464 EEPOET UNITED STATES GEOLOGICAL SURVEY. 



cific Creek. Its bed liere is occupied by a narrow flat in which the 

 stream is ponded by beaver-dams. 



Station XLVIII gives a good view of the surrounding country, from 

 which much important information may be gained relative to the gen- 

 eral character and distribution of the geological formations occurring 

 therein. Looking westward, the southern declivity of the mountain- 

 ous divide north of Buffalo Fork and Pacific Creek is traced to the angle 

 where the hills trend round to form the eastern boundary of Jackson's 

 Basin opposite and north of the lake. At the point where the slopes 

 pass round out of sight a pair of small lakes lie within the higher and 

 older terrace area at the foot of the mountain, which Professor Bradley 

 describes as bayous of the ancient abandoned channel of the Snake. 

 Beyond lie the glistening waters of Jackson's Lake, and the majestic 

 wall of the Teton Bange seems close at hand, though really more than 

 15 miles away. This southern slope of the divide, probably in the vicin- 

 ity of the twin lakes, shows a low outlying hill made up of a brown 

 earthy (?) deposit which is weathered very like deposits of similar appear- 

 ance occurring in Mount Leidy and the high hills to the east. Between 

 the latter locality and the high river bluff near the upper end of the 

 lower valley of Buffalo Fork described above, in the recess formed by 

 the entrance of the valley of Pacific Creek, the hills are low and show 

 exposures of buff-yellow sandstones like those in- the river bluff above. 

 These sandstones are often gray and generally coarse-grained, recalling 

 Laramie Group deposits in the Snake Biver and Caribou Eanges, 

 although they are doubtless more recent. The exposures of " gray and 

 buff, fine-grained, shaly sandstones" described by Professor Bradley, as 

 mentioned in a preceding page, that outcrops near the mouth of Buf- 

 falo Fork, probably belong to the same series. Professor Bradley also 

 mentions in the adjacent slopes the occurrence of "partially-cemented 

 Post-Tertiary sands and gravels, with occasional exposures of white 

 marly clays, supposed to be of the same age, though no fossils were 

 seen." The latter deposits are clearly, in part at least, identical with 

 before-mentioned strata occurring in the vicinity of the Upper and 

 Lower Gros Ventre Buttes, but the gravel beds would hardly be referred 

 to the deposits which make up the bulk of the hills north and south of 

 the lower course of Buffalo Fork, though they may belong to the singu- 

 lar conglomerate whose appearance has already been mentioned in the 

 summit of Station XLVIII. The disturbed condition of the sandstones 

 at the mouth of Buffalo Fork contrasts with the uniformly moderate and 

 apparently regular inclination of the soft sandstones occurring in the 

 adjacent hills either side of the Buffalo Fork, with which, however, they 

 offer close agreement lithologically. 



To the northwestward of Station XLVIII, the slopes in the opposite 

 side of Pacific Creek rise into a high, short mountain ridge, perhaps three 

 or four miles distant, forming a prominent landmark, which we had had 

 in view since entering Jackson's Basin. Its southern face presents es- 

 carped walls sustained by bulky buttresses in which the bared strata are 

 intricately sculptured by the elements. These apparently consist of a 

 heavy conglomeritic deposit, in appearance laminated or thin-bedded, 

 rusty yellow-buff and drab, with indurated arenaceous bands, reaching 

 a thickness of 500 feet or more, which rest upon a heavy bed of light- 

 buff arenaceous rock, probably soft sandstone, showing an exposed thick- 

 ness of 50 to 100 feet above the steep talus. The inclination is gently 

 northeastward. The outlying foot-hills on the south are much cut up by 

 the wash, and are well wooded, showing only now and then exposures 

 of buff arenaceous deposits, until approaching the bluffs on the north 



