2 GEORGE V, SESSIONAL PAPER No. 25a A. 1912 



CHAPTER XIII. 



FORMATIONS OF THE ROSSLAND MOUNTAIN GROUP. 



It will be recalled that, in the chapter on the nomenclature of the mountain 

 ranges, the Rossland mountain group where crossed by the ten-mile Boundary 

 Belt, is bounded on the east by the Selkirk Valley (Columbia river) and on the 

 ■nest by the meridional valley occupied by Christina lake and the lower Kettle 

 river. On the east the formations of the Rossland mountain group in several 

 instances extend over into the Selkirk system. Of these the Pend D'Oreille 

 series has already been described, as well as a few of the dikes cutting that series 

 along the western bank of the Columbia river. The Trail batholith, Sheppard 

 granite, Rossland and Beaver Mountain volcanic groups, and small bodies of a 

 peculiar porphyritic olivine syenite are represented on both sides of the Columbia 

 and will be described in the present chapter. The western topographic limit of 

 the Rossland mountain group is also, within the limits of the Boundary belt, a 

 clean-cut and convenient line of division between the geological formations of 

 the Rossland and Midway-Christina mountain groups. (See Maps No. 8 and 9.) 



Prom the Columbia to Christina lake igneous-rock formations dominate 

 very greatly. Sedimentary rocks appear only in small patches, and are nearly 

 always much deformed and metamorphosed. Though there are good reasons for 

 believing that these rocks are chiefly if not altogether late Paleozoic or post- 

 Paleozoic in age, fossils are almost as rare as they are in the formations of the 

 Rocky Mountain Geosynclinal. The writer has been able to add but little to the 

 stratigraphic information secured by McConnell, Brock, and others who have 

 made studies in the region. However, the interpretation given the few scattered 

 facts in hand differs somewhat from that adopted by these observers. 



The older sedimentary formations will be described first. They include, 

 besides the small area of the Pend D'Oreille slates, phyllites, quartzite, and lime- 

 stone near the Columbia, a small patch of obscurely fossiliferous limestone asso- 

 ciated with chert in Little Sheep creek valley: fossiliferous limestone occurring 

 with the older traps north of Rossland; an intensely deformed series of lime- 

 stones, quartzites, and schists sectioned by the railway line east of Christina 

 lake and named, for convenience, the Sutherland schistose complex; and a few 

 small outcrops of old-looking quartzite and argillitic rocks intimately associated 

 with the Rossland volcanics. 



A very limited exposure of fossiliferous (plant-bearing) argillite, probably 

 of Mesozoic age, will then be described. The youngest sedimentaries observed in 

 this part of the Boundary belt are conglomerates and sandstones which, again 

 from very imperfect fossil evidence, seem to be of early Tertiary or mid-Tertiary 

 age; these beds form four small patches at or near the Boundary line. 



319 



