ons REPORT UNITED STATES GEOLOGICAL SURVEY. 
part of the range and which is conspicuously displayed from long dis- 
tance to the southwest, west, and north. The area occupied by these 
rocks is probably included within a northeast-southwest belt eight miles 
long and not exceeding four miles in width, the bulk of the occurrences 
lying to the south of the Green where they also attain, perhaps, their 
greatest altitude. The outer mountain barrier crowned by these deposits 
is planed off level irrespective of the inclined position of the strata, a 
result attributable to glacial action. 
The nucleal rocks hereabout show gneissoid granite, the ledges more 
or less feldspathic and of a pale red color, at one point near head of 
lower lake dipping gently westward. Higher up the canon, the rock 
changes to a gray color, is laminated and mueh complicated by joint or 
cleavage structure. The mountain walls on either side of the entrance 
to the canon reveal the uplifted sedimentaries, which probably repre- 
sent the complete Palaeozoic series of the region. These consist in the 
first place, of typical exposures of buff, gray, and reddish stained ear- 
boniferous limestone and a buff hard sandstone, 2,000 feet or more in 
thickness, and which are apparently identical with the rocks composing 
the great ridge of Gros Ventre Peak that le twenty miles due west of 
this locality. Below the above ledge appears a heavy bed of grayish 
buff rusty-weathered magnesian limestone, 200 to 400 feet in thickness, 
and in all respects identical with the ledge elsewhere referred provision- 
ally to the Niagara epoch, although no fossils were detected in the rock 
at this locality. Below the latter otcurs a few hundred feet thickness 
of dark drab and gray rough weathered limestone, even-bedded and in 
places brecciated, resting upon a heavier series of yellowish-buff sili- 
cious beds, which probably are the equivalents of the Quebec and Pots- 
dam formations. The thickness of the sedimentary series above alluded 
to based upon rough estimates may not exceed 3,000 feet, of which two- 
thirds, perhaps more, belong to the carboniferous. 
The outer mountain declivity bears a heavy plating of carboniferous 
strata, the beds dipping north of west at an angle of 25° + —. On 
both sides of the caiion these deposits, together with the Niagara, are 
carried up forming escarped and peculiarly weathered mountain peaks 
or ridges. Between the lakes a sharp flexure arches the sedimentary 
formations, the axis of the fold being occupied by an Archean ridge that 
gradually rises to the south or southwest, in which quarter it was found 
to be quite denuded of the former rocks. Ascending the canon, east, 
the sedimentaries again rise quite uniformly or with gentle undulations, 
so that the lowest members of the series are carried to the highest ele- 
vations within perhaps a couple of miles above the upper lake on the 
north side and a less distance on the south side, beyond which the Ar- 
cheean is denuded over the remainder of the mountain plateau to the 
suminit. 
A low outflanking ridge lies close along the foot of the range, extend- 
ing from the great bend of the Green 10 miles south, where iv dies out 
in an uneven benched area. Beyond this point to the south line of the 
district the Tertiary deposits of Green River Basin impinge against the 
Archean mountain flank without intervention of older sedimentary for- 
mations. Throughout the greater length of the ridge the Triassic “ red 
beds” are displayed in frequent exposures in the slope descending to 
Green River, the interrupted section along this north-and-south line 
showing a broad, low undulation, in the axis of which Carboniferous lime- 
stones are br ought to view, as "has been elsewhere mentioned. In the 
benched area at the south end of the ridge the surface is broken by nu- 
merous sinks, the greater number of which are grassed over, although 
