168 



DEPARTMENT OF TEE INTERIOR 



2 GEORGE V., A. 1912 



Expressed in percentages the proportions of the different kinds of sedi- 

 ments, rated according to thickness, are: — 



Rocks. 



Summit 

 Series. 



Purcell 

 Series. 



Gal ton 

 Series. 



Lewis Series 



Grit 



% 



245 



9-2 



50-1 



16 18 



002 



% 

 00 



o-o 



78-8 



20' 7 



0-5 



% 



o-o 



00 

 268 

 521 

 211 



% 



00 

 00 





14 "3 



Carbonate rocks , 



405 

 452 









ioo-o 



1000 



100 



100 



The corresponding percentages for the respective parts of each series which 

 are stratigraphic equivalents of the whole Galton series (the least complete 

 section of the four) are approximately as follows: — 



— 



Carbonate 

 rocks. 



Argillite. 



Sandstone. 



Grit. 



Conglomer- 

 ate. 



Lewis Series 



30 



20 



under 1 



55 

 52 

 25 

 18 



15 



28 

 75 

 61 







Galton Series 









Purcell Series (western phase). . . 







12 



9 



As the formations are followed eastward from the summit of the Selkirks, 

 the conglomerates and grits of the immediate shore-zone are replaced by sand- 

 stones. The sandstones are largely replaced by argillites. Finally, still farther 

 east, argillites are largely replaced by more or less impure dolomite. These 

 relations are illustrated in the synthetic diagram of Plate 21. 



The systematic character of the chemical variations encountered along 

 the east-west section of the prism is well shown in the analyses of Messrs. 

 Dittrich and Connor. Those analyses which correspond to types of contem- 

 poraneous strata in the Purcell and Rocky Mountain systems have been entered 

 in the two following tables (IH. and IV.). None of these selected analyses 

 exactly represents the average composition of a formation but each differs 

 from the corresponding average in comparatively minor degree. 



Table III. illustrates the chemical contrasts between the Kitchener quartzite 

 and its eastern equivalent, the Siyeh magnesian limestone of the Galton and 

 Clarke ranges. Cols. 1 and 3 refer to specimens collected at points about 

 eighty-five miles apart. 



