234 REPORT UNITED STATES GEOLOGICAL SURVEY. 
only uncovered later Mesozoic deposits along the downthrow side of the 
fracture line, above which towers the denuded Archean in escarped 
mountain walls a thousand feet and more in height. That these distur- 
bances occarred prior to the deposition of the supposed Wahsatch Ter- 
tiary strata is evident from the fact of the occurrence of the latter in 
their original horizontal position only a few miles to the south, well up 
in the slopes outlying the Archean wall that there defines the western 
border of the range. 
The sections on an accompanying plate present the general facts re- 
lating to the above-mentioned Paleozoic remnant occurring on the west 
flank of the range vicinity of Green River Cafion, while the extent of 
area which they at present occupy is approximately shown on the geo- 
logical map. But in respect to the outlying Mesozoic ridge, it is evident 
that the deposits occurring therein have still intimate connection with 
the Mesozoic area filling the depression between the Gros Ventre and 
Wind River Ranges in the interval just south of the great bend of the 
Green. Apparently the same series of ‘‘red beds” recurs on the outlying 
slopes of the latter range immediately north of the debouchure of Green 
River, where, however, they are concealed for the most part beneath the 
morainal materials that heavily cover the divide between the main stream 
and a smaller tributary that issues from the mountains four miles to the 
north. At the latter locality “red beds” are seen resting directly on the 
Archean border of the mountain, recalling the previously-mentioned 
similar occurrences observed by Mr. Perry in the mountain flank seven 
or eight miles south of Green River Canon, in the vicinity of Station 
XVI. Along the lower abrupt descent of the tributary that crosses this 
outlying morainal bench, red conglomerate deposits were observed, dip- 
ping steeply northwards, which strikingly resemble the Tertiary con- 
glomerate along the south flank of the Gros Ventre Range at the inter- 
section of Hoback Caton ridge, described in a preceding chapter. To 
the noeth, still, the Quaternary deposits increase in importance as an ele- 
ment in the superficial geology of the broad outlying slopes that descend 
to the west and form the watershed between the Green and Gros Ventre 
drainages. This divide region is apparently largely made up of ‘Tertiary 
formations, and their presence here seems to justify the inference of the 
former connection of the waters, in which at least the earlier Cenozoic 
measures were contemporaneously deposited over the ground that now 
belongs to two separate drainage systems. 
Itis difficult to say to what extent the Mesozoic barrier has been eroded 
within the time belonging to the present era or the Quaternary, and in 
view of the geological movements that are known to have continued into 
late Cenozoic time, the meager knowledge at present possessed hardly 
warrants conclusive statements as to the relations of the present physi- 
eal conditions to what obtained during the deposition of the early Ter- 
tiary formations in the area above alluded to. This will be understood, 
perhaps, with greater clearness from the following statement of facts: 
The Carboniferous occurring in the axis of the low inter-mountain fold on 
the Green has an altitude of about 7,800 feet, or 1,100 feet lower than the 
divide between the Green and Gros Ventre 8 miles north, and only about 
2,300 feet below the highest altitude of the latest Tertiary deposits oe- 
curring in the great watershed north of Union Peak. Lf we assume the 
whole Mesozoic series of the region to have been intact at the commence- 
ment of the Wasatch epoch, the interval now occupied by the bed of 
Green River must have presented a barrier of equal if not greater actual 
elevation than that of the Gros Ventre Mountains to-day, which may well 
have isolated, then as now, the drainage basins occupied respectively by 
