Glacial and Interglacial Periods in Eastern Canada

In a study of the Pleistocene of Newfoundland in this Journal (April-May, 1926) it was shown that the island had undergone two glaciations, a severe one in the early Pleistocene, separated by a long interglacial period from a late Pleistocene ice invasion of less intensity. As eastern Canada lies between Newfoundland, with its two glaciations, and the Toronto region, likewise showing two glaciations and an important interglacial period, it seemed very probable that it also must have been glaciated twice. Field work in Quebec and eastern Ontario has proved that this was the case, and it has been shown that deposits containing marine shells lie between two bowlder clays at a number of points between Gaspé and Brockville along the St. Lawrence and its tributaries. The interglacial time was long enough to permit profound weathering of the early glacial materials, so that comparatively little of the Kansan or Jerseyan till remains, accounting for the fact that the first glaciation has usually been overlooked. There were more extensive changes of level in the interglacial time than in the postglacial history of the regions; but the two sets of marine beds have not been separated in previous studies of the Pleistocene of eastern Canada, thus causing much confusion. The new point of view solves many difficulties in the interpretation of the drift deposits of the St. Lawrence and Gulf region, and harmonizes conflicting points of view.