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



CHAPTER XI. 



STRATIGRAPHY AND STRUCTURE OF THE SELKIRK MOUNTAIN 



SYSTEM (RESUMED). 



Between the Pi;rcell Trench and the Selkirk Valley (Columbia river) the 

 ten-mile belt includes stratified rocks belonging to four groups in addition to 

 those forming the Summit series. (Maps No. 6, 7, and 8). These other groups 

 have been named the Priest River terrane, the Pend D'Oreille group, the 

 Kitchener quartzite, and the Beaver Mountain group. The first two groups 

 rival the Summit series in areal importance within the Boundary belt. The 

 Kitchener quartzite and the Beaver Mountain group cover but small patches 

 and their description can be given in few words. The Beaver Mountain sedi- 

 ments are intimately associated with basic volcanic rocks which in turn are 

 involved with the Rossland Volcanic group. Their description is best post- 

 poned to chapter XIII, in which the igneous rocks of the Rossland mountains 

 are discussed. 



Kitchener Formation. 



Along the western edge of the Kootenay river alluvium and north of the 

 Rykert granite opposite Porthill, the foot-hills are composed of unfossiliferous 

 quartzite and interbedded metargillite, which in lithological characters are 

 essentially like the Kitchener strata across the river. These beds are appar- 

 ently not metamorphosed in any sense different from that which is true of the 

 unfolded Kitchener quartzite of the Purcell mountains; that is, one misses in 

 "them the evidences of great dynamic metaniorphism, intense mashing, and 

 recrystallization observed in the neighbouring Priest River terrane and the 

 evidences of likewise intense contact metamorphism which has affected the 

 Priest River rocks in the batholithic aureoles farther west. The relative lack 

 of dynamic metamorphism is quite striking and largely on that account the 

 writer has separated these rocks from the Priest River terrane, postulating a 

 master fault of great throw on the west side of the Purcell Trench. This fault 

 is thus considered as bringing into contact a very old member of the Priest 

 River terrane (Belt G) and the quartzite which is tentatively correlated with 

 the Kitchener formation. The down-throw is on the east (see map), and may 

 be as much as 30,000 feet. 



On account of the great structural importance of this correlation a detailed 

 study of the sediments west of the alluvial flat of the Kootenay is imperative. 

 "While in the field the writer was not entirely conscious of the importance of the 

 lithological comparison, for at that time the existence of the Kitchener forma- 



25a— vol. ii— 17 257 



