218 REPORT UNITED STATES GEOLOGICAL SURVEY. 
exposures lying a little to the north of the axis of the north fold and 
' sloping off to the northeastward at a moderate angle of inclination. 
The middle sandstone member of the Carboniferous, which is well- 
developed in the latter quarter, is conspicuous on account of its red 
color. In this respect it presents a marked contrast to the lithologie 
appearance of the same horizon noted towards the opposite extremity 
of the range, in the vicinity of Gros Ventre Peak, and which might lead 
to its being mistaken for the Triassic “red beds,” were its stratigraphical 
associations locally masked or not recognizable in distant views, such 
with which the geologist too often has to be content. 
The Jura-Trias occupies a relatively wide belt on the north flank of 
the range, even rising into quite prominent tables and foreland benches, 
descending in long inclines, and merging into the area of the basin 
proper. The Jura was hardly touched at a single locality in this quar- 
ter, its presence being determined chiefly from the lithological appear- 
ance and sequence of its exposures. It seems to be in part made up of 
deep drab and chocolate-red variegated clays, sandstones, marly indu- 
rated layers, and drab limestone. Owing to the prevalence of clayey 
constituents the exposures are seldom satisfactory. On the contrary, 
the deep-red arenaceous shales and sandstones of the Trias are exposed 
in numerous and extensive escarpments, and wherever in the region of 
its occurrence the soil from one cause or other has been disturbed, a 
gleaming spot of red color, may be contrasted with the deep-green of 
herbage-clothed slopes, discloses its presence. 
