314 B. WILLIS — LEWIS AND LIVINGSTON RANGES, MONTANA 



back from the channel of the stream to a distance of from 2 to 5 miles 

 with an ascent by terraces and irregular slopes to foothills of the Living- 

 ston range on the east. The drift deposits extend above an elevation of 

 5,000 feet, and about that level present east and west profiles of a flat 

 character, suggesting that the deeper part of the valley was once occupied 

 by ice or gravel, and the space between it and the mountains was filled 

 to a comparatively smooth surface. • 



The presence of the drift at so great an elevation carries the profile 

 from the valley to the rocky heights of the Livingston range with a 

 much gentler grade than would be the fact were the drift removed. It 

 appeared from a brief examination of Camas, Logging, Bowman, and 

 Kintla lakes that the face against which the drift is piled was limited 

 along a line extending across the several valleys from southeast to north- 

 west after the fashion of a definite scarp, and upon this apparent fact 

 in part is based an inference as to the structural relation of the Flathead, 

 valley and the Livingston range. 



Stratigraphy 



general statement 



The strata encountered in that part of the Front range of the northern 

 Rockies to which this article refers belong to five great periods of geo- 

 logic history, separated by immense gaps. The oldest are sediments of 

 pre-Cambrian age, in large part at least, with possibly some early Cam- 

 brian strata. They have an aggregate thickness of more than 12,500 

 feet. Carboniferous limestone was observed in a small area in the Gal- 

 ton range west of Flathead valley, on Yakinikak creek, and although it 

 is absent from the Front range near the 49th parallel, it occurs to the 

 northwest and southeast as well as west, and probably extended over 

 the entire range. Strata of Cretaceous age occur extensively in the 

 Great plains and in the valleys which penetrate so deeply into the east- 

 ern slope of the Lewis range. Lake beds of Tertiary age, either of Mio- 

 cene or Pliocene date, are exposed in the bluffs along the North fork of 

 Flathead river. East of the Front range on the foothills of the great 

 promontories overlooking the Plains, and on the highest levels of the 

 Great plains themselves, there are coarse gravel deposits of stream-worn 

 material, which apparently antedate any glacial formations of the region, 

 and may be Pliocene or early Pleistocene. Finally, the latest episodes 

 of development are recorded in glacial drift, partly brought down from 

 the valleys and partly deposited by the great continental glacier which 

 spread from the northeast over the Plains toward the base of the Rockies. 

 Closely related to all of that portion of the history which is of post- 



