86 G. M. DAWSON — KOCKY MOUNTAIN KEGION IN CANADA 



No separate record for the Permian has yet been found in this part 

 of the continent, but it must be remembered that, in view of the scanty 

 character of the paleontological evidence, strict taxonomic boundaries 

 can seldom be drawn. At about this time, however, ver}'' important 

 changes occurred, for in the Triassic a great part of what is now the 

 inland plain of the continent is found to have become the l)ed of a sea 

 shut off from the main ocean, in whicli red rocks with salt and gypsum 

 in some places were laid down. The northern part of this sea appears 

 to have extended into the Canadian region for a short distance, covering 

 the southern portion of the Laramide area. Farther north must have 

 been the land boundary of this sea, and beyond this an extension of the 

 Pacific ocean which swept entirely across the Cordillera. In the south- 

 ern part of British Columbia, however, this ocean found its shore against 

 the Gold ranges of the Archean axis, where the preceding Carboniferous 

 beds had already been upturned and subjected to denudation. The 

 Laramide region was not affected by volcanic action at this time, but 

 vulcanism on a great scale was resumed in the entire western part of 

 tlie Cordillera that had i)reviously been similarly affected in the Car- 

 bonilerous, and the ordiiKuy marine sediments there form intercalations 

 only in a great mass of volcanic products, probably in large part the 

 result of submarine eruptions. 



Such definite indications as exist of the Jurassic must, as already 

 noted, be considered as physicall}^ attached to the Triassic of the Inte- 

 rior plateau of British Columbia. It is probable that the greater part 

 of the Jurassic })eriod was characterized by renewed orogenic move- 

 ments and by denudation, for when we are next able to form a connected 

 idea of the physical conditions of the region these are found to have 

 been profoundly modified. 



It is to about this time that the elevation of the vSierra Nevada and some 

 other mountain systems in the western states is attributed. In the region 

 hereparticularl}^ described, the Triassic and older rocks of the Vancouver 

 range, or that forming Vancouver and the Queen Charlotte islands, were 

 upturned, while a similar movement affected the zone now occu[)ied by 

 the British Columbian Coast ranges. These may not have been elevated 

 into a continuous mountain system and barrier to the sea, but in any 

 case the ranges then formed were, before the beginning of the Cretaceous 

 })eriod, largely broken down b}'' denudation, so that the underlyinggranitic 

 rocks supplied abundant arkose material to some of the lowest Cretaceous 

 beds. 



It is also probable that subsidence marked the close of the Jurassic, 

 for in southern British Columbia the Pacific of the Earlier Cretaceous 

 extended more or less continuously across the line of the Coast ranges, 



