REVIEWS 907 



Dawson 1 describes the geology of the Rocky Mountain region 

 in Canada. The oldest rocks of the region belong to the Shus- 

 wap series of Archean 2 age. 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 Thomp- 

 son 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. 

 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. Further 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. The Shuswap series includes highly meta- 

 morphosed sediments with perhaps the addition of contemporane- 

 ous bedded volcanic materials. They are grayish mica-gneisses, 

 with some garnetiferous and hornblendic gneisses, glittering 

 mica-schists, crystalline limestones and quartzites. Gneisses in 

 association with the last mentioned rocks often become highly 

 calcareous or siliceous and contain scales of graphite, which are 

 also often present in the limestones. These bedded materials 

 are, however, associated with a much greater volume of mica- 

 schists and gneisses of more massive appearance, most of which 

 are evidently foliated plutonic rocks, and are often found to pass 

 into unfoliated granites. The association of these different 

 classes of rocks is so close that it may never be possible to 

 separate them on the map over any considerable area. The 

 granites may often have been truly eruptive in origin, but the 

 frequent recurrence of quartzites among them in some regions 

 indicates that they are at least in part, the result of a further 

 alteration of the bedded rocks. The original bedded portions 

 of the series closely resemble those of the Grenville series of the 



'"Geological Record of the Rocky Mountain Region in Canada," address by the 

 President, George M.Dawson, Bulletin of the Geological Society of America, Vol. 

 XII, 1901, pp. 57-92. 



2 Pre-Cambrian. 



