[schofield] rocky MOUNTAIN TRENCH 69 



lower, middle, or upper, and above the unconformity separating those 

 strata from the Archaean. In places the Cambrian rests with apparent 

 conformity on the Beltian but Walcott holds that a regional study 

 proves a stratigraphie and time break between the known Pre- 

 Cambrian rocks and Cambrian sediments of the North American 

 continent. Daly^ does not admit the presence of the unconformity 

 between the Cambrian and the Beltian of Walcott in the Canadian 

 Cordillera; a full discussion of this problem from Daly's point of view 

 is given in the above memoir. Daly- uses the term Beltian to include 

 those "strata lying conformably below the Olenellus zone, as well as 

 the rocks which are synchronous with those strata though not in 

 proved conformity with the Olenellus zone. In this paper the question 

 will not be discussed as it is considered irrelevant, but the writer's 

 conclusions^ on the problem are that such an unconformity exists 

 between the Cambrian and the Pre-Cambrian and hence agrees with 

 Walcott. It is with Walcott's interpretation that the Beltian is used 

 in this paper. 



The Belt Series* in southern British Columbia in the vicinity 

 of the Rocky Mountain trench is as follows : 



Middle Cambrian Disconformity 



[ Roosville formation 1,000 feet 



I Phillips formation 500 " 



I Gateway formation 2,000+ " 



Belt Series J Purcell Lava formation 300 " 



Siyeh formation 4,000 " 



Kitchener formation 4,500 " 



Creston formation 5,000 " 



[ Aldridge formation 8,000+ " 



Base unexposed 



A columnar section of the Beltian in the Selkirk Mountains along 

 the Canadian Pacific Railway is given by Daly:^ 



Top Erosion Surface Approximate 



Thickness 



Lower Cambrian | Sir Donald quartzite 5,000+feet 



Rossquartzite (upper part) 2,750 " 



1 Daly, R. A., Geol. Surv., Can., Mem. 68, 1915, p. 87. 



2 Daly, R. A., Geol. Surv., Can., Mem. 68, 1915, p. 58. 



3 Schofield, S. J., Geol. Surv., Can., Mem. 76, 1915, p. 41. 



* Schofield, S. J., Geol. Surv., Can., Mem. 76, pp. 25 and 42. 

 «Daly, R. A., Geol. Surv., Can., Mem. 68, 1915, p. 61. 



