160 THE GLACIAL LAKE AGASSIZ. 



this being the only interruption of the lacustrine and allu\-ial clayey silt 

 which elsewhere continuously occupies the central part of the Red River 

 Valley plain from near Breckenridge to Winnipeg. 



In North Dakota the Fergus Falls moraine passes southward in a loop 

 outlining a lobe of the ice-sheet which lay between Lake Agassiz and the 

 Sheyenne River. This lobe reached about 40 miles south from the latitude 

 of Caledonia, which marks approximately the apex of a glacial reentrant 

 angle in the Red River Valley, where the laving action of Lake Agassiz 

 appears to have caused the melting of the ice border to progress faster 

 than on the land surface at each side. Emerging from the lacustrine area, 

 on which its drift was leveled by the waves, the Fergus Falls moraine pre- 

 sents a prominently rolling surface of till west-southwest of Galesburg, and 

 forms typical morainic hills in the northwest part of township 142, range 



53, 1 to 3 miles west of Erie, rising 50 to 75 feet above the intervening 

 hollows and the adjoining surface of smoothly undulating till westward, 

 and 100 feet or more above the highest shore of Lake Agassiz. Thence 

 the east boundar}^ of the ice-lobe is marked bj- rolling and knoUy till, 

 with plentiful bowlders, and b}' low kames of gravel and sand, occupying 

 generally a belt about 1 mile wide, which runs south-southwestward close 

 north and west of Ayr and southward across the Northern Pacific Railroad 

 1 to 2 miles east of Buffalo. In the northwest part of township 139, range 



54, a few miles south of this railroad, this morainic belt, continuing with 

 similar features, turns to the west-southwest, crosses the Maple River, and 

 holds this course about a dozen miles, passing through sections 25 to 28 

 and 32 and 31, township 139, range 56. This portion defines the southern 

 extremity of the ice-lobe, the distance of its retreat from the Dovre moraine 

 at Taylor Lake and near Geneseo and Ca3aiga having been about 55 miles. 

 In Minnesota the recession of the ice from Dovre to the Leaf Hills was 60 

 miles, and along the Red River Valley it was approximately 100 miles 

 from the southeast corner of North Dakota, to Caledonia. 



Occasional kame knolls and small plateaus of gravel and sand, 15 to 

 25 feet high, were observed along a distance of a dozen miles south of the 

 end of this morainic loop, in townships 138 and 137, range 57, showing 

 where glacial streams had flowed down from the ice-sheet during its retreat 



