2 ■ THE GLACIAL LAKE AGASSIZ 



As this report necessarily treats of the topographic features of the 

 basin of the Red River and Lake Winnipeg-, it has seemed desirable to 

 devote a chapter to the rock formations which underlie the glacial drift and 

 the old lake bed, with discussion of the preglacial erosion that gave the 

 general outhnes of the Red River Valley plain and of the Manitoba escarp- 

 ment bounding it on the west. Though this part is presented somewhat 

 briefly, it is hoped that the reader will be able to obtain in it a compre- 

 hensive review of the entire geologic history of this area, and of its uplift 

 and sculptvmng to the form of a basin, previous to the Ice age and the time 

 of Lake Agassiz. 



The economic geology of this basin has received a large share of 

 attention during the progress of the field work and in the present volume. 

 Owing to the structure of the drift deposits and of the underlying rocks, 

 many artesian wells have been obtained in the Red River Valley, descrip- 

 tive notes of which are given, with analyses of their waters, and an expla- 

 nation of the sources, in part near and probably in part hundreds of miles 

 distant, from which the waters and their dissolved mineral matter are 

 derived. No commercially valuable deposits of ores, coal, natural gas, or 

 salt can be reported, but the northern part of the Red River Valley, in 

 Manitoba, has magnesian limestone of excellent quality for building pur- 

 poses and for the manufacture of lime, and the whole valley has plentiful 

 beds of clay, unsurpassed for brickmaking. The chief resources of this 

 extensive prairie region of Lake Agassiz, however, are found in its very 

 fertile soil and favorable climate for agriculture, and especially for wheat 

 raising. 



THE GLACIAL, LAKE AGASSIZ. 



During the closing part of the latest completed division of geologic 

 time a vast lake stretched from the southern end of the Red River Valley 

 north to the Saskatchewan and Nelson rivers. The late date of its exist- 

 ence is known by the position of its shore-lines and deltas, which lie upon 

 the glacial drift and have nearly as perfect outlines as those of the present 

 shores of the Manitoba and Laurentian lakes or of the ocean. This ancient 

 lake, several times larger than Superior — indeed, exceeding the aggregate 

 area of the five great lakes tributary to the St. Lawrence— washed the east 



