216 REPORT UNITED STATES GEOLOGICAL SURVEY, 
East of Station XIII the southern flank of the north flexure has been 
almost entirely removed by erosion, only limited exposures in the foot 
of the mountain preserving part of the curved strata. Along this part 
of the mountain the high outlying slopes show here and there limited 
exposures of the arenaceous ‘red beds” that form a belt continuous 
with the Triassic deposits occurring a few miles to the westward of Gros 
Ventre Peak, of which mention has already been made. At the present 
locality these deposits appear to be little disturbed ; their inclination, al- 
though varying from northerly to southerly, perhaps does not exceed 
an angie of 10°, Their position at the foot of the mountain is not favor- 
able to the determination of their relations to the Carboniferous deposits 
occurring in the latter, while on the south they are soon concealed beneath 
the Tertiary deposits that here gently rise up in the northern terminus 
of the Green and Hoback water-divide. It is possible that the uplift at 
this point was accompanied by a fault, with downthrow on the south, 
amounting in vertical extent to about the thickness of the carboniferous 
formations. 
Soon after crossing the Hoback-Green divide, in the vicinity of the 
lake source of a stream flowing south into Green River, the Carbonif- 
erous limestone, here highly siliceous, forms a low, broad areh, with 
gentle inclination both north and southwards. The limestone appears 
over a considerable area in the low, hilly and undulating wooded coun- 
try immediately south of the sandstone-capped eastern prolongation of 
Gros Ventre Peak ridge, at the foot of which lies the above-mentioned 
little lake-basin, partially environed by the sandstone and limestone 
cliffs. Thence eastward, this ridge steadily declines, flattening out into 
one of the low divides terminating on the west side of Green River Val- 
ley, about 8 miles distant. ‘The Station XIII, or north fold of the range, 
is not traced with certainty but a short distance east of the lake, and it 
seems probable that it also dies out in that direction. 
The west side of the stream flowing south into Green River is bor- 
dered above by bluffs composed of the “ red beds,” and lower down by 
the rather abrupt east face of the main divide separating the drainage 
of the Green from that tributary to the Hoback, and which is here made 
up of Tertiary deposits. Perhaps 3 miles south of the lake limited ex- 
posures of Jurassic sandstone and calcareous deposits appear in the 
gentle slopes on the east side of the valley, dipping about 25° south, 
and containing Pentacrinus, Ostrea, and Belemnites. The way thence 
leads southeasterly over low, undulating divides in the country interven- 
ing between this stream and the Green. The only rock exposures met 
with in this section consisted of occasional outcrops of drab clays and 
reddish-buff, thin-bedded, rather hard sandstone. These rusty-weath- 
ered sandstones continued nearly to the Green, forming low ledges here 
and there in the grassy slopes, and uniformly ‘inclined about south, at 
angles of 20° to 35°. “Lithologically they bear intimate resemblance’ to, 
and are probably identical with, horizons elsewhere referred to the 
Laramie. They are apparently in conformable superposition to the Ju- 
rassic deposits occurring to the north, which further suggests the above- 
inferred identity, unless they prove to belong to an intermediate Creta- 
ceous formation. But the latter formation was not recognized here, and 
in the absence of fossils our acquaintance with its stratigraphical com- 
position is too imperfect to warrant its recognition in obscure outcrops. 
The most southerly observed exposures of the above-mentioned Lara- 
mie(?) sandstones occur in the uplands on the west of Green River, 
about 3 miles northwest of an isolated Tertiary butte that rises from 
the plain on the opposite side of the river, or about 11 miles above the 
