144 

 Pennsylvanian System. 



In the Rocky mountains of our section the Pennsylva- 

 nian system includes the Upper Banff limestone, and the 

 overlying Rocky Mountain quartzite, with estimated or 

 measured thicknesses of 2,300 feet (701 m.) and 800 feet 

 (244 m.) respectively. Dr. Allan's account of them is 

 given on page 183. 



Pennsylvanian rocks show yet greater thickness in the 

 western half of the Cordillera, where they represent the 

 the oldest Paleozoic strata known in the railway section. 

 They have been named by Dawson the Cache Creek group, 

 his own description may be quoted in abstract. Writing 

 of the group as a whole he says: 



"The lower division consists of argillites, generally as 

 slates or schists, cherty quartzites or hornstones, volcanic 

 materials with serpentine and interstratified limestones. 

 The volcanic materials are most abundant in the upper part 

 of this division, largely constituting it. The minimum 

 volume of the strata of this division is about 6,500 feet. 

 The upper division, or Marble Canyon limestones, consists 

 almost entirely of massive limestones, but with occasional 

 intercalations of rocks similar to those characterizing the 

 lower part. Its volume is about 3,000 feet. 



"The total thickness of the group in this region would 

 therefore be about 9,500 feet, and this is regarded as a 

 minimum. The argillites are generally dark, often black, 

 and the so-called cherty quartzites are probably often 

 silicified argillites. The volcanic members are usually 

 much decomposed diabases or diabase-porphyrites, both 

 effusive and fragmental, and have frequently been rendered 

 more or less schistose by pressure .... 



"In the southern part of British Columbia, the Cache 

 Creek group shows some evidences of littoral conditions 

 toward the west slopes of the Gold [Columbia and adjacent] 

 ranges, probably indicating the existence of land areas 

 there." [5, p. 70]. 



Travelling westward over the railway, the Cache 

 Creek rocks first appear in a long section east of Kamloops 

 on the South Thompson river. (See page 231). The group 

 originally covered all, or almost all, of the western half of 

 the Cordillera and has been found to have a thickness of 

 at least 6,800 feet (2,073 m -) m the Chilliwack canyon, 

 near Vancouver. [11, Part I, p. 514, and Part II, p. 559]. 



