regarding the manner in which the materials have been laid down. The
Maryland geologists hold that their three terraces represent three
epochs of submergence, and that the gravels, sands, and clays were
deposited in the salt waters of the ocean or of estuaries. Salisbury and
Knapp (Geol. Surv. New Jersey, vol. VIII, 1917, p. 3) adopt the view
that the formations are partly of subaerial and partly of marine and
estuarine origin, with emphasis on the subaerial mode. Of the Bridgeton,
the authors referred to say (their p. 18 ) that the accessible parts are
primarily of terrestrial origin. A part of what remains may be marine or
estuarine, and part of what has been removed may have been so. No
palæontological evidences of marine deposits of this epoch are found in
the State. The writer records his dissent from the theory that the
terraces and the deposits called the Sunderland, Wicomico, and Talbot
have been the product of marine submergence. A part only of the Talbot
can be referred to deposition in the sea.
Of the Pensauken, Salisbury and Knapp say (p. 87): “There is nothing in
its constitution to negative the hypothesis of the whole formation being
river work; nor is there anything, as now understood, to prove it.” As
to the deposits which they refer to the Cape May, the authors quoted say
(p. 162) that the southern part of the State seems to have stood a few
feet (30 to 50) lower than at present; but that it could not have stood
long at this height, for sea-cliffs are essentially wanting. At one
point, near Millville, Cumberland County, marine fossils are met with at
an elevation of about 10 feet above tide.
The Cape May was, according to Salisbury and Knapp, laid down during the
last glacial epoch, the Wisconsin (p. 162). This determination of age
would doubtless gain the acceptance of the Maryland geologists and their
adherents, although the latter would include under this name many local
deposits which Salisbury puts in the Pensauken.
It is remarkable that, so far as the writer knows, no remains of
Pleistocene vertebrates have ever been discovered in that portion of New
Jersey which is mapped as occupied by the Cohansey sands, an area
including nearly half the State. It lies southeast of a straight line
which would run from Navesink River to Salem. The reason for this lack
of fossil vertebrates does not occur to the writer. A large portion of
this region is mapped as being covered with deposits of all three of the
Pleistocene formations, Bridgeton, Pensauken, and Cape May. On or near
to the line of outcrop of the Cretaceous deposits from Salem to Raritan
Bay, not fewer than ten localities are known where mastodon remains have
been discovered, besides two localities which have furnished horses and
two which have furnished elephants. Since the southeastern part of the
State has yielded no vertebrate fossils and little else to throw light
on the age of its deposits, we shall dismiss it from consideration.
The glacial geology of the State has been studied by Professor Rollin D.
Salisbury, of the University of Chicago, and his assistants, Henry B.
Kümmel, Charles E. Peet, and George N. Knapp. The results of their
studies on the glacial-drift deposits have been published in volume v of
the final report of the State geologist, 1902.
The Quaternary formations of the southern part of the State are
described in volume VIII of the final report. A more succinct
description of the events of the Quaternary period is found in Bulletin
14 (1915) of the New Jersey Survey. The authors are J. Volney Lewis and
Henry B. Kümmel.
In the vicinity of Perth Amboy is a heavy glacial moraine which may be
traced eastward through Staten and Long Islands. West of Perth Amboy it
turns northward, and swinging around it reaches Springfield. Thence it
runs northwestward to Rockaway, and continues west by south to Delaware
River, at Belvidere. This moraine marks, in New Jersey, the southward
limit of the last ice-sheet, the Wisconsin. All the drift deposits of
the State north of this moraine are regarded as belonging to the
Wisconsin stage. It is to be supposed that this is, at least to some
extent, underlain by older drift deposits.
South of the moraine just described are scattered deposits of glacial
drift and other evidence of glacial action which are referred to a much
older ice-sheet, one supposed to correspond to the Kansan drift of the
Mississippi Valley (Salisbury, Geol. Surv. New Jersey, vol. V, p. 781).
On the other hand, it is sometimes referred (Chamberlin and Salisbury,
Geology, vol. III, pp. 383, 384) to the first glacial (sub-Aftonian).
As has been said, three formations are recognized which were laid down
otherwise than by glacial ice-sheets, the Bridgeton, the Pensauken, and
the Cape May. The deposition of the Cape May is regarded as being
contemporaneous with the Wisconsin ice-sheet (Salisbury and Knapp, New
Jersey Geol. Surv., vol. VIII, p. 162; Lewis and Kümmel, Bull. 14, p.
120). The Pensauken formation is believed to be much older than the Cape
May; it may (Salisbury and Knapp, op. cit., p. 78) be older than the
extra-morainic drift, mentioned above as being of about Kansan times;
but it may have coincided in part only with the Kansan. According to
Lewis and Kümmel (op. cit., p. 111) the old, extra-morainic, Jerseyan
drift was coincident with at least the later stages of the Pensauken.
Hence, we may believe that the Pensauken corresponds somewhat to the
Aftonian stage of Iowa. The Bridgeton formation is still older than the
Pensauken and, being Quaternary, must be referred either to the early
part of the first interglacial or to the first glacial; but the New
Jersey geologists are not specific on this point.
It is unfortunate that nowhere in New Jersey has any considerable number
of species of Pleistocene vertebrates been found buried together. We are
thus deprived of one means of estimating the age of the species and of
the beds. Most of the specimens found, as the mastodon and the two
elephants, belong to species which lived during the whole or a large
part of the Pleistocene and hence do not testify definitely to the age
of the deposits in which they occur. Too often the information we have
regarding the place and conditions of burial is extremely meager.
In Salem County a mastodon has been found in Mannington Township, at
Chestnut Hill (p. 63); and a deer, probably _Odocoileus virginianus_, at
Woodstown (p. 226). Although the geological map shows that in Mannington
Township Cape May Pleistocene prevails, while about Woodstown there is
Pensauken, one can not well conclude that the animals are of
corresponding age.
In Gloucester County _Mammut americanum_ has been found at Harrisonville
(p. 63), Mullica Hill (p. 64), and Woodbury (p. 64); _Equus_ at
Swedesboro (p. 184). As to the former species, we can not be certain of
the age, either from our knowledge of the age of the deposits inclosing
the remains or from the history of the species. As to the horse found at
Swedesboro, one may, from the history of the genus in this country,
arrive at some conclusion; but this will be deferred to page 303.
In Camden County, so far as the writer has knowledge, no vertebrate
remains have been found except in the Fish House beds, along Delaware
River, just above Camden; but the horse remains (p. 184) are of great
importance. These beds were originally supposed to be of Cretaceous age,
but in 1869 (Trans. Amer. Philos. Soc., vol. XIV, p. 250), Cope
expressed the conviction that they belonged to the Pliocene period. He
presented a geological section (fig. 7) of the beds which shows a thin
stratum of soil above, then from 8 to 15 feet of light-brown sand,
followed below by a blackish clay about 25 feet in thickness. Near the
bottom of the latter was found a layer containing shells of several
species of _Unio_ and _Anodonta_. Just above this bed of unios there was
discovered a large part of a skull of an extinct horse which Cope
referred to _Equus fraternus_. This was deposited in the collection of
the Academy at Philadelphia, but later disappeared.
[Illustration:
FIG. 7.—Geologic section of Fish House beds, Camden, New Jersey.
Redrawn from Cope.
]
In 1897 (Rep. State Geologist, New Jersey, for 1896, pp. 201–247, plates
X-XIV) Woolman published a paper on the stratigraphy of the Fish House
beds and described and illustrated other horse-teeth which he referred
to _Equus complicatus_. These teeth were found at a depth of 12 feet
below the top of the black clay; 6 feet of surface gravels had been
removed from the clay. The teeth are now in the collection of the
Academy, at Philadelphia. Woolman stated that in the same collection are
a patella and a fragment of a long bone of a horse found in the black
clay, in 1892.
Woolman regarded the clay in question as belonging to Pensauken times.
Salisbury and Knapp (op. cit., p. 104, fig. 49) state that there is here
20 feet of black clay overlying Pensauken sand and that the clay is
overlain by Pensauken gravel. If this judgment of the geological age of
the clay is correct, the horses probably lived during the first
interglacial (Aftonian) or the beginning of the second glacial stage
(Kansan). There are, however, those who insist that these Fish House
clays belong really to the Cape May formation. This would make the
geological age of the horse about that of the Wisconsin drift.
Besides the horse remains, only some bones of a wolf have been found in
the clays mentioned, and these too have disappeared. They probably would
have thrown little light on the age of the beds. We must reach
conclusions from other data.
This fact seems to be pretty certain: Had horses lived at Fish House
during the deposition of the Cape May they would (as did the mastodon,
_Elephas primigenius_, and _E. columbi_) quite certainly have spread out
over northern New Jersey and over the grassy plains of New York and
Ohio; and their remains would somewhere have been found, as are those of
the other species just mentioned, in old swamp and lake deposits
overlying the Wisconsin drift; but no horse remains have ever been
reported from such deposits. Furthermore, in all the digging that has
been done at Trenton, in deposits acknowledged by all to belong to
Wisconsin times, no trace has been found of horse remains.
Near the bottom of the Fish House clay bed, just below the level of the
horse remains, there is found a layer which contains river clams
represented by the genera _Unio_ and _Anodonta_. Ten species of _Unio_
have been recognized and two of _Anodonta_. When these were first
studied the beds were believed to belong to the Cretaceous.
Nevertheless, the close resemblance of the shells to still living
species was recognized; and to them were given names differing from
those of the related existing forms by the ending _oides_. The species
were described by Lea and Whitfield and have been restudied by Dr. H. A.
Pilsbry, of the Academy of Natural Sciences, Philadelphia. The species
are probably identical with forms yet living; but half of them no longer
exist in the region of Delaware River. Pilsbry (Proc. Acad. Nat. Sci.
Phila., 1896, pp. 567–570) stated that five of them have no longer any
representatives in the Atlantic drainage south of the St. Lawrence River
system. It is probable that these species had, when they lived at Fish
House, spread into other rivers south of the Delaware and thus were not
trapped in this river by the Wisconsin ice. It seems certain, therefore,
that a longer period of time and a longer series of vicissitudes must
have intervened to produce such changes in geographical distribution.
According to C. T. Simpson’s work, “Descriptive Catalogue of the
Naiades,” 1914, _Unio (Quadrula) subrotundus_ now inhabits the Ohio,
Cumberland, and Tennessee Rivers; _U. (Lampsilis) anodontoides_ occupies
the Mississippi River and Gulf drainage regions; while _Anodonta
corpulenta_ is found in the Upper Missouri region. The Wisconsin
ice-sheet and the short period of time since its disappearance are
hardly sufficient to explain this wide dispersion of species, while
others have been able to retain their place in the Delaware.
Opposed to this view regarding the identity of the unios of the Fish
House beds, see Ortmann (Proc. Amer. Philos. Soc., vol LII, p. 280,
1913) and Baker (Univ. Ills. Bull., XVII, p. 205, 1920). These writers
contend that the species have no especial relationship to western forms.
According to Baker the deposits are older than the earliest glacial
stage. On the other hand, according to Dr. E. W. Berry (quoted by
Baker), who has studied the plants, the beds belong to the late
Pleistocene.
We have, then, these reasons for holding that the Fish House clays are
of early Pleistocene age: (1) Competent geologists have determined them
as belonging to the Pensauken formation, laid down at or before the time
of the Kansan stage; (2) the presence of remains of horses, evidences of
whose existence during or after the Wisconsin have not been produced;
(3) the presence of many species of naiades, some of which yet live in
that region, but the majority of which now live only in far-distant
regions.
We may confidently conclude that the horse remains which were found at
Swedesboro belonged likewise to the Pensauken.
In Burlington County mastodons have been found at Pemberton ( p. 64),
but one can not be certain of their geological age. A reindeer has been
unearthed at Vincentown (p. 64). It seems highly probable that it lived
there while the Wisconsin ice-sheet occupied the northern part of the
State; but there is a possibility that it is older. In the Academy of
Natural Sciences at Philadelphia are some remains of _Odocoileus_ found
at Vincentown (p. 227).
In the vicinity of Trenton, Mercer County, scant remains of six species
of Pleistocene mammals have been reported. These are _Mammut americanum_
(p. 64), _Elephas primigenius_ (p. 132), Bison bison (p. 287), _Ovibos
moschatus_ (p. 248), _Cervus canadensis_ (p. 237), and _Rangifer
caribou?_ (p. 248). All are known to have existed elsewhere during late
Pleistocene times, and three indicate a cold climate. The presence of
fossil vertebrates here is of special interest because many evidences
have been found of man’s occupation of the region in apparently late
Pleistocene times.
At and in the vicinity of Trenton are found both Pensauken and Cape May
deposits, the latter overlying the former (Salisbury and Knapp, op.
cit., pp. 120, 165). The Cape May rises about 60 feet above sea-level.
At various places the Pensauken protrudes through the mantle of Cape May
and rises to a height of as much as 130 feet above sea-level. Its base
is about 20 feet above sea-level. The materials consist of sand, gravel,
and cobblestones. So far as the writer knows, no fossils have been found
in the Pensauken about Trenton.
The Cape May at Trenton is held to have been laid down principally
during the presence of the Wisconsin ice-sheet in the northern part of
the State; and naturally it consists mostly of sands, gravels, coarse
and fine, and some boulders. In the localities where excavations have
been made for sand and gravel for building purposes, for sewers, and for
railroads, and in search for relics of man, two principal divisions are
recognized. Below are strata of clays, sands, gravels, and boulders
which are believed to have been deposited by the floods of varying
intensity which issued from the glacial moraine then about 60 miles
above Trenton (figs. 8, 9). Over this lies a bed of what is called
yellow drift, which reaches a thickness of about 3 feet. It consists
mostly of fine sand, but there are many pebbles and occasionally some
large boulders. It is everywhere characterized by wavy red bands. While
some geologists have held the opinion that this deposit had been
produced by winds, it appears to be definitely determined that it was
waterlain (Wissler, Scient. Monthly, vol. II, p. 237). This “yellow
drift” is overlain by about a foot of black soil which belongs to the
Recent epoch and is the result of cultivation by whites. For details
regarding the Trenton gravels and the yellow sands above it the reader
should consult Ernest Volk’s work, “Archæology of the Delaware Valley”
(Papers Peabody Mus., vol. V, 1911).
All the species mentioned above have been reported from the beds known
as the Trenton gravels. A femur of a bison was found also in the yellow
drift (see p. 287).
Monmouth County has furnished more fossil vertebrates of the Pleistocene
than any other county. Mastodons have been discovered at Englishtown,
Freehold, Marlboro, Long Branch, Manasquan, and in the Navesink Hills
(pp. 65, 66). Many specimens, as those about Freehold and Long Branch
and Manasquan, are in such superficial positions in peat that they do
not seem to be very old, probably of Cape May age; and yet of this one
can not be wholly certain. The discovery of a heel-bone of a megatherium
(p. 31) at Long Branch appears to indicate the presence there of early
Pleistocene deposits. At Englishtown the remains had apparently become
mixed with marl, and they may belong to an older stage of the
Pleistocene. In the Navesink Hills, according to Leidy, the mastodon
remains were associated with those of an extinct horse (p. 184). If so,
both species probably were buried in Pensauken deposits. In this same
region there was found long ago a tooth of _Elephas columbi_ (p. 149);
but it is useless to speculate on its geological age. At Long Branch (p.
26), damaged skulls of walruses, probably of the existing species, have
been met with. It seems natural to associate this southward migration,
which extends to South Carolina, with the Wisconsin epoch; but it is
possible that it was earlier. At Deal (p. 227) have been found remains
of a deer, probably _Odocoileus virginianus_.
[Illustration:
FIG. 8.—Sketch of vicinity of Trenton, showing distribution of Trenton
gravels. Redrawn from Salisbury and Knapp.
]
[Illustration:
FIG. 9.—Sections taken at Trenton, New Jersey.
Upper figure taken along the line 3 of Fig. 8.
Lower figure taken along the line 2 of Fig. 8.
The black represents the glacial gravel. A, the crystalline rock of
the region; T, Trias; K, Cretaceous; Pp, Pensauken; O, sea-level.
]
Somewhere about Shark River, a tooth of a peccary (p. 213) was found, as
was supposed, in Miocene marl. Leidy could not distinguish this tooth
from that of _Mylohyus nasutus_. So far as our evidence goes, this
species belongs to the early and middle Pleistocene.
Near North Plainfield a tooth was found which is referred to _Elephas
primigenius_ (p. 133). The locality is very close to the moraine of the
Wisconsin ice-sheet, and the animal probably lived there when the
Plainfield outwash plain (Salisbury, Geol. Surv. New Jersey, vol. V,
1902, p. 738) was being laid down.
Near Schooley’s Mountain, but west of Musconetcong River and in Warren
County, remains of a mastodon (p. 67) were encountered in excavating the
Morris Canal. It is probable that these were buried in a swamp left over
from the Wisconsin times; but Lewis and Kümmel’s map of 1910–1912
indicate in this region only drift older than the Wisconsin.
The mastodons found at Hackettstown and Hope, in Warren County, are
probably of Late Wisconsin origin (pp. 67, 68).
Near Mount Hermon, about 5 miles northeast from Delaware, in Warren
County, and about 2 miles northwest of Hope, was found the splendid
skeleton of the moose _Cervalces scotti_, which forms one of the
treasures of Princeton University (Scott, Proc. Acad. Nat. Sci. Phila.,
1885, p. 174). It was discovered in a bog. All this region is
(Salisbury, Geol. Surv. New Jersey, vol. VIII, plate XXVIII) occupied by
Wisconsin drift and the bog doubtless rested on this drift. It seems
certain, therefore, that this stately relative of our existing moose
lived after the disappearance of the Wisconsin ice-sheet.
A mastodon (p. 68) which was found at Greendell in Sussex County quite
certainly lived there after the last glacial stage.
Berry (Torreya, vol. X, p. 261) has studied a collection of nine species
of plants which had been obtained in peat from near Long Branch. Only
three of these now range north of Long Branch. He concluded that the
last glacial stage had been followed by a period of climate warmer than
the present climate. This is in accord with views which the present
writer has held. It ought not, however, to be assumed with too much
confidence that the peat-bed is of Late Wisconsin origin.
PENNSYLVANIA.
About half of the area of Pennsylvania lies outside of the region which
was glaciated. Figure 10 is a map taken from Folio 172 of the U. S.
Geological Survey, published in 1910 and compiled by Dr. W. C. Alden in
1901. A broad strip along the southern part of the State, being
non-glaciated, is not represented. The areas shaded by parallel ruling
and stippling are those which present evidences of glacial action.
The glaciated area consists of two principal portions. One of these,
that subjected to the action of the Wisconsin ice-sheet, is represented
on the map by means of oblique parallel lines coming down to an
interrupted heavy line. This line, representing the Wisconsin terminal
moraine, starts on Delaware River north of Easton, runs northwestward to
Potter County, thence into New York, thence back into Pennsylvania, in
Warren County, and then enters Ohio north of the Ohio River. The course
of this moraine was worked out especially by H. C. Lewis and G. F.
Wright and was described in report L of the Pennsylvania Geological
Survey, in 1881. The moraine crosses the Delaware at Belvidere, New
Jersey, and passes through the following counties: Northampton, Monroe,
Carbon, Luzerne, Columbia, Sullivan, Lycoming, Tioga, Potter, Warren,
Crawford, Venango, Butler, Lawrence, and Beaver.
South of this moraine are two areas which, on this map, are represented
by stippling. These are occupied by drift materials, usually forming a
considerably thinner covering, which are believed by most glaciologists
to belong to an older Pleistocene stage, probably about as old as the
Kansan. Especially in the valleys these older drift deposits may reach
thicknesses of 200 or 300 feet. These old glacial deposits are
represented also by terraces along the margins of the valleys. Some of
these in the vicinity of Warren stand at a height of about 1,400 feet
above the sea. Figure 17 is taken from Shaw and Munn (Folio 178, U. S.
Geol. Surv., p. 12). The uppermost gravels are supposed to represent the
Kansan stage. A few small patches lying in the angle of the unglaciated
area are of doubtful age, as indicated on the map. It must be stated,
however, that there is some dissent from this conclusion as to the age
of this outer drift. Professor E. H. Williams has published a number of
papers in which he takes the position that this drift is a deposit laid
down by the same ice-sheet that later on built up the Wisconsin moraine
(Amer. Jour. Sci., vol. XLVII, 1894, pp. 32–36; Science (n. s.), vol.
XXXVII, pp. 447–450; Pennsylvanian Glaciation, first phase, 1917, pp.
1–101). Professor G. F. Wright appears to take the same view. The writer
sees no sufficient reason for distrusting the opinions of Dr. Alden and
his colleagues.