For the past six years I have been engaged in detailed studies of the geology of the Black hills and a portion of the Bighorn mountains. Considerable attention has also been given to the sedimentary formations exposed along the Rocky Mountain front range in Wyoming and Colorado. Some of the results of the work in the Black hills have been presented in previous papers and informal accounts have also been given of observations in the Bighorn and Rocky Mountain regions. In the present paper I propose to give a brief presentation of the salient stratigraphic features of the formations in the different areas and point out the regional variations which the formations present.
I think all geologists will be greatly impressed by the wonderful uniformity in most of the formations throughout the region to which this paper relates, a uniformity which indicates widespread unity of conditions in a succession . . .