28 



THE ROYAL SOCIETY OF CANADA 



Tabular History of Selkirk and Rocky Mountain Systems in Southern 



British Columbia 



Selkirk Mountains 



Period 



Rocky Mountains 



Uplift of peneplain . . Eocene Orogenic movements (Lar- 



amide Revolution). 



[Tertiary Paskapoo Freshwater sedimentation. 



Peneplanation Toj (Edmonton. .. .Brackish and freshwater 



Late Maturity (final) | Bearpaw. . . . .Marine sedimentation. 



Batholith unroofed'l Upper Cretaceous.^ Belly River. . .Brackish sedimentation. 



Colorado Marine sedimentation. 



Upper Blair- 



more Subaerial sedimentation. 



Early Matur ty J (Lower Blair- 



Youth (initial). . . .\ ^ ^ "^ -j more Subaerial sedimentation. 



[Kootenay. . . .Subaerial sedimentation. 

 Possible Initiation off 



Orogenic Move- { Upper Jurassic Marine Sedimentation. 



ments I 



Stable Marine Con-j Devonian and Carboniferous Marine sedimentation.' 



dition 1 



Stable Marine Con-| Lower Palaeozoic Marine sedimentation. 



dition \ 



In early Tertiary, the Laramide revolution took place, causing 

 an uplift of the Selkirk mountains and the formation of the Rocky 

 Mountains. The effect of this uplift in the Selkirks was to slowly 

 raise the old land surface formed during the Cretaceous almost to its 

 present height, with the natural result that the streams which mean- 

 dered over the old surface were rejuvenated and cut their present 

 valleys into the old peneplain. As these streams bore no relation to 

 the underlying structures, the valleys cut by their rejuvenated de- 

 scendents, the present main valleys of the range, bear no relation to 

 structure. Thus the main valleys of the Selkirk range have been 

 carved during the Tertiary and Quaternary out of a peneplain 

 which was formed during the Cretaceous and early Tertiary periods. 

 Such has been the origin of the Purcell trench which contains Kootenay 

 lake. 



