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Geology, Geochemistry, and Tectonostratigraphic 

Relations of the Crystalline Basement Beneath the 

Coastal Plain of New Jersey and Contiguous Areas

By Richard A. Volkert, Avery Ala Drake, Jr., and Peter J. Sugarman

GEOLOGIC STUDIES IN NEW JERSEY AND EASTERN PENNSYLVANIA

U.S. GEOLOGICAL SURVEY PROFESSIONAL PAPER 1565-B

Prepared in cooperation with the 

New Jersey Geological Survey

Pre-Mesozoic metasedimentary and 

metaigneous rocks beneath the New Jersey 

Coastal Plain resemble those of 

tectonostratigraphic terranes in both the 

central and northern Appalachians

UNITED STATES GOVERNMENT PRINTING OFFICE, WASHINGTON: 1996
U.S. DEPARTMENT OF THE INTERIOR 

BRUCE BABBITT, Secretary

U.S. GEOLOGICAL SURVEY 

GORDON P. EATON, Director

For sale by U.S. Geological Survey, Information Services 

Box 25286, Federal Center, Denver, CO 80225

Any use of trade, product, or firm names in this publication is for descriptive purposes only and 

does not imply endorsement by the U.S. Government.

Published in the Eastern Region, Reston, Va. 

Manuscript approved for publication January 20, 1995

Library of Congress Cataloging in Publication Data

Volkert, Richard A.

Geology, geochemistry, and tectonostratigraphic relations of the crystalline basement

beneath the coastal plain of New Jersey and contiguous areas / by Richard A. Volkert,

Avery Ala Drake, Jr., and Peter J. Sugarman ; prepared in cooperation with the New

Jersey Geological Survey, 

p. cm. — (Geologic studies in New Jersey and eastern Pennsylvania ; B) (U.S.

Geological Survey professional paper; 1565) 

Includes bibliographical references (p. - ). 

Supt.ofDocs.no.: 119.16:1565-8 

1. Rocks, Crystalline—New Jersey—Atlantic Coast. 2. Petrology—New Jersey—Atlantic

Coast. 3. Atlantic Coast (N.J.) I. Drake, Avery Ala, 1927- . II. Sugarman, Peter

J. III. New Jersey Geological Survey. IV. Title. V. Series. VI. Series: U.S.

Geological Survey professional paper; 1565. 

QE141.G46 19% vol. B 

[QE445.N5] 

557.49 s—dc20

[552.09759] 95-14469

CIP
CONTENTS

Abstract......................................................................................................................... Bl

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

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

Regional Geology......................................................................................................... 2

New Jersey Coastal Plain Sediments.................................................................... 2

Mesozoic Rocks of the Newark Basin.................................................................. 3

Exposed Middle Proterozoic and Paleozoic Crystalline Rocks............................ 3

Geophysical Data.......................................................................................................... 10

Gravity Data.......................................................................................................... 10

Aeromagnetic Data............................................................................................... 10

Description of Well Samples......................................................................................... 12

Introduction........................................................................................................... 12

Cape May County................................................................................................. 12

Cumberland County.............................................................................................. 12

Atlantic County..................................................................................................... 14

Ocean County........................................................................................................ 14

Monmouth County................................................................................................ 15

Middlesex County................................................................................................. 15

Mercer County...................................................................................................... 15

Burlington County................................................................................................ 15

Camden County.................................................................................................... 16

Gloucester County................................................................................................ 16

Salem County........................................................................................................ 19

Hudson County..................................................................................................... 20

Delaware............................................................................................................... 20

Metamorphic Grade.............................................................................................. 20

Geochemistry................................................................................................................ 21

Metapelite and Metagraywacke............................................................................ 21

Metabasalt............................................................................................................. 22

Meta-andesite........................................................................................................ 25

Metagabbro........................................................................................................... 28

Metagraywacke at Island Beach State Park.......................................................... 28

Discussion..................................................................................................................... 29

Conclusions................................................................................................................... 35

References Cited........................................................................................................... 36

Appendix: Selected Coastal Plain Wells and Seismic Stations in New Jersey and

Contiguous Areas that Penetrate Basement Rock............................................. 41

FIGURES

1-3. Maps showing—

1. Physiographic provinces of New Jersey....................................................................................................... B2

2. Tectonic setting of the New Jersey Coastal Plain......................................................................................... 3

3. Geology of the exposed pre-Mesozoic crystalline rocks in the Trenton, N.J., area..................................... 4

4. Chart showing a generalized sequence of rock units of some central and northern Appalachian crystalline

rocks ................................................................................ 5

III
IV CONTENTS

5, 6. Maps showing—

5. Geology of the Hoboken, N.J., area.............................................................................................................. 7

6. Tectonostratigraphic terranes of the central Appalachians........................................................................... 8

7. Chart showing tectonostratigraphic sequence of generalized relation of terranes of the central and northern

Appalachians................................................................................................................................................. 9

8. Bouguer gravity anomaly map of New Jersey and contiguous areas.................................................................... 11

9. Aeromagnetic map of New Jersey and contiguous areas...................................................................................... 12

10. Location map of wells penetrating basement rock in New Jersey and contiguous areas...................................... 13

11. Photograph showing type 2 fold interference patterns in amphibolite.................................................................. 19

12. Map showing metamorphic isograds in the pre-Mesozoic crystalline basement of New Jersey.......................... 21

13, 14. Plots of pelitic and psammitic schist from beneath the New Jersey Coastal Plain on diagrams of—

13. Si/(Si+Al) versus (Na+Ca)/(Na+Ca+K)....................................................................................................... 22

14. K2O/Na2O versus SiO2 ................................................................................................................................. 22

15. AFM plot of metabasalt and meta-andesite from beneath the New Jersey Coastal Plain..................................... 23

16. Chondrite-normalized rare earth element plot of New Jersey metabasalt and meta-andesite............................... 23

17, 18. Plot of mafic rocks from beneath the New Jersey Coastal Plain on diagrams of—

17. Zr/Y versus Zr............................................................................................................................................... 23

18. Nb-Zr-Y......................................._ 24

19. MORB-normalized incompatible-element diagram of New Jersey metabasalt and meta-andesite...................... 24

20. Plot of TiO2 versus Zr/P2Os showing mafic rocks from the New Jersey subsurface compared with other

Appalachian mafic rocks....................................................................................................................................... 25

21. MgO variation diagrams of major and selected trace elements for mafic rocks from beneath the New Jersey

Coastal Plain.......................................................................................................................................................... 26

22-24. Plots showing New Jersey metabasalt and meta-andesite on diagrams of—

22. Th/Yb versus Ta/Yb........................................_^ 27

23. Hf versus Sm................................................................................................................................................. 27

24. La/Sm versus La/Yb..................................................................................................................................... 28

25. Map showing speculative assignment of terranes beneath the New Jersey Coastal Plain.................................... 31

TABLES

1. Modal analyses of selected basement rocks.......................................................................................................... B14

2. Chemical analyses of selected basement rocks..................................................................................................... 17

METRIC CONVERSION FACTORS

Multiply By To obtain

inch (in) 25.4 millimeter

foot (ft) 0.3048 meter

mile (mi) 1.609 kilometer
Geology, Geochemistry, and Tectonostratigraphic Relations of the

Crystalline Basement Beneath the Coastal Plain of

New Jersey and Contiguous Areas

By Richard A. Volkert, 1 Avery Ala Drake, Jr.,2 and Peter J. Sugarman1

ABSTRACT

Cretaceous and Cenozoic sediments of the New Jersey 

Coastal Plain are underlain by basement rocks that may 

range in age from Middle Proterozoic to Mesozoic. Buried 

pre-Mesozoic crystalline rocks in New Jersey are important 

because they link rocks of the central and northern Appalachians. The peak metamorphic grade recorded in aluminous 

rocks from beneath the Coastal Plain is in the amphibolite 

facies.

The inner Coastal Plain is underlain dominantly by 

pelitic and psammitic schist and minor amounts of mafic 

rock that are correlative with the Potomac terrane in Maryland, Delaware, Pennsylvania, and Virginia. Gravity and 

magnetic highs within this part of the Coastal Plain probably result from mafic rock in a rootless pluton or a thrust 

slice. The alignment of these inferred mafic rocks along the 

same structural trend suggests that they may be related. 

These bodies may be equivalent to rocks in the Wilmington 

terrane in Delaware or the Bel Air-Rising Sun terrane in 

Maryland. Wells drilled in the northern and central outer 

Coastal Plain returned graphitic, two-mica schist and marble along a trend that is coextensive with the BromptonCameron terrane in southern Connecticut. The southern 

Coastal Plain may be underlain by rocks equivalent to the 

Chopawamsic terrane (James Run Formation) and to the 

south, rocks of the Roanoke Rapids terrane (Eastern slate 

belt). Although drill-hole data are sparse in this part of New 

Jersey, wells to the west in northern Delaware penetrated 

chlorite schist, biotite schist, and quartzite. Pyroxenite from 

this part of the Delaware Coastal Plain may be correlative 

with the Bel Air-Rising Sun terrane, or more likely it is a 

separate fragment of ultramafic rock correlative with the 

Roanoke Rapids terrane (Eastern slate belt). Metagabbro 

from the southernmost part of New Jersey may be coextensive with gabbro and associated greenschist-facies rocks in 

the Chesapeake block (Eastern slate belt). Gravity and

'New Jersey Geological Survey, CN-427, Trenton, NJ 08625. 

2U.S. Geological Survey, Reston, VA 22092.

magnetic data suggest the possible presence of small rift 

basins of early Mesozoic age beneath the southern Coastal 

Plain, but thus far no wells have drilled rock identified as 

Mesozoic. Most central and some northern Appalachian terranes appear to be present beneath the New Jersey Coastal 

Plain.

INTRODUCTION

Cretaceous and Cenozoic sediments of the New Jersey 

Coastal Plain are underlain by crystalline rocks of Middle 

Proterozoic to Paleozoic age and sedimentary and igneous 

rocks of Mesozoic age. These form a basement complex, 

which remains poorly understood because of limited direct 

sampling. In general, wells penetrating basement were 

drilled for water, for petroleum exploration, or as stratigraphic tests for Coastal Plain sediments, and the retrieval 

and study of basement rock were considered unimportant.

Recently, the geology of the subsurface crystalline 

rocks has come under increased study because the rocks 

were identified as possible repositories for high-level radioactive waste (Bredehoeft and Maini, 1981). Lloyd and others (1985) summarized and evaluated data pertaining to the 

ground-water hydrology of the Coastal Plain sediments and 

their relation to possible waste disposal in the subsurface 

basement. They identified a zone worthy of further study at 

a depth of 1,000 to about 4,000 ft below sea level in the 

crystalline basement of New Jersey and other States.

In separate areas of research, hypotheses concerning 

the tectonics of the Appalachian orogen (for example, Cook 

and others, 1979) benefit from expanded knowledge of the 

crystalline basement complex beneath the Atlantic Coastal 

Plain. New Jersey is important in this regard because it 

occupies a critical position linking the central and northern 

Appalachians. Additionally, the identification of onshore 

and offshore buried rift basins of early(?) Mesozoic age has 

taken on importance, both economically in the search for oil 

and gas reserves and scientifically in providing data on the 

opening of the Atlantic Ocean.

Bl
B2 GEOLOGIC STUDIES IN NEW JERSEY AND EASTERN PENNSYLVANIA

This study presents available geologic information on 

the buried basement, primarily in New Jersey. Descriptions 

of the crystalline rocks are both those of previous workers 

and new descriptions of core and cutting samples collected 

during this study. A tentative correlation of basement terranes is presented based on geologic information and gravity and magnetic data. The information presented here 

should be useful to geologists, hydrogeologists, geophysicists, and others interested in the pre-Cretaceous subsurface 

basement in this part of the northern central Appalachians.

ACKNOWLEDGMENTS

We are grateful to R.N. Benson, who made the samples 

of basement rocks from Delaware available for inspection 

and provided a list of the Delaware wells. D. Smolensky 

provided a list of the Long Island wells, and J. Sorel loaned 

the sample from the Brooklyn Union Gas Company well. 

M.E. Wagner generously shared unpublished geochemical 

analyses from Delaware and Pennsylvania with Volkert. L. 

Jacoby digitally plotted all of the well points on a preliminary version of figure 10, and L. Allar and D. Hogan typed 

the appendix. Volkert and Sugarman appreciate conversations with R.E. Sheridan on the geophysics of the Piedmont. 

This report benefited from reviews by D.L. Daniels, W.C. 

Burton, I.G. Grossman, and numerous staff members of the 

New Jersey Geological Survey.

REGIONAL GEOLOGY

NEW JERSEY COASTAL PLAIN SEDIMENTS

The New Jersey Coastal Plain (fig. 1) is underlain principally by unconsolidated and semiconsolidated siliciclastic 

sediments of Cretaceous and Cenozoic age. In general, 

these sediments constitute a northeast-striking, gently 

southeastward-dipping, seaward-thickening wedge that 

reaches a maximum thickness exceeding 6,300 ft in southeastern New Jersey. Coastal Plain sediments accumulated 

along the Atlantic continental margin and contain a mixture 

of nonmarine, marginal marine, and marine deposits. Nonmarine and marginal marine deposits are primarily of deltaic origin, whereas marine deposits originated on the shelf.

Coastal Plain sediments in New Jersey unconformably 

overlie a bedrock basement. Most of the sediments directly 

above basement belong to the Potomac Formation. The 

Potomac consists of several major lithofacies, including 

interbedded light-colored sand, drab, varicolored, silty clay 

and clayey silt, and very gravelly sand. Each lithofacies varies widely in thickness and lateral extent. Along the Fall 

Line from Trenton to Perth Amboy, the basement is overlain 

by sediments of the Raritan and Magothy Formations.

Sediments in the New Jersey Coastal Plain were 

deposited in two large basins (fig. 2): the Raritan embay75° 74"

40°

39° 0 16 32 KILOMETERS _

J____________I

Figure 1. Physiographic provinces of New Jersey.

ment to the north and the larger Salisbury embayment to the 

south (Owens and others, 1988). Both basins are landward 

extensions of the Baltimore Canyon trough. These basins 

are separated by the South Jersey high, an area of thinner 

sedimentary deposits that resulted from relative uplift and 

(or) lack of deposition (Owens and Gohn, 1985).

These sedimentary basins underwent differential 

movement through time. In general, the Salisbury embayment appears to have deepened in a northward direction 

during the Early Cretaceous, whereas the Raritan embayment was downwarped in the Late Cretaceous (Owens and 

others, 1988). The northward deepening appears to have 

continued until the late Paleogene and was reversed in the 

Neogene. Consequently, the modern basin configuration is a 

composite of several small tectonic events.
CRYSTALLINE BASEMENT BENEATH THE NEW JERSEY COASTAL PLAIN AND CONTIGUOUS AREAS B3

EXPLANATION 

Approximate inner edge of 

New Jersey Coastal Plain

Generalized outline of 

basins and highs

RARITAN 

EMBAYMENT

I i I 

0 30 KILOMETERS

Figure 2. Tectonic setting of the New Jersey Coastal Plain.

MESOZOIC ROCKS OF THE NEWARK BASIN

Rocks of the Newark Supergroup in New Jersey occur 

in a broad northeast-trending basin, which extends from the 

Delaware River to the New York State line (fig. 1). This 

basin is one of a series of unconnected rift basins of Triassic 

age extending along eastern North America from Nova Scotia to South Carolina. In New Jersey, Newark basin strata 

are in fault contact on the northwest with Middle Proterozoic rocks of the New Jersey Highlands and unconformably 

overlie klippen of Ordovician rocks. On the southeast, they 

are unconformably overlain by unconsolidated Cretaceous 

deposits of the inner Coastal Plain and Quaternary sand and 

gravel.

The Newark basin contains a maximum thickness of 

about 20,000 ft of Upper Triassic to Lower Jurassic nonmarine conglomerate, sandstone, siltstone, argillite, shale, and 

interbedded continental tholeiitic basalt (Van Houten,

1969). Fanglomerates of Triassic and Jurassic age, containing clasts of various Middle Proterozoic rocks, Paleozoic 

sandstone, dolomite, shale, and conglomerate, and Jurassic 

basalt locally occur adjacent to the Ramapo fault, which 

bounds the Newark basin on the northwest (fig. 1). Diabase 

of Jurassic age occurs in thick sills in Newark basin strata 

and in smaller dikes and other intrusive bodies. Newark 

basin sedimentary rocks are commonly thermally altered 

where intruded by diabase.

From Trenton to near Princeton, the Stockton Formation unconformably overlies the pre-Mesozoic crystalline 

rocks along the southeast side of the basin, but nowhere is 

the contact between them exposed. Much of the basal part 

of the Stockton is arkosic sandstone derived from the underlying crystalline rocks. It contains 50 to 70 percent quartz 

and 15 to 40 percent feldspar, plagioclase being more abundant than potassium feldspar (Van Houten, 1980). Bascom 

and others (1909) described an exposure of the Stockton at 

Cadwalader Park in Trenton, which consisted of arkosic 

conglomerate containing large clasts of quartz and feldspar.

Northeast of Princeton, both the Stockton Formation 

and the older crystalline rocks are overlain by the Cretaceous Raritan and Magothy Formations and by sand and 

gravel of the Bridgeton and Pensauken Formations. The 

Stockton emerges from beneath this cover north of Raritan 

Bay, where it unconformably overlies the serpentinite on 

Staten Island and the Manhattan Schist. There is no evidence to suggest that the Stockton is absent in the covered 

area.

EXPOSED MIDDLE AND LATE PROTEROZOIC 

AND PALEOZOIC CRYSTALLINE ROCKS

Poorly exposed crystalline rocks of the New Jersey 

Piedmont crop out in a thin, east-northeast-trending wedge, 

which underlies Mesozoic and Cenozoic rocks immediately 

northeast of Trenton. Crystalline basement rocks are 

exposed near Hoboken, N.J., and on Staten Island, N.Y., 

where serpentinite crops out. Bedrock outcrops in the Trenton area are sparse, and most are along the west shore of the 

Delaware River at Morrisville, Pa. Bascom and others 

(1909) showed an isolated body of crystalline rocks south of 

Princeton Junction, but field mapping by Volkert in 1988 

showed that these outcrops no longer exist.

Exposed pre-Mesozoic crystalline rocks in the Trenton, 

N.J., area (fig. 3) consist of Middle Proterozoic rocks to the 

north, which are unconformably overlain to the south by the 

Cambrian Chickies Quartzite. The Chickies is, in turn, 

bounded on the south by the southeast-dipping Huntingdon 

Valley fault (Bascom and others, 1909). This fault thrusts 

Middle Proterozoic rocks from the south onto the Chickies 

and, farther to the northeast, onto other Middle Proterozoic 

rocks. The Late Proterozoic to Lower Cambrian Wissahickon Formation has been thrust onto this sequence of
B4 GEOLOGIC STUDIES IN NEW JERSEY AND EASTERN PENNSYLVANIA

K | Cretaceous sediments, undifferentiated 

"6s I Stockton Formation 

€c | Chickies Quartzite 

€ZwJ Wissahickon Formation 

Zv | Metabasalt 

Ya | Amphibolite

Ygb | Metagabbro and gneiss of intermediate 

composition

Yg Felsic gneiss, granofels, and migmatite

——— Contact

>——*— Thrust fault 74°45;

3 MILES 

I

3 KILOMETERS

Figure 3. Geologic map of the exposed pre-Mesozoic crystalline rocks in the Trenton, N.J., area. Compiled from Widmer (1965) and 

R.A. Volkert and A.A. Drake, Jr. (unpub. data).

rocks along a southeast-dipping splay of the Huntingdon 

Valley fault, which Volkert and Drake (1993) have named 

the Morrisville thrust fault. These geologic relations are 

shown in figure 3. The Middle Proterozoic rocks consist of 

a heterogeneous sequence of biotite- and clinopyroxenebearing quartzofeldspathic gneiss, hornblende- and clinopyroxene-bearing felsic to intermediate gneiss, metagabbro, 

meta-andesite and amphibolite (Volkert and Drake, 1993). 

One small body of marble in these rocks is known from boring logs for the State Department of Education building in 

downtown Trenton (lithologic logs on file in the office of

the New Jersey Geological Survey, Trenton, N.J.). Many of 

these gneisses contain characteristic blue quartz and trace to 

moderate amounts of garnet and, according to Bascom and 

others (1909), locally are graphitic. No graphite was seen in 

any of the exposed rocks in the Trenton area.

The Chickies Quartzite, as exposed west of Trenton 

(fig. 3), is fine-grained, light-gray to light-greenish-gray, 

massive to well-bedded, locally crossbedded, tourmalinebearing sericite-quartz schist, quartzite, and quartz pebble 

conglomerate. The quartz pebbles are stretched down the
CRYSTALLINE BASEMENT BENEATH THE NEW JERSEY COASTAL PLAIN AND CONTIGUOUS AREAS B5

DELAWARE AND ADJACENT 

PENNSYLVANIA

GEOLOGIC 

AGE

Cambrian 

and (or| 

Late Proterozoic

Cambrian 

and lor) 

Late Proterozoic

Cambrian

Cambrian

UNIT

Peters Creek Schist 

and 

"Wissahickon Formation'

A A A

Thrust fault

Octoraro Phyllite

Thrust fault

Equivalent rocks 

not present

Vintage Dolomite through 

Conestoga Limestone

Chickies Formation

Not recognized

Unconformity

Middle Proterozoic 

rocks

MANHATTAN 

PRONG

GEOLOGIC 

AGE

Ordovician(?) 

and 

Cambrian

Cambrian 

and (or) 

Late Proterozoic

Ordovician

Ordovician 

and 

Cambrian

Cambrian

UNIT

Hartland Formation

A A A

Thrust fault

Manhattan Schist

Thrust fault

Walloomsac Formation

Inwood Marble

Lowerre Quartzite

Not recognized

Unconformity

Middle Proterozoic 

rocks

SOUTHERN 

NEW ENGLAND

GEOLOGIC 

AGE

Ordovician(?) 

and 

Cambrian

Cambrian 

and (or) 

Late Proterozoic

Ordovician

Ordovician 

and 

Cambrian

Cambrian

Cambrian 

and (or) 

Late Proterozoic

UNIT

Rowe Schist

Thrust fault

Allochthonous 

Hoosac Formation

Thrust fault

Walloomsac Formation

Stockbridge Marble

Cheshire Quartzite

Dalton Formation

Unconformity

Middle Proterozoic 

rocks

Figure 4. Generalized sequence of rock units from the north-central and southern northern Appalachians. Compiled from Hall (1976, in press), Berg and others (1983), Stanley and Ratcliffe (1985), 

Lyttle and Epstein (1987), and Brock (1989).

dip of the schistosity. No outcrops of Chickies occur east of 

the Delaware River.

Exposed to the south of the Chickies Quartzite is 

another section of Middle Proterozoic rocks (fig. 3) consisting of amphibolite, potassic feldspar augen gneiss, biotite 

schist and gneiss, calc-silicate gneiss, and biotite-quartzfeldspar gneiss. Many of these same lithologies also crop 

out north of the Chickies (Volkert and Drake, 1993). The 

augen gneiss and biotite gneiss association is similar to 

associations in Middle Proterozoic rocks from throughout 

the U.S. Appalachians, such as those of the Blue Ridge 

complex described by Sinha and Bartholomew (1984), the 

Baltimore Gneiss in the Maryland Piedmont (Hopson, 

1964), and numerous other occurrences described by 

Rankin and others (1989). We accordingly interpret this 

augen gneiss and associated schist and gneiss to be Middle 

Proterozoic in age and therefore older than the Wissahickon 

Formation; thus, not all of the schist and gneiss south of the 

Huntingdon Valley fault is Wissahickon.

Crystalline rocks farther to the northeast include the 

serpentinite at Hoboken, N.J., and Staten Island, and the 

Fordham Gneiss, Yonkers Gneiss, Manhattan Schist,

Inwood Marble, Walloomsac Formation, and Hartland Formation of the Manhattan prong. Stratigraphic correlations 

between these rocks and Piedmont rocks in adjacent States 

are shown in figure 4. The Middle Proterozoic Fordham 

Gneiss and Late Proterozoic Yonkers Gneiss are unconformably overlain by lower Paleozoic clastic and shelf carbonate rocks of the Lowerre Quartzite, Inwood Marble, and 

Walloomsac Formation (Hall, in press). The Walloomsac is 

equivalent to the Manhattan Schist, member A, of Hall 

(1976). The pelitic rocks and amphibolite of the Manhattan 

Schist (members B and C of Hall, 1976) were emplaced on 

the shelf sequence by the Elmsford thrust fault (Hall, in 

press). This sequence of basement, autochthonous, and parautochthonous cover is the North American Craton terrane 

of Zen and others (1989). The Ordovician(?) Hartland Formation is a sequence of metamorphosed interlayered clastic 

and volcanic rocks, which were thrust onto the Manhattan 

Schist along Cameron's Line thrust fault (Hall, in press). 

The Hartland Formation commonly contains serpentinite 

(Baskerville, 1990). These rocks constitute the western part 

of the Brompton-Cameron terrane of Zen and others (1989) 

and are interpreted to be fragments of obducted ocean crust.
B6 GEOLOGIC STUDIES IN NEW JERSEY AND EASTERN PENNSYLVANIA

Serpentinite crops out on Castle Point in Hoboken, it 

underlies much of Staten Island, and one body is known on 

Manhattan Island. The serpentinite at Hoboken is a tectonic 

melange containing disrupted blocks of serpentinite as 

much as several feet across within a matrix of scalycleaved, fine-grained serpentinite and talc schist. The Manhattan Schist is known from boring logs to occur in the Jersey City area but is not exposed there. At Jersey City, and 

elsewhere along the Hudson waterfront, serpentinite 

appears to have been thrust over the Manhattan Schist (Lyttle and Epstein, 1987; Baskerville, 1990; R.A. Volkert, 

unpub. data) on the Cameron's Line thrust fault (fig. 5). The 

Cameron's Line thrust fault must continue southward and 

then cut between the serpentinite exposed on northern 

Staten Island and the schist along the Hudson waterfront to 

the immediate north (fig. 5). From here, it apparently continues southwestward beneath the eastern edge of the Newark basin, merging with, or becoming, the Huntingdon 

Valley-Morrisville fault system northeast of Trenton (fig. 

3). Small bodies of serpentinite also occur within the Wissahickon Formation and the Peters Creek Schist in the Pennsylvania Piedmont immediately west of the New Jersey 

border. The fault separating these rocks from the autochthonous cover therefore may be a continuation of Cameron's 

Line.

In the part of Pennsylvania adjacent to New Jersey, 

basement rocks of Middle Proterozoic age crop out in 

numerous detached massifs of variable size. Rocks in the 

West Chester prong occur south of the Cream Valley-Huntingdon Valley fault system and are unconformably overlain 

by a lower Paleozoic succession of clastic and carbonate 

rocks of the Setters Formation and Cockeysville Marble. 

These are overlain by pelitic and psammitic schists containing ultramafic rocks and amphibolite layers usually referred 

to as the Wissahickon Formation. However, Drake (1986) 

suggested that the term "Wissahickon" actually refers to 

several distinct lithotectonic units. These include the allochthons containing the Piney Branch Complex, Peters Creek 

Schist, and Annandale Group in Virginia and Maryland of 

Late Proterozoic or Early Cambrian age, and the high-grade 

Wissahickon (in a strict sense) in Philadelphia of probable 

Late Proterozoic and (or) Early Cambrian age. These compose the Potomac terrane (fig. 6) of Horton and others 

(1989). A more conservative interpretation of the "Wissahickon" was previously taken in the Pennsylvania Piedmont, where it was mapped as stratigraphically overlying 

the Cockeysville Marble. However, recent workers (for 

example, Crawford and Mark, 1982; Wagner and Srogi, 

1987; Faill and MacLachlan, 1989) recognized that the 

"Wissahickon" may be allochthonous and composed of several distinct lithologic units. Crawford (1991) stated that the 

current interpretation for the "Wissahickon" in Pennsylvania and Delaware is that it probably represents a sequence 

of deepwater marine sediments that contains volcanic rocks 

and tectonically emplaced slices of ultramafic rocks. Thus,

rocks south of the Cream Valley fault are termed Wissahickon or Peters Creek Schist, depending on their stratigraphic position. Faill and MacLachlan (1989) assigned all 

of the rocks south of the Cream Valley-Huntingdon Valley 

fault system and east of the West Chester prong to the Philadelphia terrane and those rocks to the west to the Brandywine terrane (collectively, the Potomac terrane of Horton 

and others, 1989).

In the Maryland Piedmont, the Middle Proterozoic 

Baltimore Gneiss crops out in a series of domelike structures. It is unconformably overlain by a lower Paleozoic 

succession of clastic and shelf carbonate rocks, which are 

the Setters Formation and the Cockeysville Marble, respectively (Hopson, 1964; Crowley, 1976). The Baltimore 

Gneiss, Setters Formation, and Cockeysville Marble constitute the Baltimore terrane of Horton and others (1989) 

(fig. 6).

These are tectonically overlain by the Loch Raven 

Schist and the Oella Formation (Crowley, 1976), an interlayered sequence of meta-arenite and schist. Both units contain blocks of ultramafic rock. At different places, the thrust 

sheet containing the Loch Raven Schist and Oella Formation overlies either the Baltimore Gneiss, the Setters Formation, and (or) Cockeysville Marble (map in Crowley, 1976). 

It also overlies the Laurel Formation, a precursory sedimentary melange that contains olistoliths of Loch Raven Schist 

and Oella Formation (Fleming and others, 1994; A.A. 

Drake, Jr., unpub. data).

To the west of the Baltimore terrane, the Loch Raven 

thrust sheet is tectonically overlain by the Sykesville Formation, a precursory sedimentary melange (Drake, 1986). A 

thrust sheet of ultramafic rock, the Soldiers Delight Ultramafite, lies between these thrust sheets in central Maryland 

(A.A. Drake, Jr., unpub. data). The Sykesville Formation is 

tectonically overlain by the Mather Gorge Formation that 

was miscorrelated with the Peters Creek Schist by Drake 

and Morgan (1981). All these units are part of the Potomac 

terrane of Horton and others (1989). The Potomac terrane is 

tectonically underlain by rocks of the Westminster terrane 

(Drake, 1986; Horton and others, 1989) (fig. 6).

To the east of the Baltimore terrane, rocks of the Potomac terrane are tectonically overlain by the mafic and ultramafic rocks of the Baltimore Complex (Bel Air-Rising Sun 

terrane of Horton and others, 1989; this report, fig. 6). 

Crowley (1976) interpreted the James Run Formation (Chopawamsic terrane of Horton and others, 1989; this report, 

fig. 6) to tectonically overlie the Baltimore Complex. In 

exposures along the Patapsco River near Relay, Md., however, the units are separated by a zone of west-dipping 

mylonitic foliation, suggesting that the Baltimore Complex 

overlies the James Run Formation (A.A. Drake, Jr., unpub. 

data). Tectonostratigraphic relations of the various terranes 

adjacent to New Jersey are shown in figure 7.

The Wilmington Complex crops out in the Delaware 

and Pennsylvania Piedmont just west of Salem and
CRYSTALLINE BASEMENT BENEATH THE NEW JERSEY COASTAL PLAIN AND CONTIGUOUS AREAS B7

EXPLANATION 

Kr I Raritan Formation 

Is | Stockton Formation 

€Zs I Serpentinite 

CZm 1 Manhattan Schist

Contact-Dotted where concealed

Fault, approximately- u, uptnfown siqe 

d, downthrown side

Thrust fault-Dotted where concealed

-- -.,. €Zm H: si to 1 : iLr~' • •

3 MILES

I I I I 

0123 KILOMETERS

Figure 5. Geologic map of the Hoboken, N.J., area. Compiled from Mueser Rutledge Consulting 

Engineers (1986), Lyttle and Epstein (1987), Tarns Consultants, Inc. (1988), R.A. Volkert (unpub. 

data), and unpublished New Jersey Geological Survey permanent notes (undated).

Gloucester Counties in New Jersey (fig. 6). As mapped by 

Ward (1959} and Woodruff and Thompson (1975), the 

Wilmington Complex consists of a sequence of mafic rocks 

of gabbroic, noritic, anorthositic, and charnockitic composition (Arden pluton), as well as a sequence of layered, twopyroxene-bearing gneisses (Wagner and Srogi, 1987). The 

gneisses were intruded by the Arden pluton from which 

Poland and Muessig (1978) obtained a Rb-Sr whole-rock 

age of 502 Ma, suggesting that it is Cambrian or older. Layered gneisses associated with the Wilmington Complex

have been interpreted to be metavolcanic and volcaniclastic 

by several Piedmont geologists (for example, Southwick, 

1969; Higgins, 1972; Crawford and Crawford, 1980) who 

have correlated them with rocks of the Cambrian James Run 

Formation in Maryland, the Chopawamsic Formation in 

Virginia, and other Cambrian rocks of island arc affinity in 

the Piedmont. Horton and others (1989) disagreed with this 

correlation and interpreted the layered gneisses of the 

Wilmington Complex to be Cambrian or older, perhaps 

even Middle Proterozoic in age, and speculated that the
B8 GEOLOGIC STUDIES IN NEW JERSEY AND EASTERN PENNSYLVANIA

78° 76°

40°

78°

CHOPAWAMSIC TERRANE

(James Run Formation) 

BEL AIR-RISING SUN 

TERRANE\(ABERDEEN BLOCK)

BEL AIR-RlSING^SUN 

TERRANE (MAIN BLOCK)

CHOPAWAMSIC TERRANE

\

\

\

\

40°

76°

EXPLANATION

Peach Bottom Slate (Ordovician)

Occoquan Granite (Ordovician)

DISRUPTED TERRANES

Potomac terrane

POSSIBLE OCEANIC CRUST

VOLCANIC-ARC TERRANES

Chopawamsic terrane

METAMORPHIC COMPLEXES OF 

UNCERTAIN ORIGIN

Possible continental fragments 

(Crabtree, Gaffney, Goochland, 

and Wilmington terranes)

Laurentia

i i i i i Mesozoic normal fault (latest

movement is post-accretionary)

Paleozoic terrane boundaries and selected faults

Allochthonous offshore sequences 

(Hamburg and Westminster 

terranes)

Internal continental terranes 

(Baltimore, Sauratown, and 

Pine Mountain)

Thrust fault, sawteeth on upper 

plate

Strike-slip fault, showing relative 

horizontal movement

Fault, sense of movement uncertain

Terrane boundary concealed by 

Coastal Plain sediments (interpreted 

on the basis of geophysical and 

drill-hole data)

Northwest limit of Coastal Plain onlap 

(Cenozoic and Cretaceous)

Figure 6. Tectonostratigraphic terrane map of the central Appalachians. Modified from Horton and others (1989).
CRYSTALLINE BASEMENT BENEATH THE NEW JERSEY COASTAL PLAIN AND CONTIGUOUS AREAS B9

Goochland terrane

Montpelier metanorthosite

Maidens Gneiss 

Sabot amphibolite 

State Farm Gneiss

Wilmington terrane

Arden Pluton 

Layered gneisses

Chopawamsic terrane

Chopawamsic Formation 

James Run Formation

Bel Air-Rising Sun terrane

Baltimore Mafic Complex

Potomac/Philadelphia/Brompton-Cameron terrane

Sykesville Formation

Peters Creek Schist

Piney Run Formation

Oella Formation

Wissahickon Formation (sensu stricto) 

plus

rocks in Connecticut Valley Synclinorium 

east of Cameron's Line

Westminster terrane

Pretty Boy Schist

Octoraro Phyllite

allochthonous Hoosac Formation

plus 

Manhattan Schist B and C (?)

Baltimore/North American Craton terrane

Walloomsac Formation 

Stockbridge Marble

Inwood Marble

Cheshire Quartzite

Dalton Formation

Lowerre Quartzite

Yonkers Gneiss

Fordham Gneiss

plus

Loch Raven Schist

Cockeysville Marble

Setters Formation

Baltimore Gneiss

4- Figure 7. Tectonostratigraphic sequence showing generalized relation of terranes of the north-central and southern northern Appalachians. Compiled from Crowley (1976), Hall 

(1976), Crawford and Mark (1982), Stanley and Ratcliffe 

(1985), Drake (1986), Faill and MacLachlan (1989), Horton 

and others (1989), and Zen and others (1989). Terranes are 

listed in their inferred stacking order with the highest thrust 

sheet at the top and the lowest thrust sheet at the bottom.

Wilmington terrane (fig. 6), which they envisioned to be 

thrust over rocks of the Chopawamsic terrane, may be an 

extension of the Goochland terrane (fig. 6). Horton and 

others (1989), however, showed these terranes separately on 

their map.

It is tempting to correlate the exposed crystalline rocks 

in the Manhattan prong with those in the Pennsylvania and 

Maryland Piedmont. There are, however, problems in doing 

so. Some workers (for example, Higgins, 1972; Muller and 

Chapin, 1984) thought that the Setters Formation and Cockeysville Marble, the cover rocks that overlie Grenville basement, were Late Proterozoic or earliest Cambrian in age, 

hence older than the Lowerre and Inwood in the Manhattan 

prong. Other workers (for example, Crowley, 1976) considered them to be Cambrian to Ordovician in age. The age of 

rocks called "Wissahickon" Formation has been a problem. 

For example, Drake (1986), Lyttle and Epstein (1987), and 

Horton and others (1989) interpreted them to be Late Proterozoic or earliest Cambrian in age. Others (for example, 

Higgins, 1972; Muller and Chapin, 1984) thought that the 

"Wissahickon" ranged in age from Late Proterozoic to 

Ordovician but was mostly Cambrian. We think that the 

autochthonous cover sequence rocks overlying Proterozoic 

basement, namely the Lowerre and Inwood, and the Setters 

and Cockeysville are correlative, whether Late Proterozoic 

or early Paleozoic, because of their respective structural 

relations, their stratigraphy, and lithologic descriptions in 

Hopson (1964), Crowley and others (1975), Muller and 

Chapin (1984), and Hall (1976; in press). All of them are 

included here in the Baltimore terrane of Horton and others 

(1989) and its equivalent, the North American Craton terrane of Zen and others (1989).

We agree that rocks in the Potomac terrane have been 

thrust westward over the Laurentian craton and its cover as 

suggested by some workers (for example, Crawford and 

Crawford, 1980; Wagner and Srogi, 1987; Horton and others, 1989). We think that rocks in the Manhattan prong at 

least through the Inwood Marble would structurally underlie rocks equivalent to the Wissahickon Formation (in a 

strict sense) and other parts of the Potomac terrane. This 

interpretation suggests that the Manhattan Schist as used by 

Hall (in press), the allochthonous Hoosac Formation and 

equivalent units in New England, and the Octoraro Phyllite 

in Pennsylvania are correlative and structurally underlie 

Potomac terrane rocks. This correlation is supported by the 

fact that in New England, the Rowe Schist, which contains
BIO GEOLOGIC STUDIES IN NEW JERSEY AND EASTERN PENNSYLVANIA

ultramafic rocks and basaltic amphibolite, was thrust westward over albite schist and phyllite of the allochthonous 

Hoosac Formation (Stanley and Ratcliffe, 1985). Similarly, 

the Peters Creek Schist and "Wissahickon" both contain 

mafic and ultramafic rocks and were interpreted by Lyttle 

and Epstein (1987) to have been thrust westward over albite 

schist and phyllite (Prettyboy Schist and Octoraro Phyllite, 

respectively). However, once again, age is a problem, as the 

Peters Creek and "Wissahickon" are considered to be Late 

Proterozoic to earliest Cambrian in age, whereas analogous 

rocks in the Manhattan prong (Hartland Formation) and in 

New England (Rowe Schist) are considered to be Ordovician in age (Stanley and Ratcliffe, 1985; Hall, in press). 

We note, however, that the ages of these rocks are not well 

constrained.

GEOPHYSICAL DATA

Gravity and aeromagnetic maps constitute the principal geophysical data sets available for interpretation of the 

basement rocks beneath the Coastal Plain of New Jersey. 

Gravity maps by Bonini (1965) and the Society of Exploration Geophysicists (1982) and aeromagnetic maps by the 

U.S. Geological Survey (1979) and Zeitz and Gilbert (1981) 

were used.

GRAVITY DATA

Bouguer gravity maps of the New Jersey Coastal Plain 

display generalized patterns, which are part of the more 

extensive Appalachian trends (fig. 8). The most obvious 

gravity feature is the linear negative-positive couplet, which 

is part of the Appalachian gravity gradient (AGG) (Cook 

and others, 1979). This feature consists of a gravity low on 

the northwest, which reaches a minimum value of-100 milligals in the Valley and Ridge province, and an adjacent 

gravity high. This high trends from Staten Island south 

through the Raritan Bay, peaking near Prospertown, N.J., at 

more than 40 milligals; it continues southwestward through 

Deptford, N.J., and to the Wilmington Complex in Delaware. Bonini (1965) referred to this positive gravity anomaly as the trans-New Jersey gravity high.

The AGG is interpreted to result from the transition of 

rifted, thinned, and intruded continental crust into denser 

oceanic crust (Cook and others, 1979). Crustal thinning and 

extension preceded the opening of the lapetus Ocean basin 

during the Late Proterozoic and early Paleozoic. Regional 

gravity models in Virginia (Pratt and others, 1988) and in 

New Jersey (Sugarman, 1981) demonstrated that shallowing 

of the mantle from a depth of 25 to approximately 18.6 mi is 

sufficient to achieve the observed Bouguer gravity anomaly 

pattern.

Southeast of the AGG, a more intricate series of gravity anomaly patterns contains two oval gravity lows, which

are separated near Tabernacle, N.J. The northern gravity 

low extends offshore of the northern part of the New Jersey 

Coastal Plain, whereas the southern low continues under the 

Delaware Coastal Plain to the south of the Wilmington 

Complex. Southeast of this gravity low is a gravity high that 

exceeds 30 milligals near Manahawkin, NJ. This anomaly 

may be part of the broader positive feature that extends 

from North Carolina to New Jersey and is associated with a 

linear positive magnetic anomaly. However, just north of 

Leonardtown, Md., there is a sharp termination of both the 

gravity and magnetic anomalies, and it is unclear whether 

any anomalies to the north are a continuation (D.L. Daniels, 

written commun, 1993). Southeast of this positive anomaly, 

the Bouguer gravity anomaly decreases to a low of -25 

milligals at Cape May, NJ.

Sheridan and others (1991) interpreted the gravity high 

to result from high-density thrust slices of ophiolite, metavolcanic rock, and melange. According to their interpretation, the gravity low to the northwest marks the location of a 

buried Mesozoic basin. No density variations were needed 

below a 5 mi depth, as seismic-reflection data (Sheridan and 

others, 1991) do not indicate any large lateral velocity contrasts.

AEROMAGNETIC DATA

Aeromagnetic maps are excellent tools for studying the 

basement, as the sediments of the Coastal Plain have very 

weak magnetic susceptibilities in contrast to susceptibilities 

of some of the crystalline rocks. Consequently, it is assumed 

that the major aeromagnetic anomalies result from compositional and structural contrasts in the basement and that their 

gross trend is controlled by the regional grain of the basement rocks.

In general, the aeromagnetic map (fig. 9) shows two 

basic anomaly patterns beneath the New Jersey Coastal 

Plain: (1) in the inner Coastal Plain, an area characterized 

primarily by short-wavelength anomalies typical of the 

exposed Piedmont and (2) in the outer Coastal Plain, an area 

of broader, lower amplitude anomalies, which reflect the 

greater depth to basement.

The amplitudes of the anomalies on the aeromagnetic 

map generally correlate with the configuration of the basement surface. In areas of high-amplitude anomalies, the 

basement surface is high relative to the surrounding basement. For example, Sugarman (1981) studied the positive 

magnetic and residual Bouguer gravity anomalies near 

Marlboro, NJ. (figs. 8, 9), and suggested the presence of 

mafic rocks either in a pluton or a thrust slice. A regional 

basement structural high (fig. 10) is associated with these 

anomalies. A similar model was proposed for the Iron Hill 

in Delaware by Maguire (1980) and the Staten Island Serpentinite by Yersak (1977). Another short-wavelength magnetic anomaly, or series of anomalies, occurs near Mount
CRYSTALLINE BASEMENT BENEATH THE NEW JERSEY COASTAL PLAIN AND CONTIGUOUS AREAS B11

0 25 50 75 KILOMETERS

Figure 8. Bouguer gravity anomaly map of New Jersey and contiguous areas. Modified from Society of Exploration Geophysicists 

(1982). Contour interval 5 milligals.
B12 GEOLOGIC STUDIES IN NEW JERSEY AND EASTERN PENNSYLVANIA

75°

40°

50 MILES 

I

50 KILOMETERS

Figure 9. Aeromagnetic map of New Jersey and contiguous 

areas. Total intensities are shown in hundreds of gammas. Modified from Zietz and Gilbert (1981). Contour interval 200 gammas.

Holly in northwestern Burlington County. These anomalies 

are along the western part of the South Jersey high (fig. 1) 

and also are associated with a regional basement high (fig. 

10). We interpret the anomalies and disruption in the basement seen in the basement surface contours in figure 10 

near Mount Holly to be due to mafic rocks in a pluton 

or thrust slice similar to that proposed for the body near 

Marlboro.

DESCRIPTION OF WELL SAMPLES 

INTRODUCTION

Most of the wells in New Jersey penetrating crystalline 

basement are concentrated along the northwestern edge of 

the Coastal Plain where bedrock is encountered at relatively 

shallow depths (fig. 10). To the south and east, deep wells 

are fewer and are widely separated. Except for the few published reports (Southwick, 1964; U.S. Geological Survey, 

1967; Daniels and Leo, 1985), lithologic descriptions from 

this part of the State are known mainly from nondescript 

water well records. Where samples are available, many are 

saprolitic. Saprolite thicknesses of as much as 150 ft have 

been encountered beneath the New Jersey Coastal Plain, 

with the result that few fresh basement samples are available for study. Consequently, these basement rocks have 

remained poorly understood, and prior attempts to correlate 

them with distantly outcropping crystalline rocks elsewhere 

were problematic and conjectural at best (for example, 

Southwick, 1964).

As one objective of this study, well samples of fresher 

rock were analyzed petrographically where possible in order 

to define their gross mineralogy (table 1). This included the 

analysis of thin sections as well as rotary cuttings. The following county-by-county descriptions involve only new 

data resulting from this study and older data based on reliable sources. A complete listing of all wells used in this 

study that penetrate basement rock is given in the appendix.

CAPE MAY COUNTY

The deepest well that encountered basement in New 

Jersey for which samples are available is the Anchor Gas 

Dickinson well (appendix, well no. 104), which penetrated 

rock at a depth of about 6,300 ft below land surface. The 

samples remaining from the original well cuttings are of a 

fine-grained, grayish-black to greenish-black gabbro containing plagioclase, hornblende, trace amounts of biotite 

and sulfide, and minor amounts of quartz. No other wells to 

basement are known from Cape May County.

CUMBERLAND COUNTY

The Anchor Gas Ragovin well (appendix, well no. 

103) drilled a fine-grained, quartz-rich rock containing trace 

amounts of accessory garnet. No feldspar was seen in the 

washed cuttings. However, a few small rock fragments from 

a depth of 3,700 to 3,710 ft contained chalky, fine-grained, 

highly altered feldspar. This appears to be a metaquartzite, 

possibly feldspathic in part. Most of the sample from the 

bottom of this well was of a coarse, angular quartz sand 

containing siderite nodules, probably representative of the 

Potomac Formation. The very bottom of the well appears to
CRYSTALLINE BASEMENT BENEATH THE NEW JERSEY COASTAL PLAIN AND CONTIGUOUS AREAS B13

75°30' 75' 74° 30'

40° 30

39° 30

39°

Figure 10. Location map of wells penetrating basement rock in New Jersey and contiguous areas. Structure contours are drawn on top of 

basement surface. Well numbers are same as in appendix.
B14 GEOLOGIC STUDIES IN NEW JERSEY AND EASTERN PENNSYLVANIA

Table 1. Modal analyses of selected basement rocks. 

[Analyses are based on 1,200 points. Analyst: R.A. Volkert; —, no data]

Mineral

Total

CL

100

SH S&S GAV-22 IBP DUR-246 DUR-199

100 100 100 100 100 100

GAV-17

Plagioclase

Quartz

Biotite

Muscovite

K-feldspar

Hornblende

Garnet

Tourmaline

Sillimanite

Opaque 1

Chlorite

Apatite

Zircon

Other2

39.8

37.7

18.5

2.8

—

—

.5

.1

trace

.4

trace

.1

.1

trace

35.95

35.90

18.50

8.30

.75

—

trace

—

—

.2

trace

.2

.2

trace

36.2

45.5

14.6

—

—

—

.1 —

_

1.9

.4

.1

.2

1.0

28.5

45.0

16.2

8.6

—

—

.4

—

trace

.9

trace

.3

.1

trace

40.4

34.4

18.6

.7

3.6

—

.1

trace

—

.2

.1

.2

trace

1.7

36.6

22.1

29.6

—

—

7.6

1.5

—

trace

2.4

trace

.2

trace

trace

53.7

.4

2.6

—

—

36.9

—

—

—

5.1

.3

trace

trace

1.0

45.6

.7

—

—

—

48.9

—

—

—

3.1

.4

trace

trace

1.3

100

'Opaque minerals include magnetite, ilmenite, and pyrite.

2Includes alteration products and carbonate, plus trace amounts of titanite and epidote.

Description of samples

CL Psammitic schist from Chemical Leaman well (appendix, well no. 89)

SH Pelitic schist from Shoemaker Farm well (appendix, well no. 92)

S&S Psammitic schist from S&S Auction well (appendix, well no. 90)

GAV-22 Psammitic schist from Gaventa Farms well (appendix, well no. 88)

IBP Average of five thin sections from 3,873 ft to 3,881 ft below land surface. Based on 6,337 points from Southwick (1964) from the U.S. Geolog- 

	ical Survey Island Beach State Park well (appendix, well no. 46) 

DUR-246 Basaltic andesite from OuPont Repauno Works well (appendix, well no. 85) 

DUR-199 Amphibolite from DuPont Repauno Works well (appendix, well no. 85) 

GAV-17 Amphibolite from Gaventa Farms well (appendix, well no. 88)

have barely penetrated the basement surface. No additional 

wells into basement are known from Cumberland County.

ATLANTIC COUNTY

No wells into basement are known from Atlantic County.

OCEAN COUNTY

The U.S. Geological Survey test well (appendix, well 

no. 46) drilled at Island Beach State Park in the 1960's 

penetrated basement at a depth of about 3,800 ft. Southwick (1964) described the rock as a medium-grained, locally migmatitic, gamet-muscovite-microcline-biotite-quartzplagioclase gneiss. His description omits a medium-grained 

garnet-hornblende-biotite-quartz-feldspar gneiss recovered 

from the bottom of the hole at a depth of 3,890 ft. The thickness of the hornblende-bearing phase of the gneiss is 

unknown because only a single piece of core exists. Its contact with the overlying gneiss is conformable and gradational. The foliation at 3,890 ft dips at about 35°.

The Oxly 1A well (appendix, well no. 45), drilled in 

the southern part of Ocean County, encountered a lightpinkish-tan saprolite of decomposed schist or gneiss containing chlorite, muscovite, biotite, quartz, highly altered 

feldspar (plagioclase?), trace amounts of sulfide, and a few 

grains of graphite.

The most noteworthy well from Ocean County is the 

W.&K. Oil Company well (appendix, well no. 42) drilled 

about 1920 at Jacksons Mills. New Jersey Geological Survey permanent notes by former State Geologist Henry 

Kiimmel dated February 1922 state:

gneiss was penetrated at about 1,900 ft in well no. 2 and limestone and 

sandstones found in which were Paleozoic fossils (Ordovician)... At the 

contact of the gneiss on the supposed Ordovician there was a 5-ft bed of 

clayey material containing bits of gneiss and limestone, the description 

indicating a fault breccia or "gouge" in a vein. The data appear to indicate 

the occurrence of an overthrust mass of gneiss on Ordovician strata.

Unfortunately, no description of the Paleozoic section 

drilled or the fossils contained within it exists, nor is there 

any reference to who identified them or the current whereabouts of the fossils. We know that Kttmmel was never permitted direct access to the drilling site and relied on indirect
CRYSTALLINE BASEMENT BENEATH THE NEW JERSEY COASTAL PLAIN AND CONTIGUOUS AREAS B15

information for his interpretation. If this report is valid, the 

thrust fault would have to exist between 1,900 and 3,000 ft 

below land surface. Reexamination of the cuttings from the 

3,000- to 4,850-ft interval for this study indicates that the 

rock is a medium-fine-grained schist containing biotite, 

quartz, altered feldspar, sparse pale pink garnet, and trace 

amounts of sulfide. The section from 4,832 to 4,840 ft 

contains trace amounts of graphite. At 4,850 ft, the rock 

is a medium-fine- to medium-grained biotite-chlorite-muscovite-quartz-feldspar schist containing trace amounts of 

garnet and possible sillimanite. Apparently, the samples 

from below 4,851 and above 3,000 ft no longer exist.

The other wells in Ocean County (appendix, well nos. 

41, 43, and 44) all encountered nondescript saprolite or bedrock.

MONMOUTH COUNTY

Most of the samples obtained from wells in Monmouth 

County are of micaceous schist or gneiss containing muscovite, biotite, quartz, and altered, chalky feldspar. The U.S. 

Geological Survey Freehold observation well (appendix, 

well no. 38) cut a weathered, medium-fine-grained schist 

containing abundant biotite, quartz, and altered, chalky feldspar, as well as sparse amounts of pink garnet and trace 

amounts of graphite. Schistosity in the core dips at a moderate angle.

The New Jersey Highway Authority well (appendix, 

well no. 35) encountered weathered, fine- to medium-finegrained chlorite-biotite-muscovite-quartz-feldspar schist 

containing trace amounts of staurolite and graphite.

The Levitt & Sons, Inc., well (appendix, well no. 34) 

drilled a saprolitic mica schist that, according to the description (F.J. Markewicz, unpub. lithologic log), either was 

locally migmatitic or was intruded by granite.

MIDDLESEX COUNTY

Limited information is available from wells in Middlesex County. The lithologic descriptions are mostly of saprolitic material. The Madison Water Company well (appendix, 

well no. 17) penetrated micaceous greenish-gray saprolite. 

The two Clifford Stultz wells (appendix, well nos. 22 and 

23) encountered saprolite containing quartz and feldspar 

that was called "Wissahickon" by Johnson (1961). One 

sample contained hornblende. These three wells are in the 

southeastern part of the county. Most of the wells in central 

and eastern Middlesex County are in rocks of the Newark 

basin. The Chevron Oil Company well (appendix, well no. 

4a) in the northeastern part of the county drilled serpentinite 

(reported as "soapstone" by Gronberg and others, 1989), 

apparently a continuation of the outcropping body on Staten 

Island.

MERCER COUNTY

Most of the available well data from southern and eastern Mercer County list micaceous schist or gneiss labeled 

"Wissahickon" on the well records; the constituent mineralogy is not recorded. However, given the geographic location of these wells, a correlation with the Wissahickon 

Formation is certainly reasonable. In the south-central part 

of the county, the 270-ft-deep New Jersey Geological 

Survey Mercer County Park test hole (appendix, well 

no. 27) encountered a variety of rock types dominated 

by medium-grained, light-greenish-gray hornblende-pyroxene-quartz-biotite-plagioclase gneiss containing sparse sulfide. Above the gneiss is massive, light-tan clinopyroxenequartz-microperthite granulite. Intruding the gneiss is massive, pinkish-white-weathering, medium- to coarse-grained 

micro-perthite alaskite containing blue quartz. The contact 

between the gneiss and these granitic rocks is sharp and 

conformable with gneissic foliation. Also intruding the 

gneiss at a depth of 226 to 260 ft is greenish-gray, finegrained to aphanitic, retrogressively metamorphosed metabasalt. Foliation dips at an angle of about 35°-40° throughout the sampled interval. A thin ductile shear zone was 

observed at a depth of about 147 ft. Mineralized brittle fractures overprint this shear zone at a high angle. Several other 

sheared intervals were encountered deeper in the hole. 

These rocks probably are part of the heterogeneous Middle 

Proterozoic basement exposed near Trenton.

BURLINGTON COUNTY

Most of the wells concentrated along the northwestern 

edge of Burlington County and at least as far east as those at 

McGuire Air Force Base (appendix, well nos. 49 and 50) 

penetrated micaceous schist or gneiss. Where mineralogical 

descriptions are given, the rock consists dominantly of biotite, quartz, and weathered feldspar. The schistose gneiss 

from the Cinnaminson well (appendix, well no. 64) is a 

saprolitic, gray, medium-fine- to medium-grained rock that 

contains muscovite subordinate to biotite and sparse pink 

garnet. The dominant feldspar is plagioclase.

The Butler Place test well (appendix, well no. 53), 

drilled in the easternmost part of this county, penetrated a 

fine-grained, greenish-gray rock consisting of 40 percent 

carbonate plus phlogopite, chlorite, clay minerals, and 

minor quartz (U.S. Geological Survey, 1967). Unfortunately, samples of this core no longer are available. This 

well is particularly noteworthy in that carbonate rock was 

not encountered elsewhere in the New Jersey subsurface. 

The dimensions of this carbonate unit, as well as companion 

lithologies, remain unknown since no other wells to basement were drilled nearby. The closest wells are the Burlington County Institution well (appendix, well no. 52) to the 

northwest and the Oxly 1A well (appendix, well no. 45) to
B16 GEOLOGIC STUDIES IN NEW JERSEY AND EASTERN PENNSYLVANIA

the southeast. Both wells are over 10 mi from the Butler 

Place well, and lithologic descriptions are lacking from the 

Burlington County Institution well.

CAMDEN COUNTY

As in Burlington County, most of the wells along the 

western and northern edges of Camden County were drilled 

in micaceous schist or gneiss. An exception is the Pennsauken SLF well (appendix, well no. 70) that returned a 

yellowish-tan decomposed schist or gneiss containing muscovite, quartz, and kaolinite.

The U.S. Geological Survey New Brooklyn Park well 

(appendix, well no. 79) in the southwestern part of the 

county drilled a pale-greenish-gray, fine- to medium-grained biotite-muscovite-quartz-plagioclase schist or gneiss that 

locally contains abundant pink garnet. No sillimanite was 

seen in the core in this study, although the U.S. Geological 

Survey (1967) reported sillimanite in some of the core. The 

garnet must occur locally as well, as the U.S. Geological 

Survey did not mention it in the sample USGS workers 

studied.

GLOUCESTER COUNTY

The freshest samples examined during this study were 

of core from a series of wells along the western edge of 

Gloucester County. These include the Gaventa Farms, 

Lopes Farm, and Shoemaker Farm wells (appendix, well 

nos. 88, 91, and 92, respectively) and the Chemical Leaman, 

S&S Auction, and DuPont Repauno Works wells (appendix, well nos. 89, 90, and 85, respectively). The U.S. Geological Survey Deptford and Clayton wells (appendix, well 

nos. 83 and 95, respectively) returned somewhat more 

weathered rotary cuttings.

The Gaventa Farms well (appendix, well no. 88) 

drilled (from top to bottom) a layered sequence of 

metapelite, amphibolite, and metagraywacke. The metagraywacke is medium fine to medium grained and contains 

muscovite, biotite, quartz, and plagioclase, with minor 

amounts of garnet and trace amounts of sillimanite and sulfide (table 1). The metapelitic schist is medium grained and 

contains essentially the same mineralogy plus minor K-feldspar. The foliated amphibolite dominantly contains hornblende and plagioclase (table 1). Contacts between the 

metapelite and the metagraywacke are gradational, whereas 

the schist/amphibolite contacts are sharp. All of the contacts 

observed in the core are conformable with schistosity. 

Schistosity is gently dipping throughout the section and 

ranges from subhorizontal to about 20°.

The Lopes Farm well (appendix, well no. 91) encountered a medium-grained schist containing muscovite, biotite, quartz, and plagioclase. No garnet or sillimanite was 

noted in the small amount of core from this well. The Shoemaker Farm well (appendix, well no. 92) drilled a 

medium-grained pelitic schist similar to that from the 

Gaventa Farms well. It contains muscovite, biotite, quartz, 

and plagioclase with minor amounts of K-feldspar and trace 

amounts of garnet and sulfide (table 1). This core is locally 

migmatitic, containing O.l-in.-thick leucocratic seams of 

quartz and plagioclase. Schistosity is crenulated but dips at 

an average of about 40°.

The Chemical Leaman well (appendix, well no. 89) 

returned a layered sequence of (top to bottom) schistose 

metapelite and metagraywacke. A sample of medium-fineto medium-grained metagraywacke contains muscovite, 

biotite, quartz, and plagioclase, with minor amounts of garnet and tourmaline and trace amounts of sillimanite and 

sulfide (table 1). Contacts between the pelitic and psammitic parts of the section appear to be gradational. Schistosity is uniformly subhorizontal throughout the core.

The S&S Auction well (appendix, well no. 90) encountered medium-grained schistose metagraywacke composed 

of biotite, quartz, and plagioclase with minor amounts of 

garnet (table 1). The core from a depth of 401 ft is cut by 

brittle fractures and by a 6-in.-thick vein of quartz that dips 

about 35° to 40° and that is subparallel to the dip of the 

schistosity.

The DuPont Repauno Works (appendix, well no. 85) 

actually consists of a cluster of nine wells that returned 

dominantly metapelite and metagraywacke schist having a 

mineralogy quite similar to that of the aforementioned well 

samples with or without garnet and sillimanite locally. Contacts between the metapelite and metagraywacke are everywhere gradational and conformable. Also encountered was 

a medium-grained schist containing biotite, hornblende, 

quartz, and plagioclase, with minor amounts of garnet and 

sillimanite (table 1, sample DUR-246) that has the composition of basaltic andesite (table 2). The meta-andesite 

occurs in thin to thick layers with metapelite, with which it 

has a conformable contact. No contacts between the 

meta-andesite and metagraywacke were noted in these 

wells.

Two principal types of amphibolite were seen in samples from the DuPont Repauno Works wells. They include 

medium-grained, foliated, grayish-black gneiss to schistose 

gneiss containing hornblende and plagioclase with minor 

amounts of biotite (table 1) and medium-fine- to mediumgrained, grayish-black to black, less foliated, locally mottled gneiss to schistose gneiss containing dominantly hornblende and plagioclase. Despite the similar mineralogy, 

these amphibolites have a markedly different chemistry that 

will be discussed further on in this report.

Schistosity in the core from these wells is variable in 

dip due to folding and ranges from about 10° to subvertical. 

Dips in core from wells to the west generally are steeper, 

ranging from about 30° to 90°, whereas dips toward the east 

are gentler and range from about 10° to 50°. Folds have 

locally been refolded into type 2 dome-crescent-mushroom
CRYSTALLINE BASEMENT BENEATH THE NEW JERSEY COASTAL PLAIN AND CONTIGUOUS AREAS B17

Table 2. Chemical analyses of selected basement rocks.

[Major-oxide compositions except FeO were determined by X-ray fluorescence. FeO was determined by wet chemical methods. Traceelement abundances were determined by X-ray fluorescence. Rare earth element abundances and Th, Hf, and la were determined by instrumental neutron activation. All analyses by XRAL Activation Services, Ann Arbor, Mich. —, no data]

CL SH S&S GAV-21 DUR-398 DUR-256 IBP

Major-oxide composition, in weight percent, and loss on ignition (LOT)

SiO2 

TiO2 

A1203 

Fe2O3 

FeO

MgO 

CaO

Na2O 

K20

MnO

LOI

Total

76.80 

.55 

10.90 

1.11 

2.20

1.28 

1.37

3.11 

1.58 

.18

.10

.46

99.64

63.40 65.00 64.70 

.90 .85 .77 

15.80 14.20 15.40 

2.69 2.28 1.82 

4.30 4.30 4.10

2.77 2.83 2.49 

1.28 2.78 2.09

2.52 2.29 4.39 

4.20 2.48 2.36 

.17 .12 .08

.17 .09 .12

1.23 1.39 .62

99.43 98.61 98.94

60.90 

.88 

18.10 

2.90 

4.50

2.81 

.74

1.88 

4.26 

.16

.20

1.77

99.10

67.30 

1.20 

13.30 

2.94 

3.70

1.66 

3.01

3.24 

1.68

.22

.14

.39

98.78

68.60 

.56 

14.50 

1.53 

3.30

2.01 

2.37

3.51 

2.31 

.11

.09

.93

99.82

TVace-element abundances, in parts per mUlion

Ba

Co

Cr

Hf

Nb

Ni

Rb

Sc

Sr

Ta

Th

V

Y

Zr

330

—

50

—

10

—

100

—

110

—

—

—

10

210

670 510 770

— — —

80 100 70

— — —

40 20 20

— — —

230 110 120

— — —

90 160 220

— — —

— — —

— — —

40 <10 30

190 230 210

860

—

90

—

30

—

180

—

110

—

—

—

30

190

800

—

60

—

20

—

80

—

270

—

—

—

30

620

540

—

20

—

30

—

100

—

160

—

—

—

20

180

Rare earth element abundances, in parts per million

La

Ce

Nd

Sm

Eu

Tb

Yb

Lu

CL 

SH 

S&S 

GAV-21 

DUR-398 

DUR-256 

IBP

_

—

—

—

—

—

—

—

_ _ _

— — —

— — —

— — —

— — —

— — —

— — —

— — —

Description of samples

—

—

—

—

—

—

—

—

—

—

—

—

—

—

—

—

—

—

—

—

—

—

—

—

Psammitic schist from Chemical Leaman well (appendix, well no. 89) 

Pelitic schist from Shoemaker Farm well (appendix, well no. 92) 

Psammitic schist from S&S Auction well (appendix, well no. 90) 

Psammitic schist from Gaventa Farms well (appendix, well no. 88) 

Pelitic schist from DuPont Repauno Works well (appendix, well no. 85) 

Psammitic schist from DuPont Repauno Works well (appendix, well no. 85) 

Migmatitic gneiss from the U.S. Geological Survey Island Beach State Park well (appendix, well no. 46)
B18 GEOLOGIC STUDIES IN NEW JERSEY AND EASTERN PENNSYLVANIA 

Table 2. Chemical analyses of selected basement rocks—Continued.

DUR-199 MCP-228 DUR-206 GAV-17 DUR-185 DUR-137 DUR-246

Major-oxide composition, in weight percent, and loss on ignition (LOI)

SiO2 

TiO2 

A12O3 

Fe203 

FeO

MgO 

CaO

Na2O 

K2O

MnO

LOI

Total

48.70 

3.77 

12.70 

8.10 

9.80

4.78 

7.85

1.70 

.65 

.54

.26

.39

99.24

49.00 49.50 49.50 

3.67 3.70 1.63 

12.60 12.50 13.50 

5.30 7.70 7.40 

10.60 9.30 9.40

4.30 4.33 6.04 

8.15 7.86 8.75

2.94 1.89 1.26 

.86 .38 .38 

.50 .55 .22

.26 .24 .25

.31 .39 1.62

98.49 98.34 99.42

49.60 

2.06 

13.00 

3.20 

10.60

5.86 

9.74

2.59 

.25 

.20

.21

.93

98.24

46.70 

1.95 

13.90 

4.40 

10.00

7.35 

11.10

2.67 

.34 

.19

.21

1.20

100.01

56.10 

1.93 

15.70 

3.50 

7.90

3.18 

5.26

2.69 

1.78 

.29

.19

.46

98.98

Trace-element abundances, in parts per million

Ba

Co

Cr

Hf

Nb

Ni

Rb

Sc

Sr

Ta

Th

V

Y

Zr

250

76

40

9.2

50

56

20

31.2

230

2.0

3.9

400

40

340

350 120 90

71 — 80

12 30 52

7.8 — 3.7

50 30 30

68 — 61

10 20 10

30.2 — 40.3

250 330 100

1.7 — .5

2.2 — 1.3

420 — 320

20 50 50

280 350 170

200

—

80

—

20

—

30

—

220

—

—

—

40

140

40

—

130

—

30

—

20

—

230

—

—

—

20

100

430

83

90

6.4

20

68

60

29.6

290

1.1

4.3

260

50

270

Rare earth element abundances, in parts per million

La

Ce

Nd

Sm

Eu

Tb

Yb

Lu

32.5

73

40

9.84

2.7

1.7

4.31

.61

28.7 — 5.8

65 — 14

37 — 10

9.0 — 2.88

3.37 — 1.11

1.3 — .70

3.52 — 3.08

.49 — .48

—

—

—

—

—

—

—

—

—

—

—

—

—

—

—

—

27.2

59

29

6.2

2.1

1.1

3.11

.45

Description of samples 

DUR-199 Metabasalt from DuPont Repauno Works well (appendix, well no. 85) 

MCP-228 Metabasalt from Mercer County Park well (appendix, well no. 27) 

DUR-206 Metabasalt from DuPont Repauno Works well (appendix, well no. 85) 

GAV-17 Metabasalt from Gaventa Farms well (appendix, well no. 88) 

DUR-185 Metabasalt from DuPont Repauno Works well (appendix, well no. 85) 

DUR-137 Metabasalt from DuPont Repauno Works well (appendix, well no. 85) 

DUR-246 Basaltic andesite from DuPont Repauno Works well (appendix, well no. 85)
CRYSTALLINE BASEMENT BENEATH THE NEW JERSEY COASTAL PLAIN AND CONTIGUOUS AREAS B19

Table 2. Chemical analyses of selected basement rocks— 

Continued

DUR-246A DUR-^05 AGD-6407

Major-oxide composition, in weight percent, and 

loss on ignition (LOT)

Si02

TiO2

A1203

Fe203

FeO

MgO

CaO

Na2O

K2O

P205

MnO

LOI

52.70

2.48

16.10

13.50*

—

3.82

4.99

2.62

2.42

.28

.18

.93

56.10

1.25

16.60

3.80

6.40

3.97

3.65

2.95

2.68

.26

.35

1.20

49.20

2.55

13.70

4.50

9.20

4.98

8.09

3.24

.62

.26

.22

1.62

Total 98.99 99.21 98.18

Trace-element abundances, in parts per million

Ba

Co

Cr

Hf

Nb

Ni

Rb

Sc

Sr

Ta

Th

V

Y

Zr

620

—

99

—

30

—

90

—

430

—

—

—

40

260

280

—

50

—

50

—

150

—

570

—

—

—

40

190

170

—

50

—

20

—

20

—

450

—

—

—

30

210

Rare earth element abundances, in parts per million

La — — —

Ce — — —

Nd — — —

Sm — — —

Eu — — —

Tb — — —

Yb — — —

Lu — — —

'Total Fe as FejOsDescription of samples

DUR-246A Basaltic andesite from DuPont Repauno Works well 

(appendix, well no. 85)

DUR-405 Basaltic andesite from DuPont Repauno Works well 

(appendix, well no. 85)

AGD-6407 Metagabbro from Anchor Gas-Dickinson well (appendix, well no. 104)

Figure 11. Type 2 dome-crescent-mushroom fold interference 

patterns in amphibolite from the DuPont Repauno Works well.

interference patterns (Ramsey and Huber, 1987); one such 

refolded fold in amphibolite is pictured in figure 11. This 

type of superimposed folding is common where recumbent 

fold nappes have been refolded by a fold phase having a 

steeply dipping axial surface (Ramsey and Huber, 1987). 

The U.S. Geological Survey Deptford well (appendix, 

well no. 83) penetrated medium-grained, decomposed schist 

composed of muscovite, biotite, quartz, and altered, chalky 

feldspar, with minor amounts of garnet and trace amounts of 

sulfide. The U.S. Geological Survey Clayton well (appendix, well no. 95) encountered similar schist containing biotite and abundant quartz, with sparse amounts of altered 

feldspar and trace amounts of garnet and sulfide.

SALEM COUNTY

Typically, the wells along the northwestern edge of 

Salem County encountered micaceous schist or schistose 

gneiss. The most complete description is from well no. 7 at 

the DuPont Carney Point Works (appendix, well no. 100)
B20 GEOLOGIC STUDIES IN NEW JERSEY AND EASTERN PENNSYLVANIA

that returned a decomposed, medium-fine- to mediumgrained gneiss composed of quartz, plagioclase, biotite, and 

chlorite, with minor amounts of muscovite (U.S. Geological 

Survey, 1967). It is of interest that none of the rocks of the 

Wilmington Complex as mapped by Woodruff and Thompson (1975) were observed in any of the wells immediately 

across the Delaware River in New Jersey. The aeromagnetic 

pattern of the Wilmington Complex seen in figure 9 suggests that it is confined mainly to Pennsylvania and Delaware. It may project into the extreme western end of Salem 

County; however, descriptions of basement are lacking from 

the Pennsville well (appendix, well no. 101).

HUDSON COUNTY

Extensive borings along the eastern edge of Hudson 

County for a variety of development projects (appendix, 

well nos. 105, 106, 107) disclosed serpentinite extending 

south to a point east of Jersey City and then schist from that 

point southward to the waterfront area east of Bayonne (fig. 

5). Serpentinite crops out immediately to the south of the 

waterfront on the northern end of Staten Island. The serpentinite east of Jersey City terminates abruptly, and plots of 

the available boring logs (R.A. Volkert, unpub. data) suggest that a series of northwest-trending normal faults cut the 

Stockton Formation and crystalline rocks west of the Hudson County waterfront (fig. 5). These faults step the Stockton Formation successively farther to the east as one goes 

south. Therefore, the serpentinite and Manhattan Schist 

contacts have been offset also, as has been the Cameron's 

Line fault, which is displaced to the east into the Hudson 

River (fig. 5).

DELAWARE

As in New Jersey, most wells penetrating subsurface 

basement in Delaware are concentrated along or near the 

Fall Line and were drilled to shallow depths. Most noteworthy of the Delaware wells are those drilled to the west and 

south of the southern half of Salem County, NJ. These 

include EC 14-07, Eb 23-22, Eb 44-08, and Gd 33-04 

(appendix, well nos. D5, D6, D8, and Dll, respectively). 

Wells EC 14-07 and Eb 23-22 both returned weathered cuttings of light-green chlorite schist composed of quartz, 

plagioclase, chlorite, and muscovite. Well Eb 44-08 (appendix, well no. D8) drilled a medium-grained, dark-grayish-green pyroxenite from a depth of 1,142 ft to the bottom 

of the hole at 1,159 ft (Dames and Moore, 1974). This rock 

is dominantly composed of clinopyroxene with minor 

amounts of amphibole and some alteration products. A well 

drilled approximately 1 mi to the northwest encountered 

saprolite composed of quartz and feldspar (Dames and 

Moore, 1974). Well EC 32-7 (appendix, well no. D7), 

drilled about 3.3 mi northeast of Eb 44-08, penetrated mica

schist. However, well EC 41-10 (appendix, well no. D9), 

drilled about 1.8 mi east-southeast of Eb 44-08, encountered saprolitic green clay. This may represent weathered 

rock developed on a continuation of the same pyroxenite 

body drilled at Eb 44-08. Well Gd 33-04 (appendix, well 

no. Dll) is the southernmost of the Delaware wells for 

which basement samples are available. The sample from 

this well at a depth of between 2,291 ft and 2,300 ft is 

weathered, fine-grained, light-green- to grayish-green 

schistose gneiss composed of chlorite, quartz, and plagioclase and a fine-grained, dark-green, quartz-poor rock 

largely altered to chlorite. These lithologies appear to have 

all of the aspects of a sequence of altered metavolcanic 

rocks. Their relation to the pyroxenite from well Eb 44-08 

is unknown since these wells are separated by a distance of 

approximately 7 mi and no other wells were drilled to basement between Gd 33-04 and Eb 44-08.

METAMORPHIC GRADE

Most of the aluminous basement rocks from the New 

Jersey subsurface examined during this study consist essentially of the mineral assemblage quartz+biotite+plagioclase 

with or without muscovite and garnet. Sillimanite, It-feldspar, tourmaline, staurolite, and graphite occur locally. The 

peak metamorphic grade of these rocks is within the sillimanite-almandine-muscovite subfacies of the amphibolite 

facies (Turner and Verhoogen, 1960). No evidence of granulite-facies metamorphism was seen in any of the New Jersey 

well samples.

Metamorphic isograds (contours showing metamorphic grade) were drawn for the subsurface pelitic and psammitic basement rocks in New Jersey and are shown in figure 

12. The highest metamorphic grade occurs in northern 

Gloucester and western Camden Counties as defined by the 

sillimanite isograd. Metamorphic grade decreases to the 

immediate north and south, with isograds displaying an 

apparent bilateral symmetry. Sillimanite-grade rocks are 

seen again in southern Monmouth County, but it is doubtful 

that this sillimanite isograd is continuous with the one in 

Gloucester and Camden Counties. It is interesting to note 

that the trend of the metamorphic isograds is crudely parallel to the Bouguer gravity contours and also to the aeromagnetic contours.

Most of the New Jersey well samples contain both 

muscovite and biotite, but saprolite from the Pennsauken 

SLF well (appendix, well no. 70) contains only muscovite, 

reflecting lower metamorphic grade (fig. 12). No kyanite, 

andalusite, or cordierite was observed in any of the well 

samples.
CRYSTALLINE BASEMENT BENEATH THE NEW JERSEY COASTAL PLAIN AND CONTIGUOUS AREAS B21

76° 75°

40°

39°

35

EXPLANATION

Well sample used to define isograd 

——— Isograd 

S Sillimanite 

G Garnet 

_ B Biotite 

M Muscovite 

? Metamorphic grade 

unknown

Huntingdon ValleyCameron 's Line thrust fault

16 32 MILES

II I

rn r i 0 16 32 KILOMETERS

Figure 12. Metamorphic isograds shown in the pre-Mesozoic crystalline basement of New Jersey.

GEOCHEMISTRY

Despite the similar mineralogy of the schist and schistose gneiss encountered beneath the New Jersey Coastal 

Plain, there is a marked difference in the chemistry of many 

of these rocks. Geochemical analyses were obtained on the 

freshest samples available to determine their protolith and 

to assign them to an appropriate tectonic setting. They were 

then able to be correlated with rocks originating in similar 

tectonic settings from terranes in areas adjacent to New Jersey. Major-oxide and trace-element contents of rocks sampled for this study are given in table 2.

METAPELITE AND METAGRAYWACKE

Wells from Gloucester County consistently returned 

pelitic and psammitic schists that fall within the field of 

mudrock and graywacke, respectively (fig. 13). The psammitic schists sampled typically contain 34 to 45 modal percent quartz and 65 to 77 weight percent SiC>2 and have K^O/
B22 GEOLOGIC STUDIES IN NEW JERSEY AND EASTERN PENNSYLVANIA

1.0

-5 0.9

I 0.8 

? 0.7

0.6

0.5

Subarkose

Lithic arenite ^-^

CL Graywacke

*DUR 

S&S «GAV

Mudrock DUR

10 c

0.2 0.4 0.6 0.8 

(Na + Ca)/ (Na + Ca + K) (mole percent)

1.0

Figure 13. Si/(Si+Al) versus (Na+Ca)/(Na+Ca+K) diagram of 

politic and psammitic schist from beneath the New Jersey Coastal 

Plain. Diagram from Carrels and McKenzie (1971). Sample abbreviations are CL, Chemical Leaman; IBP, Island Beach State Park; 

DUR, DuPont Repauno Works; GAV, Gaventa Farms; S&S, S&S 

Auction; and SH, Shoemaker Farm.

0.1

PM - 

(passive margin):

ARC 

E~ (ocean island arc margin)

ACM 

(active continental margin)

60 70 90

SiOFigure 14. K2O/Na2O versus SiO2 diagram of pelitic and psammitic schist from beneath the New Jersey Coastal Plain. Diagram 

from Roser and Korsch (1986). Sample abbreviations as in figure 

13.

Na2O ratios <1. These rocks correspond to the quartz- intermediate graywackes of Crook (1974) characteristic of tectonically mobile continental margins and are undoubtedly of 

marine origin.

Various attempts have been made to correlate the mineralogy and chemical composition of ancient sandstones 

with a particular tectonic setting (for example, Dickinson 

and Suczek, 1979; Bhatia, 1983; Roser and Korsch, 1986). 

Some of these discriminants were used with the Gloucester 

County schists. On a diagram of K2O/Na2O versus SiC>2 

(fig. 14), all psammitic and pelitic schists, except for the 

sample from the Gaventa Farms well, fall within the active 

continental margin field. The Gaventa Farms sample plots 

in the ocean island arc margin field but close to the active 

continental margin field. Although a variety of basin settings are included in the active continental margin field, 

sediments are chiefly derived from continental margin magmatic arcs or dissected magmatic island arcs (Roser and 

Korsch, 1986). Comparison of the quartz, plagioclase, and 

K-feldspar ratios for the psammitic schists on a ternary diagram after Dickinson and Suczek (1979) (not shown) also 

supports a model of sediment derivation from a transitional 

to dissected magmatic arc along a continental margin or 

island arc. By using the geochemical discriminants of 

Bhatia (1983) (Fe2O3+MgO, TiO2, Al2O3/SiO2, K2O/Na2O, 

and Al2O3/[CaO+Na2O]), psammitic schists from the 

Gaventa Farms, S&S Auction, and DuPont Repauno Works 

wells are classified as oceanic island arc sandstones. The 

Chemical Leaman sample, which has lower contents of 

Fe2O3+MgO and TiO2 and a lower A^OySiC^ ratio, is an 

active continental margin sandstone from an "Andean type 

setting." The high contents of plagioclase (29 to 41 modal

percent) and Na2O (2.3 to 4.4 wt. percent) in the Gloucester 

County psammitic schists support the interpretation that 

they were receiving abundant volcanic detritus from a magmatic arc source.

METABASALT

As discussed above, Gloucester County pelitic and 

psammitic schists are intercalated with amphibolite, and at 

the DuPont Repauno Works well, with mafic schist that is 

meta-andesite. On the basis of major- and trace-element 

compositions, all amphibolites are metabasalt and form two 

distinct geochemical groups, referred to as type 1 and type 

2. Amphibolite from the Gaventa Farms well is very similar 

geochemically to some amphibolite from the DuPont Repauno Works well (table 2), and together they define type 1 

basalts. Compared to type 2 basalts, they are characterized 

by higher contents of MgO (5.86-7.35 percent), CaO (8.75- 

11.10 percent), and Cr (52-130 ppm) and lower contents of 

TiO2 (1.63-2.06 percent), P2O5 (0.19-0.22 percent), and Zr 

(100-170 ppm).

Type 1 basalts have compositions that are similar to 

those of moderately fractionated tholeiitic basalt and show 

typical tholeiitic Fe enrichment on an AFM diagram (fig. 

15). They are hypersthene normative, but the Gaventa 

Farms well sample contains normative olivine, whereas the 

DuPont Repauno Works well samples contain normative 

quartz. They all have relatively low Mg1 values (100(Mg/ 

[Mg+Fe2+]) atomic), ranging from 49.6 to 56.7, together 

with generally low Cr and Ni contents. On the basis of one 

analysis (GAV-17), total concentrations of rare earth elements (REE's) are low, and these rocks have (La/Yb)N of
CRYSTALLINE BASEMENT BENEATH THE NEW JERSEY COASTAL PLAIN AND CONTIGUOUS AREAS

100

50

B23

ALK MGO

Figure 15. Plot of metabasalt and meta-andesite from beneath 

the New Jersey Coastal Plain on an AFM diagram. Dividing line 

shows the boundary of Irvine and Baragar (1971) between tholeiitic (T) and calc-alkaline (CA) rocks. Solid circle, type 1 basalt; 

open circle, type 2 basalt; triangle, meta-andesite.

1.26. Compared with chondritic values, La is enriched 

17.7x and Yb 14x. Type 1 basalt displays a relatively flat, 

slightly light-REE enriched pattern (fig. 16) with a small 

negative Eu anomaly. The REE pattern is similar to REE 

patterns of marginal basin basalts and also island arc 

basalts. Basalts from these two settings differ in their chondrite-normalized concentrations of Ba. Island arc basalts 

have Ba^ equal to or enriched relative to LaN, while marginal basin basalts are depleted in Ba^ (Basaltic Volcanism 

Study Project, 1981). Type 1 basalt has BaN ranging from 

5.8 to 13, clearly depleted relative to LaN, and therefore 

more like that of marginal basin basalts.

Various discrimination diagrams involving immobile 

elements were used to correlate type 1 basalts with a specific tectonic setting. These samples fall dominantly in the 

field of midocean ridge basalt (MORB) on diagrams of Zr/ 

Y versus Zr (fig. 17) and Nb-Zr-Y (fig. 18), as well as a 

number of other diagrams (not shown), but also over- lap 

into the within-plate field. However, the chemistry of type 1 

basalts is less like the chemistry of normal MORB 

(N-MORB) and more closely resembles that of enriched 

MORB (E-MORB). Type 1 basalts have higher overall concentrations of incompatible elements compared to 

N-MORB and ratios of (La/Sm)N (1.25), Th/Hf (0.35), Zr/ 

Nb (3.33-7), Ta/Yb (0.16), Zr/Y (3.4), Hf/Ta (7.4), and Ti/ 

Zr (104) are more consistent with the composition of 

E-MORB (Sun and others, 1979; Wood and others, 1979, 

1981; Wilson, 1989).

On a MORB-normalized incompatible-element diagram (fig. 19), type 1 basalt (GAV-17) has a pattern that, 

except for P and Ti, is variably enriched in the more incompatible elements. This pattern is unlike that of N-MORB or

o 10

La Ce Nd Sm Eu Tb Yb Lu

Figure 16. Chondrite-normalized rare earth element patterns for 

New Jersey metabasalt and meta-andesite. Normalization values 

from Shimizu and Masuda (1986). Sample numbers as in table 2. 

MCP, Mercer County Park well sample. Other sample abbreviations as in figure 13.

5

^ 2

DUR-199 

'AGD-6407 DUR?206/

A DUR-246A 

DUR-137 DUR-246*/

DUR-405'

ARC

OFB

10 20 50 100

Zr, IN PARTS PER MILLION

200 500

Figure 17. Plot of Zr/Y versus Zr for mafic rocks from beneath 

the New Jersey Coastal Plain. Fields are WPB, within-plate basalt; 

OFB, ocean floor basalt; and ARC, island arc basalt. Diagram 

from Pearce and Norry (1979). AGO, Anchor Gas-Dickinson well 

sample. Other sample abbreviations as in figure 13. Open square, 

metagabbro. Other symbols as in figure 15.

that of island arc basalts. The latter are typically depleted in 

the elements Th to Yb and enriched in Sr to Ba (Pearce, 

1983) and have a much flatter pattern from Th to Yb with 

normalized values <1. Wood and others (1979, 1981) 

pointed out that island arc basalts are enriched in Cs, Rb, 

Ba, Th, U, La, and Sr relative to N-MORB. Type 1 basalts 

have generally low concentrations of these elements. Furthermore, island arc basalts display a distinct Ta-Nb trough 

(Pearce, 1983), whereas type 1 basalts are enriched in TaNb and display a peak in this part of the pattern. On figure
B24 GEOLOGIC STUDIES IN NEW JERSEY AND EASTERN PENNSYLVANIA

2Mb

MCP-228

/ /^DUR-40 

DUR-199

/ / DUR-246A 

/ /A / DUR-185 

AC^D-6407

DUR-206/ A \P-MORB 

UR-24

Figure 18. Plot of mafic rocks from beneath the New Jersey 

Coastal Plain on a Nb-Zr-Y ternary diagram from Meschede 

(1986). Fields are WPA, within-plate alkalic; WPT, within-plate 

tholeiitic; VAB, volcanic arc basalt; N-(normal) MORE; and 

P-(enriched plume) MORB. Symbols and sample abbreviations as 

in figure 17.

Figure 19. MORB-normalized incompatible-element diagram 

for metabasalt and meta-andesite. Normalization values from 

Pearce (1983). Sample abbreviations as in figure 17.

19, type 1 basalt displays some characteristics typical of 

N-MORB, but enrichment of high-field-strength elements 

superimposed on the pattern is responsible for its atypical 

appearance.

Type 1 basalts have a Ti/V ratio of 33 that overlaps the 

fields of MORB and back-arc basin basalts on the Ti versus 

V diagram of Shervais (1982) (not shown). Island arc 

basalts typically have Ti/V ratios of <20 (Shervais, 1982).

Scandium contents of 40 ppm for type 1 basalts and La/Nb 

ratios of 0.19 are also more consistent with the composition 

of MORB than of island arc basalt. Therefore, the geochemical evidence appears to preclude an island arc origin for 

type 1 basalts. They seemingly have a MORB affinity but 

are more fractionated and closer in composition to 

E-MORB. Wood and others (1979) stated that E-MORB can 

be distinguished from ocean island basalt and off axis 

(within plate) basalt in that the latter have ratios of Hf/Ta <2 

and Zr/Y >4.5. Type 1 basalt has Hf/Ta of 7.4 and Zr/Y of 

3.4, further supporting its MORB affinity. The MORB-like 

composition of type 1 rocks suggests that the magma that 

produced these basalts tapped a similar shallow mantle 

source and underwent considerable fractionation of mafic 

minerals plus plagioclase prior to emplacement.

Type 1 basalts are chemically dissimilar to Eastern 

North American basalt and diabase of Jurassic age in the 

Newark basin. They are also chemically dissimilar to 

basalts in the Cambrian Chopawamsic Formation or 

amphibolites of the Ta River Metamorphic Suite in Virginia 

described by Pavlides (1981) or to basalts in the Cambrian 

James Run Formation (Gilpins Falls Member) in Maryland 

described by Higgins and Conant (1990). Type 1 basalts are 

higher in TiO2 , P2O5 , FeO1, Zr, Hf, and Th and lower in 

CaO, Sc, Ni, and Cr than metabasalt in the James Run Formation. On a diagram of TiO2 versus Zr/P2O5 (fig. 20), type 

1 basalts plot away from the fields defined by basalts of the 

Chopawamsic, Ta River, and James Run. The REE pattern 

of type 1 basalts is also dissimilar to those of the occurrences just mentioned. However, type 1 basalts have majorand trace-element compositions and REE abundances very 

similar to those of basaltic rocks of Late Proterozoic to early 

Paleozoic age (Hancock Member of the Pinney Hollow Formation) (Coish and others, 1985) and early Paleozoic age 

(Stowe Formation) (Coish and others, 1986) in Vermont. On 

figure 20, they partially overlap, or fall close to, the field of 

type 1 basalts.

Type 2 basalts are defined by samples from the DuPont 

Repauno Works well and from the Mercer County Park 

well. As shown above, these rocks are typically lower in 

MgO (4.33^.78 percent), CaO (7.85-8.15 percent), and Cr 

(10-50 ppm) and higher in TiO2 (3.67-3.77 percent), 

P2O5 (0.50-0.55 percent), and Zr (280-350 ppm) than type 

1 basalts. They contain slightly lower abundances of transition metals than type 1 basalts. Type 2 basalts have compositions that are hypersthene normative and similar to those 

of fractionated tholeiitic basalt. They show typical tholeiitic 

Fe enrichment on an AFM diagram (fig. 15) at slightly 

higher Fe contents than type 1 basalt. Type 2 basalts have Y/ 

Nb ratios of 0.6-1.67, reflecting their overlap toward transitional and even slightly alkalic composition. They have relatively low Mg' values of 44-46.5, which suggests that they 

are more fractionated than type 1 rocks, and generally low 

contents of Cr and Ni. On MgO variation diagrams (fig. 21), 

type 2 basalts consistently fall along the same fractionation
CRYSTALLINE BASEMENT BENEATH THE NEW JERSEY COASTAL PLAIN AND CONTIGUOUS AREAS B25

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0.05 0.10

EXPLANATION

0.15 0.20

Chopawamsic Formation (Pavlides,

1981) 

James Run Formation (Gilpins Falls

Member) (Higgins and Conant, 1990) 

Ta River amphibolite (Pavlides, 1981) 

Stowe Formation (Coish and others,

198S. 1986) 

Hancock greenstone (Coish and others,

198S, 1986)

Catoctin greenstone in Virginia (Reed 

and Morgan, 1971)

Diabase dikes and amphibolite from 

West Chester Prong and Avondale 

anticline (Espenshade, 1986)and 

amphibolite east of Wilmington 

complex (M.E. Wagner, unpub. data)

New Jersey Highlands diabase dikes 

(Volkert and Puffer, 1995)

Figure 20. Plot of mafic rocks from the New Jersey subsurface 

(indicated by symbols and sample abbreviations) compared with 

mafic rocks from the north-central and northern Appalachians on a 

diagram of TiO2 versus Zr^Os- Dividing line is between alkalic 

(A) and tholeiitic (T) rocks. Diagram from Winchester and Floyd 

(1976). Symbols and sample abbreviations as in figure 17.

trend as type 1 basalts, suggesting that the two types are petrogenetically related.

Total concentrations of REE's are higher in type 2 

basalts than in type 1; the former have (La/Yb)N of 5.06. 

Lanthanum is enriched 89-101x relative to chondrite in 

type 2 basalts, reflecting their more fractionated composition. The REE patterns (fig. 16) of type 2 basalts are similar 

to each other, although the DuPont Repauno Works well 

sample has slightly higher total REE abundances. Similar 

REE patterns are seen in basalts from continental and 

oceanic, within-plate tectonic settings (Basaltic Volcanism 

Study Project, 1981; Wilson, 1989).

Type -2 basalts fall consistently in the within-plate field 

on diagrams of Zr/Y versus Zr (fig. 17) and Nb-Zr-Y (fig. 

18), as well as numerous other diagrams (not shown). A 

within-plate setting is further supported by incompatibleelement ratios of Zr/Nb (5.6-11.7), Hf/Ta (4.6), Zr/Y (7-14) 

(Wood and others, 1979), and La/Nb (0.6-0.8) (Basaltic 

Volcanism Study Project, 1981). On a diagram of Th/Yb 

versus Ta/Yb (fig. 22), type 2 basalts cluster in the field of

enriched, within-plate basalts. There is no geochemical evidence suggesting they have experienced much crustal contamination or enrichment by subduction zone fluids, which, 

according to Pearce (1983), would enrich them in Th.

On a MORB-normalized incompatible-element diagram (fig. 19), type 2 basalts have similar overall patterns 

that nearly overlap from Ta to Yb. The "humped" shape of 

their pattern is characteristic of basalts from within-plate 

settings (Pearce, 1983). Type 2 basalts have higher overall 

concentrations of incompatible elements than type 1 but 

have similar enrichments and depletions. The type 1 pattern 

of GAV-17, therefore, mimics the type 2 patterns, especially from Nb to Ti. The greater amount of fractionation of 

type 2 basalts probably is a result of their derivation from a 

deeper mantle source region and (or) lower amounts of partial melting prior to emplacement than type 1 rocks.

Type 2 basalts have Ti/V ratios of 52.4-56.5 that are 

slightly higher than ratios in type 1 rocks and plot in the 

field of continental and oceanic tholeiitic to alkalic basalts 

on the Ti versus V diagram of Shervais (1982). Tholeiitic 

basalts have Ti/V ratios of 30-50, and transitional to alkalic 

basalts, 35-70 (Shervais, 1982). By this criterion, type 2 

rocks are transitional to alkalic. This interpretation is consistent with their Y/Nb ratios.

Type 2 basalts have major- and trace-element compositions and REE abundances that, like those of type 1 rocks, 

are dissimilar to those of Eastern North American Jurassic 

basalt and diabase and also to those of metabasalts of the 

Chopawamisic, Ta River, and James Run. However, type 2 

chemistry is very similar to that of high-TiO2 amphibolites 

in the "Wissahickon" Formation east of the Wilmington 

Complex (M.E. Wagner, unpub. data), and also to that of 

metabasalt of Late Proterozoic to early Paleozoic age in the 

Underbill Formation as used by Coish and others (1985), 

and the early Paleozoic Stowe Formation (Coish and others, 

1986) in Vermont and Late Proterozoic or Early Cambrian 

metabasalt in the Nassau Formation in eastern New York 

and western Massachusetts (Ratcliffe, 1987a). It also has 

major- and trace-element abundances nearly identical to 

those of metabasalt of the Late Proterozoic Catoctin Formation in Virginia (Reed and Morgan, 1971; Espenshade, 

1986) and Pennsylvania (Smith and others, 1991) and to 

those of Late Proterozoic diabase dikes in the southern Blue 

Ridge (Goldberg and others, 1986), New Jersey Highlands 

(Puffer and others, 1991; Volkert and Puffer, 1995), and the 

New York Hudson Highlands (Ratcliffe, 1987b). On figure 

20, type 2 basalt overlaps or plots close to these other occurrences.

META-ANDESITE

Spatially associated with type 2 basalt in the DuPont 

Repauno Works well is metamorphosed andesite having the 

composition of basaltic andesite. These rocks contain 52.7 

to 56.1 percent SiO2- They are consistently hypersthene normative, contain normative quartz, and are dominantly
B26 GEOLOGIC STUDIES IN NEW JERSEY AND EASTERN PENNSYLVANIA

55 

53

Q 5, 

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Figure 21. MgO variation diagrams of major and selected trace elements for mafic rocks from beneath the New Jersey Coastal Plain. 

Major elements in weight percent; trace elements in parts per million. Symbols as in figure 17.
10

1.0

0.1

0.01

CRYSTALLINE BASEMENT BENEATH THE NEW JERSEY COASTAL PLAIN AND CONTIGUOUS AREAS

10

B27

Continental margin arc

Oceanic arc

0.01 0.1

Ta/Yb

1.0 10

Figure 22. Th/Yb versus Ta/Yb diagram for metabasalt and 

meta-andesite. MORB, midocean ridge basalt; WPB, within-plate 

basalt. Diagram modified from Pearce (1982, 1983).

o

d

DUR-199O

MCP-228

O

DUR-246

GAV-17

10

Sm, IN PARTS PER MILLION

Figure 23. Hf versus Sm diagram for metabasalt and metaandesite. Symbols and sample abbreviations as in figure 17.

tholeiitic in composition, although Y/Nb ratios of 0.8 to 2.5 

suggest that they range to slightly alkalic. They show typical tholeiitic Fe enrichment on an AFM diagram (fig. 15) 

with exception of sample 405, which contains less Fe and 

falls within the calc-alkaline field. The three meta-andesites 

sampled for this study contain 15.7 to 16.6 percent A^Os 

and 1.78 to 2.68 percent F^O. Compared to type 2 basalts, 

they are lower in MgO, CaO, FeO1 , and P2Os. However, 

they have TiO2 contents, trace-element abundances, and 

Mg' values (41.8-52.5) that overlap those of both type 1 and 

type 2 basalts. Concentrations of Cr are somewhat higher 

(50-99 ppm) than in type 2 samples, as are the other transition metals, and similar to abundances in type 1 rocks.

Meta-andesites sampled have relatively high total REE 

concentrations (La/YbN=6.33) and are light-REE enriched 

with La=84.5x chondrite. The REE pattern (fig. 16) is similar to that of type 2 basalts. The same is seen on a 

MORB-normalized incompatible-element diagram (fig. 19), 

with data for meta-andesite and type 2 basalts display- ing 

similar "humped" patterns and incompatible-element 

enrichments. However, meta-andesite is further enriched in 

K, Rb, Ba, and Th. Pearce (1983) has proposed that enrichment in these elements, superimposed on a within-plate pattern, may indicate a contribution from a subduction zone 

component. It may also be attributable to the effects of 

crustal contamination. However, this seems less likely given 

the close spatial association with type 2 basalts, which show 

little evidence of contamination. Enrichment in K, Rb, and 

Ba may also be the result of low-pressure fractionation as 

proposed by Dostal and others (1982). We favor this as the

cause for the enrichment in basaltic andesites for reasons 

discussed below.

By use of selected major- and trace-element abundances and trace-element-ratio discriminants of Bailey 

(1981), meta-andesite from the DuPont Repauno Works 

well has characteristics of both orogenic and non-orogenic 

andesite. On the basis of Th versus La/Yb and Sc/Ni versus 

La/Yb diagrams, which Bailey (1981) stated are the most 

sensitive for discriminating tectonic settings, meta-andesite 

falls consistently in the continental margin arc field. These 

rocks similarly plot in the continental margin arc field on a 

diagram of Th/Yb versus Ta/Yb (fig. 22). On diagrams of 

Zr/Y versus Zr (fig. 17) and Nb-Zr-Y (fig. 18) and other 

diagrams not shown, meta-andesite plots consistently in the 

within-plate field.

Several lines of evidence suggest a possible petrogenetic relation between meta-andesite and type 2 basalt. 

These include (1) their overlapping spatial and temporal 

association in the DuPont Repauno Works well, (2) similar 

REE and incompatible-element concentrations, (3) other 

trace-element similarities, and (4) consistent plot in withinplate tectonic setting on various discrimination diagrams. 

On diagrams of Hf versus Sm (fig. 23) and La/Sm versus 

La/Yb (fig. 24), meta-andesite falls along the same trend as 

types 1 and 2 basalt. The correlation of all three rock types 

on these diagrams is noteworthy and seems to imply a petrogenetic relation. On figure 23, these rocks define a linear 

progression from olivine tholeiite to quartz tholeiite to transitional alkalic to alkalic. However, meta-andesite does not 

consistently fall along the same fractionation trend as types
B28 GEOLOGIC STUDIES IN NEW JERSEY AND EASTERN PENNSYLVANIA

I

DUR-246

A

DUR-199

o

o

MCP-228

GAV-17

La/Yb

10

Figure 24. La/Sm versus La/Yb diagram for metabasalt and meta-andesite. Symbols and sample abbreviations as in figure 17.

1 and 2 basalt on MgO variation diagrams (fig. 21). Nor 

does it lie along the trend of the metabasalts on a Th versus 

Hf diagram (not shown). Ratios of Hf/Th for the two basalt 

types overlap and range from 2.36 to 3.77, whereas 

meta-andesite has a much lower Hf/Th ratio of 1.49. Nevertheless, the evidence suggests that basaltic andesite and type

2 basalt are related. We interpret the former to have been 

derived principally through fractional crystallization from 

type 2 basalt prior to emplacement. Fractionation mainly 

involved olivine, clinopyroxene, and, to a lesser extent, plagioclase. This is supported by the low Mg' values, low CaO/ 

A^OS ratios, low Sc contents, inverse correlation of Sr with 

MgO (fig. 21), and small Eu anomalies (fig. 16) present in 

both rock types. This interpretation is further supported by 

the experimental work of Ring wood (1977) who reported

that basaltic andesite may be produced through fractionation from a parental basalt; the resulting rock will be 

enriched in light rare earth elements and depleted in heavy 

rare earth elements.

METAGABBRO

Fine-grained metagabbro from the Anchor Gas Dickinson well is somewhat similar geochemically to type 2 

basalts but differs in having lower contents of FeO1 (12.33 

percent), Nb (20 ppm), and Zr (210 ppm) and higher contents of Na2O (3.24 percent) and Sr (450 ppm). This rock is 

hypersthene normative and contains normative quartz but 

substantially less than type 2 basalt and meta-andesite. Metagabbro is distinctly tholeiitic in composition and has Y/Nb 

of 1.5. It has a relatively low Mg' of 49.4 and low Cr content 

(50 ppm). A complete suite of trace elements and REE's 

could not be obtained on this sample. However, sufficient 

elements were obtained to construct a partial pattern on a 

MORB-normalized incompatible-element diagram (fig. 19). 

The metagabbro data clearly display an enriched pattern 

with a "humped" shape roughly similar to and intermediate 

between the shapes of data for type 1 and type 2 basalts. 

Incompatible-element abundances are closer to those of 

type 2 from Sr to Ba but closer to those of type 1 from P to 

Yb.

With the exception of SiC>2, CaO, K^O, and Cr contents, metagabbro data fall outside of the fractionation trend 

defined by type 1 and 2 basalts on MgO variation diagrams 

(fig. 21). The same is seen on a diagram of TiO2 versus Zr/ 

P2O5(fig. 20), with metagabbro plotting away from the 

fields of either type 1 or type 2 basalt. On diagrams of Zr/Y 

versus Zr (fig. 17) and Nb-Zr-Y (fig. 18), metagabbro consistently falls in the within-plate field. It straddles the fields 

of within-plate and volcanic arc basalts on a diagram of Y 

versus Cr (not shown). We think that the geochemical differences between metagabbro and types 1 and 2 basalt are 

sufficient to preclude a petrogenetic relation. Metagabbro 

from the Anchor Gas Dickinson well is a moderately fractionated tholeiite with an affinity toward a within-plate tectonic setting. Whether this setting was continental or 

oceanic is impossible to say at this time.

METAGRAYWACKE AT ISLAND BEACH 

STATE PARK

Schistose gneiss from the U.S. Geological Survey 

Island Beach State Park well falls within the field of 

graywacke on figure 13. This sample contains about 30 percent modal quartz and 68 weight percent SiO2 and has a 

K2O/Na2O ratio <1, values that correspond to the quartzintermediate graywacke of Crook (1974). It falls within the 

active continental margin field on a diagram of K2O/Na2O 

versus SiO2 (fig. 14). In these respects, the chemistry of this
CRYSTALLINE BASEMENT BENEATH THE NEW JERSEY COASTAL PLAIN AND CONTIGUOUS AREAS B29

rock is similar to that of psammitic schist from the wells in 

Gloucester County. However, a comparison of the geochemical discriminants of Bhatia (1983) shows that the 

Island Beach State Park well sample has somewhat lower 

Fe2O3+MgO and TiC>2 contents and a slightly higher A^O^/ 

(CaO+Na2O) ratio than the Gloucester County samples. It is 

also lower in Cr and slightly higher in Nb. Therefore, it is 

classified as a continental island arc sandstone. Sediments 

in this type of setting are deposited in basins adjacent to 

island arcs developed on continental crust or on thin continental margins (Bhatia, 1983). The high contents of modal 

plagioclase (40 percent) and Na2O (3.51 weight percent) 

suggest that the Island Beach State Park sample was receiving felsic volcanic/plutonic detritus from a magmatic 

source. A similar interpretation was discussed above for the 

Gloucester County metagray wacke.

DISCUSSION

Correlating the subsurface pre-Mesozoic crystalline 

basement rocks in New Jersey with outcropping rocks in 

adjacent States and in distant terranes is hindered by the 

overall structural complexity of the exposed rocks, as well 

as by the limited amount of subsurface data available for 

New Jersey. However, it is logical to assume that subsurface crystalline rocks in New Jersey are a continuation of 

the complex structures of the exposed Piedmont of adjacent 

States and therefore represent a composite of different lithotectonic units contained in a series of stacked thrust sheets. 

The following interpretations are based largely on drillhole, geochemical, and potential field geophysical data.

No intrusive rocks, nor any of the layered, two-pyroxene gneisses of the Wilmington Complex, were observed in 

any of the well samples studied. Rocks of the Wilmington 

terrane appear to be largely confined to southeastern Pennsylvania and northern Delaware and extend into New Jersey 

only along the western tip of Salem County (Volkert and 

Drake, 1991). The gravity data (fig. 8) and aeromagnetic 

data (fig. 9) also support this interpretation.

All of the amphibolite-facies pelitic and psammitic 

schist and schistose gneiss occurring along the Fall Line 

and extending at least to the western edge of Monmouth 

County probably are equivalent to the "Wissahickon" Formation, which is included in the Potomac terrane of Horton 

and others (1989) and the Philadelphia terrane of Faill and 

MacLachlan (1989) in Pennsylvania. Volkert and Drake 

(1991) interpreted these rocks to be equivalent also to the 

western part of the Brompton-Cameron terrane of Zen and 

others (1989) in New England (fig. 7). Rankin (1994) suggested that the correlation of the Potomac terrane with the 

Brompton-Cameron terrane is incorrect because the Brompton-Cameron terrane lacks the pre-Taconic deformation 

characteristic of the Potomac terrane. A boundary between 

these terranes is probably present in the subsurface. In New

Jersey, these pelitic and psammitic rocks represent a 

sequence of "eugeoclinal" sediments deposited in a slope 

and basin setting. Alternating shale and gray wacke layers of 

varying thickness recovered from drill holes in Gloucester 

County probably are turbidite deposits. A similar interpretation has been suggested for high-grade rocks like the "Wissahickon" in the Potomac terrane in Maryland and 

Pennsylvania (Drake and others, 1989; Muller and others, 

1989; Crawford, 1991). The basin in which these sediments 

were deposited must have been situated east of the North 

American continental margin. We interpret this basin as 

having been a marginal, perhaps back arc, basin, as did 

Crawford and Mark (1982) and Pavlides (1989).

The occurrence of type 1 basaltic rocks having a 

MORB-like chemistry with marine sediments points to the 

likelihood that a small spreading center existed within the 

basin. The areal extent and thickness of type 1 basalts in 

New Jersey are unknown due to the paucity of basement 

samples from outside of Gloucester County. However, similar low- to intermediate-TiO2 basalts having MORB and 

island arc affinities are known west of the Wilmington 

Complex in southeastern Pennsylvania (M.E. Wagner, 

unpub. data) within schist and schistose gneiss similar to the 

"Wissahickon." Closely associated with pelitic and psammitic schist and also type 1 basalt is type 2 basalt. Basaltic 

rocks that are chemically identical to type 2 rocks are 

known from artificial exposures and from drill holes in the 

Trenton prong in New Jersey (Volkert and Drake, 1993; 

R.A. Volkert, unpub. data). Some of these basalts may be 

dikes and some sills. We interpret these high-TiC^ and 

incompatible-element-enriched basalts to be correlative 

with Late Proterozoic diabase dikes that intrude Middle 

Proterozoic rocks in the New Jersey Highlands (Puffer and 

others, 1991; Volkert and Puffer, 1995) and other Late Proterozoic metabasalt from throughout the Appalachians. In 

this regard, they record tholeiitic and minor alkalic magmatism generated during crustal extension related to lapetan 

rifting. If this correlation is correct, then the ages of the pelitic and psammitic schist protoliths in this basin range from 

Late Proterozoic to early Paleozoic. Similar age estimates 

were advanced by Drake (1985, 1986) for Potomac terrane 

rocks in Virginia, by Higgins (1972) and Muller and Chapin 

(1984) for rocks in Maryland, and by Crawford (1991) for 

rocks in southeastern Pennsylvania.

The close spatial and temporal association of type 1 

and 2 basalt and meta-andesite within the same sediment 

package is intriguing. The association of transitional to 

alkalic basalts with tholeiitic MORB basalts is not uncommon and is known from modern ocean ridge settings (for 

example, Shibata and others, 1979). The more fractionated 

type 2 basalts probably were generated from a deeper mantle source through small amounts of partial melting. Less 

fractionated type 1 basalt (E-MORB) may have originated 

from a shallower mantle source that had undergone greater 

amounts of partial melting than type 2 source rocks. These
B30 GEOLOGIC STUDIES IN NEW JERSEY AND EASTERN PENNSYLVANIA

two basalt types possibly intruded the spreading center 

along a "leaky" transform fault or at some location along 

the flank of the ridge. Less enriched type 1 basalt is more 

typical of MORE erupted in a back arc basin setting. 

Whether the more fractionated type 1 basalt is similar 

MORE that underwent mixing with type 2 magma or is 

from a different, more enriched source region is difficult to 

say at this time. As discussed above, type 2 basalt likely was 

a parental magma to meta-andesite. We interpret meta-andesite to have been derived from type 2 basalt principally 

through fractionation involving olivine, clinopyroxene, and, 

to a lesser extent, plagioclase. Conformable contacts 

between meta-andesite and pelitic schist suggest that the 

former may have intruded as sills. Type 2 basalts may have 

intruded as dikes and (or) sills; contact relations are not 

clearly known. The major- and trace-element compositions 

of type 2 basalt and basaltic andesite suggest that they are 

mantle derived. Any model relating their magmatism to a 

subduction zone setting seems unlikely, as their emplacement was clearly in an extensional tectonic setting and unrelated to subduction. No evidence of associated rocks of 

dacitic or rhyolitic composition was seen within rocks of 

this marginal basin. Petrogenetic conditions apparently prevented magma intruding the basin from fractionating further 

to produce rocks of a more evolved composition. Perhaps 

these conditions were due to the presence of a relatively thin 

crust in this part of the Appalachians at this time.

Sedimentary melange deposits were recognized and 

mapped in the Potomac terrane in Virginia (Drake, 1985) 

and Maryland (Muller and others, 1989; Higgins and Conant, 1990). However, no such rock was encountered in any 

of the drill holes from the Potomac terrane in New Jersey. 

While noteworthy, this lack of data may have little meaning 

bcause basement wells are much less abundant immediately 

southeast of the inner Coastal Plain.

Recognition of possible nappe-stage folds in psammitic schist and amphibolite from Gloucester County is significant in documenting the possible presence of nappe 

structures in New Jersey involving rocks of the Potomac 

terrane. Similar structural interpretations have been proposed for Grenville-age basement cored "domes" in Maryland (Muller and Chapin, 1984) and also in Pennsylvania 

(Wagner and Srogi, 1987). It is generally accepted that 

emplacement of these nappes and northwestward-directed 

transport of Potomac terrane rocks along thrust faults over 

rocks of the North American craton and its cover rocks 

occurred in the Ordovician during the Taconic orogeny.

Lack of drill-hole data leads to uncertainty whether 

rocks of the James Run Formation (Chopawamsic terrane) 

extend into New Jersey. Such rocks, if present, should be 

outboard of the Potomac terrane. However, interpreted 

Potomac terrane rocks in New Jersey occur farther southeast than exposed occurrences of the James Run in northeastern Maryland and northern Delaware (fig. 25). 

Therefore, the James Run would have to trend southeast

through northern Delaware and then into central Salem 

County, N.J. Geologic mapping in northeastern Maryland 

(Higgins and Conant, 1990) shows that many of the units do 

have a east-southeast trend. To an extent, the aeromagnetic 

contours are also east-southeast-trending through northern 

Delaware (fig. 9). Insufficient information exists to interpret 

whether this structural divergence is related to possible displacement along north-trending faults, or to arcing of the 

regional structural grain in a trend that is subparallel to the 

Salisbury embayment. Regardless, it is possible that the 

James Run extends into New Jersey. Unfortunately, reliable 

sample descriptions are lacking from the only well in central Salem County for which information is available 

(appendix, well no. 102).

Although Volkert and Drake (1991) initially correlated 

metabasalt and meta-andesite in some Gloucester County 

wells with similar rocks in the Chopawamsic terrane, it is 

now clear from the geochemistry that these rocks are not the 

same as the Chopawamsic Formation or the James Run Formation and instead are part of the Potomac terrane. Wagner 

and Srogi (1987) suggested that the Wilmington Complex 

represents the root of a volcanic arc, and Pavlides (1989) 

proposed that the Wilmington Complex may be the northeastern extent of a volcanic arc represented by the Chopawamsic and James Run volcanic arc. We tentatively 

extend the James Run into central Salem County (fig. 25), 

but we recognize that it could also taper and end, along with 

the base of the arc, in northern Delaware. Our reason for 

extending this terrane is largely influenced by the chemistry 

of the pelitic and psammitic rocks from the inner Coastal 

Plain. Their highly sodic composition suggests a magmatic 

arc source that shed abundant volcanic detritus into the 

basin. The lack of K-feldspar in these rocks precludes an 

uplifted continental block (either part of the North American craton or a separate fragment thereof) as a sediment 

source.

Pyroxenite encountered in well Eb 44-08 in Delaware 

(appendix, well no. D8) may be correlative with pyroxenite 

in the Bel Air-Rising Sun terrane (Baltimore Complex) in 

northeastern Maryland. However, the pyroxenite in well Eb 

44-08 is more than 15 mi southeast of the exposed James 

Run Formation in Maryland, whereas the main block of the 

Bel Air-Rising Sun terrane is northwest of the exposed 

James Run. Gabbro and serpentinite are exposed south of 

the exposed James Run in northeastern Maryland (Higgins 

and Conant, 1990). Similar gabbro at Iron Hill and serpentinite, which was returned in nearby wells, occur north of 

the pyroxenite in northern Delaware. Higgins and Conant 

(1990) tentatively correlated these rocks with metagabbro at 

Aberdeen, Md. Horton and others (1989) referred to this as 

the Aberdeen block and interpreted it to be part of the Bel 

Air-Rising Sun terrane, which was structurally emplaced 

onto the James Run Formation. Pyroxenite in well Eb 44-08 

is surrounded to the immediate north by wells returning a 

diversity of lithologies; these include chlorite schist, biotite
CRYSTALLINE BASEMENT BENEATH THE NEW JERSEY COASTAL PLAIN AND CONTIGUOUS AREAS B31

TERRANE 

NO.AMERICAN CRATON

2 POTOMAC

3 BROMPTON-CAMERON

4 MONMOUTH 

MT. HOLLY

6 WILMINGTON

7 CHOPAWAMSIC

8 ROANOKE RAPIDS

9 MESOZOIC BASIN

(Shaded where buried) 

10 CAPE MAY

Bouguer gravity contour 

Contour interval 5 milligals

Figure 25. Speculative assignment of pre-Cretaceous basement rock in New Jersey to central and northern Appalachian 

terranes. Terranes are superimposed on Bouguer gravity anomaly map of New Jersey modified from Bonini (1965). Location of inferred, buried Mesozoic basin from Sheridan and others (1991); inferred Mesozoic basin in Delaware from Benson 

(1992).
B32 GEOLOGIC STUDIES IN NEW JERSEY AND EASTERN PENNSYLVANIA

schist, and quartzite. This association is dissimilar to that of 

rocks in the Bel Air-Rising Sun terrane. The pyroxenite may 

have been thrust over this sequence of rocks and may represent another fragment of the Bel Air-Rising Sun terrane. 

Alternatively, the pyroxenite may be ultramafic rock preserved in a structurally higher thrust sheet unrelated to this 

terrane. In this regard, the pyroxenite represents a small 

sliver of oceanic crust emplaced within rocks having a volcanic arc affinity. Therefore, the pyroxenite, chlorite schist, 

biotite schist, and quartzite are related and would be part of 

the same terrane. Limited subsurface data available in this 

part of the Delaware Coastal Plain prohibit a more definitive interpretation. Our preference at this time is to interpret 

the pyroxenite as a separate fragment of ultramafic rock 

since it is south of, and seemingly unconnected to, the metagabbro farther north in Delaware. Hence, we do not think it 

is another detached fragment of the Bel Air-Rising Sun terrane. We interpret the pyroxenite, chlorite schist, biotite 

schist, and quartzite to be related, and we correlate them 

with similar rocks in the Roanoke Rapids terrane of Horton 

and others (1989). This terrane, as described by Boltin and 

Stoddard (1987), consists of greenschist-facies metavolcanic and metasedimentary rocks and associated ultramafic 

rocks of the Eastern slate belt and amphibolite facies 

gneisses of the Raleigh belt. By our interpretation, rocks 

correlative with the Roanoke Rapids terrane would extend 

through central Salem and Cumberland Counties and into 

Atlantic County (fig. 25). This is consistent with the interpretation of Sheridan and others (1991) whose gravity 

model suggests that this part of the New Jersey Coastal 

Plain may be underlain by ophiolite, metavolcanic rock, and 

melange.

The metaquartzite drilled in the Anchor Gas-Ragovin 

well (appendix, well no. 103) was seen in no other New Jersey wells. However, one well penetrating basement in Delaware, Eb 23-22 (appendix, well no. D6) encountered 

muscovite-free metaquartzite. No other wells in New Jersey 

are close enough to permit direct correlation with the 

Anchor Gas-Ragovin quartzite. In Delaware, several wells 

were drilled near Eb 23-22. Most penetrated a soft, 

light-green chlorite schist. One well (Ec 32-07) to the 

immediate east returned mica schist, and well Eb 44-08 just 

to the south returned pyroxenite (appendix, well nos. D7 

and D8, respectively). Metaquartzites are ubiquitous 

throughout the Appalachians and occur in several lithologic 

sequences from Middle Proterozoic through Paleozoic in 

age. There is nothing distinctive about the quartzite from the 

Anchor Gas-Ragovin well in terms of its mineralogy. Neither its thickness nor its lithologic associations are known.

If the quartzites from the Anchor Gas-Ragovin well 

and well Eb 23-22 in Delaware are coeval, then several possible interpretations exist as follows: (1) the association of 

pyroxenite and quartzite (metamorphosed chert?) could represent a partial ophiolite sequence; (2) the quartzites may 

not be valid units but may be thick quartz veins perhaps

associated with shear zones; or (3) the pyroxenite may be 

part of a more extensive mafic/ultramafic body that was 

structurally emplaced with the quartzite, chlorite schist, and 

biotite schist that occur to the immediate north. As stated 

above, we interpret the quartzite, chlorite schist, and biotite 

schist from Delaware to be related and to be part of a volcanic arc sequence that includes the pyroxenite. The Anchor 

Gas-Ragovin well appears to be along the same gravity 

trend (fig. 8) as the pyroxenite, quartzite, and surrounding 

wells in Delaware; it is located north of a pronounced gravity high.

The sequence of chlorite-quartz-plagioclase schist/ 

gneiss and altered metavolcanic rock penetrated in well Gd 

33-04 in northern Delaware (appendix, well no. Dll) 

occurs south of the pyroxenite in well Eb 44-08. No basement rock samples are available for the intervening area in 

Delaware. However, several wells along strike in eastern 

Maryland returned similar lithologies. Descriptions from 

wells KE-DB 40 and KE-BG 33 are of quartz-plagioclase 

gneiss containing chlorite with some associated quartzite 

and highly altered schist or gneiss containing chlorite and 

sericite, respectively (Hansen and Edwards, 1986). These 

same authors described another well farther to the west, 

CH-BE 57, which drilled chlorite-quartz-plagioclase schist. 

These Maryland wells are surrounded by wells that dominantly returned biotite-quartz-plagioclase gneiss or schist. 

In New Jersey, quartzite from the Anchor Gas-Ragovin well 

is on strike with the Maryland and Delaware wells. Well Gd 

33-04 in Delaware, the Maryland wells, and the New Jersey 

quartzite all occur in an area of slightly positive gravity 

anomalies (fig. 8) but subdued aeromagnetic expression 

(fig. 9). The similarity of the chlorite schist, biotite schist, 

and quartzite drilled north of the pyroxenite to rocks in 

some of the Maryland wells and the quartzite from the 

Anchor Gas-Ragovin well is striking, and we interpret them 

to be correlative. Therefore, we interpret that part of southern New Jersey and northern Delaware including the pyroxenite in well Eb 44-08 and the gravity high in central 

Cumberland County (fig. 25) is underlain by rocks correlative with the Roanoke Rapids terrane.

The rocks beneath the central part of the Coastal Plain 

are much more difficult to interpret because of the lack of 

data. The positive gravity (fig. 8) and aeromagnetic (fig. 9) 

anomalies in Monmouth and Burlington Counties occur 

along the same general structural and geophysical trend as 

anomalies that define the Wilmington Complex and the Baltimore Complex. Both complexes consist largely of mafic 

rock. The gravity and magnetic anomalies in Monmouth 

and Burlington Counties probably result from mafic rock of 

similar composition occurring at or beneath the basement 

surface. Sugarman (1981) modeled the Monmouth County 

body as rootless and extending no deeper than 0.8 mi. However, thus far, no wells have penetrated these bodies. In 

keeping with the interpretation of the Baltimore Complex 

(Crowley, 1976) and the Wilmington Complex (Crawford
CRYSTALLINE BASEMENT BENEATH THE NEW JERSEY COASTAL PLAIN AND CONTIGUOUS AREAS B33

and Mark, 1982; Wagner and Srogi, 1987; Horton and others, 1989) as allochthonous, we suggest that the Monmouth 

County and Burlington County mafic bodies are allochthonous also. They are herein named the Monmouth terrane 

and the Mount Holly terrane, respectively. Whether they are 

correlative with rocks in the Bel Air-Rising Sun terrane, or 

perhaps the Wilmington terrane, or whether they are bodies 

of mafic rock unrelated to either terrane or even to each 

other is difficult to say. Therefore, at this time, they are 

shown as separate terranes on figure 25.

The graphite in the New Jersey Highway Authority 

well (appendix, well no. 35) and the U.S. Geological Survey 

Freehold observation well (appendix, well no. 38) in Monmouth County, N.J., the W.&K. Oil Company well (appendix, well no. 42) and the Oxly 1A well (appendix, well no. 

45) in Ocean County, N.J., and the Brooklyn Union Gas 

Company well (appendix, well no. N9) in Queens County, 

N.Y., is significant, as these wells all occur in a linear 

north-northeast-trending belt. The closest exposed crystalline rocks that are lithologically similar and contain graphite 

are the following rocks of the Manhattan prong: (1) the 

Middle Proterozoic Fordham Gneiss (unit V of Brock, 

1989); (2) the informal Late Proterozoic and Cambrian Ned 

Mountain formation of Brock (1989), which is correlated 

with the Pound Ridge Granite and Yonkers Gneiss; and (3) 

the Ordovician Walloomsac Formation (Brock, 1989; Hall, 

in press). These units are within the North American Craton 

terrane of Zen and others (1989). One problem with correlating any of these rocks with the New Jersey well samples 

is that rocks between the Fordham and Walloomsac occur 

west of the Cameron's Line thrust fault, whereas these wells 

project to the east of the Cameron's Line thrust fault (fig. 

12). Other possible correlations in southwestern Connecticut include The Straits Schist (equivalent to the Goshen 

Formation in Massachusetts), the Wepawaug Schist (equivalent to the Waits River Formation in Massachusetts), the 

Hawley Formation, or the Harrison Gneiss (Rodgers, 1985), 

all of which are graphite bearing and occur east of the Cameron's Line fault. They occur within the Brompton-Cameron terrane of Zen and others (1989) but to the east of 

rocks in this terrane correlative with those of the Potomac 

terrane. Each of the aforementioned wells is located along 

gravity (fig. 8) and aeromagnetic (fig. 9) trends that are 

more similar to trends of the Brompton-Cameron terrane 

than to trends of the cover-sequence rocks in the Manhattan 

prong (North American Craton terrane). Therefore, the best 

correlation appears to be with the graphitic schists in southern Connecticut. Unfortunately, none of the graphitic well 

samples is fresh enough for geochemical analysis. These 

carbonaceous schists likely represent a sequence of metamorphosed graywacke and minor pelitic rocks that were 

deposited in a locally restricted marine basin.

During the 1960's, pelmatozoan fragments were discovered at the base of the Walloomsac near its contact with 

the Inwood Marble in the Verplanck Point Quarry in the

Manhattan prong (Ratcliffe and Knowles, 1968). This fossiliferous unit is underlain by a white dolostone. It is possible that the schist drilled in the W&K. Oil Company well at 

Jacksons Mills (appendix, well no. 42) may be Walloomsac 

and that the "fossils" (Henry Kummel, New Jersey Geological Survey permanent notes, 1922) recovered from this well 

(if there is any validity to this report) occur in the same 

basal part of the formation. Because each of these central 

Coastal Plain wells is outboard of the Potomac terrane, 

interpreting the schist in the W.&K. Oil Company well as 

Walloomsac would require the Walloomsac to occur in a 

window beneath accreted terranes exposed farther to the 

west. Our preference is to interpret the rock drilled in these 

wells as being correlative with schists in the Brompton-Cameron terrane for reasons already stated.

The phlogopitic marble from the Butler Place well 

(appendix, well no. 53) may correlate with the phlogopitic 

metalimestone member of the Cockeysville Marble (Crowley and others, 1975) in the Maryland, Delaware, and Pennsylvania Piedmont, with the Inwood Marble, or with the 

phlogopitic marble member (Hall, in press) of the Walloomsac Formation in the Manhattan prong, or with siliceous marble in the Waits River or Gile Mountain 

Formations in southern New England. As stated above, the 

association of pelitic schist and marble from bedrock wells 

in the central Coastal Plain suggests that these rocks may be 

spatially related and equivalent to cover-sequence rocks 

cropping out in the Manhattan prong or in the Connecticut 

Valley synclinorium to the northeast. If they are correlative 

with the basement and cover-sequence rocks in the Manhattan prong, then the rocks in this part of the Coastal Plain 

would occur in a window beneath the thrust sheet(s) that 

transported rocks of the Potomac terrane farther to the west. 

However, because rocks in the Manhattan prong do not 

appear to be along the same gravity and aeromagnetic trend 

as the Butler Place well, or any of the wells penetrating graphitic schist, and because the Butler Place well is outboard 

of Potomac terrane rocks, the best correlation appears to be 

with rocks in the Connecticut Valley synclinorium (Brompton-Cameron terrane). The associated schist and marble in 

the central Coastal Plain are shown as a component of this 

terrane on figure 25.

The outermost edge of the New Jersey Coastal Plain 

was penetrated only by the U.S. Geological Survey Island 

Beach State Park well (appendix, well no. 46) and the 

Anchor Gas-Dickinson well (appendix, well no. 104). The 

migmatitic quartzofeldspathic gneiss from the Island Beach 

State Park well is important in that it is the easternmost 

sample of basement available. It occurs just west of the projected trend of several exposed and inferred early Mesozoic 

basins. These include the Hartford basin in Connecticut; the 

inferred New York Bight basin south of Long Island 

(Hutchinson and others, 1986); an inferred, unnamed basin 

in southern Cumberland and Atlantic Counties, N.J. (Benson, 1992); the Queen Anne basin in eastern Maryland
B34 GEOLOGIC STUDIES IN NEW JERSEY AND EASTERN PENNSYLVANIA

(Hansen, 1988), which Benson (1992) extended into northcentral Delaware; and the Taylorsville basin in Virginia. The 

Taylorsville Basin is in contact on the northwest with rocks 

of the Goochland terrane along the Hylas fault zone (Farrar, 

1984). As described by Farrar, rocks of the Goochland terrane consist of the State Farm Gneiss, which crops out in a 

series of domelike structures, overlain by the Sabot 

Amphibolite, Maidens Gneiss, and meta-anorthosite of 

Montpelier, which contain relict granulite-facies mineral 

assemblages overprinted by amphibolite-facies assemblages.

As stated above, chemistry of the Island Beach State 

Park well sample from a depth of 3,890 ft reveals that this 

rock is metagraywacke. The State Farm Gneiss is similar 

mineralogically, but it is characterized by abundant titanite, 

whereas the metagraywacke from this well contains only 

trace amounts of titanite (table 1) and a low TiO2 content 

(table 2). Parts of the Maidens Gneiss are also similar mineralogically to this well sample; however, the latter displays 

no evidence of relict granulite-facies assemblages. Unfortunately, no chemistry, published or unpublished, exists for 

rocks in the Goochland terrane (L. Glover, oral commun., 

1990), making any correlation with lithologies in the Maidens Gneiss largely speculative. No rocks fitting the description of Goochland lithologies were encountered in New 

Jersey in any of the wells for which samples are available. 

Therefore, at this time, we doubt that rocks having an affinity to the Goochland terrane extend into New Jersey. This 

interpretation receives support from a reexamination of the 

potential-field data by D.L. Daniels (written commun., 

1993), suggesting that gravity and magnetic trends similar 

to those of the Goochland terrane may not continue into 

New Jersey.

The Island Beach State Park well is along the same 

structural and magnetic trend as rocks in the Connecticut 

Valley synclinorium (Brompton-Cameron terrane) occurring west of the Hartford basin in southern Connecticut. The 

closest well in New Jersey is the Oxly 1A well (appendix, 

well no. 45) to the west. The graphitic schist/gneiss from 

this well appears to have an affinity to some of the sulfidic, 

carbonaceous rocks in the Brompton-Cameron terrane. The 

location of the Island Beach State Park well west of the projection of several inferred, buried, early Mesozoic basins 

from Connecticut to Maryland suggests that it is likely part 

of the Brompton- Cameron terrane also. This is more consistent with the lithologic association of nearby wells in 

New Jersey and also exposed rocks along strike in southern 

Connecticut than a correlation with Goochland terrane 

lithologies. Therefore, for reasons stated, as well as the 

closeness of the Island Beach State Park well to the rocks in 

southern Connecticut, we propose that the eastern edge of 

New Jersey is underlain by rocks correlative with the Brompton-Cameron terrane (fig. 25).

Fine-grained metagabbro from the bottom of the 

Anchor Gas-Dickinson well (appendix, well no. 104) has a

distinctly enriched tholeiitic composition (fig. 20) that is 

unlike that of eastern North American Jurassic basalt or diabase. Thus, correlation with a flow or dike in a buried Mesozoic rift basin can be ruled out. Metagabbro contains 

major-element abundances similar to those of microgabbro 

and quartz gabbro from the Baltimore Mafic Complex 

described by Hanan and Sinha (1989) and Higgins and Conant (1990). Unfortunately, no published trace-element abundances for these rocks are available for comparison.

The occurrence of gabbro in the Anchor Gas-Dickinson well in an area of negative gravity expression (-20 milligals, fig. 8) and moderate aeromagnetic expression (600 to 

800 gammas, fig. 9) is enigmatic. Hansen and Edwards 

(1986) described similar gabbro from well WO-CE 12 

(Mobil Bethards No. 1) in the eastern shore of Maryland 

just south of Delaware. This well is along the same gravity 

and aeromagnetic trend as the Anchor Gas-Dickinson well. 

These wells are approximately 40 mi apart, yet they 

returned identical rocks. The absence of positive gravity and 

magnetic anomalies in this part of New Jersey suggests that 

gabbro in the Anchor Gas-Dickinson well may be preserved 

as a very thin thrust slice above more felsic rocks or that it 

occurs very locally in a volcanic arc sequence. The latter 

interpretation is supported by the occurrence of low-grade 

metamorphic rocks, namely volcaniclastic phyllite and calcareous metasiltstone, to the south of WO-CE 12 in Maryland and Virginia (Hansen and Edwards, 1986). If this 

mixture of rock types is related, then they may be correlative with Eastern slate belt rocks (Chesapeake block of Horton and others, 1991). These consist of greenschist- grade 

metasedimentary and metavolcanic rocks locally intruded 

by gabbro. The Anchor Gas-Dickinson well, WO-CE 12, 

and the Eastern slate belt occur along similar gravity and 

aeromagnetic trends. Because the Anchor Gas-Dickinson 

well occurs outboard of the Delaware well that returned 

pyroxenite, correlation with the Bel Air-Rising Sun terrane 

seems unlikely. It is possibly coextensive with other gabbro 

and greenschist-facies metamorphic rocks in the Chesapeake block as described by Horton and others (1991). 

However, because this terrane is distanced from the Anchor 

Gas-Dickinson well, gabbro from it may represent a separate terrane fragment. We, therefore, tentatively name this 

the Cape May terrane.

Several workers (for example, Hutchinson and others, 

1986; Benson and Doyle, 1988; Sheridan and others, 1991; 

Benson, 1992) have proposed that buried Mesozoic rift 

basins containing rocks correlative with those in the Newark basin occur beneath the Coastal Plain in New Jersey and 

adjacent States, as well as offshore. With the exception of 

Mesozoic rocks encountered in wells along the Fall Line in 

New Jersey, only a few wells, none of which are in New Jersey, have definitively penetrated Mesozoic sedimentary or 

igneous rocks, and the presence of such rocks has been 

inferred largely from seismic-reflection profiles and gravity 

modeling. Several wells beneath the Maryland Coastal Plain
CRYSTALLINE BASEMENT BENEATH THE NEW JERSEY COASTAL PLAIN AND CONTIGUOUS AREAS B35

summarized in Hansen and Edwards (1986) penetrated red 

sedimentary rocks occurring along a northeast trend. A seismic-reflection profile to the east of these wells imaged what 

Hansen (1988) has tentatively named the Queen Anne 

basin. By using aeromagnetic data, Benson (1992) inferred 

the presence of a separate, but parallel, buried, early Mesozoic basin in southern Cumberland County, N.J., south of a 

gravity high (fig. 25). Sheridan and others (1991) interpreted parts of southern Gloucester and Camden Counties 

and northern Atlantic County to be underlain by a buried, 

early Mesozoic basin, which they have named the Buena 

basin. Their interpretation is based on a seismic-reflection 

profile and gravity modeling. The locations of these inferred 

basins are shown on figure 25.

The Anchor Gas-Dickinson well in New Jersey 

encountered a 140-ft-thick sequence of pale-pinkish-tan, 

angular to subangular quartz sand and clayey silt directly 

overlying crystalline basement. It is possible that this is 

sandstone of Mesozoic age as suggested by Doyle (lithologic log, on file in the office of the New Jersey Geological 

Survey, Trenton, N.J.). It is also possible that this material is 

from the Potomac Formation. Although the sediment thickness is anomalous for a buried rift basin, that the margin of 

one was drilled cannot be totally discounted. If this is, in 

fact, the margin of a buried rift basin, it is south of the 

inferred basin of Sheridan and others (1991) and also south 

of the projected subsurface trace of the Queen Anne basin 

(Benson, 1990, 1992) and the unnamed basin of Benson 

(1992). However, we interpret this quartz sand to be part of 

the Potomac Formation and do not think that crystalline 

basement was penetrated at this depth in the Anchor GasDickinson well.

CONCLUSIONS

1. The crystalline basement complex in New Jersey is 

overlain along the Fall Line by the Stockton Formation 

and to the southeast by unconsolidated sediments 

mainly of the Potomac Formation. Saprolite was 

encountered in nearly every well and locally is more 

than 150 ft thick.

2. The pre-Mesozoic subsurface basement in New Jersey 

likely consists of a stack of thrust sheets representing a 

composite of accreted terranes.

3. The inner Coastal Plain is underlain dominantly by 

amphibolite-facies pelitic and psammitic schists of the 

Potomac/Philadelphia terrane. These rocks are probably equivalent, at least partially, to the western part of 

the Brompton-Cameron terrane in southern New 

England. In New Jersey, these rocks were deposited in 

a marginal, perhaps back arc, basin to the east of the 

North American craton. Amphibolites associated with 

these schists in Gloucester County, N.J., are geochemically divisible into two basalt types. Type 1 basalts

have N-MORB and E-MORB affinities and were 

erupted at, or proximal to, a small spreading center in 

this marginal basin. Type 2 basalts are chemically similar to other occurrences of Late Proterozoic basalt and 

diabase from throughout the Appalachians and are 

therefore interpreted by us also to be Late Proterozoic 

in age. They may have intruded along a leaky transform fault. Amphibolites of basaltic andesite and type 

2 basalt compositions are associated with pelitic and 

psammitic schists as sills and dikes. Major- and traceelement abundances suggest that basaltic andesite fractionated from type 2 basalt. Type 1 basalt is less fractionated and tapped a separate, possibly shallower, 

mantle source.

4. Rocks of the James Run Formation (Chopawamsic terrane) may extend into New Jersey into central Salem 

County. The absence of drill-hole data in this area, as 

well as in southern Gloucester County, provides neither proof nor disproof of the occurrence of the James 

Run Formation in New Jersey.

5. Pyroxenite encountered in the Delaware subsur- face 

may be related to ultramafic rocks in the Bel Air-Rising Sun terrane (Aberdeen block) or may be a separate 

fragment in a structurally higher slice. It is tentatively 

interpreted as being the latter and is correlated with 

similar rocks of the Roanoke Rapids terrane (Eastern 

slate belt).

6. Quartzite in the Anchor Gas-Ragovin well is on strike 

with, and north of, the same gravity high as quartzite, 

chlorite schist, biotite schist, and altered metavolcanic 

rock from wells in northern Delaware and eastern 

Maryland. These rocks may represent a volcanic arc 

sequence. We interpret them to be correlative with 

rocks of the Roanoke Rapids terrane (Eastern slate 

belt).

7. The associated gravity and aeromagnetic anomalies in 

Monmouth County and Burlington County coincide 

with a structural high in the basement. Thinning of 

Coastal Plain sediments here reflects structural complexities in the basement. Gravity and magnetic data 

permit the interpretation of high-density mafic rock 

that occurs either in a rootless pluton or in a thrust 

slice extending to a depth of less than 1 mi. The alignment of the Baltimore Complex and Wilmington Complex with these bodies along the same structural trend 

and gravity high suggests that they may be related. The 

Monmouth County body is herein named the Monmouth terrane, and the Burlington County bodies are 

herein named the Mount Holly terrane.

8. Graphitic schists from the northern part of the Coastal 

Plain are probably related to marble and carbonaceous 

schist encountered farther to the south. We suggest a 

possible correlation with rocks of the Brompton-Cameron terrane because they are along the same gravity 

and aeromagnetic trend. The assignment of these rocks
B36 GEOLOGIC STUDIES IN NEW JERSEY AND EASTERN PENNSYLVANIA

east of the occurrence of Potomac terrane rocks is consistent with the assignment of similar rocks occurring 

east of Hartland or Manhattan in southern New England and New York. If the graphitic schist and marble 

correlate with the Walloomsac Formation and rocks of 

the North American Craton terrane, then they are outboard of rocks in the Potomac/Philadelphia terrane and 

may be exposed in a window through accreted terranes 

transported farther to the west.

9. The reported occurrence of Ordovician fossils from 

beneath schist at the W.&K. Oil Company well at 

Jacksons Mills, N.J., is scientifically intriguing but 

unsubstantiated. The available facts suggest there may 

be little validity to this report.

10. Metagabbro from the Anchor Gas-Dickinson well is 

herein named the Cape May terrane. It may be a continuation of gabbro and associated greenschist-facies 

metamorphic rocks from eastern Maryland. It is possible that these rocks correlate with rocks of the Chesapeake block (Eastern slate belt).

11. Rocks of Mesozoic age were penetrated by wells along 

the Fall Line in Middlesex and Mercer Counties. To 

the south, evidence for early Mesozoic buried rift 

basins beneath the New Jersey Coastal Plain is equivocal; thus far no well has drilled rock that can be definitively identified as Mesozoic. However, there are areas 

in southern New Jersey untested by drilling where 

gravity and magnetic data suggest the possible presence of small, buried, early Mesozoic basins.

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the New Jersey Coastal Plain—Implications for continental 

growth: Geological Society of America Bulletin, v. 103, 

p. 402-414.

Shervais, J.W., 1982, Ti-V plots and the petrogenesis of modern 

and ophiolitic lavas: Earth and Planetary Science Letters, v. 

59, p. 101-118.

Shibata, Tsugio, Thompson, Geoffrey, and Frey, FA., 1979, Tholeiitic and alkali basalts from the Mid-Atlantic ridge at 43 N: 

Contributions to Mineralogy and Petrology, v. 70, p. 127-141.

Shimizu, Hiroshi, and Masuda, Akimasa, 1986, REE patterns of 

eucrites and their genetic implications: Geochimica et Cosmochimica Acta, v. 50, p. 2453-2460.

Sinha, A.K., and Bartholomew, M.J., 1984, Evolution of the Grenville terrane in the central Appalachians, in Bartholomew, 

M.J., ed., The Grenville event in the Appalachians and related 

topics: Geological Society of America Special Paper 194, 

p. 175-186.

Smith, R.C., II, Berkheiser, S.W., and Barnes, J.H., 1991, Pennsylvania's version of the Catoctin metabasalt story, in Sevon, 

W.D., and Potter, Noel, Jr., eds., Geology in the South Mountain area, Pennsylvania, Guidebook for the 56th annual field 

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Southwick, D.L., 1964, Petrography of the basement gneiss 

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New Jersey: U.S. Geological Survey Professional Paper 501- 

C, p. C55-C60.

———1969, Crystalline rocks—The geology of Harford County, 

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Stanley, R.S., and Ratcliffe, N.M., 1985, Tectonic synthesis of the 

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Sugarman, P.J., 1981, The geological interpretation of gravity 

anomalies in the vicinity of Raritan Bay, New Jersey and New 

York: Newark, University of Delaware, M.S. thesis, 135 p.

Sun, S.S., Nesbitt, R.W., and Sharaskin, A.Y., 1979, Geochemical 

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Tarns Consultants, Inc., 1988, Boring logs for Liberty State Park— 

Unpublished consultant's report on file in the office of the 

New Jersey Geological Survey, Trenton, N.J.

Turner, F.J., and Verhoogen, J., 1960, Igneous and metamorphic 

petrology: New York, McGraw Hill, 694 p.

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in New Jersey and eastern Pennsylvania: U.S. Geological 

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at two crustal levels and a tectonic model for the Pennsylvania-Delaware Piedmont: Geological Society of America Bulletin, v. 99, p. 113-126.

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B40 GEOLOGIC STUDIES IN NEW JERSEY AND EASTERN PENNSYLVANIA

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discrimination—Application to altered and metamorphosed 

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28, p. 459-469.

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the use of trace elements to classify and discriminate between 

magma series erupted in different tectonic settings: Earth and 

Planetary Science Letters, v. 45, p. 326-336.

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variations in Atlantic Ocean basalts and Proterozoic dykes 

from northwest Scotland—Their bearing upon the nature and 

geochemical evolution of the upper mantle: Tectonophysics, 

v. 75, p. 91-112.

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New Brunswick, N.J., Rutgers University, M.S. thesis, 48 p.

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J.W, and Thompson, J.B., Jr., 1989, Tectonostratigraphic terranes in the northern Appalachians—Their distribution, origin, and age: Evidence for their existence—Field Trip 

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Geophysical Investigations Map GP-942, scale 1:2,000,000.
APPENDIX
B42 GEOLOGIC STUDIES IN NEW JERSEY AND EASTERN PENNSYLVANIA

Appendix. Selected Coastal Plain wells and seismic stations in New Jersey and contiguous areas that penetrate basement rock

[Location of wells is shown in figure 10. Elevation was estimated in feet above sea level from USGS 7.5-min topographic map. Sample type symbols: D, 

driller's log; G, geologists' log; GT, geologic description from this study. USGS, U.S. Geological Survey; Do. (do.), ditto; Fm., Formation]

Well 

no. Owner or name Latitude Longitude

Elevation 

(ft)

Depth to 

basement

(ft) Sample type Description Reference

MIDDLESEX COUNTY

1

2

3

4

4a

5

6

7

8

9

10

11

12

13

14

15

16

17

18

19

20

21

22

23

Harold Kuhn

American Cyanamid

Stephen Futo

California Refining Co.

Chevron Oil Co. #11

R & H Chemical Co.

Duhernal Water Board

DuPont#13

Man & Engine Co. #29

National Lead Co.

Man & Engine Co. #3

Water Policy Comm.

Hercules #2

DuPont

Laurence Smith

Middlesex Development Co.

Anheuser-Busch

Madison Water Co.

Duhernal Water Co.

Kimberly-Clark Co.

Stauffer Chemical #7

State Home for Boys

Clifford Stultz

Clifford Stultz

403220

403233

403207

403207

403211

403047

402940

402900

402820

402833

402740

402740

402700

402700

402407

402433

402433

402353

402340

402100

402125

402033

401833

401847

74 18 33

74 16 20

74 18 20

74 16 47

74 16 12

741607

74 18 07

74 19 13

74 20 47

741807

74 20 33

74 22 07

74 20 07

74 19 13

74 26 07

74 24 33

74 22 07

74 20 47

74 22 47

742940

74 28 25

74 23 26

74 34 07

74 33 53

170

15

150

50

14

30

10

8

23

140

100

5

50

100

115

90

20

40

10

125

128

100

90

95

+ 10

58

20

89

83

145

115

91

51

200

165

86

235

259

115

170

292

330

302

208

180

405

90

105

Cuttings

do.

do.

do.

do.

do.

do.

do.

do.

do.

do.

do.

do.

do.

do.

do.

do.

do.

do.

do.

Core

Cuttings

do.

do.

(G)

(D)

(D)

(D)

(D)

(D)

(D)

(D)

(D)

(D)

(D)

(D)

(D)

(D)

(D)

(D)

(D)

(D)

(D)

(G)

(GT)

(D)

(G)

(G)

Passaic Formation Red

Mesozoic shale.

Greenish-gray baked

Mesozoic shale.

Dusky-red, finely micaceous,

slightly calcareous Mesozoic shale.

Metamorphosed hard

gray Mesozoic shale.

"Soapstone"

Red Mesozoic shale

Mesozoic diabase

Mesozoic rock

Mesozoic diabase

Red Mesozoic shale

Mesozoic rock

Mesozoic diabase

Red Mesozoic shale

Mesozoic sandstone

Stockton Formation

"Light-colored sandstone."

Mesozoic Stockton Fm.

Basement

Basement

Basement

Red Mesozoic shale fragments.

Red clay and weathered

Mesozoic shale.

Basement

Decomposed "Wissahickon"

Weathered "Wissahickon"

(granitic).

Johnson (1961).

Kasabach and Scudder

(1961).

Do.

Do.

Gronberg and others

(1989).

Kasabach and Scudder

(1961).

Do.

(')

Do.

Do.

Do.

Kasabach and Scudder

(1961).

(>)

Kasabach and Scudder

(1961).

Do.

Do.

Do.

Do.

Do.

Johnson (1961).

Kasabach and Scudder

(1961).

Johnson (1961).

Do.

MERCER COUNTY

24

25

26

Heyden Chemical (1946)

Wing King

Peddie Inst.

401930

401740

401553

74 37 52

74 36 07

7431 26

55

100

108

+31

+ 18

374

do.

do.

do.

(D)

(D)

(D)

Stockton Formation — Light

sandstone and interbedded

Mesozoic shale; "Wissahickon" at 377 ft below sea

level (granitic).

Pre-Mesozoic basement

Pre-Mesozoic basement

Do.

Kasabach and Scudder

(1961).

Do.
CRYSTALLINE BASEMENT BENEATH THE NEW JERSEY COASTAL PLAIN AND CONTIGUOUS AREAS B43

Appendix. Selected Coastal Plain wells and seismic stations in New Jersey and contiguous areas that penetrate basement rock— 

Continued

Well

no. Owner or name

27

28

29

30

31

32

Mercer County Park

Robbinsville Hotel

Hamilton Sq. Water Co.

F. Agabiti

Hamilton Sq. Water Co.

Cocavio Bros.

Latitude

401705

401513

401433

401353

401353

401233

Longitude

743900

74 37 40

74 40 20

74 40 47

74 39 53

7443 13

Depth to 

Elevation basement

(ft) (ft)

62 15

120 240

75 79

90 66

100 115

60 82

Sample type

Core

Cuttings

do.

do.

do.

do.

(GT)

(D)

(D)

(D)

(G)

(D)

Description

Medium-grained, moderately

foliated, pale-weathering,

light-greenish-gray hornblende-pyroxene-quartzbiotite-plagioclase gneiss

with trace sulfide. Quartz is

colorless to blue. Minor

medium- to coarse-grained,

pinkish-white weathering,

afoliate microperthite alaskite with 2 feldspars & blue

quartz. Also minor greenish-gray, fine-grained to

aphanitic metabasalt.

Pre-Mesozoic basement

Pre-Mesozoic basement

Pre-Mesozoic basement

Highly weathered "Wissahickon" schist.

Weathered mica gneiss

Reference

Kasabach and Scudder

(1961).

Do.

Do.

Johnson (1961).

Kasabach and Scudder

(1961).

MONMOUTH COUNTY

33

34

35

36

37

38

39

40

Union Beach Water Dept.

Levitt&Sons, Inc., PHI

New Jersey Highway

Authority.

Gordons Corner Water Co.

RHMacyTHl

USGS Freehold observation

well.

USGS NJ Water Supply

Manasquan Reservoir.

Punk Bros.

402632

402353

402313

401913

401727

401517

40 11 05

401005

741051

74 12 47

74 10 33

74 18 07

74 03 13

741351

741202

74 29 39

10 599

90 607

215 743

160 718

60 811

205 1065

110 1390

129 659

do.

Core

Cuttings

do.

do.

Core

Cuttings

do.

(D)

(G)

(GT)

(D)

(D)

(GT)

(G)

(D)

Pre-Mesozoic basement

Clay, mostly decayed mica

schist with zones of white

granite. Schist is dark red,

white, and green with zones

of black speckling.

Pale-olive, highly weathered,

fine- to medium-finegrained chlorite-biotitemuscovite-quartz-feldspar

schist with trace staurolite

and graphite.

Weathered pre-Mesozoic

basement.

Bedrock(?), weathered

Highly weathered, mediumfine-grained, moderately

well foliated, graphitic garnet-biotite-quartz feldspar

schist.

Weathered biotite schist

Pre-Mesozoic basement

Lloyd and others (1985).

F.J. Markewicz, unpublished lithologic log.

( l )

Daniels and Leo (1985).

Brown and Zapecza (1990).

Lloyd and others (1985).

OCEAN COUNTY

41

42

W.S.DriverOilCo.

W.&K. Oil Co.

400740

400900

742807

74 19 13

110 990

110 1226

do.

do.

(D)

(GT)

Pre-Mesozoic basement

Total depth is 5,022 ft.; 3,000

Kasabach and Scudder

(1961).

ft to 4,832 ft—mediumfine-grained garnetbioite-quartz-feldspar 

schist with trace sulfide. 

4,832-ft to 4,840 ft—the 

same with accessory graphite. 4,850 ft—mediumfine- to medium-grained 

gamet-Wotite-chloritemuscovite-quartz-feldspar 

schist.
B44 GEOLOGIC STUDIES IN NEW JERSEY AND EASTERN PENNSYLVANIA

Appendix. Selected Coastal Plain wells and seismic stations in New Jersey and contiguous areas that penetrate basement rockContinued

Well

no.

43

44

45

46

Owner or name

Jackson Twp. MUA #9

Brick Twp. MUA #9

Oxly 1A

USGS Island Beach State

Park.

Latitude

400652

400431

39 45 55

39 48 29

Longitude

74 17 17

74 08 32

74 21 39

74 05 35

Depth to 

Elevation basement

(ft)

135

8

138

10

(ft)

1515

1776

3082

3793

Sample type

do.

do.

do.

Core

(D)

(D)

(GT)

(G,

GT)

Description

Clay, weathered

Weathered zone

Pale-olive, highly weathered,

medium-grained chloritemuscovite-biotite-quartzfeldspar schist or gneiss

with accessory sulfide and

trace graphite. Feldspar

chalky.

Migmatitic gamet-muscovitemicrocline-biotite-quartzplagioclase gneiss (Southwick, 1964) and mediumgrained gamet-hornblendebiotite-quartz-feldspar

gneiss (this study).

Reference

Lloyd and others (1985).

(*)

Southwick (1964).

BURLINGTON COUNTY

47

48

49

50

51

52

53

54

55

56

57

58

59

60

61

62

63

U.S. Engineering Corps

National Gypsum #2

McGuire AFB #A

McGuire AFB #2

Helis Stock Farm

Burlington County

Institution #1.

Butler Place test wellLebanon State Forest.

Levitt & Sons Adm.

Levitt & Sons, Inc., #8

Levitt & Sons, Inc., #21

Levitt & Sons, Inc., DCB-25

Levitt & Sons, Inc., DCB-27

Levitt & Sons, Inc., DCB-12

Delaware River Water

Company #17

Delaware River Water Co.

Shell Chemical Company

Riverton-Palmyra Water

401033

400620

400207

400140

400054

39 58 12

395127

4003 13

400233

400220

400153

400140

400033

400220

400207

4001 13

400047

74 42 07

744940

74 36 07

74 35 26

744000

74 38 36

74 30 20

745340

74 54 33

74 54 20

74 52 33

74 52 07

75 52 47

74 56 47

745740

74 58 33

740140

70

15

124

160

%

59

132

33

39

15

27

40

55

20

20

20

10

240

142

936

940

891

711

20%

209

1%

260

331

371

445

115

71

125

86

Cuttings

do.

do.

do.

do.

do.

Core

Cuttings

do.

do.

do.

Core

do.

do.

do.

(D)

(D)

(D)

(G)

(D)

(G)

(G)

(G)

(G)

(G)

(G)

(G)

(D)

(D)

(D)

Cuttings (D)

do. (D)

Basement

Mica rock

Weathered basement

"Wissahickon"; contains

biotite, quartz, and some

feldspar.

"Wissahickon'X?): hard sandstone, probably weathered

bedrock.

"Wissahickon"(?)

Fine-grained, greenish-gray,

laminated carbonate rock

composed of 40% carbonate plus phlogopite, chlorite, and an aggregate of

montmorillonite, illite, and

chlorite.

Decayed basement rock

Mica schist — "Wissahickon"

Schistose gneiss and biotite

schist.

Highly weathered

"Wissahickon" gneiss.

Weathered "Wissahickon"

schist.

Pre-Mesozoic basement

Pre-Mesozoic basement

Weathered rock —

"Wissahickon"(?).

Pre-Mesozoic basement

Weathered rock —

(1)

Kasabach and Scudder

(1%1).

Do.

Johnson (1961).

Daniels and Leo (1985).

Do.

U.S. Geological Survey

(1%7).

(')

Do.

Do.

Do.

Do.

Kasabach and Scudder

(1%1).

Do.

Do.

Do.

Do.

Co. #8 

64 Cinnaminson MW F-2 400036 745835

65 Sanitary Landfill GM-4 400020 745833

66 Riverton-Palmyra WC. #10 395927 745913

65

60

80

"Wissahickon." 

185 do. (GT) Saprolitic, gray, gametmuscovite-biotite-quartzplagioclase schist or gneiss. 

+40 Core (G) Micaceous bedrock with ( l )

layers of fine sand. 

226 Cuttings (D) Weathered pre-Mesozoic Do.

basement.
CRYSTALLINE BASEMENT BENEATH THE NEW JERSEY COASTAL PLAIN AND CONTIGUOUS AREAS B45

Appendix. Selected Coastal Plain wells and seismic stations in New Jersey and contiguous areas that penetrate basement rock— 

Continued

Well

no.

67

68

69

Owner or name

Maple Shade WD

MSWD#5

Moorestown WD #1

Mount Laurel Water Co.

Latitude

39 57 25

395700

395606

Longitude

74 59 14

74 57 48

74 56 30

Depth to 

Elevation basement

(ft)

20

20

30

(ft)

474

476

564

Sample type

do.

do.

do.

(D)

(D)

(D)

Description

Pre-Mesozoic basement

"Wissahickon"

Weathered "Wissahickon"

Reference

Do.

Daniels and Leo (1985).

Do.

CAMDEN COUNTY

70

71

72

73

74

75

76

77

78

79

PennsaukenSLFHD

Merchantville-Penns WC-#1

Camden City #6

U.S. Gasket Company

Camden City #5

Camden City Sewage Plant

#1.

Gloucester City

NJ Water Company #14

NJ Water Company

USGS New Brooklyn Park

#1.

39 59 53

39 57 27

39 57 13

39 57 13

39 55 53

39 55 23

39 53 53

39 52 47

39 52 33

39 42 07

75 02 26

75 02 33

750540

75 07 13

75 05 40

75 07 29

740713

75 03 26

750300

74 55 53

20

60

50

20

40

9

5

85

70

110

85

232

130

121

237

192

271

517

557

1831

Core (GT)

Cuttings (D)

do.

do.

do.

do.

do.

do.

do.

Core

(D)

(D)

(D)

(D)

(D)

(D)

(D)

(GT)

Buff to yellowish-tan saprolite containing muscovite,

quartz, and kaolinite.

Mica rock — Pre-Mesozoic

basement.

Pre-Mesozoic basement

Weathered pre-Mesozoic

basement.

"Wissahickon" schist

"Wissahickon"

Pre-Mesozoic basement

White mica rock

Highly weathered basement

Highly weathered, pale-greenish-gray, fine- to mediumgrained biotite-muscovitequartz-plagioclase schist or

gneiss. Accessory garnet

and sillimanite. Feldspar

chalky and altered.

Kasabach and Scudder

(1961).

Do.

Do.

(*)

Do.

Kasabach and Scudder

(1961).

(*)

Kasabach and Scudder

(1961).

GLOUCESTER COUNTY

80

81

82

83

84

85

86

87

Texas Co. # 3

National Park Boro. #3

CityofWoodbury

USGS Deptford observation

well.

Vacuum Oil Co.

DuPont Repauno Works

DuPont Repauno Works

TH#4.

Hercules Powder Co.

39 52 07

395140

39 50 07

39 49 57

395100

39 50 33

39 50 33

38 49 53

750926

751100

75 08 47

75 05 30

75 15 13

75 16 33

75 17 40

75 19 26

10

25

30

35

10

20

20

10

278

263

403

643

308

118

95

210

Cuttings (D)

do.

do.

do.

do.

Core

do.

Cutting

(D)

(D)

(GT)

(D)

(GT)

(G)

!S(D)

Pre-Mesozoic basement

Pre-Mesozoic basement

"Wissahickon" — weathered

mica rock.

Medium-grained schist composed of muscovite, biotite,

quartz, and partially altered

feldspar, sparse accessory

garnet, and trace sulfide.

Pre-Mesozoic basement

Schist and gneiss composed

of muscovite, biotite,

quartz, and plagioclase with

sparse accessary garnet and

trace sillimanite. Some

schist contains hornblende.

Also medium-grained

amphibolite composed of

hornblende and plagioclase.

Mica schist and amphibolite

Pre-Mesozoic basement

Kasabach and Scudder

(1961).

Do.

Do.

Kasabach and Scudder

(1961).

F.J. Markewicz, unpub.

lithologic log.

Kasabach and Scudder

(1961).
B46 GEOLOGIC STUDIES IN NEW JERSEY AND EASTERN PENNSYLVANIA

Appendix. Selected Coastal Plain wells and seismic stations in New Jersey and contiguous areas that penetrate basement rock— 

Continued

Well

no.

88

89

90

91

92

93

94

95

Owner or name

Gaventa Farms

Chemical Leaman

S&S Auction

Lopes Farm

Shoemaker Farm

Monsanto Chemical Co. #2

Monsanto Chemical Co.

USGS Clayton well

Latitude

39 48 02

39 47 56

39 47 43

39 47 22

394706

39 48 33

39 47 40

39 40 32

Longitude

75 1909

75 20 01

75 18 22

75 17 32

75 19 43

75 22 33

75 24 07

75 06 07

Depth to

Elevation basement

(ft) (ft)

10 240

20 240

12 311

28 398

7 333

10 143

5 118

140 1498

Sample type

Core

do.

do.

do.

do.

(GT)

(GT)

(GT)

(GT)

(GT)

Cuttings (D)

do.

do.

(D)

(GT)

Description

Muscovite-biotite quartzplagioclase schist with trace

sillimanite and sulfide. Also

thin, conformably interlayered, medium-grained

amphibolite.

Muscovite-biotite-quartzplagioclase schist with

accessory sillimanite, garnet, and trace sulfide.

Biotite-quartz-plagioclase

schist with minor accessory

garnet.

Muscovite-biotite-quartzplagioclase schist.

Saprolite reportedly 78 ft

thick. Muscovite-biotitequartz-plagioclase schist

with minor K-feldspar and

trace garnet and trace sulfide. Locally migmatitic

with layers composed of

quartz and plagioclase.

Pre-Mesozoic basement

Pre-Mesozoic basement

Schist composed of biotite

and abundant quartz with

sparse amounts of altered

feldspar and trace garnet

and sulfide.

Reference

Kasabach and Scudder

(1961).

Do.

SALEM COUNTY

96 Pan American Refining Co.

97

98

99

PT#1.

Ford, Bacon & Davis

Perms Grove Water Co.

DuPont Chambers

Works 45B

100 DuPont Camey Point

101

Works #7

Pennsville

102 City of Salem

39 46 33

39 45 27

39 43 53

394130

39 41 05

39 39 54

39 34 20

75 25 13

75 25 26

75 27 53

75 29 30

75 29 08

75 30 48

75 27 53

6 211

10 228

5 205

17 489

(?) Sample

from 542

and 555.

9 590

12 1364

do.

do.

do.

do.

do.

do.

do.

(D)

(D)

(G)

(D)

(G)

(G)

(G)

Mica rock

Pre-Mesozoic basement

80 ft of weathered rockmicaceous gneiss,

"Wissahickon'X?).

Weathered basement

Highly decomposed gneiss

composed of quartz, plagioclase, biotite, and chlorite

with minor muscovite.

Bedrock "pre-Cretaceous"

Weathered "Wissahickon"

Rosenau and others (1969).

Kasabach and Scudder

(1961).

Rosenau and others (1969).

Leggette, Brashears, &

Graham, Inc. (1979).

U.S. Geological Survey

(1967).

( l )

Johnson (1961).

CUMBERLAND COUNTY

103 Anchor Gas-Ragovin #1 39 25 12 745154 91 3610 do. (GT) Quartz-rich sand with trace

amounts of reddish-brown

garnet and muscovite.

CAPE MAY COUNTY

104 Anchor Gas-Dickinson #1 38 56 33 74 57 26 14 6357 do. (GT) Very fine grained, dark-grayish to greenish-black 

biotite-hornblende quartzplagioclase gneiss and a 

single fragment of finegrained muscovite-quartzfeldspar gneiss.
CRYSTALLINE BASEMENT BENEATH THE NEW JERSEY COASTAL PLAIN AND CONTIGUOUS AREAS B47

Appendix. Selected Coastal Plain wells and seismic stations in New Jersey and contiguous areas that penetrate basement rock— 

Continued

Well

no. Owner or name Latitude Longitude

Elevation

(ft)

Depth to

basement

(ft) Sample type Description Reference

HUDSON COUNTY

105 Holland Tunnel test boring

31.

106 Passaic Valley Sewerage

Commission test boring

#394.

107 Liberty State Park test

boring DB-8.

404345

403930

404220

740200

740400

74 03 30

0

5

5

128 Core (G)

123 do. (G)

39 do. (G)

Serpentinite

Red Mesozoic sandstone

Mica schist

N.J. Geological Survey

permanent notes (1935).

Do.

Tarns Consultants, Inc.

(1988).

NEW YORK WELLS

N 1 People's Pulpit Association

N2 Boulevard Station #1

N3 Hoffman Island

N4 K718

N5 K523

N6 Kl

N7 Q403

N8 Q1030

N9 Brooklyn Union Gas Co.

N10 Q350

Nil Q430

N12 Q568

N13 N5308

403230

403320

403443

403721

403818

403441

403352

403451

403932

404022

404409

404200

403519

74 12 01

74 07 40

74 03 16

74 01 21

735646

73 59 17

735440

735004

734931

735006

73 54 58

734416

73 38 28

150

10

5

139

152

125

5

74

5

78

121

58

8

210 ?

309 ?

450 ?

294 ?

384 ?

625 ?

865 ?

974 ?

651 Cuttings (GT)

577 ?

125 ?

811 ?

1459 ?

"Mica schist"

"Soapstone with mica"

Basement

Basement

Basement

"Granite"

Basement

"Granite" (65% K-feldspar,

25% quartz, 10%

biotite-muscovite, etc.).

Sample at 676 ft is light-grayish-buff-weathering clayey

saprolite containing quartz,

chalky feldspar, trace

graphite, and muscovite and

a grain or two of garnet.

"Mica schist"

"Fordham Gneiss"

"Mica rock"

Basement

Perlmutter and Arnow

(1953).

Do.

Do.

DeLaguna (1948).

Do.

Do.

U.S. Geological Survey,

Syosset, Long Island,

unpub. well record.

Roberts (1948).

Leggette and others (1938).

Do.

Do.

U.S. Geological Survey,

Syosset, Long Island,

unpub. well record.

DELAWARE WELLS

Dl Db 11-27

D2 Db 44-04

D3 DC 5 1-04

D4 DC 52-01

D5 EC 14-07

D6 Eb 23-22

D7 EC 32-7

D8 Eb 44-08

D9 EC 41-10

D10 Fb 33-06

Dll Gd 33-04

39 39 25

39 36 13

39 35 35

39 35 12

393423

39 34 11

39 32 39

39 31 19

393101

39 27 08

39 22 12

754403

75 41 21

75 39 49

75 38 12

75 36 14

75 38 14

75 38 01

75 41 16

75 39 03

75 42 57

75 32 42

_

—

—

—

—

—

—

—

—

—

—

117 ?

340 ?

543 ?

639 ?

755 Cuttings (GT)

670 do. (GT)

741 ?

1160 Core (G,

GT)

1209 ? (G)

1414 ?

2295 Cuttings (GT)

Basement

do.

do.

do.

Chlorite schist

Chlorite schist and

quartzite.

Mica schist

Pyroxenite

Saprolitic green clay

do.

Altered metavolcanic rock

Rasmussen and others

(1957).

Do.

Do.

Delaware Geological

Survey, unpub. well

record.

Delaware Geological

Survey, unpub. well

record; this study.

Rasmussen and others

(1957); Dames and

Moore (1974).

Dames and Moore (1974).

Delaware Geological

Survey, unpub. well

record; Dames and

Moore (1974).

Richards (1945).

Otton and Mandle (1984);

this study.
B48 GEOLOGIC STUDIES IN NEW JERSEY AND EASTERN PENNSYLVANIA

Appendix. Selected Coastal Plain wells and seismic stations in 

New Jersey and contiguous areas that penetrate basement rock— 

Continued

SEISMIC STATIONS

ID3

A 

B

C 

D

E

F 

G

H

I

J

K

L

Location

Charleston Springs 

Lakewood

Cedar Bridge 

Silverton

Lincoln

Pittsgrove 

Elmer

Norma

Millville

Port Elizabeth

Woodbine

Corbin City

Latitude

401136 

400548

400430 

400054

3941 18

393724 

39 35 30

393000

39 26 36

39 21 48

30 14 30

39 19 56

Longitude

742236 

74 15 30

74 12 18 

740806

75 19 30

751206 

75 10 12

750436

745754

745300

744806

744603

Seismic depth 

to basement 

(ft)

1010 

1410

1610 

2210

1200

1540 

2020

2370

3350

3750

4570

4231

'Unpublished water well record on file in the office of the Bureau of Water Allocation, Trenton, N J.

2Wells are not in Coastal Plain but are used for basement surface control.

3A-K from Ewing and others (1939, 1940). L from Robot Sheridan, Rutgers 

University (written comnraa, 1989).
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