192 DEPARTMENT OF THE INTERIOR 



2; GEORGE V.„ A. 1912 



Selkirk mountains a great thickness of rocks that have not yet yielded 

 any fossils, but appear to represent, more or less exactly, the Cambrian 

 of our typical section. Resting on the Archean rocks of the Shuswap 

 series is an estimated volume of 15,000 feet of dark gray or blackish 

 argillite schists or phyllites, usually calcareous, and toward the base with 

 one or more beds of nearly pure limestone and a considerable thickness 

 of gray flaggy quartzites. To these, where first defined in the vicinity of 

 the Shuswap lakes, the name Nisconlith series has been applied. The 

 rocks vary a good deal in different areas, and on Great Shuswap lake are 

 often locally represented by a considerable thickness of blackish flaggy 

 limestone. In' other portions of their extent dark-gray quartzites or gray- 

 waekes are notably abundant. Their colour is almost everywhere due to 

 carbonaceous matter, probably often graphitic, and the abundance of carbon 

 in them must be regarded as a somewhat notable and characteristic feature. 

 These beds have also been recognized in the southern part of the West 

 Kootenay district and in the western portion of the Interior plateau of 

 British Columbia. 



' The Nisconlith series is believed, from its stratigraphical position and 

 because of its lithological similarity, to represent in a general way the 

 Bow River series of the adjacent and parallel Laramide range, but there 

 is reason to think that its upper limit is somewhat below that assigned 

 on lithological grounds to the Bow River series. 



' Conformably overlying the Nisconlith in the Selkirk mountains, and 

 blending with it at the junction to some extent, is the Selkirk series, with 

 an estimated thickness of 25,000 feet, consisting, where not rendered 

 micaceous by pressure, of gray and greenish-gray schists and quartzites, 

 sometimes with conglomerates and occasional intercalations of blackish 

 argillites like those of the Nisconlith. These rocks are evidently in the 

 main equivalent to the Castle Mountain group, representing that group 

 as affected by the further and nearly complete substitution of clastic 

 materials for the limestones of its eastern development. 



1 In the vicinity of Shuswap lakes and on the western border of the 

 Interior plateau, the beds overlying the Nisconlith and there occupying 

 the place of the Selkirk series are found to still further change their 

 character. These rocks have been named the Adams Lake series. They 

 consist chiefly of green and gray chloritic, feldspathic, sericitic, and some- 

 times nacreous schists, greenish colours preponderating in the lower and 

 gray in the upper v parts of the section. Silicious conglomerates are but 

 rarely seen, and on following the series beyond the flexures of the mountain 

 region it is found to be represented by volcanic agglomerates and ash-beds, 

 with diabases and other effusive rocks, into which the passage may be 

 traced by easy gradations. The best sections are found where these 

 materials have been almost completely foliated and much altered by dyna- 

 mic metamorphism, but the approximate thickness of this series is again 

 about 25,000 feet. 



