250 W. UPHAM — GLACIAL LAKES IN CANADA. 



mately they will be shown to be everywhere attributable either to fluvial depo- 

 sition attendant on the recession of the ice-sheet or to deposition as deltas in 

 glacial lakes, which owed their existence to ice-dams or to depressions where 

 the land had sunk beneath the ice-w^eight and has since been reelevated. 

 For example, the Kootanie basin may well have been filled by a glacial lake 

 obstructed in the present course of drainage by the retreating ice-sheet and 

 outflowing by the way of Pack river and Lake Pend d'Oreille, which Presi- 

 dent Chamberlin finds to have been covered by the maximum advance of 

 the ice, while gravel-bearing floods from the glacial melting poured thence 

 to the south and west. * Again, the silts on the Peace river east of the 

 Rocky mountains seem referable, as will be stated more fully on a later page, 

 to a glacial lake held by the barrier of the departing ice-sheet on the north 

 and northeast, with outflow southeastward into Lake Agassiz. 



Alberta, Assinihoia, and Saskatchewan. — During the recession of the ice- 

 sheet from Alberta, small glacial lakes doubtless existed in the basins of the 

 Bow and Belly rivers, outflowing from the former successively by the Little 

 Bow river and the Snake valley, aud from the latter successively^by the 

 Verdigris, Etsi-kom, and Chin coulees, which Dr. Dawson describes as re- 

 markable abandoned river-courses now carrying little or no water. The 

 glacial drainage from the present sources of the South Saskatchewan, and 

 })robabIy also of the North Saskatchewan and Athabasca, was thus carried 

 southeastward, in parallelism both with the main Rocky Mountain range and 

 with the retiring ice-border, to the Milk^ river west and south of the Cypress 

 hills. The whole area of Alberta, partly land sloping northeastward and 

 partly ice sloping southwestward, with glacial lakes here aud there along the 

 ice-margin, seems then to have been tributary to the Missouri and the Gulf 

 of Mexico.f 



From Lake Pakowki, through which this glacial drainage for a long time 

 flowed southward to the Milk river, the ice-front must have been withdrawn 

 more than two hundred miles to the east, past the Cypress hills and Wood 

 mountain, before a lower outlet from the Saskatchewan country north of 

 these highlands would be obtained by Twelve Mile lake and over the pres- 

 ent continental water-shed to Big Muddy creek, which flows through the 

 northeastern corner of Montana to the Missouri. But only a slight further 

 retreat of the ice was sufiicient to give still lower avenues of drainage. As 

 soon as the Missouri coteau was uncovered, a glacial lake occupying the 

 valley of the South Saskatchewan in the vicinity of its elbow outflowed by 

 the way of Moose Jaw creek, and through a glacial lake in the upper Souris 

 or Mouse river basin, to the Missouri near Fort Stevenson. Later the out- 

 flow from the Lake Saskatchewan may have passed to the Lake Souris 

 by way of the Wascana river, after flowing through a glacial lake which 



* U. S. Geol. Survey, Bulletin No. 40, p. 8. 



t Compare with Mr. J. B, Tyrrell's paper in Bull. Geol, Soc. Am., vol. 1, pp. 401, 403. 



