ABSTRACT OF VOLUME, 



Chapter I: Introduction. — Lake Agassiz occupied the basin of the Red River of the North and of 

 Lake Winnipeg. Its northern barrier was the retreating ice-sheet of the Glacial period. That 

 a great lake had existed here was recognized by Keating in 1823, and later by Owen, Palliser, 

 Hind, Dawson, Warren, and N. H. Winchell. 



It was named in 1879 to commemorate Louis Agassiz, who established the theory that the drift 

 was due to glaciation. Its southward outlet was named the River Warren in 1883. The work 

 here reported comprises explorations performed for the geological surveys of Minnesota, the 

 United States, and Canada. Previous reports and papers relating to Lake Agassiz and its 

 dependence on the waning ice-sheet are noted. 



Chapter II: Topography op the basin op Lake Agassiz. — The bed of this lake is the flat Red 

 River Valley plain. Its channel of outlet by the River Warren is now occupied by lakes Traverse 

 and Big Stone and the Minnesota River. The shore-lines of Lake Agassiz are commonly m.irked 

 by beach ridges of gravel and sand a few feet high; less frequently by an eroded escarpment 

 from 10 to 30 feet high. Several large deltas were formed contemporaneously with the highest 

 shore-line. East of Lake Agassiz is a somewhat higher wooded country, on which are the Giants 

 and Mesabi ranges and the moraiuic Leaf Hills. On the west are the Coteau des Prairies and the 

 Manitoba escarpment, the latter comprising the Pembina, Riding, and Duck moimtains and 

 the Porcupine and Pasquia hills. Lake Agassiz is now represented by lakes Winnipeg, Mani- 

 toba, and Winnipegosis ; while Rainy Lake, the Lake of the Woods, and Red Lake lie within 

 its southeastern boundary. Its basin is drained by the Rainy, Winnipeg, Red, Assiniboine, and 

 Saskatchewan rivers, and others of smaller size. For some time, also, Lake Agassiz probably 

 received streams outflowing from glacial lakes in the basins of the Peace and Athabasca rivers. 

 The area of Lake Agassiz was approximately 110,000 square miles, and the country tributary to 

 it was 350,000 to 500,000 square miles. The length of the lake was nearly 700 miles ; its maxi- 

 mum width in Manitoba was probably more than 250 miles; and its maximum depth, during its 

 earliest and highest stage, was about 700 feet above the present level of Lake Winnipeg. 



Chapter III: Geologic formations underlying the drift. — The bed rocks of this lacustrine area 

 comprise, in their order from east to west, Archean, Lower and Upper Silurian, Devonian, and 

 Cretaceous formations. Sections of the Paleozoic rocks are known by borings for artesian wells 

 at Humboldt, Minn., Grafton, N. Dak., and Rosenfeld and Morden, Manitoba. Cretaceous strata 

 extend from Lake Agassiz westward across the plains to the Rocky Mountains. During the 

 Tertiary era these strata had been greatly denuded, being generally worn down to an almost flat 

 expanse. The vertical amount of the erosion was thousands of feet at the west and hundreds of 

 feet at the east, as shown by mountains and hills that Avere spared. Later erosion, during an 

 epeirogenic uplift closing the Tertiary and beginning the Quaternary era, removed the eastern 

 partof the Cretaceous beds, and thus formed the broad trough of the Red River Valley and of the 

 Manitoba lake region, which was the basin of Lake Agassiz. 



