BT.joHx.] Ti^TON RANGE. 421 



ing the final transverse section of the range, section G, the facts observed, 

 as in the preceding diagrams, are readily distinguishable from the in- 

 ferred. 



The western flank of this portion of the range is apparently precisely 

 similar to what obtains in the blocks between Fox Creek and the West 

 Teton Valley — a great foreland covered by the sandstone and red arena- 

 ceous deposits, which here constitute the uppermost member of the Carbon- 

 iferous. But while this block terminates in precipitous declivities facing 

 the east, it is here succeeded by loftier and ahnost equally massive ridges, 

 which appear to rise up from beneath the foreland bloclc in a succession 

 of great billows with whi(;h this portion of the range is furrowed. It is 

 also rendered apparent that these ridges are stratigraphically alike; that 

 is, they are all composed of the same series of strata, which were once 

 spread out in horizontal layers on the bottom of the sea, and to account 

 for their present position, fortunately, we are not wholly without evi- 

 dence that furnishes a clue. As seen from the Lower Gros Ventre Buttes 

 in Jackson's Valley, the east wall of the range rises rapidly over 1,000 

 to 2,000 feet of Archaean ledges, which are cai)ped by more than as great 

 again thickness of sedimentary fonnations. The latter, at one point, a 

 little south of west of the confluence of the Gros Ventre with the Snake 

 Eiver, are projected in a sharp-crested, bastion-like ridge a distance be- 

 yond the lofty axial summit, and where they plainly exhibit one of the 

 sharp subordinate undulations into which the great primary fold of the 

 range was corrugated. The western flank of a similar, if not identical, 

 secondary fold is preserved in the outlying hiU in the north angle of the 

 debouchure of East Pass Creek, a few miles south of the above-mentioned 

 exposure, in which the Carboniferous limestones are seen dipping gently 

 into the range, or W. 35° N. at an angle of 14°. The same beds again 

 appear in the Lower Gros Ventre Buttes, where they were observed by 

 Professor Bradley, in nearly horizontal position. 



Ascending East Pass Creek, which flows through a wild, thickly- 

 wooded ravine, no ledges in situ are met with adjacent to the trail until 

 approaching the summit of the pass, where we encounter the upper sili- 

 cious horizons of the Carboniferous. About midway, large masses of 

 buff, rough-weathered, magnesian limestone, more or less abraded, ap- 

 pear in the steep slopes, indicating the presence of the Niagara beds in 

 the dei)ression between the outlying hill and the main mountain. And 

 higher up, j)erhaps a couple of miles from the summit, quantities of 

 abraded boulders of gneiss, schists, and other Archaean rocks are met 

 with, which doubtless were brought down by the streams which i^ene- 

 trate the range to the north. 



On descending West Pass Creek, a mile or so west of the siunmit and 

 but Little lower in elevation, the trail crosses a spur ridge in which is ex- 

 posed a considerable thickness of deep red, even-bedded sandstone and 

 sandy shales, dijDping at an angle of about 45° southward, and which 

 probably represent the "red beds" of the Trias. These deposits con- 

 tinue for a distance of several miles ; even where the ledges are imex- 

 posed their position is marked by the luxuriance of herbaceous growth 

 so characteristic of the slopes underlaid by or comjjosed of the debris 

 derived from these deposits, as observed at many other and distant local- 

 ities in this region. Between three and four miles below the summit the 

 main valley receives on the right a deep gulch which heads between 

 Station XLIII and its higher neighbor to the northwest. In the lower 

 angle of this gulch the steep mountain side is plated with heavy ledges 

 of Carboniferous limestone dipping steeply to the southwest, but gra(lu- 

 ally slackening in inclination as they rise higher in the mountain. The 



