alts REPORT UNITED STATES GEOLOGICAL SURVEY. 
season. It is not improbable that the exceedingly complicated belt men- 
tioned by Professor Bradley * in the Grand Canon, in which the strata 
are tilted and disturbed in an extraordinary manner, involving Carbon- 
iferous and Mesozoic beds, was caused by proximity to the disturb- 
ances that produced the great faults of the John Day and Salt River 
ridges. But it will have been made apparent from the observations 
along the divide between John Day’s and Salt rivers, in the neighbor- 
hood and east of Station XI, recorded in foregoing pages, that only one 
well defined anticlinal arch was found in the region lying between the 
John Day ridge and the similarly faulted Carboniterous monoclinal 
mountain that forms the northern terminus of the Salt River ridge. 
The ground traversed in ascending the Snake Valley to the mouth of 
Hoback’s River has already been reported upon by Professor ae 
who accompanied the Snake River expedition of this survey in 1872. 
This part of the valley has a general northerly direction, and though 
hemmed by hills it hardly deserves the name canon. At intervals 
the valley expands, affording narrow tracts of gravelly bottom-land, 
covered with willows and grass plots, and beautiful clamps of Menzies 
spruce, aspens, and cottonwood; the hillsides being clothed with pine 
and the ordinary fir-trees. Interesting examples of terrace formations 
are also met with in these valley expansions, the highest reaching 250 
feet above the river-level. At one point the terrace declivity shows a 
thickness of 15 feet of horizontally stratified pebbles and bowlders at an 
elevation of about 100 feetsabove the intervale, which is cemented into 
a quite firm conglomerate. The terraces slope gently towards the cen- 
ter of the valley, their steep declivities being strewn with the thoroughly 
water-worn rock fragments which are identical with the materials pav- 
_ing the present shoal river-bed. These consist chiefly of quartz, with 
some granitie and other rocks, rarely a volcanic bowlder. Pieces of ob- 
sidian were found mixed with the terrace gravel, which were doubtless 
derived from the region of the Upper Snake or from the watershed, 
many miles to the northeastward. The Snake in this part of its course 
often occupies a wide, sheal bed, which at this season (August) exposes 
extensive bars of shingle and cobble-stones, amidst which the stream 
winds in many channels. The views from the higher terraces, com- 
manding long reaches of the river hemmed by disconnected terraces and 
the more rugged low mountain borders, are extremely beautiful. The 
trail along the left bank was found in good condition for the pack-train, 
and, save at one or two points, without serious obstacles in the way of 
making a wagon road. For railway purposes the valley and Grand 
Cation offers a feasible route between the lower valley of the Snake 
and Jackson’s Basin. 
For three or four miles the valley is bounded on the east by the John 
Day ridge, in which the Carboniferous ledges are steeply tilted, inclin- 
ing at an angle of 50° to 70° south of west. The mountain-foot termi- 
nates in a steep talus composed of light and flesh-tinted quartzitic sand- 
stone and gray limestone débris. In the outlying slopes occurs a brown- 
weathered gray shaly limestone, containing a few obscure fossils, which 
Dr. White refers to the young of Ostrea. Fiom this evidence it would 
appear that these beds probably belong to aremnant of the Jura, or pos- 
sibly a later formation, the stratigraphical relations of which are not 
well made out at this locality, more than that they overlie the Carbonit- 
erous. At a locality a short ‘distance higher up the valley, the foot of 
the mountain is covered with rusty red. and brown weathered, bluish 
and greenish gray sandstone débris, which probably belongs to the same 
ee a eel 
*U.S. Geol. Survey, Hayden, report 1872, p..268. 
