145 



Dr. N. L. Bowen's Agassiz series, noted on page 258, is 

 probably part of the same great geosynclinal. 



Permian System. 



As yet rocks of Permian age are known only in the 

 Rocky Mountain portion of the railway section. There 

 Shimer has shown that the Upper Banff shale is to be so 

 dated. With a thickness of 1,400 feet (427 m.) it lies 

 conformably upon the Rocky Mountin quartzite. Dr. 

 Allan summarizes the character of the formation on page 

 183. 



Triassic System. 



No formations referable to the Triassic are known in 

 the railway section across the Rocky, Purcell, Selkirk, and 

 Columbia Mountain ranges. On the other hand, Triassic 

 rocks are extensively developed in the western half of the 

 Cordillera, where they have had a volume comparable to 

 that of the Cache Creek phase of the Pennsylvanian. 

 Dawson proved the lower Mesozoic age of his Nicola group, 

 which still covers large areas in the Belt of Interior Plateaus. 

 The greater part of this group is constituted of basic vol- 

 canic rocks (chiefly basalts and diabases) with thin inter- 

 beds of limestone carrying Triassic fossils. The upper 

 members of the group are referred to the lower Jurassic. 

 Dawson estimated the total thickness at the Thompson 

 river to be 13,500 feet (4,115 m.), of which at least nine- 

 tenths represents volcanic rock. On account of the 

 extraordinary massiveness of the lavas, it has as yet 

 proved impossible to make a trustworthy columnar section 

 for the group. 



Thick fossiliferous shales of Triassic age have been 

 found in the Cascade range just south of the railway at 

 Harrison Mills, 61 miles (98 km.) from Vancouver. The 

 Boston Bar argillites, occurring between Lytton and Hope, 

 have recently been shown by Dr. Bowen to be of Mesozoic 

 age and may also belong to the Triassic. 



Jurassic System. 



Excepting those noted in the Nicola group, no Jurassic 

 fossils have been discovered in our section west of the 



