256 REPORT UNITED STATES GEOLOGICAL ‘URVEY. 
der range, the lands on the north rising in great up wd benches that 
occupy the wider interval lying between the main stre m and the mount- 
ains on that side of the basin. The upper half of the ourse of the main 
stream is eroded out of the soft Tertiary strata, the ren under ofits course 
to a point below the mouth of North Fork closely « orms to the de- 
markation between the Mesozoic and Tertiary formatio: . the latter oceu- 
pying the whole of the basin area lying to the north of t. »river. At one 
point, in the neighborhood of Du Noir or Willow C °ek, the stream 
touches the Paleozoic mountain flank, where for a short istance it fiows 
in @ narrow gorge walled by Carboniferous sandstone. 
This narrow belt of Mesozoic and Paleozoic strata alon ' the southwest 
border of the basin has already been noticed in the acec nt of the geol- 
ogy of the eastern flank of the Wind River Range, to w. ch it properly 
pertains, geologically. The stratigraphicai relations oc the two sec- 
tions are uninterrupted and most intimate; erosion in ; ‘eglacial time 
having swept away the unconformable Tertiary deposii_, exposing to 
view the older formations over quite extensive areas ii the interval 
lying between the river and the mountain flank. Durii .° the glacial 
poch, when the mourtain gorges were filled to the brim with moving 
bodies of ice, vast quantities of erratic materials were tra1 ported from 
the interior of the mountains and spread out in orderly diso: ler over the 
bared sedimentary formations in the slopes along their fo t. ‘The lat- 
ter accumulations are conspicuously displayed in the embou hures of all 
the streams that rise in the interior of the range as far sou ‘h, at least, 
as Little Wind River. But, perhaps, their most extensive e hibition is 
found in the debouchures of Bull Lake and Campbell’s Fo: ks, and on 
Torrey’s Oreek, where the drift lies scattered over broad area and reach- 
ing perhaps a thousand feet up on the mountain side, their »ccurrence 
everywhere clearly displaying their origin. Besides the hug. morainal 
ridges flanking either side of the debouching mountain valle) s, the ad- 
jacent mountain slopes are corrugated with the peculiar sh rt ridges 
composed of loose materials which were borne to their presei t resting 
places by glacial agents. 
Concerning, therefore, the remaining geologic characteristics of the 
basin area, there only remains to be noticed the great Tertiary forma- 
tions that are known to outcrop over the greater portion of its surface, 
and such Quaternary and modern deposits as were observed the present 
season. 
In a previous report, as also in preceding pages of the present re- 
port, allusion has been made to the great voleanic-capped water shed in 
the vicinity of Togwotee Pass, and in the chapter devoted to th: Gros 
_ Ventre Basin, brief mention was made of the geologic components of 
that portion of the watershed lying between Togwotee and Union asses. 
The latter forms a low mountain barrier, separating Wind Riv: ° from 
Gros Ventre drainage, and, as previously stated, it is almost e.tirely 
made up of Tertiary formations. The ridge, however, retains the vol- 
canic capping to a point perhaps 10 miles south-southeast of Togwotee 
Pass, and remnants of the same sedimented volcanic ejectamenta were 
found crowning low eminences on the summit still farther south to within 
6 miles of Union Pass trail. On one of thelatter points Station XX VIII 
was made, which has an altitude of 10,142 feet above the sea. 
Soon after leaving the summit of Togwotee Pass, the nascent stream 
begins to erode its bed into the soft deposits that underlie the great 
voleanic accumulations, and which appear in bluffs of gradually in- 
creasing height as low down as the confluence of the first considerable 
affluent from the north, just below which, or some 12 miles from its ulti- 
