[COLEMAN] THE DRIFT OF AFBERTA 7 



is disclosed in cuttings there are Laurentiau boulders as well as quartzites 

 fi'om the mountains. For the whole distance the boulder clay contains 

 rocks of both origins, indicating similar relationships to those already 

 described. 



The Edmonton Eegion, 



While Calgary is only 40 miles from the mountains Edmonton is 

 not far from midway between the Archaean area surroanding Hudson 

 bay and the Eocky Mountains, owing to the northwesterly trend of the 

 pliysical features of the continent. ^ Most of the surface of the flat plain 

 around Edmonton is formed of old lake deposits, silt and clay; so that 

 sections showing boulder clay are found only along the valleys of the 

 Saskatchewan and its tributaries, cut 150 feet below the genej-al level of 

 the country. The lower part of the sections consisting of Laramie 

 sandstone and shale with seams of coal, may be neglected here. 



At the descent from Edmonton towards the bridge leading to 

 Strathcona typical boulder clay is seen beneath a few feet of the vaguely 

 stratified clay forming the surface of the plain. The thickness of till 

 varies from 10 to 15 feet, and the stones contained in it are largely 

 Archaean, though there are some Roclcy Mountain quartzites, and also 

 local stones, such as siderite concretions and bits of coal. Under the 

 till is soft sandstone 6 or 8 feet thick and then gravel or a crumbling 

 conglomerate, both probably belonging to the Laramie. The pebbles of 

 the conglomerate, often several inches in diameter, are entirely of Eocky 

 Mountain origin, so far as seen, and may have furnished part or all of 

 the quartzites found in the overlying boulder clay. 



An exposure on the cliff a few hundred yards down Lhe river shows 

 20 feet of till with mostly Archfean stones. Above it is yellow sandy 

 clay 5 feet in thickness, containing in one place a lens of boulder clay 

 a foot and a half thick and 12 feet long. This till must have been depo- 

 sited close to the shifting margin of the ice. The surface here is formed 

 of a few feet of loess-like silt or clay. 



In Strathcona on the south side of the Saskatchewan similar sections 

 occur, though more obscured by landslips. At one place near the point 

 where the road from the bridge reaches the general level of the plain the 

 boulder clay is covered with coarse gravel followed by stratified clay and 

 loess-like clay. About 300 yards to the southwest similar gravel is seen 

 underlying boulder clay. The pebbles in this gravel are sometimes a 

 foot in diameter and include both Archaean and Eocky Mountain stones.2 



1 About 150 miles from the Rockies and- 250 from the Archsean, measured in 

 a direction from the southwest to northeast. 



2 Compare Dawson's account in Bull. G.S.A., vol. 7, p. 55 (note). 



