147 



Miles and light venccr of lower Tertiary continuing for 

 some distance to the east. This plain is sup- 

 posed to have been a glacial lake basin, known 

 as Lake Saskatchewan, occupying part of the 

 valleys of the North and South Saskatchewan 

 and blocked or dammed to the northeast by 

 the retreating Keewatin ice sheet. The exist- 

 ence of this lake, as inferred from the silts 

 covering the surface, was not of long duration, 

 since no strongly marked beaches are apparent. 

 Milepost 478 marks the western edge of the 

 flat country west of the Saskatchewan valley 

 and may also mark the western limit of the 

 glacial lake at its lowest stage in this latitude. 



467 m. Saskatoon— Altitude 1,665 ft. (507 m.). 



751 -4 km. Saskatoon is situated on both sides of the 

 Saskatchewan valley. Eastwards to Young, 

 the country is flat with little evidence to show 

 the character of the underlying rocks. The 

 few cuttings show sandy clay with very few 

 boulders. 



422 m. Young — Altitude 1,714 ft. (522 m.). Near 



679 km. the station there appears to be a possible outlet 

 valley to the southeast for the glacial Lake 

 Saskatchewan. This valley appears to join the 

 deep valley occupied by Lost Mountain lake, 

 which is a tributary of the Qu'Appelle. The 

 difference in elevation between Young and 

 Lost Mountain lake is 118 feet (35-8 m.) and 

 if the drainage was southwards at any time 

 it was of short duration otherwise it would 

 be expected that the valley of Lost Mountain 

 would have deepened itself further to the 

 north. 



The deep valley of the tributary of the 

 Qu'Appelle lying west of the foot of Lost 

 Mountain lake and extending to the elbow of 

 the South Saskatchewan, marks the old main 

 channel of the latter river when it flowed east- 

 wards through the length of the present Qu'Ap- 

 pelle valley. 



408 m. Watrous — Altitude i, 781 ft. (543 m.). The 



656 km. position of the front of the Keewatin ice sheet 

 during a pause or a series of advances and 

 36425— iqI 



