240 The American Geologist. October, 1894 
intervened between the deposition of the Lafayette formation 
and the Ice age; and, in a recent paper before this Society, I 
have shown that the successive Lafayette epochs of deposition 
and erosion are also recognizable in this more northern area 
drained principally by the Nelson river.* 
Origin of the Red river valley and the Manitoba escarp- 
ment BY THIS LATEK EROSION. 
East from the foot of the Pembina, Riding, and Duck moun- 
tains and the hills farther north, together called the Manitoba 
escarpment by Mr. J. B. Tyrrell, of the Canadian Geological 
Survev, Cretaceous strata have not been found, so far as I 
have learned, in Manitoba, nor in the region north and north- 
east from lake Winnipeg to Hudson bay. It seems quite cer- 
tain, however, that Cretaceous beds continuous from this es- 
carpment extended eastward at the end of the Tertiary base- 
leveling so far as to cover the area of lake Winnipeg^ As 
Hind and Dawson have well pointed out, it was by the erosion 
of the eastern portion of these beds, after the great western 
expanse of the plains had received nearly its present form, 
that this steep escarpment was produced. f At the time of 
uplifting of the plains near the beginning of the Quaternary 
era. this great baseleveled region appears to have stretched 
from the Rocky mountains to the Archean hills on the eastern 
border of the area of the later glacial lake Agassiz. The east 
margin of the soft Cretaceous strata was then anew subjected 
to rapid erosion, wkh the result that it was almost wholly 
worn away to the floor of the Archean gneiss and granite and 
Paleozoic limestones upon a width of 100 miles or more and 
to a depth westward of 800 to 1,000 feet as shown by thehight 
of the Pembina mountain and Manitoba escarpment. 
In Minnesota and North Dakota the flat Red river valley 
plain, averaging 50 miles wide, with a depth of 200 to 500 
feet below the country on each side, and extending more than 
200 miles from south to north, opening into the Manitoba lake 
area, appears also to have been eroded at the same time. The 
*Bulletin, Geol. Societj of America, vol. v. 1804, pp. 87-100. 
|H. Y. 1 1 i ml. Report of the Assiniboine anil Saskatchewan Exploring 
Expedition, Toronto, 1859, pp. 168, 169; Narrative of the Canadian Ex- 
ploring Expeditions, London. 1860, vol. n, pp. 48, 55, and 265. <i. M. 
Dawson. Geology and Resources of the Forty-ninth Parallel. 1ST."), pp. 
253, 254. 
