66 DEPARTMENT OF THE INTERIOR 



2 GEORGE V„ A. 1912 



Appekunny Formation. 



The formation immediately and conformably overlying the Altyn limestone 

 has been named the ' Appekunny argillite ' by Willis. His original description 

 applies to these rocks as they crop out in the Boundary belt and it may be 

 quoted in full: — 



' The Appekunny argillite is a mass of highly silicious argillaceous 

 sediment approximately 2,000 feet in thickness. Being in general of a 

 dark-gray colour, it is very distinct between the yellow limestones below 

 and the red argillites above. The mass is very thin-bedded, the layers 

 varying from a quarter of an inch to two feet in thickness. Variation is fre- 

 quent from greenish-black argillaceous beds to those which are reddish and 

 whitish. There are several definite horizons of whitish quartzite from 15 

 to 20 feet thick. The strata are frequently ripple-marked, and occasionally 

 coarse-grained, but nowhere conglomeratic. An excellent section of these 

 gray beds is exposed in the northeastern spur of Appekunny mountain, 

 from which the name is taken, but the strata are so generally bared in the 

 cliffs throughout the Lewis and Livingston [Clarke] ranges that they may 

 be examined, with equal advantage almost anywhere in the mountains. 



' The Appekunny argillite occurs everywhere above the Altyn lime- 

 stone along the eastern front of the Lewis range from Saint Mary lakes 

 to Waterton lake and beyond both northward and southward. It also 

 appears at the western base of the Livingston range above Flathead valley 

 and is there the lowest member of the series seen from Kintla lakes south- 

 ward to McDonald lake.'* 



At the eastern end of the South Kootenay pass the lower part of the Appe- 

 kunny includes a 75-foot band of thin-bedded magnesian limestone which is 

 identical with the staple rock of the Upper Altyn. Several other bands, each 

 a few feet in thickness, are dolomitic sandstones and grits, quite similar to the 

 beds of the Middle Altyn. The two great formations are thus transitional 

 into each other. On the other hand, the top of the Appekunny is rather sharply 

 marked off from the overlying Grinnell red beds. 



The formation as a whole is not exposed in any one section within the belt 

 covered by the Commission map. The best exposures studied occur on the 

 southern slope of King Edward peak and on the mountain slopes north and 

 south of Lower Kintla lake. A complete section was found on the ridge south 

 of Oil City, and thus outside the area of the Commission map. The total 

 thickness in these sections was estimated to be 2,600 feet. 



The dominant rock of the Appekunny is gray or greenish-gray and silicious, 

 weathering lighter gray or more rarely light greenish-gray or light rusty brown. 

 The content of silica is often so great that the rock might well be called an 

 impure quartzite. As noted in Willis' description the thin-bedded : argillite ' is 

 often interleaved with more massive strata of gray, whitish, and rusty- weathering 



* B. Willis, Bull. Geol. Soc. America, Vol. 13, 1902, p. 322. 



