H7 



Rocky mountains. In that range itself the rock system 

 is represented by the Fernie shale, with a thickness of 

 1,500 feet (457 m.). Its description is briefly given by 

 Dr. Allan on page 184. 



Cretaceous System. 



Following the orogenic disturbances near the close of the 

 Jurassic, sedimentation in our section became restricted 

 to relatively narrow geosynclines or zones of overlap. A 

 thick mass of Cretaceous strata was deposited in a down- 

 warp along the eastern limit of the Cordilleran area. Other 

 local geosynclinal prisms were developed near the line of 

 the present Pacific coast. The stratigraphy of each of 

 these two sedimentary provinces needs separate treatment. 



In the eastern Rockies, west of Bankhead, beds lying 

 conformably on the Jurassic Fernie shale and all of Lower 

 Cretaceous age, have been subdivided into three formations: 

 the Lower Ribboned sandstone, the Kootenay Coal measures 

 and the Upper Ribboned sandstone. Their respective 

 thicknesses are approximately: 1,000 feet (305 m.), 2,800 

 feet (853 m.), and 550 feet (168 m.). On page 185 is to 

 be found Dr. Allan's description of the formations. The 

 railway section does not give the full thickness of this 

 geosynclinal, to which Dawson has credited a value of 

 more than 11,000 feet (3,353 m.). 



Six hundred kilometres (370 miles) farther west, Lower 

 Cretaceous rocks again appear in the section. They cover 

 two principal areas: one at Ashcroft, the other following 

 the Fraser valley north and south of Lytton. Both groups 

 of rocks are doubtless remnants of a single geosynclinal, 

 once covering part of the Belt of Interior Plateaus as well 

 as part of the Coast Range region. A still greater remnant 

 has been mapped at the 49th parallel section under the 

 name Pasayten series, of which the Lower Cretaceous 

 members alone have a thickness of about 7,000 metres. 



The erosion remnants at Ashcroft and Lytton consist of 

 highly indurated sandstones, argillites and conglomerates. 

 "The sandstones are most commonly of greenish-grey 

 colours, passing on one hand into coarse, distinctly green 

 rocks, largely composed of arkose materials derived from 

 the older [Paleozoic and Triassic] greenstones and [late 

 Jurassic] granites; on the other, into fine-grained blackish 

 sandstones, which grade down perceptibly into argillites 



