ST. JOHN.] HOBACK CANON SECTION. | 185 
ing a thickness ofa thousand feet, perhaps more. Approaching the 
debouchure of the cation, where these strata exhibit their greatest verti- 
cal exposure, the limestones are crumpled into two low anticlinals, the 
axis of the lower fold, or that forming the west flank of the Hoback 
Cafion mountain belt, exposing a nucleus of brownish-gray magnesian 
limestone, which lithologically resembles the so-called Niagara horizon. 
A short distance within the mouth of the cafion a small cave has been 
fashioned out of this bed in the wall rising over the north side of the 
stream ; and just below this issues the sulphnr spring previously men- 
tioned. The west flank of the cation ridge is here much eroded, the 
ledges in the steep slope farther south showing their basset edges, dip- 
ping westward. Higher up the cafion the limestone beds exhibit inter- 
esting examples of irregular deposition, in places a heavy bed wedging 
out, so that subjacent and overlying beds elsewhere separated by many 
feet thickness of intervening layers are brought into immediate con- 
tact. 
The above-described limestones, which compose the walls throughout 
the lower reaches of the cation, are unquestionably Carboniferous, as 
shown by the fossils they contain, while the heavy series of conformably 
superimposed siliceous and limestone deposits agree in relative position 
with identical deposits occurring in the Snake River Mountains and 
elsewhere, which have been referred to the later epochs of the same age. 
No fossiis, however, were here observed in these beds, and the demarka- 
tion between them and the typical ‘‘red beds” of the Trias is obscure 
in the cafion section. But from the adjacent heights the Triassic “ red 
beds” are seen to be well developed, occupying the synclinal in the cen- 
tral portion of the mountain belt. 
The eastern border of the Carboniferous belt in the above described 
caiion section presents an interesting flexure, which, in connection with 
that observed in the early Mesozoic strata just above, exhibits anomalous 
results in the action of the dynamical forees in this part of the Hoback 
Cation ridge which may beof local significance. Intheelevation and fold- 
ing of the strata over this mountain belt the Carboniferous beds were 
forced up into the position they now oceupy, the strata in the eastern fold 
remaining intact, although there is evidence that along the eastern flank 
of the west fold the beds were subjected to excessive tension, which might 
have resulted in the severance of the superimposed and perhaps less 
tenacious Mesozoic strata, the latter appearing in the corresponding 
parallel fold directly opposite the upper siliceous horizons of the Carbon- 
iferous, the before-mentioned gulch descending from Station IL, marking 
the line of disruption. The facts, such as were observed, are reproduced 
in the diagram of the cafion section. 
Six miles north of Hoback Cafion the mountain ridge is crossed by a 
small tributary of the Snake, which rises in the southern slope of the 
Gros Ventre Mountains, inthe vicinity of Station XII, whose picturesque 
valley exhibits essentially the same structural features above noted. 
The narrow debouchure of the caiion is marked on either side by walls 
composed of massive gray limestone and pale reddish siliceous beds of 
the Carboniferous, dipping at a moderate angle northeastward. Ascend- 
ing the caiion, the same ledges outcrop in mural exposures, the incli- 
nation changing a mile or so ahove the entrance to a westerly one at an 
angle of 10° to 15°, and gradually steepening higherup the valley, which 
opens outinto pretty little meadow intervales; thenarrow portions of the 
valley walled by limestone cliffs and steep taluses of débris; the mountain 
slopes furrowed by exceedingly steep ravines and clothed with beauti- 
ful evergreen forests. The bed of the stream is filled with a variety of 
