143 



of the eastern Selkirks but have there been completely 

 denuded. It is highly probale that the western half of 

 the Cordillera was a land surface during the Ordovician. 



In our section the system is composed of the Goodsir 

 shales and the Graptolite shales. Dr. Allan credits 

 them with respective thicknesses of 6,040 feet (1,841 m.) 

 and 1,700 feet (518 m.). His account of them appears 

 on pages 1 79-181. 



Silurian System. 



The Silurian rocks of the section seem to have had the 

 same general distribution as the Ordovician shales. To 

 the younger system belong the Halysites beds, a formation 

 named by McConnell and described on page 181 by Dr. 

 Allan, who estimates the thickness of the formation at 

 1,850 feet (563 m.) 



Devonian System. 



Sediments of Devonian age in the railway section are 

 also confined to the Rocky mountains. The Intermediate 

 limestone, named by McConnell and described by Dr. Allan 

 on page 181 has a thickness estimated at 1,800 feet 

 (548 m.) or more. In the Sawback range it is conformably 

 underlain by the unfossiliferous Sawback formation, 3,700 

 feet (1,128 m.) thick. This is certainly post-Cambrian 

 but its exact age cannot now be declared. (See page 182.) 



Mississippian System. 



The strata formerly mapped as Carboniferous in the 

 Rocky mountains of our section have recently been shown 

 by Shimer to be partly Mississippian and partly Pen- 

 nsylvanian in age.* The former system is represented in 

 the Lower Banff limestone (thickness, 1,500 feet or 457 m.) 

 and the overlying Lower Banff shale (thickness, 1 ,200 feet 

 or 366 m.), both named in McConnell's original report. 

 [2, p. 17]. Some details concerning these will be found on 

 page 182. 



*H. W. Shimer, Summary Report, Geo. Surv. Can. 1910, p. 147. Since this 

 passage was written Dr. Shimer has concluded from palaeontological evidence that at 

 least part of the Lower Banff limestone is Devonian. 



