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



CHAPTER XIV. 



FORMATIONS IN THE MOUNTAINS BETWEEN CHRISTINA LAKE 

 AND MIDWAY (Middle part of Columbia Mountain System). 



General Description. 



As one crosses the Kettle river-Christina lake valley he immediately 

 encounters, in the Boundary belt, a new formation which does not appear in 

 the Rossland mountains. It consists in a thoroughly metamorphosed, highly 

 gneissic granite batholith, here named for convenience, the Cascade gneissic 

 batholith. The eastern limit of this body, marked as it is by the strong valley 

 occupied by lake and river, is also a natural dividing line between the rock 

 formations. The batholith belongs, in fact, to a complex of formations which 

 centre about the ' Boundary Creek mining district,' just as the formations 

 east of Christina lake centre about the Rossland mining camp. Within 

 the five-mile Boundary belt the formations occurring between the lake and the 

 mountain slopes just east of Midway are believed to be all of pre-Tertiary age. 

 The Midway (volcanic) formation, described in the next chapter, seems to be 

 clearly referable to the Tertiary. It covers a relatively large area at and west 

 of the town. We may therefore appropriately place the western limit of the 

 area discussed in the present chapter, at the eastern limit of the Midway 

 formation. (See Maps No. 9 and 10.) 



For the information hero published regarding this area the writer is very 

 largely indebted to the printed preliminary reports on the geology of the 

 Boundary Creek mining district, by R. W. Brock (Summary reports of the 

 Director of the Geological Survey of Canada for 1901 and 1902). Mr. Brock 

 spent nearly all of two arduous seasons in a detailed geological study of the 

 Boundary belt (here about 13 miles broad) between Grand Forks and Midway. 

 It seemed therefore inadvisable for the present writer to attempt a thorough 

 survey of this stretch. He has, accordingly, simply made two rapid traverses 

 across the mountains between the towns mentioned, so as to attain a general 

 acquaintance with the rocks as described by Mr. Brock. In addition, the writer 

 has made closer studies of the rocks between Christina lake and Grand Forks 

 as well as of the Midway volcanics. It is quite possible that most of the rocks 

 occurring between Grand Forks and Christina lake are much older than any 

 of the formations which are volumetrically important in the area described 

 by Mr. Brock. Partly for this reason as well as to preserve in some measure 

 the east to west order of treatment which is being followed in this report, the 

 formations of the Christina range will be first described. There will follow 

 an abstract of Mr. Brock's results which are here recorded as seems best to 



3Y7 



