iad 
st. soun.] LITTLE WIND RIVER CANON. 251 
the basin Tertiary series described in following pages under the head of 
Wind River Basin. 
No. 21. Pliocene, or possibly Post-Tertiary, conglomerate, resting 
upon the planed-off edges of the unconformable subjacent Mesozoic 
strata, attaining a thickness of 30 to 50 feet, gently sloping in the direc- 
tion of the basin. The deposit is here mainly made up of water-worn 
limestone and sandstone pebbles, evidently derived from the adjacent 
mountain, few, if any, metamorphic fragments occurring in the deposit, 
which is more or less firmly cemented. This deposit reaches well up on 
the outlying slopes, in places resting upon the Trias. 
The Tertiary and Post-Tertiary occurrences briefly alluded to in the 
foregoing section in the vicinity of Sage Creek, are further mentioned in the 
chapter devoted to the consideration of the Wind River Basin deposits. 
The fossiliferous Jurassic sandstone, No. 13, is an interesting occurrence, 
definitely establishing the age of the series of variegated arenaceous and 
argillaceous strata with which it is associated. It is impossible in the 
present lack of paleontological evidence bearing on the question to de- 
cide where the line of demarkation between this series and the Triassic 
should be drawn. It is probable, however, that the upper limestone, 
No. 10, pertains to the Jura, in which case the inferior buff and reddish 
sandstones would fall into the horizon of the passage beds, offering a some- 
what marked resemblance to the lithologic appearances remarked in this 
horizon in the region above Campbell’s Fork. The upper member of the 
Cretaceous was not recognized at this locality, the uplands lying to the 
east of the Colorado shales, being occupied by the Pliocene (?) conglom- 
erate formation which masks the older strata upon which it rests. 
Little Wind River debouches from the mountains a little north of the 
parallel 43°, opening a wide gap across the sedimentary plated mountain 
ridge, exposing to view an exceedingly rugged Archean region outlying 
the main erest of the range at the heads of both the North and South 
Forks, as seen from the valley near Camp Brown. Just without the foot 
of the mountain the main stream forks, each branch penetrating the in- 
terior of the range independently, and where they break through the 
outer mountain ridge their courses are confined between stupendous 
walls, which disclose magnificent sections of the upraised Paleozoic 
series from top to base. In the latter respect, as also in the scenic con- 
comitants, the Little Wind River cafions are much like those men- 
tioned in preceding pages, yet with local peculiarities sufficiently strik- 
ing to arrest the attention and stimulate the desire for more intimate 
acquaintance with the locality. 
The canon of the South Fork, which lies mainly south of 43d parallel, 
appears to be the narrower of the two, though the mountain basin in 
which their sources lie is much the same. About three miles above 
the debouchure of the North Fork the stream is confined to a narrow 
defile hemmed in by steep débris slopes terminated above in vertical walls 
of Carboniferous limestone. This part of the valley is swept nearly clean 
of the morainal deposits, whose recurrence above and below exhibits some 
of the most stupendous and interesting examples of their kind. Above 
the narrows the sedimentary cliffs diverge to right and left, rising up 
into the crest of the ridge which here, as to the north, forms a rim defin- 
ing the Archean area of the elevated interior of the range. At the en- 
trance to the canon below, the Permo-Carboniferous and upper lime- 
stones outcrop in the low benches alongside the stream, but no good 
exhibitions of the junction with the Triassic “‘red beds” were met with. 
Underlying these deposits, which incline at an angle of about 12°, N. 52° 
E., the middle Carboniferous sandstone formation appears, gradually 
