54 THE ROYAL SOCIETY OF CANADA 



Pacific coast the origin and history of its canon are therefore very 

 important in so far as the development of the drainage of the interior 

 is concerned. In view of the fact also that some of the rock formations 

 of Cenozoic age are not represented in that region a complete history 

 of the course of development of this part of Fraser valley is necessary 

 to obtain a full outline of the geological history of the region. It is very 

 evident, however, that because the physiographic history of Fraser 

 valley is dependent to a large degree on the course of geological events 

 in the surrounding region a study of the physiographic history of 

 Fraser canon must be carried on conjointly with that of the geology. 



Up to the present no attempt has been made to work out a com- 

 plete history of the origin and development of the canon though brief 

 statements bearing on this have been made by both Selwyn and 

 Dawson in former publications of the Geological Survey. 



Selwyn ^ on the evidence of the high level terraces in the interior 

 of British Columbia, suggests that a series of large lakes existed in 

 that region, and that the removal of a rocky barrier by which one of 

 these lakes was confined resulted in the formation of the canon of 

 Fraser river. The terraces referred to are of post-Glacial origin 

 and consequently according to this idea the canon of Fraser river 

 must also be of post-Glacial origin. This view is clearly incorrect, 

 because the canon shows undoubted evidence of occupation by glacial 

 ice during that period. Other evidence to be presented later is also 

 opposed to this view. 



G. M. Dawson ^ in a later report carries the origin of the Fraser 

 farther back in the geological history of the region when he states that 

 "its valley, originally excavated in Tertiary times, in the rocky sub- 

 stratum of the country was subsequently, during the Glacial period, 

 largely filled with drift material, through which, at a still later date, 

 the river had to excavate its bed leaving great series of terraces or 

 benches along its banks in many places." 



In a later report on the Kamloops Map Sheet ^ Dawson fixes the 

 date of origin much more closely, when he states that "the excavation 

 of the great valleys now occupied by the Fraser and Thompson rivers 

 is believed to have been accomplished wholly or almost wholly in the 

 interval between the close of the Miocene Tertiary and the beginning 

 of the Glacial period." He also cites the case of horizontal Miocene 

 sandstones and basalts above Pavilion creek, cut through by the 

 Fraser river, as evidence in support of the post-Miocene age of the 



1 Report of Progress, 1871-72, p. 55. 



2 Geol. Surv. Can., Annual Report, 1887-88, Pt. R., p. 25. 

 *Geol. Surv. Can., Annual Report, 1894, p. 302B. 



