328 B. WILLIS — LEWIS AND LIVINGSTON RANGES, MONTANA 



such moderate width between mountains of such height that no simple 

 condition of alluvial accumulation seems appropriate. It is possible 

 that the lake was at times shallow like a flooded river. It is probable 

 that it was some time reduced to the proportions of a river. It is cer- 

 tain that during considerable intervals some areas were marshes ; but, 

 admitting that a lake may pass through various phases of depth and 

 extent, the term lake beds best describes these deposits. 



PLEISTOCENE (f)— KENNEDY GRAVELS 



The typical occurrence of Kennedy gravels is illustrated in figure 2, 

 plate 51. There one may note the size and form of the constituent boul- 

 ders and pebbles, the incoherent water-washed nature of the gravel 

 shown by the' slopes, the level top which falls into the horizon line of 

 the Plains, and the elevated position of the gravel mass. This gravel 

 mesa lies just 5 miles east of the top of Chief mountain, north of and 

 900 feet above North Fork of Kennedy creek. It is isolated, and equaled 

 in height among the outlying hills only by a ridge of Cretaceous sand- 

 stone about 100 feet higher and two miles west of it. The gravel rests 

 on Benton shales, which give rise to many landslides. The Kennedy 

 deposit at' this point is something more than 100 feet thick, but its base 

 cannot be accurately placed. 



Mr Finlay examined this gravel with care, and the following data are 

 compiled from his notes. The gravel composing the mesa is well 

 rounded or subangular. No striated stones were observed. Boulders 

 two feet across occur, but are rare. Others from 6 to 12 inches in diam- 

 eter are common. Finer gravel and gravelly soil make up the mass. 

 Of the constituent rocks, limestone and quartzite are most abundant ; 

 green argillite forms about 10 per cent ; red shale is rarer ; Cretaceous 

 sandstone more common. The intrusive diorite of the Siyeh formation 

 is not represented. The gravel deposit is obscurely stratified. 



Comparing these notes with Mr Finlay's observations on glacial drift, 

 which covers the slopes 300 to 400 feet below the mesa summit and 

 thence to the creek, it appears that the Kennedy gravels and the drift 

 are alike in being composed of local Algonkian and Cretaceous mate- 

 rials, but differ in that the drift includes many striated stones, and also 

 boulders of diorite from the intrusive sheet in the Siyeh formation. The 

 latter rock does not extend in place into the watershed of North Fork of 

 Kennedy. Boulders of diorite presumably entered the drift in the lower 

 part of that valley by a course on or in the ice when it was confluent 

 with that from Swift Current valley. That the Kennedy formation does 

 not contain diorite boulders is a point in favor, of its purely local origin. 



The constituent materials, the forms of the boulders and pebbles, the 



