THE M'CAULEYVILLE BEACHES. 427 



BEACHES OF THE ]VrCAUr,EYVIIiIiE STAGES. 



The channel of the River Warren, outflowing from Lake Agassiz, had 

 been eroded behiw the level of Lakes Traverse and Big Stone when the 

 McCaiileyville beaches l)egan to be accumulated. Portions of the bottom 

 of the river-course are now the beds of these lakes, whose luaximum depths 

 are reported to be respectively about 15 and 30 feet. In the vicinity of 

 White Rock the bottom of the River Warren, eroded in till, is 9G5 to 970 

 feet above the sea. Along the broad tract of marsh, Avith lakelets, between 

 White Rock and Lake Traverse, the depth of the alluvial swamp}' deposit 

 probably ranges from 10 to If) feet, reaching down to the level of the 

 deepest part of the l^ed of Lake Traverse, apj)roximatelv 955 feet above 

 the sea. This or a slightly greater depth of tlie channel continued between 

 Lakes Traverse and Big Stone, Avhere alluvium has since been brought in 

 by the head stream of the Minnesota River to the depth of 25 feet or more. 

 The bed of Big- Stone Lake siidcs to about 935 feet in its deepest part, and 

 the alluvium of the Whetstone River, which is spread along the Minnesota 

 Valley below this lake, has probably a corresponding thickness of at least 

 30 feet. 



The southern portions of the McCauleyville shore-lines of Lake Agassiz 

 coincide nearly witli the levels of high and low water in Lake Traverse, 

 which are approximately 976 and 970 feet above the sea. The highest 

 yearly stage of the glacial lake attended the more rapid melting of the ice- 

 sheet in summer, while its winter stages doubtless fluctuated so low at 

 times as to reduce the depth of the River Warren to only a few feet. No 

 appreciable epeirogenic movement of the south part of the lacustrine area 

 appears to have taken place during the time of formation of the McCauley- 

 ville beaches; but northward, in Manitoba, the earth's crust was uplifted 

 15 to 50 feet within this time, as shown by its upper and lower shore-lines. 



Along nearly all of their course the Campbell and McCauleyville 

 shores lie nearly parallel, and are only a few miles or mainly less than 1 

 mile apart, permitting both to be mapped, with determination of their 

 heights, from a single line of survey. The latter are 10 to 20 or 30 feet 

 below the former in their soiithern portion, but the vertical range of the 

 two series increases to 70 feet in southwestern Manitoba, while the highest 



