204 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. 75 



Silurian sea deposited them over the impure sandstones and shales 

 of the Ordovician in the western side of the Cordillcran sea, where 

 they now form the Wonah quartzite of the Beaverfoot-Brisco-Stan- 

 ford Range, and later when the Devonian transgressing sea deposited 

 the sands now forming the Mount Wilson quartzite of the Clear- 

 water and Saskatchewan areas. 



The Beltian pre-Cambrian rocks are mainly arenaceous and siliceous 

 shales, with some fine conglomerate and more or less friable sand- 

 stone. They are unlike the superjacent Cambrian rocks except where 

 they may have furnished the material that was distributed over the 

 bottom of the Cambrian sea and incorporated in the shales and sand- 

 stones in the lower part of the Lower Cambrian. 



The limestones are persistent in character over relatively large 

 areas but they vary in amount of included arenaceous and argillaceous 

 material, in the extent of dolomitization, and in the thickness of layers, 

 which range from a thin shale to a layer several feet thick. Such 

 variations may be noted by comparing the Bow-Kicking Horse section 

 with that of Glacier Lake and even better with the Robson Peak 

 section. 



Sedimentation. — When the advancing Cambrian sea penetrated the 

 area of the Cordilleran Geosyncline, the adjoining land surfaces were 

 of low relief with only minor elevations and depressions. An excep- 

 tion appears to have existed in Kintla Island,' which was not, as far 

 as now known, covered by a post-Beltian pre-Devonian sea. The 

 impure sandstones and shales of the Beltian series of the Algonkian 

 had not been greatly disturbed or eroded since the withdrawal of the 

 great inland non-marine seas in which they were deposited, although 

 they were undoubtedly more or less decayed and disintegrated. 



That the advancing waters encountered only slight elevations in 

 and along the shores of the Cordilleran Geosyncline is evidenced by 

 the almost entire absence of coarse conglomerates, and the presence, 

 above the coarse basal sandstones and fine conglomerates, of deposits 

 of very fine-grained sandstones and mud rocks. 



As the sands and mud were gathering in the shallow Lower Cam- 

 brian sea, the Bow Trough of the Cordilleran Geosyncline was slowly 

 deepening until 4.000 feet (1,219.2 m.) or more of shallow water 

 sediments accumulated before the calcareous sediments now forming 

 the Mount Whyte limestones began to be deposited. This period 

 appears to have been sufficiently long to permit of the thorough work- 



^ Problems of American Geology, Vale Univ. Press, 1915, p. 167. 



