REPORT OF THE CHIEF ASTRONOMER 133 



SESSIONAL PAPER No. 25a 



the area already shows signs of systematic variation in the staple rock-types. 

 As the section is carried farther eastward the changes become more and more 

 marked, until, in the angle between the two forks of the Yahk river, the forma- 

 tion has attained what may be called its eastern phase. 



In the meantime the total thickness seems to diminish so that at the Yahk 

 river, where the top and base are both represented, the Kitchener measures 

 not more than 6,2-00 feet in thickness. As with the western phase the passage 

 to the underlying and overlying formations is not abrupt and it is impossible 

 to be certain of an exact figure. In any case the thickness is believed to be 

 close to 6,000 feet at the Yahk river. 



Along the west fork of the river great thicknesses of the strata assigned 

 to this phase of the Kitchener are still so similar to the rocks of the western 

 phase that there can be no reasonable doubt that it is the one great formation 

 reappearing on the eastern side of the twelve-mile interval. This view was 

 corroborated by finding these beds developed in their proper relations to the 

 typical Moyie and Creston formations. 



The chief differences between the eastern and western phases are two in 

 number. Though the feldspathic quartzite still persists, its vertical continuity 

 is yet more signally broken by intercalations of metargillite which gradually 

 increase in importance as the sections lead eastward. At the same time a wholly 

 new ingredient or pair of ingredients appears in the formation. Many beds 

 of the metargillite and even some of the more quartzitic f acies betray an acces- 

 sory amount of calcium carbonate which causes effervescence on the application 

 of cold dilute acid to the specimens. Magnesium carbonate is present but, as 

 in the Creston formation, is not so abundant as the calcium carbonate. 



Finally, on the ridge running south from the Boundary line along the right 

 bank of the west fork of the Yahk river, strong interbeds of somewhat silicious, 

 magnesian limestone with typical molar-tooth structure occur among the still 

 dominant quartzites and metargillites. The exposures are nowhere all that 

 could be desired but there seems to be no doubt that at this locality, the car- 

 bonate rock forms several beds. As the section is carried eastward, these beds 

 increase rapidly both in number and thickness, with a simultaneous decrease 

 in the amount of more purely silicious strata. 



About halfway between the two main forks of the Yahk and three thousand 

 yards north of the Boundary line, a thick bed of molar-tooth limestone, which 

 crops out again at the line, has afforded the specimen illustrated in Plate 10. 

 This bed is, microscopically, at any rate, a good type of the molar-tooth rock 

 so characteristic of the Siyeh formation. Along the Commission trail on the 

 west slope of the McGillivray range, several hundred feet of this more or less 

 impure limestone are well exposed at several points. 



Finally, the character of the Kitchener strata still further eastward has 

 become so far modified that the molar-tooth limestone and highly calcareous 

 metargillites must total 1,000 feet or more at the Kootenay river opposite 

 Gateway. 



