262 REPORT UNITED STATES GEOLOGICAL SURVEY. d 
thickness of variegated chocolate-red and drab deposits. Butin the up- 
lands on the opposite side of the valley, over which the road to Camp 
Brown leads, the horizontal Tertiary sandstones are again met with. 
Mention has already been made of some fossiliferous sandstone oceur- 
rences, of probable Tertiary age, in the debouchure of Jake’s Creek. 
These exposures are practically horizontal and fill a depression eroded 
out of the tilted Jura-Trias at the foot of the Wind River Mountains. 
Below this the Tertiary area is crowded to the north side of Wind River 
and is not again met with on the south side of the stream until reaching 
Campbells Fork, nine or ten miles to the east-southeast. At the latter 
locality a series of nearly horizontal drab and dirty-yellow soft sand- 
stones appears in the blufis bordering the stream for a mile or more, and 
which extend up the valley to a place nearly opposite the head of the 
lake, where they abut against the upraised Triassic “red beds” in the 
mountain flank. The same deposits occur in the bluff borders along all 
the deeper drainage channels that flow down from the Wind River 
Mountains between Campbell’s and Bull Lake Forks, where they hold 
the same unconformable relations to the outlying Mesozoic belt at the 
foot of the mountains. But in the interval between North Fork and 
Campbell’s Fork, where the outlying Mesozoics are projected beyond 
the mountain-foot in a sort of broad, low arch, across the outer edge of 
which the main stream has eroded its channel for several miles, the va- 
riegated red and drab deposits rest immediately upon the unconforma- 
ble older formations without intervention of the above-described Tertiary _ 
sandstones. It may be urged that the latter sandstones hold a strati- 
graphie position superior to the variegated deposits, in which case it is 
evident that the heavy lignite-bearing series of supposed Wasatch Ter- 
tiary occurring in the Gros Ventre Basin just over the watershed at the 
head of Wind River, if not wanting, is so attenuated as to escape recog- 
nition in the denuded borders of the lower Wind River Basin. | 
Bull Lake Pork, immediately it leaves the mountains, exhibits an un- 
usally clear section of the Tertiary sandstones. They here occur very 
much in the same manner as on Campbell’s Fork, impinging at a sharp 
angle against the inclined Cretaceous strata occurring in the outlying 
bench at the foot of the mountains. The highest exhibitions of these 
strata occur in the bluffs about opposite the head of Bull Lake and between 
600 and 700 feet above the water-level, the beds showing slight easterly 
inclination in the direction of the basin. Perhaps a mile lower down, 
on the north side of the lake, a section showing a vertical thickness of 
about 400 feet in this horizon was examined. 
Section of Tertiary strata on Bull Lake. » 
No. 1. Unexposed slope to level of Bull Lake, 145 feet. 
No. 2. Coarse, dirty-yellow sandstone, containing pebbles of metamor- 
phic rocks and pockets of green clay, exposed 25 feet +. 
No. 3. Soft, almost incoherent dirty-yellow sandstone, with thin layers 
of green clay and small coneretions; fragments of fossil-wood in upper 
part, 259 feet +. 
No. 4. Buff, coarse-grained, soft sandstone, with greenish arenaceous 
clays below, heavy-bedded above, and containing regular and irregular. 
shaped sand and ferruginous sand concretions, 125 feet exposed. 
No. 5. Brownish-yellow clay or soil, 20 feet +L. 
No. 6. Slope occupied by irregular parallel ridges of morainal mate- 
rials reaching up into summit 700 feet above level of Bull Lake. 
The Tertiary beds are planed off even with the tilted edges of the 
