322 B. WILLIS — LEWIS AND LIVINGSTON RANGES, MONTANA 



in the base of the Livingston range. Southeastward from Altyn the 

 limestone was traced around Point and eastern Flattop mountains to the 

 Narrows of upper Saint Mary lake. Thence it forms the base of the 

 mountains southward to an unknown distance, but it may be replaced 

 by any of the overlying formations, among which it is closely resembled 

 by the Siyeh and Carboniferous limestones. 



^ Appekunny argillile. — The Appekunny argillite is a mass of highly 

 silicious argillaceous sediment approximately 2,000 feet in thickness. 

 Being in general of a dark-gray color, 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 frequent from greenish-black argillaceous beds 

 to those which are reddish and whitish. There are several definite hori- 

 zons of whitish quartzite from 15 to 20 feet thick. The strata are fre- 

 quently 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 ranges that they may be examined with equal 

 advantage almost anywhere in the mountains. 



The Appekunny argellite 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 val- 

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

 southward to McDonald lake. 



Grinnell argillite. — A mass of red rocks of predominantly shaly argilla- 

 ceous character is termed the Grinnell argillite from its characteristic 

 occurrence with a thickness of about 1,800 feet in mount Grinnell. 

 These beds are generally ripple-marked, exhibit mud cracks and the 

 irregular surfaces of shallow water deposits. The3^ appear to vary consid- 

 erably in thickness, the maximum measurement having been obtained 

 in the typical locality, while elsewhere to the north and northwest not 

 more than 1,000 feet were found. It is possible that more detailed 

 stratigraphic study may develop the fact that the Grinnell and Appe- 

 kunny argillites are really phases of one great formation, and that the 

 line of distinction between them is one diagonal to the stratification. 

 The physical characters of the rocks closely resemble those of the Che- 

 mung and Catskill of New York, and it is desirable initially to recognize 

 the possibility of their having similar interrelations. 



The Grinnell argillite outcrops continuously along the eastern side of 

 Lewis range and its spurs, occurring above the Appekunny argillite and 



