The writer has already (p. [346]) expressed his opinion regarding the Coastal Plain terraces found in the States farther north. He finds in Florida nothing to contradict, but much to confirm, that opinion. Whatever may be the origin of Newberry and Tsala Apopka terraces, they were not laid down in salt water. From the descriptions of the deposits there the stratification and the alternation of the materials do not exist that one might expect; but, above all, there seem to be no marine fossils to attest to the presence of the sea. In Florida, too, here and there over these higher lands there are found, in place of marine fossils, the remains of many extinct land animals, as mastodons, elephants, horses, ground-sloths, and the like.
As regards the Pensacola terrace, there are found at its base, within a few feet above or below sea-level, deposits containing remains of such animals as have just been mentioned, besides many others. Often the state of preservation of these remains and the condition of their burial are such that we must conclude that the animals lived and died on the spot. Furthermore, these animals constitute an assemblage corresponding to that found in western Iowa, in Nebraska, and in Oregon, which are believed to have existed during the first interglacial stage. It corresponds also to that met with under similar conditions and at the same level at Savannah, at Charleston, at Brunswick, and at Long Branch. In most cases, too, this fossiliferous stratum is overlain with very scant deposits. By some geologists and palæontologists the animals are regarded as belonging to the Pliocene.
If the reference of the fossil vertebrates mentioned is not wholly wrong, it follows that the lowest terrace or plain along the coast was not laid down late in the Pleistocene, but at an early stage, and the higher plains must have been formed at still earlier times.
At Vero, as will be shown on page [382], a large assemblage of fossil vertebrates has been secured. The bed furnishing the oldest fossils, those of the bed known as No. 2 and believed to be of about first interglacial age, is underlain by a bed of marine shells, also of Pleistocene age. This bed is regarded by Dr. E. H. Sellards as being equivalent to the coquina which is so well known at St. Augustine; and the same formation is found here and there along both coasts of the peninsula (Matson and Sanford, op. cit., p. 192). Probably not all deposits that are called coquina are of the same age, but the deposits in question pass, on the landward side, beneath the deposits which bear vertebrate fossils. The bed at Vero, No. 2, must have been laid down after an uplift had brought above sea-level the bed of shells No. 1, on which No. 2 reposes; that is, between the time of deposition of No. 1 and No. 2 there must have elapsed a considerable interval of time. The shell deposit, therefore, probably belongs to the first glacial epoch, the Nebraskan. Inasmuch as a similar vertebrate fauna is found on both the eastern and the western coasts of the peninsula, it follows that any Pleistocene deposits underlying these vertebrate-bearing beds belongs to the Nebraskan stage; in places these have great thickness. Matson and Sanford (op. cit., pp. 194–195) concluded that the maximum thickness of the Pleistocene in southern Florida, disregarding the sandhills, is probably about 125 feet. Even if it were a matter of importance to determine in or on which terraces the vertebrate fossils are found, it would not always be easy to do so. The majority of specimens have been discovered around the coasts of the State, and therefore in deposits referred to the youngest terrace. In other cases it is difficult to determine the terrace in which fossils are buried, partly because of imperfect records as regards locality, kind of deposits, and depth of burial, partly because each terrace extends up the river valleys beyond its general border. The various fossil-bearing localities will therefore be taken up by counties, beginning at the western end of the State and ending at the southern end.
Jackson County.—As already recorded on page [121], a tooth of Mammut americanum has been found at Marianna. No details have been recorded. The Newberry terrace extends nearly or quite to this town. If it could be shown that this tooth had been buried in that terrace when it was formed, it would probably have to be referred to the time of the first glacial stage.
Gadsden County.—It appears that no vertebrate remains belonging to the Pleistocene have been found in this county, except a tooth of Mammut americanum (p. [157]) which was discovered somewhere in Little River.
Wakulla County.—On page [157] the finding of a tooth of Elephas columbi somewhere along St. Marks River has been mentioned; also the discovery of a part of a skeleton of either a mastodon or an elephant somewhere about Wakulla Springs.
Columbia County.—A mastodon tooth has been found in this county 3 miles northwest of Fort White (p. [121]). To which terrace it belonged or what is its place in Pleistocene time it is impossible to say.
Nassau County.—At Stokes Ferry have been found some teeth of an extinct horse (p. [194]), a fragment of a tooth of an elephant (p. [180]) and some ear-bones of a whale. Veatch and Stephenson (Bull. 26, Geol. Surv. Georgia, p. 394) report that these appeared to come from either the Charlton formation or the Satilla. If the Charlton really belongs to the Pliocene it is not probable that the fossils were derived from it; if they were derived from the Satilla, they do not belong to late Pleistocene.
Duval County.—On page 106 of the Eighth Annual Report of the Florida Geological Survey, Sellards reported the finding of remains of Mammut americanum (p. [122]), Elephas columbi (p. [157]), an undetermined species of Bison (p. [262]), and an undetermined species of Odocoileus (p. 232), near Pablo Beach, at station 120 on the Inland Waterway Canal. Here, too, has been discovered a bone of Trachemys? nuchocarinata. Sellards stated that the position of the beds here is the same as that of the other localities along the Atlantic coast, the fossils being found in sand and muck which rest upon Pleistocene shell-marl. The locality is, of course, on the youngest terrace; but that, in the opinion of the writer, belongs to the early Pleistocene.