Stratigraphy and Characteristic Mollusks of 

the Pamunkey Group (Lower Tertiary) and 

the Old Church Formation of the 

Chesapeake Group Virginia Coastal Plain

U.S. GEOLOGICAL SURVEY PROFESSIONAL PAPER 1346

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Stratigraphy and Characteristic Mollusks of 

the Pamunkey Group (Lower Tertiary) and 

the Old Church Formation of the 

Chesapeake Group Virginia Coastal Plain

By Lauck W. Ward

U.S. GEOLOGICAL SURVEY PROFESSIONAL PAPER 1346
DEPARTMENT OF THE INTERIOR 

DONALD PAUL HODEL, Secretary

U.S. GEOLOGICAL SURVEY 

Dallas L. Peck, Director

Library of Congress Cataloging-in-Publication Data

Ward, Lauck W.

Stratigraphy and characteristic moUusks of the Pamunkey Group (lower Tertiary) and the Old Church Formation of the 

Chesapeake Group Virginia Coastal Plain.

(U.S. Geological Survey professional paper ; 1346)

Bibliography: p. 76

Supt. of Docs, no.: I 19.16:1346

1. Geology, Stratigraphic Tertiary. 2. Mollusks, Fossil Virginia Pamunkey River Watershed. 3. Geology Virginia 

Pamunkey River Watershed.

I. Title. II. Series: Geological Survey professional paper ; 1346. 

QE691.W37 1986 564 85-600091

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

604 South Pickett Street, Alexandria, VA 22304
CONTENTS

Page

Abstract ................................................................... 1

Introduction ................................................................ 1

Acknowledgments ........................................................ 2

Stratigraphy ................................................................ 2

Pamunkey Group ........................................................ 2

Brightseat Formation ................................................. 6

Aquia Formation ..................................................... 6

Piscataway Member (revised) ....................................... 9

Paspotansa Member (revised) ....................................... 15

Marlboro Clay ....................................................... 20

Nanjemoy Formation ................................................. 25

Potapaco Member ................................................. 27

Bed A Nonbedded Potapaco ................................... 29

Bed B Bedded Potapaco ....................................... 30

Bed C Burrowed Potapaco ..................................... 35

Bed D Concretion-bed Potapaco ................................. 37

Woodstock Member ............................................... 37

Piney Point Formation ................................................ 45

Chesapeake Group ....................................................... 50

Old Church Formation ................................................ 51

Summary of lower Tertiary stratigraphy and onlap-offlap record .................... 58

Paleocene ............................................................... 58

Eocene ................................................................. 58

Oligocene ............................................................... 59

Localities and measured sections .............................................. 59

References cited ............................................................. 76

ILLUSTRATIONS

[Plates follow References cited]

PLATE

FIGURE

1.

2.

3.

4.

5.

6.

1.

2.

3.

4.

5.

6.

7.

8.

9.

10.

11.

12.

13.

14.

15.

16.

Mollusks from the Piscataway Member, Aquia Formation. 

Mollusks from the Paspotansa Member, Aquia Formation. 

Mollusks from the Potapaco Member, Nanjemoy Formation. 

Mollusks from the Woodstock Member, Nanjemoy Formation. 

Mollusks from the Piney Point Formation. 

Mollusks from the Old Church Formation.

Page

3

4

5

7

Correlation chart showing Tertiary units from New Jersey to Alabama ......................................

Major structural features of the Atlantic Coastal Plain from New York to Florida .............................

Composite stratigraphic section of Tertiary units along the Pamunkey River .................................

Locality map of exposures of the Brightseat Formation ...................................................

Photographs showing A, Aquia Creek, above Thorney Point, Stafford County, Va. (Loc. 1); B, Rappahannock River,

east of Greenfield, Spotsylvania County, Va. (Loc. 2) .................................................. 8-9

Map showing area! extent of the Brightseat Formation .................................................... 10

Map showing the area! extent of the Aquia Formation .................................................... 10

Locality map of exposures of the Piscataway Member, Aquia Formation ..................................... 11

Photograph showing the Pamunkey River, east of Wickham Crossing, Hanover County, Va. (Loc. 8) ............. 12

Photograph showing Aquia Creek, above Thorney Point, Stafford County, Va. (Loc. 1)......................... 13

Photograph showing the Pamunkey River, east of Wickham Crossing, Hanover County, Va. (Loc. 8) ............. 14

Photograph showing the James River, above the mouth of Turkey Island Cutoff, Chesterfield County, Va. (Loc. 10) 15 

Locality map of exposures of the Paspotansa Member, Aquia Formation ..................................... 16

Photographs showing A, Potomac River at Bull Bluff, King George County, Va. (Loc. 11); B, Potomac River, just below

mouth of Passapatanzy Creek, King George County, Va. (Loc. 12) ...................................... .18-19

Photograph showing the Potomac River, below Fairview Beach, King George County, Va. (Loc. 13) .............. 20

Photograph showing the Potomac River, below the mouth of Aquia Creek, Stafford County, Va. (Loc. 3). Lectostratotype of the Aquia Formation and the Piscataway and Paspotansa Members ............................... 21

ill
IV CONTENTS

Page

FIGURE 17. Photograph showing the Pamunkey River at Sturgeon Hole, Caroline County, Va. (Loc. 26) .................... 22

18. Locality map of exposures of the Marlboro Clay ......................................................... 23

19. Map showing the area! extent of the Marlboro Clay ...................................................... 24

20. Photograph showing the Mattaponi River, just below the Rte. 207 bridge, Caroline County, Va. (Loc.32) ......... 25

21. Photograph showing the Pamunkey River, below Sturgeon Hole, Caroline County, Va. (Loc. 24) ................ 26

22. Maps showing area! extent of A, the Potapaco Member, Nanjemoy Formation; B, the Woodstock Member, Nanjemoy

Formation ...................................................................................... 27

23. Locality map of exposures of the Potapaco Member, Nanjemoy Formation .................................. 28

24. Photograph showing the Pamunkey River, above Normans Bridge, King William County, Va. (Loc. 38) .......... 31

25. Photograph showing the Mattaponi River, 1.0 mile east of Reedy Mill, Caroline County, Va. (Loc. 45) ........... 32

26. Photograph showing the Potomac River, 2.5 miles upstream from Popes Creek, Charles County, Md. (Loc. 34) .... 33

27. Photograph showing the Pamunkey River, just below the boat landing at Dabneys Millpond, King William County, Va.

(Loc. 50) ....................................................................................... 34

28. Photograph showing the Mattaponi River, 0.8 mile southeast of Reedy Mill, Caroline County, Va. (Loc. 58) ....... 36

29. Photograph showing the Pamunkey River, 0.58 mile below the mouth of Totopotomoy Creek, Hanover County, Va.

(Loc. 61) ....................................................................................... 38

30. Locality map of exposures of the Woodstock Member, Nanjemoy Formation ................................. 39

31. Photograph showing the Potomac River, above Mathias Point, King George County, Va. (Loc. 67) .............. 40

32. Photograph showing the Potomac River, 0.4 mile above Popes Creek, Charles County, Md. (Loc. 53) ............. 41

33. Photograph showing the Rappahannock River, above Greenlaw Wharf, King George County, Va. (Loc. 54) ....... 42

34. Photograph showing the Pamunkey River, in a small ravine 0.63 mile south-southeast of the mouth of Totopotomoy

Creek, Hanover County, Va. (Loc. 74) ............................................................... 43

35. Photographs showing A, the Pamunkey River at the termination of Rte. 732, Hanover County, Va. (Loc. 64); B, the

Pamunkey River, 200 yards upriver of Locality 64, Hanover County, Va ................................. 44

36. Locality map of exposures of the Piney Point Formation .................................................. 47

37. Map showing the area! extent of the Piney Point Formation ............................................... 48

38. Photograph showing the Mattaponi River, 1.3 miles above the mouth of Maracossic Creek, King William County, Va.

(Loc. 73) ....................................................................................... 49

39. Photograph showing the Rappahannock River, below Wilmont Wharf, King George County, Va. (Loc. 70) ........ 50

40. Photographs showing the Pamunkey River at Horseshoe, Hanover County, Va. (Loc. 83) ...................... 51-52

41. Photograph showing the Pamunkey River at Piping Tree Ferry, King William County, Va. (Loc. 84) ............. 53

42. Photograph showing the Pamunkey River below Retreat, Hanover County, Va. (Loc. 85) ....................... 54

43. Locality map of exposures of the Old Church Formation .................................................. 55

44. Photograph showing the Patuxent River at the "Kaylorite" pit at the termination of Landing Road, Calvert County,

Md. (Loc. 65) ................................................................................... 56

45. Photograph showing the Patuxent River at White Landing, Prince Georges County, Md. (Loc. 66) .............. 57

46. Map showing the areal extent of the Old Church Formation ............................................... 58

47. Chart showing onlap-offlap history of the Atlantic Coastal Plain ........................................... 60-61
STRATIGRAPHY AND CHARACTERISTIC MOLLUSKS OF THE

PAMUNKEY GROUP (LOWER TERTIARY) AND THE

OLD CHURCH FORMATION OF THE

CHESAPEAKE GROUPVIRGINIA COASTAL PLAIN

By LAUCK W. WARD

ABSTRACT

Along the Pamunkey River and its tributaries can be found a very 

complete, well-preserved, Tertiary stratigraphic record that reflects 

the sea-level changes as well as the local tectonic history of the central Virginia Coastal Plain. Using this record, I have described the 

lower Tertiary units and proposed a sequential model for their occurrence. Sediments examined in this study range in age from early 

Paleocene to latest Oligocene or earliest Miocene. Upper Tertiary units 

are described where they occur in the same sections with the lower 

Tertiary beds. The Brightseat Formation (lower Paleocene), Aquia Formation (upper Paleocene), Marlboro Clay (upper Paleocene), Nanjemoy 

Formation (lower Eocene), Piney Point Formation (middle Eocene) and 

Old Church Formation (new unit, upper Oligocene and lower Miocene) 

were studied. The definitions of the Piscataway and Paspotansa 

Members of the Aquia are amended, and a lectostratotype (principal 

reference section) is designated for those units as well as the Aquia 

on the Potomac River just below the mouth of Aquia Creek. A lectostratotype section is also designated for the Nanjemoy and its two 

members, the Potapaco and the Woodstock. That section is on the 

Potomac above Popes Creek. Beds assigned to the Piney Point and 

Old Church Formations, previously known only in the subsurface, crop 

out extensively on the Pamunkey River. A hypostratotype (reference 

section) is selected for the Piney Point Formation on the Pamunkey 

River at Horseshoe. The Old Church Formation (named herein) is included in the Chesapeake Group. Area! extent of the stratigraphic units 

was determined by correlation of outcropping beds on the Pamunkey, 

Patuxent, Potomac, Rappahannock, Mattaponi, Chickahominy, and 

James Rivers supplemented by well data. Comparisons of the onlap 

histories of the Salisbury, Albemarle, and Charleston Embayments 

indicate a number of simultaneous transgressive events implying 

global sea-level rises. More restricted transgressions appear to be the 

result of local downwarping.

INTRODUCTION

The stratigraphy of the central Virginia Coastal Plain, 

and specifically of the Pamunkey River area, has been 

the subject of attention since the early 19th century. 

The earliest work was accomplished by W.B. Rogers in 

the 1830's, 1840's, and 1850's (for a complete account 

of this work see W.B. Rogers, 1884, and J.K. Roberts, 

1942). Most later work consisted of paleontological

descriptions (see, for example, Bagg, 1895, 1896; Conrad, 1843, 1847; Cope, 1896; Van Winkle, 1919, 1921; 

Van Winkle and Harris, 1919; Clark, 1896b; Clark and 

Martin, 1901). Intensive stratigraphic work began with 

Barton (1891), who used the Pamunkey River exposures 

as typical of those glauconitic units that he termed the 

Pamunkey Formation. The Pamunkey Formation was 

later mapped by Barton (1894, 1896). Work by Clark 

(1896a,b) and Clark and Martin (1901) refined and 

modified the concept of the Pamunkey Formation and 

raised the unit to group status, while dividing it into 

formations and members. Barton (1911,1948,1951) accepted this stratigraphic revision and extensively 

mapped the formations included in the Pamunkey 

Group. Clark and Miller (1912) extended their stratigraphic work into the Virginia Coastal Plain, giving sections and faunal lists from outcrops on all the important rivers. The Pamunkey River received only a small 

share of attention in this work in spite of its numerous 

exposures. Paleontological interest in beds exposed 

along the Pamunkey was revived as a result of a Cornell University collecting venture in 1897 (Van Winkle 

and Harris, 1919). Van Winkle (1919) described numerous new taxa on that expedition to the lower and middle Eocene exposures in the vicinity of New Castle, 

Hanover County, Va. Since that time, no further work 

has been published on the paleontology of that area. 

Later stratigraphic work, however, included that of 

Gildersleeve (1942), Cederstrom (1957), and Ward and 

Blackwelder (1980). None of this work has presented a 

comprehensive picture of the stratigraphic framework 

as shown by beds exposed along the Pamunkey River. 

It is the purpose of this paper to synthesize the stratigraphic framework, describe the depositional patterns, 

and correlate the various units recognized on the Pamunkey with those on the James, Chickahominy, Mattaponi, Rappahannock, Potomac, and Patuxent Rivers. 

The excellent and frequent exposures encountered on

i
STRATIGRAPHY AND MOLLUSKS OF PAMUNKEY GROUP AND OLD CHURCH FORMATION

the Pamunkey lend themselves particularly well to the 

recognition of the natural stratigraphic sequence. The 

excellence of the exposures and the fact that the entire 

sequence is exposed over a relatively short distance 

make it a fine "teaching" section. Well-exposed units, 

exhibiting both upper and lower contacts, help one to 

interpret the physical evidence of depositional breaks, 

while the various well-preserved fossil groups enable the 

paleontologist to maintain excellent chronostratigraphic control. The result is an extensive record of sealevel fluctuations and paleogeography from the Paleocene through the late Pliocene. Only the lower Tertiary 

units are described in detail in this work (fig. 1).

Two of the factors that, perhaps, stymied earlier 

research on the Pamunkey River section were the failure 

to recognize critical formational contacts and the apparently unfossiliferous nature of many of the exposures. When closely examined, the contacts between 

units are seen to be clearly defined but often intensely 

burrowed. Sampling errors are common when collecting 

near contacts because of the deep burrowing (as deep 

as 9 feet (2.7 m)) and reworking of microfossils. Further, 

in spite of the good preservation of the calcareous fossil 

groups at many exposures, in several of the units those 

taxa are poorly preserved. Pollen and dinoflagellates 

were used to help correlate these beds.

This combination of lithostratigraphic and biostratigraphic techniques has facilitated the recognition of a 

complex onlap-offlap (transgressive-regressive) history 

in the central Virginia Coastal Plain. Such a detailed 

record, together with similar information from adjoining basins, makes possible the reconstruction of global 

sea-level fluctuations independent of local tectonic 

imprint. Immediately apparent, when comparing the 

sea-level curves of the mid-Atlantic region and the Gulf 

area, are the very different tectonic and sedimentary 

histories of the two basins. The Gulf Coastal Plain was 

the site of accumulation of thick sequences of alluvial 

and deltaic sediments; tongues of marine sediment mark 

intermittent sea-level rises. The Atlantic basins 

(Salisbury, Albemarle, and Charleston Embayments) 

(see fig. 2), however, were characterized by relatively 

thin deposits, principally marine, with only remnants 

of nearshore facies. It is clear that large volumes of sediment were not being transported to the Atlantic Coastal 

Plain during the Tertiary. Marine deposition was of 

longer duration than that in the Gulf area, with fewer 

breaks, but the shallow basins accumulated relatively 

thin deposits. This pattern is well developed in the central Virginia Coastal Plain where intermittent deposition of thin marine to marginal-marine beds combined 

to record a relatively complete tectonic and depositional 

history of the area.

ACKNOWLEDGMENTS

A comprehensive chronostratigraphic framework for 

the beds exposed in the Virginia and Maryland Coastal 

Plains could not have been accomplished without the 

help of several micropaleontologists at the U.S. 

Geological Survey (USGS), Reston, Va. These were: J.E. 

Hazel (ostracodes), R.Z. Poore (planktic foraminifers), 

L.E. Edwards (dinoflagellates), N.O. Frederiksen 

(pollen), L.M. Bybell (calcareous nannofossils), and J.A. 

DiMarzio (calcareous nannofossils). Also helpful was 

P. J. Huddlestun (planktic foraminifers) of the Georgia 

Geologic Survey. Suggestions on stratigraphy were provided by R.B. Mixon (USGS, Reston), P.M. Brown 

(North Carolina Geological Survey), C.F. Koch, D.A. 

Darby, and R.S. Spencer (Old Dominion University, 

Norfolk, Va.), and G.H. Johnson (College of William and 

Mary, Williamsburg, Va.). Many of the subsurface data 

have been adapted from Brown, Miller, and Swain 

(1972). The following persons aided in the field work: 

Thor Hansen (University of Texas, Austin), B.W. 

Blackwelder (Tenneco, Houston, Tex.), G.B. Lawrence 

(Richmond, Va.), C.M. Crampsey (USGS, Reston), E.G. 

Shaw (USGS, Reston), E.E. Compton (USGS, Reston), 

G.L. Strickland (George Washington University, 

Washington, D.C.), and C.C. Morrell (Old Dominion 

University, Norfolk, Va.).

STRATIGRAPHY 

PAMUNKEY GROUP

Most of the beds now assigned to the Pamunkey 

Group were originally placed in the Pamunkey Formation by Darton (1891) and were considered to be of 

Eocene age. Describing its areal extent in some detail, 

Darton (1891) referred to the work of Rogers (see 

Rogers, 1884) and considered the exposures along the 

Pamunkey River, as described by Rogers, to be the 

typical section. (See fig. 3 for a composite section of the 

beds exposed along the Pamunkey River.) More detailed 

lithic and faunal work on the Pamunkey Formation by 

Clark (1896a,b) resulted in its division, on biostratigraphic grounds, into the "Aquia Creek stage" and the 

"Woodstock stage." Further, the beds exposed along 

the Potomac River from near Aquia Creek to Popes 

Creek were separated into 17 "clearly defined lithological zones" (Clark, 1896b, p. 39). Clark and Martin (1901)

FIGURE 1. Correlation chart showing Tertiary units in the Coastal 

Plain from New Jersey to Alabama.
SERIES

OLIGOCENE

EOCENE

PALEOCENE

STAGE NEW JERSEY DELAWARE MARYLAND

CAQLH -AINIAN} Old Church (?) Old Church ?) Old Church C

UPPER

LOWER

UPPER

MIDDLE

LOWER

UPPER

LOWER

X

<

< 1 

fe 1

X «

SJ I

X

< 

1 |

£ §§ & fc.

_. _. 

>

i i

Q C Chickahpminy

03 ? ^ z Formation (?)

e* <

B. i

/:

<

1 * ........................................................

< < 

* *

oi . . Q Pmey Point Piney Point Piney Point

<j Formation Formation Formation

W U 

h

D

/: 

< ,. _____ .-...--.--------

C/j _7 W «-: Shark River -^ -. Woodsux

B. 7 Formation £ -S Member 

> ^ S «

< Manasquan ^ g Potapacc 

Formation " ^ Member

\ arlboro Clay

?; c Paspotansa I

i Vincentown Vincentown -| '^ 

W Formation Formation 5" g Piscatawa

/^ C Member

< uI TTTT 1 1 1 1 1 1 1 1 1 1 1 

h *

,< 

> 

7. *

"7. S Brightseat Forma

<!

C

WID^IXTIA NORTH SOUTH ^TT/^O

VIRGINIA CAROLINA CAROLINA C.EOR

) Old Church (?) Format i>e ^--Tl^iYn""^ F-disto Formation Tampa Fo

a.

3

River Bend J Ashlev Suwa

r _.,-,. Lime

Formation u Formation

a.

Glendon L

Maria

......... .. .. ... .. -9- Parkers Ferrv Em. I'obano R

t.hickahqminy eg Drv Br

Formatioi ^ -j Harewille Fm. Forma

Tivola Li

.2 Spring Garden 

ra , , v Cross Member Gosport 

g Member £

U. 0;

o E 

c .. - 

>- (.omfort w 

Piney Point Member s; Moultrie 

_, . ^ Member | Lisbon Fo

Formation __; § Member 

« c«

(j New Hanover 

Member

Tallahatta F

k >, c Wood stock 

P _; Member

- .w 1 , 

, II Potapaco Fishburne Formation Hatche

Marlboro Clay Tuscah

^br c Paspotansa Mbr ' ' ^ Forma

i' cr £ Piscataway Beaufort Formation | 1 1 1 1 1 1 1 1 1 

"*" c Member 

ta Black Minso

Formation Porters 

Clay

tion Brightseat Formation ^ eau ort '^'l,",?.1"1 n-ji/t«n F,

Illlllllll

'For use of the name in Maryland see Brown and others, 1972.
STRATIGRAPHY AND MOLLUSKS OF PAMUNKEY GROUP AND OLD CHURCH FORMATION

(Irtn&r Bdufidary 

/ of Coasta) Plain S

Raritan 

Ernbayment

South New 

Jersey Arch

Norfolk Arch

Albemarle 

Ernbayment

Cape Fear Arch

Charleston Embayment 

Yamacraw Arch 

Southeast Georgia Embayment

Southwest

Georgia

Embayment

South Florida Embayment

100 200 Ml 

I i i

Ocala Arch

i \ \ 

0 100 200 KM

FIGURE 2. Major Tertiary structural features of the Atlantic Coastal 

Plain from New York to Florida. Heavy lines to east mark edges of 

depositional basins.

raised the Pamunkey Formation to group status, divided it into two formations (or "stages"), the Aquia 

and Nanjemoy, and further subdivided each of these 

into two members ("substages"). The Aquia consisted 

of (in ascending order) the Piscataway and Paspotansa 

Members, and the Nanjemoy consisted of the Potapaco 

and Woodstock Members. In the 1901 report, Clark and 

Martin used the terms "formation" and "stage" and 

"member" and "substage" interchangeably, and there 

is evidence of confusion of rock-stratigraphic and 

biostratigraphic terms. It is clear, however, that the 

Aquia and Nanjemoy Formations and their members 

were described on their lithic characteristics in a series 

of 17 beds ("zones"). Lists of fossils were made from 

each bed. Clark and Miller (1912) expanded on their 

work southward into Virginia but at that time* used only 

the terms "formation" and "member", deleting "stage" 

and "substage".

Clark and Martin (1901, p. 65) and Clark and Miller 

(1906, p. 17; 1912, p. 115) briefly mentioned a pink clay

unit that occurs at the base of the Potapaco Member. 

This bed was informally referred to as the Marlboro 

clay. The term "Marlboro clay" continued in the 

literature informally until Barton (1948) raised the unit 

to member rank. Glaser (1971) described the unit in 

considerable detail and proposed its elevation to formational status.

Further subdivision of the Pamunkey Group came 

when Bennett and Collins (1952) recognized the Brightseat Formation as lithologically and faunally distinct 

from the Aquia Formation. The Brightseat consists of 

micaceous, silty, very fine sand that was included in 

"zone" 1 by Clark and Martin (1901, p. 60). Later, 

Cederstrom (1957) introduced another and more confusing stratigraphic unit, the Mattaponi Formation, to 

include beds that he considered to be Paleocene in age. 

Observing that the first 28 feet (8.5 m) below the 

Marlboro Clay in a corehole at Colonial Beach, Va., contained Eocene foraminifers, he assigned that interval 

to the Aquia Formation. In the underlying 149 feet 

(45.4 m), Cederstrom recognized the presence of 

Paleocene foraminifers. Since the Aquia was thought 

to be Eocene, Cederstrom suggested that the term 

"Mattaponi Formation" be used for these Paleocene 

beds and the underlying 280 feet (85.3 m) of sands and 

clays (probably part of the Potomac Group). Because 

the concept of the Mattaponi was based on an age determination and because the beds included in that formation all had previously been assigned to lithic units, I 

recommend that the term be discarded.

The Piney Point Formation, a lithologically distinct 

unit, was defined on the basis of subsurface data and 

was named from a well in St. Marys County, Md. 

(Otton, 1955). The formation's distribution and lithology were discussed by Otton (1955), but its assignment 

to the upper Eocene was based on analyses by Shifflett 

(1948) of foraminifers from two Eastern Shore counties, 

far from the type area. Later work on ostracodes from 

the type well (Brown and others, 1972) showed the Piney 

Point to be middle Eocene in age. Beds of the same age 

and similar lithology crop out on the Pamunkey River 

in the type area of the Pamunkey Group. On this basis, 

the Piney Point is included as a formation within that 

group.

The youngest unit, the Chickahominy Formation, was 

recognized in the subsurface of Virginia by Cushman 

and Cederstrom (1945). This formation was recognized 

on the basis of the presence of upper Eocene foraminifers. The lithic description they provided indicated little 

difference between this unit and the underlying glauconitic Pamunkey beds. The Chickahominy is not known 

to crop out along the Pamunkey River or elsewhere on 

the Coastal Plain and is not treated in this report. Its
STRATIGRAPHY

Clay 

Sand

(birrl! Clayey silt 

lo ^V'-'ll Conglomerate 

KsriTj Clayey sand 

RivS;:.:} Fine sand

Mr1^ Silty sand 

TTT" Burrow

Concretion

NP Zones of

Martini (1971)

^^^t^j^^Vy/J-.^Jjg^g

FIGURE 3. Composite stratigraphic section showing the relationship of Tertiary units found along the 

Pamunkey River in Caroline, Hanover, King William, and New Kent Counties, Va. Thicknesses indicated 

are the average maximum thicknesses for units cropping out on the Pamunkey River.
STRATIGRAPHY AND MOLLUSKS OF PAMUNKEY GROUP AND OLD CHURCH FORMATION

lithology suggests that it should probably be included 

in the Pamunkey Group even though it was not included 

in the original description.

To summarize, formations included in the Pamunkey 

Group in this report are as follows:

Chickahominy Formation ...................... upper Eocene

Piney Point Formation ....................... middle Eocene

Nanjemoy Formation 

Woodstock Member ......................... lower Eocene

Potapaco Member ........................... lower Eocene

Marlboro Clay ................... ......... upper Paleocene

Aquia Formation 

Paspotansa Member ...................... upper Paleocene

Piscataway Member ...................... upper Paleocene

Brightseat Formation ....................... lower Paleocene

BRIGHTSEAT FORMATION

The Brightseat Formation, named by Bennett and 

Collins (1952), consists of olive-black (5 Y 2/1) (Goddard 

and others, 1948), micaceous, clayey, and silty sands. 

The Brightseat does not crop out on the Pamunkey 

River, but fieldwork during this study revealed that it 

crops out as far south as the Rappahannock River in 

Virginia. In its type area, 1 mile (1.6 km) west-southwest 

of Brightseat, Prince Georges County, Md., mollusks 

are abundant, but only the calcitic forms are well 

preserved. Away from the type area, the macrofossils 

are leached, leaving only molds and casts. In the Prince 

Georges County area, the Brightseat unconformably 

overlies marine deposits of the Severn Formation 

(Upper Cretaceous). To the south, on the Potomac and 

Rappahannock Rivers, it overlies fluvial deposits of the 

Potomac Group (Lower Cretaceous). Beds now placed 

in the Brightseat were originally assigned, with some 

reservations, to "zone" 1 of the Aquia Formation (Clark 

and Martin, 1901). Bennett and Collins (1952) pointed 

out the disconformity between the Brightseat and the 

Aquia, and this relationship was later substantiated by 

the work of Hazel (1969). (The opinion of Nogan (1964) 

and Drobnyk (1965) that this contact was gradational 

was discussed by Hazel in his paper and was shown to 

be the product of sampling near a burrowed contact between the formations.) Hazel (1969) recognized the 

presence of the Brightseat Formation in Stafford County, Va., near the mouth of Aquia Creek, on the basis 

of its lithology and stratigraphic position. On the right 

bank of Aquia Creek (Locality 1; locality descriptions 

given in section entitled "Localities and measured 

sections"; see fig. 4 for locality map), the Brightseat unconformably overlies the Patapsco Formation of the 

Potomac Group (fig. 5). The Brightseat is, in turn, 

unconformably overlain by the Aquia Formation at that 

locality. A similar sequence may be seen on the Rappahannock River, just below Fredericksburg (Locality

2) (see fig. 5B). Macrofossils there are leached and are 

present only as rare molds and casts, but the micaceous, 

silty sand, devoid of glauconite, distinguishes the unit. 

The Brightseat is not known in outcrop or the subsurface to the south of the Rappahannock River exposures 

but may be present in the Oak Grove core drilled in 

Westmoreland County, Va., and reported on by 

Reinhardt and others (1980), Gibson and others (1980), 

and Estabrook and Reinhardt (1980). A series of sandy 

clays between approximately 410 feet (125 m) and 435 

feet (138 m) below ground level was lacking in 

calcareous fossils but has been determined to be lower 

Paleocene and equivalent to the Brightseat Formation 

on the basis of dinoflagellates (oral commun., 1984, by 

L.E. Edwards, interpretation of dinoflagellate data in 

Gibson and others, 1980). The area! extent of the depositional basin of the Brightseat is shown on figure 6.

Hazel (1968, 1969) studied the ostracodes of the 

Brightseat in its type area, found the unit to be the 

equivalent of the upper Clayton Formation in Alabama, 

and placed it in the Globoconusa daubjergensisGloborotalia trinidadensis zone on the basis of its 

planktic foraminifers. Further, he showed the 

Brightseat to be early Paleocene in age and placed it 

in the upper part of the lower Danian Stage. The 

foraminifers listed by Brown and others (1977, p. 13) 

suggest the equivalency of the Brightseat to the Jericho 

Run Member of the Beaufort Formation.

Dinoflagellates were found at the type Brightseat, at 

the mouth of Aquia Creek (Locality 1), and on the Rappahannock River below Fredericksburg (Locality 2). 

These floral assemblages appear to be equivalent in age 

(L.E. Edwards, oral commun., 1984). Dinoflagellate data 

from the Oak Grove core suggest the presence of 

Brightseat in that well (L.E. Edwards, oral commun., 

1984). According to L.M. Bybell (oral commun., 1984), 

calcareous nannofossils present in the Brightseat indicate its placement in nannoplankton zone NP 3 (of 

Martini, 1971).

AQUIA FORMATION

The term "Aquia", for a stratigraphic unit, was first 

introduced by Clark (1896a,b); he gave the name "Aquia 

Creek Stage" to beds that crop out in the vicinity of 

Aquia Creek, Stafford County, Va. The concept of the 

unit was soon revised, and it was renamed the Aquia 

Formation by Clark and Martin (1901). Two members, 

the Piscataway and Paspotansa, were recognized by the 

authors. Clark and Martin (1901) expanded the work on 

the Aquia farther southward into Virginia but recognized its members only in their sections along the 

Potomac River. Bennett and Collins (1952) restricted
STRATIGRAPHY

FIGURE 4. Map showing localities where the Brightseat Formation is exposed. Numbers refer to localities mentioned in

the text.
STRATIGRAPHY AND MOLLUSKS OF PAMUNKEY GROUP AND OLD CHURCH FORMATION

FIGURE 5A Aquia Creek, above Thorney Point, Stafford County, Va. (Locality 1), 

showing contact between the Lower Cretaceous (A) and the Brightseat Formation 

(B). Section cleaned off by pick is approximately 5.0 feet (1.52 m) in length.

Clark and Martin's (1901) earlier definition of the Aquia 

by designating beds that Clark had placed in zone 1 the 

Brightseat Formation. It is the Aquia Formation, in 

this presently restricted sense, that unconformably 

overlies the Brightseat Formation, in the northeastern 

area of the Aquia's range, and Lower Cretaceous 

deposits, south of the Rappahannock River.

The Aquia consists of clayey, silty, very shelly, 

glauconitic sand; it crops out in a continuous arc from 

the upper Chesapeake Bay to the area around Hopewell 

on the James River, Va. Both members of the Aquia

may be recognized along the Potomac, Rappahannock, 

Mattaponi, Pamunkey, and James Rivers. (See fig. 7 for 

the basinal outline of the Aquia sea.) Macrofossils locally are well preserved but more commonly are leached, 

making recovery difficult. Microfossil groups consist of 

ostracodes, foraminifers, pollen, dinoflagellates, and 

calcareous nannofossils. Macrofossil and microfossil 

work has indicated that the Aquia Formation is upper 

Paleocene (Gibson and others, 1980). L. M. Bybell (oral 

commun., 1984), on the basis of calcareous nannofossils, 

placed the Aquia Formation in zones NP 5-9. The Aquia
STRATIGRAPHY

FIGURE 5B. Rappahannock River, 1.85 miles (2.98 km) east of Greenfield, Spotsylvania County, Va. (Locality 2), showing 

contact between the Lower Cretaceous (A) and the Brightseat Formation (B).

Formation is further characterized here by the description of its members.

PISCATAWAY MEMBER (REVISED)

The Piscataway Member of the Aquia Formation was 

named by Clark and Martin (1901) from exposures along 

Piscataway Creek, Prince Georges County, Md. It included seven "zones", which were traceable along the 

Potomac River in the type area of the Aquia. "Zone" 

1 of Clark and Martin (1901) has since been recognized 

as a distinct unit by Bennett and Collins (1952) and 

termed the Brightseat Formation. The present study 

of the lectostratotype section (principal reference section) of the Aquia Formation, the Piscataway Member, 

and the Paspotansa Member (herein designated Locality 3 of this report; see fig. 8) has revealed that the most 

significant lithic change in the formation, from a poorly sorted, clayey sand to a very well sorted, micaceous, 

silty, fine sand, takes place between "zones" 5 and 6 

of Clark and Martin (1901). It is recommended, therefore, that the boundary between the two members be 

placed between those "zones" and that the base of the

Paspotansa be extended downward to include Clark and 

Martin's (1901) zones 6 and 7. Evidence from calcareous 

nannofossils (L.M. Bybell, oral commun., 1984) and 

dinoflagellates (L.E. Edwards, oral commun., 1984) indicates a biostratigraphic break between "zones" 5 and 

6, which is further substantiated by mollusk data. The 

remaining beds assigned to the Piscataway Member 

consist of clayey, silty, poorly sorted, glauconitic sands, 

which contain large numbers of macrofossils, principally 

mollusks (see fig. 9). The mollusks are concentrated in 

beds of varying thicknesses and are cemented at several 

intervals into locally traceable indurated ledges. Large 

bivalves, including Cucullaea, Ostrea, Dosiniopsis, and 

Crassatellites (see pi. 1), are the most conspicuous taxa. 

The quartz sand incorporated into the Piscataway is 

usually poorly sorted, angular, and clear. Glauconite is 

extremely abundant, ranging from sand-size pellets to 

coatings on and in molluscan fossils. The sand, 

glauconite, and mollusks are interspersed in a clayey, 

silty matrix producing a very tough, olive-gray (5 Y 4/1), 

calcareous marl. Glauconite percentages range from a 

low of 20 percent in far updip localities to 70 percent 

or more in the seaward parts of the basin.
10 STRATIGRAPHY AND MOLLUSKS OF PAMUNKEY GROUP AND OLD CHURCH FORMATION

76°

38°

37°

. >---,--» v."\ "fr:»1

FIGURE 6. Map showing the areal extent of the middle early Paleocene depositional basin of the Brightseat Formation in the Salisbury 

Embayment. Dashed line indicates area where boundary data are 

lacking. Map is based on outcrop and core data used in this report 

as well as on subsurface data from Brown and others (1972).

The Piscataway Member unconformably overlies the 

Brightseat in Prince Georges County, Md., and at 

Aquia Creek, Va. (see Hazel, 1969; Bennett and Collins, 

1952). At Aquia Creek (Locality 1), a transgressing 

Aquia sea angularly beveled off the underlying Brightseat beds, resulting in a pronounced unconformity (see 

fig. 10). The micaceous, silty sand of the Brightseat contrasts sharply with the overlying, poorly sorted, 

glauconitic sand of the Piscataway Member. The 

Piscataway Member may be seen along the Potomac 

River in continuous exposures from Aquia Creek to 

Potomac Creek. This is the best series of outcrops of 

Piscataway in either Maryland or Virginia; as much as 

20 feet (6.0 m) of extremely fossiliferous, olive-gray (5 Y 

6/1), glauconitic sand is exposed. Aragonitic forms of 

mollusks are soft but obtainable, and calcitic forms are 

well preserved but often incorporated into indurated 

masses or thin beds. The fine, silty, glauconitic sand of

37" -

FIGURE 7. Map showing the areal extent of the late Paleocene depositional basin of the Aquia Formation in the Salisbury Embayment. Dashed line indicates area where boundary data are lacking. 

Map is based on outcrop and core data used in this report as well 

as on subsurface data from Brown and others (1972).

the Paspotansa apparently disconformably overlies the 

Piscataway. The contact between the Brightseat and 

the Aquia has not been observed along the Rappahannock River in Virginia but is presumed to be similar to 

those contact exposures to the north. The Brightseat 

crops out on the Rappahannock below Fredericksburg, 

1.85 miles (2.98 km) east of Greenfield, Spotsylvania 

County (Locality 2, fig. 5B), and the Piscataway is first 

seen on that river 0.15 mile (0.24 km) below the mouth 

of Snow Creek, Caroline County (Locality 4). The contact between the two units may be presumed to descend 

to water level (sea level) somewhere between the two localities. No outcrops of the Piscataway are known along 

the Mattaponi River, but a core taken by R.B. Mixon 

(USGS, Reston) at Blantons Pond, 0.65 mile (1.05 km) 

southwest of the Rte. 207 bridge over the Mattaponi 

River (Locality 5), showed sediments assigned to the 

Piscataway directly overlying Lower Cretaceous clays.
STRATIGRAPHY 11

77°

xWASHINGTON

\ Anne

Prince \Arunde! 

Georges

FIGURE 8. Map showing localities where the Piscataway Member (revised) of the Aquia Formation 

is exposed or found in cores used in this study. Numbers refer to localities mentioned in the 

text.
12 STRATIGRAPHY AND MOLLUSKS OF PAMUNKEY GROUP AND OLD CHURCH FORMATION

FIGURE 9. Locality 8 on the Pamunkey River, 0.5 mile (0.8 km) east of Wickham 

Crossing, Hanover County, Va. Note the large number of mollusks, which typify 

the Piscataway Member of the Aquia Formation. The pick handle is 25 inches 

(63.5 cm) long.

The Piscataway Member first appears on the 

Pamunkey River about 0.65 mile (1.05 km) below the 

confluence of the North and South Anna Rivers (Locality 6). There it overlies a greenish-blue clay belonging 

to the Lower Cretaceous. The contact between the two 

units is especially conspicuous and is marked by 1.5 feet 

(0.5 m) of cobble- to boulder-sized clasts along the base 

of the Aquia. The Piscataway is extremely weathered 

there, and only calcitic mollusks are preserved. The 

Pamunkey River continues southward, and 0.8 miles 

(1.3 km) downriver from Locality 6, on the right bank,

a similar section is exposed (Locality 7). There the 

Piscataway is relatively fresh and contains a large and 

varied assemblage of preserved mollusks. In spite of the 

apparent excellent preservation in the field, the 

mollusks become crumbly when dried. The calcitic 

forms, however, are well preserved, as is the microfauna. 

The farthest downdip outcrop of the Piscataway 

Member on the Pamunkey is just downstream from 

Wickham Crossing on the right bank (Locality 8, fig. 

11). At this locality 13.5 feet (4.1 m) of fresh, olive-gray 

(5 Y 4/1), very fossiliferous, clayey sand is exposed and
STRATIGRAPHY 13

FIGURE 10. Aquia Creek (looking upstream), above Thorney Point, Stafford County, Va. (Locality 1) showing the contact 

(arrow) between the Brightseat (A) and the Aquia (B) Formations. Nearer the photographer the Brightseat is capped by 

an indurated bed. Upstream that bed has been beveled off by the transgressing Aquia sea.

is underlain by a blue-green clay (presumed to be Lower 

Cretaceous). The Piscataway is overlain by the oliveblack (5 Y 2/1), very well sorted, silty, very fine, 

glauconitic sand of the Paspotansa Member of the 

Aquia. The contact between the two Aquia units at this 

locality seems to be undulant and exhibits as much as 

one foot of relief. The top of the Piscataway descends 

below stream level, and 30 feet (9.1 m) of Paspotansa 

is exposed in a large bluff (Locality 9) 1.1 miles (1.8 km) 

(straightline) downstream from Locality 8. The Aquia 

is not known along the Chickahominy River but was 

reported by Barton (1911) from Shockoe, Gillis, and 

Almond Creeks in Richmond. Strata older than the 

Miocene have been covered by buildings and sewers, but 

detailed descriptions by Darton (1911) and Rogers 

(1861) make certain the presence of both the Piscataway 

and Paspotansa Members of the Aquia Formation in 

Richmond. Reported thicknesses range from 15 to 25 

feet (4.6 to 7.6 m). The only exposure of Piscataway beds 

along the James River found in this study is 1.0 mile 

(1.6 km) above the Turkey Island Cutoff on the right 

bank (Locality 10, fig. 12). There, 2.0 feet (0.6 m) of darkolive-gray (5 Y 4/1), poorly sorted, glauconitic sand

overlies a basal gravel and cobble conglomerate. 

Molluscan fossils are poorly preserved but include 

aragonitic forms (Crassatellites, Turritella) as well as 

calcitic forms (Ostrea). Downriver from this locality the 

top of the Piscataway dips below river level (sea level), 

and the Paspotansa is the only member of the Aquia 

Formation exposed.

Calcareous macrofossils in the Piscataway Member 

are generally poorly preserved and often soft and 

friable. Slow and careful extraction methods, however, 

make it possible to recognize a number of molluscan 

taxa. Calcitic mollusks are generally well preserved, and 

some localities exhibit moderately well preserved 

aragonitic forms. At the lectostratotype locality of the 

Aquia Formation on the Potomac River below Aquia 

Creek (Locality 3), mollusks are present in large 

numbers but are relatively poorly preserved. Preservation is somewhat better along the Rappahannock River 

below Fredericksburg (Locality 4) but is probably best 

in that section of the Pamunkey River above the U.S. 

Rte. 301 bridge (Localities 7, 8). In all these exposures, 

molluscan diversity is relatively low, and a small group 

of taxa forms a relatively large percentage of the
14 STRATIGRAPHY AND MOLLUSKS OF PAMUNKEY GROUP AND OLD CHURCH FORMATION

FIGURE 11. Locality 8 on the Pamunkey River, 0.5 mile (0.8 km) east of Wickham Crossing, Hanover County, Va., showing the Piscataway Member of the Aquia Formation. Cobbles occur along the Lower Cretaceous contact near the 

bottom of the photograph. The Paspotansa Member occurs near the head level of the person at upper right.

fauna. Some of these common taxa include the following (see pi. 1):

Cucullaea gigantea Conrad, 1830 (fig. 7) 

Ostrea alepidota Ball, 1898 (figs. 1, 2, 4, 5) 

Crassatellites capricranium (Rogers, 1839) (fig. 9) 

Lucina aquiana Clark, 1895 

Dosiniopsis lenticularis (Rogers, 1839) (fig. 10) 

Pitar pyga Conrad, 1845 (fig. 8) 

Corbula aldrichi Meyer, 1885 

Turritella mortoni Conrad, 1830 (fig. 6) 

Turritella humerosa Conrad, 1835 (fig. 3) 

Clark (1896b) and Clark and Martin (1901) listed many 

additional species of mollusks found in the Piscataway 

Member. However, lack of abundance or poor preservation, or both conditions, cause these taxa to constitute only a small percentage of the total Piscataway 

assemblage. The relative lack of diversity and the 

absence of known warm-water mollusks suggest 

temperate conditions. Distribution of sediments indicates a basin bordered to the south by the Norfolk 

Arch and to the west by the Piedmont (Brown and 

others, 1972). Access to the paleo-Atlantic was to the 

northeast through Maryland, Delaware, and New

Jersey. This northeastward alignment, with the Norfolk 

Arch acting as a barrier between the Piscataway sea 

and the Beaufort sea in the Albemarle Embayment to 

the south (see fig. 2), probably affected current circulation patterns creating more temperate conditions.

The molluscan taxa found in the Piscataway Member 

indicate a late Paleocene age. A more specific age is difficult to determine on the basis of mollusks, but in Gulf 

Coast stratigraphic terms the unit is clearly a preTuscahoma, post-Porters Creek equivalent. On the basis 

of ostracodes and planktic foraminifers, Hazel (1969) 

placed the Piscataway in the Globorotaliapseudomenardii Subzone of the Globorotalia velascoensis Zone and 

in the upper Landenian Stage. Hazel (oral commun., 

1982) believes the Piscataway to be the equivalent of 

the Coal Bluff Member of the Naheola Formation and 

the lower Nanafalia Formation. Foraminifers listed by 

Brown and others (1977, p. 13) indicate an equivalency 

of the upper beds of the Beaufort Formation in North 

Carolina to the Piscataway. These glauconitic sands, 

which overlie the Jericho Run Member of the Beaufort, 

were assigned to the basal part of the Globorotalia 

pseudomenardii Zone (P4) of Berggren (1972).
STRATIGRAPHY 15

FIGURE 12. Locality 10 on the James River, 1.0 mile (1.6 km) above the mouth of the Turkey Island Cutoff, Chesterfield 

County, Va., showing the basal portion of the Piscataway Member of the Aquia Formation. The pick handle is approximately 36 inches (91.5 cm) long.

PASPOTANSA MEMBER (REVISED)

The Paspotansa Member of the Aquia Formation, 

described by Clark and Martin (1901), received its name 

from Passapatanzy Creek, a tributary of the Potomac 

River in Stafford County, Va. As originally defined, the 

Paspotansa included zones 8 and 9 of Clark and Martin (1901). However, as previously discussed, it is here 

recommended that "zones" 6 and 1 also be included in 

the Paspotansa. "Zone" 6 is an olive-black (5 Y 2/1), very 

fine, micaceous, glauconitic sand containing large 

numbers of Turritella mortoni. "Zones" 1 and 8 consist 

of olive-black (5 Y 2/1), fine, glauconitic sand containing scattered, thin Turritella beds. "Zone" 9 is an oliveblack (5 Y 2/1), fine, glauconitic sand containing large 

numbers of closely packed Turritellas in beds of varying thickness (see figs. 13, 14). The thickness of the 

units, as well as their fossil content, varies from locality to locality, but several characteristics are internally 

consistent. The Paspotansa consists of fine to very fine, 

silty, well-sorted, micaceous, glauconitic and quartzose 

sand, which appears as massive or very thick beds. This 

texture is strikingly different from the underlying

poorly sorted, clayey, shelly, glauconitic and quartzose 

sands of the Piscataway Member. Further, the Paspotansa is usually overlain by a gray (N 1, when fresh), 

tough clay termed the Marlboro Clay (see fig. 15). This 

bed, when present, makes the recognition of the upper 

boundary of the Paspotansa relatively easy. Where the 

Marlboro is absent, the well-sorted, fine sands of the 

Paspotansa may be distinguished from the overlying 

clayey, highly bioturbated, poorly sorted glauconitic 

sands of the Potapaco Member of the Nanjemoy Formation. As in all the formations in the Pamunkey 

Group, the glauconite content of the Paspotansa varies 

with proximity to the paleoshoreline. Percentages are 

much lower near the perimeter of the basin and in some 

areas are as low as 20 percent. Seaward, in an eastward 

direction, the glauconite content may reach 90 percent. 

The nature of the shell deposits within the Paspotansa 

further serves to distinguish that unit from the underlying Piscataway and overlying Nanjemoy. Massive 

glauconitic sands, containing many large Turritella in 

thin beds or lenses, characterize the Paspotansa, in 

striking contrast to the very shelly, silty sands of the 

Piscataway, which are usually dominated by closely
16 STRATIGRAPHY AND MOLLUSKS OF PAMUNKEY GROUP AND OLD CHURCH FORMATION

77° 76°

FIGURE 13. Map showing localities where the Paspotansa Member (revised) of the Aquia Formation is exposed or found in cores used in this study. Numbers refer to localities mentioned in the 

text.
STRATIGRAPHY 17

packed, medium-sized to large bivalves. Also notable 

is the massive nature of the Paspotansa, often exposed 

in the high vertical walls of bluffs along the Potomac, 

Rappahannock, and Pamunkey Rivers. Where very 

fresh the unit is dark olive black (5 Y 2/1). Where partially weathered it is grayish orange (10 YR 7/4), and 

where very weathered it appears yellowish orange 

(10 YR 7/6) owing to the oxidation of iron in the 

glauconite.

The Paspotansa apparently disconformably overlies 

the Piscataway, but the contact is commonly obscured. 

Clark and Martin (1901) described the contact between 

"zones" 6 and 7 along the bluffs below Aquia Creek, 

but, as previously discussed, the most notable lithic 

change occurs at the contact between their zones 5 and 

6. On the Rappahannock and Mattaponi Rivers, the contact between the two members is obscured by slumping and poor outcrops. On the Pamunkey River, 

however, the contact between the two members is sharp 

and undulating. No phosphate accumulations or burrows are present, indicating, at most, only a brief period 

of nondeposition. The contact is not exposed on the 

Chickahominy and James Rivers, but the distinct textural makeup of the Piscataway and Paspotansa, as well 

as their unique macrofaunal assemblages, enable the 

field geologist to differentiate them readily.

The Paspotansa is overlain over much of its area! extent by the Marlboro Clay. The contact between the two 

units is abrupt, and there is little or no mixing of their 

sediments. Some burrows extend down into the underlying Paspotansa and are filled with Marlboro sediment, 

a tough, light-gray (N 7) clay (pink 10 R 7/4, when 

weathered) with small admixtures of sand and gravel. 

In some areas where the Marlboro Clay is absent, beds 

of the Nanjemoy Formation (Potapaco Member) directly 

overlie the Paspotansa.

The Paspotansa sea, like that of the preceding 

Piscataway, was embayed from the northeast; the stillpositive Norfolk Arch separated the basin from the 

Paleocene embayment in North Carolina.

The Paspotansa Member crops out in a broad arc 

from the Eastern Shore of Maryland to the James River 

in Virginia (see figs. 7, 13). Clark and Martin (1901, 

p. 73) described the Paspotansa from the Chester River 

in Kent County, Md., and their descriptions of the sections on the Severn and South Rivers in Anne Arundel 

County, Md., indicate the presence of the unit there. Additional sections are given for the Upper Marlboro area 

of Prince Georges County, Md., where the Paspotansa 

includes a heavy concentration of bryozoans. The most 

extensive outcrops of the member extend along the 

Virginia shore of the Potomac River from the mouth 

of Aquia Creek to near Fairview Beach. Between 

Potomac Creek and Aquia Creek (Locality 3), 61.5 feet

(18.8 m) of the Paspotansa crops out in steep, almost 

vertical bluffs, which have been weathered to a reddishorange color (fig. 16). This section is here designated the 

principal reference section (lectostratotype locality) of 

the Paspotansa. Several distinct shell beds are present, 

as well as several ledges of somewhat discontinuous 

boulder-sized concretions. Other shells, principally 

large, current-oriented Turritella mortoni, are concentrated in lens-shaped masses. Below the mouth of 

Potomac Creek (Locality 11), the Paspotansa descends 

to near water level, is considerably fresher, and consists 

of olive-black (5 Y 2/1), glauconitic, shelly sand. 

Mollusks are abundant and well preserved; Turritella 

mortoni, Ostrea sinuosa, Crassatellites alaeformis, and 

Cucullaea gigantea are the dominant taxa (see pi. 2). The 

last unweathered outcrop of the Paspotansa on the 

Potomac occurs just below the mouth of Passapatanzy Creek (Locality 12). The next exposure of Paleogene 

beds is at a bluff 1.75 miles (2.8 km) below the large 

wharf at Fairview Beach where the Aquia, Marlboro, 

and Nanjemoy crop out (Locality 13, fig. 15).

On the Rappahannock River, the Paspotansa makes 

its first appearance 1.0 mile (1.6 km) upriver from the 

mouth of Ware Creek on the left bank, King George 

County, Va. (Locality 14). There 10.0 feet (3.0 m) of 

glauconitic, micaceous, shelly sand is exposed, 7.0 feet 

(2.1 m) of which is fresh. Mollusks are present and 

preserved; Turritella mortoni is abundant, and Ostrea 

sinuosa is common. Downriver of this locality the 

Paspotansa crops out intermittently near water level. 

At the large bluff on the right bank of the Rappahannock 0.4 mile (0.6 km) below the mouth of Ware Creek 

(Locality 15), 4 feet (1.2 m) is exposed, but slumping 

obscures its contact with the overlying units. Small exposures of the Paspotansa are present above and below 

the mouth of Lambs Creek on the left bank (Localities 

16,17), above Hopyard Landing (Locality 18), and below 

Jones Top Creek (Locality 19).

Outcrops of the Paspotansa are relatively scarce in 

the Mattaponi River valley, a condition due principally to the low stream gradient. In Caroline County, Va., 

several boreholes drilled by R.B. Mixon (USGS) (some 

with the help of the author) have penetrated sediments 

assignable to that unit. A core taken at Blantons Pond 

south of Bowling Green (Locality 5) contained 58 feet 

(17.7 m) of Aquia, the upper two-thirds of which is considered to be Paspotansa. Farther to the west, 1.0 mile 

(1.6 km) northwest of Wrights Corner, where Rte. 634 

crosses Hobby Swamp (Locality 20), a core to basement 

revealed 27.0 feet (8.2 m) of Aquia directly overlying 

Piedmont rocks. The Aquia, in turn, was directly 

overlain by the Calvert, the Nanjemoy having apparently been beveled off. Another core, taken at Smoots Pond 

on the Camp A.P. Hill Military Base (Locality 21),
18 STRATIGRAPHY AND MOLLUSKS OF PAMUNKEY GROUP AND OLD CHURCH FORMATION

r\_; '*r^* - >i-«^ -fc ' ^ >'- -- **&&''* &<??** S«r t^ ^ *"* * -* *.<'zF*f *f" '-W *t

*

r^ IT ^Li *_ -**' v, » '*

FIGURE 14. Paspotansa Member of the Aquia Formation as exposed along the Potomac River near Potomac Creek. A, Bull 

Bluff, right bank of the Potomac River at the mouth of Potomac Creek, King George County, Va. (Locality 11). Exposed 

are numerous thin beds made up almost entirely of large Turritella. This taxon is also abundant in the indurated blocks 

in the upper half of the photograph. B, Potomac River, 0.1 mile (0.16 km) below the mouth of Passapatanzy Creek, King 

George County, Va. (Locality 12). Large indurated blocks, like those seen in figure I4A, litter the shore here and contain 

large numbers of silicified Turritella. The pick handle is 25 inches (63.5 cm) long.

contained 57 feet (17.4 m) of Aquia, at least half of which 

is Paspotansa. The only known outcrops of the Aquia 

on the Mattaponi River occur between the Richmond, 

Fredericksburg, and Potomac Railroad bridge and the 

Rte. 301 bridge. Exposed are beds assignable to the 

Paspotansa Member. Clark and Miller (1912) and 

Gildersleeve (1942) reported Aquia beds in the vicinity 

of the railroad bridge. This locality was not accessible 

during this study, but the description and faunal lists 

of those authors suggest that the exposed beds are 

Paspotansa. Clark and Miller (1912) and Gildersleeve 

(1942) both described a section on the Mattaponi River, 

just upstream from the Rte. 301 bridge. This locality 

(Locality 22) is still accessible; the exposure consists of 

3 to 6 feet (0.9 to 1.8 m) of fine, silty, glauconitic sand 

containing numerous poorly preserved Turritella mortoni. The lithology and faunal assemblage are typical 

of the Paspotansa Member. At the next bridge downstream (Rte. 654), in a small ravine, basal Potapaco 

(Nanjemoy Formation) is exposed (Locality 23).

The Paspotansa Member is better exposed along the 

Pamunkey River: outcrops occur from below Wickham

Crossing (Locality 8) to 0.65 mile (1.05 km) below 

Sturgeon Hole (Locality 24). Most of the calcareous 

material has been leached from the upriver exposures, 

but molluscan molds and casts are common. The Paspotansa makes its farthest updip appearance 0.5 mile 

(0.8 km) east of Wickham Crossing (Locality 8) (fig. 11) 

where it overlies the Piscataway Member. The oliveblack (5 Y 2/1), very fine, silty, micaceous, relatively unfossiliferous, very well sorted glauconitic sands of the 

Paspotansa may be readily distinguished from the poorly sorted, clayey, very fossiliferous, glauconitic sands 

of the Piscataway. Downstream, 1.6 miles (2.6 km) east 

of Wickham Crossing (Locality 9), 30 feet (9.1 m) of 

Paspotansa are exposed. There, molds of Turritella mortoni are scattered throughout the unit but are concentrated in thin beds in the upper 10 feet (3.0 m). 

Unweathered Paspotansa, containing preserved 

mollusks, crops out 0.25 mile (0.40 km) below the Rte. 

301 bridge (Littlepage Bridge) (Locality 25), at Sturgeon 

Hole (Locality 26), and 0.65 mile (1.05 km) below 

Sturgeon Hole (Locality 24). At Locality 24 the Paspotansa is unconformably overlain by the Marlboro Clay.
STRATIGRAPHY 19

FIGURE 14. Continued.

As previously mentioned, the description by Rogers 

(1861) and Darton (1911) of the glauconitic sand occurring in Richmond indicates the presence of the Paspotansa there, but these exposures have since been covered. Along the James River, however, the Paspotansa 

crops out along the left bank 1.1 miles (1.8 km) above 

Shirley Plantation (Locality 27). Another, smaller exposure may be seen at City Point, near the mouth of 

the Appomattox River in Hopewell (Locality 28). The 

farthest downriver exposure of the Paspotansa on the 

James occurs on the right bank just below the mouth 

of Bailey Creek (Locality 29), where this unit is overlain 

by as much as 10 feet (3.0 m) of Marlboro Clay. Turritella mortoni and Ostrea sinuosa are both common in 

the Paspotansa at that outcrop, and it is probably the 

topotype locality for the latter taxon (Rogers and 

Rogers, 1835).

The Paspotansa contains large numbers of 

macrofossils, principally mollusks (fig. 17). The shells 

are often concentrated in thin or lens-shaped beds. At 

many localities where the outcrop has dried out, the 

mollusks are very soft or entirely dissolved, and only 

molds or casts remain. Localities with the best fossil 

preservation include those on the Potomac River below 

Aquia Creek (Locality 3) and below Potomac Creek near 

Belvedere Beach (Localities 12, 30). Preservation is good

at some localities along the Rappahannock River 

(Localities 14, 15), but it is poor on the Mattaponi River 

above the Rte. 301 bridge (Locality 22) and below the 

mouth of Baileys Creek on the James River (Locality 

29). Preservation of macrofossils at the Pamunkey 

River localities is poor above the Rte. 301 bridge and 

consists mainly of molds and casts. Molds of large taxa 

such as Turritella mortoni, Ostrea sinuosa, and 

Crassatellites alaeformis are easily recognized even 

when preservation is poor. At the localities below the 

Rte. 301 bridge (Localities 24, 25, 26), preservation is 

fair to good. Although many species of mollusks were 

listed by Clark (1896b) and Clark and Martin (1901) as 

occurring in the Paspotansa Member, the most common 

taxa are the following (see pi. 2):

Cucullaea gigantea Conrad, 1830 (fig. 1) 

Pycnodonte sp. (fig. 2)

Ostrea sinuosa Rogers and Rogers, 1837 (fig. 4, 8) 

Crassatellites alaeformis Conrad, 1830 (fig. 7) 

Venericardia regia Conrad, 1865 (fig. 5) 

Pitar pyga Conrad, 1845 (fig. 9) 

Turritella humerosa Conrad, 1835 (fig. 10) 

Turritella mortoni Conrad, 1830 (fig. 3, 6) 

Lunatia marylandica Conrad, 1865 

Generally poor preservation of mollusks may account 

for the apparent low diversity. Some localities, such as
20 STRATIGRAPHY AND MOLLUSKS OF PAMUNKEY GROUP AND OLD CHURCH FORMATION

FIGURE 15. Potomac River, 1.75 miles (2.8 km) below the large wharf at Fairview Beach, King George County, Va. (Locality 13). Lower arrow and Lynn Strickland's foot are on the contact between the Paspotansa Member of the Aquia Formation (A) and the Marlboro Clay (B); upper arrow and her pick point are at the contact between the Marlboro Clay 

(B) and the Nanjemoy Formation (Potapaco Member) (C).

the small bluff on the Potomac River just below the 

mouth of Passapatanzy Creek (Locality 12), where the 

sediment is fresh, contain a number of well-preserved, 

small mollusks, but they make up a small percentage 

of the total assemblage. Paspotansa molluscan faunas 

are dominated principally by the large gastropod Turritella mortoni. Forms closely related or identical to that 

taxon have been found in upper Paleocene deposits in 

South Carolina at Wilsons Landing on the Santee River. 

Turritella praecincta occurs with T. mortoni at Wilsons 

Landing and has been reported from the Tuscahoma 

Formation of Georgia by Gibson (1980). Both forms 

occur in Alabama and range from the Nanafalia Formation to the Bells Landing Marl Member of the Tuscahoma Formation. T. humerosa, another common taxon 

in the Paspotansa, is also found in the Nanafalia and 

Tuscahoma Formations. Ostrea sinuosa, a less abundant but very conspicuous form, is also commonly 

found in upper Paleocene beds in South Carolina, 

Georgia, and Alabama.

Gibson and others (1980) identified the Paspotansa 

Member in a core taken in Westmoreland County, Va.,

and placed the entire member in calcareous nannoplankton zone NP 9. L.M. Bybell (oral commun., 1984) concurs with this assignment.

MARLBORO CLAY

Clark and Martin (1901, p. 65) first applied the term 

"Marlboro clay" to sediments included in "zone" 10 of 

Clark (1896b, p. 42). The name was derived from exposures of that unit near Upper Marlboro, Prince 

Georges County, Md. Clark and Martin (1901) considered this unit to be the basal unit of the Potapaco 

Member of the Nanjemoy Formation. Clark and Miller 

(1906) briefly described the outcrop area of the 

"Marlboro clay" across Maryland and Virginia and included it in the basal bed of the Nanjemoy Formation. 

Clark and Miller (1912) again included the pink clay in 

the basal bed of the Nanjemoy. However, at only one 

locality, below Hopewell on the James River (Clark and 

Miller, 1912, p. 115), did those authors give a specific 

section where this unit crops out. Barton (1948), in a
STRATIGRAPHY 21

FIGURE 16. Potomac River, 1.5 miles (2.4 km) below the mouth of Aquia Creek, Stafford County, Va. (Locality 3). Principal reference section and lectostratotype locality of the Aquia Formation and its Piscataway and Paspotansa Members. 

The Piscataway Member (as herein amended) includes the beds from beach level up to and including the prominent indurated ledge. For scale, the top of the indurated ledge is approximately 14.0 feet (4.3 m) above water level. The 

Paspotansa occupies the remainder of the exposure.

short note, described the areal extent of the Marlboro 

Clay and referred to that unit as the basal member of 

the Nanjemoy Formation. This had the effect of formalizing the name. A more detailed study, including a 

detailed geologic map by Barton (1951), continued the 

placement of the Marlboro as the basal bed of the Nanjemoy. Well studies in Virginia by Cederstrom (1957) 

showed the persistence and mappability of the unit in 

the subsurface in that area. Glaser (1971), however, was 

the first to formally propose the elevation of the 

Marlboro Clay to formational rank. This restricted the 

original concept of the Nanjemoy Formation and, more 

specifically, of the Potapaco Member. This treatment 

of the Marlboro as a separate formation was continued 

by Reinhardt and others (1980). Glaser (1971, p. 14), in 

a rather complete description of the unit, characterized 

it as "a silvery-gray to pale-red plastic clay interbedded 

with much subordinate yellowish-gray to reddish silt." 

Observing the silty, somewhat ripple-marked texture 

of the Marlboro and the restricted fauna from the unit 

reported by Nogan (1964), Glaser (1971) concluded that

the evidence suggests very shallow, possibly tidal-flat, 

depositional conditions. Glaser pointed out that both 

the lower and upper contacts of the Marlboro were 

sharp and nongradational and probably represented at 

least a brief hiatus between the underlying and overlying units. A more recent study by Reinhardt and others 

(1980) on a core in Westmoreland County, Va., conluded 

that the Aquia-Marlboro contact was somewhat gradational whereas the upper Marlboro-Nanjemoy contact 

was sharp and was marked by burrows into the underlying Marlboro. In the present study, Marlboro outcrop 

and well information is scanty (fig. 18). Where the unit 

was observed, both the upper and lower contacts were 

abrupt and burrowed, which indicates periods of 

nondeposition or unconformities.

The areal distribution of the Marlboro was mapped 

by Barton (1951) and was schematically shown by 

Glaser (1971), but no detailed study of the formation 

has been made in much of the Virginia Coastal Plain 

(see fig. 19). Outcrops of the Marlboro examined in this 

study have been limited to the Potomac, Mattaponi,
22 STRATIGRAPHY AND MOLLUSKS OF PAMUNKEY GROUP AND OLD CHURCH FORMATION

FIGURE 17. Pamunkey River at Sturgeon Hole, 0.75 mile (1.21 km) below the Rte. 301 bridge (Littlepage Bridge), Caroline 

County, Va. (Locality 26). Numerous thin bands of Turritetta are present, as is common in the upper part of the Paspotansa Member of the Aquia Formation.

Pamunkey, and James Rivers. Several additional data 

points were observed in cores taken by R.B. Mixon 

(while assisted by me) in Caroline County, Va. Preliminary results indicate a spotty, though widespread, 

occurrence of the unit. In some places the Nanjemoy 

directly overlies the Aquia. In others, the Marlboro 

separates the two. Depositional trends indicated by 

these presences or absences of the Marlboro are not yet 

clear but may reflect thinning or erosion across an intermittently structurally active area. Thinning of this 

type has been described by Mixon and Newell (1977) 

where it has affected the Aquia Formation in the Fredericksburg area of northern Virginia. Further drilling 

may make clear any such depositional or erosional 

trends. Knowledge of the presence of the Paspotansa 

Member of the Aquia and the overlying Potapaco Member of the Nanjemoy may help bracket the area in which 

the Marlboro is present, even without the benefit of exposures. Along the Potomac River, very thin discontinuous remnants of the Marlboro Clay are present at 

the lectostratotype section of the Aquia (Locality 3) and 

Bull Bluff (Locality 11). On the right bank of the Potomac River 1.75 miles (2.5 km) below Fairview Beach

(Locality 13, fig. 15), the Marlboro may be seen to 

overlie several feet of weathered Paspotansa and is in 

turn overlain by the Potapaco Member of the Nanjemoy 

Formation. Barton's (1951) map of northern Virginia 

and part of southern Maryland indicates that the 

Marlboro is present in that area. On the Rappahannock 

River, the last exposure of Aquia occurs below Hopyard 

Landing (Locality 18), and the Nanjemoy crops out at 

water level a short distance downriver (Locality 31). The 

bluffs between the two localities are slumped and 

covered by vegetation, but it may be inferred that the 

Marlboro dips to water level (sea level) somewhere in 

that interval. Barton (1951) mapped the Marlboro in 

that area. Outcrop and well data concerning the 

distribution of the Marlboro Clay south of the Rappahannock River are scarce. Clark and Miller (1912) 

listed only the outcrop on the right bank of the James 

River below the mouth of Baileys Creek (Locality 29) 

as exposing the Marlboro, while Gildersleeve (1942, 

p. 15) mentioned that he nowhere observed the unit in 

his study area. Subsurface work by Cederstrom (1945, 

1957) indicated the presence of the Marlboro in many 

water wells in southeastern Virginia, although the clay
STRATIGRAPHY 23

WASHINGTON 

\

/ xv/

King George

_ f \ <j* ^r>

Hanover l^»Hf f ^ 

Vy,

O^wFIGURE 18. Map showing localities where the Marlboro Clay is exposed or found in cores used in 

this study. Numbers refer to localities mentioned in the text.
24

37° -

STRATIGRAPHY AND MOLLUSKS OF PAMUNKEY GROUP AND OLD CHURCH FORMATION

the Potapaco. This contact is not as obvious, but the 

fine, well-sorted, glauconitic sands of the Paspotansa 

may be distinguished from the clayey, poorly sorted 

sands of the Potapaco.

On the Pamunkey River, the Marlboro Clay was 

observed at only two localities. At a large bluff 0.95 mile 

(1.53 km) above the Rte. 301 bridge over the Pamunkey 

(Locality 33), 1.5 feet (0.4 m) of weathered gray clay 

belonging to the Marlboro overlies at least 10.0 feet (6.1 

m) of fine, micaceous, glauconitic sand of the Paspotansa. The Marlboro is in turn overlain by a weathered, 

poorly sorted, brown, micaceous, clayey sand, which 

contains a dinoflagellate flora found at other localities 

in the lowermost bed (Bed A) of the Potapaco Member 

of the Nanjemoy Formation. Both the upper and lower 

contacts are sharp and are marked by burrows. The 

Marlboro contains small amounts of sand, probably as 

a result of burrowing from above. The other exposure 

of the Marlboro on the Pamunkey River occurs 0.65 mile 

(1.05 km) below Sturgeon Hole (Locality 24, fig. 21). 

There the Marlboro unconformably overlies the Paspotansa and is unconformably overlain by the Nanjemoy 

(Bed A of the Potapaco Member). Downriver of this section, it may be inferred by the last outcrop of the Aquia 

and Marlboro and downdip exposures of the lower Nanjemoy that the Marlboro approaches river level approximately 2 miles (3.2 km) east of the Littlepage Bridge 

(Rte. 301). A water well described by Cederstrom (1957, 

p. 87) northeast of Mechanicsville, Hanover County, 

contained 10.0 feet (3.0 m) of pink mud at the base of 

the Nanjemoy, which was probably the Marlboro. It occurred at the interval between 5 and 15 feet (1.5 and 

4.6 m) below sea level. Records of wells closer to the 

Pamunkey are absent. However, the distinctive nature 

of the Marlboro Clay makes it easily recognizable in 

many of the wells described by Cederstrom (1957) in 

Hanover, King William, and New Kent Counties.

The sole known occurrence of the Marlboro Clay on 

the James River was first reported by Clark and Miller 

(1912, p. 115) (Locality 29). At that locality the unit is 

still exposed; it overlies 17.5 feet (5.3 m) of somewhat 

weathered, fine, glauconitic sand of the Paspotansa that 

contains Tunitella mortoni. The Marlboro consists of 

light-gray to pink clay and contains a few molds of small 

indeterminate gastropods, the only known fossil occurrence in the Marlboro. The Marlboro Clay's lower contact with the Aquia is sharp and bioturbated; its upper 

contact is obscured by slumped sediments from beds 

of the Eastover and Yorktown Formations.

Because of the lack of calcareous fossils, the age of 

the Marlboro Clay has been based principally on the fact 

that it occurs between the Aquia and Nanjemoy Formations. This effectively brackets its age but does not 

afford primary evidence. A detailed study of a core from

FIGURE 19. Map showing the areal extent of the late Paleocene 

depositional basin of the Marlboro Clay in the Salisbury Embayment. Dashed line indicates area where boundary data are lacking. 

Map is based on outcrop and core data used in this report as well 

as on subsurface data from Brown and others (1972).

unit was never identified as such. The Marlboro Clay 

crops out on the right bank of the Mattaponi River, just 

below the Rte. 207 bridge in Caroline County (Locality 

32, fig. 20). There the unit consists of light-gray (N 7) 

clay containing scattered sand and pebbles. Burrows 

extend down into the Marlboro from the glauconitic, 

sandy Potapaco Member of the Nanjemoy Formation 

and are filled with sediment from that unit, in sharp contrast to the gray clay below. The contact with the 

underlying Aquia is not exposed there, but the two 

units are present in a core to the west at Blantons Pond 

(Locality 5). In that core 7.0 feet (2.1 m) of Marlboro 

Clay are present in the subsurface. The lower contact 

with the Aquia and the upper contact with the Nanjemoy are sharp and suggest at least brief diastems. To 

the east, at Smoots Pond, in Camp A.P. Hill in Caroline 

County (Locality 21), a core revealed the absence of the 

Marlboro, and the Paspotansa was directly overlain by
STRATIGRAPHY 25

FIGURE 20. Mattaponi River, just below the Rte. 207 bridge, Caroline County, Va. (Locality 32). Pick is at the contact of 

the Marlboro Clay and the Nanjemoy Formation. The Nanjemoy unit is Bed A of the Potapaco Member.

Oak Grove, Westmoreland County, Va., by Gibson and 

others (1980) and Frederiksen (1979) afforded the best 

paleontologic evidence of its age. The consensus of pollen and dinoflagellate data suggested a very late Paleocene or a very early Eocene age assignment. Mixing of 

the two floral assemblages may have been accomplished 

through reworking and bioturbation, or the unit may 

indeed straddle the Paleocene-Eocene boundary. N.O. 

Frederiksen (oral commun., 1984) found Eocene pollen 

only in the upper part of the Marlboro, where it may 

have been reworked downward by burrowing organisms. The Marlboro will be treated by the author in this 

work as an upper Paleocene unit until primary evidence 

suggests a younger age assignment. Nogan (1964) reported the presence of arenaceous foraminifers in the 

lower part of the Marlboro and suggested this as 

evidence of brackish-water conditions. Dinoflagellate 

assemblages are relatively low in diversity and contain 

several brackish-water forms, which suggest a shallow, 

estuarine environment (Gibson and others, 1980, p. 24).

NANJEMOY FORMATION

Beds now included in the Nanjemoy Formation were 

first studied in detail by Clark (1896b), who divided

them, along with those now included in the Aquia Formation, into "zones." Those "zones" above the Aquia 

Creek Stage of Clark (1896b) were numbered 10 through 

17. "Zone" 17 was defined as the Woodstock Stage. 

Clark and Martin (1901) revised this terminology and 

placed their zones 10 through 17 in the "Nanjemoy Formation or Stage." The Nanjemoy was divided into the 

"Potapaco member or substage," including "zones" 10 

through 15, and the "Woodstock member or substage," 

including "zones" 16 through 17. In this same publication Clark and Martin (1901, p. 65) introduced the term 

"Marlboro clay," informally, for part of their zone 10. In 

a brief, preliminary report on the stratigraphy of the Virginia Coastal Plain, Clark and Miller (1906) dropped the 

stage and substage terminology and referred only to the 

Aquia and Nanjemoy Formations. Clark and Miller (1912) 

continued this usage and retained both in formational 

status. Again, the "Marlboro clay" was briefly mentioned 

(Clark and Miller, 1912, p. 103) but was specifically 

reported from only one locality (Clark and Miller, 1912, 

p. 115). The zonation of beds and their breakdown into 

members was retained only for those well-studied exposures along the Potomac River. South of the Potomac 

only assignment to formation was attempted.
26 STRATIGRAPHY AND MOLLUSKS OF PAMUNKEY GROUP AND OLD CHURCH FORMATION

FIGURE 21. Pamunkey River, 0.65 mile (1.05 km) below Sturgeon Hole, Caroline County, Va. (Locality 24). Exposed is the 

Paspotansa Member of the Aquia Formation (A), the Marlboro Clay (B), and the Potapaco Member (Bed A) of the Nanjemoy 

Formation (C).

The term "Marlboro Clay" was finally formalized by 

Barton (1948), but he retained the unit as a basal 

member of the Nanjemoy. This removed the Marlboro 

("zone" 10, in part, of Clark) from beds previously included in the Potapaco Member. The Marlboro was retained as a member of the Nanjemoy until Glaser (1971) 

elevated it to formational rank. This, in effect, restricted 

the original concept of the Nanjemoy, and only part of 

"zone" 10 and "zones" 11-17 remained in that formation. Younger beds, not included in the original description or sections of the Nanjemoy, were later lumped 

under the term "Nanjemoy Formation" by Clark and 

Miller (1912). Included were beds of middle Eocene and 

late Oligocene or early Miocene age along the Pamunkey 

and James Rivers. Later, work by Gildersleeve (1942) 

continued this practice. Otton (1955) described "alight 

gray to yellowish glauconitic sand and interbedded 

rock" in a well near Piney Point in St. Marys County, 

Md. He termed this unit the Piney Point Formation and 

believed it to be of late Eocene age, on the basis of 

foraminifers found in wells on the Eastern Shore of 

Maryland. Later, work by Brown and others (1972)

established the age of the Piney Point as middle Eocene 

(Claibornian). Because of their age equivalency and 

because of their similar lithic composition and texture, 

I believe that the middle Eocene beds along the 

Pamunkey and James Rivers should be included in the 

Piney Point. The beds there represent the only known 

outcrops of that unit. Along the Pamunkey, the Piney 

Point is overlain by a grayish-olive (10 Y 4/2), sandy 

unit herein named the Old Church Formation (late 

Oligocene and early Miocene). Sharp contacts mark the 

unconformity. The Old Church is devoid of glauconite 

except small amounts reworked from the Piney Point. 

Because beds included in the Piney Point and Old 

Church were not included in the original description of 

the Nanjemoy, are not present at the "type area" of the 

Nanjemoy, and are lithologically distinct from the unit, 

it seems appropriate to treat them as separate units of 

formational status. This effectively restricts the Nanjemoy to those beds originally included in the Potapaco 

and Woodstock Members, less the Marlboro Clay. For 

the distribution of sediments assigned to the Nanjemoy, 

see figure 22.
STRATIGRAPHY 27

77

. _

rc NORTH CAROLINA; VC"~ NORTH" CAROLINA--,

'erriK %

37" -

FIGURE 22. Maps showing area! extent of the members of the lower Eocene Nanjemoy Formation. Maps based on outcrop and core data 

used in this report as well as on subsurface data from Brown and others (1972). A, Map showing area! extent of the early Eocene depositional basin of the Potapaco Member of the Nanjemoy Formation in the Salisbury Embayment. Dashed line indicates where boundary 

data are lacking. B, Map showing areal extent of the early Eocene depositional basin of the Woodstock Member of the Nanjemoy 

Formation in the Salisbury Embayment. Dashed line indicates where boundary data are lacking.

POTAPACO MEMBER

The Potapaco Member of the Nanjemoy Formation 

was described by Clark and Martin (1901, p. 65) and 

received its name from "the word Potapaco found on 

the (Captn. John) Smith and others early maps***." 

The Potapaco included Clark and Martin's (1901) 

"zones" 10-15. Part of their "zone" 10 included the 

Marlboro Clay. This unit was later termed the Marlboro 

Clay Member (Darton, 1948) and eventually was 

elevated to formational rank by Glaser (1971). Clark 

(1896b), Clark and Martin (1901), and Clark and Miller 

(1912) described the beds ("zones") found in the 

Potapaco at sections above Popes Creek on the left bank 

of the Potomac River, Charles County, Md. The section 

described by Clark and Martin (1901, p. 70, Section 

VIII) is herein designated the principal reference section 

(lectostratotype) of the Nanjemoy Formation and the 

Potapaco Member. The exposure is just downstream of

Locality 34 in this report. No attempt was made by 

Clark and Martin to trace the "zones" to the north or 

south of the Potomac River; indeed, not even the 

members were recognized away from the Potomac sections. Recent work, principally on the Pamunkey River, 

but with supplemental sections on the James, Mattaponi, Rappahannock, and Patuxent Rivers (see fig. 

23), has enabled me to identify a consistent and readily 

recognizable stratigraphic sequence of beds in the 

Potapaco. Vague descriptions of the "zones" by Clark 

(1896b) has made the correlation of his beds with the 

present scheme, in many cases, a matter of guesswork. 

For that reason, the following terminology is used for 

the series of four beds that have been recognized in the 

Potapaco (lettered from bottom to top):

Bed D concretion-bed Potapaco,

Bed C burrowed Potapaco,

Bed B bedded Potapaco,

Bed A nonbedded Potapaco.
28 STRATIGRAPHY AND MOLLUSKS OF PAMUNKEY GROUP AND OLD CHURCH FORMATION

77° 76°

FIGURE 23. Map showing localities where the Potapaco Member of the Nanjemoy Formation is exposed or found in cores used in this study. Numbers refer to localities mentioned in the text.
STRATIGRAPHY 29

The most striking characteristic of the Potapaco 

Member is its clayey texture. In all four beds, the dominant lithology is a gray to pink clay, studded with varying amounts of fine-sand-sized grains of glauconite. This 

characteristic texture serves to distinguish the 

Potapaco from the silty, fine, glauconitic sand of the 

overlying Woodstock Member and from the underlying 

silty, fine, glauconitic sand of the Paspotansa Member 

of the Aquia Formation (when the Marlboro Clay is not 

present). The clayey nature of the Potapaco was first 

described by Clark (1896b), Clark and Martin (1901), and 

Clark and Miller (1912). Later work by Glaser (1971) and 

Reinhardt and others (1980) alluded to the very clayey 

texture of the lower Nanjemoy.

Another distinguishing characteristic of the Potapaco 

is the relative lack of diversity in the molluscan 

assemblages. A single, small bivalve, Venericardia 

potapacoensis Clark and Martin, 1901, dominates, occurring in relatively thin, very crowded beds. This 

faunal assemblage enables the ready distinction of the 

Potapaco from the TwrateWa-packed sands of the 

underlying Paspotansa Member of the Aquia Formation. Faunally, the overlying Woodstock Member may 

be distinguished by the relative increase in molluscan 

diversity and the occurrence of common to abundant 

large bivalves, Venericardia ascia Rogers and Rogers, 

1839. Mollusks in the Woodstock are scattered 

throughout the unit and only locally are concentrated 

in thin bands as in the Potapaco.

Of the four beds recognized in the Potapaco, Beds B 

and C seem to grade into each other with no discernible, continuous, or mappable contacts. It is believed, 

therefore, that they represent nearly continuous deposition with, perhaps, several marine pulses involving a 

deepening or shallowing of the sea, which caused the 

lithic or environmental changes. Beds A and D, 

however, seem to represent separate marine pulses and 

have sharp contacts marking their lower and upper 

boundaries. In spite of the physical evidence for a 

stratigraphic break between Beds C and D and between 

Bed D and the Woodstock Member, the floras and 

faunas present in the units indicate, at the most, breaks 

of only short duration and the deposition of both the 

Potapaco and Woodstock during the early Eocene.

BED A NONBEDDED POTAPACO

Bed A is found on the Pamunkey, Potomac, Rappahannock, and Mattaponi Rivers. It consists of a 

clayey, silty, fine sand containing scattered, small 

mollusks including Venericardia potapacoensis Clark 

and Martin, 1901. Glauconite occurs in relatively small 

amounts in the sand-sized fraction in updip areas, but 

glauconite percentages increase in a seaward direction.

Small phosphate pebbles are common. The bed is estimated to be 15 to 20 feet (4.6 to 6.1 m) thick and in most 

instances unconformably overlies the Marlboro Clay. 

Bed A is distinguishable from Bed B because of its 

darker color, lack of bedding, and less clayey texture. 

Calcareous fossils are generally leached, leaving only 

molds and casts; however, preserved mollusks are present opposite Goat Island, on the right bank of the Rappahannock River 2.5 miles (4.0 km) above Port Royal, 

Caroline County, Va. (Locality 31), where Bed A 

descends to sea level. The unit also occurs high in the 

bluff just below the mouth of Ware Creek on the right 

bank of the Rappahannock in Caroline County (Locality 35). The unit is present on the right bank of the 

Potomac River 1.0 mile (1.6 km) below Fairview Beach 

in King George County, Va. (Locality 13). On the Mattaponi River, it can be seen overlying the Marlboro Clay 

just below the Rte. 207 bridge on the right bank in 

Caroline County (Locality 32, fig. 20). The contact with 

the Marlboro is abrupt; burrows deep into the Marlboro 

contain Potapaco sediments. Medium to coarse sand is 

concentrated in the lower part of Bed A, and phosphate 

and quartz pebbles are common. An apparent reverse 

dip (trending north) brings the Marlboro below water 

level upriver of the Rte. 207 bridge and causes higher 

beds in the Potapaco to descend to water level with increasing distance above Locality 32. At a point where 

the R.F.& P. Railroad track passes near the left bank 

of the Mattaponi 1.5 miles (2.4 km) above the Rte. 207 

bridge (Locality 36), some 4.0 feet (1.2 m) of Bed A are 

exposed. Bed A descends to water level 2.4 miles 

(3.9 km) above the Rte. 207 bridge (Locality 37), indicating a continuing reverse dip. The MarlboroNanjemoy contact occurs at approximately 79 feet 

(24.1 m) above sea level just below the Rte. 207 bridge 

(Locality 32). In a small roadcut 0.9 mile (2.3 km) south 

of this locality on Rte. 676, the Nanjemoy-Calvert contact is exposed at approximately 90 feet (27.4 m). The 

relatively thin beds of the Nanjemoy in this area (11 feet 

(3.3 m)) indicate beveling of the Nanjemoy by a transgressing Calvert sea during the middle Miocene. The 

result is a thinning of Nanjemoy over an apparent high 

area and a thickening of that unit to the north and south 

on the flanks of that structure. An additional possible 

exposure of Bed A was found to the southeast, just 

below the Rte. 654 bridge on the left bank of the Mattaponi River in Caroline County (Locality 23), where it 

is overlain by bedded glauconitic sands of Bed B. The 

farthest updip exposure of Bed A on the Pamunkey 

River is at a large bluff, 1.0 miles (1.6 km) above the 

Rte. 301 bridge (Locality 33). There the unit consists 

of a weathered, brownish-gray (5 YR 4/1), micaceous, 

clayey sand. At Locality 24 on the Pamunkey (fig. 21), 

Bed A unconformably overlies the Marlboro Clay,
30 STRATIGRAPHY AND MOLLUSKS OF PAMUNKEY GROUP AND OLD CHURCH FORMATION

which, at that locality, is only 6.0 to 8.0 inches (15.2 to 

20.3 cm) thick. The upper surface of the Marlboro is intensely burrowed, and the burrows are filled with sediment from Bed A. Downstream, 0.65 mile (1.04 km) 

above Normans Bridge (Rte. 614), at a sharp bend 

(Locality 38, fig. 24), 4.0 feet (1.2 m) of Bed A are 

overlain, at least disconformably, by 6.0 feet (1.8 m) of 

Bed B. The contact is sharp and marked by the burrowed upper surface of Bed A as well as a concentration of pebbles. There is also an abrupt color change 

from the olive-black (5 Y 2/1) of Bed A to olive-gray (5 Y 

4/1) of Bed B. No exposures are known on the James 

River, but, if present, Bed A should be near sea level 

at the Rte. 156 bridge over the James in Prince George 

County, Va.

The lithic and faunal makeup of Bed A suggests an 

initial marine pulse and basal trangression following the 

quiet, protected embayment represented by the Marlboro Clay. Physical and paleontologic evidence indicates 

that little time is represented by the break between the 

Marlboro and Bed A of the Potapaco. Low molluscan 

diversity and small glauconite percentages reflect less 

than normally saline conditions during the deposition 

of Bed A. In spite of this reduced salinity, renewed 

marine influence is apparent. Dinoflagellate assemblages are marked by reduced diversity, the flora being dominated by a single taxon, indicating brackish 

or restricted marine conditions (L.E. Edwards, oral commun., 1984). Mollusks, in general, are poorly preserved 

but where present are low in diversity. The following 

mollusks were present above Port Royal on the Rappahannock (Locality 31). One of these taxa is illustrated 

on plate 3.

Venericardia potapacoensis Clark and Martin, 1901

Macrocallista sp.

Corbula sp.

Lucina sp. (fig. 10)

Lucina sp.

Cadulus sp.

Such a list indicates a somewhat restricted, shallowshelf environment but is of little help in determining an 

age for the unit other than a regional, relative stratigraphic placement. Calcareous nannoplankton, found in 

the Oak Grove core in Westmoreland County (Gibson 

and others, 1980) from the interval just above the 

Marlboro Clay, probably come from Bed A and indicate 

the placement of that bed in calcareous nannoplankton 

zone NP 10. This zonation indicates an early Eocene age 

assignment. Assemblages of pollen, dinoflagellates, 

foraminifers, and ostracodes tend to substantiate this 

placement. Dinoflagellates found in Bed A at two localities above the Rte. 207 bridge in Caroline County 

(Localities 36, 37) indicate an early Eocene age (L.E. 

Edwards, oral commun., 1984); on the basis of the

dinoflagellate data, Edwards believes that Bed A is correlative with the Bashi Member of the Hatchetigbee 

Formation (as used by MacNeil, 1946) as exposed at its 

type section as Bashi Creek in Alabama. Further, the 

small assemblage and the dominance of a single taxon 

point toward a restricted marine environment.

BED B BEDDED POTAPACO

Bed B, the most striking unit in the Potapaco, is easily recognized by its bedded appearance. This effect is 

created by the accumulation of a small bivalve, Venericardia potapacoensis Clark and Martin, 1901, in vast 

numbers along numerous, discontinuous, thin bedding 

planes (figs. 24, 25). Bed B varies in thickness from 

locality to locality. Its exact thickness in surface 

exposures is difficult to determine because of poor outcrops. It can be estimated to range from only a few feet 

(about 1 m) to more than 15 feet (4.6 m). The sediment 

in Bed B is olive-gray (5 Y 4/1), very clayey, glauconitic 

sand to sandy clay. The clay, when fresh, appears 

grayish-orange-pink (5 YR 7/2) and contains varying 

amounts of fine to medium glauconite and quartz sand. 

Glauconite content ranges from less than 10 percent in 

the westernmost exposures to more than 75 percent 

with increasing distance from the paleoshoreline. 

Bedded concretions ranging up to boulder size are common in Bed B. These concretions, although sometimes 

regionally traceable, are not sufficiently stratigraphically continuous to be used as marker beds. It is believed 

that Bed B is equivalent to parts of "zones" 13 and 14 

of Clark (1896b) and Clark and Martin (1901). "Zone" 

13 matches the description well, and "zone" 14 seems 

to correspond to parts of Bed B where the calcareous 

fossils have been leached out, leaving bands of molds. 

Often these surfaces are encrusted with gypsum 

crystals. The physical appearance of Bed B, especially 

the bedding, is so obvious that it may be identified easily in some section descriptions in the older literature. 

Descriptions by Clark (1896b), Clark and Martin (1901), 

and Clark and Miller (1912) indicate the presence of Bed 

B at many localities in Maryland and Virginia. Among 

the more notable of their localities are the bluff at 

Potomac Creek, Virginia (Bull Bluff on the Passapatanzy 7.5-min quadrangle map; Locality 11 of this report); 

3 miles (4.8 km) below Potomac Creek, Va.; 3 miles 

(4.8 km) above Popes Creek, Md.; and near Thrift in 

Prince Georges County, Md. These section descriptions 

reflect the homogeneous nature of the unit over a wide 

geographic area. Limited, poor exposures on the Patuxent River in Maryland make it difficult to observe the 

unit there, but the appearance of Bed C of the Potapaco 

Member plus the presence of the Woodstock Member 

0.85 mile (1.37 km) below Nottingham on the left bank
STRATIGRAPHY 31

FIGURE 24. Pamunkey River, 0.65 mile (1.04 km) above Normans Bridge (Rte. 614), 

King William County, Va. (Locality 38). Bed A (nonbedded) of the Potapaco 

Member of the Nanjemoy Formation is overlain by Bed B (bedded) of the Potapaco. 

The contact between the beds (arrow) is clearly exposed.

(Locality 39) indicate that Bed B should be near water 

level (sea level) in the vicinity of Lyons Creek Wharf, 

Calvert County (Locality 40).

The unit is present at Bull Bluff on the Potomac River 

(Locality 11), as previously stated, but is high in the section (62.5 feet, 19.0 m) and badly weathered. The same 

bed dips to water level 2.7 miles (4.3 km) below the big 

pier at Fairview Beach in King George County, Va. (Locality 41). The next occurrence downriver of Bed B of 

the Potapaco is 2.5 miles (4.0 km) above Popes Creek

on the left bank, Charles County, Md. (Locality 34, fig. 

26), where it exhibits the typical thin beds of Venericardiapotapacoensis Clark and Martin, 1901, and contains 

irregularly bedded, boulder-sized concretions. Sediments herein assigned to Bed B were found in the Oak 

Grove core by Reinhardt and others (1980). In that 

report the interval at 276.9 feet (84.4 m) was figured 

(fig. 8, p. 7) and clearly shows the crowding of the 

bivalve Venericardia potapacoensis Clark and Martin, 

1901.
32 STRATIGRAPHY AND MOLLUSKS OF PAMUNKEY GROUP AND OLD CHURCH FORMATION

FIGURE 25. Mattaponi River, 1.0 mile (1.6 km) east of Reedy Mill, Caroline County, Va. (Locality 45). Poorly preserved, 

disarticulated valves of Venericardia potapacoensis Clark and Martin are crowded along thin, locally continuous beds, 

as is typical of Bed B of the Potapaco Member of the Nanjemoy Formation.

On the Rappahannock River, Bed B is first exposed 

in a high bluff on the right bank just below the mouth 

of Ware Creek in Caroline County (Locality 35). There 

it may be seen to overlie bed A at approximately 22.0 

feet (6.7 m) above river level (sea level). It is seen again 

0.9 mile (1.4 km) downstream on the right bank at approximately 20.0 feet (6.0 m) above water level (Locality 42), and it dips to water level on the right bank opposite Goat Island (Locality 31). Downriver, exposures 

are scattered and poor, but a small stream cut on Mill 

Creek just below the now-drained Millers Pond (Locality 43) exposes as much as 8.0 feet (2.4 m) of Bed B. A 

short distance downstream on the left bank of the Rappahannock, just above the mouth of Gingoteague Creek 

(Locality 44), Bed C crops out at water level, suggesting 

that Bed B has dipped below sea level.

On the Mattaponi River, the lower portion of Bed B 

is exposed in a small gully adjacent to the Rte. 654 

bridge (Locality 23). Downriver, Bed B is exposed intermittently from I mile (1.6 km) (straightline) above 

Reedy Mill, Caroline County, to 0.6 mile (1.0 km) east of 

Reedy Millpond on the right bank. Best exposures, with 

preserved mollusks, are below Reedy Mill (Localities 45,

46, 47). There they show the typical, thinly bedded 

nature of Bed B with many Venericardia potapacoensis Clark and Martin, 1901, crowded along thin bedding 

planes (fig. 24). At Locality 46, beds with a pronounced 

reverse dip (approximately 4°) are exposed; the 

Venericardia bed dips upstream or northwest. These exposures occur at approximately 40 to 45 feet above sea 

level. Where Bed B reaches sea level in the Mattaponi 

River area can only be estimated until drilling 

establishes the location. The bed may be estimated to 

dip below sea level in the area of the Rte. 628 bridge 

over the Mattaponi in King William and King and 

Queen Counties, Va.

The next extensive outcrop area of Bed,B to the south 

is along the Pamunkey River from 0.65 mile (1.04 km) 

above Normans Bridge (Locality 38, fig. 24) to 0.8 mile 

(1.3 km) south of Hanovertown (Locality 48). At Locality 49, above Dabneys Millpond, Bed B is exposed between 5 and 10 feet (1.5 and 3.0 m) above water level 

(which here is approximately 5 feet (1.5 m) above sea 

level). Just below the boat landing at Dabneys Millpond 

(Locality 50, fig. 27), a good section is exposed in a high 

bluff that includes Beds B and C of the Potapaco, as
STRATIGRAPHY 33

f i V /-^-.*-

/ %-K'"' ' *'v | J

i;','"f / ' 't>!

FIGURE 26. Potomac River, 2.5 miles (4.0 km) upstream from Popes Creek, Charles County, Md. (Locality 34). E.G. Shaw 

(USGS, Reston, Va.) has her hand on a contact marking a diastem within Bed B of the Potapaco Member of the Nanjemoy 

Formation. The lower bed (A) of the Potapaco has a burrowed upper surface. The burrows are filled with sediment from B.

well as the Woodstock Member. Bed B crops out in the 

river bed where, at low water, thousands of Venericardia potapacoensis Clark and Martin, 1901, may be seen. 

Bed B also crops out to a height of 4 feet (1.2 m) depending on the water level, and contains abundant, 

poorly preserved Venericardia and common Cubitostrea. 

It is overlain by Bed C; the contact between the two 

is apparently gradational with no abrupt lithic change. 

Downriver, and along strike, at Hanovertown (Locality 51), small outcrops expose Bed B to a height of 8.0 

feet (2.4 m) (approximately 11 feet (3.4 m) above sea 

level). At a sharp bend 0.8 mile (1.3 km) south of 

Hanovertown, Hanover County, on the right bank of 

the Pamunkey (Locality 48), Bed B crops out to a height 

of 5.0 feet (1.5 m) at low water. Sediments exposed at 

low water contain moderately well preserved mollusks 

at approximately 5 feet (1.5 m) above sea level. To the 

east and downriver of this point, the burrowed, glauconitic clays of Bed C crop out, Bed B apparently having dipped below river level.

Bed B probably is present, but has not been seen, 

along the James River. Outcrop patterns of the Aquia, 

Marlboro, Nanjemoy, and Piney Point Formations

suggest that Bed B probably crops out near water level 

(sea level) just below the Rte. 156 bridge over the James 

in Prince George County, Va.

Sedimentological and faunal characteristics of Bed B 

indicate deposition in a shallow, somewhat restricted 

embayment. Glauconite grains, which appear to be concentrated in burrows, are common. The burrows and the 

concentrations of abraded bivalves along bedding 

planes suggest shallow depths, probably not below 

wave base. Glauconite-coated, worn, disarticulated 

valves of Venericardia indicate at least periods of slow 

sediment accumulation. Bivalves may be concentrated 

along those winnowed zones because of favorable bottom conditions or storms. Elsewhere in the section, 

where soft clays inhabited by burrowing organisms 

predominated, the bottom may not have been suitable 

for the settlement of bivalve larvae. The molluscan 

assemblage of Bed B is dominated (as much as 95 percent) by Venericardia potapacoensis Clark and Martin, 

1901. This small bivalve has a striking, forward umbonal inclination, which makes it easy to separate from 

even young individuals of Venericardia ascia Rogers 

and Rogers, 1839, found in the Woodstock Member.
34 STRATIGRAPHY AND MOLLUSKS OF PAMUNKEY GROUP AND OLD CHURCH FORMATION

FIGURE 27. Pamunkey River, just below the boat landing at Dabneys Millpond, King William County, Va. (Locality 50). 

P.F. Huddlestun (Georgia Geologic Survey, Atlanta, Ga.) is standing on Bed B of the Potapaco Member of the Nanjemoy 

Formation. Bed C of the Potapaco extends from approximately shoulder height up into the vegetation. The Woodstock 

Member of the Nanjemoy Formation is visible in the upper left clearing.

Gardner and Bowles (1939) pointed out the affinities of 

V. potapacoensis with V. clavidens Grzybowski, 1899, 

from Peru and with V. diga Gardner and Bowles, 1939, 

from Mexico. Both of these forms occur in the lower 

Eocene, but no analogue is known in the Gulf States. 

Another common, though never abundant, taxon is an 

unnamed species of Cubitostrea (pi. 3, figs. 1-6), which 

also occurs in the Woodstock Member. Toulmin (1977, 

pi. 35, figs. 1, 3) figured a specimen from the lower Tallahatta along the Chattahoochee River in Alabama that 

appears to be similar to, if not identical with, this species. A figure of a young Ostrea brevifronta Dockery, 

1980, found in the Bashi Formation (lower Eocene) in 

Mississippi (Dockery, 1980, pi. 4, fig. 4) appears very 

similar to the form from the Potapaco. Harris (1897, pi. 

6, fig. 2) figured a specimen from Hatchetigbee Bluff 

on the Tombigbee River in Alabama that closely resembles the Maryland and Virginia forms. Beds at Hatchetigbee Bluff from which the specimens were collected 

are considered to be lower Eocene. A collection from 

Tunnell Springs, Monroe County, Ala., in a railroad cut, 

contains specimens of Cubitostrea that appear to be the 

same species. The thin marine bed exposed there is,

stratigraphically, somewhat higher in the Hatchetigbee 

Formation than the Bashi but is still considered to be 

lower Eocene. Other mollusks present in Bed B occur in 

small numbers and are of little stratigraphic value. 

These include the following genera (see pi. 3):

Vokesula sp. (figs. 9, 11)

Lucina sp. (fig. 10)

Nucula sp.

Nuculana parva (Rogers, 1837) (fig. 8)

Macrocallista sp.

Cadulus sp. (fig. 12)

Calcareous nannofossils are poorly preserved in many 

parts of the basin, but the core at Oak Grove, Westmoreland County, Va., contained an assemblage in the 

Potapaco indicative of NP 10 and NP 11 (Gibson and 

others, 1980). L.M. Bybell (oral commun., 1984) believes 

that this part of the Potapaco contains nannofossils 

assignable to NP 11. Detailed work on dinoflagellates 

by L.E. Edwards (USGS) has enabled her to correlate 

those assemblages with the calcareous nannofossil zonation. In this way, the wide areas lacking calcareous 

forms can be safely zoned. Such an area is the updip 

region of Virginia where nannofossils are scarce or
STRATIGRAPHY 35

leached out. Along the Pamunkey River, samples from 

Bed B have been found to contain a dinoflagellate flora 

correlative to what has been called NP 10 or 11.

BED C BURROWED POTAPACO

Above the thin-bedded clayey sand of Bed B is a 

series of sandy clays to clayey sands, which is easily 

recognized by its intensely burrowed appearance. Bedding, if it was ever present, has been obscured by bioturbation except along a few very thin planes. Along those 

surfaces sedimentation appears to have been interrupted; they are marked by at least regional diastems, 

a concentration of glauconitic sand, and glauconite-filled 

burrows extending down into the underlying sediment. 

These stratigraphic breaks, if that is what they represent, have not been traced over a wide area and may 

be only local, possibly current-scoured surfaces. The 

dominant lithic characteristic of Bed C is its very clayey 

texture, with interspersed grains of fine- to mediumsand-sized glauconite in a grayish-orange-pink (5 YR 

7/2) clay matrix. In some areas, the concentration of 

glauconite is such that the lithology is best described 

as a clayey sand. This very clayey, glauconitic texture 

is typical of the entire Potapaco Member, but the intensely burrowed nature of the unit is unique to Bed 

C. The macrofossils in Bed C are principally small or 

broken, poorly preserved mollusks that are concentrated in burrows and make up a small percentage of 

the bed. Thicknesses of as much as 20 feet (6.1 m) of 

Bed C have been observed in outcrop. The bed overlies 

Bed B with no distinct contact between the two, suggesting a gradation from one environmental regime to 

another. In most of its outcrop area, Bed C is overlain 

by the Woodstock Member of the Nanjemoy Formation. 

On the Pamunkey River, at least, Bed C is overlain by 

a thin bed, 1.5 to 3.0 feet (0.5 to 0.9 m) thick, of clayey, 

glauconitic sand marked by a series of boulder-sized indurated blocks. The contact between Bed C and the 

younger unit, Bed D, is abrupt and is marked by a sharp 

but burrowed contact indicating a probable diastem. 

Elsewhere, where Bed D is missing, the Bed CWoodstock boundary is disconformable and is marked 

by an abrupt change in lithology, a lag deposit of 

phosphate, bone, pebbles, and wood in the lower 

Woodstock, and burrows containing Woodstock sediment several feet into the underlying Bed C. The oliveblack (5 Y 2/1), very fine, well-sorted, micaceous, 

glauconitic sand of the Woodstock is easily distinguishable from the very clayey, burrowed sands of Bed C. 

This contact has been observed on the Patuxent, 

Potomac, Mattaponi, and Pamunkey Rivers.

Bed C is present on the Patuxent River from 0.3 to 0.8 

mile (0.5 to 1.4 km) above Jones Point, Calvert County,

Md. (Localities 52, 39). There it is disconformably 

overlain by the Woodstock. The Potapaco-Woodstock 

contact is sharp and burrowed and is marked by a line 

of pebbles as well as by the textural changes previously mentioned. At both localities (52 and 39), 15.0 feet 

(4.5 m) of Bed C is exposed near water level (sea level); 

it consists of a very burrowed, olive-gray (5 Y 4/1) 

(grayish-yellow, 5 Y 8/4, where weathered), clayey, 

glauconitic sand. Weathering of the burrows has 

brought out their detail; they appear to have been built 

by Callianassa, a burrowing, shrimp-like arthropod. 

Above Popes Creek on the left bank of the Potomac 

River, Charles County, Md., the area in which Bed C 

probably descends to water level is slumped and 

obscured, causing weathering of the cliff face. However, 

in 1969 an unusual combination of wind and tide swept 

much of the normal beach sand away and revealed an 

intensely burrowed unit at beach level and below. The 

burrows were apparently made by the burrowing 

shrimp Callianassa and were visible for several miles 

above Popes Creek. They were best developed 0.4 mile 

(0.6 km) above the mouth of Popes Creek (Locality 53). 

These beds are now covered by slump and beach sand 

in that area. Below Popes Creek, the Woodstock 

Member descends to beach level, indicating that the 

contact between Bed C and the Woodstock probably 

reaches water level (sea level) very near Popes Creek.

On the Rappahannock River, Bed C is visible only on 

the left bank 0.4 mile (0.6 km) above the mouth of 

Gingoteague Creek (Locality 44). There some 10.0 feet 

(3.0 m) of the unit is exposed at beach level (sea level). 

At the next exposure downstream, just above Greenlaw 

Wharf on the left bank (Locality 54), the Woodstock 

crops out, Bed C presumably having dipped below sea 

level.

Outcrops of Bed C on the Mattaponi River are known 

at numerous small exposures below Reedy Mill. There 

Bed C is overlain by the Woodstock Member (Localities 

55, 56, 57, 58) (see fig. 28). Bed C is better exposed at 

places along the Pamunkey River where some 15 feet 

(4.6 m) crops out and its upper and lower contacts may 

be seen. At the large bluff just below the boat landing 

at Dabneys Millpond (Locality 50, fig. 27), Bed C is exposed from 4 feet (1.2 m) above water level (approximately 13 feet (2.7 m) above sea level) to approximately 14.0 feet (4.2 m) above water level (23 feet (7.0 m) 

above sea level). It consists of a very bioturbated, 

clayey, somewhat weathered, olive-gray (5 Y 4/1) and 

grayish-yellow (5 Y 8/4) glauconitic sand. At least three 

"contacts" may be seen within the unit. These appear 

to represent only pauses in deposition or current winnowing, because identical Ethologies occur above and 

below. Medium-sized glauconitic sand is concentrated 

above the contact and fills burrows into the underlying
36 STRATIGRAPHY AND MOLLUSKS OF PAMUNKEY GROUP AND OLD CHURCH FORMATION

- ;c«^>- * ££

P* * >^*fsr _ -fe4K.. 1. «

FIGURE 28. Mattaponi River, 0.8 mile (1.28 km) southeast of Reedy Mill, Caroline County, Va. (Locality 58). D.R. Womer 

(USGS, Reston, Va.) has his pick on the contact between the Potapaco Member (below) and the Woodstock Member 

of the Nanjemoy Formation.

sediment. Small shell fragments are present but are 

poorly preserved. The low bluffs between Dabneys Millpond and 0.7 mile (1.1 km) south of Hanovertown 

(Locality 48) expose only small sections of Bed B. Poor 

exposures of Bed C are present along the stretch of the 

Pamunkey 0.55 mile (0.89 km) downriver of the sharp 

bend below Hanovertown to a point 1.45 miles (2.33 km) 

southeast of Hanovertown (Localities 59, 60). Bed C is 

best seen in a series of excellent, though low, outcrops 

beginning 0.4 mile (0.6 km) below the mouth of 

Totopotomoy Creek and continuing to the sharp bend 

to the east, 0.2 mile (0.3 km) downstream. Below this 

point the Woodstock Member descends to river level 

(approximately 2.5 feet (0.8 m) above sea level). The outcrop nearest the bend, and another about 0.1 mile (0.2 

km) above the bend, expose Bed C to a height of 5.0 feet 

(1.5 m) (Localities 61, 62). It consists of glauconitic, burrowed, olive-gray (5 Y 4/1) clay. Bed C is overlain, at 

these two outcrops and the following one upstream 

(Locality 63), by Bed D, a thin bed, 1.5 to 2.0 feet (0.5 

to 0.6 m) thick, of clayey, very glauconitic sand that has 

only been seen in this area. Bed D is, in turn, overlain 

by the Woodstock Member. The contact between Bed

C and the overlying Bed D is sharp and marked by a 

lag deposit of phosphate pebbles, burrows into the top 

of Bed C, and a coarser texture in the basal part of Bed 

D. Higher concentrations of glauconite in Bed D make 

the unit easily distinguishable from the more clayey, 

burrowed Bed C below. The contact between the two 

units appears to represent a hiatus of longer duration 

than the breaks observed within Bed C. A reverse dip 

(upriver, to the northwest) brings the top of Bed C to 

within 2.5 feet (0.8 m) above water level (which here is 

sea level) at Locality 63. Downriver of this area, Bed 

C is believed to have dipped below water level. The unit 

is not exposed on the James River, but if present it 

would approach water level (sea level) in the vicinity of 

Indian Point, on the right bank, below the Rte. 156 

bridge, King George County.

Biostratigraphic information afforded by mollusks is 

meager in Bed C. Apparently bottom conditions were 

unsuitable for settlement by most taxa. The extreme 

bioturbation seen in Bed C certainly played a part in 

the absence of adult or large mollusks. Probably the 

very clayey aspect of Bed C was also a limiting factor. 

The result is a nondiverse assemblage (where preserved)
STRATIGRAPHY 37

consisting of a few Corbula, Lucina, and Cadulus that 

offer little evidence of age. The lithic combination of 

clays mixed with sand-sized glauconite and quartz, 

together with the intricate burrow systems, indicate a 

shallow (above wave base), restricted embayment, 

perhaps protected by offshore bars, which served to 

trap the finer sediment. The presence of Callianassa indicates high-energy conditions, possibly accomplished 

by current or tidal scour, and at least near normal 

salinities. Dinoflagellate assemblages indicate nearshore or high-energy conditions and an abundant source 

of nutrients (L.E. Edwards, oral commun., 1984). On the 

basis of the dinoflagellate flora, Bed C may be correlated 

with calcareous nannoplankton zone NP 10 or 11. 

Samples examined for nannoplankton by J.A. DiMarzio (oral commun., 1984) were barren in the Pamunkey 

River area.

BED D CONCRETION-BED POTAPACO

As previously mentioned, Bed D crops out along the 

Pamunkey River only from Locality 63 to Locality 61, 

below the mouth of Totopotomoy Creek. Upriver, at 

Dabneys Millpond (Locality 50), Bed D is not present, 

possibly having been beveled off by the transgressing 

Woodstock sea. There the Woodstock directly overlies 

Bed C. Bed D, in its small outcrop area, consists of 1.5 

to 2.0 feet (0.5 to 0.6 m) of clayey, very glauconitic sand 

and is marked above and below by sharp contacts. Both 

contacts are marked by abrupt changes in lithology and 

color and contain concentrations of phosphate pebbles, 

quartz, and wood. Burrows at both contacts extend 

down into the underlying beds. The high glauconite content of Bed D makes it easily differentiated from the 

lighter colored clays of Bed C and the less glauconitic 

silty sand of the basal portion of the Woodstock 

Member (see fig. 29). At Localities 61 and 62 the lower 

contact of Bed D is at approximately 5 feet (1.5 m) 

above water level (7.5 feet (2.3 m) above sea level). The 

bed is marked by a line of cobble- to boulder-sized concretions in the middle of the unit. Further upstream 

(Locality 63), as previously mentioned, a reverse dip 

brings the top of Bed D to within 4.5 feet (1.4 m) above 

river level (5.0 feet (2.1 m) above sea level).

Mollusks in Bed D, in the small area they could be 

studied, are very poorly preserved, small, and fragmentary. Recognizable forms included Corbula, Lucina, 

Venericardia, and Cadulus. Adequate molluscan 

evidence on the environment is lacking, but the 

assemblage, together with the more massively bedded, 

more evenly textured, very glauconitic lithology of the 

unit, indicates near normally saline, open, shallow-shelf 

conditions. Dinoflagellates obtained from Bed D indicate near-shore or marginal-marine conditions much

like those of Bed C (L.E. Edwards, oral commun., 1984). 

The similarity of floras in the two beds may be the result 

of reworking into the very thin Bed D. However, the 

dinoflagellate assemblage indicates an equivalency with 

calcareous nannoplankton zones NP 10 and 11. NP 11 

was recognized in the Oak Grove core in Westmoreland 

County (Gibson and others, 1980), where it may represent the same beds recognized on the Pamunkey River 

as Bed D.

WOODSTOCK MEMBER

The Woodstock Member of the Nanjemoy was first 

proposed by Clark and Martin (1901, p. 66) for beds of 

glauconitic sand exposed near Woodstock, "an old 

estate situated a short distance above Mathias Point," 

King George County, Va. The term "Woodstock" had 

previously been used by Clark (1895,1896b) to describe 

the Woodstock Stage, a unit defined principally on its 

fauna. Clark and Martin (1901) described the member 

as consisting of their two lithic "zones" 16 and 17. The 

bluff described by Clark (1896b, p. 40, pi. IV, Section 

III) and Clark and Martin (1901, p. 70, Section IX) exhibits both the Potapaco and Woodstock Members and 

is therefore designated herein the lectostratotype section for the Woodstock. It is just downstream from 

Locality 67 of this report. (See fig. 30 for locality map.)

The Woodstock Member of the Nanjemoy consists of 

olive-black (5 Y 2/1), very fine, well-sorted, silty, 

glauconitic sands. The glauconite content increases 

markedly from a low of 10-15 percent in its most inland outcrops to 70-80 percent in its most seaward exposures. Carbonaceous material in the form of logs, 

branches, and nuts is abundant. The Woodstock unconformably overlies the Potapaco Member and is unconformably overlain either by the Piney Point Formation, 

where present, or by younger beds, depending on the 

area. The lower contact with the Potapaco is a constant 

and easily recognized feature that may be seen from the 

Patuxent River to the Pamunkey River. Biostratigraphically there is a significant fauna! and floral change at 

this boundary, though it marks only a relatively brief 

hiatus. The Woodstock may be distinguished from the 

underlying Potapaco by its fine-textured, micaceous, 

massive appearance, in contrast to the very clayey, 

poorly sorted, bioturbated texture of the underlying 

Potapaco.

Molluscan assemblages in the Woodstock are diverse 

and abundant and are scattered throughout the fine 

matrix. Large valves of Venericardia ascia Rogers and 

Rogers, 1839, are concentrated along bedding planes 

in some areas but are easily distinguished from the 

much smaller Venericardiapotapacoensis found in the
38 STRATIGRAPHY AND MOLLUSKS OF PAMUNKEY GROUP AND OLD CHURCH FORMATION

FIGURE 29. Pamunkey River, 0.58 mile (0.93 km) below the mouth of Totopotomoy Creek, Hanover County, Va. (Locality 

61). Beds C (below lower arrow) and D (between arrows) of the Potapaco Member of the Nanjemoy Formation are 

exposed. Bed D is unconformably overlain by the Woodstock Member (above upper arrow).

Potapaco Member. The overlying Piney Point Formation is coarser textured, clayey, and poorly sorted. Both 

units contain a large number of mollusks, but they have 

no species in common. In some areas along the 

Pamunkey River, mollusks from the Woodstock have 

been reworked upward into the base of the Piney Point. 

This is clearly illustrated at Locality 64, where the Piney 

Point transgression beveled across a bed of articulated 

Venericardia ascia in living position. Specimens of this 

taxon were reworked upward, the valves still adhering, 

and showing almost no abrasion, by as much as 1 foot 

(0.3 m) into the overlying Piney Point. Their origin is 

easily determined, however, by the presence of distinctive, olive-black (5 Y 2/1), micaceous, silty, very fine 

sand of the Woodstock within the double valves.

Outside of the Pamunkey River and James River 

areas, the Woodstock is directly overlain by beds 

younger than the Piney Point. On the Patuxent River 

above Jones Point, Calvert County, Md. (Locality 52), 

the Woodstock is directly overlain by a basal sandstone 

included in the Calvert Formation. This sandstone is 

"zone" 2 of Shattuck (1904) and is early Miocene in age. 

At the old Kaylorite mine 1.2 miles (1.9 km) above

Nottingham on the left bank (Locality 65) and at White 

Landing on the right bank (Locality 66), the Woodstock 

is overlain by a thin bed referred to as "zone" 1 of the 

Calvert Formation by Shattuck (1904). This bed has 

been determined, on the basis of mollusks, pollen, and 

dinoflagellates, to be of late Oligocene or early Miocene 

age. It is lithologically distinct from the underlying 

Woodstock and the overlying Calvert ("zones" 2-15). 

The unit may correlate with a similar bed on the 

Pamunkey, herein termed the Old Church Formation 

(described later) and with the Belgrade Formation in 

North Carolina, the Edisto Formation in South Carolina, and the Tampa Formation in Florida.

Along the Potomac River above Mathias Point on the 

right bank (Locality 67) (see fig. 31) and above and below 

Popes Creek on the left bank (Localities 53, 68) (see fig. 

32), the Woodstock is overlain by transgressive sediments of the Calvert Formation that range from early 

to middle Miocene in age. The contact is marked by a 

basal lag concentration of phosphate and quartz pebbles, a burrowed surface, and an abrupt lithic change 

from glauconitic sands to olive-brown, clayey, phosphatic sand. At the downriver end of the bluffs below
STRATIGRAPHY 39

15 KSLOfViETERS

FIGURE 30. Map showing localities where the Woodstock Member of the Nanjemoy Formation 

is exposed or found in cores used in this study. Numbers refer to localities mentioned in the text.
40 STRATIGRAPHY AND MOLLUSKS OF PAMUNKEY GROUP AND OLD CHURCH FORMATION

 i \

FIGURE 31. Potomac River, 1.65 miles (2.66 km) above Mathias Point, King 

George County, Va. (Locality 67). The upper surface of the Woodstock Member 

(A) of the Nanjemoy Formation is deeply eroded and intensely burrowed. It 

is overlain by the weathered, yellowish-gray, silty sands and clays of the Calvert 

Formation (B). The pick is imbedded near the bottom of a sharp cut into the 

Woodstock.

Popes Creek (Locality 69), a very thin tongue of burrowed gray clay and a bed of glauconitic sand occur 

between the good, easily recognized Woodstock and the 

Calvert. These two beds thicken downstream but are 

beveled off before reaching Popes Creek. Macrofossils 

are leached from the beds, but dinoflagellates indicate 

that they are early Eocene in age (L.E. Edwards, oral 

commun., 1984). It seems best, therefore, to include 

them in the Woodstock in spite of their very different

lithologies. It is believed that these units are represented in the Oak Grove core by the clay and sand beds 

shown as occurring in the upper Nanjemoy by 

Reinhardt and others (1980, fig. 1). They probably represent a separate marine pulse from that which resulted 

in the deposition of the Woodstock (in its strict sense) 

but are best included in that unit until their stratigraphic and areal relationships can be assessed. 

On the Rappahannock River, as much as 4 feet (1.2 m)
STRATIGRAPHY 41

FIGURE 32. Potomac River, 0.4 mile (0.6 km) above Popes Creek, Charles County, Md. (Locality 53). The Woodstock Member 

of the Nanjemoy Formation is overlain by the Calvert Formation; an arrow marks the contact.

of the Woodstock Member may be seen on the left bank, 

just above Greenlaw Wharf (Locality 54) (see fig. 33). 

It is overlain there by a grayish-yellow, poorly sorted, 

slightly glauconitic and pebbly sand. The contact between the two units is decidedly undulant and exhibits 

several feet of relief. A lag of pebbles as well as burrows mark the contact. This previously unrecognized 

unit (herein provisionally included in the Woodstock 

Member) is also present at the upriver end of the bluffs 

below Wilmont Wharf (Locality 70) where it is overlain 

by the Calvert Formation. On the Mattaponi River, the 

Woodstock crops out continuously from Reedy Mill on 

the right bank (Locality 71) to 1.8 miles (2.9 km) 

(straightline) above the mouth of Maracossic Creek, also 

on the right bank (Locality 72). At the next exposure 

downstream, 1.3 miles (2.1 km) above the mouth of 

Maracossic Creek (Locality 73), the Woodstock has apparently passed below river level and a clean, ripplemarked and pebbly sand crops out. This unit bears a 

strong resemblance to the previously described bed that 

overlies the Woodstock on the Rappahannock River at 

Greenlaw and Wilmont Wharves (Localities 54, 70). 

From Reedy Mill (Locality 71) to 0.95 mile (1.53 km) east 

of Reedy Mill (straightline) on the left bank (Locality

55), the olive-black (5 Y 2/1), silty, micaceous sand of 

the Woodstock overlies the olive-gray (5 Y 4/1) clay of 

the Potapaco Member (fig. 28). The contact is abrupt, 

marked by a pebble lag and burrowing, and is easy to 

delineate owing to marked color differences in the two 

beds.

The Woodstock Member is probably best seen along 

the Pamunkey River, where it is almost continuously 

exposed from the bluff just below the boat landing at 

Dabneys Millpond (Locality 50, fig. 27) to 0.85 mile 

(1.37 km) (straightline) southeast of the Newcastle 

Bridge ruins (Locality 64). Just below Dabneys Millpond (Locality 50), the Woodstock overlies Bed C of the 

Potapaco Member. The contact is marked by pebbles, 

a concentration of glauconite, a burrowed contact, and 

carbonized wood. The next good exposure downriver of 

the Woodstock begins 0.4 mile (0.6 km) (straightline) 

below the mouth of Totopotomoy Creek (Locality 63) 

and continues intermittently for some miles downstream. At Locality 63 and for approximately 0.5 mile 

(0.8 km) downstream (Localities 61, 62) (see fig. 32), the 

Woodstock overlies the thin tongue of sediment 

previously designated Bed D. Here again, the contact 

is marked by a pebble concentration, burrows, and
42 STRATIGRAPHY AND MOLLUSKS OF PAMUNKEY GROUP AND OLD CHURCH FORMATION

FIGURE 33. Rappahannock River, 0.2 mile (0.3 km) above Greenlaw Wharf, King George County, Va. (Locality 54). The 

Woodstock Member of the Nanjemoy Formation is overlain by a pebbly, slightly glauconitic sand of uncertain affinity.

wood. Bed D of the Potapaco is considerably more 

glauconitic than the basal part of the Woodstock and, 

as a result, is much darker in color. This difference 

makes tracing of the contact, and accompanying burrows, relatively easy. The Woodstock contains much 

carbonaceous material and ranges from 15 to 25 feet 

(4.6 to 7.6 m) in thickness along this section, although 

it is covered by vegetation and slump over much of the 

area. Shell material is scattered throughout and increases in size upwards. Glauconite content increases 

higher in the section and downdip, whereas the wood 

content decreases higher in the section and downdip. 

Along the Pamunkey, the Piney Point Formation 

(middle Eocene) directly overlies the Woodstock, 

separated by a sharp, easily recognized unconformity. 

This relationship is first seen in a ravine 0.63 mile 

(1.01 km) (straightline) south-southeast of the mouth of 

Totopotomoy Creek on the right bank of the Pamunkey 

(Locality 74, fig. 34). There some 15.0 feet (4.6 m) of 

olive-black (5 Y 2/1), very fossiliferous Woodstock is 

overlain by 3.0 feet (0.9 m) of yellowish-gray (5 Y 8/1), 

leached, somewhat indurated, poorly sorted, shelly sand 

of the Piney Point Formation. At this updip locality, 

the Piney Point contains less than 5.0 percent glauconite, and its relatively light color is in sharp contrast to 

the dark, very glauconitic Woodstock. This color and

textural difference enables the observer to recognize 

burrows filled with Piney Point sediment as far as 8.0 

feet (2.4 m) down into the Woodstock. Burrows are common, relatively large, and deep there (Locality 74) but 

are even more numerous downstream, making the collection of uncontaminated samples difficult. As 

previously mentioned, reworking of sediment and fossils 

is common along the contact. The elevation of the contact is variable from place to place and does not follow 

a simple, predictable, regional dip. This variation may 

have been achieved by the transgression of the Piney 

Point sea over a deeply dissected Woodstock surface, 

but it is my opinion that some of these anomalous relationships may be related to structural movements as 

shown by several beds that dip west or northwest, opposite the normal seaward dip. Numerous exposures of 

the Woodstock-Piney Point contact are exposed below 

the Rte. 360 bridge (Localities 75, 76, 77, 64) (see fig. 

35). The Woodstock passes below water level (sea level) 

near the dead end of Rte. 732 at the Pamunkey River 

(downriver of Locality 64).

Along the James River valley, the Woodstock is 

known only from a ravine below the mouth of Baileys 

Creek on the right bank of the James River, Prince 

George County (Locality 78). There it is directly overlain 

by a thin tongue of the Cobham Bay Member of the
STRATIGRAPHY 43

FIGURE 34. A small ravine along the Pamunkey River, 0.63 mile (1.01 km) 

south-southeast of the mouth of Totopotomoy Creek, Hanover County, Va. (Locality 74). The upper surface of the Woodstock Member of the Nanjemoy Formation is intensely burrowed as deep as 8 feet (2.4 m). The Woodstock is overlain 

by the Piney Point Formation, and material from that unit fills the burrows.

Eastover Formation. Its lower contact is not exposed 

there, but it presumably overlies the Potapaco Member. 

The Woodstock sea occupied a broad embayment 

reaching from at least the Patuxent River in Maryland 

to a short distance south of the James River in Virginia. 

The locus of the embayment was somewhat south of the 

Potomac River. Work by Enright (1969) indicated the 

presence of a probable lower Eocene equivalent to the 

Woodstock, the Squankum Member of the Shark River 

Formation, in New Jersey. No other equivalents of the 

Woodstock, in the subsurface or otherwise, have been 

detected along the Atlantic Coastal Plain. The only

known possible Gulf Coast equivalent occurs at Hatchetigbee Bluff on the Tombigbee River, Ala. (Locality 

79). There, near the top of the lower Eocene section, is 

a marine bed that unconformably overlies the lagoonal 

and deltaic f acies of the Hatchetigbee Formation. This 

unit, which by definition is included in the Hatchetigbee, is overlain by the Tallahatta Formation and was 

numbered Bed 4 by Smith and Johnson (1887, p. 40). 

The unconformity between this and the underlying bed 

may mark the same break as that between the Woodstock and Potapaco. 

The Woodstock contains a large, diverse molluscan
44 STRATIGRAPHY AND MOLLUSKS OF PAMUNKEY GROUP AND OLD CHURCH FORMATION

FIGURE 35. Contact between the Woodstock Member of the Nanjemoy Formation and the Piney Point Formation along the Pamunkey River. A, The termination of Rte. 732, Hanover County, Va. (Locality 64). The 

lighter colored, more calcareous Piney Point lithology shows in sharp contrast to the darker, very glauconitic 

Woodstock Member. B, Approximately 200 yards upriver of Locality 64, where the Woodstock-Piney Point 

contact approaches water level (sea level).
STRATIGRAPHY 45

fauna. Many of the taxa are new, and their stratigraphic 

significance is at present poorly understood. A number 

of species are listed by Clark and Martin (1901) as being present in the Woodstock, but the list is in serious 

need of updating. Species most often observed by me 

include the following (pi. 4):

Venericardia ascia Rogers and Rogers, 1839 (figs. 

8, 9)

Cubitostrea sp. (figs. 2, 3, 4)

Pitar ovata (Rogers, 1837)

Macrocallista subimpressa (Conrad, 1848) (fig. 6)

Corbula aldrichi Meyer, 1885 (fig. 7)

Lucina dartoni Clark, 1895 (fig. 10)

Nuculana sp. (fig. 5)

Glycymeris sp. (fig. 1)

Turritella sp. (figs. 12, 13)

Lunatia sp. (fig. 11)

Cadulus sp. (fig. 14)

Venericardia ascia Rogers and Rogers, 1839, resembles, 

but is not identical with, V. hatcheplata Gardner and 

Bowles, 1939, from the Hatchetigbee Formation (lower 

Eocene) of Alabama. Pecten choctavensis Aldrich, 1895, 

is present in both the Hatchetigbee and the Woodstock 

but is not common.

Best evidence, at this time, of the age and correlation 

of the Woodstock is found in the dinoflagellate and 

calcareous nannofossil assemblages. Calcareous nannofossils in the Putneys Mill core (Locality 86) indicate 

an approximate equivalence with nannofossil zone NP 

12 (L.M. Bybell, oral commun., 1984). This zone was also 

reported in the Oak Grove core (Gibson and others, 

1980) in the interval between 227.0 and 269.4 feet (69.2 

and 82.1 m). L.M. Bybell (oral commun., 1984) now 

believes that only the 69.2-m interval in the Oak Grove 

core contains calcareous nannofossils indicative of NP 

12. That sample lies just above a lithic break shown by 

Reinhardt and others (1980, p. 3) at 75 m. A sample 

taken at 75.6 m contains an NP 11 flora and is believed 

to be near the top of the Potapaco Member. Dinoflagellate data from the Woodstock Member also indicate an 

equivalence with NP 12 (L.E. Edwards, oral commun., 

1984). Edwards says the Woodstock contains the oldest 

occurrence of Kisselovia coleothrypta (Williams & 

Downie) Lentin & Williams, which to many authors 

equates approximately with the base of NP 12.

Molluscan assemblages in the Woodstock Member indicate a gradual return to open-marine, shallow-shelf 

conditions. In the lower one-third of the unit, molluscan 

diversity is relatively low and the assemblage is 

dominated by small forms. Carbonized wood and nuts 

are especially abundant in the lower section. The 

Woodstock shows a gradual trend towards deeper water 

with greater distance from the paleoshoreline. Diversity and size of mollusks increase to the east, and the

amount of carbonaceous material decreases. Nuts have 

been reported from the Woodstock by Ruffin (1850), 

Hollick (in Clark and Martin, 1901), and Mazer and Tiffney (1982). Although wood may be found at many horizons in the Paleocene-Eocene sequence, it is certainly 

most abundant in the Woodstock. The nuts, which are 

locally abundant in the Woodstock, are known only 

from that unit. These fruits are assigned to the genus 

Wetherellia; they are also found in the London Clay and 

Lower Bagshot Beds in England, both of which are considered to be lower Eocene (Mazer and Tiffney, 1982).

PINEY POINT FORMATION

The Piney Point, where fresh, is an olive-gray (5 Y 4/1), 

clayey, poorly sorted, very glauconitic, highly fossiliferous sand. It was first described from cuttings taken in 

a well at Piney Point, St. Marys County, Md. (Locality 

80), by Otton (1955). From the first usage, the age and 

correlation of the Piney Point have caused confusion. 

Beds on the Pamunkey River herein placed in the Piney 

Point do, by their inclusion in the original definition, 

belong in the Pamunkey Formation of Darton (1891). 

Clark and Martin (1901) elevated the Pamunkey to 

group rank and proposed two subdivisions: the Aquia 

Formation and the Nanjemoy Formation. The Nanjemoy Formation, or its upper member, the Woodstock, 

as originally described by Clark and Martin (1901), did 

not include the younger beds (Piney Point) seen along 

the Pamunkey River. In a later work, Clark and Miller 

(1912) apparently lumped younger beds observed along 

the Pamunkey River, and now considered to be Piney 

Point, in the Nanjemoy. Sections described on the 

James River by Clark and Miller (1912) also include the 

younger beds with the Nanjemoy. It is clear, however, 

that the original definition of the Nanjemoy included 

no beds equivalent to the Piney Point; Clark and 

Miller's (1912) inclusion of those beds in the Nanjemoy 

was not an attempt to expand the definition of that 

stratigraphic concept but, rather, a failure to differentiate the beds. Further, the younger unit may be seen 

to overlie the Nanjemoy unconformably, the contact being marked by an abrupt lithic, f aunal, and floral change 

indicative of a lengthy hiatus. The lithic characteristics 

of the Piney Point make it an easily distinguishable unit 

that can be, and has been, extensively traced and 

mapped, both on the surface and in the subsurface. I 

prefer, therefore, to consider the Piney Point a formation within the Pamunkey Group.

One complication of the concept of the Piney Point 

has been the use of that term for an unnamed upper 

Oligocene unit (possibly the Old Church Formation defined in this report) that was traced in the subsurface
46 STRATIGRAPHY AND MOLLUSKS OF PAMUNKEY GROUP AND OLD CHURCH FORMATION

of Maryland, Delaware, and New Jersey (Olsson and 

others, 1980). Brown and others (1972) listed a number 

of species of ostracodes and foraminifers from the type 

well of the Piney Point that clearly show the age of the 

unit to be middle Eocene (Claibornian). In their figure 2, 

Olsson and others (1980) indicated that the unit that 

they called "Piney Point" was not present in their St 

MEf 56 well, even though they are only a short distance 

from the type well of the Piney Point where Otton (1955) 

reported 50 feet (15.2 m) of Piney Point. It is evident 

that Olsson and others (1980), used the term "Piney 

Point" for a younger bed, which they showed to be late 

Oligocene in age and which overlies the Piney Point Formation as conceived by Otton (1955).

Otton (1955) adequately described the Piney Point as 

consisting of "light gray to yellowish glauconitic sand 

and interbedded 'rock' or shell layers containing a 

foraminiferal assemblage distinctive from that of the 

overlying and underlying deposits." The shell layers 

that form "rock" are principally Cubitostrea sellaeformis (Conrad, 1832). When present in large numbers, this 

oyster becomes cemented into very hard, thick beds, 

probably owing to its calcitic shell structure. Like many 

of the lower Tertiary units, the Piney Point becomes 

progressively more glauconitic, both in a seaward direction and higher in the section. Generally, the Piney 

Point is a much lighter color than the underlying 

Woodstock Member, partly due to its much higher shell 

content. Where weathered, the bed is yellowish orange 

(10 YR 7/6) in color because of glauconite decomposition. Where fresh, the Piney Point has a decided "salt 

and pepper" look to it because of the mixture of dark 

glauconite grains and small, light shell fragments. The 

unit is richly fossiliferous and contains a large (around 

150 species), well-preserved molluscan assemblage, 

which is largely unstudied. Most conspicuous is the 

large oyster Cubitostrea sellaeformis (Conrad, 1832), 

which in some cases makes up a large proportion of the 

rock.

The Piney Point may be seen along the James and 

Pamunkey Rivers to overlie the Woodstock Member of 

the Nanjemoy Formation unconformably (see figs. 36, 

37). Best exposures of the contact between the two units 

occur almost continuously along the Pamunkey from 

1.75 miles (2.82 km) above the Rte. 360 bridge over the 

Pamunkey River (Locality 74, fig. 34) to 1.0 mile 

(1.6 km) below the ruins of the Newcastle bridge (Locality 64, fig. 35). There the contact is very sharp and is 

marked by an abrupt lithic change from the very fine, 

silty, micaceous, dark sands of the Woodstock to the 

much lighter colored, poorly sorted, clayey, coarse sands 

of the basal Piney Point. Burrowing of the Woodstock 

surface is intense; individual burrows filled with Piney

Point sediment penetrate as much as 8.0 feet (2.4 m) 

downward (see fig. 34). Reworking of Woodstock molluscan fossils into the base of the Piney Point is common; 

double valves of Venericardia ascia Rogers and Rogers, 

1839, are reworked upward as much as 1.0 foot (0.3 m) 

into the Piney Point. As previously mentioned in the 

description of the Woodstock, a slightly glauconitic, 

pebbly, very clean sand crops out both on the Mattaponi River, below Reedy Mill (Locality 73, fig. 38), and 

on the Rappahannock River, at Greenlaw Wharf (Locality 54, fig. 33) and at Wilmont Wharf (Locality 70, fig. 

39), at the same interval as the Piney Point. This unit 

occurs at Wilmont Wharf only at the upriver end of the 

bluffs (upriver of the Wilmont fault of Ward and 

Blackwelder, 1980). There it may be seen below the 

steeply dipping beds of the Calvert Formation. Downstream, at a small waterfall in a ravine (Locality 81) 

where the Calvert beds resume their normal seaward 

dip, the unit in question is missing and the basal Calvert 

directly overlies the Woodstock Member. The patchy 

occurrence of the unknown bed in this area may be due 

to intermittent movement of the Wilmont fault (see 

Ward and Blackwelder, 1980).

It has not been paleontologically proven that this 

sand is an equivalent of the more open marine Piney 

Point, but the unit rests on known Woodstock and is 

overlain by the Calvert Formation. It appears to represent a barrier and back-barrier, very near shore sand 

and clay sequence, which may be a marginal-marine 

facies of either the Woodstock or the Piney Point. The 

Piney Point along the Pamunkey River is overlain, in 

places, by an unnamed upper Oligocene and lower 

Miocene unit, herein termed the Old Church Formation, 

and in other places by the Calvert Formation, where 

beds of the Old Church were not deposited or have been 

beveled off. The spotty exposure pattern of the Old 

Church suggests some tectonic control over its occurrence in addition to removal due to erosion. In the type 

well at Piney Point in St. Marys County, Md. (Locality 

80), the Piney Point Formation is underlain by the Nanjemoy and overlain by the Calvert. At Oak Grove in 

Westmoreland County, Va., somewhat farther inshore 

and updip, no middle Eocene beds were reported 

(Reinhardt and others, 1980; Gibson and others, 1980). 

A core taken at the Baltimore Gas and Electric atomic 

power plant site in Calvert County, Md. (Locality 82), 

contained typical Piney Point lithology and large 

fragments of Cubitostrea sellaeformis (Conrad, 1832) at 

the 330-foot (100.6-m) interval (approximately 210 feet 

(64 m) below sea level). There the Calvert directly 

overlies the Piney Point. Along the Patuxent River, the 

Calvert directly overlies the Woodstock in most places, 

but at a few localities (Locality 65, 66) a thin remnant
STRATIGRAPHY 47

FIGURE 36. Map showing localities where the Piney Point Formation is exposed or found in cores 

used in this study. Numbers refer to localities mentioned in the text.
48 STRATIGRAPHY AND MOLLUSKS OF PAMUNKEY GROUP AND OLD CHURCH FORMATION

76°

38°

37°

FIGURE 37. Map showing areal extent of the depositional basin 

within the Salisbury Embayment in which sediments of the Piney 

Point Formation were deposited during middle Eocene time. 

Dashed lines indicate area where boundary data are lacking. Map 

is based on outcrop and core data used in this report as well as on 

subsurface data from Brown and others (1972).

of the upper Oligocene and lower Miocene bed (the Old 

Church Formation(?)) is present. No outcrop of the 

Piney Point, however, is known from this area.

On the Pamunkey River, where the Old Church Formation overlies the Piney Point, the contact between 

the two units is sharp and is marked by a basal lag of 

shell, bone, and pebbles. At Horseshoe on the 

Pamunkey River, the type section of the Old Church 

Formation (Locality 83, fig. 40), burrows filled with 

Calvert sediment penetrate the whole thickness of the 

Old Church (3 feet (0.9 m)) and then spread horizontally along the Piney Point-Old Church contact. This 

lateral spreading was presumably due to the lag accumulation of oyster shells concentrated at the top of 

the Piney Point, which made further downward penetration difficult. Because the Piney Point was named from 

cuttings from a well in St. Marys County, Md. (Locality 80) and because the unit is so well exposed along the

Pamunkey River in Virginia, it is here proposed that 

the outcrops at Horseshoe (Locality 83) and 0.8 km 

upstream from Horseshoe (Locality 91) be considered 

the hypostratotype or reference sections.

The Piney Point on the Pamunkey includes (in ascending order) (A) basal, clayey, glauconitic sand (approximately 8.0 feet (2.4 m)), with a conspicuous line of concretions near the top of the bed, (B) a clayey, glauconitic 

sand (approximately 15.0 feet (4.6 m)), with an indurated 

oyster bed (approximately 5.0 feet (1.5 m)) at the top 

of the bed, and (C) a soft, nonfossiliferous, very burrowed, medium to coarse, glauconitic sand. This sequence is a composite of many small exposures from 

above the Rte. 360 bridge to below Retreat (Locality 

85). The indurated oyster bed at the top of Bed B clearly is lithologically similar to the beds seen upstream; 

it is present just below Piping Tree Ferry (Locality 84, 

fig. 41) where it can be seen only at low tide, dipping 

sharply downstream. There it is directly overlain by the 

Calvert, the Oligocene having been removed by erosion. 

Ascending, the next unit (C), the coarse glauconitic 

sand, is presumed to overlie the oyster beds and seems 

to be lithologically distinct from other beds of the Piney 

Point. It crops out only on the right bank of the 

Pamunkey just below Retreat at the mouth of Whiting 

Swamp (Locality 85, fig. 42). This bed is represented in 

a short core taken at Putney Mill, on the right bank of 

the Pamunkey River, in New Kent County (Locality 86). 

Preliminary dinoflagellate data from the core indicate 

a younger age for Bed C than for most of the Piney 

Point and a possible equivalence with the Gosport Sand 

of Alabama (late Claibornian) (L.E. Edwards, oral 

commun., 1984). This age has not been confirmed with 

samples from the single outcrop at Retreat (Locality 85, 

fig. 42). In spite of its distinct lithology, I prefer at this 

time to include this bed in the Piney Point.

The Piney Point outcrop and subsurface distribution 

patterns indicate a broad, shallow embayment, open 

eastwardly and northeastwardly to the paleo-Atlantic. 

To the south, the Norfolk Arch was a positive area and 

acted as a barrier affecting sedimentary regimes as well 

as faunal and floral assemblages. While sediment accumulations in the Carolinas and southward consisted 

principally of carbonates, north of the Norfolk Arch 

principally glauconite and quartz sands were deposited. 

Molluscan assemblages reflect a mild to warmtemperate marine environment in the Piney Point embayment, while tropical to subtropical seas dominated 

to the south.

The Piney Point may be confidently correlated with 

beds as far south as Texas. It is the equivalent of the 

Castle Hayne Formation (New Hanover and Comfort 

Members) in North Carolina, the Santee Limestone
STRATIGRAPHY 49

FIGURE 38. Mattaponi River, 1.3 miles (2.1 km) above the mouth of Maracossic Creek, King William County, Va. 

(Locality 73). Beds here may represent a marginal-marine facies of either the Woodstock Member of the Nanjemoy 

Formation or the Piney Point Formation.

(Moultrie Member) and McBean Formation in South 

Carolina, the Santee Limestone and McBean and Lisbon 

Formations in Georgia, the Lisbon Formation in 

Alabama, and the Cook Mountain Formation in Mississippi, Louisiana, and Texas. This correlation may be 

demonstrated with the molluscan assemblages even 

though they are incompletely known. The most characteristic taxon, Cubitostrea sellaeformis (Conrad, 

1832), is common in the middle Eocene (Claibornian) interval over this wide geographic area. This correlation 

and age assignment are in agreement with dinoflagellate 

data (L.E. Edwards, oral commun., 1984), ostracode data 

(J.E. Hazel, oral commun., 1984), planktic foraminifer 

data (P.F. Huddlestun, oral commun., 1984), and calcareous nannoplankton data (J.A. DiMarzio, oral commun., 1984).

Molluscan assemblages indicate a shallow-shelf, openmarine environment. Diversity among the mollusks is 

moderate; small bivalves are the most common taxa. 

Among the more common are the following (pi. 5):

Cubitostrea sellaeformis (Conrad, 1832) (figs. 4-6, 

8,9)

Anomia lisbonensis (Aldrich, 1886) (fig. 10)

Plicatula filamentosa Conrad, 1833 (fig. 7)

"Pecten" sp. (fig. 1)

"Pecten" sp. (fig. 2)

"Pecten" sp. (fig. 3)

Glycymeris lisbonensis Harris, 1919 (fig. 13)

Leda semen Lea, 1833 (fig. 12)

Leda coelatella Van Winkle, 1919 (fig. 11)

Venericardia rotunda Lea, 1833 (fig. 16)

Macrocallista perovata (Conrad, 1833)

Anapteris regalis Van Winkle, 1919 (fig. 14, 15)

Caestocorbula fossata (Meyer and Aldrich, 1886)

(fig. 21)

Corbula sp. (fig. 20) 

Turritella nasuta Gabb, 1860 (fig. 17) 

Dentalium sp. (fig. 18) 

Dentalium sp. (fig. 19)

Calcareous nannoplankton from the Piney Point examined by L.M. Bybell (oral commun., 1984) and J.A. 

DiMarzio (oral commun., 1984) indicate a placement of 

that unit within NP 16. Dinoflagellate data generated 

by L.E. Edwards (oral commun., 1984) also indicate an 

equivalency with NP 16 except for the possible presence 

of an NP 17 flora in Bed C of the Piney Point. That bed 

is the possible equivalent of the Gosport Sand in 

Alabama. Dinoflagellate diversity and composition also 

reflect a shallow-shelf, near-shore environment, with a 

fair amount of nutrients available.
50 STRATIGRAPHY AND MOLLUSKS OF PAMUNKEY GROUP AND OLD CHURCH FORMATION

FIGURE 39. Rappahannock River, 0.5 mile (0.8 km) below Wilmont Wharf, King George County, Va. (Locality 70). Slightly glauconitic, pebbly, quartz sand (A) overlain by diatomaceous silty sands of the Calvert Formation (B). The arrow 

marks the burrowed contact.

CHESAPEAKE GROUP

The term "Chesapeake Formation" was introduced 

by Barton (1891, p. 433) for a series of beds in southeastern Maryland and Virginia that consist of sands, 

clays, marls, diatomaceous clays, and shell fragments. 

Ball and Harris (1892) elevated the unit to group status 

and included all beds at the same horizon (or age) from 

Belaware to Florida. Shattuck (1902) subdivided the 

Chesapeake Group in Maryland into (in ascending order) 

the Calvert Formation, the Choptank Formation, and 

the St. Marys Formation. Shattuck (1904) greatly expanded this work and described the units, and their contained molluscan fauna, in detail. Clark and Miller (1906) 

expanded the definition of the Chesapeake Group by including the Yorktown Formation in Virginia. Clark and 

Miller (1912) included beds along the Chowan River in 

Bertie County, N.C., in the Yorktown Formation. Mansfield (1944) also included the Chowan River beds in the 

Yorktown. Blackwelder (1981) named those beds the 

Chowan River Formation, split the unit into two members, the Edenhouse Member (lower) and the Colerain 

Beach Member (upper), and included the new formation 

in the Chesapeake Group.

I recommend that the Old Church Formation be included in the Chesapeake Group. It is a calcareous, 

shelly sand that contains only small amounts of glauconite and is therefore easily separated from the underlying, very glauconitic beds of the Pamunkey Group. 

It is unclear whether Barton (1891) or Clark and Miller 

(1912) actually observed the bed herein termed the Old 

Church. Therefore, where they would have placed it is 

conjectural. If the correlation between the Old Church, 

at the type section on the Pamunkey River, with "zone" 

1 of Shattuck (1904) on the Patuxent River, Calvert and 

Prince Georges Counties, Md., is correct, then beds 

equivalent to the Old Church have already been included in the Chesapeake Group.

The following units constitute the Chesapeake Group:

Chowan River Formation

Colerain Beach Member . upper Pliocene

Edenhouse Member .... upper Pliocene 

Yorktown Formation

Moore House Member . upper Pliocene

Morgarts Beach Member . upper Pliocene

Rushmere Member ...... upper Pliocene

Sunken Meadow Member lower Pliocene 

Eastover Formation

Cobham Bay Member .... upper Miocene

Claremont Manor Member upper Miocene
STRATIGRAPHY 51

FIGURE 4QA. Pamunkey River at Horseshoe, Hanover County, Va. (Locality 83). Type locality (principal reference section) of the 

Old Church Formation. Hypostratotype or reference section for the Piney Point Formation. The Piney Point Formation (A) 

is overlain by the Old Church Formation (B), which is in turn overlain by the Calvert Formation (C). Arrows mark the contacts. 

The thin bed of mollusks in the Piney Point consists principally of Cubitostrea sellaeformis. The boulder-sized nodules near 

the base of the bluff originate in the Old Church Formation.

St. Marys Formation 

Windmill Point beds* . . . 

Little Cove Point beds* . . 

Conoy Member .....

Choptank Formation 

Boston Cb'ffs Member 

St. Leonard Member 

Drumcliff Member ......

Calvert Formation 

Calvert Beach Member . . . 

Plum Point Marl Member 

Fairhaven Member . .

Old Church Formation

upper middle Miocene 

upper middle Miocene 

upper middle Miocene

middle middle Miocene 

middle middle Miocene 

middle middle Miocene

lower middle Miocene

lower middle Miocene

lower and lower middle Miocene

upper Oligocene and lower Miocene

""Informal name used by Blackwelder and Ward (1976).

OLD CHURCH FORMATION

The presence of possible Oligocene sediments in 

Virginia was first pointed out by Ward and others (1978, 

p. 13), who correlated them with Chickasawhayan 

beds in North Carolina assigned to the River Bend

Formation. The upper Oligocene or lower Miocene beds 

in the outcrop area on the Pamunkey River are herein 

termed the Old Church Formation. The unit takes its 

name from the nearby village of Old Church, Hanover 

County, Va. The unit consists of grayish-olive (10 Y 4/2), 

clayey, quartz sands containing small amounts of reworked glauconite. CaCO3 content is high owing to shell 

fragments as well as to the large number of foraminifers 

and ostracodes, both primary and reworked, within the 

unit. Aragonitic molluscan fossils are commonly 

leached, leaving molds and casts. Calcitic mollusks are 

common and consist of small pectens and oysters. The 

formation contains irregular indurated masses that occur along the river as large, boulder-sized concretions. 

The Old Church unconformably overlies the Piney Point 

Formation and is unconformably overlain by the 

Calvert Formation. In Virginia the Old Church is known 

in natural surface exposures only from the Pamunkey 

River, where it crops out from above Horseshoe (Locality 83, fig. 40) to below the mouth of Matadequin Creek 

(Locality 87; see fig. 43 for locality map). The exposure 

on the right bank of the Pamunkey at Horseshoe is
52 STRATIGRAPHY AND MOLLUSKS OF PAMUNKEY GROUP AND OLD CHURCH FORMATION

FIGURE 405. Pamunkey River at Horseshoe, Hanover County, Va. (Locality 83). Type locality (principal reference section) of the 

Old Church Formation. Blake W. Blackwelder (Tenneco Co., Houston, Tex.) has his pick on the contact between the Old Church 

Formation and the overlying Calvert Formation.

designated the type section of the Old Church (Locality 83). The unit is 3 feet thick at the type section, but 

its thickness varies from locality to locality because of 

beveling by the sea during the Calvert transgression. 

A bed that occurs on the Patuxent River in Maryland 

(Localities 65, 66) and that lies between the Woodstock 

Member of the Nanjemoy Formation and "zone" 2 of 

the Calvert Formation may be equivalent to, and belong 

in, the Old Church Formation. It was included by Shattuck (1904) in the original definition of the Calvert Formation and called "zone" 1. Along the Patuxent River 

in Maryland, it unconformably overlies the Woodstock 

Member and unconformably underlies "zone" 2 of the 

Calvert Formation at the abandoned glauconite mine 

("Kaylorite" pit) (Locality 65, fig. 44) and below White 

Landing on the right bank (Locality 66, fig. 45). If this 

bed proves to be the equivalent of the Old Church, it 

is here recommended that the original concept of the 

Calvert Formation be amended and restricted to include 

only "zones" 2-15 of Shattuck. The only other known 

exposure of the Old Church Formation was at the 

Warren Brothers sand and gravel borrow pits on the

Chickahominy River floodplain below Bottoms Bridge 

(Locality 88). There the Old Church immediately 

underlies Pleistocene(?) gravels that were mined from 

1975 to 1977. Stripping caused the Old Church to be 

exposed briefly in the bottom of the pits, which, when 

depleted, were allowed to flood. The mine ceased operations in 1978, and no exposure of the Old Church remains. The upper and lower contacts of the unit were 

obscured at the pit, but a nearby gulley cutting down 

to the floodplain through the Chickahominy River 

escarpment exposed a thick section including the Claremont Manor and Cobham Bay Members of the Eastover 

Formation as well as the Rushmere Member of the 

Yorktown Formation, all presumably overlying the Old 

Church.

It seems clear, on the basis of stratigraphic position 

and age, that the unit traced in the subsurface of 

Maryland, Delaware, and New Jersey by Olsson and 

others (1980) is equivalent to the Old Church Formation, even though they termed it the "Piney Point." Except for the glauconite percentages, the description by 

Olsson and others (1980) fits well with the Old Church
STRATIGRAPHY 53

FIGURE 41. Pamunkey River at Piping Tree Ferry, King William County, Va. (Locality 84). Thin-bedded, seaward-dipping, 

indurated, glauconitic sands of the Piney Point Formation are exposed only at low tide. The beds are crowded with oysters 

(Cubitostrea sellaeformis), from which the cement is probably derived.

beds that crop out on the Pamunkey River. Two reasons 

may account for this difference. Their study indicated 

that much of the glauconite was reworked from the 

underlying, more glauconitic Eocene beds. A further explanation may be in the lower percentages of glauconite 

with increasing proximity to paleoshorelines, as shown 

throughout the Paleocene and Eocene beds in the 

Salisbury Embayment. The Brightseat, Aquia, Nanjemoy, and Piney Point Formations all increase in 

glauconite content in a seaward direction.

Further evidence for the presence of a bed equivalent 

to the outcropping Old Church is obtained from a study 

on fossils found in deep wells on the Atlantic Coastal 

Plain by H.G. Richards (1947). In that work, Richards 

figured and described a small pecten, "Pecten" seabeensis Richards, 1947, at a depth of 380 feet (115.8 m) at 

Camp Peary, York County, Va. The type specimen has 

been examined and appears identical with specimens 

from the type section of the Old Church (Locality 83) 

on the Pamunkey River as well as with specimens from 

the Warren Brothers pit on the Chickahominy River 

(Locality 88).

At another locality, Gravatts Millpond on Mill Pond

Creek in King William County, Va. (Locality 89), beds 

probably equivalent to the Old Church are exposed. 

There, large indurated blocks of a phosphatic, conglomeratic sandstone overlie the fine, micaceous, silty 

sand of the Woodstock Member and are overlain by the 

clayey, olive-brown (5 Y 4/4) sands of the basal Calvert 

Formation. These blocks and some of the phosphate 

pebbles, cobbles, worn bone, and teeth are believed to 

be residuum from the erosion of the Old Church. Among 

the bone fragments found on this contact was a periotic 

from an odontocete whale that was certainly pre-Calvert 

and was probably early Miocene or very late Oligocene 

in age.

The Old Church Formation thins a short distance 

upstream from Horseshoe (Locality 83) and is less than 

a foot thick 0.30 mile (0.48 km) above Horseshoe (Locality 90).

The basinal outline of the Old Church is, at present, 

only partially known (fig. 46). If the correlation of the 

type Old Church with beds on the Patuxent River in 

Maryland, beds in the subsurface at Camp Peary, and 

beds mapped as "Piney Point" by Olsson and others 

(1980) is correct, then the basin configuration covers
54 STRATIGRAPHY AND MOLLUSKS OF PAMUNKEY GROUP AND OLD CHURCH FORMATION

FIGURE 42. Pamunkey River below Retreat, Hanover County, Va. (Locality 85). The very burrowed, medium to coarse 

glauconitic sand of unit C of the Piney Point Formation crops out to a height of 9.0 feet (2.7 m). Burrows from an 

overlying, very weathered, mold and cast, calcareous sandstone may be seen as deep as the arrow indicates. The 

degree of weathering of this overlying unit has prevented the determination of its exact age.

parts of New Jersey, Delaware, Maryland, and Virginia. 

Apparently the Norfolk Arch was, again, a high area 

separating the Old Church embayment from its counterpart in North Carolina. This barrier, or a seaward connection somewhat farther north, probably served to 

divert the tropical currents that dominated in North 

Carolina at that time. The result is a temperate, lowdiversity, molluscan assemblage strikingly different 

from that south of the Norfolk Arch but sharing a few 

of the same taxa.

Because of basic, though minimal, differences of opinion as to the age of Old Church Formation, the precise 

correlation of that unit to equivalent beds to the south 

is not yet clear. The consensus of paleontologic data, 

including mollusks, ostracodes, foraminifers, pollen, and 

dinoflagellates, brackets the unit in the interval embracing the late Oligocene and early Miocene. That period 

was a time of widespread climatic change and abrupt, 

short-term, small-scale, marine pulses. To the south in 

the Albemarle Embayment (fig. 2) in central and northeast North Carolina, this resulted in the deposition of 

the River Bend Formation (late Oligocene-Chickasawhayan) and the Belgrade Formation (late Oligoceneearly Miocene-Tampan).

Molluscan assemblages of the Old Church Formation 

indicate a close affinity with both the upper River Bend 

and Belgrade Formations, though they are less diverse 

than assemblages in those units. The following taxa are 

commonly found in the Old Church (pi. 6):

Mercenaria gardnerae Kellum, 1926 (fig. 8)

Anomia ruffini Conrad, 1843 (fig. 4)

"Pecten" seabeensis Richards, 1947 (fig. 6)

"Pecten" sp. (fig. 5)

Lucina sp. (fig. 9, 10)

Plicatula sp. (fig. 14, 15)

Epitonium sp.

Panopea sp. (fig. 13)

Cyclocardia sp. (fig. 16)

Astarte sp.

Pycnodonte sp. (fig. 1, 2, 3)

Isognomon sp. (fig. 11)

"Cardium" sp.

Bicorbula idonea (Conrad, 1833) (fig. 7)

Macrocallista sp.

Diadora sp.

Ecphora sp. (fig. 12)

Trophon sp.

Calyptraea sp.

Nonmolluscan macrofossils include solitary corals and 

two barnacles a hesperabalanid and a balanid. Aragonitic mollusks occur only as molds and were identified 

with the aid of latex casts. Calcitic mollusks are abundant and well preserved. Mercenaria gardnerae Kellum, 

1926, made its first appearance in the upper part of the 

River Bend Formation but is also abundant in the Belgrade. It closely resembles Venus marionana Mansfield, 

1937, from the Tampa Formation of Florida and is 

the first known occurrence of the genus Mercenaria.
STRATIGRAPHY 55

FIGURE 43. Map showing localities where the Old Church Formation is exposed or found in cores 

used in this study. Numbers refer to localities mentioned in the text.
56 STRATIGRAPHY AND MOLLUSKS OF PAMUNKEY GROUP AND OLD CHURCH FORMATION

j «

FIGURE 44. Patuxent River at the "Kaylorite" pit at the termination of Landing Road, Calvert County, Md. (Locality 65). The contact of the Woodstock Member of the Nanjemoy Formation (A) with the Old Church Formation(?) 

(B) occurs at the top of the pen. Burrows on the upper surface of the Old Church(?) (zone 1 of Shattuck, 1904) are 

filled with white sand from the overlying basal sands of the Fairhaven Member of the Calvert Formation (zone 2 

of Shattuck, 1904).

Anomia ruffini Conrad, 1843 (=Anomia mcgeei Clark, 

1895), was collected on Edmund Ruffin's property along 

the Pamunkey River and is the probable senior 

synonym of Anomia taylorensis Mansfield, 1940, from 

the Chickasawhay of Alabama and Mississippi and 

Anomia onslowensis Richards, 1943, from the River 

Bend and Belgrade Formations. "Pecten" seabeensis 

Richards, 1947, is known only from the Old Church, but 

"Pecten" sp. is also present in the upper beds of the 

Ashley Formation of South Carolina. The Lucina sp. 

that is so common in the Old Church is also present in 

large numbers in the Ashley Formation in South Carolina and is probably the taxon reported from "zone" 1 

of the Calvert Formation by Shattuck (1904) to be 

"Phacoides contractus" The species may, in fact, be 

more closely related to Phacoides hemandoensis 

Mansfield, 1937, from the Suwannee Limestone of 

Florida. The Pycnodonte sp. is similar to an oyster from 

the lower Miocene of Florida that Ball named Ostrea 

podagrina Ball, 1896. That taxon, or one very similar, 

is common in the Ashley in South Carolina, the River

Bend in North Carolina, and the Old Church in Virginia. 

The presence of the genus Isognomon is revealed only 

by exterior molds (xenomorphism) of that taxon on the 

ventral valves of a few specimens of Pycnodonte. 

Isognomon had been absent alon^ the Atlantic coast 

of North America since the Late Cretaceous. The genus 

is present, but not common, in the Haywood Landing 

Member of the Belgrade Formation. Both Bicorbula and 

Macrocallista are known from the Belgrade Formation. 

TheEcphora sp. is known also from the Haywood Landing in North Carolina. Molluscan evidence, therefore, 

indicates a correlation with the Belgrade Formation in 

North Carolina and brackets the age of the Old Church 

as late Oligocene or early Miocene. Further work on the 

European type sections is necessary before a more 

definite age determination is possible.

This same conclusion is in agreement with results 

from workers on the various microfossil groups. Ostracode data indicates a late Oligocene age assignment and 

equivalency with the Ashley Formation of the Cooper 

Group (J.E. Hazel, oral commun., 1984). Reworking is
STRATIGRAPHY 57

FIGURE 45. Patuxent River at White Landing, Prince Georges County, Md. 

(Locality 66). B.W. Blackwelder (Tenneco Co., Houston, Tex.) is pointing at 

the contact between the Woodstock Member of the Nanjemoy Formation (A) 

and the Old Church Formation!?) (B). The Old Church(?) (zone 1 of Shattuck, 

1904) is overlain by the basal sands of the Fairhaven Member of the Calvert 

Formation (C) (zone 2 of Shattuck, 1904). An arrow marks the contact be 

tween the Old Church(?) and the Fairhaven.

a problem with microfossil evaluation, as demonstrated 

by R.Z. Poore (written commun., 1984) for planktic 

foraminifers. In a sample from the type locality (Locality 83) of the Old Church, the following planktics were 

identified by R.Z. Poore: Globigerina praebulloides 

Blow, G. ciperoensis Boli, G. juvenilis Boli, and 

Morozovella aequa (Cushman and Renz). TheM aequa 

(Cushman and Renz) was reworked from the Paleocene 

(Aquia Formation) or lower Eocene (Nanjemoy Formation), but the other taxa indicate a late Oligocene or 

early Miocene age. A sample from the Old Church 

Formation at the Warren Brothers pit on the Chickahominy (Locality 89) included the following planktics: 

Globigerina praebulloides Blow, G. ciperoensis Boli, 

G. angustiumbilicata Boli, and G. sp. This assemblage 

also brackets the unit within the late Oligocene and 

early Miocene. Pollen samples from the type section at 

Horseshoe (Locality 83) examined by N.O. Frederiksen 

(written commun., 1984) contained the following taxa:

Quercus sp.

Carya sp.

Myrica sp.

Liquidambar sp.

Boehlensispollis hohlii Krutzsch, 1962

Tetracolporopollenites lesquereuxianus (Traverse,

1955) Frederiksen, 1980 

Pinus sp. 

Momipites spackmanianus (Traverse, 1955)

Nichols, 1973 

Momipites annulatus Frederiksen and Christopher,

1978

Milfordia sp. indet. 

Ulmipollenites undulosus Wolff, 1934 

Ulmipollenites krempii (Anderson, 1960)

Frederiksen, 1979 

Tilia sp.

Frederiksen concluded that the assemblage was more 

suggestive of late Oligocene than early Miocene but that 

the evidence was somewhat inconclusive.
58 STRATIGRAPHY AND MOLLUSKS OF PAMUNKEY GROUP AND OLD CHURCH FORMATION

76°

38°

37°

DELAWARE ~* 

MARYLAND 3:.'

FIGURE 46. Map showing areal extent of the depositional basin 

within the Salisbury Embayment in which sediments of the Old 

Church Formation were deposited during the latest Oligocene or 

earliest Miocene. Dashed lines indicate area where boundary data 

are lacking. Map is based on outcrop and core data used in this 

report as well as on subsurface data from Brown and others (1972).

SUMMARY OF LOWER TERTIARY

STRATIGRAPHY AND 

ONLAP-OFFLAP RECORD

The Salisbury Embayment and the entire Atlantic 

Coastal Plain have had a complex history. In contrast 

to the implications of the term "passive margin," this 

was a structurally dynamic area whose sedimentary 

history clearly shows the effects of structural movement as well as of global sea-level events. To identify 

and eliminate local tectonic "noise" and detect actual 

global sea-level changes, one must compare the detailed 

stratigraphic records of several embayments. In figure 

47, the sea-level curves of three principal Atlantic 

Coastal Plain basins (Salisbury Embayment, Albemarle 

Embayment, and Charleston Embayment) are plotted.

A fourth curve for the Atlantic Coastal Plain combines 

the data obtained in the three basins and attempts to 

represent the actual record of sea-level fluctuations. 

These curves are plotted against the cycles and supercycles of Vail and Mitchum (1979). The curves are based 

on my interpretations of onshore outcrop and subsurface data. I have made no attempt to plot sea-level 

changes beyond the present coastline.

PALEOCENE

The following trends may be observed by examining 

the onlap relationships of formations in the three basins. 

In the middle early Paleocene, there is agreement for 

a moderately strong marine pulse. This pulse is recorded 

by the Brightseat Formation in the Salisbury Embayment, the Jericho Run Member of the Beaufort Formation in the Albemarle Embayment, and the Black Mingo 

Formation in the Charleston Embayment. Another 

strong onlap sequence occurred during the late 

Paleocene and lasted almost that entire period. In the 

Salisbury Embayment, beds associated with the event 

are included in the Aquia Formation. There are at least 

two recognizable pulses, represented by the Piscataway 

and Paspotansa Members, involved in that sequence, 

however. A final small transgression, probably only in 

the Salisbury Embayment, resulted in the deposition 

of the Marlboro Clay. In the Albemarle Embayment, 

late Paleocene beds include the Beaufort Formation, 

while in the Charleston Embayment they are placed in 

the Black Mingo Formation. More detailed work in 

these latter two basins will probably reveal a series of 

small pulses within the major units.

EOCENE

During the early Eocene a moderately strong transgression occurred in the Salisbury Embayment (Potapaco Member of the Nanjemoy Formation), Albemarle 

Embayment (unnamed, subsurface only), and Charleston Embayment (Fishburne Formation, subsurface), 

again indicating a general sea-level rise. In the late early 

Eocene a second pulse occurred, which is reflected by 

sedimentation in the Salisbury Embayment (Woodstock 

Member of the Nanjemoy Formation) but not in North 

or South Carolina. There is evidence of a pulse in the 

stratigraphic sequence at Hatchetigbee Bluff on the 

Tombigbee River, Ala. If indeed the resulting marine 

bed is correlative with beds of the Woodstock, then the 

pulse may be deemed to have been more than just local 

subsidence. From the Atlantic record alone, however,
LOCALITIES AND MEASURED SECTIONS 59

it appears to be a result of individual basin subsidence 

in the Salisbury Embayment.

The most extensive transgression during the Tertiary 

occurred in the middle Eocene. In Virginia it took place 

during the middle middle Eocene and resulted in the 

deposition of the Piney Point Formation. To the south 

this transgression is represented by carbonate beds: 

Castle Hayne Formation in North Carolina, Moultrie 

Member of the Santee Limestone and McBean Formation in South Carolina and Georgia, and Lisbon Formation in Georgia and Alabama. Beds associated with this 

event are present in all areas of the Gulf Coastal Plain. 

It is clear, then, that these deposits record a global sealevel rise. At least five small pulses are reflected in the 

middle Eocene sequence, but they are plotted as one in 

figure 47 due to the lack of correlative data. Each apparently was of short duration but was significant 

enough, when sufficient stratigraphic refinement is accomplished, to correlate from basin to basin. During the 

late middle Eocene, a final sharp pulse resulted in a 

relatively thin series of beds in most of the basins from 

Alabama to Virginia. This transgression resulted in 

beds of the Gosport Sand in Alabama, the Cross 

Member of the Santee Limestone in South Carolina, the 

Spring Garden Member of the Castle Hayne Formation 

in North Carolina, and possibly Bed C of the Piney Point 

Formation in Virginia. The unconformity between beds 

associated with this onlap and those of the middle middle Eocene is well developed and sharp, but molluscan 

fossil evidence indicates that this break represents a 

relatively brief period of time. The geographically 

widespread stratigraphic record suggests that this 

event was global in nature. During the late Eocene, a 

small-scale transgression took place in South Carolina 

(Cooper Group, Harleyville and Parkers Ferry Formations) and Virginia (Chickahominy Formation of 

Cushman and Cederstrom, 1945). This small thickness 

contrasts with the thick stratigraphic sequence 

deposited in the Gulf area at that time. That record suggests a high sea-level stand, but the meager upper 

Eocene record in the Atlantic basins indicates a general 

sea-level lowering, unless most of that area was tectonically emergent.

OLIGOCENE

During the early Oligocene, a thick sequence of beds 

was deposited in the Gulf, while in the Atlantic region 

there are no confirmed units of that age. In the late 

Oligocene, there is agreement as to a relative high stand, 

which resulted in the deposition of beds in the 

Charleston Embayment (Ashley Formation of the 

Cooper Group), Albemarle Embayment (River Bend

Formation), and the Gulf. During the very late 

Oligocene or very early Miocene a brief, small-scale, high 

stand left a sedimentary record in the Salisbury Embayment (Old Church Formation), Albemarle Embayment (Haywood Landing Member of the Belgrade Formation), Charleston Embayment (Edisto Formation), 

and Florida (Tampa Formation). In spite of the thinness 

of these deposits, their wide occurrence is good evidence 

for a global sea-level rise or the submergence of most 

of the Atlantic Coastal Plain.

LOCALITIES AND MEASURED SECTIONS

1. (USGS Locality 26330) Right bank of Aquia Creek, 0.5 mile 

(0.8 km) above Thorney Point, Stafford County, Va., Widewater 

7.5-min quadrangle (see figs. 5A, 10)

Ft (m) 

Sloped and covered by vegetation .............. 3.0 (0.9)

Aquia Formation (Piscataway Member)

Sand, grayish-orange (10 YR 7/4), silty, 

fine, very glauconitic, poorly sorted, 

weathered, and leached; some molds and 

casts ................................. 9.0 (2.7)

 Unconformity 

Brightseat Formation

Sand, dark-olive-black (5 Y 2/1), micaceous, clayey, silty, very fine, well sorted 

in the lower half, weathered to grayish 

orange in the upper half; an 8-inch 

(20-cm) indurated capping present at 

the lower end of the exposure but 

beveled off at the upper end of the 

exposure .............................. 7.0 (2.1)

 Unconformity 

Patapsco Formation (Lower Cretaceous)

Sand, well consolidated, clayey, silty, 

light-blue-gray (5 B 7/1); very irregular, 

burrowed and eroded upper surface ..... 0-1.0 (0-0.3) 

 Sea Level 

2. (USGS Locality 26331) Right bank of the Rappahannock River, 

1.85 miles (2.98 km) east of Greenfield, Spotsylvania County, 

Va., Guinea 7.5-min quadrangle (see fig. 5B)

Ft (m) 

Covered by vegetation ...................... 10.0 (3.0)

Brightseat Formation (lower Paleocene)

Sand, weathered, light-olive-gray (5 Y 5/1), 

micaceous, silty, very well sorted, very 

fine; small blades of gypsum common; 

trace amounts of glauconite; calcareous 

material leached ........................ 8.0 (2.4)

 Unconformity 

Patapsco Formation (Lower Cretaceous)

Sandstone, tan, coarse; burrowed upper 

surface ............................... 1.5 (0.4)

Silt, well-consolidated, blue-gray ............ 6.0 (1.8)

Sand, crossbedded, fine, well-sorted ........ 10.0 (3.0)

 Sea Level 
60 STRATIGRAPHY AND MOLLUSKS OF PAMUNKEY GROUP AND OLD CHURCH FORMATION

EPOCHS

Cycles of Relative Changes 

of Sea Level Based on Coastal Onlap

(After Vail and Mitchum, 1979)

Atlantic Coastal Plain 

Sea Level Changes

Salisbury Embayment 

Sea Level Changes

Present Sea Level

-« Present 

Sea Level

Tb

TP2 2 

TP2 1

FIGURE 47. Sea-level fluctuations in the Salisbury, Albemarle, and Charleston Embayments are plotted against cycles and supercycles by Vail and Mitchum (1979). Data from the three basins are combined to approximate global sea-level events as seen 

along the Atlantic coastal margin. The marine climate curve represents conditions in the Salisbury Embayment and is based 

on data from fossil molluscan assemblages.
LOCALITIES AND MEASURED SECTIONS 61

Albemarle Embayment 

Sea Level Changes

Present Sea Level

Y -« Rising Falling

Charleston Embayment 

Sea Level Changes

Present Sea Level

Y 

-« Rising Falling i

Marine Climatic 

Fluctuations

Present

Y 

"Warmer Cooler*

EPOCHS

a ? 

« 9

FIGURE 47. Continued.
62 STRATIGRAPHY AND MOLLUSKS OF PAMUNKEY GROUP AND OLD CHURCH FORMATION

3. (USGS Locality 26332) Right bank of the Potomac River, 1.5 

miles (2.4 km) below the mouth of Aquia Creek and 

Youbedam Landing, Stafford County, Va., Passapatanzy 

7.5-min quadrangle. Principal reference section (lectostratotype locality) of the Aquia Formation and the Piscataway and 

Paspotansa Members (see fig. 16)

Ft (m) 

Covered .................................... 5.0 (1.5)

Nanjemoy Formation

Sand, yellowish-gray (5 Y 8/1), weathered, 

moderately glauconitic, fine .............. 5.0 (1.5)

Marlboro Clay

Clay, light-gray (N 8), weathered; where this 

bed is absent there is a distinct line 

between the Aquia and the overlying 

bed .............................. 0.0-0.75 (0.0-0.23)

Aquia Formation (Paspotansa Member)

Sand, weathered, grayish-orange 

(10 YR 7/4), glauconitic, fine; contains 

large numbers of Turritella in lenses, 

bands, and large indurated masses ....... 35.0 (10.7)

Sand, olive-black (5 Y 2/1), fine, wellsorted, silty; scattered poorly preserved 

Turritella ............................ 25.0 (7.6)

Sand, olive-black (5 Y 2/1), glauconitic, 

very fine, well sorted; many Turritella 

("zone" 6 of Clark and Martin, 

1901) ................................. 1.5 (0.5)

 Unconformity 

Aquia Formation (Piscataway Member)

Sandstone, light-olive-gray (5 Y 6/1), indurated, glauconitic; many molds and 

casts, some siliceous replacements 

("zone" 5 of Clark and Martin, 

1901) ................................. 2.0 (0.6)

Sand, olive-gray (5 Y 4/1), very glauconitic, silty, clayey, very shelly, poorly 

sorted; packed with large bivalves and 

Turritella, appears light-olive-gray 

(5 Y 6/1) from a distance due to large 

numbers of mollusks present; preservation poor to moderate; irregularly 

indurated in beds where Ostrea are 

concentrated .......................... 12.0 (3.7)

 Sea LevelThe section given by Clark (1896b, p. 40) for the bluff at Aquia Creek 

and by Clark and Martin (1901, p. 69, Sect. Ill) at the same locality 

are clearly composite sections giving the maximum thicknesses of the 

units observed between Aquia and Potomac Creek. It is evident that 

the measurements for the thickness of the Piscataway were taken at 

the northwest end of the bluffs, while the measurements of the bed 

they placed in the Pleistocene was apparently taken at the southeast 

end of the bluffs. It has been found that the "light-yellow" sand they 

placed in the Pleistocene is weathered Nanjemoy. The "white clay" 

at the base of the sand is Marlboro Clay. The upper 10 feet of the 

Paspotansa that Clark and Martin call "Zone 10" lies below the 

Marlboro Clay and is weathered Paspotansa (not Nanjemoy as shown 

on their Plate VI, Section III). Because of the composite nature of 

dark's (1896b) and Clark and Martin's (1901) sections, it is advisable 

to choose a specific locality as a principal reference section (lectostratotype). The section chosen has, by necessity, a smaller thickness 

of both Piscataway and Nanjemoy, but all beds are present.

4. (USGS Locality 26333) Right bank of the Rappahannock River, 

0.15 mile (0.2 km) below the mouth of Snow Creek, Caroline 

County, Va., Rappahannock Academy 7.5-min quadrangle

Ft (m) 

Covered with vegetation ..................... 10.0 (3.0)

Aquia Formation (Piscataway Member)

Sand, olive-gray (5 Y 4/1), clayey, poorly 

sorted, glauconitic; many bivalves, moderate to good preservation ............... 5.0 (1.5)

 Sea Level 

5. (USGS Locality 26334) Blantons Pond, 1.2 miles (1.9 km) west of 

Milford, Caroline County, Va., Woodford 7.5-min quadrangle 

Core taken by R.B. Mixon, U.S. Geological Survey, Reston, Va.

6. (USGS Locality 26335) Left bank of the Pamunkey River, 0.65 

mile (1.05 km) below the confluence of the North Anna and 

South Anna Rivers, Caroline County, Va., Ashland 7.5-min 

quadrangle

Ft (m) 

Sloped and covered ......................... 10.0 (3.0)

Aquia Formation (Piscataway Member)

Sand, grayish-orange (10 YR 7/4), silty, 

very weathered; very poorly preserved 

bivalves ............................... 3.0 (0.9)

Cobbles, in matrix of sand and gravel; 

believed to be reworked into base of 

Aquia ................................ 1.5 (0.5)

 Unconformity 

Patuxent Formation (Lower Cretaceous)

Clay, greenish-blue, mixed with gravel, 

sand, and cobbles ...................... 3.0 (0.9)

 Water Level 

7. (USGS Locality 26336) Right bank of the Pamunkey River, 

1.1 miles (1.8 km) (straightline) southeast of the confluence 

of the North Anna and South Anna Rivers, Hanover 

County, Va., Ashland 7.5-min quadrangle. 0.8 mile (1.3 km) 

downriver of Locality 6

Ft (m) 

Sloped and covered .......................... 3.0 (0.9)

Aquia Formation (Piscataway Member)

Sand, same as below but weathered to 

grayish-orange (5 YR 7/4); many mollusks 

including Turritella, Ostrea, Dosiniopsis, 

Pitar ................................. 6.0 (1.8)

Sand, olive-gray (5 Y 5/1), clayey, poorly 

sorted, glauconitic and quartzose; many 

moderately to poorly preserved large bivalves including Cucullaea, Crassatellites, and Ostrea ....................... 3.0 (1.9)

Cobbles, basal conglomerate ................... 2.5 (0.8)

 Water Level 
LOCALITIES AND MEASURED SECTIONS 63

8. (USGS Locality 26337) Right bank of the Pamunkey River, 0.5 

mile (0.8 km) east of Wickham Crossing, Hanover County, 

Va., Ashland 7.5-min quadrangle (see figs. 9, 11)

Ft (m) 

Pleistocene (undiff.)

Sand and gravel, orange .................. 6.0 (1.8)

 UnconformityFormation (?)

Sand, reworked(?), weathered to grayishorange, glauconitic, poorly sorted ......... 4.0 (1.2)

Aquia Formation (Paspotansa Member)

Sand, olive-black (5 Y 2/1), glauconitic, silty, 

micaceous, very fine, very well sorted ..... 3.0 (0.9)

 Unconformity 

Aquia Formation (Piscataway Member)

Sand, olive-gray (5 Y 4/1), clayey, fine,

glauconitic, poorly sorted, many bivalves,

especially Crassatella ................... 3.0 (0.9)

Sand, olive-gray (5 Y 4/1), clayey, fine, glauconitic, poorly sorted; many Turritella ..... 3.5 (1.1)

Sand, olive-gray (5 Y 4/1), clayey, fine,

glauconitic, poorly sorted; many small

bivalves and Ostrea ..................... 2.5 (0.8)

Sand, olive-gray (5 Y 4/1), clayey, fine,

glauconitic, poorly sorted; many large

bivalves ............................... 3.0 (0.9)

Cobbles, basal conglomerate ............... 1.5 (0.5)

 Unconformity 

Patapsco Formation (Lower Cretaceous)

Clay, blue-green (covered at high water 

level .................................. 1.0 (0.3)

Sand, blue, medium, cross-bedded (covered at normal water level) ............... 1.0 (0.3)

 Water Level 

9. (USGS Locality 24338) Right bank of the Pamunkey River, 

1.6 miles (2.6 km) east of Wickham Crossing, Hanover 

County, Va., Ashland 7.5-min quadrangle

Ft (m) 

Sloped and covered ......................... 10.0 (3.0)

Eastover Formation (Claremont Manor Member) 

Sand, tan and orange, weathered, fine, 

burrowed .............................. 5.0 (1.5)

Sand, light-grayish-yellow, fine ............. 3.0 (0.9)

Sand, yellowish-brown, poorly sorted, clayey . . 4.0 (1.2)

 Unconformity 

Calvert Formation

Clay, olive-brown (5 Y 4/4), silty, sandy; 

some phosphate along contact ............ 1.5 (0.5)

 Unconformity 

Aquia Formation (Paspotansa Member)

Sand, very fine, well-sorted, micaceous, silty, 

glauconitic, olive-black (5 Y 2/1) where 

fresh in the lower portions, light-olivegray (5 Y 6/1) where weathered above, indurated nodules at 15 feet (4.5 m). Burrows in top of unit contain sediments from 

the Marlboro Clay and Bed A of the Potapaco Member. These two units were present but were beveled off here leaving only 

their sediments filling burrows. 300 feet 

(91.4 m) downstream at Locality 33 both 

of these units are exposed; Turritella common throughout but concentrated in beds 

(molds only) .......................... 30.0 (9.1)

 Water Level 

10. (USGS Locality 26339) Right bank of the James River, 1.0 

mile (1.6 km) above the mouth of the Turkey Island Cutoff, 

just above Fishpond, Chesterfield County, Va., Hopewell 

7.5-min quadrangle (see fig. 12)

Ft (m) 

Covered .................................... 2.0 (0.6)

Pleistocene(?) 

(?)Formation

Clay, white, sandy, weathered ............. 14.0 (4.3)

 Unconformity? 

(?)Formation

Conglomerate, weathered, grayish-yellow, 

sand, gravel, cobbles, some reworked glauconitic sand ........................... 2.5 (0.8)

 Unconformity 

Aquia Formation (Piscataway Member)

Sand, olive-gray (5 Y 4/1, medium to fine, 

clayey, glauconitic, poorly sorted; contains 

numerous mollusks, moderately preserved 

(Crassatellites, Turritella, Ostrea) .......... 2.0 (0.6)

Cobbles, sand and gravel conglomerate; glauconitic, contains shark teeth ............ 1.0 (0.3)

 Sea Level11. (USGS Locality 26340) Bull Bluff, right bank of the Potomac 

River at the mouth of Potomac Creek, King George County, 

Va., Passapatanzy 7.5-min quadrangle (see fig. 144). Section 

has been modified from Clark and Martin (1901) because 

of the present slumping at the locality.

Ft (m) 

Covered

Sand, yellow and orange ................. 15.0 (4.6)

Calvert Formation (Fairhaven Member)

Clay, silty, weathered ..................... 5.0 (1.5)

 Unconformity 

Nanjemoy Formation (Potapaco Member)

Sand, clayey, glauconitic ................. 35.0 (10.7)

Sand, clayey, glauconitic; thin beds of 

Venericardia (Bed B of this report) ....... 16.0 (4.9)

Sand, clayey, glauconitic; scattered molds 

and casts (may be Bed A of this report) . . 25.0 (7.6)

 UnconformityMar Iboro Clay

Clay, light-gray (N 7) ..................... 0.5 (0.15)

Aquia Formation (Paspotansa Member)

Sand, weathered, yellowish-gray, glauconitic,

fine, irregularly indurated, many Turritella 12.0 (3.7) 

Sand, olive-black (5 Y 2/1), fresh near water 

level, glauconitic, fine; Turritella 

numerous in several beds; Ostrea sinuosa, 

Crassatellites alaeformis, and Cucullaea 

gigantea common ..................... 25.0 (7.6)

 Sea Level12. (USGS Locality 26341) Right bank of the Potomac River, 0.1 mile 

(0.16 km) below the mouth of Passapatanzy Creek, King George 

County, Va., Passapatanzy 7.5-min quadrangle (see fig. 145)

Ft (m) 

Covered

Sand, tan, gravelly ....................... 8.0 (2.4)

 Unconformity 

Aquia Formation (Paspotansa Member)

Sand, olive-black (5 Y 2/1), silty, fine, micaceous; many Turritella, small gastropods 

common ............................... 6.0 (1.8)

 Sea Level 
64 STRATIGRAPHY AND MOLLUSKS OF PAMUNKEY GROUP AND OLD CHURCH FORMATION

13. (USGS Locality 26342) Right bank of the Potomac River, 1.75 

miles (2.8 km) below the large wharf at Fairview Beach, King 

George County, Va., King George 7.5-min quadrangle (see 

fig. 15)

Ft (m) 

Sloped and covered .......................... 5.0 (1.5)

Nanjemoy Formation (Potapaco Member, 

Bed A)

Sand, grayish-yellow, weathered, clayey, 

fine, poorly sorted, glauconitic ............ 6.0 (1.8)

 Unconformity 

Marlboro Clay

Clay, light-gray (N 7), somewhat weathered, blocky ........................... 6.0 (1.8)

 Unconformity 

Aquia Formation (Paspotansa Member) 

Sand, grayish-yellow, silty, very weathered; 

molds of Turritella mortoni .............. 2.5 (0.7)

 Sea Level14. (USGS Locality 26343) Left bank of the Rappahannock River, 

1.05 miles (1.68 km) above the mouth of Ware Creek, King 

George County, Va., Rappahannock Academy 7.5-min 

quadrangle

Ft (m) 

Sloped and covered .......................... 3.0 (0.9)

Aquia Formation (Paspotansa Member)

Sand, same as below but weathered, 

grayish-orange (10 YR 7/4) ............... 3.0 (0.9)

Sand, olive-black (5 Y 2/1), glauconitic, 

micaceous, silty, well sorted; many 

Turritella mortoni ...................... 7.0 (2.1)

 Sea Level15. (USGS Locality 26344) Right bank of the Rappahannock 

River, 0.35 mile (0.56 km) below the mouth of Ware Creek, 

Caroline County, Va., Rappahannock Academy 7.5-min 

quadrangle

Ft (m) 

Sloped and covered ......................... 40.0 (12.2)

Aquia Formation (Paspotansa Member)

Sand, olive-black (5 Y 2/1), fine, wellsorted, glauconitic, micaceous; contains 

many Turritella ........................ 4.0 (1.2)

 Sea Level16. (USGS Locality 26345) Left bank of the Rappahannock 

River, 0.45 mile (0.72 km) above the mouth of Lambs Creek, 

King George County, Va., Rappahannock Academy 7.5-min 

quadrangle

Ft (m) 

Sloped and covered ......................... 15.0 (4.6)

Aquia Formation (Paspotansa Member)

Sand, olive-black (5 Y 2/1), fine, wellsorted, glauconitic, micaceous ............ 4.0 (1.2)

 Sea Level17. (USGS Locality 26346) Left bank of the Rappahannock River, 

0.4 mile (0.6 km) below the mouth of Lambs Creek, King 

George County, Va., Passapatanzy 7.5-min quadrangle

Ft (m) 

Sloped and covered ......................... 10.0 (3.0)

Aquia Formation (Paspotansa Member)

Sand, grayish-orange (10 YR 7/4), weathered, leached, fine, silty ................. 3.0 (0.9)

Sand, olive-black (5 Y 2/1), fine, silty, 

micaceous, well-sorted, glauconitic; 

contains discontinuous bands of Turritella mortoni ........................... 6.0 (1.8)

 Sea Level18. (USGS Locality 26347) Left bank of the Rappahannock River, 

0.3 mile (0.5 km) above Hopyard Landing, King George 

County, Va., Port Royal 7.5-min quadrangle

Ft (m) 

Covered with vegetation ..................... 13.0 (4.0)

Aquia Formation (Paspotansa Member) 

Sand, olive-black (5 Y 2/1), fine, micaceous, 

well-sorted, glauconitic; Turritella common; line of concretions at +4 feet 

( + 1.2 m) .............................. 7.0 (2.1)

 Sea Level19. (USGS Locality 26348) Left bank of the Rappahannock River, 

0.65 mile (1.05 km) below the mouth of Jones Top Creek, 

King George County, Va., Port Royal 7.5-min quadrangle

Ft (m) 

Covered .................................... 2.0 (0.6)

(?)Formation

Conglomerate, coarse, sandy ............... 2.0 (0.6)

Aquia Formation (Paspotansa Member)

Sand, olive-black (5 Y 2/1), fine, wellsorted, glauconitic, micaceous; small 

shell fragments; line of indurated nodules at +4 feet ( + 1.2 m) ............... 10.0 (3.0)

 Sea Level20. (USGS Locality 26349) 1.0 mile (1.6 km) northwest of Wrights 

Corner, where Rte. 634 crosses Hobby Swamp, Caroline 

County, Va., Woodford 7.5-min quadrangle

Core taken by R.B. Mixon, U.S. Geological Survey, Reston, Va.

21. (USGS Locality 26350) Smoots Pond, near the miUrace, just north 

of Rte. 640, in Camp A.P. Hill, Caroline County, Va., Bowling 

Green 7.5-min quadrangle

Core taken by R.B. Mixon, U.S. Geological Survey, Reston, Va.

22. (USGS Locality 26351) Right bank of the Mattaponi River, 

0.15 mile (0.24 km) above the Rte. 301 bridge, Caroline 

County, Va., Penola 7.5-min quadrangle

Ft (m) 

Covered .................................... 6.0 (1.8)

Aquia Formation (Paspotansa Member)

Sand, olive-black (5 Y 2/1), glauconitic, 

silty, fine, micaceous, well-sorted, somewhat weathered; Turritella and other 

mollusks common but poorly preserved .... 6.0 (1.8)

 Water Level 
LOCALITIES AND MEASURED SECTIONS 65

23. (USGS Locality 26352) Left bank of the Mattaponi River, in 

a small stream cut just below the Rte. 654 bridge, Caroline 

County, Va., Penola 7.5-min quadrangle

Ft (m) 

Pleistocene(?)

Gravel, coarse, white ..................... 2.0 (0.6)

 Unconformity 

Nanjemoy Formation (Potapaco Member, 

BedB)

Sand, olive-gray (5 Y 4/1), clayey, poorly 

sorted, glauconitic; Venericardia potapacoensis molds concentrated in thin 

beds but also scattered throughout ...... 10.0 (3.0)

Nanjemoy Formation (Potapaco Member, 

Bed A?) 

Sand, olive-gray (5 Y 5/1), silty ............. 2.0 (0.6)

 Water Level24. (USGS Locality 26353) Left bank of the Pamunkey River, 

0.65 mile (1.05 km) below Sturgeon Hole, just below the 

mouth of Mill Creek, Caroline County, Va., Hanover 7.5-min 

quadrangle (see fig. 21)

Ft (m) 

Pleistocene(?)

Gravel, yellow, sandy ..................... 6.0 (1.8)

 Unconformity 

Nanjemoy Formation (Potapaco Member, 

Bed A)

Sand, olive-black (5 Y 2/1), fine, silty, glauconitic, micaceous; no molds ............. 2.0 (0.6)

 Unconformity 

Marlboro Clay

Clay, light-gray (N 7); very burrowed from 

above ................................. 0.5 (0.2)

 Unconformity 

Aquia Formation (Paspotansa Member)

Sand, olive-black (5 Y 2/1), fine, well-sorted, 

glauconitic, micaceous; many Turritella 

present throughout but concentrated in 

beds, preservation moderate ............. 8.0 (2.4)

 Water Level25. (USGS Locality 26354) Left bank of the Pamunkey River, 0.25 

mile (0.40 km) below the Rte. 301 bridge (Littlepage Bridge), 

Caroline County, Va., Hanover 7.5-min quadrangle

Ft (m) 

Pleistocene(?)

Gravel, sandy ........................... 3.0 (0.9)

 Unconformity 

Aquia Formation (Paspotansa Member)

Sand, yellow-orange, weathered, glauconitic .................................. 12.0 (3.7)

Sand, olive-black (5 Y 2/1), fine, well-sorted, 

glauconitic, micaceous; numerous Turritella in bands, preservation moderate ...... 8.0 (2.4)

Nodules, thin bed, indurated, intermittent . . . 0.5 (0.2)

Sand, olive-black (5 Y 2/1), fine, well-sorted, 

glauconitic, micaceous; scattered Turritella, preservation poor to moderate ...... 4.0 (1.2)

 Water Level26. (USGS Locality 26355) Left bank of the Pamunkey River at 

Sturgeon Hole, 0.75 mile (1.21 km) below the Rte. 301 

bridge (Littlepage Bridge), Caroline County, Va., Hanover 

7.5-min quadrangle (see fig. 17)

Ft (m) 

Covered ................................... 10.0 (3.0)

Aquia (?)

Sand, yellowish-orange, clayey, weathered .... 3.0 (0.9)

Sand, olive-black (5 Y 2/1), fine, well sorted; 

shell material leached ................... 2.5 (0.8)

Aquia Formation (Paspotansa Member)

Sand, olive-black (5 Y 2/1), silty, glauconitic, 

well-sorted, micaceous; many Turritella .... 8.0 (2.4)

Concretions, intermittent, glauconitic ....... 1.0 (0.3)

Sand, olive-black (5 Y 2/1), silty, glauconitic, well-sorted; micaceous; many 

Turritella, some Ostrea sinuosa ........... 6.0 (1.8)

 Water Level27. (USGS Locality 26356) Left bank of the James River, 1.1 

miles (1.8 km) above Shirley Plantation, Charles City County, 

Va., Hopewell 7.5-min quadrangle

Ft (m) 

Covered ................................... 20.0 (6.1)

Aquia Formation (Paspotansa Member)

Sand, olive-gray (5 Y 4/1), somewhat weathered, well-sorted, fine, micaceous, glauconitic; some carbonaceous material; molds of 

Turritella and Crassatellites alaeformis ..... 6.0 (1.8

 Sea Level28. (USGS Locality 26357) City Point, right bank of the James 

River at the mouth of the Appomattox River, Hopewell, 

Prince George County, Va., Hopewell 7.5-min quadrangle

Ft (m)

Covered ................................... 25.0 (7.6)

Aquia Formation (Paspotansa Member)

Sand, dark-olive-black (5 Y 2/1), fine, micaceous, leached .......................... 3.0 (0.9)

 Sea Level29. (USGS Locality 26358) Right bank of the James River, just 

below the mouth of Bailey Creek, Prince George County, Va., 

Westover 7.5-min quadrangle

Ft (m) 

Covered (sloped) ............................ 20.0 (6.1)

Marlboro Clay

Clay, pink (10 R 7/4) in lower one-third, 

gray (N 7) in upper two-thirds, gypsum 

crystals common throughout; rare small 

gastropod molds ....................... 10.0 (3.0)

 Unconformity 

Aquia Formation (Paspotansa Member)

Sand, fine, well-sorted, glauconitic, weathered, reddish-yellow, somewhat indurated ... 0.5 (0.2) 

Sand, olive-black (5 Y 2/1), fine, silty, micaceous, well-sorted, glauconitic; scattered poorly preserved Turritella and Crassatellites . . . 12.0 (3.7) 

Sand, olive-black (5 Y 2/1), fine, weathered, well-sorted, glauconitic; shell 

material poorly preserved, numerous 

Turritella, Ostrea ....................... 5.0 (1.5)

 Sea Level 
66 STRATIGRAPHY AND MOLLUSKS OF PAMUNKEY GROUP AND OLD CHURCH FORMATION

30. (USGS Locality 26359) Right bank of the Potomac River, 0.3 

mile (0.5 km) above Belvedere Beach, King George County, 

Va., Passapatanzy 7.5-min quadrangle

Ft (m) 

Covered .................................... 5.0 (1.5)

Aquia Formation (Paspotansa Member)

Sand, olive-black (5 Y 2/1), fine, wellsorted, silty, micaceous, glauconitic; 

numerous Turritella, scattered as well 

as in distinct bands, common Ostrea 

sinuosa, moderate molluscan diversity .... 12.0 (3.7)

 Sea Level31. (USGS Locality 26360) Right bank of Rappahannock River, 

directly across from Goat Island, Caroline County, Va., 

Port Royal 7.5-min quadrangle

Ft (m) 

Covered ................................... 20.0 (6.1)

Nanjemoy Formation (Potapaco Member, 

BedB)

Sand, olive-gray (5 Y 4/1), very clayey, fine, 

glauconitic; bands of Venericardia .......... 4.0 (1.2)

Nanjemoy Formation (Potapaco Member, 

Bed A)

Sand, olive-black (5 Y 2/1), fine, clayey, 

glauconitic; small shells common .......... 6.0 (1.8)

 Sea Level32. (USGS Locality 26361) Right bank of the Mattaponi River, 

just below the Rte. 207 bridge, Caroline County, Va., Woodford 7.5-min quadrangle (see fig. 20)

Ft (m) 

Covered .................................... 4.0 (0.9)

Pleistocene(?)

Gravel, sandy, orange .................... 4.0 (0.9)

 Unconformity 

Nanjemoy Formation (Potapaco Member, 

Bed A)

Sand, olive-black (5 Y 2/1), glauconitic, 

silty, some indurated nodules; medium 

to coarse sand concentrated near base 

with phosphate and quartz pebbles 

common; a few scattered molds of 

bivalves ............................... 3.0 (1.5)

 Unconformity 

Marlboro Clay

Clay, gray (N 7); upper surface burrowed, 

burrows filled with Potapaco sediment ..... 2.0 (0.9)

 Water Level33. (USGS Locality 26362) Right bank of the Pamunkey River, 

0.95 mile (1.53 km) straightline above the Rte. 301 bridge 

(Littlepage Bridge), Hanover County, Va., Ashland 7.5- 

min quadrangle

Ft (m) 

Covered ................................... 10.0 (3.0)

Eastover Formation

Sand, weathered, grayish-yellow, fine, burrowed ................................ 8.0 (2.4)

 Unconformity 

Calvert Formation

Clay, weathered, yellowish-gray (5 Y 7/2), 

diatomaceous .......................... 3.0 (0.9)

 Unconformity 

Nanjemoy Formation (Potapaco Member, 

Bed A)

Sand, weathered, brownish-gray (5 YR 4/1), 

clayey, poorly sorted, moderately glauconitic, micaceous ...................... 4.0 (1.2)

 Unconformity 

Marlboro Clay

Clay, gray (N 7); burrows filled with 

sand from Potapaco Member ............. 1.5 (0.5)

 Unconformity 

Aquia Formation (Paspotansa Member)

Sand, olive-black (5 Y 2/1), fine, micaceous, 

silty, well-sorted, glauconitic, somewhat 

weathered on the surface; upper surface 

burrowed, burrows filled with sediment 

from Potapaco and Marlboro ............ 10.0 (3.0)

Covered by slump .......................... 10.0 (3.0)

 Water Level34. (USGS Locality 26363) Left bank of the Potomac River, 

2.5 miles (4.0 km) above Popes Creek, 1.7 miles (2.7 km) 

southeast of Windmill Point, Charles County, Md., Mathias 

Point 7.5-min quadrangle (see fig. 26)

Ft (m) 

Holocene

Soil, contains Crassostrea as artifacts ....... 3.0 (0.9)

 Unconformity 

Nanjemoy Formation (Woodstock Member) 

Sand, grayish-yellow, very weathered, 

glauconitic, clayey; abundant carbonaceous material ........................ 4.0 (1.2)

Nanjemoy Formation (Potapaco Member, 

BedB)

Sand, grayish-yellow, weathered, glauconitic, clayey; line of concretions near 

top of bed ............................. 2.0 (0.6)

Sand, olive-gray (5 Y 4/1), very clayey, 

glauconitic; thin beds of Venericardia 

potapacoensis .......................... 4.0 (1.2)

 Unconformity 

Nanjemoy Formation (Potapaco Member, 

Bed B?)

Clay, olive-black (5 Y 2/1), silty, sandy, 

glauconitic, burrowed ................... 4.0 (1.2)

 Sea Level 
LOCALITIES AND MEASURED SECTIONS 67

35. (USGS Locality 26364) Right bank of the Rappahannock River, 

0.2 mile (0.3 km) below the mouth of Ware Creek, Caroline 

County, Va., Rappahannock Academy 7.5-min quadrangle

Ft (m) 

Pleistocene(?)

Gravel, grayish-orange, sandy .............. 7.0 (2.1)

Nanjemoy Formation (Potapaco Member, 

BedB)

Sand, olive-gray (5 Y 4/1), glauconitic, 

clayey; prominent thin bands where 

Venericardia have been leached ........... 5.0 (1.5)

Nanjemoy Formation (Potapaco Member, 

Bed A)

Sand, olive-black (5 Y 2/1), glauconitic, 

silty; scattered small shells ............. 10.0 (3.0)

Slump ................................. 12.0 (3.7)

 Sea Level36. (USGS Locality 26365) Left bank of the Mattaponi River, 1.5 

miles (2.4 km) (straightline) above the Rte. 207 bridge, Caroline 

County, Va., Woodford 7.5-min quadrangle

Ft (m) 

Sloped and covered ......................... 15.0 (4.6)

Nanjemoy (Potapaco Member, Bed A)

Sand, olive-black (5 Y 2/1), silty, fine, 

moderately glauconitic, some pebbles; 

scattered molds of Venericardia .......... 4.0 (1.2)

 Water Level37. (USGS Locality 26366) Left bank of the Mattaponi River, 

next to the Rte. 605 bridge at Bowling Green Park, Caroline 

County, Va., Woodford 7.5-min quadrangle

Ft (m) 

Sloped and covered ......................... 15.0 (4.5)

Nanjemoy Formation (Potapaco Member, 

Bed A)

Sand, olive-gray (5 Y 4/1), micaceous, 

glauconitic, fine, silty; molds of Venericardia common ......................... 4.0 (1.2)

 Water Level38. (USGS Locality 26367) Left bank of the Pamunkey, 0.65 mile 

(1.04 km) above Normans Bridge (Rte. 614), King William 

County, Va., Hanover 7.5-min quadrangle (see fig. 24)

Ft (m) 

Pleistocene (?)

Gravel, sandy ........................... 1.0 (0.3)

 Unconformity 

Nanjemoy Formation (Potapaco Member, 

Bed B)

Sand, olive-gray (5 Y 4/1), very clayey, 

glauconitic, burrowed; many Venericardia potapacoensis in thin bands ........ 6.0 (1.8)

 Disconformity 

Nanjemoy Formation (Potapaco Member, 

Bed A)

Sand, olive-black (5 Y 2/1), glauconitic, 

fine, silty; upper surface uneven, 

burrowed .............................. 4.0 (1.2)

 Water Level39. (USGS Locality 26368) Left bank of the Patuxent River, 

0.85 mile (1.37 km) below Nottingham, Calvert County, 

Md., Lower Marlboro 7.5-min quadrangle

Ft (m) 

Covered ................................... 10.0 (3.0)

Calvert Formation

Clay, yellowish-gray (5 Y 8/1), weathered, 

diatomaceous .......................... 3.0 (0.9)

Sandstone, indurated, yellowish-gray 

(5 Y 8/1), fine- to medium-grained; some 

pebbles, Pecten humphreysii as molds ..... 0.5 (0.2)

 Unconformity 

Nanjemoy Formation (Woodstock Member) 

Sand, olive-gray (5 Y 4/1), silty, glauconitic, 

well-sorted, fine, pebbles along base ....... 3.0 (0.9)

 Unconformity 

Nanjemoy Formation (Potapaco Member, 

BedC)

Clay, olive-gray (5 Y 4/1), very burrowed, 

fine- to medium-sand-sized glauconite 

filling burrows ......................... 7.0 (2.1)

Sand, olive-gray (5 Y 4/1), clayey, glauconitic, fine to medium, compact .......... 8.0 (2.4)

 Sea Level40. (USGS Locality 26369) Left bank of the Patuxent River, 

0.55 mile (0.89 km) below the mouth of Lyons Creek, Calvert 

County, Md., Lower Marlboro 7.5-min quadrangle

Ft (m) 

Sloped .................................... 10.0 (3.0)

Calvert Formation

Clay, light-yellowish-gray (5 Y 9/1), highly 

diatomaceous, weathered, blocky .......... 5.0 (1.5)

Sandstone, yellowish-gray (5 Y 8/1), indurated, medium-grained; molds of mollusks . . 1.0 (0.3) 

Sand, yellowish-gray (5 Y 8/1), medium, 

unconsolidated ......................... 0.5 (0.2)

 Unconformity 

Nanjemoy Formation (Potapaco Member) 

Sand, glauconitic, weathered, partially 

covered and sloped .................... 35.0 (10.7)

Sand, olive-gray (5 Y 4/1), clayey, compact, 

very glauconitic, fine calcareous material leached ............................ 8.0 (2.4)

 Sea Level41. (USGS Locality 26370) Right bank of the Potomac River, 

2.7 miles (4.3 km) below the big pier at Fairview Beach, 

King George County, Va., King George 7.5-min quadrangle

Ft (m) 

Covered .................................... 3.0 (0.9)

Pleistocene(?)

Conglomerate, sand, gravel, cobbles, 

orange ............................... 20.0 (6.1)

 Unconformity 

Nanjemoy Formation (Potapaco Member, 

BedB)

Sand, olive-gray (5 Y 4/1), clayey, fine, 

glauconitic; bands of bedded Venericardia potapacoensis ..................... 15.0 (4.6)

 Sea Level 
68 STRATIGRAPHY AND MOLLUSKS OF PAMUNKEY GROUP AND OLD CHURCH FORMATION

42. (USGS Locality 26371) Right bank of the Rappahannock River, 

1.0 miles (1.6 km) (straightline) below the mouth of Ware 

Creek, Caroline County, Va., Rappahannock Academy 

7.5-min quadrangle

Ft (m) 

Covered ................................... 15.0 (4.6)

Nanjemoy Formation (Potapaco Member, 

BedB)

Sand, olive-gray (5 Y 4/1), clayey, fine, 

glauconitic; scattered Venericardia ........ 8.0 (2.4)

Sand, olive-gray (5 Y 4/1), clayey, fine, 

glauconitic; Venericardia in thin 

beds .................................. 8.0 (2.4)

Slumped and covered ....................... 20.0 (6.1)

 Sea Level43. (USGS Locality 26372) Right bank of Mill Creek, just below the 

dam at Millers Pond (now drained), 150 feet (54.7 m) upstream from the Rte. 17 bridge, Camp A.P. Hill Military 

Reservation, Caroline County, Va., Port Royal 7.5-min 

quadrangle

Ft (m) 

Sloped and covered .......................... 6.0 (1.8)

Nanjemoy Formation (Potapaco Member, 

BedB)

Sand, somewhat weathered, olive-gray 

(5 Y 4/1), clayey, glauconitic; leached thin 

bands of Venericardia molds ............. 8.0 (2.4)

 Water Level44. (USGS Locality 26373) Left bank of the Rappahannock River, 

0.4 mile (0.6 km) above the mouth of Gingoteague Creek, 

King George County, Va., Port Royal 7.5-min quadrangle

Ft (m) 

Covered ................................... 10.0 (3.0)

Nanjemoy Formation (Potapaco Member, 

BedC)

Clay, olive-gray (5 Y 4/1), very burrowed, 

very glauconitic; fresh in lower 4 feet 

(1.2 m) and weathered to grayish-yellow 

(5 Y 8/4) in upper 6 feet (1.8 m) .......... 10.0 (3.0)

 Sea Level45. (USGS Locality 26374) Left bank of the Mattaponi River, 

1.0 mile (1.6 km) east of Reedy Mill, 1.8 miles south of 

Shumansville, Caroline County, Va., Penola 7.5-min 

quadrangle (see fig. 25)

Ft (m) 

Covered .................................... 3.0 (0.9)

Nanjemoy Formation (Potapaco Member, 

BedB)

Sand, olive-gray (5 Y 4/1), clayey, fine, 

glauconitic; a thin bed of concretions 

in lower 2 feet (0.6 m); thin bands of 

Venericardia extending from below 

water level to approx. 6 feet (1.8 m) 

above water level ....................... 8.0 (2.4)

 Water Level46. (USGS Locality 26375) Right bank of the Mattaponi River, 

0.38 mile (0.61 km) northeast of the intersection of Routes 

601 and 663, Caroline County, Va., Penola 7.5-min quadrangle

Ft (m) 

Covered .................................... 8.0 (2.4)

Nanjemoy Formation (Potapaco Member, 

BedB)

Sand, olive-gray (5 Y 4/1) clayey, fine, 

glauconitic; thin bands of Venericardia 

dipping upstream (northwest) at approximately 4° ............................. 6.0 (1.8)

 Water Level47. (USGS Locality 26376) Right bank of the Mattaponi River, 

0.48 mile (0.77 km) east of the intersection of Routes 601 

and 663, Caroline County, Va., Penola 7.5-min quadrangle

Ft (m) 

Covered ................................... 25.0 (7.6)

Nanjemoy Formation (Potapaco Member, 

BedB)

Sand, olive-gray (5 Y 4/1), clayey, greenishgray, glauconitic; thin bands of poorly 

preserved Venericardia ................. 10.0 (3.0)

 Water Level48. (USGS Locality 26377) Right bank of the Pamunkey River, 

0.8 mile (1.3 km) below Hanovertown, just below a sharp 

bend, Hanover County, Va., Manquin 7.5-min quadrangle

Ft (m) 

Covered ................................... 10.0 (3.0)

Nanjemoy Formation (Potapaco Member, 

BedB)

Sand, olive-gray (5 Y 4/1), clayey, fine, 

glauconitic; thin bands of Venericardia 

potapacoensis, Cubitostrea common; 

beds dip upriver (northwest) at approximately 4° ............................. 5.0 (1.5)

 Water Level49. (USGS Locality 26378) Left bank of the Pamunkey River, 

0.85 mile (1.37 km) northwest of the boat landing above 

Dabneys Millpond, King William County, Va., Manquin 7.5- 

min quadrangle

Ft (m) 

Covered ................................... 10.0 (3.0)

Nanjemoy Formation (Woodstock Member) 

Sand, olive-black (5 Y 2/1), fine, massive, 

silty, well-sorted, glauconitic; calcareous 

material leached ........................ 5.0 (1.5)

Slumped and covered ....................... 10.0 (3.0)

 Contact not visible 

Nanjemoy Formation (Potapaco Member, 

BedB)

Sand, olive-gray (5 Y 4/1), clayey, fine, 

glauconitic; thin bands of Venericardia .... 5.0 (1.5)

Slumped ................................... 5.0 (1.5)

 Water Level 
LOCALITIES AND MEASURED SECTIONS 69

50. (USGS Locality 26379) Left bank of the Pamunkey River, at 

a tall bluff on the river bend just below the boat landing at 

the end of Rte. 602 at Dabneys Millpond, King William 

County, Va., Manquin 7.5-min quadrangle (see fig. 27)

Ft (m) 

Pleistocene(?)

Sand and gravel, orange ................. 20.0 (6.1)

 Unconformity 

Nanjemoy Formation (Woodstock Member) 

Sand, olive-black (5 Y 4/1), silty, fine, very 

glauconitic, massive; bed of large concretions in lower 2 feet (0.6 m), pebbles, wood 

along lower contact, grayish yellow where 

weathered ............................. 5.0 (1.5)

 Unconformity 

Nanjemoy Formation (Potapaco Member, 

Bed C)

Sand, olive-gray (5 Y 4/1), very burrowed, 

very glauconitic, clayey, grayish-yellow 

where weathered; three planes of glauconite concentration mark short-term 

diastems within the unit ................ 10.0 (3.0)

 Gradational contact 

Nanjemoy Formation (Potapaco Member, 

Bed B)

Sand, olive-gray (5 Y 4/1), clayey, fine, glauconite; numerous thin bands of Venericardia; Cubitostrea common .............. 4.0 (1.2)

 Water Level51. (USGS Locality 26380) Right bank of the Pamunkey River, at 

Hanovertown, Hanover County, Va., Manquin 7.5-min 

quadrangle

Ft (m) 

Covered .................................. 10.0 (3.0)

Nanjemoy Formation (Potapaco Member, 

Bed B)

Sand, olive-gray (5 Y 2/1), clayey, fine, glauconitic; thin bands of Venericardia dipping 

downstream .......................... 8.0 (2.4)

 Water Level52. (USGS Locality 26381) Left bank of the Patuxent River, 0.3 mile 

(0.5 km) above Jones Point, Calvert County, Va., Lower 

Marlboro 7.5-min quadrangle

Ft (m) 

Covered .................................. 30.0 (9.1)

Calvert Formation

Clay, light-yellowish-gray (5 Y 9/1), blocky, 

weathered, diatomaceous ................ 8.0 (2.4)

Sandstone, yellowish-gray (5 Y 8/1), mediumgrained; molds of Pecten Humphreysii ..... 1.0 (0.3)

 Unconformity * 

Nanjemoy Formation (Woodstock Member) 

Sand, olive-black (5 Y 2/1), fine, well-sorted, 

micaceous, silty, glauconitic; pebbles along 

the lower contact ..................... 12.0 (3.7)

 Unconformity 

Nanjemoy Formation (Potapaco Member, 

Bed C)

Sand, olive-gray (5 Y 4/1), very burrowed, 

very glauconitic, very clayey; grayish 

yellow (5 Y 8/4) where weathered ........ 15.0 (4.6)

 Sea Level53. (USGS Locality 26382) Left bank of the Potomac River, 0.4 mile 

(0.6 km) above Popes Creek, Charles County, Md., Popes Creek 

7.5-min quadrangle (see fig. 32). Bed C was exposed at beach 

level in 1969 but now is covered with beach sand.

Ft (m) 

Pleistocene(?)

Sand, orange .......................... 15.0 (4.6)

 Unconformity 

Calvert Formation (Fairhaven Member)

Clay, yellowish-gray (5 Y 8/1), weathered,

blocky, diatomaceous; this bed is associated with the second sedimentation

pulse ............................... 10.0 (3.0)

Sand, olive-brown (5 Y 4/4), silty, phosphatic, poorly sorted, fine to medium,

pebbles along contact; fining upward;

contains diatoms; this bed is associated

with the first sedimentation pulse ....... 10.0 (3.0)

 Unconformity 

Nanjemoy Formation (Woodstock Member) 

Sand, olive-black (5 Y 2/1), well-sorted, 

fine, silty, glauconitic ................... 6.0 (1.8)

Sand, olive-black (5 Y 2/1), compact, 

well-sorted, fine, silty, glauconitic, burrowed ............................... 18.0 (5.5)

 Sea Level54. (USGS Locality 26383) Left bank of the Rappahannock River, 

0.2 mile (0.3 km) above Greenlaw Wharf, King George County, 

Va., Rollins Fork 7.5-min quadrangle (see fig. 33)

Ft (m) 

Covered .................................. 10.0 (3.0)

Nanjemoy Formation(?)

Sand, grayish-yellow (5 Y 8/4), medium to 

pebbly, poorly sorted, slightly glauconitic; 

fine, lower contact undulant and burrowed ................................ 5.0 (1.5)

 Unconformity (?) 

Nanjemoy Formation (Woodstock Member) 

Sand, olive-black (5 Y 2/1), fine, silty, 

micaceous, well-sorted, glauconitic, burrowed; molds and casts ................. 4.0 (1.2)

 Sea Level55. (USGS Locality 26384) Left bank of the Mattaponi River, 0.95 

mile (1.53 km) east of Reedy Mill, 1.85 miles (2.98 km) south 

of Shumansville, Caroline County, Va., Penola 7.5-min 

quadrangle

Ft (m) 

Covered ................................... 8.0 (2.4)

Nanjemoy Formation (Woodstock Member) 

Sand, olive-black (5 Y 2/1), silty, very fine, 

micaceous, glauconitic; contact with 

lower unit sharp ....................... 2.0 (0.6)

 Unconformity 

Nanjemoy Formation (Potapaco Member, Bed 

C)

Sand, olive-gray (5 Y 4/1), clayey, fine, 

glauconitic, burrowed ................... 6.0 (1.8)

 Water Level 
70 STRATIGRAPHY AND MOLLUSKS OF PAMUNKEY GROUP AND OLD CHURCH FORMATION

56. (USGS Locality 26385) Left bank of the Mattaponi River, 0.8 mile 

(1.3 km) east of Reedy Mill, 1.95 miles (3.24 km) south of 

Shumansville, Caroline County, Va., Penola 7.5-min quadrangle

Ft (m) 

Covered ................................... 3.0 (0.9)

Nanjemoy Formation (Woodstock Member) 

Sand, olive-black (5 Y 2/1), silty, very fine, 

micaceous, glauconitic; contact with 

lower unit sharp but burrowed .......... 6.0 (1.8)

 Unconformity 

Nanjemoy Formation (Potapaco Member, Bed 

C)

Sand, olive-gray (5 Y 4/1), clayey, fine, 

glauconitic, burrowing throughout ....... 3.0 (0.9)

 Water Level 

57. (USGS Locality 26386) Right bank of the Mattaponi River, 0.5 

mile (0.8 km) east of Reedy Mill, Caroline County, Va., Penola 

7.5-min quadrangle

Ft (m) 

Covered ................................... 6.0 (1.8)

Nanjemoy Formation (Woodstock Member) 

Sand, olive-black (5 Y 2/1), silty, very fine, 

micaceous, glauconitic; contact with 

lower unit sharp ....................... 6.0 (1.8)

 Unconformity 

Nanjemoy Formation (Potapaco Member, Bed 

C)

Sand, olive-gray (5 Y 4/1), clayey, fine, 

gray-green, glauconitic, burrowing 

throughout; upper surface burrowed ...... 3.0 (0.9)

 Water Level 

58. (USGS Locality 26387) Right bank of the Mattaponi River, 0.8 

mile (1.3 km) southeast of Reedy Mill, Caroline County, Va., 

Penola 7.5-min quadrangle (see fig. 28)

Ft (m) 

Covered .................................. 12.0 (3.7)

Nanjemoy Formation (Woodstock Member) 

Sand, olive-black (5 Y 2/1), silty, very fine, 

micaceous, glauconitic; contact with 

lower unit sharp ....................... 7.0 (2.1)

 Unconformity 

Nanjemoy Formation (Potapaco Member, Bed 

C)

Sand, olive-gray (5 Y 4/1), clayey, fine, 

glauconitic, burrowing throughout; upper 

surface burrowed ...................... 6.0 (1.8)

 Water Level59. (USGS Locality 26388) Right bank of the Pamunkey River, 1.0 

mile (1.6 km) southeast of Hanovertown, 0.55 mile (0.89 km) 

east of the intersection of Rtes. 604 and 605, Hanover County, 

Va., Manquin 7.5-min quadrangle

Ft (m) 

Covered ................................... 3.0 (0.9)

Nanjemoy Formation (Potapaco Member, Bed 

C)

Sand, olive-gray (5 Y 4/1), clayey, burrowed, 

fine, glauconitic ....................... 6.0 (1.8)

Covered ................................... 3.0 (0.9)

 Water Level60. (USGS Locality 26389) Right bank of the Pamunkey River, 

1.45 miles (2.33 km) southeast of Hanovertown, 1.3 miles east 

of the intersection of Rtes. 604 and 605, Hanover County, 

Va., Manquin 7.5-min quadrangle

Ft (m) 

Covered .................................. 10.0 (3.0)

Nanjemoy Formation (Potapaco Member, Bed C) 

Sand, olive-gray (5 Y 4/1), clayey, burrowed, 

fine, glauconitic; line of concretions at 

+ 4 feet (+1.2 m) ...................... 5.0 (1.5)

 Water Level61. (USGS Locality 26390) Right bank of the Pamunkey River, 

0.58 mile (0.93 km) (straightline) below the mouth of Totopotomoy Creek, 0.75 mile (1.21 km) northwest of the intersection of Rtes. 360 and 605, Hanover County, Va., Manquin 

7.5-min quadrangle (see fig. 29)

Ft (m) 

Covered .................................. 15.0 (4.6)

Nanjemoy Formation (Woodstock Member) 

Sand, olive-black (5 Y 2/1), fine, well-sorted, 

micaceous, glauconitic; clayey and poorly 

sorted at base, becoming silty and very well 

sorted upward; carbonaceous material abundant, scattered small shells throughout . . 10.0 (3.0)

 Unconformity 

Nanjemoy Formation (Potapaco Member, Bed D) 

Sand, dark-olive-black (5 Y 1/1), silty, 

clayey, very fine, burrowed, very glauconitic, micaceous; large concretions, 

some phosphate pebbles ................ 2.0 (0.6)

 Disconformity 

Nanjemoy Formation (Potapaco Member, Bed C) 

Clay, olive-gray (5 Y 4/1), abundant finesand-sized glauconite, very burrowed; 

small mollusk fragments common ........ 1.0 (0.3)

Covered ................................... 4.0 (1.2)

 Water Level62. (USGS Locality 26391) Right bank of the Pamunkey River, 

0.55 mile (0.89 km) (straightline) below the mouth of Totopotomoy Creek, 0.80 mile (1.29 km) northwest of the intersection of Rtes. 605 and 360, Hanover County, Va., Manquin 

7.5-min quadrangle

Ft fm) 

Covered .................................. 20.0 (6.1)

Nanjemoy Formation (Woodstock Member) 

Sand, olive-black (5 Y 2/1), fine, well-sorted, 

micaceous, silty, glauconitic; clayey and 

poorly sorted near base, becoming silty and 

very well sorted upward; carbonaceous material abundant, scattered small shells ..... 4.0 (1.2)

 Unconformity 

Nanjemoy Formation (Potapaco Member, Bed D) 

Sand, dark-olive-black (5 Y 1/1), silty, clayey, 

very fine, burrowed, very glauconitic, 

micaceous; large concretions, some phosphate pebbles ......................... 2.0 (0.6)

 Disconformity 

Nanjemoy Formation (Potapaco Member, Bed C) 

Clay, olive-gray (5 Y 4/1), clayey, glauconitic, very burrowed .................... 2.0 (0.6)

Covered ................................... 3.0 (0.9)

 Water Level 
LOCALITIES AND MEASURED SECTIONS 71

63. (USGS LocaHty 26392) Right bank of the Pamunkey River, 0.4 

mile (0.6 km) (straightline) below the mouth of Totopotomoy 

Creek, 0.95 mile (1.53 km) northwest of the intersection of Rtes. 

360 and 605, Hanover County, Va, Manquin 7.5-min quadrangle

Ft (m) 

Covered .................................. 15.0 (4.6)

Nanjemoy Formation (Woodstock Member) 

Sand, olive-black (5 Y 2/1), fine, well-sorted, 

micaceous, silty, glauconitic; clayey and 

poorly sorted near base, becoming silty 

and very well sorted upward, phosphate 

pebbles along base; scattered small molds, 

wood, nuts common .................. 15.0 (4.6)

 Unconformity 

Nanjemoy Formation (Potapaco Member, Bed D) 

Sand, dark-olive-black (5 Y 1/1), silty, clayey, 

very fine, burrowed, very glauconitic, micaceous, some phosphate pebbles; large 

concretions ........................... 2.0 (0.6)

 Disconformity 

Nanjemoy Formation (Potapaco Member, Bed C) 

Clay, olive-gray (5 Y 4/1), abundant sandsized glauconite, very burrowed ......... 2.5 (0.8)

 Water Level 

64. (USGS Locality 26393) Right bank of the Pamunkey River at the 

northern termination of Rte. 732, 1.35 miles (2.17 km) northeast of Farmers Shop Corner, Hanover County, Va., Manquin 

7.5-min quadrangle (see fig. 35-A)

Ft (m) 

Covered .................................. 10.0 (3.0)

Old Church Formation(?)

Sand, grayish-olive (10 Y 4/2), weathered,

clayey, moderate amounts of glauconite . . . 3.0 (0.91) 

Piney Point Formation

Sand, light-olive-gray (5 Y 6/1), very calcareous, slightly glauconitic; many mollusks, somewhat indurated at base; Woodstock fossils (Venericardia, Glycymeris) 

reworked into base ................... 15.0 (4.6)

 Unconformity 

Nanjemoy Formation (Woodstock Member) 

Sand, olive-black (5 Y 2/1), very fine, silty, 

micaceous, well-sorted, very glauconitic; 

numerous small, well-preserved mollusks; 

upper contact sharp and burrowed; 

burrows extend as much as 3 feet (0.9 m) 

downward ............................ 9.0 (2.7)

 Sea Level65. (USGS Locality 26394) Left bank of the Patuxent River, at the 

"Kaylorite" pit at the end of Landing Road, 1.2 miles (1.9 km) 

above Nottingham, in Calvert County, Md., Lower Marlboro 

7.5-min quadrangle (see fig. 44)

Ft (m) 

Calvert Formation (Fairhaven Member)

Clay, light-yellowish-gray (5 Y 9/1), weathered, very diatomaceous, blocky ........ 10.0 (3.0)

Sand, yellowish-gray (5 Y 8/1), indurated; 

fine to medium; molds of Pecten Humphrey sii and other bivalves ............. 1.0 (0.3)

Sand, yellowish-gray (5 Y 8/1), soft, fine to 

medium .............................. 0.5 (0.2)

 Unconformity 

7. (USGS Locality 26395)-Continued

Ft (m) 

Old Church Formation(?)

Sand, pinkish-gray (5 YR 7/1), clayey, silty, 

weathered; molds and casts of Lucinids; 

upper surface very burrowed ............ 1.0 (0.3)

 Unconformity 

Nanjemoy Formation (Woodstock Member) 

Sand, olive-black (5 Y 2/1), silty, very fine, 

micaceous, glauconitic; becoming very 

clayey in upper 5 feet (1.5 m) ........... 13.0 (4.0)

Sloped and covered ........................ 15.0 (4.6)

 Sea Level66. (USGS Locality 26395) Right bank of the Patuxent River at 

White Landing, Prince Georges County, Md., Lower Marlboro

7.5-min quadrangle (see fig. 45)

Ft (m)

Covered .................................. 10.0 (3.0)

Calvert Formation (Fairhaven Member)

Clay, light-yellowish-gray (5 Y 9/1), weathered, diatomaceous .................... 1.0 (0.3)

Sand, yellowish-gray (5 Y 8/1), coarse, indurated 1.5 (0.5) 

Sand, yellowish-gray (5 Y 8/1) to olivegray (5 Y 6/1), coarse, soft .............. 0.5 (0.2)

 UnconformityOld Church Formation (?)

Sand, grayish-olive (10 Y 4/2), clayey, silty, 

poorly sorted; many molds along contact, 

Lucinids common ...................... 1.5 (0.5)

 Unconformity 

Nanjemoy Formation (Woodstock Member) 

Sand, olive-black (5 Y 2/1), silty, very fine, 

micaceous; some molds ................. 1.0 (0.3)

 Sea Level67. (USGS Locality 26396) Right bank of the Potomac River, 1.65 

miles (2.66 km) above Mathias Point, King George County, 

Va., Mathias Point 7.5-min quadrangle. Principal reference 

section (lectostratotype locality) of the Woodstock Member (see

fig. 31 for Woodstock-Calvert contact)

Ft (m)

Pleistocene(?)

Sand, orange, coarse ..................... 5.0 (1.5)

Conglomerate, sand, gravel, cobbles, boulders 3.0 (0.9)

 Unconformity 

Calvert Formation (Fairhaven Member)

Clay, yellowish-gray (5 Y 8/1), silty, somewhat 

sandy near base, weathered, blocky, diatomaceous; phosphate and sand along contact .. 17.0 (5.2)

 Disconformity 

Clay, yellowish-gray (5 Y 8/1), silty, somewhat sandy towards base, weathered, 

blocky; phosphate, bone, and teeth along 

lower contact; as much as 3.0 feet (1.0 m) 

of relief along the lower contact ........ 10.0 (3.0)

 Unconformity 

Nanjemoy Formation (Woodstock Member) 

Sand, pale-greenish-yellow (10 Y 8/2),

weathered, fine, micaceous; molds and

casts; upper surface very eroded and

burrowed with as much as 3 feet (1.0 m)

of relief ............................. 25.0 (7.6)

Sand, olive-black (5 Y 2/1), silty, very fine,

micaceous, glauconitic; small mollusks

with moderate preservation ............ 15.0 (4.6)

 Sea Level 
72 STRATIGRAPHY AND MOLLUSKS OF PAMUNKEY GROUP AND OLD CHURCH FORMATION

68. (USGS Locality 26397) Left bank of the Potomac River, 0.95 mile 

(1.53 km) below the mouth of Popes Creek, Charles City 

County, Va., Popes Creek 7.5-min quadrangle

Ft (m) 

Pleistocene!?)

Conglomerate, yellowish-orange, weathered;

gravel, sand, cobbles, boulders ......... 25.0 (7.6)

Calvert Formation (Fairhaven Member)

Clay, light-yellowish-gray (5 Y 9/1), blocky,

diatomaceous ........................ 10.0 (3.0)

Sand, yellowish-gray (5 Y 8/1), silty ........ 2.0 (0.6)

 Disconformity 

Clay, light-yellowish-gray (5 Y 9/1), blocky . . 0.5 (0.2) 

Sand, yellowish-gray (5 Y 8/1), silty ........ 5.0 (1.5)

Sand, olive-brown (5 Y 4/4), silty, phosphatic, pebbles ........................ 1.5 (0.5)

Sand, yellowish-gray (5 Y 7/2), silty ........ 2.5 (0.8)

Sand, olive-brown ( 5 Y 4/4), silty, phosphatic, pebbles ........................ 2.0 (0.6)

 Unconformity 

Nanjemoy Formation (?) The following two units are 

provisionally referred to the Woodstock Member 

Sand, olive-gray (5 Y 4/1), medium, very 

glauconitic; many molds and casts; unit 

becoming thicker downstream ............ 0.75 (0.23)

 Disconformity 

Clay, olive-gray (5 Y 4/1), very burrowed; 

burrows filled with glauconite, possibly 

from bed above ........................ 0.25 (0.08)

 Disconformity 

Nanjemoy Formation (Woodstock Member) 

Sand, olive-black (5 Y 2/1), very fine, micaceous, silty, glauconitic; many small 

mollusks, poorly preserved .............. 5.0 (1.5)

Concretions, olive-gray (5 Y 4/1), calcareous, 

sandy, glauconitic, rounded .............. 5.0 (1.5)

Sand, olive-black (5 Y 2/1), very fine, micaceous, silty, glauconitic; many small 

mollusks, moderate preservation .......... 5.0 (1.5)

 Sea Level69. (USGS Locality 26398) Left bank of the Potomac River, 0.6 mile 

(1.0 km) above the Route 301 bridge (Harry W. Nice Bridge), 

Charles County, Md., Colonial Beach North 7.5-min quadrangle

Ft (m) 

Covered .................................. 20.0 (6.0)

Calvert Formation (Fairhaven Member)

Sand, olive-brown (5 Y 4/4), silty, slightly 

phosphatic, pebbles along lower contact; 

burrows extending down into underlying 

unit ................................. 6.0 (1.8)

 Unconformity 

Nanjemoy Formation(?) The following two units are 

provisionally referred to the Woodstock Member 

Sand, olive-gray (5 Y 4/1), fine, glauconitic; 

molds of mollusks abundant ............. 4.0 (1.2)

 Disconformity 

Clay, olive-gray (5 Y 4/1), very burrowed; 

burrows filled with glauconitic sand, 

probably from overlying bed ............. 1.0 (0.3)

 Disconformity 

Nanjemoy Formation (Woodstock Member) 

Sand, olive-black (5 Y 2/1), silty, very fine, 

micaceous, glauconitic; small shells 

abundant ............................. 1.0 (0.3)

 Sea Level70. (USGS Locality 26399) Left bank of the Rappahannock River, 

0.5 mile (0.8 km) below Wilmont Wharf, King George County, 

Va., Rollins Fork 7.5-min quadrangle (see fig. 39)

Ft (m) 

Covered .................................. 25.0 (7.6)

Calvert Formation (Fairhaven Member)

Clay, light-yellowish-gray (5 Y 9/1), silty, 

sandy along lower contact, very weathered, blocky, very diatomaceous ........ 12.0 (3.7)

Sand, grayish-brown (5 YR 3/2) silty, very 

fine, pebbles, phosphatic sand, teeth, 

bone along lower contact, becoming more 

clayey in upper portion ................. 4.0 (1.2)

 Unconformity 

Nanjemoy Formation(?) (possibly Woodstock 

Member)

Sand, yellowish-gray (5 Y 8/1), weathered, 

poorly sorted, medium, some glauconite, 

clean, pebbles, dipping sharply downstream; burrows of unit above in upper 

1 foot (0.3 m) ......................... 4.0 (1.2)

 Sea Level71. (USGS Locality 26400) Right bank of the Mattaponi River, 0.2 

mile (0.3 km) below the Rte. 647 bridge at Reedy Mill, Caroline 

County, Va., Penola 7.5-min quadrangle

Ft (m) 

Covered ................................... 4.0 (1.2)

Nanjemoy Formation (Woodstock Member) 

Sand, olive-black (5 Y 2/1), silty, very fine, 

micaceous, glauconitic .................. 6.0 (1.8)

 Unconformity 

Nanjemoy Formation (Potapaco Member, Bed 

C)

Sand, olive-gray (5 Y 4/1), clayey, glauconitic, burrowed ......................... 3.0 (0.9)

 Water Level72. (USGS Locality 26401) Right bank of the Mattaponi River, 

1.8 miles (2.9 km) (straightline) above the mouth of Maracossic Creek, King William County, Va., Sparta 7.5-min quadrangle

Ft (m) 

Pleistocene(?)

Sand, tan and orange, coarse ............. 8.0 (2.4)

Calvert Formation

Clay, yellowish-gray (5 Y 8/1), weathered, 

blocky, diatomaceous .................. 2.0 (0.6)

Sand, grayish-brown (5 YR 3/2), silty, 

clayey, slightly phosphatic; pebbles along 

lower contact ......................... 8.0 (2.4)

 Unconformity 

Nanjemoy Formation (Woodstock Member) 

Sand, olive-black (5 Y 2/1) silty, very 

fine, micaceous, weathered in upper portions ............................... 10.0 (3.0)

 Water Level 
LOCALITIES AND MEASURED SECTIONS 73

73. (USGS Locality 26402) Right bank of the Mattaponi River, 1.3 

miles (2.1 km) (straightline) above the mouth of Maracossic 

Creek, King William County, Va., Sparta 7.5-min quadrangle 

(see fig. 38)

Ft (m) 

Covered ................................... 2.0 (0.6)

Nanjemoy Formation(?) (Woodstock Member?) 

Sand, olive-gray (5 Y 4/1), silty, glauconitic, massive; molds and casts ........... 6.0 (1.8)

Sand, white (N 9), clean, quartz, some 

molds and casts ....................... 0.25 (0.08)

Sand, greenish-yellow (10 Y 8/2), weathered, 

very clean, quartz, some glauconite; thin 

clay laminae showing ripple marks, 

burrowed ............................. 4.0 (1.2)

 Water Level 

This deposit may represent a remnant of the nearshore facies of either 

the Woodstock Member or the Piney Point Formation.

74. (USGS Locality 26403) Right bank of the Pamunkey River, in a 

small ravine, 0.63 mile (1.01 km) south-southeast of the mouth 

of Totopotomoy Creek, 0.55 mile (0.89 km) north of the intersection of Rtes. 360 and 605, Hanover Co., Va., Manquin 7.5- 

min quadrangle (see fig. 37)

Ft (m) 

Covered ................................... 3.0 (0.9)

Piney Point Formation (Bed A)

Sand, yellowish-gray (5 Y 8/1), very calcareous, poorly sorted, fine to coarse, pebbly, 

partially indurated, leached; calcitic 

mollusks preserved (Cubitostrea sellaeformis); lower contact uneven, burrows 

projecting as much as 8 feet (2.4 m) into 

underlying unit ....................... 3.0 (0.9)

 Unconformity 

Nanjemoy Formation (Woodstock Member) 

Sand, olive-black (5 Y 2/1), silty, very fine, 

massive, glauconitic; contains large 

numbers of well-preserved mollusks scattered throughout, large Venericardia 

concentrated in several thin bands, much 

carbonaceous material ................. 15.0 (4.6)

Covered ................................... 6.0 (1.8)

 Water Level75. (USGS Locality 26404) Left bank of the Pamunkey River, 0.85 

mile (1.37 km) (straightline) below the Rte. 360 bridge, King 

William County, Va., Manquin 7.5-min quadrangle

Ft (m) 

Covered .................................. 10.0 (3.0)

Piney Point Formation (Bed A)

Sand, light-olive-gray (5 Y 6/1), very calcareous, moderately glauconitic, fine to medium, 

poorly sorted, partially indurated; containing many well-preserved mollusks; burrows 

from this unit extend downward through the 

Woodstock and below water level ......... 2.0 (0.6)

 Unconformity 

Nanjemoy Formation (Woodstock Member) 

Sand, olive-black (5 Y 2/1), silty, very fine, 

very glauconitic, well-sorted, micaceous; 

numerous well-preserved mollusks, most T 

conspicuous are large Venericardia ....... 5.0 (1.5)

 Sea Level76. (USGS Locality 26405) Right bank of the Pamunkey River, at the 

waterfall just above the old Newcastle Bridge, 1.35 miles 

(2.17 km) (straightline) below the Rte. 360 bridge, Hanover

County, Va., Manquin 7.5-min quadrangle

Ft (m)

Covered ................................... 2.0 (0.6)

Piney Point Formation (Bed A)

Sand, yellowish-gray (5 Y 8/1), weathered, 

indurated, calcareous, coarse to medium, 

pebbly, poorly sorted; aragonitic shells 

leached, calcitic shells preserved; forms 

indurated ledge for small waterfall ....... 2.0 (0.6)

 Unconformity 

Nanjemoy Formation (Woodstock Member) 

Sand, olive-black (5 Y 2/1), silty, very fine, 

very glauconitic, micaceous, well-sorted; 

many well-preserved mollusks throughout, large Venericardia concentrated in 

several thin bands, burrows from overlying 

Piney Point as deep as 5 feet (1.5 m) ..... 7.0 (2.1)

Covered ................................... 5.0 (1.5)

 Sea Level77. (USGS Locality 26406) Right bank of the Pamunkey River, 0.5 

mile (0.8 km) below the ruins of the old Newcastle Bridge, 0.45 

mile (0.72 km) above the northern termination of Rte. 732, 

Hanover County, Va., Manquin 7.5-min quadrangle

Ft (m) 

Covered .................................. 15.0 (4.6)

Piney Point Formation

Sand, light-greenish-gray (5 GY 7/1), calcareous, medium, quartz, glauconitic; mollusks 

abundant, Cubitostrea sellaeformis common; lower contact uneven, burrows extending down into the underlying unit .... 2.5 (0.8)

 Unconformity 

Nanjemoy Formation (Woodstock Member) 

Sand, olive-black (5 Y 2/1), silty, very fine, 

micaceous, well-sorted, very glauconitic; 

many small mollusks .................. 1.5 (0.5)

 Sea Level78. (USGS Locality 26407) Right bank of the James River, in a ravine 

downriver from the mouth of Baileys Creek at the northern termination of Rte. 644,1.40 miles (2.25 km) (straightline) above 

Jordan Point, Prince George County, Va., Westover 7.5-min

quadrangle

Ft (m)

Covered .................................. 50.0 (15.2)

Yorktown Formation (Morgarts Beach Member) 

Clay, blue-gray (4 B 4/1), silty; shells small 

and mostly leached ................... 15.0 (4.6)

 Grades sharply 

Yorktown Formation (Rushmere Member) 

Sand, blue-gray (5 B 5/1), medium, quartz; 

numerous large bivalves, especially 

Chesapecten madisonius and Mercenaria tridacnoides ...................... 4.0 (1.2)

 Unconformity 

Eastover Formation (Cobham Bay Member) 

Sand, blue-gray (5 B 5/1) where fresh, 

medium, quartz, phosphatic; numerous 

large bivalves (Isognomon, Chesapecten 

middesexensis, Euloxa) ................. 1.0 (0.3)

 Unconformity 
74 STRATIGRAPHY AND MOLLUSKS OF PAMUNKEY GROUP AND OLD CHURCH FORMATION

78. (USGS Locality 26407)-Continued

Ft (m)

Nanjemoy Formation (Woodstock Member) 

Sand, olive-black (5 Y 2/1), silty, very fine, 

micaceous; mollusks common, poorly 

preserved ........................... 12.0 (3.7)

Covered .................................. 20.0 (6.1)

79. (USGS Locality 26408) Right bank of the Tombigbee River,

at Hatchetigbee Bluff, Washington County, Ala. 

Section is described by Smith and Johnson (1887, p. 40).

80. (USGS Locality 26409) Left bank of the Potomac River, 0.8 

mile (1.3 km) northeast of the Piney Point Lighthouse on 

Piney Point, St. Marys County, Md., Piney Point 7.5-min 

quadrangle

The following is a summary of the well log taken by Otton (1955, 

p. 303-306) from the type well of the Piney Point. For more detail 

refer to that report. Well altitude: 5 feet (1.5 m)

Thickness Depth 

Ft (m) Ft (m) 

Pleistocene deposits ...... 120 (36.6) 0-120 (0-36.6)

Calvert Formation ....... 100 (30.5) 120-220 (36.6-67.1)

Piney Point Formation ... 50 (15.2) 220-270 (67.1-83.3) 

Nanjemoy Formation ..... 130 (39.6) 270-400 (82.3-121.9)

Aquia Formation ........ 10 (3.0) 400-410 (121.9-125.0)

81. (USGS Locality 26410) Left bank of the Rappahannock River, 

0.2 mile (0.3 km) below the mouth of Bristol Mine Run, at a 

ravine and waterfall, 0.95 mile (0.29 km) above Owl Hollow, 

Westmoreland County, Va., Rollins Fork 7.5-min quadrangle

Ft (m)

Covered .................................. 50.0 (15.2)

Calvert Formation (Fairhaven Member)

Clay, olive-brown (5 Y 4/4), silty, blocky, 

very diatomaceous, sandy and pebbly 

along a sharp lower contact ............ 20.0 (6.1)

 Disconf ormity 

Sand, olive-brown (5 Y 4/4), silty, clayey, 

quartz and phosphate pebbles, teeth, 

bone along irregular, burrowed lower 

contact; grades into blocky, diatomaceous clay in upper one-half ............... 4.5 (1.4)

 Unconformity 

Nanjemoy Formation (Woodstock Member) 

Sand, olive-black (5 Y 2/1), silty, very fine, 

micaceous ............................ 1.5 (0.5)

Covered ................................... 2.0 (0.6)

 Sea Level82. (USGS Locality 26411) West shore of the Chesapeake Bay, 

2 miles (3.2 km) below Long Beach, 2.25 miles (3.6 km) above 

Rocky Point, just above the Baltimore Gas and Electric powerplant, Calvert County, Md., Cove Point 7.5-min quadrangle 

Summary of data on a core taken at the E.G. and E. powerplant site 

by F.C. Whitmore and T.G. Gibson in September 1967. Examination 

of lower 9.0 feet (2.7 m) of the core has confirmed the presence of the 

Piney Point Formation on the basis of lithology, mollusks (Cubitostrea 

sellaeformis), and dinoflagellates. Used with the permission of

F.C. Whitmore (written commun., 1984).

(36.6 m) above sea level.

Thickness 

Ft (m)

Pleistocene(?) ............. 29 (8.8)

St. Marys Formation ...... 55 (16.8)

Choptank Formation ...... 50 (15.2)

Calvert Formation

Plum Point Marl Member 84 (25.6) 

Fairhaven Member ...... Ill (33.8)

Piney Point Formation .... 9 (2.7)

Altitude of well 120 feet

Depth

Ft (m) 

0-29 (0- 8.8) 

29-84 (8.8-25.6) 

84-134 (25.6-40.8)

134-218 (40.8-66.4) 

218-329 (66.4-100.3) 

329-338 (100.3-103.0)

83. (USGS Locality 26412) Right bank of the Pamunkey River at 

Horseshoe, Hanover County, Va, Manquin 7.5-min quadrangle. 

Type locality of the Old Church Formation. Hypostratotype 

or reference section for the Piney Point Formation (see fig. 40)

Ft (m) 

Covered .................................. 10.0 (3.0)

Calvert Formation

Sand, olive-brown (5 Y 4/4), clayey, phosphatic; quartz and phosphate pebbles 

and sand along sharp contact; some 

burrows extend downward through the 

Old Church and spread laterally along 

Old Church-Piney Point contact; fining 

to a blocky clay upward ................ 6.0 (1.8)

 UnconformityOld Church Formation

Sand, grayish-olive (10 Y 4/2), clayey, 

poorly sorted; some glauconite present, 

probably reworked from below; very 

calcareous owing to microfossil content, 

both primary and reworked; large concretions mark center of bed; mollusks 

common but small and poorly preserved, 

molds of Lucinids ...................... 3.0 (0.9)

 Unconformity 

Piney Point Formation (Bed B)

Sand, olive-gray (5 Y 4/1), clayey, very 

glauconitic, very calcareous owing to 

shell fragments and microfossils; many 

well-preserved mollusks, several distinct 

thin beds of Cubitostrea sellaeformis ..... 15.0 (4.6) 

 Sea Level84. (USGS Locality 26413) Left bank of the Pamunkey River, just 

below Piping Tree Ferry, King William County, Va., King 

William 7.5-min quadrangle (see fig. 41)

Ft (m) 

Covered .................................. 20.0 (6.1)

Piney Point Formation

Sand, greenish-gray (5 GY 6/1), clayey, 

glauconitic; partially indurated, concentrations of Cubitostrea sellaeformis in 

thin, cemented beds dipping downstream 

are exposed at very low water ........... 4.0 (1.2)

 Sea LevelThere are exposures at places along the bluffs downriver from Piping 

Tree Ferry. Slumps in this area expose up to 15.0 feet (4.6 m) of silty 

clays of the Calvert Formation overlying the Piney Point. The Old 

Church Formation is absent. In some exposures the Eastover Formation can be seen overlying the Calvert.
LOCALITIES AND MEASURED SECTIONS 75

85. (USGS Locality 26414) Right bank of the Pamunkey River, below 

Retreat, 0.05 mile (0.01 km) below the mouth of Whiting 

Swamp, Hanover County, Va., Manquin 7.5-min quadrangle 

(see fig. 42)

Ft (m) 

Covered and sloped ........................ 20.0 (6.1)

Calvert Formation

Clay, very weathered, silty, light gray ...... 2.0 (0.6)

Formation(?)

Sand, fine, moderately glauconitic, quartz, 

poorly sorted; cemented with poor molds 

and casts of mollusks; contact with 

underlying unit very irregular; deep 

burrows into underlying unit ............ 3.0 (1.0)

 Unconformity 

Piney Point Formation (Bed C)

Sand, olive-black (5 Y 2/1), coarse to 

medium, very glauconitic, weathered to 

yellowish-gray in upper portions; many 

small burrows weather out; no molds or 

casts; pink claystone concretions occur 

in upper portion ........................ 9.0 (2.7)

 Sea Level86. (USGS Locality 26415) Right bank of the Pamunkey River at 

Putneys Mill, 2.2 miles (3.5 km) north of Tunstall Station, New 

Kent County, Va., Tunstall 7.5-min quadrangle 

Core taken by L.E. Edwards, L.M. Bybell, and T.G. Gibson (all of 

USGS). Formational picks by L.E. Edwards. Altitude of drilling site: 

10 feet (3.0 m) above sea level.

Thickness Depth 

Ft (m) Ft (m) 

Pleistocene ............. 21 (6.4) 0-21 (0-6.4)

Old Church Formation .... 6 (1.8) 21-27 (6.4-8.2)

Piney Point Formation ... 33 (10.0) 27-60 (8.2-18.3) 

Uncertain .............. 8 (2.4) 60-68 (18.3-20.7)

Nanjemoy Formation ..... 49 (14.9) 68-117 (20.7-35.7)

Marlboro Clay ........... 13 (4.0) 117-130 (35.7-39.6)

87. (USGS Locality 26416) Right bank of the Pamunkey River, 0.50 

mile (0.80 km) below the mouth of Matadequin Creek, New 

Kent County, Va., Tunstall 7.5-min quadrangle

Ft (m) 

Covered ................................... 8.0 (2.4)

Old Church Formation

Sand, grayish-olive (10 Y 4/2), clayey, fine, 

very calcareous due to high microfossil 

content; some molds, few solitary corals . . 4.0 (1.2) 

 Sea Level88. (USGS Locality 26417) Warren Brothers sand pits, 1.4 miles 

(2.3 km) southeast of Bottoms Bridge, 2.0 miles (3.2 km) northeast of Elko, Henrico County, Va, Roxbury 7.5-min quadrangle. 

The Yorktown and Eastover Formations are exposed in an 

adjacent river escarpment. The Old Church Formation was exposed in the bottom of the pit below the terrace gravels.

Ft (m)

Covered ................................... 5.0 (1.5)

88. (USGS Locality 26417)-Continued

Ft (m)

Yorktown Formation (Rushmere Member) 

Sand, grayish-orange (5 Y 8/4), weathered, 

fine, very shelly; many Chesapecten 

madisonius, Ostrea sculpturata, Chama 

congregata .......................... 10.0 (3.0)

 Unconformity 

Eastover Formation (Cobham Bay Member) 

Sand, blue-gray (5 B 5/1), fine, phosphatic, 

pebbles along lower contact; contains 

Chesapecten middlesexensis, Isognomon . . 1.0 (0.3)

 Unconformity 

Eastover Formation (Claremont Manor Member)

Clay, greenish-gray (5 GY 3/1), silty ...... 15.0 (4.6)

Covered .................................. 50.0 (15.2)

Bottom of the terrace gravels that were quarried here.

 Unconformity 

Old Church Formation

Sand, grayish-olive (10 Y 4/2), fine, quartz, 

partially indurated, somewhat weathered; most aragonitic mollusks leached, 

calcitic forms well preserved (Pycnodonte, Anomia, Pecten) ................. 3.0 (0.9)

89. (USGS Locality 26418) Gravatts Millpond, on Millpond Creek, 

0.9 mile (1.4 km) west of Etna Mills, King William County, 

Va., Hanover 7.5-min quadrangle

Ft (m) 

Covered .................................. 10.0 (3.0)

Eastover Formation (Claremont Manor 

Member)

Clay, grayish-yellow (5 Y 8/4), blocky, silty, 

weathered ............................ 5.0 (1.5)

Sand, grayish-yellow (5 Y 8/4), fine; many 

molds and casts, especially Glossus, 

Turritella ............................ 0.25 (0.08)

Sand, grayish-yellow (4 Y 8/4), weathered, 

fine, clayey ........................... 1.5 (0.5)

Clay, greenish-gray (5 GY 3/1), blocky, silty . 4.0 (1.2) 

Sand, greenish-gray (5 GY 3/1), fine, clayey, 

cobbles and pebbles along base .......... 1.5 (0.5)

 Unconformity 

Calvert Formation

Sand, olive-brown (5 Y 4/4), clayey, phosphatic; fining upward to diatomaceous 

clay; phosphate pebbles along base, fining 

to sand-sized above; phosphatized whale 

bone and vertebrate teeth along base; middle Miocene articulated whale, porpoise, 

and turtle skeletons common near base ... 8.0 (2.4)

 Unconformity 

Old Church Formation(?)

Sandstone, grayish-olive (10 Y 4/2), weathered; large, residual, cobble- to bouldersized concretions occur along contact 

with lower unit ....................... 1.0 (2.4)

 Unconformity 

Nanjemoy Formation (Woodstock Member) 

Sand, olive-black (5 Y 2/1), very fine, silty, 

micaceous, glauconitic; contains carbonaceous material, nuts .................. 1.5 (0.5)
76 STRATIGRAPHY AND MOLLUSKS OF PAMUNKEY GROUP AND OLD CHURCH FORMATION

90. (USGS Locality 26421) Right bank of the Pamunkey River, 0.30 

mile (0.48 km) above Horseshoe, Hanover County, Va., 

Manquin 7.5-min quadrangle

Ft (m) 

Covered .................................. 10.0 (3.0)

Pleistocene(?)

Sand, orange, gravelly, cross-bedded ....... 4.0 (1.2)

 Unconformity 

Eastover Formation (Claremont Manor 

Member)

Sand, greenish-gray (5 GY 5/1), fine to 

medium, silty, clayey, poorly sorted; 

pebbles along contact with burrows extending down into underlying clay; few 

molds of Glossus ...................... 8.0 (2.4)

Clay, greenish-gray (5 GY 5/1), silty and 

sandy near basal contact; grades upward 

into blocky, diatomaceous clay ......... 15.0 (4.6)

 Unconformity 

Calvert Formation

Clay, olive-brown (5 Y 4/4); silty in lower 

10.0 feet (3.0 m), grades to blocky diatomite above, phosphate along lower 

contact ............................. 15.0 (4.6)

 Unconformity 

Old Church Formation (Bed B)

Sand, grayish-olive (5 Y 4/1), clayey, fine; 

partially indurated ..................... 0.8 (0.25)

Piney Point Formation

Sand, olive-gray (5 Y 4/1), clayey, very 

glauconitic, very calcareous owing to 

shell fragments and microfossils ........ 15.0 (4.6)

91. (USGS Locality 26454) Right bank of the Pamunkey River, on 

a bend 0.5 mile (0.8 km) west of Horseshoe, 2.4 miles (3.8 km) 

north of Glimpses Corner, Hanover County, Va., Manquin 

7.5-min quadrangle. Hypostratotype or reference section for 

the Piney Point Formation

Ft (m) 

Eastover Formation (?)

Sand, weathered, grayish-yellow, fine ....... 9.0 (2.7)

Calvert Formation (zones 12-13 of Shattuck, 

1904)

Clay, weathered, light-gray, silty near 

base, becoming blocky above ............ 6.0 (1.8)

Old Church Formation

Sand, weathered, yellowish-gray ........... 0.25 (0.07)

Piney Point Formation (Bed B)

Sand, olive-gray (5 Y 5/1), fine, very calcareous, very glauconitic, weathered and 

leached in upper 10.0 feet (3.0 m); 

burrows containing much glauconite 

extend as much as 2.0 feet (0.6 m) into 

underlying bed ....................... 14.0 (4.2)

Piney Point Formation (Bed A)

Sand, light-olive gray (5 Y 6/1), very 

calcareous, fine; boulder-sized concretions 2.0 feet (0.6 m) from upper contact; 

contact burrowed ...................... 5.1 (1.5)

 Sea Level 

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___1896a, The Potomac River section of the middle Atlantic coast 

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2, p. 11-24.

_____1912, Physiography and geology of the coastal plain province 

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Conrad, T.A., 1843, Description of nineteen species of Tertiary fossils 

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___1847, Observations on the Eocene Formation, and descriptions

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Cope, E.D., 1896, Sixth contribution to the knowledge of the marine

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___1894, Description of the Fredericksburg sheet (Va.-Md.): U.S.

Geological Survey Geological Atlas, Folio 13, p. 1-6. 

___1896, Description of the Nomini quadrangle (Md.-Va.): U.S.

Geological Survey Geological Atlas, Folio 23, p. 1-4. 

___1911, Economic geology of Richmond, Virginia, and vicinity:

U.S. Geological Survey Bulletin 483, p. 1-48. 

___1948, The Marlboro Clay: Economic Geology, v. 43, no. 2,

p. 154-155. 

.1951, Structural relations of Cretaceous and Tertiary formations in parts of Maryland and Virginia: Geological Society of 

America Bulletin, v. 62, p. 745-780.

Dockery, D.T., III, 1980, The invertebrate macropaleontology of the 

Clarke County, Mississippi, area: Mississippi Department of 

Natural Resources, Bureau of Geology, Bulletin 122, p. 1-387.

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Enright, Richard, 1969, The stratigraphy and clay mineralogy of the 

Eocene sediments of the northern New Jersey Coastal Plain, in 

Subitzky, Seymour, ed., Geology of selected areas in New Jersey 

and eastern Pennsylvania and guidebook excursions: New 

Brunswick, N.J., Rutgers University Press, p. 14-20.

Estabrook, James, and Reinhardt, Juergen, 1980, Geology of the Oak 

Grove core, Part 4, Lithologic log of the core: Virginia Division 

of Mineral Resources Publication 20, p. 53-87.

Frederiksen, N.O., 1979, Sporomorph biostratigraphy, northeastern 

Virginia: Palynology, v. 3, p. 129-167.

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Group in the Gulf Province: U.S. Geological Survey Professional 

Paper 189-F, p. 1-215.

Gibson, T.G., 1980, Molluscan and foraminiferal biostratigraphy of 

lower Paleogene strata, in Frey, R.W., ed., Excursions in 

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Niewenhuise, D.S., 1980, Geology of the Oak Grove core, Part 2, 

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Pelecypoda: Bulletins of American Paleontology, v. 2, no. 9, 

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Hazel, J.E., 1968, Ostracodes from the Brightseat Formation (Danian) 

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78 STRATIGRAPHY AND MOLLUSKS OF PAMUNKEY GROUP AND OLD CHURCH FORMATION

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Bulletins of American Paleontology, v. 8, no. 33, p. 5-12.

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in paleontological collections at Cornell University: Bulletins of 

American Paleontology, v. 8, no. 36, p. 349-358.

Van Winkle, Katherine, and Harris, G.K., 1919, New or otherwise interesting Tertiary molluscan species from the East Coast of 

America: Bulletins of American Paleontology, v. 8, no. 33, p. 5-32.

Ward, L.W., and Blackwelder, B.W.,1980, Stratigraphic revision of 

upper Miocene and lower Pliocene beds of the Chesapeake Group, 

middle Atlantic Coastal Plain: U.S. Geological Survey Bulletin 

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Miocene Atlantic Coastal Plain of North Carolina: U.S. 

Geological Survey Bulletin 1457-F, p. 1-23.
PLATES 1-6

Contact photographs of the plates in this report are available, at cost, from 

U.S. Geological Survey Library, Federal Center, Denver, Colorado 80225.
PLATE 1

[Mollusks common in the Piscataway Member of the Aquia Formation. All specimens were collected from the Pamunkey River, 0.5 mile (0.8 km) east of Wickham

Crossing, Hanover County, Va. (Locality 8) (USGS Locality 26337)] 

FIGURE 1, 2, 4, 5. Ostrea alepidota Dall, 1898.

1. Left valve of specimen (USNM 366470); length 73.5 mm, height 85.1 mm.

2. Right valve of specimen (USNM 366470); length 65.4 mm, height 82.6 mm.

4. Left valve of specimen (USNM 366472); length 58.9 mm, height 74.3 mm.

5. Left valve of specimen (USNM 366473); length 36.3 mm, height 44.6 mm. 

3. Turritella humerosa Conrad, 1835.

Apertural view of an incomplete specimen (USNM 366471); height 32.5 mm.

6. Turritella mortoni Conrad, 1830.

Apertural view of an incomplete specimen (USNM 366474); height 35.8 mm.

7. Cucullaea gigantea Conrad, 1830.

Left valve of specimen (USNM 366475); length 42.4 mm, height 27.4 mm.

8. Pitar pyga Conrad, 1845.

Left valve of a double-valved specimen (USNM 366476); length 46.3 mm, height 38.9 mm.

9. Crassatellites capricranium (Rogers, 1839).

Left valve of specimen (USNM 366477); length 59.1 mm, height 38.6 mm.

10. Dosiniopsis lenticularis (Rogers, 1839).

Left valve of specimen (USNM 366478); length 47.1 mm, height 44.5 mm.
U.S. GEOLOGICAL SURVEY PROFESSIONAL PAPER 1346 PLATE 1

OSTREA ALEPIDOTA, TURRITELLA HUMEROSA, TURRITELLA MORTONI, CURULLAEA GIGANTEA, 

PITAR PYGA, CRASSATELLITES CAPRICRANIUM, DOSINIOPSIS LENTICULARIS
PLATE 2

[Mollusks common in the Paspotansa Member of the Aquia Formation. All except figure 5 were collected from the Potomac River, 0.3 mile (0.5 km) above

Belvedere Beach, King George County, Va. (Locality 30)] 

FIGURE 1. Cucuttaea gigantea Conrad, 1830.

Left valve of specimen (USNM 366479); length 83.3 mm, height 71.8 mm.

2. Pycnodonte sp.

Left valve of specimen (USNM 366480); length 74.2 m, height 74.6 mm.

3. Turritella mortoni Conrad, 1830.

Apertural view of specimen (USNM 366481); height 105.0 mm. 

4, 8. Ostrea sinuosa Rogers and Rogers, 1837.

4. Left valve of specimen (USNM 366482); length 152.8 mm, height 134.3 mm. 

8. Right valve of specimen (USNM 366482); length 98.8 mm, height 118.3 mm.

5. Venericardia regia Conrad, 1865.

Left valve of specimen (USNM 366483) from the Potomac River 0.1 mile (0.3 km) below the mouth of Passapatanzy 

Creek, King George County, Va. (Locality 12) (USGS Locality 26341); length 75.4 mm, height 71.7 mm.

6. Turritella mortoni Conrad, 1830.

Apertural view of nearly complete specimen (USNM 366484); height 92.3 mm.

7. Crassatellites alaeformis Conrad, 1830.

Right valve of specimen (USNM 366485); length 51.9 mm, height 22.7 mm. 

9. Pi tar pyga Conrad, 1845.

Right valve of specimen (USNM 366486); length 33.6 mm, height 28.1 mm. 

10. Turritella humerosa Conrad, 1835.

Apertural view of an incomplete specimen (USNM 366487); height 49.8 mm.
U.S. GEOLOGICAL SURVEY PROFESSIONAL PAPER 1346 PLATE 2

10

CUCULLAEA GIGANTEA, PYCNODONTE sp., TURRITELLA MORTONI, OSTREA SINUOSA VENERICARDIA 

REGIA, CRASSATELLITES ALAEFORMIS, PITAR PYGA, TURRITELLA HUMEROSA
PLATE 3

[Mollusks common in the Potapaco Member of the Nanjemoy Formation. Figures 1, 3, and 5 from the Pamunkey River, 0.8 mile (1.3 km) below Hanovertown, 

Hanover County, Va. (Locality 48) (USGS Locality 26377). Figures 2, 4, and 6 from the Pamunkey River, 0.45 mile (0.72 km) above the mouth of Millpond 

Creek on the right bank, Hanover County, Va. (USGS Locality 26424). Figures 7-9, 11, and 12 from the Potomac River, 2.3 miles (3.9 km) above Popes 

Creek, Charles County, Md. (USGS Locality 26425). Figure 10 from the Rappahannock River, opposite Goat Island, Caroline County, Va. (Locality 31) 

(USGS Locality 26360)]

FIGURE 1. Cubitostrea sp.

Left valve of specimen (USNM 366488); length 48.5 mm, height 51.6 mm.

2. Cubitostrea sp.

Left valve of specimen (USNM 366489); length 35.7 mm, height 50.4 mm.

3. Cubitostrea sp.

Left valve of specimen (USNM 366490); length 37.7 mm, height 58.5 mm.

4. Cubitostrea sp.

Left valve of specimen (USNM 366491); length 18.7 mm, height 27.6 mm.

5. Cubitostrea sp.

Right valve of specimen (USNM 366492); length 47.9 mm, height 56.2 mm.

6. Cubitostrea sp.

Right valve of specimen (USNM 366493); length 18.8 mm, height 21.4 mm.

7. Venericardia potapacoensis Clark and Martin, 1901.

Left valve of specimen (USNM 366494); length 29.0 mm, height 24.1 mm.

8. Nuculana parva (Rogers, 1837).

Right valve of specimen (USNM 366495); length 4.62 mm, height 2.85 mm.

9. Vokesula sp.

Right valve of specimen (USNM 366496); length 4.48 mm, height 4.20 mm.

10. Lucina sp.

Right valve of specimen (USNM 366497); length 5.14 mm, height 4.66 mm.

11. Vokesula sp.

Right valve of specimen (USNM 366498); length 4.29 mm, height 3.65 mm.

12. Cadulus sp.

Lateral view of incomplete specimen (USNM 366499); length 3.45 mm.
U.S. GEOLOGICAL SURVEY PROFESSIONAL PAPER 1346 PLATE 3

-- / ;*/ J

*-....«.:>V'f

10

CUBITOSTREA sp., VENERICARDIA POTAPACOENSIS, NUCULANA PARVA, 

VOKESULA sp., LUCINA sp., CADULUS sp.
PLATE 4

[Mollusks common in the Woodstock Member of the Nanjemoy Formation. Figures 5, 6, and 10-14 from the Pamunkey River, in a small ravine, 0.63 mile 

(1.01 km) south-southeast of the mouth of Totopotomoy Creek, Hanover County, Va. (Locality 74) (USGS Locality 26403). Other localities are as described below] 

FIGURE 1. Glycymeris sp.

Right valve of specimen (USNM 366500) from the Pamunkey River at the termination of Rte. 732, Hanover County,

Va. (Locality 64) (USGS Locality 26393); length 22.0 mm, height 21.0 mm.

2-4. Specimens from the Potomac River, 0.95 miles (1.53 km) below the mouth of Popes Creek, Charles County, Md. (Locality 

68) (USGS Locality 26397).

2. Cubitostrea sp.

Left valve of specimen (USNM 366501); length 13.8 mm, height 20.2 mm.

3. Cubitostrea sp.

Left valve of specimen (USNM 366502); length 11.8 mm, height 17.0 mm.

4. Cubitostrea sp.

Right valve of specimen (USNM 366503); length 12.0 mm, height 22.0 mm.

5. Nuculana sp.

Right valve of specimen (USNM 366504); length 4.14 mm, height 2.56 mm.

6. Macrocallista subimpressa (Conrad, 1848).

Left valve of specimen (USNM 366505); length 21.3 mm, height 13.9 mm.

7-9. Specimens from the Pamunkey River, just upstream of the old Newcastle Bridge, Hanover County, Va. (Locality 76) 

(USGS Locality 26405).

7. Corbula aldrichi Meyer, 1885.

Right valve of specimen (USNM 366506); length 10.0 mm, height 7.5 mm.

8. Venericardia ascia Rogers and Rogers, 1839.

Right valve of specimen (USNM 366507); length 41.4 mm, height 37.5 mm.

9. Venericardia ascia Rogers and Rogers, 1839.

Right valve of specimen (USNM 366508); length 62.6 mm, height 54.1 mm.

10. Lucina dartoni Clark, 1895.

Left valve of specimen (USNM 366509); length 6.1 mm, height 5.2 mm.

11. Lunatia sp.

Apertural view of specimen (USNM 366510); height 14.2 mm.

12. Turritella sp.

Apertural view of incomplete specimen (USNM 366511); height 12.2 mm.

13. Turritella sp.

Apertural view of incomplete specimen (USNM 366512); height 14.4 mm.

14. Cadulus sp.

Lateral view of nearly complete specimen (USNM 366513); height 4.93 mm.
U.S. GEOLOGICAL SURVEY PROFESSIONAL PAPER 1346 PLATE 4

GLYCYMERIS sp., CUBITOSTREA sp., NUCULANA sp., MACflOCALL/STA SUBIMPRESSA, CORBULA 

ALDRICHI, VENERICARDIA ASCIA LUCINA DARTONI, LUNATIA sp., TURRITELLA sp., CADULUS
PLATE 5

[Mollusks common in the Piney Point Formation. Figures 1-3, 8-19, and 21 from the Pamunkey River, 1.0 mile (1.6 km) west of Horseshoe, Hanover County, 

Va. (USGS Locality 26427). Figures 4 and 20 from the Pamunkey River at the termination of Rte. 732, Hanover County, Va. (USGS Locality 26426). Figures 

5-7 from the Pamunkey River at Horseshoe, Hanover County, Va. (Locality 83) (USGS Locality 26412)]

FIGURE 1. "Pecten" sp.

Right valve of specimen (USNM 366514); length 15.0 mm, height 15.8 mm.

2. "Pecten" sp.

Right valve of specimen (USNM 366515); length 7.1 mm, height 7.6 mm.

3. "Pecten" sp.

Right valve of specimen (USNM 366516); length 11.7 mm, height 12.4 mm. 

4-6, 8, 9. Cubitostrea sellaeformis (Conrad, 1832).

4. Left valve of a double-valved individual (USNM 366517); length 110.9 mm, height 99.7 mm.

5. Left valve of specimen (USNM 366518); length 77.7 mm, height 76.3 mm.

6. Right valve of specimen (USNM 366519); length 70.7 mm, height 82.3 mm.

8. Left valve of specimen (USNM 366521); length 16.1 mm, height 24.2 mm.

9. Left valve of specimen (USNM 366522); length 11.1 mm, height 19.7 mm. 

7. Plicatula filamentosa Conrad, 1833.

Right valve of incomplete specimen (USNM 366520); length 10.5 mm, height 9.2 mm.

10. Anomia lisbonensis (Aldrich, 1886).

Left valve of specimen (USNM 366523); length 17.5 mm, height 19.4 mm.

11. Leda coelatella Van Winkle, 1919.

Left valve of specimen (USNM 366524); length 15.3 mm, height 6.8 mm.

12. Leda semen Lea, 1833.

Right valve of specimen (USNM 366525); length 11.2 mm, height 5.8 mm.

13. Glycymeris lisbonensis Harris, 1919.

Right valve of specimen (USNM 366526); length 18.5 mm, height 16.9 mm. 

14, 15. Anapteris regalis Van Winkle, 1919.

14. Left valve of specimen (USNM 366527); length 15.5 mm, height 8.5 mm.

15. Left valve of specimen (USNM 366528); length 14.5 mm, height 7.6 mm.

16. Venericardia rotunda Lea, 1833.

Left valve of specimen (USNM 366529); length 14.5 mm, height 14.0 mm.

17. Turritella nasuta Gabb, 1860.

Apertural view of incomplete specimen (USNM 366530); height 11.1 mm.

18. Dentalium sp.

Lateral view of specimen (USNM 366531); height 11.4 mm.

19. Dentalium sp.

Lateral view of specimen (USNM 366532); height 9.2 mm.

20. Corbula sp.

Right valve of specimen (USNM 366533); length 8.7 mm, height 5.5 mm.

21. Caestocorbula fossata (Meyer and Aldrich, 1886).

Right valve of specimen (USNM 366534); length 6.9 mm, height 4.6 mm.
U.S. GEOLOGICAL SURVEY PROFESSIONAL PAPER 1346 PLATE 5

21

'PECTEN" sp., CUBITOSTREA SELLAEFORMIS, PLICATULA FILAMENTOSA, ANOMIA LISBONENSIS,

LEDA COELATELLA, LEDA SEMEN, GLYCYMERIS, ANAPTERIS REGALIS, TURRITELLA NASUTA,

DENTALIUM sp., CORBULA sp., CAESTOCORBULA FOSSATA
PLATE 6

[Mollusks common in the Old Church Formation. All specimens from the Warren Brothers sand pit, 1.4 miles (2.3 km) southeast of Bottoms Bridge, Henrico

County, Va. (Locality 88) (USGS Locality 26417)] 

FIGURE 1-3. Pycnodonte sp.

1. Left valve of specimen (USNM 366535); length 80.9 mm, height 66.7 mm.

2. Left valve of specimen (USNM 366536); length 53.9 mm, height 57.0 mm.

3. Right valve of specimen (USNM 366535); length 60.2 mm, height 59.2 mm.

4. Anomia ruffini Conrad, 1843.

Left valve of specimen (USNM 366537); length 49.5 mm, height 47.7 mm.

5. "Pecten" sp.

Right valve of specimen (USNM 366538); length 11.5 mm, height 12.3 mm.

6. "Pecten" seabeensis Richards, 1947.

Right valve of specimen (USNM 366539); length 11.3 mm, height 11.5 mm.

7. Bicorbula idonea (Conrad, 1833).

Latex cast of right valve (USNM 366540); length 23.9 mm, height 18.7 mm.

8. Mercenaria gardnerae Kellum, 1926.

Latex cast of right valve (USNM 366541); length 44.5 mm, height 38.4 mm.

9. Lucina sp.

Internal mold of left valve (USNM 366542); length 30.7 mm, height 25.7 mm.

10. Lucina sp.

Latex cast of hinge area of double-valved individual (USNM 366543); length 36.4 mm.

11. Isognomon sp.

Partial external mold of right valve (USNM 366544); length 87.4 mm, height 56.0 mm.

12. Ecphora sp.

Latex cast of incomplete specimen (USNM 366545); height 16.6 mm.

13. Panopea sp.

Internal mold of left valve of specimen (USNM 366546); length 45.6 mm, height 30.1 mm.

14. Plicatula sp.

Exterior view of a fragment (USNM 366547); length 11.6 mm, height 11.2 mm.

15. Plicatula sp.

Exterior view of a fragment (USNM 366548); length 16.0 mm, height 15.1 mm.

16. Cyclocardia sp.

Latex cast of right valve of specimen (USNM 366549); length 15.3 mm, height 15.9 mm.
U.S. GEOLOGICAL SURVEY PROFESSIONAL PAPER 1346 PLATE 6

V)

14

PYCNODONTE sp., ANOMIA RUFFINI, "PECTEN" sp., "PECTEN" SEABEENSIS, BICORBULA IDONEA, 

MERCENARIA GARDNERAE, LUCINA sp., ISOGNOMON sp., ECPHORA sp., PANOPEA sp., PLICATULA

sp., CYCLOCARDIA sp.