58 THE ROYAL SOCIETY OF CANADA 



by way of Okanagan valley, and it appears fairly certain that the 

 head waters of certain streams, to the north of the Fraser, that flowed 

 westward through the Coast range in broad valleys were diverted by 

 the uplift and became part of the Fraser drainage. 



The occupation of the Fraser canon by glacial ice is clearly 

 proven by the effects of that occupation. The effect of valley glacia- 

 tion would be to change the sharply V-shape caused by the Pliocene 

 uplift to a more broadly U-shape, to truncate projecting spurs and 

 straighten the course of the valley and probably to deepen it some- 

 what. Another effect also would be the development of hanging val- 

 leys in the streams tributary to the valley. All of these features are 

 exhibited in it. 



There is little doubt that Fraser valley throughout was more or 

 less deeply filled with glacial material at the close of maximum glacia- 

 tion, and in the canon itself a considerable thickness would have been 

 deposited in the broader parts while in the constricted parts there 

 was little room for such accumulations. This filling was presumably 

 brought about when the general level of the region, above the sea, 

 was considerably lower than at present. 



The evidence of a re-elevation of the region since Glacial times 

 is shown on the Pacific coast by abandoned beaches up to 400 feet 

 above sea level, and is clear throughout the canon and in the valley 

 higher up. This elevation again revived the stream causing it to cut 

 down through the accumulations of glacial material leaving merely 

 remnants on either slope of the valley in the form of terraces or benches. 

 In many places the stream has cut down to its old rock floor, and in 

 the gorge itself and on the Thompson river has cut into that floor to 

 a depth of about 100 feet, leaving rock benches on one or both sides of 

 the old valley. The post-Glacial notching of the old glaciated valley 

 floor in the gorge and not in the valley above and below implies a 

 warping up of the surface across the course of the gorge and along 

 the axis of the Cascade-Coast mountain uplift. This is equivalent to 

 saying that the Coast and Cascade ranges have risen relative to the 

 sea and probably to the Interior Plateau region also since Glacial 

 times. 



Another feature of the post-Glacial uplift has been the develop- 

 ment, in the gorge, of a second set of breaks in some of the tributary 

 valleys entering it. Hanging valleys had previously been developed 

 by the action of valley glaciers where the streams plunged down over 

 falls to the main valleys, and where these streams ran over a rock 

 bench in the main valley they plunge again in falls over the bench 

 to the bottom of the recently excavated gorge. While the upper break 



