204 REPORT UNITED STATES GEOLOGICAL SURVEY. 
is made up of alternations of soft, in places friable, sandstones of a 
grayish-buff color, including coarse-grained and conglomeritic layers, 
interbedded in the soft drab or blue and variegated dull chocolate-red 
clays, in quite horizontal position. The nature of the deposits, which 
re eadily decompose at the surface, renders their outcrop obseure save 
along the streams, where they appear in low bluff exposures. The infe- 
rior portion of the series, as it is here developed, becomes more clayey, 
like Wasatch deposits lower down the Green. The 'same beds reappear 
along Lead Creek, and they apparently constitute the great sloping 
benches that rise high up on and even invest the broad summit of the 
eastern portion of the Wyoming Range in the vicinity of the south line 
of the district. The benches here alluded to constitute the divide be- 
tween Lead Creek, which flows into Green River near our south line, 
and the ultimate source of Hoback’s River, which rises just south 
of Hoback’s Peak (Station VI), in the Wyoming Mountains, and hence 
they belong to the before-mentioned water-divide. The whole upland 
region, as also the terraces and stream-beds, are strewn with drift mate- 
rials mainly composed of quartz rock with occasional granitic and lime- 
stone bowlders. But these superficial deposits become less prevalent 
in the western portion of the basin in proportion to the greater distance 
the remove from the loftier mountain elevations that lie to the east. 
The view from the divide-ridge looking towards the western mountain- 
border south of Hoback Cation, shows the Tertiary gently upraised along 
the eastern outlying ridge of the Wyoming Range. As has been else- 
where stated, these deposits, here constituted of ight grayish slightly 
calcareous sandstones and clays, incline off the monoclinal ridge of steeply 
dipping, non-conformable Jura-Trias at angles of inclination varying from 
15° to 45° eastward, gradually flattening out towards the center of the 
basin. The soft deposits are seldom well exposed, the comparatively 
smooth, herbaceous-covered slopes here as elsewhere contrasting with 
the densely timbered surface of the more rugged mountain declivities. 
The unconformity of these deposits is well displayed at the forks of the 
Hoback 3 or 4miles above the cation, where their most westerly exposures 
are reached. In the west side of the valley the Triassic red sandstones 
appear, dipping to the southwestward, while in the same side low out- 
liers of the later deposits cling to the foot of the mountain slopes, and 
on the opposite side of the stream they form a considerable elevation in 
the bluff face of which several hundred feet thickness of the soft sand- 
stones and clays are seen, dipping eastward at angles of 30° to 45°. 
South of the latter locality, the Tertiary deposits rapidly rise in eleva- 
tion, and finally surmount the mountain summit, in the neighborhood 
of the south boundary of the district. In the latter quarter, these de- 
posits incline eastward at a much gentler angle; but as this -part of 
the Wyoming Range was not visited, their relations to the underlying 
Laramie formations, which Dr. Peale recognized still farther south, was 
not determined. It is improbable that the latter formation appearsin the 
central portion of the Hoback Basin; not, however, that it does not ex- 
ist there, but because it is concealed beneath the equally vast accumu- 
lations of Tertiary strata that fill the basin. Neither are the limits of. 
the Tertiary deposits well-defined in the angle between the Hoback 
Cation ridge and the Gros Ventre Mountains, where they are covered by 
erratic materials that in places deeply bury the foot of the mountain and 
outlying slopes., But the slopes soon merge into the benches descend- 
ing into the lower level of the basin, which in places disclose the Ter- 
tiary strata apparently inclined in a northerly direction or towards the 
mountain. 
