MESOZOIC SYSTEMS ALONG THE PACIFIC 



275 



ferred to as the Nicola series and consists largely of volcanic intrusives 

 and effusives, tuffs, and agglomerates with argillites and limestone at 

 several horizons. The total thickness in places is 10,000 to 15,000 feet, but 

 the uppermost part may be of early Jurassic age. In the vicinity of Kam- 

 loops, the Triassic beds with a basal conglomerate rest without angular 

 unconformity on Carboniferous beds, and possibly the same general re- 

 lation holds elsewhere. The Triassic strata occur also west of the Fraser 

 River, and consist of dark green massive andesite and basalt, chert, argil- 

 lite, limestone, and tuffaceous shales (Cairnes, 1936). Volcanic rocks 

 with minor amounts of sediments occupy a great part of Vancouver Island 

 and of Queen Charlotte Islands. See map, Fig. 17.18. The bedded char- 

 acter of the fragmental volcanic rocks, the presence of a few limestone 

 members which in some places are several thousand feet thick, and the 

 marine fossils found in tuffs and other sediments indicate that the gen- 

 eral assemblage is marine in origin. It seems probable that the beds formed 

 in a sea which, like that of Carboniferous time, extended over the greater 

 part, if not all, of the Canadian Cordilleran region. 



In Queen Charlotte Islands, a thick clastic series with some pyroclastic 

 material ranges in age from Late Triassic to Jurassic and grades upwards 

 into a volcanic assemblage of tuffs and effusives, 5000 feet or more 

 thick. The tuffs are fossiliferous, evidently were laid down in the sea, and 

 are of Jurassic and, presumably, Middle Jurassic age. The thick assem- 

 blage of Triassic volcanics and sediments which is widely displayed over 

 Vancouver Island and known as the Vancouver group also may be suc- 

 ceeded by beds of Jurassic age. Strata, resembling the Vancouver group 

 and related series but in places much metamorphosed, occur at intervals 

 along the mainland coast and as included masses in the granitic rocks of 

 the Coast Range. Along the eastern side of the Coast Range, within the 

 basins of Nass and Skeena rivers, is a thick assemblage of sedimentary and 

 volcanic rocks known as the Hazelton group and which, as indicated by 

 an imperfectly known flora and fauna, is of Jurassic, possibly Mid- Jurassic, 

 age. The proportions of sedimentary and volcanic material composing the 

 Hazelton group varies from district to district with some indication that 

 the nonvolcanic sedimentary rocks become more and more preponderant 

 as the formation is followed eastward from the margin of the Coast 



Fig. 17.13. Batholiths of the North 

 American Cordillera. Heavy dashed 

 lines indicate axes of anticlinoria, syn- 

 clinoria, belts, and general trends of 

 the late Jurassic and early Cretaceous 

 phase. The dashed line north of the 

 Nelson batholith is an anticlinorium in 

 Proterozoic strata and may be Lara- 

 mide in age. 



