
° GENERAL OUTLINE OF THE GEOLOGY. 11 
of the mountains followed them in their elevation, and thus, at a very 
late stage in the history of the continent, the great region of the plains 
acquired its eastward slope. In the vicinity of the forty-ninth parallel, 
these rocks have been raised almost horizontally to a height of over 
4,000 feet above the sea; to the south their elevation is even greater, 
while northward the plateau which they form falls gradually. 
It is interesting to observe that while the Cretaceous and Tertiary beds 
of the interior, have thus been raised en masse by the slow exercise of 
immense force, their broken remnants on the west coast have scarcely 
been elevated above the level of the Pacific. 
20. The details of the Laurentian and Huronian rocks receiving — 
more extended notice in subsequent pages, these need not be mentioned 
in this preliminary sketch. On their western flanks, and resting directly 
on their contorted and denuded edges, limestones of Lower Silurian age 
appear. They have been deposited tranquilly around the Laurentian 
shores, and in general still rest almost horizontally upon them, though 
they have been described as occurring much disturbed at one locality on 
the southern shore of Lake Winnipeg. Upper Silurian rocks are not 
certainly known to exist in place, though limestones of this age probably 
remain concealed by drift and alluvial deposits, and may even at one 
time have overlapped a great part of the Laurentian plateau, and have 
been continuous with those which appear to underlie the whole flat margin 
of Hudson’s Bay on the north-western side of the same Laurentian region. 
The best known exposure of the Lower Silurian limestones is near the 
Stone Fort, on the Red River, twenty miles south of Lake Winnipeg. 
It was examined as long ago as 1848 by Dr. Owen, then engaged in a 
Geological Survey of the Northern Territories of the United States. He 
concisely describes the limestone as “of a light buff colour, sometimes 
mottled, spotted, or banded, with light brown,” and in his report gives 
the most extensive list of the fossils yet made, and figures some of them. 
The list includes seventeen forms, but—unless some mistakes in the refer- 
ence of these has occurred—shows a rather mixed fauna, but one which, 
according to Dr. Owen, agrees with that of the lower beds of the Upper 
Magnesian limestone of Wisconsin, and may therefore be taken as repre- 
senting the Trenton. 
Dr. Hector also gives a short list of fossils collected at the same place, 
in his report. 
The limestone is highly magnesian, and afforded Dr. Shumard, who 



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