62 



a more subdued type characterized by rounded ridges and 

 dome-shaped summits, the average elevation rarely exceed- 

 ing 5,000 feet (1,524 m). The principal valleys constitute 

 a well marked longitudinal and transverse system which 

 serves as boundaries of subdivisions on mountain groups. 

 The most striking features of the Selkirk system are the 

 Purcell trench occupied by Kootenay lake and the Selkirk 

 valley occupied by Columbia river, and the connecting 

 transverse valley occupied by the West arm of Kootenay 

 lake and its westward extension, Kootenay river. 



GENERAL GEOLOGY. 



The main geological divisions are briefly classified in 

 the following table of formations. The smaller geological 

 units, however, have been omitted on the route maps owing 

 the scale of publication. 



Table of Formations. 

 Quaternary. .Glacial and Recent. 



Tertiary . 



Mesozoic . 



fMiocene Midway volcanic group. 



lOligocene Kettle river formation, Rossland 



alkali granite and syenite, Val- 

 halla granite. 



.Jurassic ? .Nelson batholith. 



(Rocks range from granite to 



gabbro). 

 Monzonite. 

 Carboniferous and 

 Post-Carboniferous.. . .Rossland group. 



Rocks largely of igneous origin. 

 It includes the Brooklyn and Raw- 

 hide formations and the Knob 

 Hill group at Phoenix; the 

 Mount Roberts formation and 

 the augite porphyrite series at 

 Rossland. 

 Carboniferous (?) Pend d'Oreille group. (Metamor- 

 phosed sediments in great part). 

 Slocan series. (Slates, argillaceous 

 limestones and quartzites). 



Cambrian (?) Selkirk series. 



Pre-Cambrian Shuswap series. (Schists, ortho- 

 gneisses, etc.). 



Palaeozoic. . 



PRE-CAMBRIAN. 



The Shuswap series is the oldest known terrane in 

 British Columbia. It consists of a series of gneisses, 



