184 REPORT UNITED STATES GEOLOGICAL SURVEY. 
which the structure of the ridge is fully revealed, besides affording excel- 
lent facilities for detail stratigraphical examinations. 
One of the most interesting sections across this mountain belt is that 
presented in the sides of Hoback Cation. This gorge traverses the 
ridge in a direction a little north of west, and that por tion here alluded 
to is about five miles in length. The Hoback flows in narrow defiles at 
intervals, several miles above this point.. Throughout this distance the 
south side of the eafion is closely hemmed in by steep mountain slopes, 
which are frequently broken by mural escarpments several hundred feet 
high, in which the strata are well exposed. 
At the upper entrance to this stretch of cation stands the before-men- 
tioned eastern border ridge, in which the Triassic red sandstones are 
steeply tilted, dipping westward into a synclinal depression, whose axis 
apparently is but a few hundred yards distant. The west flank of this 
synclinal rises with a more gradual ascent, bearing a heavy series of 
Jurassic deposits, which consist of a rather heavy deposit of rusty buff 
limestone, resting upon hard reddish sandstone, probably belonging to 
the upper portion of the Trias. Then succeed heavy ledges of drab lime- 
stone, associated with drab nodular and indurated calcareous shales, 
charged with quantities of Grypheea calceola, the whole dipping a little 
north of east at angles of 30° to 35°. The latter deposits are overlaid by 
a series of chocolate-red and gray, more or less arenaceous shales. In 
the latter series, at a point on the north side of the stream, a short dis- 
tance above the upper entrance to the cation, a thick bed of brownish- 
drab limestone forms a rather prominent outcrop in the slope, rising to 
the westward at an angle of 45°, finally curving over past verticality 
in the crest of the low ridge. The same flexure is also noticeable in in- 
ferior ledges lower down the cafon, though less marked than in the 
above instance. Although no fossils are detected in these higher strata, 
they are presumed to belong to the Jura, with the lower fossiliferous beds 
of which they are conformable. On the east flank of the synclinal the 
latter beds reappear, affording abundance of their characteristic fossils. 
Just east of the debouchure of a gulch heading in the north end of 
Station If ridge, the Triassic red sandstones rise up and curve over in a 
fold with sharp, in places almost vertical, inclination on the west side, 
the same deposits in the east slope of the fold dipping at an angle of 
25° north of east. Higher up the gulch the steeply-tilted ledges have 
been weathered into narrow walls, presenting interesting examples of 
atmospheric erosion. The outer plating of this west-side slope consists 
of gray ledges, probably of the age of the Jura. On the north side of 
the cation these horizons are not as well exposed, the slopes being strewn 
with red sandstone débris. In the opposite side of the eulch, a few 
hundred yards below, a heavy series of buif or pale flesh- colored and 
gray, very hard sandstone, including layers of siliceous limestone, oc- 
curs, which rises up into a fold with rather steep inclination in the east 
flank. The strata descend much more gently on the west flank of the 
fold, the ledges as seen in the exposures along the south side of the 
cafion gently undulating, until reaching a point ‘half to three-fourths of 
a mnile below the above- mentioned eulch, where they again more steeply 
rise to the westward, as shown in the mural exposures which rise 500 
to 800 feet above the ’ stream on either side. The tipper siliceous depos- 
its here occupy the crests of the ridges, and are underlaid by a heavy 
series of grayish-drab, more or less cherty limestone, containing Zaph- 
rentis, crinoidal remains, Polyzoans, Hemipr onites, Spirifer, &e. The 
latter beds rise descending the cation, presenting marked inequalities or 
undulations, and finally make up the bulk of the cation walls, and show- 
SA ag 
