This paper is an outline and summary of the salient features of the geology of the Rocky Mountain front ranges in Montana. It is based on the results of field studies by the writer, supplemented by data obtained from the literature cited.
Most of the features considered have been observed by the writer. A few areas have been examined in detail, but the exigencies of reconnaissance mapping prevented detailed work in much of the region; hence certain details of the stratigraphy, including the thickness of most of the formations, have been taken from published descriptions. The chief results of these studies have been to obtain a general knowledge of the geology of the region and to outline some of its major problems for detailed investigation. The opinions expressed should be considered tentative, for much detailed field-work must be done before many of the problems can be . . .