CORRELATION OF SECTIONS 23 



member, varies by several thousand feet in volume, showing that the old sur- 

 face was a very irregular one and had been greatly modified by denudation 

 previous to the deposition of the Nisconlith. The same circumstance has been 

 noticed by Mr McConnell in the case of the Bow River series of the Laramide 

 range, where it is found resting on the Archean in the vicinity of the Finlay 

 river, over 400 miles northwest of his typical section,* proving this denudation 

 interval to be a very important one, although, as already noted, there is often 

 a parallelism in strike between the two series of rocks." 



He then describes the general characteristics of the Bow Eiver and 

 Castle Mountain series, and then sa}'s of the Nisconlith series of the 

 western section :f 



"Passing now to the next mountain system, to the southwest of the 

 Laramide range and parallel with it — the Gold ranges — we find in the 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 lime- 

 stone 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 quartz- 

 ites or graywackes are notably abundant. Their color 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 stratigraphic position and because 

 of its lithologic 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 blend- 

 ing with it at the junction to some extent, is the Selkirk series, with an esti- 

 mated 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 



* Annual Report Geological Survey of Canada, vol. vii (N. S.), p. 24 C. 



t Loc. cit, pp. 66 and 67. 



$ Annual Report Geological Survey of Canada, vol. iv (N. S.), p. 31 B. 



Bull. Geol. Soc. Am., vol. 2, p. 170. 



Annual Report Geological Survey of Canada, vol. vii (N. S.), p. 31 B. 



Shuswap map sheet, Geological Survey of Canada. 



