DEDUCTIONS FROM RELATIONS OF THE DRIFT 553 



of more than one till observed. At some of the localities, however, the 

 bottom of the drift filling the preglacial valley has not yet been reached 

 by the stream. 



Going up the valley of Oldman Biver, a section wos observed at the 

 wagon bridge near Brocket, 16 miles southwest of Macleod, exposing the 

 following : 



Pleistocene Deposits near Brocket, Alberta 



D. Coarse gravel underlying a river terrace and lying on the eroded Feet 

 surface of the till 15 



C. Dense, dark, gray till (Wisconsin ?) pebbles, mostly from the 

 Rocky Mountains with a small percentage of Laurentian crys- 

 talines to 20 



B. Dark laminated silt (interglacial ?) 1 to 3 



A. Dense, gray till (pre-Wisconsin ?), not very stony, pebbles mostly 

 from Rocky Mountains, with a very small percentage of Lauren- 

 tian crystallines 30 



Here again the deposits A and B may perhaps represent the beds B 

 and C respectively in the Lethbridge exposure. 



This is the most westerly point at which we observed any evidence of 

 more than one sheet of till deposited by the continental glacier. At the 

 nearest point the mountain front is distant about 20 miles to the south- 

 westward. At the exposure near Brocket, the river has not yet cut down 

 to the bottom of the drift filling in the preglacial valley. From this rela- 

 tion it appears that at least one of the main streams had cut below its 

 present level before the first invasion of the region by the Keewatin ice- 

 sheet of which we have evidence. Evidently preglacial erosion had pro- 

 gressed much farther here than it had in the Browning quadrangle, or 

 else the lower till deposit of the Keewatin ice is not as old as that de- 

 posited by the Rocky Mountain glaciers on the Blackfoot peneplain in 

 the Browning quadrangle. 



In the vicinity of the confluence of Waterton and Belly rivers, and 

 southwestward to points within a few miles of the village of Hill Spring, 

 Alberta (township 4 north, range 27 west), numerous places were ob- 

 served where the bottom of the drifl filling lias nol yel been reached by 

 the streams. In these places, however, no evidence was noted which 

 seemed to warrant regarding the lowesl I ill exposed as older than the 

 Wisconsin stage. It can not therefore be asserted thai these valleys were 

 deeper than now this far sou i h al the time the lower drift was being 

 deposited in the vicinity of Lethbridge. 



