126 



THE ROYAL SOCIETY OF CANADA 



taceous rocks extend farther across the Rocky mountains than at 

 any other place. 



The conditions described in an earlier part of this paper as being 

 those which preceded the action of the first compressive stresses of 

 the Laramide revolution are illustrated in Section A of both figures. 

 The Precambrian strata are taken as 14,000 feet thick, this being the 

 thickness exposed along the 49th parallel, although the base is not 

 exposed (12,m). 



Mcsozoic 

 P&lseoYoic 



Precéimbrian 



Ai, 



cscao/c 



^a/ép, 



OXOIC 



Horizontal and vertical scale of miles 



Figure 3. The progressive development of the Rocky Mountain structures 

 at the North Kootenay pass; (A) Section 1, Conditions immediately preceding 

 the Laramide revolution; (B) Section 2, Structure at an early stage in the com- 

 pression; (C) Section 3, The development of reverse faults caused by continued 

 compression; (D) Section 4, Further compression causes overthrusting, and 

 steepening of reverse faults; (E^i Section 5, Formation of 'soles' by continued 

 compression; overthrusting marked; (F) Section 6, Rotation of slices above 

 'soles' causes further steepening of reverse faults; (G) Section 7, Generalized 

 present structure ; illustrates normal faulting caused by relaxation of compression. 



