Oelecle Wada Wee 
GROS VENTRE BASIN. 
Gros Ventre River drains a large basin tract lying to the north of the 
mountain range bearing the same name, and which is about twice the 
superficial extent of the upper basin of the Hoback on the south of that 
range. ‘To the southeast it is defined by the low, inconspicuous divide 
stretching over from the north slope of the Gros Ventre Range, east, 
to the great foreland bench on the west flank of the Wind River Range 
‘south of Union Peak; the elevated water-shed that spans the gap be- 
tween Union Peak at the northern terminus of the latter range and the 
great sedimented volcanic mountains in the vicinity of Towotee Pass, 
a distance of 24 miles, constitutes the barrier on the east between this 
drainage and the upper course of Wind River; while it is separated from 
the valley of Buffalo Fork by the low mountainous highlands dominated 
by Mount Leidy, which form the northern boundary of this special drain- 
age basin. Thus defined, the Gros Ventre Basin has an area of 500 
square miles, approximately. 
The main stream rises in a glaciated defile a few miles south of Union 
Peak, and once it emerges upon the elevated park-like slopes at the foot 
of the latter mountain, it pursues a general course a little north of west 
for the distance of about 42 miles to the point where it gains the plain of 
Jackson’s Basin. It receives several good-sized tributaries from the 
surrounding highlands, and is of additional importance from the fact 
that it affords easy communication with the Wind River Valley Via 
Union Pass at the north end of the Wind River Range. Chiefly occu- 
pied by easily eroded tertiary deposits, the general superficial contour, 
of the basin is exceedingly broken, especially in the central and north- 
ern portion. The streams generally flow in narrow valleys, often deserv- 
ing the name “cations”; lower down the main valley expands, affording 
small tracts of intervale and terrace land. The uplands present pleasing 
variety of forest and herbaceous openings in the undulating southeast- © 
ern quarter, where the woods and meadows were found stocked with 
numerous bands of elk and deer. Butin economic importance it scarcely 
equals the beautiful basin of the Hoback (its general elevation being in 
the neighborhood of a thousand feet higher), save in one particular, its 
extensive deposits of coal. 
Geologically, the area above alluded to constitutes but a part of the 
great Cenozoic basin that stretches north until it is lost beneath the lava 
flows and volcanic ejectamenta that mask the whole country around 
Yellowstone Lake. Its present orographic boundaries are, on the west, 
the Téton Range; south, the Gros Ventre Mountains and the northern 
end of the Wind River Range; to the north and east, except for the 
presence of the probably isolated uplift on Buffalo Fork, described in the 
report on the Téton district the previous season, it has an extent reach- 
ing far beyond the limits of the present district. 
It is not the province of this special report to attempt the detinition 
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