64 G M. DAWSON ROCKY MOUNTAIN REGION IN CANADA 



A distinct tendency to parallelism of the strata or foliation with adja- 

 cent borders of the Cambrian system has moreover also been noted in a 

 number of cases. This might imply that the foliation was largely pro- 

 duced at a time later than the Cambrian, but the materials of some of 

 the Cambrian rocks show that the Shuswap series must have fully as- 

 sumed their crystalline character before the Cambrian period, and there 

 are other evidences of their extensive pre-Cambrian erosion. It seems, 

 therefore, probable that the foliation of the Shuswap rocks may have 

 been produced rather beneath the mere weight of superincumbent strata 

 than by pressure of a tangential character accompanied by folding, and 

 that both these rocks and those of the Cambrian were at a later date 

 folded together. In the Archean of eastern Canada, foliation still nearly 

 horizontal or inclined at low angles, often characterizes considerable 

 areas and appears to call for some explanation similar to that above 

 suggested. 



The greatest thickness of the Shuswap rocks so far measured, where 

 there is no suspicion of repetition, on Kootenay lake, is about 5,000 feet, 

 but even here there are doubtles included considerable intercalations of 

 foliated eruptives. The Shuswap series characterizes considerable areas of 

 the Selkirk, Columbia, and adjacent ranges in the southern part of British 

 Columbia. It is known also in the Cariboo mountains and near the 

 sources of the North Thompson and Fraser, about latitude 53°.* It is 

 again well developed on the Finlay river, where the country has been 

 geologically examined, between the 56th and 57th parallels of latitude.f 



Northward to this point these rocks appear to be confined to a belt 

 lying to the west of the Laramide range and to come to the surface seldom, 

 if at all, in that range. Farther north similar rocks occur in the Yukon 

 district in several ranges lying more to the west, but still with nearly 

 identical characters, in so far as they are known. J 



The granitic rocks of the Coast ranges are probably much newer, nor 

 have any crystalline schists yet been observed in association with these 

 raeges to which an Archean date can be definitel}^ assigned. 



Cambrian 



The importance of rocks assigned to the Cambrian in the Rocky 

 Mountain region of Canada has become much more apparent as the 

 result of later explorations. Their thickness is very great, and they 

 appear under differing characters in different parts of the region, in 



♦Annual Report, Geol. Surv. Can., vol. xi (N. S.), p. 39 D. 



t Ibid., vol. vii, p. 33 C. 



X Ibid., vol. iii, p. 34 B, and vol. iv, p. 14 D. 



