124 DEPARTMENT OF THE INTERIOR 



2 GEORGE V., A. 1912 



by McEvoy, Dawson, and others for these rocks, has been retained because of 

 the chemical composition and tough, massive field habit of the beds selected as 

 the types of the formation. To the writer a distinct genetic problem remains. 

 One cannot easily tinderstand the conditions under which such an immense 

 accumulation of fine quartz and feldspar particles has been made. The purely 

 argillaceous material must have been quite subordinate through thousands of 

 feet of the Creston formation. The question arises as to the mechanism by 

 which residual clay has teen thus separated from the more silicious matter. 

 Such separation is very rare, if not unknown, in the muds now accumulating 

 on the ocean-floor. The writer has failed to find in the ' Challenger ' report on 

 the deep-sea deposits an account of any mud which chemically or mineralc- 

 gically matches the Creston type of deposit. The ' Blue Muds ' of the report 

 furnish the nearest parallels and yet show vital contrasts. This problem of 

 genesis applies also to the rock forming the type of the Kitchener quartzite.* 



The micas and the accessories are chiefly the result of the crystallization 

 of a small original admixture of micaceous, argillaceous, and ferruginous 

 material in the sandy sediment. It is probable that most of the quartz and 

 of the feldspars represent clastic material cemented together by secondary 

 growths of the original crystal fragments. One of the plagioclases, referred 

 with some doubt to albite, may be of metamorphic origin. The metamorphism 

 which led to the crystallization or recrystallization was, almost without doubt, 

 not dynamic but static in nature. As in the case of the metargillites of the 

 Lewis and Galton series, these effects have resulted from deep burial with 

 consequent increase of temperatui'e and pressure. 



Professor Dittrich's analysis of a typical specimen (No. 1125) of the homo- 

 geneous quartzite from McKim cliff gave the following result — 



* While this chapter was going through the press the writer had opportunity to 

 study the Shuswap terrane, from which the clastic materials of the Creston, Kitchener, 

 and other formations composing the Rocky Mountain Geosynclinal were derived. Great 

 thicknesses of phyllites, chlorite schists, green schists, greenstones, and fine-grained 

 mica schists were found in this pre-Beltian terrane as exposed at the Shuswap lakes. 

 In general these rocks are abundantly charged with secondary quartz developed in 

 minute individual crystals (anhedra). During the secular weathering of such rocks 

 the more soluble micas, chlorite, talc, uralite, etc., would be leached out and the more 

 resistant quartz and alkaline feldspar would be washed out to sea. The writer is 

 inclined to credit this explanation of the silicious muds which have been consolidated 

 to form the thick, very dense quartzites of the Cambrian and Beltian formations. The 

 rich content of microcline and microperthite repeatedly emphasized in the descrip- 

 tions of the latter can be explained as due to the weathering and washing of the 

 millions of aplite and pegmatite dikes and sills cutting the Shuswap sediments and 

 srreen schists. These injections are associated with large batholiths of likewise pre- 

 Beltian granite; its debris is also represented in the Eo^ky Mountain Geosynclinal. 



