A brief interesting account of the Pleistocene epoch as recorded in Massachusetts and Rhode Island may be found in an article by B. K. Emerson (Bull. U. S. Geol. Surv., No. 597, pp. 134–149). It deals in part with the geology of the valley of the Connecticut River.
Goldthwait (Appalachia, vol. XIII, pp. 1–23) and Foshay (Amer. Jour. Sci., ser. 4, vol. XXXVIII, pp. 345–348) have found evidences of an early Pleistocene glaciation in the White Mountains of New Hampshire.
Vermont is interesting especially on account of the Pleistocene history of Lake Champlain. This history has been recently discussed by Professor H. L. Fairchild (Rep. State Geologist Vermont, vol. X, 1916, pp. 1–41, with maps and views), who presents (pp. 40–411) a list, 37 in number, of the more important papers relating to the subject.
While the Wisconsin ice-sheet was resting upon Canada and the northern part of the United States, the land thus occupied, and probably a considerable area beyond the ice, became depressed. The valleys of the St. Lawrence, the Ottawa, the Hudson, and the Connecticut had been pressed down to such an extent that, as the ice-sheet retired these valleys became filled with water standing at sea-level. When at length the glacial front had retreated beyond the St. Lawrence, sea-water entered Lake Ontario and passed up Ottawa River far above the city of Ottawa (Leverett, Monogr. U. S. Geol. Surv., LIII, plate XXI). South of the St. Lawrence, marine waters occupied what is now Lake Champlain and as much of the surrounding land as was then at or below sea-level. In his account Fairchild makes use of the plate which is here reproduced (map [31]) from his article of 1917 (Bull. Geol. Soc. Amer., vol. XXVIII, p. 279, plate XI). This geologist believes that the Hudson formed for a while a connection with Lake Champlain, although the Hudson waters may not have been actually saline. But in Lake Champlain the presence of fossil marine mollusks and at least one whale skeleton shows that its waters were salt. The lines crossing the plate obliquely are the isobases which show the amount of elevation which has taken place along those lines since the end of the Pleistocene. South of New York City this is zero. At the northern end of Lake Champlain the elevation is 800 feet. This means that the north end of the lake for a while stood 800 feet lower than now. Marine fossils have, however, been found at an elevation of only about 300 feet. The waters which first occupied the lake and stood at the highest level were of glacial origin and fresh. When the ice-front had receded so as to open the St. Lawrence and admit sea-water, the northern end of the lake had been uplifted about 500 feet. It was then that the marine animals entered.
Other important papers to be consulted in this connection are as follows: One by J. B. Woodworth (Bull. 84 New York State Mus.); one by Charles E. Peet (Jour. Geol., vol. XII, 1904, pp. 415–469; 617–660), and two by Professor Fairchild (Bulls. 105, 127, New York State Mus.).
It is proper to say that certain glacial geologists maintain that the depression in the New England States has been less than supposed by Fairchild, and that the isobases curved around toward the north as the New England coast was approached, somewhat as represented by Taylor (Monogr. LIII, U. S. Geol. Surv., p. 503). Fairchild, in a later paper (Bull. Geol. Soc. Amer., vol. XXIX, 1918, pp. 187–244), has reached the same conclusion and presented a map on which are drawn the isobases, or lines passing through points affected by the same amount of post-glacial uplift; from this map [32] has been prepared. On his map the location of the heavy or solid lines is regarded by Fairchild as being based on clear evidence. Where the lines become thin the evidence is less trustworthy; where the lines are broken their positions are hypothetical. The numerals on the lines show the amount of uplift along those lines. Two points of importance are brought out on the map. The first is that Newfoundland formed an independent center of glaciation and of subsequent uplift, a conclusion based on good geological evidence. The second point is that the center of the Wisconsin glaciation was located southeast of James Bay, considerably farther south and west than is usually supposed. The confirmation of this is left to the future.
It does not seem to have been demonstrated that there are in Connecticut any Pleistocene deposits older than those laid down by the Wisconsin ice-sheet. In case Fuller (U. S. Geol. Surv. Prof. Paper 82) is correct in his determination of beds of the early, middle, and late Pleistocene on Long Island, it is to be expected that beds of corresponding ages will yet be recognized in Connecticut. Woodworth (17th Ann. Rep. U. S. Geol. Surv., pt. 1, p. 978) mentions deposits of clay at Berlin and at New Haven that may be older than the Wisconsin.
While the correlations recorded above of the Pleistocene of the New England States with the glacial and interglacial stages of the Mississippi Valley may be subject to modifications, it is interesting to learn that the presence of Middle and Early Pleistocene deposits in the Eastern States has received the recognition of so many students of glacial geology. The hope is awakened that in New England there may yet be found interglacial deposits which will furnish remains of Pleistocene vertebrates, as these have come to light from Throg’s Neck, New York, to southern Florida. It is possible that the astragalus of an equine animal (p. [183]), found at Gay Head, Martha’s Vineyard, belongs to a species of Equus of early Pleistocene age.
In order to illustrate still further the events connected with the history of the Pleistocene in the region of the Great Lakes, three additional figures are introduced. One of these (map [33]) shows J. W. Spencer’s conception of the drainage of the region in preglacial times. The areas now occupied by the lakes were then traversed by rivers. It will be observed that the rivers above Pittsburgh now discharging into the Ohio then emptied northward into the Erigan. This is shown also by a map (fig. 6) taken from Leverett (U. S. Geol. Surv. Monogr. XLI, p. 89). Figure [5], on page [287], shows the position of the shore of this Champlain Sea.
The number of Pleistocene vertebrates found in the New England States is limited, and most of them have been mentioned.