

Locality 28. Type section of the Cobham Bay Member of the

Eastover Formation. 0.8 km below Cobham Wharf, right bank of

the James River, Surry 7 1/2 min quad.

Thickness 

(m)

Obscured by vegetation .......................... 2.5

Yorktown Formation (in part): 

Rushmere Member:

Tan fine shelly sand, clayey, phosphatic, 

partially indurated, partially leached; fine 

broken shell present: Chesapecten madisonius 

and Chama sp. common ................. 1.5

Sunken Meadow Member:

Tan fine shelly sand, phosphatic; Glycymeris

abundant, Ostrea, Turritella, sand dollar

spines .............................. 0.8

Tan fine shelly sand, glauconitic, phosphatic; 

Placopecten clintonius and Chesapecten 

jeffersonius abundant, sand dollar spines common; 

cetacean bone commonly found along base of 

unit ............................... 1.2

Eastover Formation

Cobham Bay Member:

Tan fine shelly sand, glauconitic, phosphatic 

slightly silty (sand fraction sorted); 

Argopecten and Chesapecten middlesexensis 

abundant ............................ 1.1

Tan fine slightly silty, sorted sand;

fewer shells than in above unit ............ 0.5

Yellow-tan medium-fine clean shelly sand, quartz

somewhat poorly sorted; some phosphatic grains

of organic origin; larger quartz grains

rounded; many Chesapecten

and Crassatella ....................... 0.8

Tan fine sand containing abundant broken fine
CHESAPEAKE GROUP, MIDDLE ATLANTIC COASTAL PLAIN D23

shell; many bivalves are articulated; Glycymeris, 

Mercenaria, Anadara, Chione, and Crassatella 

abundant ............................ 0.6

Tan fine shelly, slightly clayey, medium-fine 

sand, sorted, glauconite, phosphatic; containing 

very abundant broken fine shell ........... 0.3

Tan fairly well-sorted fine quartz sand; containing 

large shells (some bivalves articulated), 

Chesapecten, Isognomon ................ 0.4

 undulating contact 

Claremont Manor Member:

Blue-gray sandy clay; fraction is fine, 

moderately sorted to poorly sorted in different

horizons; sand dollar spines common; scattered

poorly preserved shell; top of unit burrowed

from above .......................... 1.8

 approximate mean low-tide level 

Stratigraphic relationships. At Murfreesboro, N.C. (loc. 

15), and along the Nottoway River near Littleton, Sussex 

County, Va. (loc. 30), the Cobham Bay Member overlies the 

light-gray sand and clay of the Cretaceous. However, over most 

of its geographic range, the Cobham Bay unconformably overlies 

the Claremont Manor Member. At Petersburg (loc. 16) and at 

Richmond (loc. 8), the fine, well-sorted, shelly sands of the 

Cobham Bay overlie diatomaceous- clays of the Claremont 

Manor. In the Claremont area, below the mouth of Sunken 

Meadow Creek (loc. 7), a thin tongue of the Cobham Bay 

overlies the poorly sorted silty sand of the Claremont Manor. 

Above the mouth of Sunken Meadow Creek (loc. 17), the Cobham 

Bay Member has been entirely removed by transgressive 

beveling of the younger Yorktown sea. Downriver from Sunken 

Meadow Creek, the Coham Bay thickens to its maximum 

thickness of 4.6 m in the Cobham Wharf area. The contact 

between the Claremont Manor and the Cobham Bay along this 

stretch undulates and in some areas has a relief of 0.6 to 0.9 

m. Shell bands in the underlying Claremont Manor were 

excavated in places (loc. 1) by scouring of the transgressing 

Cobham Bay sea. The Cobham Bay dips below sea level along 

the James River at Grove Wharf, James City County (loc. 31), 

where it is overlain by the Sunken Meadow Member of the 

Yorktown Formation. Just below Hopewell, Prince George 

County (loc. 13), a thin (0.3 m) bed of Cobham Bay directly 

overlies the lower and middle Eocene Nanjemoy Formation; the 

Claremont Manor was completely removed by erosion. To the 

east and west of this area, the Cobham Bay overlies clayey beds 

of the Claremont Manor. At Bottom's Bridge, Henrico County
D24 CONTRIBUTIONS TO STRATIGRAPHY

(loc. 6), a structurally high area, a thin (0.3 m) bed of Cobham 

Bay overlies the silty clay of the Claremont Manor. This same 

stratigraphic relationship is also present to the north, exposed in 

deep ravines near Tunstall, New Kent County (loc. 32). Along 

the Pamunkey River, the Cobham Bay is first exposed where it 

descends to river level just west of Romancoke on the left bank 

of the Mattaponi at Court House Landing, King and Queen 

County (loc. 36), the Cobham Bay consists of 2.4 m of fine, wellsorted, slightly clayey, shelly sand. This contrasts with the 

poorly sorted very clayey medium to fine sand of the Claremont 

Manor found upstream at White Oak Landing (loc. 22). Along 

the Rappahannock River, the Cobham Bay is exposed from Fones 

Cliffs (loc. 9) in Richmond County discontinuously to Whiting 

Creek, Middlesex County (loc. 37). At Fones Cliffs, it is seen 

overlying the Claremont Manor, but its lower contact is 

obscured. In the Rte. 621 road cut just south of Connellee Mill 

Pond (loc. 69), the glauconitic basal sand of the Cobham Bay 

overlies the burrowed clay of the Claremont Manor at an 

elevation of 23 m. The Cobham Bay lower contact is at 13 m 

ASL (above sea level) at Bayport, Middlesex County (loc. 4), but 

is only 0.9 m ASL or less 10 km away at Bowlers Wharf, Essex 

County (loc. 2). This dip is probably structurally controlled and 

is too great to reflect a primary depositional dip. Around 

Urbanna (loc. 5), the Cobham Bay is extensively exposed as it 

also is at Burhans Wharf (loc. 38) and Whiting Creek (loc. 37) in 

Middlesex County. The outcrop at Burhans Wharf exhibits a 

sharp westward dip and may represent the sloping flanks of a 

local bar. Horizontal strata just upstream at Urbanna (loc. 5) 

and just downstream at the mouth of Whiting Creek (loc. 37) 

indicate that the westward dipping of beds is a local feature and 

probably not related to local structural activity, but rather due 

to depositional conditions. In contrast to the normally fine sand 

of the Cobham Bay Member, the exposure of that member on 

the right bank of the Piankatank at Freeport (loc. 39) and Blands 

Wharf (loc. 40) contain coarse sand and pebbles. This is 

interpreted to indicate an influx of coarse deltaic detritus. 

Similar deposits were made on Maryland's eastern shore during 

the late regressive stages of the Cobham Bay sea. Auger holes 

on Virginia's eastern shore (J. Owens, C. Denny, R. Mixon, 

unpub. data, 1977) in the Cobham Bay sequence penetrated 

coarse sand and pebbles. Along the Potomac, the Cobham Bay 

may be seen in a few places along Westmoreland Bluffs (loc. 24), 

and along Hull Creek in Northumberland County (loc. 41). In St. 

Marys County, Md. (loc. 10), the Cobham Bay overlies the 

Claremont Manor Member.

The Yorktown Formation overlies most of the Cobham 

Bay Member. At Murfreesboro, N.C. (loc. 29), the Sunken
CHESAPEAKE GROUP, MIDDLE ATLANTIC COASTAL PLAIN D25

Meadow Member of the Yorktown overlies the Cobham Bay, as 

it does along the Nottoway near Littleton (loc. 30). A similar 

stratigraphic arrangement exists along the James River, Va., 

from Grove Wharf, James City County (loc. 31), to Sunken 

Meadows Creek in Surry County (loc. 42). At Baileys Creek near 

Hopewell (loc. 13) and along Lieutenant Run at Petersburg (loc. 

43), the Rushmere Member of the Yorktown Formation directly 

overlies the Cobham Bay. In the Richmond area, the Yorktown 

is not present, and the Cobham Bay is capped by a weathered 

residuum and coarse sand and gravel. Farther to the east, at 

Bottom's Bridge (loc. 6), the Sunken Meadow Member overlies 

the Cobham Bay as it does throughout most of King William 

County. At Fleets Mill in King William County (loc. 44), a very 

thin (15 cm) bed of the Sunken Meadow Member overlies the 

Cobham bay. Undifferentiated Yorktown may be seen to overlie 

a back-barrier sequence of laminated clays of the regressive 

Cobham Bay in a road cut along State Rte. 360 at Piscataway 

Creek, Essex County (loc. 45). The Cobham Bay-Sunken Meadow 

contact may be interpreted to be at sea level just below the 

mouth of Felgates Creek on the York River, York County (loc. 

46), on the basis of an unpublished manuscript (1890) by G. D. 

Harris, but the cliff line has been largely obscured by riprap and 

covered by vegetation.

Paleogeography. The Cobham Bay sea covered most of 

the Virginia Coastal Plain and overlapped slightly into 

southeastern Maryland (fig. 10). To the west, the Cobham Bay 

slightly overlapped the Piedmont in the northern part of the 

State, but south of Petersburg the shoreline trended southeast. 

Only very thin beds of the Cobham Bay are known as far south 

as the Nottoway and Meherrin Rivers. The northeastern part of 

the North Carolina Coastal Plain was apparently positive at this 

time, but remnants of Cobham Bay-age sediments in the Neuse 

River-New Bern area (loc. 47 and 48) indicate that a small 

embayment existed here at this time. A deep open-pit 

phosphate mine at Aurora, Beaufort County, N.C. (loc. 49), 

exposes no Eastover Formation sediments, and the Yorktown 

Formation rests directly on the Pungo River Formation (lower 

and middle Miocene).

Age and Correlation. The Cobham Bay Member is of 

late Tortonian Age (middle late Miocene). As previously 

mentioned, a radiometric date on glauconite from the lower part 

of the Cobham Bay Member is 8.7 + 0.4 million years, and beds 

judged to belong to this member from the shallow subsurface of 

the eastern shore of Virginia have been dated, by means of 

glauconite, at 6.46 + 0.15 million years (J. P. Owens, 1977, 

written commun.). Chesapecten middlesexensis, one of the 

characteristic species of the Cobham Bay Member, occurs in the
D26 CONTRIBUTIONS TO STRATIGRAPHY

0 10 20 30 40 50 60 KILOMETERS

I I I I I I

^ I I I

10 20 30 40 MILES

Figure 10. Basin configuration of the Cobham Bay Member, Eastover 

Formation. Extent of outcrops of the Cobham Bay Member 

(westernmost line) and locations where the lower contact 

(center line) and upper contact(easternmost line) reach sea level.
CHESAPEAKE GROUP, MIDDLE ATLANTIC COASTAL PLAIN D27

Area zone of the Miocene of Florida. Akers (1972) placed beds 

of the Area zone in planktonic foraminifer zone N17, which is 

largely of late Tortonian Age (Berggren and van Couvering, 

1974). The ostracode Aurila redbayensis (Howe and Brown, 

1935) is present in the upper part of the Cobham Bay in the 

shallow subsurface of the eastern shore of Virginia and in the 

Area zone (J. E. Hazel, written commun., 1975). These data 

support the age interpreted from glauconite radiometry.

Paleoenvironment. The Cobham Bay sediments were 

deposited in a fairly shallow open-marine embayment. The 

abundant and varied molluscan assemblage indicates favorable 

substrates, abundant food supply, and warm-temperate to 

subtropical conditions. Two main molluscan biofacies are 

present throughout the basin. One consists of large numbers of 

the small bivalve, Spisula rappahannockensis Gardner. This 

species thrived in northern and northwestern sections of the 

basin and apparently preferred quiet, slightly more silty 

substrates, although they are present in low numbers throughout 

the basin. The other biofacies were dominated by large species 

of Chesapecten, Mercenaria, and Isognomon. These taxa 

apparently preferred higher energy conditions and clean sandy 

substrates. The exposure below Bowlers Wharf (loc. 2) typifies 

the Spisula biofacies, and the exposure at Cobham Wharf (loc. 

28) typifies the Chesapecten-Mercenaria-Isognomon biofacies.

Molluscan Assemblage. The following mollusks are commonly

found in the Cobham Bay Member:

Scapharca carolinensis (Pall, 1897)

Scapharca arata (Say~1824)

Striarca centenaria (Say, 1824)

Glycymeris sp.

Isognomon sp.

Euvola smithi (Olsson, 1914)

Chesapecten middlesexensis (Mansfield, 1936)

Carolinapecten urbannaensis (Mansfield, 1928)

Placopecten princepoides (Emmons, 1858)

Pododesmus philippi Gardner, 1943

Ostrea sp.

Ostrea compressirostra Say, 1824

Stewartia anodonta (Say, 1824)

Pseudochama corticosa (Conrad, 1833)

Astarte rappahannockensis Gardner, 1943

Astarte sp.

Crassatella urbannaensis (Mansfield, 1928)

Cardium laqueatum (Conrad, 1831)

Spisula delumbis (Conrad, 1832)

Spisula bowlerensis (Gardner,1943)

Spisula rappahannockensis (Gardner, 1943)
D28 CONTRIBUTIONS TO STRATIGRAPHY

Euloxa latisulcata (Conrad. 1839)

Glossus~fraterna TSay, 1824)

Macrocallista sp.

Dosinia acetabulum (Conrad, 1832)

Lirophora sp.

Mercenaria sp.

Pleiorytis sp.

Panopea goldfussii Wagner, 1839

Kuphus fistula (H. C. Lea, 1843)

Turritella plebeia Say, 1824

Tripsycha virginica (Conrad, 1838)

Pterorhytis umbrifer (Conrad, 1832)

Ecphora sp.

Bulliopis quadrata (Conrad, 1830)

Busycotypus sp.

Busycotypus coronatum (Conrad, 1840)

Oliva idonea Conrad

Conus sp.

PLIOCENE SERIES

YORKTOWN FORMATION 

Previous Work

The first comprehensive treatment of the strata on the 

York River in the vicinity of Yorktown, Va., was done by Harris 

(1890, unpub. manuscript). Dall and Harris (1892) described 

some of the beds in this area but made no attempt to name 

them. In 1906, Clark and Miller described these beds and beds 

on the James River as the Yorktown Formation but gave no type 

section. In 1912, Clark and Miller greatly expanded this 

description and gave many sections. No type section was 

established, but a composite section, originally made by Harris, 

was given. Although Clark and Miller described the Yorktown 

Formation, they had difficulty recognizing the unit in areas 

remote from the York River-James River sections. Beds now 

known to belong to the Yorktown at Petersburg, Va. (loc. 43), 

were considered to be Calvert, and the same beds along the 

Nottoway River (loc. 50) were placed in the St. Marys 

Formation. Mansfield (1927, unpub. thesis) established a 

stratigraphic scheme for the beds in question and, in 1928, 

published an abbreviated form of his correlation chart. 

Mansfield excluded the "Perna beds" from the Yorktown and 

considered the Pecten clintonius beds as the lowermost unit of 

the Yorktown. Thus, the beds were distinguished primarily on 

paleontologic grounds. Mansfield (1931, 1943) expanded his
CHESAPEAKE GROUP, MIDDLE ATLANTIC COASTAL PLAIN D2 9

description of the Miocene units but gave no type section for the 

Yorktown and divided the formation only into faunal zones. His 

work lacked lithostratigraphic treatment of the beds, and no 

type section for the Yorktown. John (1969) recognized the 

presence of several lithofacies within the Yorktown, but 

followed Mansfield's zonation closely.

Gibson (1971, p. 12) placed beds in the Yorktown 

Formation that had been considered to be St. Marys by Johnson 

and by other workers. These beds are properly assigned to the 

Eastover Formation. Teifke (1973) assigned all the beds above 

the Calvert Formation to the Yorktown and included beds placed 

in the Choptank and St. Marys, as well as those herein assigned 

to the Eastover Formation.

Redefinition and Description

The Yorktown Formation consists of a basal, pebbly, 

coarse-grained sand unit, a shelly fine-grained sand unit, a very 

fine grained sandy clay unit, and an upper sandy shell hash. 

These various units are herein described as four members. In 

ascending order from the base, they are the Sunken Meadow 

Member, the Rushmere Member, the Morgarts Beach Member, 

and the Moore House Member. A lectostratotype for the 

Yorktown Formation is herein designated. The original 

description of the Yorktown Formation (Clark and Miller, 1906) 

did not clearly designate a type locality but included beds at 

Yorktown, Va., and on the James River. The beds at Yorktown 

are now largely inaccessible because the cliffs have been 

obscured by riprap. A section near Rushmere, Isle of Wight 

County (loc. 61), is here designated as lectostratotype (fig. 14, 

15).

Stratigraphic Relationships

The Yorktown Formation overlies the Cobham Bay 

Member of the Eastover Formation throughout most of the 

Virginia coastal plain (fig. 11). In northeastern North Carolina, 

the Yorktown overlies Upper Cretaceous deposits. Near 

Skippers, Greensville County, Va. (loc. 51), and at Halifax, 

Halifax County, N.C. (loc. 52), the Yorktown overlaps 

crystalline rocks of the Piedmont. In the structurally high area 

near Claremont, Va. (loc. 17), erosion by the Yorktown sea 

removed sediments of the Cobham Bay Member so completely 

that the Yorktown directly overlies the Claremont Manor 

Member. In the western third of the Yorktown basin, the lower 

contact of the formation is marked by a basal lag deposit of 

coarse-grained sand, pebbles, cobbles, phosphate nodules, bone,
D30 CONTRIBUTIONS TO STRATIGRAPHY

 ym

Figure 11. Yorktown Formation overlying laminated clays of the Eastover 

Formation at locality 45 near Tappahannock, Va. Pebbles are visible 

along the contact.

and fish teeth. Toward the center part of the basin and 

principally in the area where the Yorktown directly overlies the 

Cobham Bay, the lower contact relationships are more subtle. 

In areas where both formations consist mostly of macromollusks in a matrix of sand, a study of the bedding features and 

lithology is required to separate the two units. These areas are 

chiefly in the vicinity of the James and York Rivers where the 

contact between the two formations is irregular and marked by 

small pebbles and bone. Over most of its extent in Virginia, the 

Yorktown is overlain by units of fluvial and marine-regressive 

coarse-grained sand and gravel. In part of northeastern North 

Carolina, the Yorktown is overlain by the clayey, shelly sands of 

the Croatan Formation. This sequence exists in the vicinity of 

Colerain Landing (loc. 53) and Edenhouse Landing (loc. 54) in 

Bertie County, N.C. and at the Texasgulf Pit, Beaufort County, 

N.C. (loc. 49).

The Yorktown Formation strikes approximately 

northeast-southwest and has a varying dip. In some areas, the 

Yorktown dips to the west. Reverse dipping of this type may be 

seen just below Morgarts Beach, Isle of Wight County, Va. (loc. 

55), and just below Yorktown, York County, Va. (loc. 56). As in 

the Cobham Bay Member, subsurface irregularities probably 

caused a sharp westward dip. From the apex of the structure,
CHESAPEAKE GROUP, MIDDLE ATLANTIC COASTAL PLAIN D31

the beds resume their normal eastward dip at a much lower 

angle. These relationships suggest intermittent graben-type 

deep-seated basement faulting during the late Miocene and early 

Pliocene, causing contemporaneous depositional anomalies. The 

average dip of the Yorktown is 0.5 m/km. The thickness of the 

Yorktown varies from only a few cm in the far westward 

exposures to approximately 12 m or more in quarries in eastern 

areas. In the vicinity of Yorktown, the thickness is 

approximately 16.8 m.

Paleogeography

The initial transgressive phase (the Sunken Meadow 

Member) of the Yorktown sea covered much of the Virginia 

coastal plain and parts of the northeastern North Carolina 

coastal plain, but not until after a basinal realignment during 

the ensuing maximum transgression did the seas cover almost 

the entire North Carolina coastal plain. The Yorktown basin is 

bounded to the north by the emerged Maryland coastal plain and 

to the west by the Piedmont, which is slightly overlapped. To 

the south, the Yorktown is bounded by a linear high area 

approximating the course of the Neuse River. The early Pliocene 

sea overlapped this barrier, but only thin beds were deposited. 

South of the Neuse River high, deposits of this age have been 

placed in the Yorktown and Raysor Formations.

Age and Correlation

On the basis of planktonic fossils and radiometric data, J. 

E. Hazel (written commun., 1975, 1977) placed the Yorktown 

Formation entirely within the early Pliocene. Akers (1972) 

described zone N19 Zanclian-Age planktonic foraminifers from 

the Yorktown at Hampton, Va. Glauconite from the Rushmere 

Member near Grove Creek, James River, James City County, 

has been dated at 4.4 + 0.2 million years (Krueger Enterprises, 

Inc., Geochron Laboratories).

J. E. Hazel (written commun., 1978) stated that the basal 

beds of the Yorktown (the Sunken Meadow Member) are 

equivalent to planktonic foraminifer zone N18 in age and 

constitute the lower zone of the Pliocene (Berggren and van 

Couvering, 1974). Zone N18 began about 5.0 million years ago. 

If the 6.46 million-year date on the upper part of the Cobham 

Bay Member is correct, then the unconformity between the 

Cobham Bay and the Yorktown approximately represents the 

time equivalent of the Messinian Stage of the Mediterranean 

region.
D32 CONTRIBUTIONS TO STRATIGRAPHY

Paleoenvironment

During the initial transgressive phase of the Yorktown 

sea, a large open embayment existed in which large numbers of 

warm-temperate mollusks thrived. During the maximum 

transgression, the Yorktown sea reached, and even overlapped, 

the Piedmont, depositing the Rushmere Member clay beds with a 

high diversity (more than 250 species) of mollusks. These 

mollusks are typical of open-marine subtropical conditions. In 

the calmer waters after maximum transgression, clayey fine 

sand and silt containing the abundant small bivalve, Mulinia 

congesta (Conrad) were deposited. These beds are termed the 

Morgarts Beach Member. This member formed behind partially 

protective offshore bars at Chuckatuck (loc. 58), Yorktown (loc. 

57), and Glebe Neck (loc. 59). Although Mulinia is somewhat 

euryhaline, the presence of open-marine species in the Morgarts 

Beach Member as far west as the Piedmont indicates normal 

saline conditions. Regressive sediments are seen in southeastern 

Virginia where the terminal Yorktown sea occupied only a final 

small area in Virginia. At the time of this regression, either the 

basin in northeastern North Carolina was emergent or later 

erosion and transgressive beveling removed the sedimentological 

record.

Sunken Meadow Member

Definition and Description. The Sunken Meadow 

Member is herein named for beds in the cliffs just below Sunken 

Meadow Creek, on the right bank of the James River, Surry 

County, Va. (loc. 42) (see fig. 5).

The Sunken Meadow Member consists of a basal 

transgressive, coarse-to-medium, poorly sorted, very shelly 

sand. To the west, the lower contact of the member is marked 

by a coarse lag deposit. To the east the basal deposits are finer 

and are dominated by glauconitic and phosphatic fine shelly 

sand.

Stratigraphic relationships. The Sunken Meadow 

unconformably overlies the Cobham Bay in much of Virginia, and 

to the south it overlies older stratigraphic units. Throughout its 

extent, the lower contact of the member is sharp. The Sunken 

Meadow Member is overlapped in its entire extent by the 

maximum transgressive phase (the Rushmere Member) of the 

Yorktown Formation. The Rushmere overlies the Sunken 

Meadow apparently conformably, although there is evidence of a 

brief diastem between the two members. Areas north of the 

Rappahannock River in Lancaster County, Va., which had been 

shallow marine during the deposition of the Sunken Meadow
CHESAPEAKE GROUP, MIDDLE ATLANTIC COASTAL PLAIN D33

Figure 12. Piankatank River, Va., near Martiau showing shelly beds of the 

Sunken Meadow Member overlain by current-bedded fine comminuted 

shell hash containing Ophiomorpha.

Member, became emergent during Rushmere time, and shoaling 

areas were present as far south as the Piankatank River (fig. 

12).

At Martiau (loc. 82) and Glebe Neck (loc. 59), the Sunken 

Meadow Member consists of very shelly glauconitic sand and 

abundant large coral, indicative of a shallow open-marine 

environment. It is overlain by current-bedded coquinoid deposits 

containing Ophiomorpha, indicative of shoaling during Rushmere 

time. In North Carolina, the Sunken Meadow Member overlies 

the Cobham Bay Member of the Eastover Formation at 

Murfreesboro, Hertford County (loc. 29), and the Pungo River 

Formation at Aurora, Beaufort County (loc. 49). The Sunken 

Meadow strikes northeast-southwest and dips at the average 

rate of 0.5 m/km but locally this dip may vary. The Sunken 

Meadow averages about 3 m in thickness, but thins to the west 

and pinches out near St. Stephens Church, King and Queen 

County, Va. (loc. 44), Manquin, King William County, Va. (loc. 

60), Bottoms Bridge, New Kent County, Va. (loc. 6), below the 

mouth of Baileys Creek, Prince George County, Va. (loc. 13), 

and Homeville, Sussex County, Va. (loc. 30).

Paleogeography. The Sunken Meadow Member occupied 

much of the eastern two-thirds of the Virginia coastal plain
D34 CONTRIBUTIONS TO STRATIGRAPHY

75°

0 10 20 30 40 50 60 KILOMETERS

III I I III

I ' I II 1

0 10 20 30 40 MILES

Figure 13. Extent of outcrops of the Sunken Meadow Member of the 

Yorktown Formation (westernmost line) and locations where the 

lower contact (center line) and upper contact (easternmost line) 

reach sea level.
CHESAPEAKE GROUP, MIDDLE ATLANTIC COASTAL PLAIN D35

extending as far west as King and Queen, King William, New 

Kent, Charles City, Prince George, Sussex and Southampton 

Counties in Virginia (fig. 13). In North Carolina, the Member is 

found in Hertford, Bertie, and Beaufort Counties.

Paleoen vironm ent. Molluscan assemblages from the 

Sunken Meadow Member indicate that normally saline, shallowshelf conditions existed in the basin and that the sandy substrate 

was a favorable habitat in the mild temperate sea. Many 

mollusk species attained an unusually large size at this time. 

Diversity among the mollusks was moderately high, although 

somewhat less than the Cobham Bay assemblages and the later 

Yorktown assemblages. A structurally high area from Cape 

Lookout, N.C., to the Cape Fear Arch area, North and South 

Carolina, served as a barrier, which probably deflected warmer 

currents from the south. Later in the Yorktown, these barriers 

were breached and the accompanying moilU3can assemblages had 

distinctly more tropical affinities.

Molluscan Assemblages. The following mollusks are commonly

found in the Sunken Meadow Member of the Yorktown

Formation:

Glycymeris subovata (Say, 1824)

Euvola smithi (Olsson, 1914)

Chesapecten jefferspnius (Say, 1824)

Pecten watsonensis (Mansfield, 1936)

Pycnodonte sp.

Ostrea compressirostra Say, 1824

Stewartia anodonta Say, 1824

Lucinoma contracta (Say, 1824)

Astarte deltoidea (Gardner, 1943)

Astarte vaginulata (Pall, 1903)

Astarte coheni Conrad, 1840

Crassatella cyclopterus (Pall, 1903)

Cardium taeniopleura (Pall, 1900)

Spisula confraga (Conrad, 1833)

Glossus fraterna (Say, 1824)

Posinia acetabulum (Conrad, 1832)

Mercenaria sp.

Mercenaria inflata (Pall, 1903)

Panopea reflexa (Say, 1824)

Kuphus fistula (H. C. Lea, 1843)

Turritella pilsbryi Gardner, 1928

Ecphora quadricostata (Say, 1824)

Oliva canaliculata (H. C. Lea, 1843)

Scaphella solitaria (Conrad, 1830)

Conus marylandicus Green, 1831

Busycon maximum (Conrad, 1839)

Lirosoma multicostata (Olsson, 1914)
D36 CONTRIBUTIONS TO STRATIGRAPHY

500 1000 METERS

0 1000 2000 3000 FEET

CONTOUR INTERVAL 10 FEET

NATIONAL GEODETIC VERTICAL DATUM OF 1929

DEPTH CURVES IN FEET DATUM IS MEAN LOWER LOW WATER

SHORELINE SHOWN REPRESENTS THE APPROXIMATE LINE OF MEAN HIGH WATER

DASHED LINE REPRESENTS HALF-CONTOUR INTERVAL

Figure 14. Location of Yorktown Formation lectostratotype near Rushmere, 

Isle of Wight County, Va. (loc. 61). Type locality of the Rushmere Member.

Rushmere Member

Definition and Description. The Rushmere Member is 

herein named for beds exposed along the right bank of the James 

River at Burwell Bay near Rushmere, Isle of Wight County, Va. 

(loc. 61) (fig. 14, 15).

The Rushmere Member consists of a fine well-sorted 

shelly sand. Phosphatic sand and glauconite are common in 

amounts less than 10 percent. Some coarse sand and pebbles are 

present near its lower contact in areas where it overlaps the 

Sunken Meadow Member and rests directly on older beds 

(Eastover Formation or Piedmont Rocks).
CHESAPEAKE GROUP, MIDDLE ATLANTIC COASTAL PLAIN D37

Figure 15. Lectostratotype of the Yorktown Formation and type locality of 

the Rushmere Member. Shelly sand of the Rushmere Member (A) is 

overlain by clay of the Morgarts Beach Member (B).

Locality 61. Measured lectostratotype section of the Yorktown 

Formation and type locality of the Rushmere Member of the 

Yorktown Formation. 0.7 km east of Rushmere, right bank of 

the James River, Isle of Wight County, Va. Bacons Castle 7 1/2 

min quad.

Thickness

Post-Yorktown:

Partially covered, probably Pleistocene ........... 3.0

Yorktown Formation (in part):

Moore House Member:

Reddish-brown, partially leached, indurated, 

coarse, broken-shell hash; Chama, Chesapecten 

common ............................ 3.7

Morgarts Beach Member:

Blue-gray fine slightly sandy clay. Glauconite 

and phosphate present. Sand-size fraction 

is fine grained and highly calcareous 

because of large number of sand dollar 

spines and foraminifers. Unit appears 

"blocky" on face of outcrop because of
D38 CONTRIBUTIONS TO STRATIGRAPHY

Yorktown Formation (in part)--Continued 

Morgarts Beach Member--Continued

desiccation. Abundant mollusks include

Turritella and Mulinia .................. 5.5

Rushmere Member:

Blue-gray fine sandy clay containing abundant

shell. Sand fraction is glauconitic,

phosphatic, containing abundant sand dollar

spines and foraminifera. This unit contains

some medium-sand-size rounded

quartz ............................. 1.1

 approximate mean low-tide level 

Stratigraphic relationships. The Rushmere Member 

overlapped the Sunken Meadow Member in its entire extent 

except in the area north of the Rappahannock River in 

Lancaster County, Va. As a result, the Rushmere rests on the 

Cobham Bay near St. Stephens Church, King and Queen County, 

Va. (loc. 44), at Manquin, King William County, Va. (loc. 60), 

near the mouth of Baileys Creek, Prince George County, Va. 

(loc. 13), and along Lieutenant Run, Petersburg, Va. (loc. 43). 

Near Skippers, Greensville County, Va. (loc. 51), the Rushmere 

rests directly on (granite) saprolite. At Halifax, Halifax County, 

N.C. (loc. 52), the same stratigraphic relationship exists, but 

near Palmyra, in Martin County, N.C. (loc. 62), the Rushmere 

rests on Upper Cretaceous sands. In the area around Fort 

Barnwell, on the Neuse River, Craven County, N.C. (loc. 63), the 

Rushmere-age beds overlie the bryozoan limestone of the Castle 

Hayne Formation. The Pliocene beds at these exposures (loc. 

63) are of the same lithology and age as the Rushmere. Beds 

also assigned to the Yorktown are present in the Martin 

Marietta Quarry, in New Bern, Craven County, N.C. (loc. 64). 

Here the Yorktown overlies Oligocene limestone, but where 

solution and erosion has removed the Oligocene, Yorktown beds 

directly overlie the upper calcareous sandstone of the Castle 

Hayne. Where the Rushmere directly overlies the Sunken 

Meadow Member, the two are apparently conformable. A 

distinct contact, however, separates them in most areas. The 

Rushmere is overlain throughout most of its areal extent by the 

clayey beds of the Morgarts Beach Member. The two beds are 

conformable, and, though in some areas they grade into each 

other, they are usually separable. Areas where the Morgarts 

Beach Member overlies the Rushmere are discussed in the 

Morgarts Beach section. The Rushmere strikes approximately 

northeast-southwest in Virginia and approximately north-south 

in North Carolina. It dips at 0.5 m/km and is as much as 4.8 m 

thick in outcrop.

Paleogeography. The Rushmere Member represents the 

maximum transgressive phase of the Yorktown Formation and
CHESAPEAKE GROUP, MIDDLE ATLANTIC COASTAL PLAIN D39

38°,

75°

77°

0 10 20 30 40 50 60 KILOMETERS

I I I I I I

0 10 20 30 40 MILES

Figure 16. Extent of outcrops of the Rushmere and Morgarts Beach Members 

of the Yorktown Formation (westernmost line) and locations where the 

lower contact of the Rushmere (center line) and upper contact of the 

Morgarts Beach (easternmost line) reach sea level.
D40 CONTRIBUTIONS TO STRATIGRAPHY

occupies the lower three-fourths of the Virginia coastal plain 

(fig. 16). In North Carolina, the Rushmere basin covered that 

part of the Coastal Plain north and northeast of the Neuse 

River. The western boundary of the basin was slightly west of 

the Fall Line. To the north, the emerged Maryland and northern 

Virginia coastal plains provided a boundary. To the south, the 

partial barrier in the Neuse River area created a separate, 

though interconnected, basin that contained identical sediments 

but a more tropical molluscan assemblage.

Paleoenvironment. The Rushmere sea was clearly an 

open-marine, shallow-shelf environment that was conducive both 

to increased diversity and to large populations. The molluscan 

assemblages show a subtropical to tropical influence, especially 

in the eastern parts of the Yorktown basin. In the more 

shoreward areas, diversity decreases and many of the exotic 

tropical taxa are not present. South of the Neuse River barrier, 

the assemblage is predominantly tropical but retains many of 

the taxa of the northern Yorktown populations. Shallow, 

shoaling, offshore bar systems were present in the eastern areas 

in Nansemond, York, and Middlesex counties, Va. In the Aurora 

area, Beaufort County, N.C. (loc. 49), which was a moderately 

deep part of the basin, only the Rushmere Member is present but 

the Morgarts Beach Member occurs to the west in more shallow, 

quieter areas.

Molluscan assemblages. Because of the similarity of the 

assemblages of the Rushmere, Morgarts Beach, and Moore House 

Members, mollusks of those units are considered together (See 

"Moore House section").

Morgarts Beach Member

Definition and Description. The Morgarts Beach Member 

is herein named for beds exposed at Morgarts Beach, right bank 

of the James River, Isle of Wight County, Va. (fig. 17, 18).

The Morgarts Beach Member is commonly a very fine 

sandy to silty clay that contains a few silty, very fine sand 

beds. The member contains an abundant molluscan assemblage, 

but less abundant than that in the sandy Rushmere Member. The 

emergence of the offshore bars created a quiet lagoonal area to 

the west in which the fine sands, silts, and clays were 

deposited. Tilted bedding reflects the presence of these bars 

and, in the channels between them, the sand content is greater 

owing to higher energy conditions.

Locality 55. Measured type section of the Morgarts Beach 

Member. 1.0 km below Morgarts Beach, right bank of the James 

River, Isle of Wight County, Va. (Mulberry Island 7 1/2 min 

quad.).
CHESAPEAKE GROUP, MIDDLE ATLANTIC COASTAL PLAIN D41

xMogarts Beach

0 ' 500 1000 METERS

0 1000 2000 3000 FEET

CONTOUR INTERVAL 5 FEET

NATIONAL GEODETIC VERTICAL DATUM OF 1929

DEPTH CURVES IN FEET DATUM IS MEAN LOWER LOW WATER

SHORELINE SHOWN REPRESENTS THE APPROXIMATE LINE OF MEAN HIGH WATER

Figure 17. Location of the type section of the Morgarts Beach Member, 

Yorktown Formation.

Thickness

Pleistocene(?):

Tan sand and cobbles ........................ 1.2

Yorktown Formation (in part):

Morgarts Beach Member:

Gray fine slightly sandy clay (tan where weathered) 

containing abundant small shell (Mulinia) 

throughout .......................... 3.0

Rushmere Member:

Blue-gray sandy shell clay, abundant

large shell ........................... 2.1

 approximate mean low tide 

Stratigraphic relationships. The Morgarts Beach 

overlies the Rushmere Member and coincides in geographic 

extent with that unit (fig. 16). This relationship is conformable,
D42 CONTRIBUTIONS TO STRATIGRAPHY

Figure 18. Type locality of the Morgarts Beach Member and closeup of this 

member at locality 61 (Rushmere).

and in a few places the contact is gradational. The Morgarts 

Beach may be seen overlying the Rushmere near St. Stephens, 

King and Queen County, Va. (loc. 44), along the right bank of the 

James River near Rushmere, Isle of Wight County, Va. (loc. 61), 

at Grove Wharf, left bank of the James River, James City 

County, Va. (loc. 31), below the mouth of Baileys Creek on the 

right bank of the James River, Prince George County, Va. (loc. 

13), along Lieutenant Run in Petersburg, Va. (loc. 43), and at 

Sycamore Bend, Nottoway River, Southampton County, Va. (loc. 

50). The two members may also be seen in the vicinity of 

Murfreesboro, right bank of the Meherrin River, Hertford 

County, N.C. (loc. 29). In all of these locations, the underlying 

Rushmere Member is more arenaceous and contains abundant 

mollusks. The Morgarts Beach is distinguished by its fine, 

clayey lithology and abundance of small bivalves (Mulinia 

congesta). The Morgarts Beach conforms to the same strike and 

dip as the underlying Rushmere and attains an outcrop thickness 

of 6 m.

Paleogeography. The Morgarts Beach occupies the same 

area as the Rushmere in Virginia and northeast North Carolina 

(fig. 16). South of this area, it loses its identity and probably 

grades into the lithology of the Rushmere Member.
CHESAPEAKE GROUP, MIDDLE ATLANTIC COASTAL PLAIN D43

;-. U S COAST GUAR 

'3S£SERVE TRAINING CENTER

1000 2000 3000 FEET 

CONTOUR INTERVAL 5 FEET

NATIDNAL GEODETIC VERTICAL DATUM OF 1929

DEPTH CURVES IN FEET DATUM IS MEAN LOWER LOW WATER

SHORELINE SHOWN REPRESENTS THE APPROXIMATE LINE OF MEAN HIGH WATER

Figure 19. Location of type section Moore House Member, Yorktown

Formation.

Paleoenvironm ent. Although the clayey beds of the 

Morgarts Beach were deposited behind protective barrier bars, 

there is no evidence of lowered salinities. Normal marine 

conditions apparently prevailed while fine clayey sediments 

formed a suitable substrate for the bivalve, Mulinia congesta. In 

many areas, this species dominated the molluscan assemblage 

and is found in very high densities. Other forms commonly 

found with Mulinia include Yoldia sp., Nuculana sp., Spisula 

delumbis and Turritella alticostata.

Moore House Member

Definition and Description. The Moore House Member is 

herein named for exposures on the York River at Moore House, 

Yorktown Battlefield Park, York County, Va. (loc. 56) (fig. 19, 

20).
D44 CONTRIBUTIONS TO STRATIGRAPHY

Figure 20. Type locality of the Moore House Member showing the very shelly 

sands of the Moore House Member overlying the siltier Morgarts Beach 

Member.

The Moore House Member, representing the regressive 

phase of the Yorktown Formation, reflects a renewal of higher
CHESAPEAKE GROUP, MIDDLE ATLANTIC COASTAL PLAIN D45

current and wave energy conditions. The member consists of 

sandy shell beds and cross-bedded shell hash and locally is 

cemented to form a very indurated rock.

Locality 56. Measured type section of the Moore House Member 

of the Yorktown Formation. Bluffs at the Moore House, right 

bank of the York River, in the Colonial National Historical Park, 

York County, Va. (Poquoson West 7 1/2-min quad).

Thickness (mT~

Yorktown Formation (in part): 

Moore House Member:

Orange fragmental shell hash, extremely 

calcareous but containing some fine quartz 

sand; bryozoan and molluscan fragments 

abundant ............................ 1.0

Tan clayey highly calcareous sand containing

abundant mollusks (Crepidula, oysters,

pectens), foraminifers, and ostracodes.

Sand is phosphatic, glauconitic, fine

grained, but somewhat poorly sorted

in places ............................ 3.0

Slump:

Lower outcrop surface obscured by

slump and by 2.1 m of riprap ............. 3.7

 approximate mean low-tide-level 

Stratigraphic relationships. The Moore House Member 

conformably overlies the Morgarts Beach Member in its outcrop 

area. The lower contacts of the Moore House, in some areas, 

are gradational with the underlying Morgarts Beach Member, but 

in most areas the transition is abrupt. The Moore House 

Member may be seen to overlie the Morgarts Beach Member 

from Morgarts Beach (loc. 55) to the vicinity of Rushmere on 

the right bank of the James River, Isle of Wight County, Va. 

(loc. 61), at Grove Wharf, left bank of the James River, James 

City County, Va. (loc. 31), and below Yorktown from Cornwallis 

Cave (loc. 65) to the Moore House, right bank of the York River, 

York County, Va. (loc. 56). At the abandoned Lone Star Cement 

Quarry near Chuckatuck, Nansemond County, Va. (loc. 58), small 

remnants of the Moore House overlie the cross-bedded shell beds 

of the Chuckatuck bar system. The Moore House strikes 

northeast-southwest and dips at approximately 5m/km, except 

locally where underlying structures affect the regional dip. The 

maximum thickness of this member in outcrop is 6 m.

Paleogeography. The Moore House Member is found 

only east of the Surry Scarp, a feature which may have been cut 

at this time (fig. 21). The member is not known from North
D46 CONTRIBUTIONS TO STRATIGRAPHY

 m^r^^su^

0 10 20 30 40 50 60 KILOMETERS

I I I I I I

I I I I 

0 10 20 30 40 MILES

Figure 21. Map showing extent of outcrops in Moore House Member of the

Yorktown Formation.
CHESAPEAKE GROUP, MIDDLE ATLANTIC COASTAL PLAIN D47

Carolina and is confined to the southeastern part of the Virginia 

coastal plain.

Paleoenvironment. The Moore House Member reflects a 

progressively shallowing, regressive sea. Molluscan assemblages 

indicate normal salinities, but some of the highest beds in the 

Williamsburg area (loc. 66) contain a few brackish-water 

mollusks. Locally large offshore bars were the site of rapid, 

large-scale, cross-bedded sand deposition.

Molluscan Assemblages. The following mollusks are commonly

found in the Rushmere, Morgarts Beach, and Moore House

Members of the Yorktown Formation:

Scapharca staminea (Say, 1832) 

Anadara scalaris (Conrad,1843) 

Anadara lienosa (Say, 1832) 

Granoarca propatula (Conrad, 1843) 

Anadara improcera (Conrad, 1845) 

Noetia incile (Say, 1824) 

Striarca centenaria (Say, 1824) 

Glycymeris tuomeyi (Pall, 1898) 

Glycymeris americana (DeFrance, 1826) 

Glycymeris arata (Conrad, 1841) 

Pecten ocklockoneensis (Mansfield, 1932) 

Placopecten sp.

Amusium mortoni (Ravenel, 1844) 

Chesapecten madisonius (Say, 1824) 

Chesapecten septenarius (Say, 1824) 

Pecten decenmarius Conrad, 1834 

Pecten rogersii (Conrad, 1834) 

Pecten eboreus Conrad, 1833 

Argopecten vicenarius (Conrad, 1843) 

Plicatula marginata Say, 1824 

Qstrea sculpturata Conrad, 1840 

Qstrea raveneliana Tuomey <5c Holmes, 1855 

Stewartia anodonta (Say, 1824) 

Lucinoma contracta (Say, 1824) 

Chama congregata Conrad, 1833 

Pseudochama corticosa (Conrad, 1833) 

Carditamera arata (Conrad, 1832) 

Astarte undulata Say, 1824 

Astarte concentrica Conrad, 1834 

Astarte symmetrica Conrad, 1834 

Crassatella undulata Say, 1824 

Cardium acutilaqueatum Conrad, 1839 

Planicardium virginianum (Conrad, 1839) 

Spisula delumbis (Conrad, 1832) 

Spisula "harrisi (Olsson, 1914)
D48 CONTRIBUTIONS TO STRATIGRAPHY

Spisula duplinensis (Pall, 1898) 

Spisula modicella'TConrad, 1833) 

Mulinia congesta (Conrad, 1833) 

Rangia clathrodonta (Conrad. 1833) 

Glossus'fraterna (Say, 1824) 

Macrocallista albaria (Sav. 1834) 

Dosinia acetabulum (Conrad, 1832) 

Lirophora sp.

Chione cortinaria (Rogers & Rogers, 1835) 

Mercenaria tridacnoides (Lamarck, 1818) 

Pleiorytis centenaria (Conrad, 1833) 

Panopea goldfussii Wagner, 1839 

Panopea reflexa Say. 1824

Kuphus fistula (H. C. Lea, 1843)

Diadora redimicula (Say, 1824)

Turritella alticostata Conrad, 1834

Petaloconchus sculpturatus (H. C. Lea, 1843)

Lirosoma sp.

Pterorytis umbrifer (Conrad, 1832)

Ecphora quadricostata (Say, 1824)

Urosalpinx suffolkensis Gardner (1948)

Urosalpinx trossulus (Conrad, 1832)

Peristernia filicatum (Conrad, 1843)

Ptychosalpinx fossulatum (Conrad, 1843)

Ptychosalpinx laqueatum (Conrad, 1832)

Ptychosalpinx altile (Conrad, 1832)

Busycon maximum (Conrad, 1839)

Busycotypus incile (Conrad, 1833)

Scaphella solitaria ssp.

Scaphella sp.

Fusinus exilis (Conrad, 1832)

Faciolaria rhomboidea Rogers <5c Rogers, 1835

Oliva canaliculata H. C. Lea, 1845

Conus marylandicus Green, 1830

Conus adversarius Conrad, 1840

Cymatosyrinx lunatum (H. C. Lea, 1843)

SUMMARY OF DEPOSITIONAL AND STRUCTURAL HISTORY

Schematic sections were prepared showing the trends of 

various units outcropping along parts of major rivers. Figure 22 

shows sections of the Chesapeake Group as seen along the 

Potomac River, the Rappahannock River, the Pamunkey River, 

and the James River. All sections have been drawn to the same 

scale so that dips and thicknesses may be compared. The 

locality numbers are shown in figure 1. Distances between each 

of the localities were measured essentially at right angles to the
POTOMAC RIVER SECTION

SEA 

LEVEL 84

SEA 

LEVEL

SEA 

LEVEL

24 85 10

RAPPAHANNOCK RIVER SECTION

Clay -facies

41

70 9 67 ' 2 3 4 71

PAMUNKEY RIVER SECTION

5 38 37

727374757677 78' 79 33

JAMES RIVER SECTION

SCALE

r 6 METERS

r 3 L 0 

0 5 10 KILOMETERS ! " ' i '0 5 MILES

SEA 

LEVEL 43 19

EXPLANATION

YORKTOWN FORMATION 

Moore House Membel Morgarts Beach Member 

Rushmere Member Sunken Meadow Member 

EASTOVER FORMATION 

EST'Cobham Bay Member

laremont Manor Member

ST. MARYS FORMATION 

H3CHOPTANK FORMATION 

EDCALVERT FORMATION

7 Locality number referred 

to in text

Nanjemoy /t

Covered

13 20 18 28 1081 31 61 55

Figure 22. Schematic sections along major Virginia rivers.

O

aM

M 

> 

* 

M

O

Oa tMtr1 

>asHI-H

OO O

>CO

13

r

t-H

25 

OCD
D50 CONTRIBUTIONS TO STRATIGRAPHY

Figure 23. View of the cliffs just below Wilmont Wharf (loc. 70) on the 

Rappahannock River showing steeply dipping beds upriver and nearly 

horizontal beds downstream.

strike. The river sections tend to parallel the direction of the 

dip. These illustrate positions of reverse dip, geologic highs, and 

regions of low-angle dipping beds. These profiles and the inland 

outcrops, shown in figure 1, enabled delimitation of certain 

coastal plain structural features. The most striking structural 

feature is found at the boundary of King George and 

Westmorland counties along the Rappahannock River, Va. (fig. 

23), where a fault is exposed. The fault is a half graben striking 

N 70° W. Beds on the southwest side of the fault dip steeply to 

the southeast at an angle of 9°. Beds on the northeastern side 

of the fault dip downriver at a very low angle. At this section, 

Eocene and lower and middle Miocene (Calvert Formation) beds 

are faulted. The fault is herein named the Wilmont Fault from 

the name of the old wharf at this locality.

Other structural movement is suggested for locations 

where beds were deposited with a westward dip. Presumably,
CHESAPEAKE GROUP, MIDDLE ATLANTIC COASTAL PLAIN D51

.* 

Wilmonf Fault ;

, "^ .

%'-4^ ';. \ 

Bottoms Bridge

^ HppewellA

X

*»-- /t

Uoc. 4

%

*: Loc: 38

. O

£" / 

£ /

^ /

^/ fl) / * * '-,

EXPLANATION)

A Structurally positive

area

-i- Monocline Arrows, 57- 

point down dip |

'' /toe, 58 : ^ : _i_ Fault Bar and ball

/.^._ "''"i- 1 on downthrown

/ Chuckatsuck Bar side

/ **"""-'" * ffi Regions of low dip

_-fcJ -Ji£^i O Locations of shoali .-r "s ing deposits

, ~' . ^ **Regions of wesr- 

, \% V*ir* t (. ward dip

, < ;

"S*k. "* ' -" -& ' L -1 **' /

Vv " ^ **t' . rft --^* /

0 10 20 30 40 50 60 KILOMETERS

I I I

I 

0 10 20 30 40 MILES

Figure 24. Location of structural features in part of the Virginia Coastal

Plain.

westward dip is caused by uplift to the east that created high 

areas. Those highs controlled sedimentary patterns within the 

particular formations. Three major areas have westwarddipping beds: the Bowlers Wharf area of the Rappahannock 

River, the lower York peninsula, and the lower James River
D52 CONTRIBUTIONS TO STRATIGRAPHY

area. In the York and James River area (fig. 24), Yorktown beds 

dip to the west (upriver). Locations of shoaling within the 

Yorktown Formation on the Piankatank River (fig. 12) and in the 

northeastern part of Nansemond County (loc. 58) are in line with 

the eastern limit of reverse dip areas, suggesting a structural 

feature that trends approximately N 15° E. This feature is 

termed the York-James River monocline because it is a steplike 

feature. This trend is virtually essentially parallel to the 

present surface expression of the southern Delmarva Peninsula 

and indicates a possible relationship between the structural 

controls of the two areas. It should be noted that the region of 

shoaling in Nansemond County (loc. 58) is in close proximity to a 

basement graben indicated by Brown and others (1972, pi. 5). 

These shoaling areas are typified by cross-bedded shell hashes 

that contain abundant Ophiomorpha burrows. The units of the 

Yorktown in which this shoaling occurs correlate with deeperwater beds to the west and are unrelated to the regressive phase 

of the later parts of the Yorktown.

Within the Cobham Bay Member of the Eastover 

Formation, westward dipping beds may be seen for about 5 km in 

the vicinity of Bowlers Wharf on the Rappahannock River. The 

dip appears to be primary and to reflect patterns of 

sedimentation within the member. Beds are progressively 

sandier to the east. Behind this high area, clay accumulated 

during Cobham Bay time west of Bayport (loc. 4). This suggests 

that structural activity created a high area which locally 

controlled sedimentary patterns within the Cobham Bay 

Member. Brown and others (1972, pi. 5) also indicated a 

presence of a basement graben in this area.

Farther downriver on the Rappahannock River, beds of 

the Cobham Bay Member also dip steeply to the west in the 

vicinity of Burhans Wharf (loc. 38). There the bivalve Isognomon 

is commonly found articulated with the ligamented area facing 

updip. The dip reflects sedimentary patterns within the member 

that are possibly related to structural controls. These beds must 

have been originally deposited at a steep angle (see fig. 25).

In addition to these locations of westwardly dipping units, 

there are regions over which the dip in particular units is 

extremely low. These regions are indicated in figure 24 and 

include the Calvert and Choptank beds on the Patuxent River 

and on the Rappahannock River. Farther south are two areas 

where the angle of the dip is very low within the Cobham Bay 

beds but extremely high within the preceding Claremont Manor 

beds. On the Mattaponi River from White Oak Landing to the 

Mattaponi Indian Reservation, a distance of about 5 km, the 

upper surface of the Claremont Manor Member drops about 12m 

in elevation. Along the James River from Burrowsville to
CHESAPEAKE GROUP, MIDDLE ATLANTIC COASTAL PLAIN D53

Figure 25. View of the cliffs at Burhans Wharf (loc. 38) on the Rappahannock 

River showing the beds dipping steeply upriver (northwest).

Claremont Wharf, a distance of 12 km, the lower surface of 

Claremont Manor Member drops from sea level to 20 m below 

sea level. At the Mattaponi and at the James River locations, 

the Cobham Bay Member is extremely thin as the areas 

apparently became relatively positive after Claremont Manor 

time, and remained positive during Yorktown time.

Cobham Bay beds also thin over two other high areas. At 

Hopewell, the entire Eastover Formation pinches out on top of 

glauconitic Eocene sands and the Yorktown beds are extremely 

thin. In close proximity to the west of Hopewell, Eocene beds 

can be seen at water level, and nearby to the west, Cretaceous 

outcrops are 24 m thick. This area at Hopewell is herein 

referred to as the Hopewell High.

Another high area occurring to the north of the Hopewell 

High is centered in the vicinity of Bottoms Bridge in eastern 

Henrico County. In that area, the Cobham Bay Member thins to 

10 cm in thickness over a moderately thick Claremont Manor 

Member. This high area is herein referred to as the Bottoms 

Bridge High. This feature is suggested by the structural contour 

map of Cederstrom (p. 56, fig. 6) and in the basement maps of 

Brown and others (1972, pi. 5) that show a graben in the vicinity 

of this high area.

Regional structural activity is also indicated for the 

innermost parts of the Coastal Plain. The Miocene-Pliocene 

boundary at Petersburg is at 30 m elevation, bham Bay Member 

is extremely thin as the areas apparently became relatively 

positive after Claremont Manor time, and remained positive 

during Yorktown time.
D54 CONTRIBUTIONS TO STRATIGRAPHY

Cobham Bay beds also thin over two other high areas. At 

Hopewell, the entire Eastover Formation pinches out on top of 

glauconitic Eocene sands and the Yorktown beds are extremely 

thin. In close proximity to the west of Hopewell, Eocene beds 

can be seen at water level, and nearby to the west, Cretaceous 

outcrops are 24 m thick. This area at Hopewell is herein 

referred to as the Hopewell High.

Another high area occurring to the north of the Hopewell 

High is centered in the vicinity of Bottoms Bridge in eastern 

Henrico County. In that area, the Cobham Bay Member thins to 

10 cm in thickness over a moderately thick Claremont Manor 

Member. This high area is herein referred to as the Bottoms 

Bridge High. This feature is suggested by the structural contour 

map of Cederstrom (p. 56, fig. 6) and in the basement maps of 

Brown and others (1972, pi. 5) that show a graben in the vicinity 

of this high area.

Regional structural activity is also indicated for the 

innermost parts of the Coastal Plain. The Miocene-Pliocene 

boundary at Petersburg is at 30 m elevation. At Richmond, 

Miocene and Pliocene beds are absent, although the marine 

Cobham Bay Member is above 48 m elevation.

LOCALITY REGISTER

Locality, county, state, map reference: 

(USGS)

26025 1. 0.8 km above Mount Pleasant, right bank of 

James River, Surry County, Va., Surry 71/2 min 

quad.

26026 2. 2.7 km below Bowlers Wharf, right bank of 

Rappahannock River, Essex County, Va., 

Morattico 7 1/2 min quad.

26027 3. Laytons Landing, right bank of the Rappahannock 

River, Essex County, Va., Morattico 7 1/2 min 

quad.

26028 4. Bayport, right bank of the Rappahannock River, 

Middlesex County, Va., Morattico 7 1/2 min quad.

26029 5. Right bank of Urbanna Creek, 0.5 km above the 

Rte. 227 Bridge, Middlesex County, Va., Urbanna 

7 1/2 min quad.

26030 6. Warren Bros., Henrico Pit, 0.8 km SW of 

intersection of Rte. 33 and Rte. 60, near 

Bottom's Bridge, south of the Chickahominy 

River, Henrico County, Va., Quinton 7 1/2 min 

quad.

26031 7. Just below the mouth of Sunken Meadow Creek, 

right bank of the James River, Surry County, Va., 

Clare mont 7 1/2 min quad.
CHESAPEAKE GROUP, MIDDLE ATLANTIC COASTAL PLAIN D55

26032 8. Behind (just east of) the Richmond City jail at 

the corner of Fair field Ave. and 17th St., 

Richmond, Va., Richmond 7 1/2 min quad.

26033 9. Fones Cliffs, 1 km above Carters Wharf, left 

bank of the Rappahannock River, Richmond 

County Va., Champlain 7 1/2 min quad.

26034 10. Carthagena Creek, 1 km above the Rte. 244 

Bridge, in a western branch, St. Marys County, 

Md., St. Marys City 7 1/2 min quad.

26035 11. Rickahock, left bank of the Mattaponi River, 

King and Queen County, Va., King and Queen 

Court House 7 1/2 min quad.

26036 12. Elsing Green, left bank of the Pamunkey River, 

King William County, Va., Tunstall 7 1/2 min 

quad.

26037 13. Just below the mouth of Baileys Creek, right 

bank of the James River, in gully at dead end of 

Rte. 644, Prince George County, Va., Westover 7 

1/2 min quad.

26038 14. Colonial Heights, in creek at dead end of 

Chesterfield Ave., Chesterfield County, Va., 

Petersburg 7 1/2 min quad.

26039 15. Boat launching ramp just below the Rte. 258 

bridge on the left bank of the Meherrin River at 

Murfreesboro, Hertford County, N.C., unmapped 

quad.

26040 16. Just below the Wilcox Lake Spillway, Petersburg, 

Va., Petersburg 7 1/2 min quad.

26041 17. Just above the mouth of Sunken Meadow Creek, 

right bank of the James River, Surry County, Va., 

Claremont 7 1/2 min quad.

26042 18. Bluffs at, and just below, the mouth of Upper 

Chippokes Creek at Claremont Manor, 1.5 km 

northwest of Claremont, right bank of the James 

River, Surry County, Va., Claremont 7 1/2 min 

quad.

26043 19. Poor Creek at Fort Stedman, Petersburg National 

Battlefield Park, Prince George County, Va., 

Prince George 7 1/2 min quad.

26044 20. 1.4 km above Coggins Point, right bank of the 

James River at Tar Bay, Prince George County, 

Va., Westover 7 1/2 min quad.

26045 21. Gravatts Mill on Millpon Creek, King William 

County, Va., Hanover 7 1/2 min quad.

26046 22. White Oak Landing, right bank of Mattaponi 

River, King William County, Va., King and Queen 

Court House 7 1/2 min quad.
D56 CONTRIBUTIONS TO STRATIGRAPHY

26047 23. Mantua Landing, right bank of Mattaponi River, 

King William County, Va., King and Queen Court 

House 7 1/2 min quad.

26048 24. Westmorland State Park, at the eastern end of 

Horsehead Cliffs, right bank of the Potomac 

River, Westmorland County, Va., Stratford Hall 

7 1/2 min quad.

26049 25. 0.1 km west of Rte. 31 and Rte. 604 intersection 

and 1.5 km NW of Rte. 604, Sussex County, Va., 

Dendron 7 1/2 min quad.

26050 26. 0.2 km above Rte. 647 Bridge at Reedy Mill, left 

bank of Mattaponi River, Caroline County, Va., 

Penola 7 1/2 min quad.

26051 27. Well at Crisfield, Somerset Co., Md. N. H. 

Darton, collector, 1891. Burton Water Co., 

Drillers.

26052 28. 0.8 km below Cobham Wharf, right bank of James 

River, Surry County, Va., Surry 7 1/2 min quad.

26053 29. Bluffs just above Murfreesboro, right bank of 

Meherrin River, Hertford County, N.C., 

unmapped quad.

Right bank of the Nottoway River, 100 m below 

Rte. 631 Bridge, Sussex County, Va., Sebrell 7 

1/2 min quad.

Grove Wharf, left bank of James River, 8 km 

below mouth of Grove Creek, James City 

County, Va., Hog Island 7 1/2 min quad. 

0.3 km southwest of Tunstall Station, in a deep 

ravine and tributary to Black Creek, New Kent 

County, Va., Tunstall 7 1/2 min quad. 

2.1 km northwest of Romancoke, left bank of the 

Pamunkey River, King William County, Va., West 

Point 7 1/2 min quad.

Madison Creek, 1.2 km northwest of Colosse 

Baptist Church (on Rte. 30), King Williams 

County, Va., King and Queen Court House 7 1/2 

min quad.

26059 35. 0.8 km above Wakema, right bank of the 

Mattaponi River, King William County, Va., King 

and Queen Court House 7 1/2 min quad.

26060 36. Courthouse Landing, left bank of the Mattaponi 

River, King and Queen County, Va., King and 

Queen Court House 7 1/2 min quad.

26061 37. Just below mouth of Whiting Creek, right bank of 

Rappahannock River, Middlesex County, Va., 

Saluda 7 1/2 min quad.

26062 38. Burhans Wharf, 1.6 km above the mouth of 

Whiting Creek, right bank of the Rappahannock

26054

26055

26056

26057

26058

30.

31.

32.

33.

34.
CHESAPEAKE GROUP, MIDDLE ATLANTIC COASTAL PLAIN D57

River, Middlesex County, Va., Saluda 7 1/2 min 

quad.

26063 39. Freeport, just above the mouth of Harper Creek, 

right bank of the Piankatank River, Gloucester 

County, Va., Saluda 7 1/2 min quad.

26064 40. Elands Wharf, just below the mouth of Harper 

Creek, right bank of the Piankatank River, 

Gloucester County, Va., Saluda 7 1/2 min quad.

26065 41. Along Hull Creek, right bank of the Potomac

River, Northumberland County, Va., Heathsville 

7 1/2 min quad.

26066 42. 1.3 km below mouth of Sunken Meadow Creek, 

right bank of the James River, Surry County, Va., 

Claremont 7 1/2 min quad.

26067 43. Lieutenant Run, upstream of the Baylor Lane 

Bridge, Petersburg, Va., Petersburg 7 1/2 min 

quad.

26068 44. Fleets Mill Pond, 1.5 km southeast of Shepherds 

Church and Rte. 360 on Rte. 631, King and Queen 

County, Va., Aylett 7 1/2 min quad.

26069 45. 0.1 km northeast of Pauls Cross Roads, in 

roadcut of Rte. 360, just south of Piscataway 

Creek, Essex County, Va., Millers Tavern 7 1/2 

min quad.

26070 46. 0.1 km below the mouth of Felgates Creek, right 

bank of the York River, York County, Va., Clay 

Bank 7 1/2 min quad.

26071 47. Right bank of the Trent River, just below the 

mouth of Brice Creek, Jones County, N.C., New 

Bern 7 1/2 min quad.

26072 48. 0.1 km below Mill Creek, left bank of the Neuse 

River, Pamlico County, N.C., Cherry Point 7 1/2 

min quad.

26073 49. Texasgulf, Inc., phosphate pit north of Aurora, 

right bank of the Pamlico River, Beaufort 

County, N.C., Bath 7 1/2 min quad.

26074 50. Left bank of the Nottoway River at Sycamore 

Bend, Southampton County, Va., Franklin 7 1/2 

min quad.

26075 51. Trego Quarry, 2.8 km WSW of Skippers, 

Greensville County, Va., Skippers 7 1/2 min quad.

26076 52. Banks of a northward flowing tributary to 

Quankey Creek, north side of North Carolina 

Rte. 561, 0.8 km west of railroad crossing over 

Rte. 651 in Halifax, Halifax County, N.C., 

unmapped quad.

26077 53. Colerain Landing, 1.6 km east of Colerain, right 

bank of the Chowan River, Bertie County, N.C., 

unmapped quad.
D58 CONTRIBUTIONS TO STRATIGRAPHY

26078 54. Edenhouse Landing, 0.8 km above Edenhouse 

Point, right bank of the Chowan River, Bertie 

County, N.C., Edenton 15 min quad.

26079 55. 1.0 km below Morgarts Beach, right bank of the 

James River, Isle of Wight County, Va., Mulberry 

Island 71/2 min quad.

26080 56. Bluffs at the Moore House, right bank of the 

York River, in the Colonial National Historical 

Park, York County, Va., Poquoson West 7 1/2 min 

quad.

26081 57. Point of Rocks, 1.2 km below Yorktown on the 

right bank of the York River, York County, Va., 

Poquoson West 7 1/2 min quad.

26082 58. Lone Star Cement Co. Quarry (abandoned), 0.1 

km north of Chuckatuck and east of Rtes. 10 and 

32, Nansemond County, Va., Chuckatuck 7 1/2 

min quad.

Glebe Neck, 0.1 km below the mouth of Wilton 

Creek, left bank of the Piankatank River, 

Middlesex County, Va., Wilton 7 1/2 min quad. 

Roadcut 0.6 km northeast of Manquin on Rte. 

360, King William County, Va., Manquin 7 1/2 

min quad.

0.7 km east of Rushmere, right bank of the 

James River, Isle of Wight County, Va., Bacons 

Castle 7 1/2 min quad.

1.2 km east of Palmyra, right bank of the 

Roanoke River, Martin County, N.C., Palmyra 7 

1/2 min quad.

Biddle Landing, right bank of the Neuse River, 

3.2 km north of Ft. Barnwell, Craven County, 

N.C., Ayden 15 min quad.

Martin Marietta Co., New Bern Quarry, 

northwest of New Bern, 0.8 km northeast of Rte. 

55 on County Road 1402, Craven County, N.C., 

New Bern 15 min quad.

26089 65. Cornwallis' Cave at Yorktown Beach, right bank 

of the York River, York County, Va., Yorktown 7 

1/2 min quad.

26090 66. Ravine leading down to Matoaka Lake, 0.2 km 

west of Gary Stadium, Williamsburg, Va., 

Williamsburg 7 1/2 min quad.

26091 67. Essex Mill, 2.2 km west of Dunnsville, Essex 

County, Va., Dunnsville 7 1/2 min quad.

26092 68. Mt. Airy Mill Pond, just off Rte. 621, Richmond 

County, Va., Tappahnnock 7 1/2 min quad.

26093 69. Just south of ConneUee Mill Pond in roadcut on 

Rte. 621, Richmond County, Va., Tappahannock 7 

1/2 min quad.

26083

26084

26085

26086

26087

26088

59.

60.

61.

62.

63.

64.
CHESAPEAKE GROUP, MIDDLE ATLANTIC COASTAL PLAIN D59

26094 70. Wilmont Wharf, left bank of Rappahannock 

River, King George County, Va., Rollins Fork 7 

1/2 min quad.

26095 71. Butylo, right bank of the Rappahannock River, 

Middlesex County, Va., Morattico 71/2 min quad.

26096 72. Roadcut of Rte. 360 at the Pamunkey River, 

King William County, Va., Old Church 7 1/2 min 

quad.

Sycamore bend, right bank of the Pamunkey 

River, Hanover County, Va., Old Church 7 1/2 

min quad.

Piping Tree Ferry, left bank of the Pamunkey 

River, King William County, Va., King William 7 

1/2 min quad.

Matadequin Creek, right bank of Pamunkey 

River, New Kent County, Va., Tunstall 7 1/2 min 

quad.

Montague Landing, left bank of the Pamunkey 

River, King William County, Va., Tunstall 7 1/2 

min quad.

Below Putneys Mill at end of Rte. 607, right bank 

Pamunkey River, New Kent County, Va., Tunstall 

7 1/2 min quad.

1.6 km below White Landing, left bank of the 

Pamunkey River, King William County, Va., New 

Kent 7 1/2 min quad.

Just below Brickhouse Landing, left bank of the 

Pamunkey River, King William County, Va., New 

Kent 7 1/2 min quad.

Chippokes Plantation State Park, right bank of 

the James River, Surry County, Va., Cobham Bay 

7 1/2 min quad.

26105 81. 1 km below Kingsmill Wharf, James City County, 

Va., Cobham Bay 7 1/2 min quad.

26106 82. Martiau 1.6 km below Horse Pt., left bank of the 

Piankatank River, Middlesex County, Va., Wilton 

7 1/2 min quad.

26107 83. 1.6 km above Popes Creek, left bank of the 

Potomac River, Charles County, Md., Mathias 

Point 7 1/2 min quad.

26108 84. 2 km below Popes Creek, left bank of the 

Potomac River, Charles County, Md., Colonial 

Beach North 71/2 min quad.

26109 85. Coles Point, right bank of the Potomac River, 

Westmoreland County, Va., St. Clements Island 7 

1/2 min quad.

26110 86. 1 km below Eastover, right bank of the James 

River, Surry County, Va., Claremont 7 1/2 min 

quad.

26097

26098

26099

26100

26101

26102

26103

26104

73.

74.

75.

76.

77.

78.

79.

80.
D60 CONTRIBUTIONS TO STRATIGRAPHY

26111 87. Haynes Mill, where Rte. 614 crosses Carter 

Creek, Gloucester County, Va., Clay Bank 7 1/2 

min quad.

26112 88. Rices Borrow Pit, off Harris Creek Road in 

Hampton, Va., Hampton 7 1/2 min quad.

26113 89. 1 km above Morgarts Beach, right bank of the 

James River, Isle of Wight County, Va., Mulberry 

Island 7 1/2 min quad.

26114 90. Morgarts Beach, right bank of the James River, 

Isle of Wight County, Va., Mulberry Island 7 1/2 

min quad.

26115 91. Excavation for sewage treatment plant in 

Waverly, Sussex County, Va., Waverly 7 1/2 min 

quad.

REFERENCES CITED

Akers, W. H., 1972, Planktonic Foraminifera and biostratigraphy

of some Neogene formation, northern Florida and Atlantic

Coastal Plain: Tulane Studies in Geology and Paleontology,

v. 9, no. 1-4, 139 p. 

Berggren, W. A., and van Couvering, J. A., 1974, The late

Neogene Biostratigraphy, geochronology and

paleoclimatology of the last 15 million years in marine and

continental sequences: Palaeogeography, Palaeoclimatology,

Palaeoecology, v. 16, no. 1-2, 216 p. 

Brown, P. M., Miller, J. A., and Swain, F. M., 1972, Structural

and stratigraphic framework, and spatial distribution of

permeability of the Atlantic Coastal Plain, North Carolina

to New York: U. S. Geological Survey Professional Paper

796, 79 p., 59 pi. 

Clark, W.B., and Miller, B. L., 1906, A brief summary of geology

of the Virginia Coastal Plain: Virginia Geological Survey

Bulletin 2, pt. 1, p. 11-24. 

___ 1912, The physiography and geology of the Coastal Plain

province of Virginia: Virginia Geological Survey Bulletin 4,

p. 13-222. 

Ball, W. H., and Harris, G. D., 1892, Correlation papers

Neogene: U.S. Geological Survey Bulletin 84, 349 p. 

Barton, N. H., 1891, Mesozoic and Cenozoic formation of

eastern Virginia and Maryland: Geological Society of

America Bulletin, v. 2, p. 431-450. 

Gibson, T. G., 1970, Late Mesozoic-Cenozoic tectonic aspects of

the Atlantic coastal margin: Geological Society of America

Bulletin, v. 81, no. 6, p. 1813-1822. 

___ 1971, Miocene of the Middle Atlantic Coastal Plain, in

Gernant, R. E., Gibson, T. G., and Whitmore, F. C., Jr.,
CHESAPEAKE GROUP, MIDDLE ATLANTIC COASTAL PLAIN D61

Environmental history of Maryland Miocene, Field Trip 5 of 

Geological Society of America, Annual Meeting: Maryland 

Geological Survey Guidebook 3, p. 1-15.

Goddard, E. N., and others, 1948, Rock-color chart: Washington, 

D. C., National Research Council; reprinted by Geological 

Society of America, 1951, 1963,1970, 6 p.

Johnson, G. H., and Goodwin, B. K., 1969, Guidebook to the 

geology of the York-James Peninsula and south bank of the 

James River Atlantic Coastal Plain Geologic Association, 

10th Annual Field Conference, and 1st Annual Virginia 

Geologic Field Conference: Williamsburg, Va., College of 

William and Mary (Department of Geology Guidebook 1), 33

PMansfield, W. C., 1927, The Miocene stratigraphy of Virginia,

based upon the study of the faunas: George Washington

University, unpub. Ph.D thesis, 156 p. 

___ 1928, New fossil mollusks from the Miocene of Virginia and

North Carolina, with a brief outline of the divisions of the

Chesapeake group: U.S. National Museum Proceedings, v.

74, art. 14, 11 p. 1929 . 

___ 1931, The Miocene stratigraphy of Virginia based upon the

study of faunas: George Washington University Bulletin,

Summaries of Doctoral Theses 1925-1928, p. 91-96. 

__ 1943, Stratigraphy of the Miocene of Virginia and the

Miocene and Pliocene of North Carolina, in Gardner, Julia,

Mollusca from the Miocene and lower Pliocene of Virginia

and North Carolina: Pt. 1, Pelecypoda: U.S. Geological

Survey Professional Paper 199-A, p. 1-19. 

McGee, W. J., 1888, Three formations of the Middle Atlantic

slope: American Journal Science, ser. 3, 35, p. 120-143,

328-330, 367-388, 448-466. 

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Washington and its scientific institutions, prepared by the

local committee for the International Congress of

Geologists, 5th session, Washington, 1891: pp. 38-64. 

Olsson, Axel, 1917, The Murfreesboro stage of our east coast

Miocene: Bulletins of American Paleontology, v. 5, no. 28,

11 p. (v. 5, p. 155-163). 

Teifke, R. H., 1973, Stratigraphic units of the lower Cretaceous

through Miocene series: Virginia Division of Mineral

Resources Bulletin 83, part 1, p. 1-78. 

Weems, R. E., 1968, The Virginia Miocene: Randolph-Macon

College Sci. Mag., v. 3, p. 15, 16. 

Wilmarth, M. G., 1957, Lexicon of Geologic Names of the United

States: U.S. Geological Survey Bulletin 896, pt. 1, p. 1128-

1129.
PLATE 1

Figure 1. Isognomon sp.

Right valve of a nearly complete specimen "(USNM 258347), 

from Cobham Wharf, Va. (loc. 28) (USGS loc. 26052), length 

150.3 mm.

2. Ecphora sp.

Apertural view of specimen (USNM. 258348), from just 

above Sunken Meadow Creek on the James River, Va. (loc. 

17) (USGS loc. 26041), height 74.4 mm.

3. Mereenaria sp.

Left valve of specimen (USNM 258349), from just above 

Sunken Meadow Creek on the James River, Va. (loc. 17) 

(USGS loc. 26041), length 93.5 mm, height 75.9 mm.

4. Glycymeris virginiae (Pall, 1898)

Left valve of specimen (USNM 258350), from Cobham 

Wharf, Va. (loc. 28) (USGS loc. 26052), length 60.5 mm, 

height 65.1 mm.

5. Scapharea virginiae (Pall, 1898)

Right valve of specimen (USNM 258351) from just above 

Sunken Meadow Creek on the James River, Va. (loc. 17) 

(USGS loc. 26041), length 82.2 mm, height 57.3 mm.

6. Lirophora dalli (Olsson, 1914)

Right valve of specimen (USNM 258352) from Cobham 

Wharf, Va. (loc. 28) (USGS loc. 26052), length 19.3 mm, 

height 17.2 mm.

7. Scapharea clisea (Pall, 1898)

Left valve of specimen (USNM 258353), from just above 

Sunken Meadow Creek on the James River Va. (loc. 17) 

(USGS loc. 26041), length 42.7 mm, height 44.1 mm.

8. Glossus fraterna (Say. 1824)

Left valve of specimen (USNM 258354), from just below the 

mouth of Upper Chippokes Creek on the James River, Va. 

(loc. 18) (USGS loc. 26042), length 87.3 mm, height 80.2 mm.

9. Euloxa latisulcata (Conrad, 1839)

Left valve of an incomplete specimen (USNM 258355), from 

just below the mouth of Upper Chippokes Creek on the 

James River, Va. (loc. 18) (USGS loc. 26042), approx. length 

15.0 mm, approx. height 13.1 mm.

10. Ostreasp.

Left valve of specimen (USNM 258356), from just above 

Sunken Meadow Creek on the James River, Va. (loc. 17) 

(USGS loc. 26041), length 97.7 mm, height 111.9 mm.

11. Turritella sp. aff. T. plebeia (Say, 1824)

Apertural view of incomplete specimen (USNM 258357), 

from just below the mouth of Upper Chippokes Creek on the 

James River, Va. (loc. 18) (USGS loc. 26042), height 24.3 

mm.

12. Chesapeeten middlesexensis (Mansfield, 1936)

Right valve of specimen (USNM 258358), from just above 

Sunken Meadow Creek on the James River, Va. (loc. 17) 

(USGS loc. 26041), length 98.8 mm, height 91.4 mm.
GEOLOGICAL SURVEY BULLETIN 1482-D PLATE 1

12

COMMON BIVALVES AND GASTROPODS FROM THE CLAREMONT 

MANOR MEMBER OF THE EASTOVER FORMATION
PLATE 2

Figure 1. Placopecten princepoides (Emmons, 1858)

Right valve of a topotype specimen (USNM 258359), from 

just above Murfreesboro, N.C., on the Meherrin River (loc. 

29) (USGS loc. 26053), length 155.8 mm, height 140.0 mm. 

2,3. Scapharca carolinensis (Pall, 1897)

2. Right valve of a complete specimen (USNM 258360), from 

2.7 km below Bowlers Wharf on the Rappahannock River, 

Va. (loc. 2) (USGS loc. 26026), length 44.9 mm, height 46.7 

mm.

3. Left valve of same specimen (USNM 258360), length 44.7 

mm. height 46.8 mm.

4. Glycymeris sp.

Right valve of specimen (USNM 258361), from Cobham 

Wharf, Va. (loc. 28) (USGS loc. 26052), length 29.2 mm. 

height 27.9 mm.

5. "Pecten" urbannaensis (Mansfield, 1928)

Right valve of specimen (USNM 258362), from Cobham 

Wharf, Va. (loc. 28) (USGS loc. 26052), length 77.3 mm, 

height 73.5 mm.

6. Chesapecten middlesexensis (Mansfield, 1936)

Right valve of specimen (USNM 258363) from Urbanna 

Creek, Middlesex County, Va. (loc. 5) (USGS loc. 26029 

length 115.2 mm, height 110.1 mm.
GEOLOGICAL SURVEY BULLETIN 1482-D PLATE 2

COMMON BIVALVES FROM THE COBHAM BAY 

MEMBER OF THE EASTOVER FORMATION
PLATE 3

Figure 1. Isognomon sp.

Right valve of a nearly complete specimen (USNM 258364), 

from Burhans Wharf on the Rappahannock River, Va. (loc. 

38) (USGS loc. 26062), length 225.0 mm.

2. Astarte rappahannockensis (Gardner, 1943)

Left valve of specimen (USNM 258365), from just below 

Sunken Meadow Creek on the James River, Va. (loc.7), 

(USGS loc. 26031), length 21.9 mm, height 19.8 mm.

3. Euloxa latisulcata (Conrad, 1839)

Left valve of specimen (USNM 258366), from Cobham 

Wharf, Va. (loc. 28) (USGS loc. 26052), length 20.9 mm, 

height 18.9 mm.

4. Mercenaria sp.

Left valve of specimen (USNM 258367), from Urbanna Creek 

just above Urbanna, Va. (loc. 5) (USGS loc. 26029) length 

75.5 mm, height 63.3 mm. 

5, 6. Spisula rappahannockensis (Gardner, 1943)

5. Left valve of specimen (USNM 258368), from 2.7 km below 

Bowlers Wharf on the Rappahannock River, Va. (loc. 2) 

(USGS loc. 26026), length 27.2 mm, height 18.8 mm.

6. Interior of right valve of specimen (USNM 258369), from 

same locality as that shown in fig. 5, length 28.0 mm, height 

19.0 mm. 

7. Ostrea compressirostra (Say, 1824)

Left valve of specimen (USNM 258370), from 

Cobham Wharf, Va. (loc. 28) (USGS loc. 26052), length 90.1 

mm, height 106.8 mm.
GEOLOGICAL SURVEY LETIN 1482-D PLATE 3

COMMON BIVALVES FROM THE COBHAM BAY 

MEMBER OF THE EASTOVER FORMATION
PLATE 4

Figure 1. Placopecten clintonius (Say. 1824)

Right valve of specimen (USNM 258371), from just below 

Sunken Meadow Creek on the James River, Va. (loc. 7) 

(USGS loc. 26031), length 129.0 mm, height 127.3 mm. 

2. Chesapecten jeffersonius (Say, 1824)

Left valve of specimen (USNM 258372) from 1.0 km below 

KingsmiU Wharf on the James River, Va. (loc. 81) (USGS loc. 

26105), length 98.6 mm, height 91.1 mm. 

3, 4. Pycnodonte sp.

Exterior and interior views of the left valve of a specimen 

(USNM 258373), from 1 km below Eastover on the James 

River, Va. (loc. 86) (USGS loc. 26110), length 63.5 mm, 

height 67.1 mm.

5. Ostrea compressirostra (Say, 1824)

Left valve of specimen (USNMN 258374) from just below 

Sunken Meadow Creek on the James River, Va. (loc. 7) 

(USGS loc. 26031), length 83.2 mm, height 77.8 mm.

6. Busy con maximum (Conrad, 1839)

Apertural view of incomplete specimen (USNM 258375), 

from Martiau on the Piankatank River, Middlesex County, 

Va. (loc. 82) (USGS loc. 26106), length?, height 92.1 mm.

7. Panopea reflexa Say, 1824

Left valve of specimen (USNM 258376), from just below 

Sunken Meadow Creek on the James River, Va. (loc. 7) 

(USGS loc. 26031), length 124.4 mm, height 74.0 mm.

8. Mercenaria sp.

Right valve of specimen, (USNM 258377), from just below 

Sunken Meadow Creek on the James River, Va. (loc.7) (USGS 

loc. 26031), length 108.5 m, height 94.0 mm.

9. Astarte deltoidea (Gardner, 1943)

Right valve of specimen (USNM 258379), from just below 

Sunken Meadow Creek on the James River, Va. (loc. 7) 

(USGS loc. 26031), length 24.2 mm, height 25.6 mm.

10. Astarte vaginulata (Pall, 1903)

Right valve of specimen (USNM 258379) from just 

below Sunken Meadow Creek on the James River, Va. (loc. 

7) (USGS loc. 26031), length 25.3 mm, height 22.0 mm.

11. Ecphora quadricostata (Say, 1824)

Apertural view of specimen (USNM 258380), from Haynes 

Mill, Gloucester Co., Va. (loc. 87) (USGS loc.26111), height 

119.8 mm.
GEOLOGICAL SURVEY BULLETIN 1482-D PLATE 4

COMMON BIVALVES AND GASTROPODS FROM THE SUNKEN 

MEADOW MEMBER OF THE YORKTOWN FORMATION
PLATE 5

Figure 1. Chesapecten septenarius (Say, 1824)

Right valve of specimen (USNM 258381) from Lieutenant 

Run in Petersburg, Va. (loc. 43) (USGS loc. 26067), length 

68.8 mm, height 66.3 mm.

2. Chesapecten madisonius (Say, 1824)

Right valve of specimen (USNM 258381) from Lieutenant 

Run in Petersburg, Va. (loc. 43) (USGS loc. 26067), length 

68.8 mm, height 66.3 mm.

3. Fusinus exilus (Conrad, 1832)

Apertural view of specimen (USNM 258383), from 1.0 km 

below Morgarts Beach on the James River, Va. (loc. 55) 

(USGS loc. 26079), height 50.3 mm.

4. Busycon maximum (Conrad, 1839)

Apertural view of specimen (USNM 258384), from Rices 

Borrow Pit in Hampton, Va. (loc. 88) (USGS loc. 26112), 

height 260.0 mm.

5. Ostrea raveneliana Tuomey and Holmes, 1855

Left valve of specimen (USNM 258385), from 1.0 km below 

Morgarts Beach on the James River, Va.(loc. 55) (USGS loc. 

26079), length 102.5 mm, height 114.3 mm.

6. Ostrea sculpturata Conrad, 1840

Left valve of specimen (USNM 258386), from Rices Borrow 

Pit in Hampton, Va. (loc. 88) (USGS loc. 26112), length 42.1 

mm, height 57.2 mm.

7. Astarte undulata (Say 1824)

Right valve of specimen (USNM 258387), from 1.0 km above 

Morgarts Beach on the James River, Va. (loc. 89) (USGS loc. 

26113), length 28.4 mm, height 26.4 mm.

8. Glycymeris tuomeyi (Pall, 1898)

Right valve of specimen (USNM 258388 from Morgarts 

Beach on the James River, Va.doc. 90) (USGS loc. 26114), 

length 35.5 mm height 31.8 mm.

9. Glycymeris americana (DeFrance, 1826)

Right valve of specimen (USNM 258389), from Morgarts 

Beach on the James River, Va. (loc. 90) (USGS loc. 26114), 

length 60.7 mm, height 55.6 mm. 

10. Mercenaria tridacnoides rileyi (Conrad,1838)

Right valve of specimen (USNM 258390), from Lieutenant 

Run in Petersburg, Va. (loc. 43) (USGS loc. 26067), length 

94.0 mm, height 70.2 mm 

11, 12. Pseudochama corticosa (Conrad,1833)

Exterior and interior views of the right valve of a specimen 

(USNM 258391), from Morgarts each on the James, Va. 

(loc.90) (USGS loc. 26114), River, length 46.1 

mm, height 51.5 mm.

13. Astarte concentrica (Conrad, 1834)

Right valve of specimen (USNM 258392), from Lieutenant 

Run in Petersburg, Va. (loc. 43) (USGS loc. 26067), length 

22.6 mm, height 20.5 mm.

14. Mulinia congesta (Conrad,1833)

Right valve of specimen (USNM 258393), from Waverly, 

Sussex County, Va. (loc. 91) (USGS loc. 26115), length 17.4 

mm, height 12.9 mm.

15. Mercenaria tridacnoides (Lamarck, 1818)

Right valve of specimen (USNM 258394), from Lieutenant 

Run in Petersburg, Va. (loc. 43) (USGS loc. 26067), length 

106.1 mm, height 83.8 mm.

16. Planicardium virginianum (Conrad, 1839)

Left valve of specimen (USNM 258395), from Rices Borrow 

Pit in Hampton, Va. (loc. 88) (USGS loc. 26112), length 95.9 

mm, height 120.0 mm.
GEOLOGICAL SURVEY BULLETIN 1482-D PLATE 5

14

COMMON BIVALVES AND GASTROPODS FROM THE RUSHMERE, 

MORGARTS BEACH, AND MOORE HOUSE MEMBERS 

OF THE YORKTOWN FORMATION