124. 



of bedding and schistosity are coincident. A thickness 

 of some 1,500 feet (457 m.) is locally represented in these 

 schists. They appear to be of the same horizon as a group 

 of schists exposed in still greater strength on Salmon Arm 

 of Shuswap lake; the name Salmon Arm schist may be 

 given to the member. The coarse crystallization of the 

 plainly sedimentary formation is due to the contact meta- 

 morphism of countless granitic sills and laccoliths. On 

 the cliffy slopes at the eastern end of Bastion mountain 

 the coarse schists pass up gradually into phyllite, a less 

 metamorphosed phase. 



On the slope just mentioned the Salmon Arm schists are 

 conformably overlain by the thick Sicamous limestone, 

 named for its occurrence at Sicamous station. This is a 

 thin-platy, light bluish-gray to dark gray or almost black 

 limestone, generally interrupted by closely spaced sericitic 

 films. The range in colour tints is due to variation in the 

 amount of carbonaceous matter disseminated through 

 the limestone. The rock effervesces with cold dilute acid, 

 but it is somewhat magnesian. 



The western slope of Bastion mountain is in part under- 

 lain by the Bastion schists conformably overlying the 

 Sicamous limestone These are best exposed on the shore 

 of the lake, north of Canoe point opposite Sicamous. 

 They are chiefly sedimentary phyllites but at the top are 

 green schists, apparently of volcanic orgiin. 



On Adams lake, schists like the last-mentioned rocks, 

 are conformably overlain by the composite Tshinakin 

 formation, which, in turn, is there conformably overlain 

 by a gigantic series of greenstones and green schists, the 

 Adams Lake formation, enclosing rare interbeds of lime- 

 stone and phyllite. To this youngest recognized member of 

 the Shuswap series Dawson gave the name "Adams Lake 

 series", and he regarded it as of Cambrian date and of 

 volcanic origin. More recent work has referred it to the 

 Pre-Beltian series. Dawson estimated the thickness of 

 these volcanics as 25,000 feet (7,620 m.) ; the apparent 

 thickness is certainly greater than 10,000 feet (3,048 m.). 



No complete field section has yet been found in the 

 great Shuswap terrane and several of the horizons have 

 been brought into the described relations through litho- 

 logical similarities in different sections. That principle 

 is of specially hazardous application in a region of complete 

 metamorphism like that now under consideration. The 



