212 



KUometres. an< ^ R° ss quartzites, it has proved very difficult 

 to map the exact contacts of these two forma- 

 tions. Nearly all the cliffs from the hotel seem 

 to be composed of the Sir Donald formation. 

 In spite of local complications, the upper 

 valley of the Illecillewaet river, including the 

 neve region, is to be considered as lying in the 

 axis of the main Selkirk syncline. This view 

 is substantiated by the easterly dip of the 

 Nakimu limestone, exceptionally well exposed 

 on Cougar mountain and Ross peak. 



The character of the Sir Donald formation 

 may be studied in the many large blocks strewing 

 the floors of the valleys above the hotel. The 

 essential similarities of the quartzitic sandstone, 

 grit, and occasional conglomerate to the differ- 

 ent phases of the St. Piran formation in the 

 Rocky mountains (Lake Louise and elsewhere), 

 are so many and so special that these formations 

 have been correlated with much confidence. 

 A general stratigraphic comparison, has in 

 fact, referred the Sir Donald and the upper 

 beds of the likewise unfossiliferous Ross quart- 

 zite to the Lower Cambrian. 



A highly characteristic feature of all these 

 formations is the abundance of bluish, opalescent 

 quartz grains and pebbles, which are also found 

 at many horizons in the Cougar formation, 

 The source of this quartz is to be found in 

 the coarse orthogneisses and pegmatites of 

 tjhe Shuswap terrane bordering the Selkirks 

 on the west. The sometimes abundant feldspar 

 grains in these sediments are microcline, 

 microperthite, orthoclase, and acid plagioclases 

 — all largely derived from the same source. 

 Mineralogical composition, general stratigraphy, 

 and field habit indicate that the Selkirk series 

 represent the northern continuation of the 

 thick Belt series of Montana and Idaho. 



In the Selkirk mountains, there can be no 

 doubt as to the conformity of the rocks here 

 referred to the Lower Cambrian with the older, 

 enormously thick mass of strata (Beltian 

 system) to be seen between Ross Peak and 

 Albert Canyon stations. 



