218 



Kilometres °^ ^ e roc ^ s °f tne Shuswap terrane until the 

 revolution which flexed the Rocky Mountain 

 Geosynclinal into the folds of the Selkirk 

 range. 



The thoroughness of the static metamorphism 

 suffered by the orthogneiss is very striking. 

 In part the completeness of the recrystallization 

 of the granite may be explained by burial 

 under the enormous mass of geosynclinal sedi- 

 ment, but it should be noted that similar 

 metamorphism is shown in the Shuswap 

 orthogneisses far to the west where the Beltian- 

 Cambrian strata were, apparently, never de 7 

 posited in great strength. It seems probable 

 that the advanced static metamorphism of 

 the older Shuswap rocks was already accom- 

 plished in pre-Beltian time. 



At this section along the railway track, 

 one can see samples of the many aplitic and 

 pegmatitic dykes cutting the orthogneiss and 

 schists beneath it. The abundance of these 

 igneous intrusions here, together with their 

 entire absence in the adjacent Beltian strata^ 

 is one of the leading proofs of an important 

 erosion unconformity at the base of the Selkirk 

 series. 



From the noth mile-post, near Albert 

 Canyon, to Shuswap station, 116 miles (186-7 

 km.) farther west, the railway runs almost 

 entirely over the Shuswap terrane. For the 

 first 30 kilometres the line crosses a dominantly 

 igneous phase of the formations composing this 

 second principal province of the Canadian Cor- 

 dillera. Biotitic and hornblendic orthogneisses 

 are the chief rock types until the Columbia river 

 at Revelstoke is reached. These metamorphosed 

 granites are all pre-Beltian but show different 

 dates of intrusion. The oldest masses observed 

 are generally hornblendic and are sills cutting 

 coarse sedimentary (?) mica schists; or are 

 larger bodies (batholiths?) without clear indica- 

 tion of shape. The hornblendic granites seem 

 to have been statically metamorphosed into 

 gneisses at an early date, for the younger, 



