ST. JOHN.] GROS VENTRE RANGE. 455 



valley of the Little Gros Ventre, and -which are so •well displayed from 

 Station XLIY. The northeast face of tlie peak brealcs down in sheer 

 preci])ices of dark- weathered limestone into an amphitheatre, which is 

 divided into two nearly eqnal parts by a hnjie bnttress that projects 

 from the main peak, carrying- on its crest cnri<msly weathered pinnacles 

 and towers of limestone, terminating in a conical point. The amphithe- 

 atre is idled with banks of snow, which feed the tiny lakelets that nestle 

 at the foot of the debris slopes. To tlie east the peak is rent and fis- 

 sured by the action of the elements, placing an almost impassable bar- 

 rier between the station and the lower crest in which the monntain 

 ridge is terminated above the saddle separating the drainage of the two 

 Gros Ventres. 



The summit of the peak is strewn wdth angular limestone fragments, 

 wiiich, in places, are tumbled into funnel-shaped sinks; no erratic 

 materials were observed. It is made np of drab limestone interbedded 

 with dark brownish-drab magnesian layers and yellowish weathering 

 deposits in the lower i^ortion, and abonnding in fossils, Hcmipromtes 

 crcnistrla Ijeing particnlarly numerous in certain layers, besides a large 

 Splri/h; AthyriSj Zaphrentls, &g. These beds dip at an angle of loO, 

 AV. 30O N. to :N^. 50 W. In the northwest foot of the peak they inchne 

 at about the same angle, K. 40° E. to N. 5° W., and at one place bulged 

 up into a slight anticlinal or undulation, with a -westerly dip of about 

 10^ on the one flank. 



In the sloping ridge which forms the western wall of the gulch that 

 Hows down to the Gros Ventre to the northward, the Carboniferous 

 limestones are overlaid by a series of arenaceous deposits, consisting of 

 ■intensely hard, pinkish siliceous beds and hard, laminated, grayish, 

 reddish-stained sandstone, including bauds of red and yellowdsh sandy 

 shales, which impart to the exposures so strong a Triassic aspect. But 

 these deposits are precisely like the upper beds of the Carboniferous in 

 the Teton and Snake Eiver ranges to the w^est, in Avhich latter region 

 they are known to be succeeded by later- formed limestones, whose or- 

 ganic remains establish their Carboniferous age. These Carboniferous 

 red beds are doubtless identical with the lower red-bed series in the 

 debouchm-e of the Gros Ventre, which -were described, as above quoted, 

 by Professor Bradley, where they were estimated at 400 to 500 feet 

 in thickness. The same beds also appear in the east side of the above- 

 mentioned gulch, capping the limestones, which slope oft" at a moderate 

 angle northward in the declivity which forms the Gros Ventre or north-^ 

 ern face of this jjart of the range ; and still farther east a heavy mass of 

 deeper red-colored strata appears, borne upon the flank of the moun- 

 tain, their edges shown in escari^ments facing southward. The latter 

 deposits are doubtless the same as those noticed by Dr. Hayden in the 

 valley of the Gros Ventre, where they are associated with thin bands 

 of gypsum. 



To tlie southeast this northern barrier ridge shows a sharp fold, the 

 limestones flagging the south-facing slope, and vrhich ])robably is part 

 of the great fold seen from Station XLIV. It is possible that the belts 

 of red deposits seen at various points Avithin the range belong to the 

 Tria.ssic "red-bed" series, which were curved over the great fold, but 

 Avhich have become quite disconnected from the northern mass through 

 the agency of subsequent erosion, which has removed a vast amount 

 of sedimentary materials over the central portion of the range. The 

 northerly inclination of the Carboniferous dejiosits cairies them beneath 

 the level of the Gros Ventre, along the north side of which appears a 

 line of beautifully-eroded bluffs, sliowing a thickness of several hun- 



