GLACIO-LACUSTRINE STAGE 



641 



to the north and northeast. It is probable that there were corre- 

 sponding lacustrine substages at the close of each of the several 

 glacial epochs, but their history is not known. 



In the later part of this substage, an arm of the sea extended up 

 the St. Lawrence to Lake Ontario, filling the basin of Lake Cham- 

 plain (Fig. 531). It probably connected southward by a narrow 



Fig. 532. Map of the extinct Lake Agassiz, and other glacial lakes. Lake 

 Winnipeg occupies u part of the basin of Lake Agassiz. (U. S. Geol. Surv.) 



strait along the site of the Hudson valley with the ocean. The 

 sediments deposited in this arm of the sea contain shells and bones 

 of marine animals. The marine fossils are found at various places 

 about Lake Champlain at altitudes varying from 400 feet or less 

 about the south end of the lake, to 500 feet at the north end, and 

 about 600 feet near the east end of Lake Ontario. 1 At about the 

 same time the sea stood higher than now relative to the land on the 



1 Dawson, G. M., Am. Jour. Sci., 3d ser., Vol. VIII (1874), p. 143; Dawson, 

 J. W., The Canadian Ice Age, p. 201, and Am. Jour. Sci., Vol. CXXV, 1883. 



