THE CRETACEOUS PERIOD. 



165 



time cannot always be distinguished from faulting of later date. 

 In the Rocky mountains of British Columbia, one overthrust fault 



LewisSJange 



Fig. 403. — Section in northern Montana, showing Proterozoic rock, A, thrust over 

 Cretaceous, K. Subsequent erosion has removed much of the overthrust beds, 

 but Chief Mountain is a remnant of them. The extent of the overthrust is 

 unknown. , 



has been located which crowded the Cambrian rocks obliquely 

 up over the Cretaceous. The horizontal displacement is estimated to 



Fig. 404.— Chief Mountain. (Willis, U. S. Geol. Surv.) 



be as much as seven miles/ while the throw is as much as 15,00C 

 feet. Near the national boundary, the displacement of what appears 

 to be the same fault crowded the Proterozoic up over the Cretaceous 2 

 by a movement of equal magnitude (Fig. 403). The exact date of 



1 McConnell, Geol. Surv. of Canada, Vol. II, Rept. D, p. 33, 1886. 



2 Willis, Bull. Geol. Soc. of Am., Vol. 13, pp. 307, 331-5. 



