st. soHN.] JOHN DAY BASIN—EAST FLANK SALT RIVER RIDGE. 195 
into deep ravine, apparently impinging against the faulted Carbonifer- 
ous deposits in the east flank of the Salt River ridge. 
The conglomerate ledges mentioned under No. iG) of the foregoing sec- 
tion are undoubtedly identical with bed No. 18 of the preceding section 
east of Station LX; also the vertically-upraised sandstone beds, 19 and 
20 respectively of the two sections, are doubtless the same ledge. The 
latter horizon marks the site of a sharp synclinal flexure, into which the 
strata are wedged and so crushed together as to render the determina- 
tion of the exact character of the fold extremely difficult. The dark- 
blue shales included in No. 20 are not dissimilar to the supposed Bear 
River Laramie shales, No. 7, farther east, while the limestone, No. 22, 
found on the summit contains a small univalve shell resembling similar 
imperfectly-preserved forms occurring in Jurassic limestone beds de- 
scribed under the preceding section. The latter inference and surmised 
identity of the deposits in question, if well founded in fact, indicate a 
fracture or fault in the strata at this point, which must have taken place 
during the folding of. the beds into the anticlinal of Station XI, and 
which latter movement was probably closely synchronous with that 
concerned in the upheaval of the neighboring parallel ridges of this 
mountain belt. 
The western slope of Station XT descends with steepening abruptness 
imto a deep depression largely filled with grayish deposits (No. 24), on 
the farther side of which rises a more prominent mountain mass belong- 
ing to the ridge bordering the east side of Salt River Valley and prop- 
erly considered as the northern terminus of the mountain ridge bearing 
the same name. In the abrupt eastern face of the latter mountain a fine 
section is exhibited, the lower two-thirds or more, based on the Carbon- 
iferous gray limestones, capped by a few hundred feet thickness of red 
arenaceous deposits, constituting the summit. Although the latter de- 
posits bear lithologic resemblance to the “‘red beds” of the Trias, they 
may prove to belong to the red sandstone horizon forming the middle 
member of the Carboniferous series of the region. The strata in the lat- 
ter mountain ridge dip to the westward, the general exposure as seen 
from Station XI being along the strike of the strata, and in places ex- 
tensively barred, though much eroded, by drainage. action. Between 
this mountain and the confluence of John Day’s River and the Snake, 
at the lower entrance to the Grand Cajion, a belt some 5 miles across 
intervenes, which is known to be composed largely, if not. entirely, of 
Carboniferous deposits, an account of which was given by Professor Brad- 
ley in the report of this survey for 1872. To the south, in the adjoin- 
ing district, Dr. Peale found the same deposits extensively developed 
in the southern continuation of this mountain ridge, where they form a 
synclinal depresgion. 
There can be little doubt that the strata composing the latter moun- 
tain ridge are faulted, the Carboniferous beds having been forced up 
into a position high abov e those pertaining to the Mesozoic and Laramie 
epochs which flank the ridges west of Stations IX and XI, descending 
into the valley of John Day’ s River. The condition of things referred 
to is sufficiently clearly interpreted in the diagram of the foregoing sec- 
tion, which, together with the diagrams of sections farther to the east, 
afford a comprehensive view of the structural features of this mountain 
zone in the territory immediately south of the Grand Cation of the Snake. 
From the above account of the observations made in this region, it will 
have appeared that the work of exploration was carried nearly across 
the Wyoming Range; indeed, the results practically give a connected 
section across this portion of the range, between the upper basin of the 
