TRIASSIC AND JURASSIC FORMATIONS OF THE NEWARK BASIN

 

 

TRIASSIC AND JURASSIC
FORMATIONS OF THE NEWARK BASIN

PAUL E. OLSEN

Bingham Laboratories, Department of Biology, Yale University,
New Haven, Connecticut

Abstract

Newark Supergroup deposits of the Newark Basin
(New York, New Jersey and Pennsylvania) are divided
into nine formations called (from bottom up): Stockton
Formation (maximum 1800 m); Lockatong Formation
(maximum 1 150 m); Passaic Formation (maximum 6000
m); Orange Mountain Basalt (maximum 200 m);
Feltville Formation (maximum 600 m); Preakness
Basalt (maximum + 300 m); Towaco Formation (max-
imum 340 m); Hook Mountain Basalt (maximum 110
m); and Boonton Formation (maximum + 500 m). Each
formation is characterized by its own suite of rock
types, the differences being especially obvious in the
number, thickness, and nature of their gray and black
sedimentary cycles (or lack thereof).

Fossils are abundant in the sedimentary formations of
the Newark Basin and provide a means of correlating
the sequence with other early Mesozoic areas. The
Stockton, Lockatong, and most of the Passaic Forma-
tion are Late Triassic (?Middle and Late Carnian-
Rhaetic) while the uppermost Passaic Formation (at
least locally) and younger beds appear to be Early
(Hettangian and Sinemurian) in age. The
Jurassic
distribution of kinds of fossils is intimately related to se-
quences of rock types in sedimentary cycles.

INTRODUCTION

Far from being the consequence of the last gasps of
the Appalachian Orogeny, Late Triassic and Early
Jurassic Newark Supergroup basins formed in dynamic
association with the opening of the Atlantic Ocean
(Sanders, 1974; Van Houten 1977; Manspeizer,Puffer,
and Cousminer, 1978; Olsen, 1978). In addition,
Newark Supergroup rocks, once thought to be nearly
barren of fossils, are now known to be exceptionally
rich in organic remains (Thomson, 1979), replete with
plants, invertebrates, and vertebrates spanning some 35
million years of the Early Mesozoic (Cornet, 1977).
Finally,
long episodes of unusually continuous
deposition coupled with an abundance of laterally
extensive stratigraphic “marker” beds (McLaughin,

1946), makes this deposit ideal for studying time-facies
relationships and evolutionary phenomena. These
recent discoveries have focused new interest on Newark
strata.

The Newark Basin (Fig. 1 and 2) is the largest of the
exposed divisions of the Newark Supergroup, covering
about 7770 km2 and stretching 220 km along its long
axis. The basin contains the thickest sedimentary se-
quence of any exposed Newark Supergroup basin and
correspondingly covers the greatest continuous amount
of time. Thus, the Newark Basin occupies a central posi-
tion in the study of the Newark Supergroup as a whole.

–

In well over a century of study the strata of Newark
Basin have received a relatively large amount of atten-
tion. By 1840, the basic map relations were worked out
(Rogers, 1839, 1840, Cook, 1868) and by 1898, the ma-
jor rock-stratigraphic subdivisions of the basin section
were delimited and named (Darton, 1890; Kiimmel,
1897, 1898). Despite this long tradition, fundamental
aspects of its historical and structural geology have re-
mained essentially unexplored. The lithostratigraphy of
the younger sediments, in particular, has received short
shrift. Recently I have revised certain aspects of Newark
Basin stratigraphy with an emphasis on the younger
rocks (Olsen, in press). In the process I haveproposed a
number of new formational names (Table 2). Here I will
review the formations of the Newark Basin and attempt
to place their broader lithostratigraphic features into
biostratigraphic context.

OVERVIEW OF NEWARK BASIN FORMATIONS

As currently defined (Olsen, 1978; Van Houten, 1977;
Cornet, 1977), the Newark Supergroup consists of
predominantly red elastics and volumetrically minor
basaltic igneous rocks exposed in 13 major and 7 minor
in the Piedmont, New
elongate basins preserved
England, and Maritime physiographic provinces of
eastern North America (Figure 1, Table 1). In general,
the long axes of these basins parallel the fabric of the

In W. Manspeizer (ed.), 1980, Field Studies in New Jersey Geology and Guide to Field Trips, 52nd Ann. Mtg. New
York State Geological Assoc.iation, Newark College of Arts and Sciences, Newark, Rutgers University, p. 2-39.

3

FIELD STUDIES OF NEW JERSEY GEOLOGY AND GUIDE TO FIELD TRIPS

0
l

(krn)

SCALE

– EXPOSED

~

~

*

l

CS=3>

INFERRED

800
l

‘

.

l

Fig. 1

Newark Supergroup of eastern North America. Key to
numbers given in Table 1 . The Newark Basin is 1 1 . Data
from Olsen, 1978.

TRIASSIC AND JURASSIC FORMATIONS O F THE NEWARK BASIN

Fig. 2
A.

The Newark Basin.
Geologic map showing distribution of formations,
conglomeritic facies (irregular stipple), and major clusters
of detrital cycles in Passaic Formation (parallel black lines)
— abbreviations of formations and diabase bodies as
follows: 9 , Boonton Formation; C, Coffman Hill Diabase;
Cd, Cushetunk Mountain Diabase; F, Feltville Formation;
H, Hook Mountain Basalt; Hd, Haycock Mountain
Diabase; Jb, Jacksonwald Basalt; L, Lockatong
Formation; 0, Orange Mountain Basalt; P, Passaic
Formation; Pb, Preakness Basalt; Pd, Palisade Diabase;
Pk, Perkasie Member of Passaic Formation; Rd, Rocky
Hill Diabase; S, Stockton Formation; Sc, carbonate Facies
of Stockton Formation; Sd, Sourland Mountain Diabase;
T, Towaco Formation.

B.

Structural features of the Newark Basin. Faults are all
drawn as normal with dots on the down-thrown side;
portions of basin margin not mapped as faults should be
regarded as onlaps. While all the faults are mapped here as

Appalachian Orogene (Rodgers, 1970; Van Houten,
1977). The rocks of these basins present a relatively
unified lithology and structure and unconformably
overlie (or intrude) Precambrian and Palaeozoic rocks.
They are in turn overlain by post-Jurassic rocks of the
Coastal Plain, Pleistocene deposits or Recent alluvium
and soils. In addition, early Mesozoic red clastics,
basaltic volcanics, and evaporites at the base of some se-
quences on the continental shelf and also at least 12
units recognized beneath the Atlantic Coastal Plain pro-
bably should be grouped in the Newark Supergroup
(Figure 1).

Precambrian and early Paleaozoic rocks of the
southwestern prongs o f the New England Upland

normal, it is clear many, if not all of them, have some
component of strike slip, although the significance of this
component is unclear. Symbols for the names of structural
features used in this paper are as follows: A, Montgomery-
Chester fault block; B, Bucks-Hunterdon fault block; C,
Sourland Mountain fault block; D, Watchung syncline; E,
New Germantown syncline; F, Flemington syncline; G,
Sand Brook syncline; H, Jacksonwald syncline; I, Ramapo
fault; J, braided connectoin between Ramapo and
Hopewell faults; K, Flemington fault; L, Chalfont fault;
M, Hopewell fault.

Data for A and B from Kimmel, 1897; Lewis and Kimmel,
1910-1912; Darton, 1890, 1902; Darton, et a]., 1908;
Glaeser, 1963; Sanders, 1962; Van Houten, 1969;
McLaughlin, 1941, 1943, 1944, 1945, 1946a, 1946b;
Bascom, et at., 1909; Willard, et al., 1959; Faille, 1963;
Manspeizer, pers. comm.; Olsen, in press, and personal
observation.

border the Newark Basin along its northeast and north-
west margins (Figure 2). The southeastern and
southwestern portions of the Newark Basin overlie and
are bordered by Palaeozoic and Precambrian rocks of
the Blue Ridge and Piedmont Provinces. Newark Basin
sediments rest with a profound unconformity on base-
ment rocks and mostly dip 5 Â – 25’ to the northwest.
The entire stratigraphic column reaches a cumulative
trigonometrically calculated thickness of over 10,300 m
(the sum of the maximum thicknesses of all the forma-
tions), although the total thickness of sediments actually
deposited at any one spot was probably much less. Red
clastics are the dominant sediments; intrusive and ex-
trusive tholeiites are the dominant igneous rocks. The
oldest sediments are probably middle Carnian (early

5

FIELD STUDIES OF NEW JERSEY GEOLOGY AND GUIDE TO FIELD TRIPS

Key t o
F i g u r e 11

R o c k – s t r a t i g r a p h i c t e r m

Bas i n name

Age r a n g e

Chatham Group

Deep R i v e r B a s i n

C a r n i a n – ?Nor i a n
( L a t e T r i a s s i c )

T a b l e 1

I

u n d i f f e r e n t i a t e d

Davie County B a s i n

L a t e T r i a s s i c

u n d i f f e r e n t i a t e d

F a r m v i l l e B a s i n

‘ C a r n i a n
T r i a s s i c )

( L a t e

u n d i f f e r e n t i a t e d

I Dan R i v e r Group

4 s m a l l b a s i n s s o u t h
o f F a r m v i l l e B a s i n

‘PCarnian ( L a t e
T r i a s s i c )

Dan R i v e r a n d D a n v i l l e
Bas i n s

C a r n i a n – ‘;Norian
( L a t e T r i a s s i c )

Tuckahoe a n d
C h e s t e r f i e l d Groups

Richmond B a s i n a n d
s u b s i d i a r y b a s i n s

C a r n i a n ( L a t e
T r i a s s i c )

none

C u l p e p e r B a s i n

T a y l o r s v i l l e B a s i n

9

u n d i f f e r e n t i a t e d

S c o t t s v i l l e B a s i n and
2 s u b s i d i a r y b a s i n s

? L a t e T r i a s s i c –
E a r l y J u r a s s i c

1 0

none

G e t t y s b u r g B a s i n

11

none

Newark B a s i n

12

none

Pomperaug Bas i n

1 3

none

H a r t f o r d B a s i n and
s u b s i d i a r y C h e r r y
Brook B a s i n

14

none

D e e r f i e l d B a s i n

1 5

Fundy Group

Fundy B a s i n

Chedabucto Format i o n
( = E u r y d i c e Format i o n ? )

Chedabucto B a s i n
(=Orpheus B a s i n ? )

? L a t e T r i a s s i c –
E a r l y J u r a s s i c

N o r i a n – PSinemurian
( L a t e T r i a s s i c –
E a r l y J u r a s s i c )

C a r n i a n ( L a t e
T r i a s s i c )

C a r n i a n – H e t t a n g i a n
( L a t e T r i a s s i c –
E a r l y J u r a s s i c )

C a r n i a n . S i n e m u r i a n
( L a t e T r i a s s i c –
E a r l y J u r a s s i c )

? L a t e T r i a s s i c –
E a r l y J u r a s s i c

N o r i a n – ? B a j o c i a n
( L a t e T r i a s s i c –
?Middle J u r a s s i c )

? N o r i a n – P T o a r c i a n
( L a t e T r i a s s i c –
E a r l y J u r a s s i c )

?Middle T r i a s s i c –
E a r l y J u r a s s i c

1

2

3

4

6

7

1

1

1
1

TRIASSIC AND JURASSIC FORMATIONS OF THE NEWARK BASIN

Lyman, 1895

Kummel, 1897;
Darton, 1890

American New Red Sandstone

Newark System
(of Newark Basin)

Newark System
(of Newark Basin)

Table 2

Baird and Take,
1959; Baird, 1964;
Colbert, 1965

(Olsen, in press)
This Article

Newark Supergroup
(of Newark Basin)

Boonton Formation

Brunswick Formation

Boonton and Whitehall
Beds

‘3rd” Watchung Basalt

Hook Mountain Basalt

Hook Mountain Basalt

Brunswick Formation

Brunswick Formation

Towaco Formation

“2nd” Watchung Basalt

“2nd” Watchung Basalt

Preakness Basalt

Brunswick Formation

Brunswick Formation

Feltville Formation

‘1st” Watchung Basalt

“1st” Watchung Basalt

Orange Mountain Basalt

Brunswick Formation

Brunswick Formation

Passaic Formation

Pottstown Shales
Perkasie Shales
Lansdale Shales

Gwynedd Shales

Lockatong Formation

Lockatong Formation

Lockatong Formation

Norristown Shales

Stockton Formation

Stockton Formation

Stockton Formation

Late Triassic) in age while the youngest appear to be
Sinemurian (middle Early Jurassic) (Cornet, 1977;
Olsen, McCune, and Thomson, in press). Cretaceous
and younger Coastal Plain deposits overlap Newark
beds with an angular unconformity along the basin’s
eastern edge. The northern quarter of the basin is
mantled by Pleistocene and recent deposits.

The first lithostratigraphic terms for the sedimentary
formations of the Newark Basin were introduced by
Lyman in 1895 (Table 2). Although he clearly demar-
cated the units in their type areas (southeastern Penn-
sylvania), mapped and briefly described them, his terms
never gained wide acceptance. In 1897, Kiimmel in-
troduced his own nomenclature for equivalent rocks in
New Jersey (Table 2). Since their introduction, Klim-
mel’s terms have been widely used. While the rule of
priority applies to stratigraphic names, no practical pur-
pose is served by resurrecting those of Lyman. This is in
accordance with Code of Stratigraphic Nomenclature,
1961 (hereafter C. N. S.), article 1 lb, and with the Inter-
national Stratigraphic Guide, 1976 (hereafter I. S. G.),

I chapter 3e.

Kiimmel (1897) divided the Newark Basin sequence
into three formations: Stockton, Lockatong, and
Brunswick. The Stockton Formation (maximum
thickness ca. 1800 m) consists of thick beds of buff or
cream colored conglomerate and sandstone and red
siltstone and sandstone forming the basal formation of
the Newark Basin. Throughout the exposed central por-
tion of the Newark Basin, the Stockton Formation is

overlain by
the Lockatong Formation (maximum
thickness 1150 m) which is made up of beds of gray and
black siltstone. These siltstones are arranged, as Van
Houten (1969) later showed, in distinctive sedimentary
cycles. The youngest formation KUmmel recognized is
the Brunswick. Throughout the Newark Basin, the
lower half of this formation consists mostly of red
siltstone, sandstone, and conglomerate with clusters of
laterally persistent cycles of gray and black siltstone
similar to that in the Lockatong Formation (Kiimmel,
1897,1898; McLaughlin, 1943; Van Houten, 1969). The
upper Brunswick, on the other hand, is made up of
three major, multiple-flow, basalt sheets (units Darton
in 1890 called the Watchung Basalts), two major in-
terbedded sedimentary units, and a thick overlying
sedimentary unit. The latter sedimentary sequences have
escaped even preliminary lithologic description.

Field work by myself and others (Olsen, in press) has
shown that Kummel’s Brunswick Formation consists of
a heterogeneous mix of major, mappable units of differ-
ing and distinctive lithology, each as distinct and
perhaps originally as widespread as the Stockton or
Lockatong; “Watchung Basalt” and the interbedded
and overlying sedimentary beds are lithologically
distinct from the stratigraphically older beds. In addi-
tion, Kummel’s upper Brunswick is Early Jurassic,
rather than Late Triassic as most authors have assumed
(Cornet, Traverse and McDonald, 1973; Cornet and
Traverse, 1975; Cornet, 1977; Olsen and Galton, 1977;
Olsen, McCune, and Thomson, in press). It now seems
that these Jurassic rocks are in many ways different

7

FIELD STUDIES OF NEW JERSEY GEOLOGY AND GUIDE TO FIELD TRIPS

from the Late Triassic lower Brunswick Formation,
Lockatong, or Stockton formations.

I have proposed elsewhere (Olsen, in press) that the
terms Brunswick Formation (Kiimmel, 1897) and Wat-
chung Basalts (Darton, 1890) be dropped and their com-
ponents subdivided to form seven new formations.
Despite the wide (although inconsistent) use of those
terms over the years, it is inappropriate to conserve
them for the following reasons:

1. The division of the Brunswick Formation of Kum-
me1 into four sedimentary formations constitutes a ma-
jor redefinition of the unit. C.S.N. article 14b recom-
mends that “When a unit is divided into two or more of
the same rank as the original, the original name should
not be employed for any of the revisions.” Thus, while
it could be argued that the term Brunswick Formation
should be retained for the pre-basalt sediments of the
Newark Basin, such use could be a source of confusion,
and it seems better to establish a new term for the pre-
basalt, post-Lockatong beds.

2. Darton’s Watchung Basalt has been traditionally
recognized as a single formation embracing the three
major multiple flow units interbedded in Kiimmel’s
upper Brunswick Formation (see,
for example,
Wilmarth, 1938, p. 896; Faust, 1975, 1978; Van
Houten, 1969, p. 327). Since both the C.S.N. (article
lOh) and the I.S.G. (chapter 5f, 1c) state that repetition
of geographic names in formations is considered
informal nomenclature, it is appropriate to drop the
formal use of the term Watchung Basalt and recognize
three basalt formations with individual names (Table 2).

The new formational names I have proposed to
replace Kummel’s and Darton’s formations are (from
the bottom up): Passaic Formation, Orange Mountain
Basalt, Feltville Formation, Preakness Basalt, Towaco
Formation, Hook Mountain Basalt, and Boonton
Formation. These new divisions of the Newark Basin
section are similar in scale to Emerson’s (1898) and
Lehman’s (1959) widely used divisions of the Hartford
Basin and Klein’s (1962) divisions of theFundy Group,
and are in accordance with the letter and intent of the
C.S.N. and I.S.G. In this way, formal names are given
to beds critical to the overall pattern of Newark Basin
historical geology.

A NOTE ON THE CALCULATION
STRATIGRAPHIC THICKNESS

OF

The arguments which center on the accuracy of
trigonometrically computed stratigraphic thicknesses of
Newark Basin sections (Rogers, 1840, 1865; Kummel,
1898; Faill, 1973; Faust, 1975; Sanders, MS) concern
two components. First, deposition along the stepfaulted
northwest margin decreases the real thickness of beds

preserved at any one place. This is a major concern, but
the problem can beat least partially resolved by careful
analysis of existing outcrops and geophysical data (see
Faill, 1973, for a review and Dunleavy, 1975, and Olsen,
in press, for particulars) (see Figure 5). Second, there
are a large number of hidden strike faults with large dip-
slip components. This problem has no clear quantitative
solution in some important areas. In parts of the
Newark Basin, such as the entire northern third of the
basin, this is a substantial problem, as the following
examples show (Figure 2).

1. A suite of faults has long been known to offset the
northern segments of the Watchung ridges (Kummel,
1897; Darton, et al., 1908; Olsen, in press). These series
cut the type sections of both the Orange Mountain
Basalt and the Preakness Basalt. 2. Another suite of
faults cuts the Palisades ridge, especially in the area of
Weehawken and Edgewater, New Jersey (Kiimmel,
1898; Van Houten, 1969; Olsen, in press). 3. Faults
duplicate 30 % of the exposed Lockatong Formation at
Gwynned, Pennsylvania (Watson, 1958). Many other
examples are know (Willard, et al., 1959; Rima,
Meisler, and Longwill, 1962).

Most of these faults are visible because they cut ridges
with topographically expressed offsets; in areas of low
topography, they do not show up. In certain areas, such
as the Passaic Formation type section (Figure 6), the
distribution of
such faults is essentially unknown.
Those faults presently mapped which cut the Watchung
the Passaic
ridges must continue and cut
Formation,though they may eventually die out. Thus,
the
thickness for the
Passaic Formation in the northern third of the Newark
Basin is certainly an overestimation.

trigonometrically computed

In contrast, the field relationships of mapped gray
and black siltstone and conglomerate beds in the Bucks-
Hunterdon fault block (see Figure 2) show that these
small strike faults are absent over broad areas. In these
areas the trigonometrically computed thicknesses have
been confirmed by some deep well records (Lesley,
1891; McLaughlin, 1943). This inconsistency over parts
of the Newark Basin demonstrates that there can be no
single constant to correct for “hidden faults.” Rather,
if a correction is attempted (as in Figure 6) it must be
based on extrapolation of the local fault patterns. For
thin units, such as the northern outcrops of the
Lockatong or the basalt formations, these small faults
usually do not present much of a problem sinccthere are
single outcrops covering much of each unit.

As a general guide, I place most confidence in
thickness determinations in the Bucks-Hunterdon Block
and the least confidence in the calculated thicknesses at
the northeastern and southwestern portions of the

TRIASSIC AND JURASSIC FORMATIONS OF THE NEWARK BA SIN

8

Newark Basin.

STOCKTON FORMATION

the

Jersey,

is 1500 m

The Stockton Formation is the poorest known of all
Newark Basin formations. It is also the oldest and most
widespread deposit, forming the basal beds of the
Newark Basin section everywhere except along portions
of the northwest border.The Stockton is thickest near
the Bucks-Montgomery county line in the Bucks-
Hunterdon fault block (Figure 2), where it reaches a
calculated stratigraphic thickness of 1830 m (Willard, et
al., 1959). Along its type section (Figure 3, Table 3)
along the shores of the Delaware River near Stockton,
thick
formation
New
(McLaughlin, 1945). Measured from the base of the
lowest continuous black siltstone unit of the overlying
Lockatong Formation, the Stockton thins in all direc-
tions from this central area (Kiimmel, 1897). Towards
the south at Norristown, Pennsylvania it is 1221 m and
at Phoenixville, Pennsylvania it is 700 m; to the north
near Clinton, New Jersey it is 1350 m; to the east near
Princeton, New Jersey it is 920 m; and to the northeast
at Hoboken and Weehawken, New Jersey it is less than
250 m. The predeformational shape of the Stockton
Formation lithosome is thus an asymmetrical lens with
the thickest portion near the center of the Bucks-
Hunterdon fault block (see Figure 4). McLaughlin (in
Willard, et al., 1959) presents evidence that the
Stockton Formation in the southern Newark Basin thins
by a progressive onlap of younger Stockton beds onto
basement.

Stockton lithology is diverse. The dominant sediment
types are gray and buff colored arkose and arkosic con-
glomerate, and red siltstone and arkosic sandstone. In
broad view, the Stockton Formation fines upward with
the coarsest sediments near the base. As noted by
McLaughlin (In Willard, et al., 1959) the Stockton
coarsens in the same directions it thins; thus con-
glomerate bodies and coarse arkose are found high in
the section along the eastern edge of the basin.

The belt of Stockton Formation which runs through
the Bucks-Hunterdon fault block and through the
Montgomery-Chester fault block (Figure 2) has been
divided into members by McLaughlin (In Willard et al.,
1959) and by Rima, Meisler and Longwill (1962),
primarily on the basis of texture (Table 3).They did not
attempt to extend these member names into other parts
of the Newark Basin. Upper Stockton fissile red sand-
stone and siltstone pass upwards into hard non-fissile
red siltstones (argillite) in the Bucks-Hunterdon belt.
These siltstones have been grouped with the overlying
Lockatong Formation by a number of authors
(McLaughlin, 1945; McLaughlin, In Willard et al.,
1959; Van Houten, 1969). I believe the Stockton-

Lockatong boundary should be defined at the base of
the lowest continuous black siltstone bed. This is in ac-
cord with Kiimmel’s own definition which does not
seem to include 30 m of red beds at the base of the
Lockatong, although I think his definition is somewhat
vague. I group these red siltstones with the Stockton.

While the predominant facies trend is clearly upward
fining, important beds of different lithology occur
throughout. Basal Stockton beds, where they are expos-
ed, rest on a locally .irregular surface. Where basal
Stockton beds rest on Cambro-Ordovician limestones,
red matrix limestone breccia and red siltstone fill ap-
parent solution cavities. Elsewhere, there are basal red-
matrix conglomerate and breccia composed of underly-
ing basement rocks (Olsen, in press). The main masses
of Stockton Formation conglomerate in the central part
of the basin, however, are definitely not basal and rest
some 100 m above the base of the formation. These con-
glomerates are gray and buff, but are never red (Rima,
Miesler, and Longwill, 1962; McLaughlin in Willard, et
al. 1959).

Red siltstones of

the Stockton Formation are
characteristically intensively bioturbated by roots and
burrows, notably the arthropod burrow Scoyenia (see
Olsen, 1977). Purple and mauve siltstone beds with a
markedly disrupted fabric occur near the middle and
top of the formation. These beds are usually densely
penetrated by roots, but rarely burrowed by Scoyenia.
Beds of greenish-gray and brown carbonate-rich pellets
occur throughout the formation. These are often
associated with bases of buff arkose beds. Well-bedded
gray and gray-green siltstone beds are present locally in
the upper Stockton, and these beds are the source of
most of the Stockton fossils found so far. How these
units, which are unusual compared to the bulk of the
Stockton sequence, fit in the overall facies pattern re-
mains obscure.

LOCKATONG FORMATION

The beds of the Lockatong Formation rest confor-
mably on the Stockton Formation over most of the
Newark Basin. The Lockatong is composed primarily of
gray and black siltstones arranged, as shown by Van
Houten (1962, 1964, 1965, 1969, 1977), in sedimentary
cycles. In the Bucks-Hunterdon fault block, near the
Lockatong’s type section along Lockatong Creek, the
formation reaches its maximum thickness of 1150 m
(Figure 2, Table 4). The formation thins in all direc-
tions away from this central area, passing into Passaic
and Stockton formations along exposed edges of the
Newark Basin.

Van Houten (1962, 1964a,b, 1965, 1969, 1977)
recognizes two end-members to the range of short cycle

9

FIELD STUDIES OF NEW JERSEY GEOLOGY AND GUIDE TO FIELD TRIPS

Fig. 3 Geographic map of Newark Basin showing locations of
type sections of formations: a, type section of Passaic
Formation; b, type section of Orange Mountain Basalt; c,
type section of Feltville Formation; d, type section of
Preakness Mountain Basalt; e, type section of Towaco
Formation in Roseland, New Jersey; f, type section of
Hook Mountain Basalt in Pine Brook, New Jersey; g, type
section of Boonton Formation, Boonton, New Jersey; h,
type section of Lockatong Formation along both shores of
the Delaware River north of Stockton, New Jersey; i, type
section of Stockton Formation near Stockton, New Jersey
just south of the type section of the Lockatong.

I

types present in the Lockatong; he terms these detrital
and chemical. In the Delaware River section of the for-
mation the detrital cycles are an average of 5.2 m thick
and consist of a lower platy black calcareous siltstone
succeeded upwards by beds of disrupted dark gray,
calcareous siltstone, ripple-bedded siltstone, and fine
sandstone. In the same area, chemical cycles average 3.2
m thick. Their lower beds consist of platy black and
dark gray dolomitic siltstone, broken by shrinkage
cracks, and containing lenses of pyritic limestone. The
upper beds are massive gray or red analcime- and
carbonate-rich siltstone,
intensively and minutely
disrupted. The massive beds often contain pseudo-
morphs after analcime and glauberite.

Detrital and chemical cycles are not distributed ran-
domly through the Lockatong. In vertical section, in the
central Newark Basin, the two cycle types occur in

clusters; the center of each detrital cycle cluster is about
107 m from the next. Detrital cycle clusters are
separated by clusters of chemical cycles. Again, in ver-
tical section, there are more detrital cycles in the lower
than in the upper Lockatong. Evidence gathered so far
(Olsen, this Fieldbook) indicates that individual detrital
cycles can be traced for over 20 km. Judging from the
outcrop pattern of detrital cycle clusters in the upper
Lockatong and lower Passaic Formation, it seems likely
that individual detrital cycles can be traced basin-wide.
Chemical cycles, on the other hand, are predominantly
restricted to the central 97 km of the Newark Basin,
passing laterally into beds indistinguishable from the
Stockton and Passaic formations. At the southwestern
end of the Newark Basin at Phoenixville, Pennsylvania,
the Lockatong is 350 m thick; the formation consists of
clusters of detrital cycles separated by red siltstone and
some beds of gray sandstone. At the northeastern end of