GLACIAL WORK IN WESTERN MOUNTAINS JIQ 



The moraine formed by the northeastern ice sheet of the 

 Wisconsin epoch was traced from Fort Benton, via Choteau, to 

 the point where it crosses the 49th parallel, about longitude 

 112° 20'. From this point the moraine bends to the west and 

 continues in this direction to the Watertown River, where it 

 turns to the north, its course being nearly parallel to the moun- 

 tains. 



The moraines of fourteen glaciers from the Rocky Mountains 

 were mapped. The recessional moraines of both the valley and 

 continental ice masses were studied as far as time permitted. 

 Study was also made of the extent of valley trains and out- 

 wash plains, and of the lakes which existed in front of the ice 

 during the glacial period. 



Among the results of the work, the following may be men- 

 tioned : -: .- 

 ■ I. The westward and southwestward extension of the Wis- 

 consin drift is greater than had been suppcjsed. 



2. The till of the northeastern ice sheet and that of the moun- 

 tain glaciers overlap just south of the 49th parallel, between the 

 meridians of 113° 10' and 113° 15'. At no other point south 

 of the boundary line did the ice from opposite directions 

 occupy the same territory; but in Two Medicine Valley (lati- 

 tude 48° 30') the ice from the east advanced to within two 

 miles of the position occupied at an earlier time by the ice 

 from the mountains. 



3. The ice sheet from the northeast reached its most 

 advanced position after the valley glaciers from the west had 

 retreated, for the drift of the former overlies the drift of the 

 latter at various points, both north and south of the national 

 boundary. In some cases the till from the northeast overlies 

 the till from the west. This is true in the locality mentioned 

 under 2, and farther north in the valleys of St. Mar3^'s River, 

 Belly River, and Lees Creek. In other places the till from the 

 east overlies fluviatile deposits connected with the western drift, 

 but extending down the valleys some miles beyond (east of) the 

 ends of the mountain glaciers. In still other cases lacustrine 



