[camsell] great canon OF FRASER RIVER 55 



valley. The locality here referred to, however, is in the plateau 

 portion of the valley and about 80 miles above the upper end of the 

 canon. It is quite possible that the portion referred to by Dawson is 

 Miocene in age and at the same time that the caiion portion is con- 

 siderably older. 



In attempting to carry the origin of the Fraser farther back in 

 geologic time than that assigned to it by Dawson, the writer is able 

 to present some evidence to suggest the possibility of a valley along 

 the course of the caiion as far back as the beginning of Eocene times, 

 a period which brings us back to the closing events of the Laramide 

 revolution. 



The presence of bands of Lower Cretaceous sediments in the 

 Cascade range south and east of Fraser valley, and on the eastern 

 slope of the Coast range, indicates that previous to the Laramide 

 revolution a considerable depression, in which sediments were deposited 

 existed in the region of Fraser caiion and probably extended north- 

 westerly from this point along a line now occupied by the eastern 

 slope of the Coast range. It is hardly possible that at this time any 

 river system could have existed along the present course of Fraser river 

 except probably streams flowing eastward into the Cretaceous basin. 



The next outstanding event in the geological history of this 

 region is the Laramide revolution, an event which terminated the 

 existing conditions of deposition and elevated the region into a land 

 area on which stream courses would naturally be developed. The 

 effects of this revolution here were to elevate the Cretaceous into a 

 series of folds, and to develop lines of weakness along north and 

 south directions. 



The production of such lines of weakness in the solid rocks of 

 the uplifted land area was a necessary preliminary to the development 

 of subsequent stream courses along the direction of those lines, which 

 is also the direction of the greater part of the Fraser canon and of the 

 plateau portion of the valley. The conditions therefore at the close 

 of the Laramide revolution must be considered to have been favourable 

 for the inauguration of lines of drainage along the course of the Fraser 

 canon. 



The Eocene period is generally supposed to have been one of long 

 continued stable conditions during which the Interior plateau and the 

 region of the Coast ranges suffered erosion to such an extent that the 

 plateau at least was reduced almost to conditions of peneplanation. 

 An enormous amount of material must have been removed from the 

 surface of this region, carried away by streams, and deposited again 

 somewhere else. 



