[coLEiLiN] THE DRIFT OF ALBERTA 8 



100 feet of pleistocene materials are found, the lower part largely 

 covered, however, by the slipping of clay and sand from the upper layers. 

 A freshly under cut part of the bank a few hundred yards south of 

 the railway bridge shows a fairly complete section, as follows : 



FEET 



Upper Boulder clay 30 



Uncertain (some slipping of ground) 34^^ 



Silt, well stratified 4 



Boulder clay II/2 



Silt, well stratified 10 



Lower Boulder clay to level of river 15 



95 



The upper boulder clay is of the usual kind at this distance from the 

 mountains, containing some Arohœan stones, principally granite, a much 

 greater number of Rocky Mountain quartzites and blue limestones, 

 and a few large boulders of local sandstone. The Eocky mountain 

 stones are often rounded, but include angular bits also. The limestones 

 are often well polished and striated. 



The lower boulder clay is \ery like the upper in general appearance; 

 but a careful study showed only 'Roeky Mountain and local stones in 

 the clay. Archœan boulders or pehhles could not he found. 



The lower boulder clay was deposited then by a glacier advancing 

 from the mountains. 



The silt above this till is interglacial, though the small sheet of 

 interbedded till indicates glacial conditions near by. 



Going up Elbow river a quarter of a mile other sections are dis- 

 closed, generally with the lower part buried under debris slid from above. 

 At the best exposure a quite different assemblage of materials was found, 

 consisting a few feet of loess like clay or silt on top, then 5 to 10 feet 

 of the upper boulder clay, with some Archaean stones, and below this 

 an unknown thickness of coarse gravel and stratified silt and sand, 

 reaching down beneath the talus slope. No Archaean stones were found 

 in the gravel, which is no doubt interglacial. It is clear that this was 

 an interglacial river valley buried under a varjdng thickness of till laid 

 down by the Keewatin ice sheet. 



The sections just described difi'er greatly from those found by 

 Dawson and McConnell on Bow river not far away.^ 



The Keewatin glacier advanced then over a Cordilleran till sheet 

 which it largely worked over, mingling the few Archaean stones which 



1 Bull. G.S.A. Vol. 7, pp. 53-5. 



