[schofield] 



ROCKY MOUNTAIN TRENCH 



91 



seen at present. It is evident from a study of the modern drainage 

 system that the east-flowing Cretaceous rivers of the eastern highland, 

 eroded headwards until before the close of the Cretaceous they had 

 penetrated through the ancient highland and were draining the 

 interior basin. Much rearrangement of the drainage would take 

 place at this time but at present nothing is known concerning it. 

 It is probable that the ancestral rivers of the modern Liard and Peace 

 were present in Cretaceous times, as well as the ancestors of those 

 streams which flowed eastward through the Yellowhead, Kicking- 

 horse, and Crowsnest Passes, but have since disappeared for the most 

 part. The Columbia, Kootenay, and Okanagan Rivers in southern 

 British Columbia as well as the Fraser River have an ancestry in the 

 Cretaceous epoch although they have passed through many changes 

 during the successive periods. A rough idea of the distribution of 

 these Cretaceous rivers is given in Figure 3. 



Geo/o^/cdl Survey. Canada. 



Figure 3 



At the close of the Cretaceous, as mentioned above, the two main 

 highlands as well as the Interior Plateaus were in a state of old age or 

 peneplanation which was characterized by a rolling landscape over 

 which the rivers meandered sluggishly. At the close of the Cretaceous, 



