[dowling] eastern BELT OF THE CANADIAN CORDILLERAS 181 



and Flathead b^ds now forming the summits of the mountains in the 

 Crowsnest coal field. The land deposits of the Kootenay formation 

 also include coal measures and are largely composed of coarse sedi- 

 ments. Their thickness is estimated at about 6,000 feet while the 

 conglomerate series above them is placed at a maximum of 6,500 

 feet.^ The amount of material piled on the marine floor of Jurassic 

 sediments in the west was thus from 12,000 to 13,000 feet,^ but in 

 the Foothill section it is only 1,500 feet,^ showing that the mass had 

 a wedge-like section. It is assumed, therefore, during the deposition 

 of these beds, a subsidence took place which approximated 13,000 

 feet or more. The character of the débris is also an indication of 

 the nearness of the source of supply and we can conceive of either a 

 land mass produced by an upwarp and, therefore, giving a low gradient 

 for the transport of material produced by its denudation or, a bodily 

 elevated fault block fronting a subsided surface. The second con- 

 ception seems the more probable, especially in view of the break 

 already mentioned as forming the dividing line between the two 

 parts of the Rocky Mountains. Its position in the district is a few 

 miles west of the deposits discussed and, therefore, it is claimed as 

 the mechanical instrument responsible for the building of the wedge 

 of coarse debris. It seems reasonable to assume movements at this 

 fault line as early as the beginning of the Cretaceous with probably 

 a major period of movement at the close of the Kootenay period. 

 The amount of material removed from the uplifted area is so far in 

 excess of that removed from the area to the east that an early sub- 

 jection to erosion is a necessary postulate and it is put forward here 

 that the western Rockies appeared first in M id- Cretaceous time, 

 although earlier uplifts of the same mass are no doubt indicated in 

 the conglomerates of the Kootenay which are so persistent and 

 extend as far north as the Smoky River coal basin. 



The former extent of the Elk conglomerates can only be con- 

 jectured as in the process of mountain building they have been 

 removed, north of the locality cited. They probably occupied the 

 foot of the wall formed by the normal fault which divides the moun- 

 tain mass and would be limited by its extent and probably by the 

 amount of displacement. It may be that a large part of the dis- 

 placement, especially to the north, occurred during the deposition 

 of the Kootenay measures and that to the northward the movement 

 recorded by the Elk conglomerates was limited in amount. 



^Guide Book No. 9, p. 24, Geol. Surv., Can. 

 "Sumrn. Rep. 1900, p. 90A, Geol. Surv., Can. 

 'Memoir 31, p. 34, Geol. Surv., Can. 



