SUMMARY 571 



quadrangle. It should also include drift of the Cordilleran Glacier, 

 which may be shown to be of the same age, though lying in the valleys 

 farther north, but should not include the mountain drift composing the 

 moraines near the front of the Eocky Mountains in southwestern Alberta, 

 the latter moraine probably being of Wisconsin age. Thus applied it 

 would be used in a sense not greatly different from that intended by 

 Dawson, as designating the stage at which occurred the earliest known 

 extension of the Cordilleran Glacier and the deposits formed by this gla- 

 cier at this early stage. We do not, however, favor the continued use of 

 the name ''Albertan." 



17. It seems probable that the earliest stage of Cordilleran glaciation 

 corresponds either to the earliest known stage of continental glaciation — 

 that is, pre-Kansan or Nebraskan or to the Kansan stage — but the correla- 

 tion is as yet undetermined. 



18. The occurrence of gravelly deposits, underlying the second and 

 lower set of plains and containing striated pebbles, may be regarded as 

 evidence of a second pre-Wisconsin extension of the Cordilleran glaciers, 

 but the relations are not conclusive. 



Addendum 



Evidence of a pre-Wisconsin continental glaciation extending south of 

 the International Boundary, and probably the counterpart of the pied- 

 mont glaciation on the high levels near the mountains, has recently been 

 obtained as a result of field work during the summer and fall of 1913. 

 About 15 miles east of the Sweetgrass Hills (see figure 1), on a small 

 coulee tributary to Sage Creek from the north, in township 36 north, 

 range 8 east, Montana, the following section was observed in good ex- 

 posures extending several hundred feet along the nearly vertical banks of 

 the coulee. 



Pleistocene Deposits near Sage Creek, Toivnship 86 North, Range 8 East, 



Montana „ J 



Feet 



C. Stony, compact till of Keewatin Glacier (Wisconsin stage), containing 

 an abundance of Laurentian crystalline pebbles and Paleozoic ? lime- 

 stone pebbles. This till is as fresh and unweathered as that usually 

 found in the drift of Wisconsin age B 



B. Stony, compact, but n inch- weathered till of Keewatin Glacier (pre- 

 Wisconsin stage), containing many Laurentian crystalline pebbles, 

 but no, or only very few, limestone pebbles 6 



A. Clay and sandstone of Judith River formation (Cretaceous) 



The recognition of two separate drift sheets in the above section rests 

 entirely on the difference in the amount of weathering present in each, 



