sr. JOHN.|] UPPER PORTION OF GRAND CANON OF SNAKE RIVER. 197 
exposures of probable J urassic¢ strata, showing alternations of variegated 
clays and indurated beds resting upon the Triassic red sandstones, the 
whole uniformly dipping south of west. The exposures, however, for 
some distance, appear along the strike of the strata, the section present- 
ing the following lithologic appearance, as seen from the east side of the 
river, the vertical spaces being roughly estimated : 
Section west side of Snake River, in the Grand Canon. 
No. 1. Red sandstones; Trias. 
No. 2. Drab clays, a heavy bed, 200 feet or more; Jura. 
No. 3. Ledge of dirty gray rock, probably limestone. 
No. 4. Clays, with indurated layers, 100 feet. 
No. 5. Drab and chocolate-red clays, alternating with brown and gray 
sandstone and limestone layers, 100 feet. 
No. 6. Chocolate-red and drab clays, 100 feet. 
No. 7. Heavy ledge of light gray rock, probably limestone, 40 feet. 
No. 8. Drab and chocolate-red clays, 40 feet, with a bed of gray lime- 
stone (?), 15 feet. 
The exposures along the east side of the river in this vicinity are 
much less satisfactorily revealed. In the neighborhood of the placer 
mines along the little stream draining the west slope of John Day 
ridge, the following Jurassic strata underlying the Gryphwa bed appear: 
Half a mile above the debouchure of the gulch there appears a ledge of 
drab, fragmentary limestone, containing fragments of Ostrea (2), a small 
gasteropod, and segments of the the column of Pentacrinites, underlaid 
by drab and chocolate-red variegated shales and earthy butf-weathered 
limestone, dipping about W. 15° S., at an angle of 38°. Underlying the 
above occurs a heavy bed of drab indurated calcareous shales, with frag- 
ments of a chambered shell resembling Ainmonites, also fragments of a con- 
chifer, Pentacrinites, &c. Then follows a ledge of softish butf-gray, mag- 
nesian (?) limestone, with pink calcite seams, dip 43° southwest, followed 
by a heavy bed of gray, reddish tinted quartzitic sandstone, weathering 
rusty reddish, and changing to red, laminated sandstone below, dip 37° 
to 40°, W. 20°98. The latter red sandstones belong to the Trias. They 
occur in a belt of rugged, outlying ridges along the toot of the John Day 
ridge, whose crest, as already stated, is composed of Carboniferous rocks, 
tlhe limestone and siliceous débris of which is plentifully scattered over 
the lower slopes and incorporated with the soi], which is largely derived 
from the breaking up of the Jura-Trias deposits. 
The latter section of strata is the same as that mentioned in connec- 
tion with the sections east of Stations IX and XI ridge. In the extension 
north of the Grand Cation it probably constitutes a belt of Mesozoic 
strata continuous with that noticed the previous season at Station XL, 
in the Snake River Mountains. Further, as was at that time surmised, 
it appears highly probable that these formations are faulted in the lat- 
ter quarter—the western border ridge of the Snake River Mountains 
corresponding in geologic structure and in its disturbed condition to the 
John Day ridge in the southwest portion of the present district. The 
Mesozoics were there found to be overlaid by a great thickness of drab, 
buff, and variegated pale red deposits, the same as above noticed west 
of Station XI, and there as here the deposits apparently abut against 
the Carboniferous along the line of the fault. It will thus be seen that 
this faulted condition, in the areas here alluded to north and south of the 
Grand Cafion, has an extent of at least 60 miles; its southeasterly ex- 
tension in the Wyoming Range was defined by Dr. Peale the previous 
