60 G. M. DAWSON ROCKY MOUNTAIN REGION IN CANADA 



and, becoming less continuous and separated by wider intervening low- 

 lands, run toward the eastern boundary of Alaska. 



The geological features follow a similar rule, the rock series repre- 

 sented differing much in age and composition within comparatively short 

 distances as the Cordilleran belt is crossed, while they run far and with 

 closel}^ accordant characters in the direction of its length. 



This depends on two conditions, both imposed by the position of the 

 zone of recurrent crustal movements coincident with the western border 

 of the continent: (1) The occurrence of successive zones of deposition, 

 whether sedimentar}^ or volcanic, parallel to the continental edge ; (2) the 

 actual compression of the original area of deposition, by folding and 

 fracture, produced by pressure from the Pacific side, by means of which 

 the superficies may have been reduced by at least one- third of its original 

 width since early Paleozoic times. It results, further, from these condi- 

 tions that the local names applied to geological formations remain appro- 

 priate for long distances in the general direction of the strike, while the 

 characters associated with such names can seldom be traced far without 

 change in a transverse direction. The bearing of this on the nomencla- 

 ture appropriate for the Cordilleran region as a whole is important, and 

 the want of attention to it has already, I fear, led to the })ublication of 

 some new formational names which are unnecessary and confusing rather 

 than helpful. 



The ruling orographic features of the Cordilleran region in Canada at 

 the present time are the Rocky mountains proper, forming its high 

 eastern border, and the Coa^t ranges of British Columbia on the west. It 

 has been pro[)Ose(l by Dana to name the first of these systems the " Lara- 

 mide range," as its origin was coeval with the close of the Laramie period. 

 This mountain system appears to begin about the 46th or 47th parallel 

 of latitude, from wliich it runs in a northerly direction to the Arctic 

 ocean, with occasional echelon-like breaks, but forming throughout the 

 western limit of the inland plain of the continent. Its width is about 

 60 miles, and although reduced in the far north, the height of many of 

 its peaks exceeds 11,000 feet. The rocks composing it are for the most 

 part referable to the Paleozoic, and it is found to be affected by numerous 

 great faults parallel to its direction, overthrust to the eastward, and 

 along the eastern margin, resulting in some cases in horizontal displace- 

 ments of several miles, by which Paleozoic rocks override those of Creta- 

 ceous age in the foothills. 



The Coast ranges of British Columbia form a belt of about 100 miles 

 in width that extends' along the border of the Pacific for at least 900 

 miles, beginning near the estuary of the Fraser and eventually running 

 inland beyond the head of Lynn canal, where the coast changes its trend 



