148 



of the same colour." [4, p. 151]. Owing to structural 

 complication, no attempt at a detailed section of the Cre- 

 taceous in either of the areas has yet been successful. 

 Dr. Drysdale estimates the minimum thickness of the 

 Ashcroft remnant at 5,000 feet (1,524 m.), while Dawson 

 indicated a value of 7,000 feet to 10,000 +feet (2,133 to 

 3,048 +m.) for the Fraser valley Cretaceous. A partial 

 section in the latter area (Jackass Mountain series) is 

 given by Dr. Bowen on page 258. Mr. Camsell also refers 

 certain quartz porphyry flows found west of Hope station 

 to the Lower Cretaceous. (See page 273.) 



EOCENE SYSTEM. 



In our section rocks of Tertiary age are entirely confined 

 to the western half of the Cordillera. So far as known, 

 they have originated in volcanic action or in fresh-water 

 sedimentation, though it is possible that the Eocene strata 

 of the Pacific coast are partly marine. 



The formations assigned to the Eocene are: the sedi- 

 mentary Coldwater group ; and the sedimentary Puget 

 group. These are local formations and their mutual 

 relations have not been fully determined. 



The Coldwater group, named and mapped by Dawson, 

 is probably younger and includes conglomerate, sandstone, 

 shale and coal accumulated in the valleys formed during 

 and after post-Cretaceous mountain-building. Penhal- 

 low's recent study of the fossil floras contained in these 

 beds as mapped by Dawson refers at least part of them 

 to the Eocene proper [6, p. 106]. Dawson estimated the 

 local maximum thickness of the Coldwater beds to be 

 about 5,000 feet (1,524 m.) 



Like the other Eocene groups, the Puget beds — sand- 

 stones, conglomerates and shales with thin coal beds — are 

 in unconformable relation to the Cretaceous. They attain 

 very great thickness in Puget sound. In the railway 

 section the group is truncated by the existing erosion 

 surface; the remnant of the Tertiary sediments on the 

 lower Fraser has an observed thickness of about 3,000 feet 

 (914 m.) 



OLIGOCENE SYSTEM. 



The Belt of Interior Plateaus is widely covered with 

 lavas mapped by Dawson as the ' Upper Volcanic Group ' 



