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.
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.