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A. E. CAMERON 



wan and Churchill rivers lying in a sandy plain at the bottom of the 

 deep valley. As will be shown later, a portion of this valley prob- 

 ably at one time was the principal drainage channel of great post- 

 glacial lakes lying in the Athabaska and Peace river valleys, 

 though possibly Hyper-Churchill Lake intervened to take the 

 waters from Hyper-Athabaska Lake before discharging them into 

 the Saskatchewan River. 



A second channel is suggested in his account of the east end of 

 Athabaska Lake and the valley of Stone River below Black Lake. 

 This appears as a short, narrow channel connecting the waters of 

 Hyper-Athabaska Lake with those of Hyper-Black Lake. It 

 would seem very probable that during a certain period of the lake 

 formations these two bodies of water were confluent by way of this 

 channel, and that the outlet of the chain of lakes lay possibly by 

 way of Mudjatick River Valley to Hyper- Churchill Lake or by 

 another channel farther east. 



Just at the eastern end of Athabaska Lake Tyrrell reports two 

 distinct sets of glacial striae: an earHer one tending south, 65° west, 

 parallel to other striae seen almost everywhere along the shore and 

 doubtless made by the ice sheet from the northeast ; and a later one, 

 tending south, 35° west, probably made by a local glacier descending 

 from the high land to the north after the greater ice sheet had 

 withdrawn. 



A portion of the moraine of this later local glacier may be seen as a great 

 stretch of huge broken masses of rock, forming a prominent point, and covering 



the shore for a considerable distance beyond it Athabasca Lake is here 



five miles wide, and lies in a long narrow valley with a steep sandstone escarp- 

 ment between 400 and 500 feet high on its south side. The later glacier from 

 the north flowed into the valley at this point, and probably reached across to 

 the south side, completely fiUing it and damming up the water from the east 

 to the height of the sandstone plain on the south, which is at about the level 

 of the high benches previously described on the banks of Cree River and 

 along the west shore of Black Lake. The occurrence of an ice dam across the 

 valley accounts fully for the former existence of a large lake in the present 

 basin of Black Lake. Without the ice dam, or some other dam of which no 

 evidence can be found, the water of Black Lake could not have stood much 

 above its present level in glacial or post-glacial times, for the great valley of 

 Athabasca Lake, which extends eastward to Black Lake, dates back to a period 

 long before the glacial epoch. 



