Tf-^1 T^l 1 -C* T * *.\ 1 he Par sons burg Sand in the 

Central Belmarva Peninsula, 

Maryland and Delaware

GEOLOGICAL SURVEY PROFESSIONAL PAPEH 1067-B
The Parsonsburg Sand in the 

Central Delmarva Peninsula, 

Maryland and Delaware

By CHARLES S. DENNY, JAMES P. OWENS, LESLIE A. SIRKIN, 

and MEYER RUBIN

SURFACE AND SHALLOW SUBSURFACE GEOLOGIC STUDIES IN THE 

EMERGED COASTAL PLAIN OF THE MIDDLE ATLANTIC STATES

GEOLOGICAL SURVEY PROFESSIONAL PAPER 1067-B

Sandy and peaty sediments 

suggest that the climate 

of the Delmarva Peninsula 

was cooler and drier 

during the late Wisconsin 

than it is at present

UNITED STATES GOVERNMENT PRINTING OFFICE, WASHINGTON : 1979
UNITED STATES DEPARTMENT OF THE INTERIOR 

CECIL D. ANDRUS, Secretary

GEOLOGICAL SURVEY

H. William Menard, Director

Library of Congress Cataloging in Publication Data

Main entry under title:

The Parsonsburg Sand in the central Delmarva Peninsula, Maryland and Delaware.

(Surface and shallow subsurface geologic studies in the emerged coastal plain of the Middle Atlantic States) (Geological Survey

professional paper; 1067-B) 

Bibliography: p. 

Includes Index.

Supt. of Docs, no.: I 19.16:1067-B 

1. Geology, Stratigraphic Pleistocene. 2. Glacial epoch Delmarva Peninsula. I. Denny, Charles Storrow, 1911- II. Series.

III. Series: United States. 

Geological Survey. Professional paper; 1067-B.

QE697.P19 551.792 77-608323

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

Washington, B.C. 20402

Stock Number 024-001-03192-2
CONTENTS

Geographic and geologic setting —— 

Acknowledgments

Distribution and lithology 

Microflora

Thickness and stratigraphic relationsSurface expression

Origin

In the valleys 

On the uplands

References cited

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ILLUSTRATIONS

FIGURE 1. Generalized geologic map of part of central Delmarva Peninsula, Del., Md., and Va,—————————————————

2. Ternary diagram showing light-mineral distribution in several formations, central Delmarva Peninsula——————

3. Ternary diagram showing heavy-mineral distribution in several formations, central Delmarva Peninsula ——————

4. Map of Parsonsburg Sand east and south of Salisbury, Md., showing materials penetrated in auger and drill holes •

5. Cross section of Parsonsburg Sand on divide north of Parsonsburg, Md —————————————————————————•

6. Sketches showing bedding in Parsonsburg Sand north of Parsonsburg, Md ———————————————————————•

7. Sketches showing crossbedding and deformed beds in Parsonsburg Sand north of Parsonsburg, Md—————————-

8. Maps showing Parsonsburg Sand on uplands east and south of Salisbury, Md——————————————————————

9. Cross section of Parsonsburg Sand on upland north of Parsonsburg, Md—————————————————————————

10. Cross sections of Parsonsburg Sand near Snow Hill and near Powellville, Md —————————————————————

Page

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TABLES

TABLE 1. Section of the Parsonsburg Sand exposed in borrow pit on divide north of Parsonsburg, Md—————

2. Presence or absence of arboreal and nonarboreal pollen in 24 samples of the Parsonsburg Sand ———

3. Radiocarbon age determinations on samples from the Parsonsburg Sand and adjacent formations——

B8 

10 

13

ill
SURFACE AND SHALLOW SUBSURFACE GEOLOGIC STUDIES IN THE 

EMERGED COASTAL PLAIN OF THE MIDDLE ATLANTIC STATES

THE PARSONSBURG SAND IN THE

CENTRAL DELMARVA PENINSULA,

MARYLAND AND DELAWARE

By CHARLES S. DENNY, JAMES P. OWENS, LESLIE A. SIRKIN, and MEYER RUBIN

ABSTRACT

The Parsonsburg Sand, a surface sand largely of Wisconsin age, caps 

terraces east of some of the major streams and mantles broad areas on 

the uplands of the central Delmarva Peninsula, Maryland and Delaware. The main body of the formation east and south of Salisbury, Md., 

ranges from 1.25 to 6.00 m (4-20 ft) in thickness and is a mediumgrained moderately feldspathic sand containing a relatively mature 

heavy-mineral suite. The sand is either stratified or massive, and in 

some areas contains peaty sand and silt-clay, typically at or near the 

base of the formation. The organic matter ranges in radiocarbon age 

from about 30,000 to about 13,000 years B.P. and contains microfloral 

assemblages suggesting that at the time the sand was deposited the 

climate was cooler and drier that it is at present. The region may have 

been a pine-birch barrens in which were small ponds, spruce bogs, and 

abundant shrubs. The distribution of the sand at or near the position of 

high stands of the Sangamon sea suggests that the Parsonsburg Sand 

was derived from sandy shore and nearshore deposits of Sangamon 

age. Deposition was in part eolian and in part fluvial and lacustrine, 

probably in small streams and ponds between sand dunes.

INTRODUCTION

The central Delmarva Peninsula in southern Delaware 

and adjacent Maryland (fig. 1) is covered by a surficial 

blanket of sand—the Parsonsburg Sand—that yields data 

about the environment of the central Atlantic Coastal 

Plain in middle and late Wisconsin time. The sand ranges 

in radiocarbon age from about 30,000 to about 13,000 

years B.P. For two-thirds of this interval, including the 

maximum advance of the last ice sheet onto Long Island 

about 18,000-20,000 radiocarbon years ago, the record 

heretofore has been limited to a few isolated radiocarbon 

dates. A fairly complete record of the late Wisconsin is 

found on the central Delmarva Peninsula, about 250 km 

(160 mi) south of the terminal moraine of the Wisconsin 

ice sheet. Fluvial, eolian, and lacustrine sediments contain an extensive microflora that suggests a cooler and 

slightly drier climate at the time of deposition than at 

present. The region may have been a pine barrens that

'Adelphi University, Garden City, N. Y. 11530.

had abundant shrubs and small ponds between isolated 

sand dunes.

The name Parsonsburg Sand was applied by Rasmussen and Slaughter (1955, p. 118) to a "*** veneer of sand 

and associated deposits which compose the rims and, in 

places, the interior of the Maryland basins." The "basins" were defined by Rasmussen (1953, 1958; Rasmussen and Andreasen, 1959) as groups of more or less 

circular poorly drained basins bordered by low sandy 

ridges. The formation was named for the village of Parsonsburg about 9.6 km (6 mi) east of Salisbury, Md. The 

sand was believed to extend from below sea level to the 

crest of the divide near Parsonsburg and to be of Wisconsin age. Hansen (1966, p. 22) believes that some of 

the sand formed at the end of the Sangamon Interglaciation "as a submarine bar which later developed into 

an emergent sand spit capped by dune deposits."

In southern Delaware, the surficial sands have been 

studied in detail by Jordan (1964, 1967, 1974; Jordan and 

Talley, 1976), who believes that the sandy ridges are 

beaches or bars whose surface has been reworked by the 

wind.

As part of the Delmarva project, a study by the U.S. 

Geological Survey of the surface and shallow subsurface 

geology of the central Delmarva Peninsula, many auger 

borings were made not only in the Parsonsburg Sand as 

originally defined in Worcester, Wicomico, and Somerset 

Counties, Md., but also in areas to the north in both 

Maryland and Delaware. We have found that a surficial 

mantle of sand is present in many upland areas. The sand 

may form dunes or it may be a discontinuous sheet without any distinctive surface morphology. It rests on deposits of both Pleistocene and late Tertiary age and, in 

many areas, lacks any sediment rich in organic matter or 

other fossil materials. The sand has a complex origin and 

may include beds as old as the Pliocene and as young as 

the Holocene.

Bl
B2 GEOLOGIC STUDIES IN EMERGED COASTAL PLAIN OF MIDDLE ATLANTIC STATES

75°45' 75°00'

38°45

38*00!

~?^m'A+i&$$.

^:#vj£^\'ii£PS3

15'

FIGURE 1.—Generalized geologic map of part of the central Delmarva Peninsula, Del., Md., and Va.
PARSONSBURG SAND IN CENTRAL DELMARVA PENINSULA B3

We use the name Parsonsburg Sand for this surficial 

mantle regardless of whether or not it contains diagnostic material (pollen or peaty sediment dateable by radiocarbon) because we are unable to separate sand known 

to be of late Wisconsin age from sand that could be older 

or younger.

Our study in southern Maryland and adjacent Delaware shows that the Parsonsburg Sand is found in two 

topographic situations: it forms parabolic dunes on the 

east side of the valleys of some of the rivers, such as the 

Nanticoke, Wicomico, and Pocomoke (fig. 1), and it blankets large areas on the uplands in the central part of the 

peninsula. In some upland areas, the surface of the sand 

is heaped up into dunes separated by shallow poorly 

drained depressions; in other upland areas, the surface is 

level to gently rolling. Sediment rich in organic matter is 

found in the Parsonsburg Sand in some upland areas such

as that east and south of Salisbury, Md. (fig. 1). On the 

other hand, on the uplands northwest of Salisbury between the Wicomico and Nanticoke Rivers, an extensive 

blanket of Parsonsburg Sand is barren; it contains no 

peaty sediments or any other fossil materials. Along the 

rivers, the Parsonsburg Sand contains sediment rich in 

organic matter at only one or two localities. The deposition of the sand in the two upland areas mentioned above 

and along the rivers may or may not have been contemporaneous.

In this paper, we describe the Parsonsburg Sand in the 

valleys of the Nanticoke, Wicomico, and Pocomoke Rivers and in the uplands east and south of Salisbury, Md. 

The uplands include the type area of Rasmussen and 

Slaughter (1955) on the divide near Parsonsburg between Salisbury and Ocean City, Md. On the uplands, 

the Parsonsburg Sand commonly consists of an upper

EXPLANATION

Wisconsin <

Sangamon

Kent Island Formation

(Indudes swamp and tidal

marsh deposits)

Parsonsburg Sand

(Indudes Atlantic

barrier sand)

a 

1

Q

Pensauken Formation

Contact

Localities 1-5 are sample sites 

and are keyed to quadrangle 

name and field number below

1 Burrsvilfe 2

2 Federalsburg 4

3 Chfcamacomico 1

4 Mardela Springs 13

5 Kingston 12

FIGURE 1. — Continued.
B4 GEOLOGIC STUDIES IN EMERGED COASTAL PLAIN OF MIDDLE ATLANTIC STATES

light-colored sand (pale yellow to brown) and a lower 

dark-colored sand or clay silt (light brown to dark gray) 

rich in organic matter.

The paper is based on observations in a few borrow 

pits and of samples from about 60 auger holes. Here we 

discuss the nature and origin of the Parsonsburg Sand. 

Sirkin and others (1977) have described the microfloral 

assemblages, and Denny and Owens (1978) have discussed the surface morphology. (See also Hess, 1977.)

GEOGRAPHIC AND GEOLOGIC SETTING

The Delmarva Peninsula is a broad upland, generally 

not more than 24 m (80 ft) above sea level except at its 

extreme northern end. The peninsula is bordered by 

wetlands that separate it from Chesapeake Bay to the 

west and the Delaware Bay and Atlantic Ocean to the 

east. An extensive barrier-backbarrier system forms the 

Atlantic shore. The sediments that directly underlie the 

central and northern parts of the peninsula form a sheet 

of interbedded and interfingered sand and gravel. These 

alluvial and marginal marine sediments were deposited 

in a broad valley in Miocene and Pliocene time. Presumably the valley was bordered by uplands of low relief that 

have since been eroded away to form Delaware and 

Chesapeake Bays. The formations adjacent to the Parsonsburg Sand, which are, therefore, possible source 

rocks for the Parsonsburg Sand are described below. 

(See also Owens and Denny, 1978.)

The Pensauken Formation, late Miocene in age, is a 

fluvial deposit consisting of orange to reddish-brown 

sand and gravelly sand. The unit is a feldspathic quartz 

sand (fig. 2.), the heavy-mineral assemblages being immature, notably hornblende rich (fig. 3). The Beaverdam 

Sand, Pliocene in age, is principally light-colored gravelly sand and interbedded clay-silt beds. The sands are 

highly feldspathic and contain a moderately mature suite 

of heavy minerals. The Beaverdam was deposited in a 

marginal marine environment.

The Walston Silt, of probably late Pliocene age, underlies the highest part of the central Delmarva Peninsula. The unit is a deeply weathered sequence of interbedded clay, silt, and sand. The clay-silt fraction 

contains a disordered kaolinite that is probably detrital 

rather than secondary. Halloysite and gibbsite are present in the upper weathered strata. In the weathered 

zone there is a mature suite of heavy minerals; below the 

weathered zone, the heavy-mineral suite is less mature 

but more so than in the underlying Beaverdam Sand. 

The Walston Silt is the oldest unit in the Delmarva Peninsula that probably is part of a barrier-backbarrier sequence. The formation suggests a marine high-stand 

about 21 m (70 ft) above present sea level. The Omar 

Formation of Sangamon age, extending southward into

QUARTZ

PLAGIOCLASE

EXPLANATION

Holocene barrier 

Parsonsburg Sand

 Upland east and south of Salisbury, Md.

» Along Nanticoke River

A Along Pocomoke River 

Sinepuxent Formation 

Ironshire Formation 

Omar Formation

Walston Silt (Samples from weathered zone) 

Beaverdam Sand 

Pensauken Formation

FIGURE 2.—Ternary diagram showing light-mineral distribution (<2.80 

sp gr; 0.149-0.074 mm diam) in the Parsonsburg Sand and adjacent 

formations in the central part of the Delmarva Peninsula (fig. 1).

the Accomac trough in Virginia, is interbedded dark-colored clay-silt and light-colored sand, primarily part of a 

barrier-backbarrier system. The clay-sized clasts are kaolinite, montmorillonite, illite, and chlorite. The heavymineral assemblages are immature (abundant hornblende, epidote, and garnet). The clay-silt facies reaches 

altitudes of nearly 10.6 m (35 ft) above sea level. The 

sand facies resembles the Parsonsburg Sand, making it 

difficult to establish the maximum elevation of the Sangamon sea that may have stood as much as 17.0 m (55 

ft) above present sea level.

ACKNOWLEDGMENTS

On behalf of the Delmarva project, it is a pleasure to 

acknowledge the assistance of the Maryland Geological 

Survey, K. N. Weaver, Director, and the Delaware Geological Survey, R. R. Jordan, Director, and the staffs of 

both Surveys. Several members of the U.S. Department 

of Agriculture aided the study in various ways, especially Klaus Flack, R. L. Hall, Ray Daniels, and Paul 

Siegrist. Grace Brush, C. B. Hunt, and L. C. Peltier visited the area and offered helpful suggestions.
PARSONSBURG SAND IN CENTRAL DELMARVA PENINSULA B5

ZIRCON

TOURMALINE

RUTILE

HORNBLENDE

EPIDOTE

GARNET

ACTINOLITE

TREMOLITE

EXPLANATION

® Holooane barrier 

Parsonsburg Sand

+ Upland east and south of Salisbury, Md.

9 Along Nanticoke River

A Along Pocomoke River 

C3 Sinepuxent Formation 

D Ironshire Formation 

X Omar Formation

O Walston Silt (Samples from weathered zone) 

+ Beaverdam Sand 

 Pensauken Formation

FIGURE 3.—Ternary diagram showing heavy-mineral distribution 

(>2.80 sp gr; 0.149-0.074 mm diam) in the Parsonsburg Sand and 

adjacent formations in the central part of the Delmarva Peninsula 

(fig. 1). Note general tendency of the Parsonsburg Sand to have a 

higher zircon-tourmaline-rutile concentration than do all the underlying formations except the Walston.

Finally, our thanks to our colleagues in the U.S. Geological Survey—to M. J. Grolier, J. T. Hack, W. S. Kirk, 

R. B. Mixon, William Raspet, R. S. Sigafoos, and the 

late Karl Stefansson for discussions and for assistance in 

the field, and to J. A. Wolfe for some preliminary palynological investigations.

DISTRIBUTION AND LITHOLOGY

The distribution and type of material found in the main 

body of the Parsonsburg Sand on the uplands east and 

south of Salisbury, Md., are presented in figure 4. The 

individual columnar sections illustrate the relationship of 

the upper sand to the underlying peaty sediments and to 

the older formations that underlie the Parsonsburg.

In general, most of the sand fraction in the Parsonsburg is medium grained and light colored (pale yellow to 

brown). The sand grains are in general subrounded to 

well rounded. Sand in the Parsonsburg appears to have 

a lower feldspar content than sand in most of the other

formations in the region (fig. 2). The heavy-mineral assemblages in the Parsonsburg are also more mature than 

those in the adjacent formations except for the Walston 

(fig. 3).

The clay-silt fraction in the upper sand ranges from 

about 0.2 to 3.0 percent and was X-rayed to determine 

its mineralogy. The major minerals are dioctahedral vermiculite and kaolinite. Smaller amounts of gibbsite, halloysite, illite, and montmorillonite are also present; the 

last two minerals are increasingly abundant near the upper surface of the formation. Basically, the mineralogy 

of the clay-silt fraction is dominated by minerals that are 

stable in well-drained (leached) deposits.

The clay mineralogy of the basal peaty sediments of 

the Parsonsburg, however, is much less mature than it is 

in the upper sand. Kaolinite is the major mineral present, but montmorillonite and chlorite (+ chloritized vermiculite) are much more abundant. Small amounts of 

gibbsite and halloysite are also present in the basal peaty 

sediments.

The mineralogy of the sand both in the upper part of 

the formation and in the basal peaty sediments indicates 

derivation of sediment from an already leached source 

such as weathered sand in the Beaverdam Sand or Walston Silt, which are beneath or adjacent to the Parsonsburg Sand. The high concentration of montmorillonite in 

the peaty sediments could be interpreted as a product of 

diagenesis, much as postulated by Jackson (1965). He 

suggested that aluminated clays could be transformed to 

montmorillonite in the swampy environment indicated 

by the peaty sediments.

The only extensive exposure of the Parsonsburg Sand 

was a large borrow pit on the divide north of Parsonsburg, Md. (Pittsville 172, fig. 4) described in detail below. 

It was also the only exposure of the peaty sediment. In 

the pit, about 1.5 m (5 ft) of peaty sand and clay-silt is 

overlain by about 3 m (10 ft) of bedded sand. In places, 

the bedded sand is overlain by 1-2 m (3-6 ft) of loose 

sand forming a low ridge, probably part of an ancient 

sand dune (fig. 5; table 1). Beds of coarse to fine sand 

are present inte'rbedded with a few lenses of coarse sand 

and granules. In places, lenses of very fine gravel range 

in thickness from about 0.1 to 10.0 cm (0.04^4.0 in.); 

some are about one grain thick.

The internal structure of the material exposed in the 

borrow pit suggests deposition by currents in standing 

water (figs. 6 and 7). The stratification is horizontal to 

slightly inclined (fig. 6A). Many of the horizontal beds 

are slightly undulating. Ripple marks are absent. One 

sequence of beds may be disconformable on the adjacent 

sequence (fig. 6B). In the borrow pit, in the lower part

-The borrow pit and drill holes are located in figure 4 by quadrangle name and number.
B6

75°45'

GEOLOGIC STUDIES IN EMERGED COASTAL PLAIN OF MIDDLE ATLANTIC STATES

30' 75°15'

38°30'

22'30"

38°07'30"

llfllfllfiSS

FIGURE 4.—Map of Parsonsburg Sand in area east and south of Salisbury, Md. Columnar sections show materials found in drill holes.

of unit 2 (fig. 5), small-scale crossbedding (fig. 7A) includes lenses containing abundant dark-mineral grains. 

On the north wall of the borrow pit (Pittsville 17) the 

sand directly overlying the basal peaty sediment is deformed (fig. 7B). Beds of fine sand containing thin clay

laminae near the base overlie peaty fine sand and claysilt. The beds are symmetrically folded, the axes being 

more or less vertical. Some of the clay laminae are broken. The deformed beds are cut off above by an essentially horizontal surface on which rests medium sand a
PARSONSBURG SAND IN CENTRAL DELMARVA PENINSULA B7

EXPLANATION

Parsonsburg Sand

Largely Wisconsin with perhaps

some lower Holocene

Columnar section showing materials found in drill holes and borrow pits

20,490±500-1-P 

b

Sand Slt-day Sediment containing 

organic matter

20,490±500

Radiocarbon age of sediment sample containing 

organic matter, in years before present

PPine, birch, alder, and spruce dominate the 

pollen spectra (Sirkin and others, 1977)

Geologic Units

k, Kent Island Formation (Sangamon) 

o, Omar Formation (Sangamon) 

w, Walston Sit (Pliocene) 

b, Beaverdam Sand (Pliocene)

Borrow pit Drill hole 

Numbers refer to localities in named quadrangles

x Cg38

Drillholes

Data taken from Ramussen andSlaughter (1955), 

Ramussen andAndreasen (1959), and Hansen (1966)

Plttsvaie0

Where underlined, the names of cities, towns, or 

physical features are also the names of quadrangles

Contact

FIGURE 4.—Continued.

few inches thick overlain conformably by sand containing 

thin wavy laminae of organic matter. Horizontally bedded sand overlies the peaty sand layer. The section suggests deformation, erosion, and deposition, perhaps related to changes in the level of the surface of the pond 

in which the sediments were deposited.

MICROFLORA

The microflora in layers of peaty sediment, at or near 

the base of the formation (fig. 4) has been described by 

Sirkin and others (1977) on the basis of examination of 

samples from auger holes and from the large borrow pit 

north of Parsonsburg (Pittsville 17). Pine, spruce, birch, 

alder, grass, sedge, and the composites are present in at 

least 20 of the 24 samples of the Parsonsburg Sand that 

have been analyzed; heaths (Ericaceae) are present in 14 

of the samples, and willow, oak, and Rosaceae, in 11 of

w 

ALTrruoe.

IN METERS

25-

20-

15-

23,300±

30i560±75<r CLAY (WALSTON SILT)

100 200 300

I

400 METERS

500 1000 FEET

FIGURE 5.—The Parsonsburg Sand on divide north of Parsonsburg, Md. Generalized cross section of the material exposed in 

borrow pit about 2.8 km (1.7 mi) north of Parsonsburg (Pittsville 17, fig. 4). Units 1, 2, and 3 are described in table 1. Ages 

of samples dated by radiocarbon are given in years B.P. Vertical exaggeration x 40.

the samples (table 2). For a detailed account of the microflora, the reader should consult Sirkin and others 

(1977). The microfloral assemblages dated by radiocarbon suggest that from about 30,000 years B.P. to about 

13,000 years B.P., the climate of the central Delmarva 

Peninsula was cooler and drier that it is at present. The 

area may have been a pine-birch barrens similar in part 

to the New Jersey pine barrens or to the Pocono Plateau 

in northeastern Pennsylvania. Shrubs were abundant, 

and there were small ponds and bogs containing spruce.

THICKNESS AND STRATIGRAPHIC 

RELATIONS

The Parsonsburg Sand on the uplands east and south 

of Salisbury, Md., ranges in thickness from about 1.25 

to 6.00 m (4-20 ft); the mean value is about 4 m (13 ft). 

The formation is thicker in the type area north of Parsonsburg and in a belt running northeast through Pittsville than it is in much of the remainder of the uplands 

(fig. 8A). The base of the formation is at about 18 m (60 

ft) above sea level in the type area north of Parsonsburg 

(fig. 8£?) and slopes southeastward to about 9 m (30 ft) 

near the eastern and southern limits of the formation on 

the uplands.

The Parsonsburg Sand overlies the Pensauken Formation, the Beaverdam Sand, the Walston Silt, the 

Omar Formation, and the Kent Island Formation (fig. 

1).

East of Salisbury, the northeast-trending belt of thick 

Parsonsburg Sand that passes through Pittsville (fig.
B8 GEOLOGIC STUDIES IN EMERGED COASTAL PLAIN OF MIDDLE ATLANTIC STATES

TABLE 1.—Section of the Parsonsburg Sand exposed in borrow pit on divide north of Parsonsburg, Md. (Pittsville 1 7, fig. 4)

[Altitude of ground surface about 25 m (83 ft)]

Unit Range in thickness 

in meters (feet)

Average depth in 

meters (feet)

Sand, pale-yellowish-brown, medium-grained, loose, 

apparently structureless, forms a low ridge (dune). 

Where present, the underlying sand of unit 2 is 

reddish brown and slightly cemented --————————

Sand, yellowish-brown above to pale-gray below, 

medium-grained; some coarse-grained and finegrained sand and granules; thin lenses of small 

pebbles; beds 1.3-15 cm (0.5-6 in.) thick, bedding 

essentially horizontal to gently inclined; abundant 

"finger" burrows in upper part; locally small-scale 

undulations and possible load casts; small-scale 

crossbedding and channeling and heavy-mineral 

laminae, especially in lower part. Thin beds of 

fine sand, silt, and clay near base of unit. Near 

center of north wall, bedded sand contains thin 

layer of peaty sediment, depth about 1.5 m (5 ft), 

underlain by about 1.25 m (4 ft) of fine sand 

containing thin clay lenses. The fine sand and clay 

are symmetrically folded; folds are about 0.6 m 

(2 ft) high, and axial planes are essentially 

vertical. In places, the clay beds are broken. 

The folds die out abruptly above and below——————

Peaty fine sand and silt, dark-gray to black (moist); 

contains abundant organic matter, fragments of wood; 

becomes brown and more clayey near base————————

0.0-2.5 (0-8) 0.0-1.2 (0-4)

3.0-3.7 (10-12) 

1.5 (5)

1.2-4.6 (4-15) 

4.6-6.1 (15-20)

8A) is close to the position of the 12-m contour on the 

base of the formation (fig. SB). South of Salisbury, the 

12-m restored contour is close to the northern limit of 

the formation. We suspect that the 12-m contour is close 

to the position of the highest stand of the Sangamon Sea 

or the northwest limit of the Omar Formation. Perhaps 

the belt where the sand is thick is related to sandy deposits near the shore of the Sangamon Sea. We will discuss the source of the Parsonsburg Sand in more detail 

later.

On the upland north of Parsonsburg, at altitudes of 

about 18-25 m (60-80 ft), the Parsonsburg Sand was 

exposed in the borrow pit at Pittsville 17 and was penetrated in six adjacent drill holes (fig. 9). Here the formation includes about 5 to 8 m (17-26 ft) of sand and 

peaty sediment underlain by clay-silt beds of the Walston 

Silt.

The section is drawn on the assumption that the sediment rich in organic matter was deposited in several 

small ponds, which in the line of section were about 0.5- 

2.0 km (0.3-1.2 mi) in diameter. For example, the peaty 

sediment at the base of test hole Cg40 would, on this 

assumption, be older than that in adjacent holes. Other 

relationships are possible. Perhaps there was a larger

pond with an uneven bottom; sand mixed with organic 

matter might have been deposited on part of the pond 

bottom, while only sand was being deposited elsewhere. 

On the other hand, if we are dealing here with several 

small ponds between sand dunes, the ponds might have 

been contemporaneous but not necessarily at the same 

elevation. If sand were being blown by the wind during 

the life of this pond or ponds, the relationship of the units 

shown in the cross section could be explained in part as 

the result of the advance of a sand dune into a pond. In 

holes P24 and P25, for example, organic matter mixed 

with sand was deposited in a pond. At a later time, a 

sand dune advanced into the pond from the north. As a 

result, only sand was deposited in the north half of the 

pond (P24), while sand mixed with organic matter continued to accumulate in the south half of the pond (P25). 

Stratigraphic relations near the eastern side of the 

area of Parsonsburg Sand on the uplands east and south 

of Salisbury suggest that the sand moved eastward across 

the western limit of the clay-silt facies of the Omar Formation. As shown in figure 10A, about 3-6 m (10-20 ft) 

of Parsonsburg Sand overlies the Beaverdam Sand, Omar 

Formation, and Kent Island Formation. In auger hole 

SH25, the dated horizon of peaty sediment contains pine,
PARSONSBURG SAND IN CENTRAL DELMARVA PENINSULA

10 20 30 CENTIMETERS

5 10 15 20 CENTIMETERS

I__I

T

5 INCHES

\ I

5 10 INCHES

FIGURE 6.—Bedding in Parsonsburg Sand exposed in borrow pit 

north of Parsonsburg, Md. (Pittsville, 17, fig. 4), sketched from 

photographs. A, Bedding horizontal or gently inclined. Disconformity at top of section. B, Inclined bedding in lower part of unit 

2, figure 5.

3 FEET

FIGURE 7.—Crossbedding and deformation in Parsonsburg Sand exposed in borrow pit north of Parsonsburg, Md. (Pittsville, 17, fig. 

4), sketched from photographs. A, Small-scale crossbedding in horizontally bedded sand. Crossbeds contain considerable amounts of 

dark minerals. Origin of vertical structures is unknown. B, Deformed beds of fine sand containing clay laminae between beds rich 

in organic matter. The basal peaty sand and silt (unit 3, fig. 5) is 

beneath the section shown in the figure.

birch, and spruce pollen. The peaty sediment in the two 

other holes has not been analyzed. The data suggest that 

the sand spread southward across a pond or swamp.

On the east edge of the sand sheet northeast of Powellville, Md. (fig. 105), the Parsonsburg Sand contains 

four horizons of peaty sediment and rests on the Omar 

Formation (Ninepin 24). The organic sediments contain 

cool-climate indicators (pine, spruce, birch, and alder) 

and range in radiocarbon age from 20,490 ± 500 years 

B.P. near the base to 16,280 ± 350 years B.P. in a layer 

about 2 m (7 ft) below the ground surface. Deposition of 

Parsonsburg Sand began here (Ninepin 24) nearly 10,000 

years after the start of deposition on the upland north 

of Parsonsburg (Pittsville 17). Sand was transported

eastward and deposited on the clay-silt of Sangamon age. 

Sand movement took place over a period of more than 

4,000 years. Sand deposition alternated or was contemporaneous with the deposition of organic material in 

small ponds or swamps. The sand now forms a low bluff 

on the west side of the Pocomoke River (east of Ninepin 

24). We postulate that sand of Omar age west of Powellville was picked up by the wind, carried eastward, and 

deposited as a blanket about 4 m (14 ft) thick. The surface of this blanket of sand was molded into parabolic 

dunes. The low bluff along the river is the stabilized front 

of the sand sheet.

The Pocomoke River came into being when sea level 

fell in late Omar (early Sangamon) time; it occupied its
BIO GEOLOGIC STUDIES IN EMERGED COASTAL PLAIN OF MIDDLE ATLANTIC STATES

TABLE 2.—Presence or absence of arboreal and nonarboreal 

pollen in 24 samples of the Parsonsburg Sand

Number of

samples in which

present

Percent of

total number

of samples

Arboreal pollen

Spruce —— ——— -

Pine ———— — —

Hemlock ———— --

Cedar group1 . —

Willow--- ——— —

Hickory- — —— -

Birch ———————

Alder ———————

Oak- ———————

Black gum— -----

Ericaceae ————

Rosaceae ——— —

Others ——————

23

24

4

11

11

2

22

21

11

4

14

11

15

96

100

17

46

46

8

92

88

46

17

58

46

63

Nonarboreal pollen

Pondweed-- — — 8

Cattail ————— 7

Grass ——————— 23

Sedae----------- +J ^» v-* y ^, 24jl. i

Polygonaceae —— 8 

Compositae —— -- 20

Others —————— 23

33O O

29

96

100

33

po

96

Cypress present in one sample.

present channel during the deposition of the Parsonsburg Sand. The sand on the Omar Formation southeast 

of the river (fig. 4) may have come from the flood plain. 

Deposition may or may not have been contemporaneous 

with that of the Parsonsburg Sand northwest of the 

river; certainly the sand southeast of the river antedates 

the formation of the swamp that now borders the river's 

channel.

AGE

The Parsonsburg Sand in the area of this report is 

largely of late Wisconsin age; its upper part is perhaps

early Holocene. The evidence is both stratigraphic and 

radiometric. In the eastern and southern part of the central Delmarva uplands, largely in Maryland (fig. 1), the 

Parsonsburg Sand overlies the Omar Formation of Sangamon age. Peaty sediments in the formation have been 

dated by the radiocarbon method and range in age from 

about 30,000 to about 13,000 years B.P. (table 3). An environment favorable for Parsonsburg deposition may 

have lasted several thousand years longer because the 

cool climate of the late Wisconsin may have persisted in 

the early Holocene. Spruce is present in the pollen record until about 9,000 years B.P. (Sirkin and others, 

1977).

In areas where peaty sediment is absent, sand mapped 

as Parsonsburg may be sandy beds of the Omar Formation of Sangamon age or of the Walston Silt of Pliocene 

age. Such an area is the belt of Parsonsburg Sand northwest of Salisbury (fig. 1). The belt marks the approximate position of a shoreline of the ancestral Chesapeake 

Bay during Sangamon time. In the absence of radiocarbon ages or of pollen data, some of the sand in this belt 

may be nearshore deposits of Sangamon age perhaps overlain or mixed with eolian sand of Wisconsin age derived 

from the adjacent Sangamon deposits.

SURFACE EXPRESSION

The surface of the Parsonsburg Sand consists of long, 

narrow, sinuous ridges separating broad poorly drained 

swales. Many of the ridges are stabilized U-shaped dunes 

built by northwest winds. The sand ridges are low with 

gentle side slopes, and their spacing is irregular. The 

dunes probably formed in late Wisconsin time or in the 

early Holocene. They are best developed on the east side 

of the Nanticoke, Wicomico, and Pocomoke Rivers, but 

U-shaped dunes also are found in some areas on the uplands between the rivers. The dunes are described in 

more detail by Denny and Owens (1978).

ORIGIN

IN THE VALLEYS

The Parsonsburg Sand caps terraces along the east 

side of the Nanticoke, Wicomico, and Pocomoke Rivers. 

Here the sand forms parabolic dunes whose axes trend 

northwest, indicating that the sand came from riverbank 

or flood plain and was picked up, transported, and deposited by winds from the northwest. At present the rivers 

are bordered by tidal marsh or fresh-water swamp. Only 

one or two of the auger holes on the terraces along the 

three rivers found peaty sediment beneath sand. Along 

the Nanticoke River, about 19 km (12 mi) above its 

mouth (loc. 4, fig. 1), peaty sediment beneath 5.2 m (17 

ft) of sand has a radiocarbon age of about 28,000 years 

B.P.; its pollen spectra is dominated by pine, spruce,
PARSONSBURG SAND IN CENTRAL DELMARVA PENINSULA 

30' 75°22'30" 75°37'30" 30'

Bll

38°22'30"

38°15' —

75°22'30"

— 38°22'30"

38°15'

Snow HU

10 KLOMETERS

5 MILES 

EXPLANATION

.'.[•'.' Parsonsburg Sand

—— Contact

S—— Thickness of formation, 

in meters

0 SMILES 

EXPLANATION

I""".* .'*""]

[•'.•'.;.';':'] Ffersonsburg Sand

Contact

B

— -9-— Restored contours on base 

of formation, in meters

FIGURE 8.—Maps showing Parsonsburg Sand on uplands east and south of Salisbury, Md. A, Contour map showing thickness of formation.

B, Map showing restored contours on base of formation.

birch, and alder. The data suggest that the Parsonsburg 

Sand in this vicinity was deposited at the same time as 

that on the uplands east and south of Salisbury, Md. (fig. 

4). However, most of the Parsonsburg Sand in the Nanticoke and other valleys might be as young as early Holocene.

The Parsonsburg Sand has not been found in the valley 

of the Choptank River (fig. 1) nor in the upper reaches of 

the Pocomoke Valley. Laminated silt and micaceous sand 

of the Choptank and Calvert Formations (Owens and 

Denny, 1978) are exposed in the banks of the Choptank 

River, and the upper Pocomoke River is bordered by 

dark-colored clay-silt of the Omar Formation. Perhaps 

these beds were not an adequate sand source because 

they are too fine grained. Southeast of the Choptank Valley, the rivers are bordered either by sandy beds of the 

Beaverdam Sand or Pensauken Formation or by one or 

more terraces underlain by sandy fluviatile or estuarine 

deposits (Kent Island Formation, fig. 1).

Along the Pocomoke River, the body of Parsonsburg 

Sand on the east side of the river more or less coincides 

with the extent of the underlying Kent Island Formation 

(fig. 1). Neither formation is present upriver from the 

vicinity of Powellville (fig. 4).

ON THE UPLANDS

The Parsonsburg Sand mantles about a third of the upland areas east of the Nanticoke River (fig. 1) where the 

older rocks are the Beaverdam Sand, the Walston Silt, 

and the Omar Formation. These units contain abundant 

sand, yet none of them appear to have been the principal 

sand source for the Parsonsburg. The Parsonsburg generally contains less feldspathic material and a more stable heavy-mineral assemblage than do the adjacent formations (figs. 2 and 3). We postulate that the sands of 

the Parsonsburg came from sandy beds in the Omar Formation or Walston Silt. In order to explain the mineralogy of the Parsonsburg Sand, we further postulate that 

the Sangamon and upper Tertiary sands were reworked, 

probably on a beach or associated dune field, prior to 

deposition as Parsonsburg Sand. The reworking may 

have taken place during a Sangamon high stand of the 

sea about 12 m (40 ft) to perhaps as much as 17 m (55 ft) 

above present sea level.

Chlorite is abundant in the clay-silt fraction of the Parsonsburg Sand and the Omar Formation and in the Holocene fill of Chesapeake Bay (Owens and others, 1974), 

but it is absent in beds of late Tertiary age (Walston, 

Beaverdam, and Pensauken). The distribution of chlorite
B12 GEOLOGIC STUDIES IN EMERGED COASTAL PLAIN OF MIDDLE ATLANTIC STATES

ALTITUDE, 

IN METERS

_ , Parsonsburg

0 .5 1 KILOMETER

0 % 1 MILE

EXPLANATION

Parsonsburg Sand

Sand SedBnent contacting 

organic material

Walston Sit 

Beaverdam Sand

Auger hole or borrow pit Number refers to locality 

in quadrangle

Dril hole. Data taken from Ramussen and 

Slaughter, 1955

< 25'690±6MRadtocarbon age of sediment sample containing 

organic matter, in years before present

w 

b 

P8

Bg11

FIGURE 9.—Cross section of the Parsonsburg Sand overlying the 

Walston Silt on the upland north of Parsonsburg, Md. Section 

is on the Wicomico River-Pocomoke River divide from Melson 

south to Parsonsburg. Section includes the large borrow pit at 

Pittsville 17. For location of auger holes and borrow pit, see 

figure 4. Vertical exaggeration x 200.

in the rocks of the peninsula appears to support our belief 

that the Parsonsburg was derived from the Omar. However, the chlorite in the Parsonsburg could have come 

from bay fill of Wisconsin age. The soils over much of the 

area have loamy surface horizons (R. D. Hall, oral commun., 1975), suggesting a thin mantle of eolian silt. If we 

postulate strong northwest winds during late Wisconsin 

(Parsonsburg) time when the level of the bay was 50 m 

(165 ft) or more below present sea level, fine-grained 

chlorite-rich sediment may have been picked up by the 

wind from the exposed bay floor, blown across the Delmarva Peninsula, and deposited as a thin loess cover 

over the entire area.

The distribution of the Parsonsburg Sand on the central Delmarva uplands (fig. 1) does not conform with the 

distribution of any of the older sandy deposits that might 

be the source of the sand. As previously mentioned, the 

mineralogy of the Parsonsburg Sand suggests that the 

sand was not derived directly from an older formation. 

The explanation for the distribution of the Parsonsburg 

Sand on the uplands that seems reasonable ties the distribution of the sand to possible high stands of the Sangamon Sea.

On the uplands of the central Delmarva Peninsula (fig. 

1), a belt of Parsonsburg Sand roughly 2-8 km (1.2-5

ALTITUDE, 

IN METERS

15-

10--

W

SH8

BEAVEROAM SAND

1 KILOMETER

1 MILE

NW

ALTITUDE, 

IN METERS SE

10- N17 PARSONSBURG 

ID

PARSONSBURG SAND 

2j,20,490±500

^\ OMAR FORMATION 

BEAVERDAM SANDXX

OMAR 

FORMATION

0 .5 1 KILOMETER

Vi 1 MILE

B

EXPLANATION

Parsonsburg Sand

Sand

SH25 

Auger hole number

SH,Snow Hit quadrangle 

N, Ntnepln quadrangle

Sediment containing 

organic material

X20,490±500

Age of sediment sample 

containing organic matter. 

Dated by radiocarbon 

methods In years before 

present

FIGURE 10.—Cross sections showing Parsonsburg Sand overlying 

Beaverdam Sand, Omar Formation, and Kent Island Formation. A, North-south section north of Snow Hill, Md. B, Northwest-southeast section northeast of Powellville, Md. For location of auger holes, see figure 4. Vertical exaggeration x 200.

mi) wide extends from the Nanticoke Valley southeast 

through the southern part of Salisbury to a point about 

12 km (8 mi) north of Pocomoke City. The southern half 

of the belt south of the Wicomico River is also shown in
PARSONSBURG SAND IN CENTRAL DELMARVA PENINSULA B13

TABLE 3.—Radiocarbon age determinations on samples from the Parsonsburg Sand and adjacent formations

[Locations in figs. 1 and 4]

Laboratory no. Quadrangle 

and field no.

Sample site 

and location

Description 

of sample

Age 

(years B.P.)

W-2842 Snow Hill 25- Auger hole on low ridge, 

altitude about 12 m 

(40 ft), Forest Lane 

Road about 2 km (1.2- 

mi) north of State Route 

354.

Peaty silt, 1m 

(3.3 ft) thick, 

beneath 2 m 

(6.6 ft) of sand.

W-2843 Dividing 

Creek 17

Auger hole on plain, alti- Peaty sand and

W-2995 Kingston 12-

W-3002 Ninepin 24-

tude about 9 m (30 ft), 

north-south road about 

2 km (1.2 mi) south of 

West P.O.

Davis-type piston core in 

cypress swamp at sea 

level east of Pocomoke 

River, about 2.4 km 

(1.5 mi) east-southeast 

of Rehobeth and about 

0.4 km (0.25 mi) east 

of Hickory Run Road.

Auger hole on low ridge, 

altitude about 14 m 

(46 ft), at Mt. 

Pleasant, about 4.7 km 

(2.9 mi) northeast of 

Powellville.

silt, 0.6 m 

(2 ft) thick, 

beneath 1.5 

m (5 ft) of 

sand.

Sandy, muddy peat 

0.25 m (0.8 ft) 

thick beneath 9 

m (30 ft) of 

peat.

Peat and silty 

sand, 0.3 m (1 

ft) thick, beneath 2 m (6.6 

ft) of sand.

W-3003 Pittsville 8- Auger hole on low ridge, Peat 2.8 m (9 ft)

altitude about 24 m 

(80 ft) on Parsonsburg 

divide about 2 km 

(1.2 mi) south of Melson.

W-3016 Ninepin 24- Same as W-3002-

thick, beneath 

about 3.6 m 

(12 ft) of 

sand. Sample 

from depth of 

about 4.6 m 

(15 ft).

Peat and silty 

sand, 0.6 m 

(2 ft) thick, 

beneath about 

5.9 m (19 ft) 

of interbedded 

sand, thin clay 

lenses, and 

peat beds 

0.3-0.6 m 

(1-2 ft) thick.

17,850+350

22,340+600

8,940+250

16,280+350

25,690+600

20,490+500
B14 GEOLOGIC STUDIES IN EMERGED COASTAL PLAIN OF MIDDLE ATLANTIC STATES

TABLE 3.—Radiocarbon age determinations on samples from the Parsonsburg Sand and adjacent formations—Continued

[Locations in figs. 1 and 4]

Laboratory no. Quadrangle 

and field no.

Sample site 

and location

Description 

of sample

Age 

(years B.P.)

W-3019

W-3096

Pittsville 8——— Same as W-3003-

Pittsville 17—— Borrow pit, altitude 

about 20 m (66 ft), 

on Parsonsburg 

divide about 2.8 km 

(1.7 mi) north of 

Parsonsburg.

W-3097

W-3098

W-3105

•do- •do-

•do- •doFederalsburg 4—

W-3106 Burrsville 2-

W-3271 Mardel a 

Springs 13.

Gully on west bank of 

Marshyhope Creek, 

about 1.5 km (0.9 mi) 

south of Federalsburg, 

altitude about 8 m 

(26 ft).

West bank of Marshyhope 

Creek at Gut Bridge, 

altitude about 15.5 m 

(51 ft), about 8 km 

(5 mi) east-northeast 

of Burrsville.

Auger hole on low ridge 

altitude about 7 m 

(23 ft), on plain east 

of Nanticoke River, 

about 1.1 km (0.7 mi) 

north-northwest of 

Camphels Wharf.

Same as W-3003, 

Sample from 

depth of about 

6.5 m (21 ft).

Sandy peat about 

1.5 m (5 ft) 

thick, beneath 

about 3.0-4.6 

m (10-15 ft) 

of sand

containing thin 

lenses of clay 

and peaty sand. 

Sample from depth 

of about 3.6 m 

(12 ft).

Same as W-3096. 

Sample from 

depth of about 

4 m (13 ft).

Same as W-3096. 

Sample from 

depth of about 

4.3 m (14 ft).

Wood from humusstained sand, 

1.5 m (5.0 ft) 

thick, beneath 

about 1.5 m 

(5.0 ft) of 

dune sand. Wood 

from depth of 

about 2.8 m 

(9 ft).

Peat about 1.2 

m (4 ft) thick 

overlies clay. 

Sample from depth 

of about 0.9 m 

(3 ft).

Peaty sand, 1 m 

(3.3 ft) thick, 

beneath 5.2 m 

(17 ft) of sand.

28,330+600

21,570+500

23,300+500

30,560+750

13,420+300

9,020+300

27,900+700
PARSONSBURG SAND IN CENTRAL DELMARVA PENINSULA B15

figure 4. Altitudes in this belt range commonly from 

about 10 to 14 m (35-45 ft). The belt appears to mark a 

shoreline of Omar (Sangamon) time. We believe that the 

sand in this belt consists largely of shore and nearshore 

deposits of Sangamon age that were partially reworked 

in Parsonsburg time. Scattered data on the microflora in 

a few auger samples from the belt south of the Wicomico 

River support our thesis that the belt is composed of materials of both Sangamon and Wisconsin age.

The distribution of the Parsonsburg Sand on the uplands east of Salisbury may also be related to a Sangamon high stand of the sea. East of Salisbury, the outcrop 

belt of the Parsonsburg Sand is wider than it is in the 

area to the west (10-15 km (6-10 mi)), but the range in 

altitude is about the same. The exception is the divide 

area near Parsonsburg (fig. 8), where the altitude is as 

much as 24 m (80 ft).

On the drainage divide north and south of Parsonsburg 

in an area roughly 8 by 10 km (5 by 6 mi), altitudes 

range from about 18 to 24 m (60^80 ft). The Parsonsburg Sand is heaped into parabolic dunes formed by 

northwest winds, suggesting an eolian origin for the formation. However, the internal structure of the unit as 

exposed in the large borrow pit on the divide (Pittsville 

17, fig. 4) suggests that the dunes are underlain by 

water-laid sand deposited in small ponds between older 

dunes. The area on the divide is only about 80 sq km 

(30 sq mi). The base of the Parsonsburg Sand is at about 

18-20 m (60-65 ft) above sea level in the subsurface 

beneath the divide (fig. 8B) that in Sangamon time was 

a low-lying island near the southern end of the ancestral 

Delmarva Peninsula. We postulate that in Sangamon 

(Omar) time, this island was capped by sand dunes 9- 

12 m (30-40 ft) high, their tops being about 30 m (100 

ft) above present sea level. In Parsonsburg time, sand 

of Sangamon age was moved by the wind. Small ponds 

and swamps between dunes were filled first by peaty 

sediment and later by sand. We suggest that sand dunes 

of Sangamon age were reworked more or less in place by 

water and by wind to form the Parsonsburg Sand that 

now mantles the divide.

The structural and topographic relations of the Parsonsburg Sand on the divide support our belief that the 

formation was in part laid down in small interdune ponds. 

At Melson (figs. 4, 9), the upland stands about 20 m (65 

ft) above sea level, and to the north and northwest, it 

ranges from about 15 to 18 m (50-60 ft). If the sand 

exposed in the borrow pit (Pittsville 17, figs. 4, 9) was 

laid down in a small pond, then there must have been a 

barrier of some sort between the pit and Melson. Perhaps the sand found in the auger hole at Pittsville 8 or 

21 is part of a dune ridge that dammed the pond at Pittsville 17. Small ponds or bogs at Pittsville 8 and 17, perhaps separated by sand ridges, came into existence about

28,000^30,000 years B.P. The northern pond (Pittsville 

8) was filled, at an average rate of about 0.072 cm/year, 

with sediment containing abundant organic matter, and 

about 25,000 years B.P., the sediment was buried by 

sand. The pond at the site of the borrow pit to the south 

(Pittsville 17) filled with sediment containing much organic matter at a slower rate (0.004-0.017 cm/year), and 

about 21,500 years B.P., sand containing only a little organic matter was laid down. Deposition continued until 

about 4.5 m of sand had accumulated. Perhaps the sand 

came from a dune that was advancing into the pond.

On the upland north of Whitesville (fig. 4) are a few 

isolated parabolic dunes whose sand probably is derived 

from the adjacent Beaverdam Sand. In the auger hole at 

Pittsville 13, for example, the dune sand rests directly 

on the Tertiary rocks without any intervening layer containing organic matter. The isolated dunes appear to 

have been formed by northwest winds, and their sand 

presumably came from sand reworked or weathered 

from the underlying Beaverdam Sand.

The age of the Parsonsburg Sand, on the basis of the 

available carbon-14 dates (table 3), ranges from about 

30,000 years to about 16,000 years B.P., perhaps to as 

late as about 13,000 years B.P. The dated samples are 

largely from the base or the lower part of the formation, 

and most of them are more than 20,000 years old. The 

dated samples may indicate that most of the formation is 

older than about 20,000 years B.P. On the contrary, deposition of sediment containing abundant organic matter 

may have been widespread during early Parsonsburg 

time and may have been much more limited in late Parsonsburg time when sand was the principal material to 

be deposited. Perhaps deposition of the upper part of the 

Parsonsburg Sand is related to the cold climate of the 

last glacial maximum about 18,000 years B.P.

We picture the central Delmarva upland during Parsonsburg time as a pine-birch barrens where isolated 

sand dunes were separated by small ponds or bogs. The 

present landscape on the Parsonsburg Sand consists of 

low sandy ridges separated by broad poorly drained 

swales (Denny and Owens, 1978) and perhaps resembles 

the landscape as it was during Parsonsburg time. The 

dune sand came from bare sandy areas on the shores of 

the ponds or in small areas of parkland. Perhaps eolian 

activity was dominant when the water table was low, and 

lacustrine deposition was dominant when the ponds were 

full. Ponds were present between sand hills because evapotranspiration was low as a result of cool temperatures 

and sparse vegetation. Dunes advanced into ponds, where 

the sand was redistributed by circulating currents in the 

water. Runoff in the spring when the ground was still 

frozen may have promoted transport and deposition of 

sand in the interdune depressions.
B16 GEOLOGIC STUDIES IN EMERGED COASTAL PLAIN OF MIDDLE ATLANTIC STATES

The dunes are irregularly spaced and are commonly 

associated with poorly drained swales, as if the sand 

came from the swale—perhaps the shore of a small pond— 

and was heaped up on the edge of the swale. This association suggests that the dunes did not move any great 

distance across the uplands. Only on the east side of the 

uplands along the west side of the Pocomoke River 

where Parsonsburg Sand overlies clay-silt of the Omar 

Formation is there clear evidence that sand was carried 

southeast for several kilometers across the underlying 

clay-silt. In most of the central Delmarva Peninsula, the 

Parsonsburg Sand appears to be close to its source, regardless of whether it was transported by water or by 

wind.

Freezing or thawing of the ground does not appear to 

have been a factor during deposition of the Parsonsburg 

Sand. The deformed beds seen in the borrow pit near 

Parsonsburg (Pittsville 17) and elsewhere are best explained as the result of slumping caused by either loading 

of sand on saturated fine sand or clay-silt, or by changes 

in water level, or by both processes.

REFERENCES CITED

Denny, C. S., and Owens, J. P., 1978, Sand dunes on the central 

Delmarva Peninsula, Maryland and Delaware: U.S. Geol. Survey Prof. Paper 1067-C. (In press.)

Hansen, H. J., Ill, 1966, Pleistocene stratigraphy of the Salisbury 

area, Maryland, and its relationship to the lower Eastern 

Shore—A subsurface approach: Maryland Geol. Survey Rept. 

Inv. 2, 56 p.

Hess, Melodie, 1977, Drill-hole logs and location map of surface and 

shallow subsurface materials, central and southern Delmarva

Peninsula, Maryland, Delaware, and Virginia: U.S. Geol. Survey Misc. Field Studies Map MF-899, 2 sheets, scale 1:250,000.

Jackson, M. L., 1965, Clay transformations in soil genesis during the 

Quaternary: Soil Sci., v. 99, no. 1, p. 15-22.

Jordan, R. R., 1964, Columbia (Pleistocene) sediments of Delaware: 

Delaware Geol. Survey Bull. 12, 69 p.

___1967, Delaware guidebook—Atlantic Coastal Plain Geological 

Association, 8th Annual Field Conference: Newark, Del., Univ. 

Delaware and Delaware Geol. Survey, [20] p., appendices and 

road log.

___1974, Pleistocene deposits of Delaware, in Oaks, R. Q., Jr., and 

DuBar, J. R., eds.. Post-Miocene stratigraphy, central and 

southern Atlantic Coastal Plain: Logan, Utah, Utah State Univ. 

Press, p. 30-52.

Jordan, R. R., and Talley, J. H., 1976, Guidebook—Columbia deposits 

of Delaware: Delaware Geol. Survey, open-file rept. 8, 49 p.

Owens, J. P., and Denny, C. S., 1978, Upper Cenozoic deposits of the 

lower Delmarva Peninsula, Maryland and Delaware: U.S. Geol. 

Survey Prof. Paper 1067-A. (In press.)

Owens, J. P., Stefansson, Karl, and Sirkin, L. A., 1974, Chemical, 

mineralogic, and palynologic character of the upper Wisconsinan-lower Holocene fill in parts of Hudson, Delaware, and Chesapeake estuaries: Jour. Sed. Petrology, v. 44, no. 2, p. 390- 

408.

Rasmussen, W. C., 1953, Periglacial frost-thaw basins in New Jersey, 

a discussion: Jour. Geology, v. 61, no. 5, p. 473^74.

_____1958, Geology and hydrology of the "bays" and basins of Delaware: Bryn Mawr, Pa., Bryn Mawr College, Ph. D. thesis, 199

PRasmussen, W. C., and Andreasen, G. E., 1959, Hydrologic budget of

the Beaverdam Creek basin, Maryland: U.S. Geol. Survey

Water-Supply Paper 1472, 106 p. 

Rasmussen, W. C., and Slaughter, T. H., 1955, The ground-water

resources, in The water resources of Somerset, Wicomico, and

Worcester Counties: Maryland Dept. Geology, Mines and Water

Resources Bull. 16, p. 1-469. 

Sirkin, L. A., Denny, C. S., and Rubin, Meyer, 1977, Late Pleistocene

environment of the central Delmarva Peninsula: Geol. Soc.

America Bull., v. 88, no. 1, p. 139-142.

fr U.S. Government Printing Office: 1979—281-359/60