NATURAL HISTORY, TORONTO REGION
Above this sheet of boulder clay resting on the eroded surface of the delta there, are three other layers of till with stratified sand or clay between, the whole reaching a thickness of two hundred feet. None of the upper interglacial beds seem of much importance compared with the earliest, the Toronto Formation.
At certain sand pits in western Toronto near Christie and Shaw Streets, a little north of Bloor Street, there are interglacial deposits of a quite different character, cross-bedded sand and gravel laid down by powerful currents. In these beds bones of bison, Cervalces borealis, and of mammoth or mastodon have been found, as well as ivory and a few shells. The relations of these sands to the other beds are uncertain, but they are undoubtedly inter-glacial.
Interglacial beds have been found at the Whirl-pool, Niagara, near Dundas, at the head of Lake Ontario, and at some other points ; but few or no fossils have been obtained from them, and it is not known whether they should be correlated with the Toronto Formation or not. There is some reason to believe that the Aftonian interglacial beds of Iowa, which have yielded Cervalces, as well as a number of other mammals, may be of the same age as the Toronto Formation.
Each advance of the ice must have ponded back the water before it in the present lake basins, but 72