414 REPORT UNITED STATES GEOLOGICAL SURVEY. 



alluded to are incorporated in the diagram of the section across the north 

 end of the range given in an accompanying plate. 



Station XXXII attains an altitude of 9,749 feet above the sea. The 

 view from the summit, looking north and west, takes in the great volcanic 

 watershed and the plain north of Pierre's Basin, the nearer slopes clothed 

 in dense forests of pine and the higher mountain flats dotted with beau- 

 tiful clumps of dwarfed spruces. To the east the view is shut out by 

 higher ridges, in which appear long lines of strata probably referable 

 to the Silurian, but here and there through the depressions appears the 

 crest of the peculiarly weathered Archaean ridge, which is seen to pass 

 northward much diminished in height and finally disappears. It was 

 not certainly ascertained whether this latter ridge was denuded of its 

 superincumbent sedimentary mantle prior to the flow of volcanic mate- 

 rial or not, but such appears to be the case. But to the west the sedi- 

 mentaries again intervene, as also to the east, in which latter quarter 

 Professor Bradley found several hundred feet of limestone, representing 

 the Lower Silurian to the Carboniferous, reclining on the Archaean nucleus 

 of the range, and in turn overlaid by the volcanics. Hence there can be 

 no question that at one time the sedimentaries folded around the north- 

 ern extremity of the range, but subsequent denudation effected their 

 removal down to a level which came within the reach of the great vol- 

 canic inundation, which at a comparatively modern date submerged so 

 large an extent of the mountain border. Almost due north of Station 

 XXXII, overlooking a small area of Carboniferous plateau in the fore- 

 ground, beyond a deep gorge whose waters flow out into the Upper 

 Snake Valley, the last elevation in this direction exhibits what appears 

 to be a rather sudden upheaval of the strata, which in places apparently 

 stand almost vertical, but with a general westerly inclination. Within 

 less than a mile to the eastward the Archaean ridge passes behind a 

 nearer ridge, and it seems highly probable that the flexure above men- 

 tioned is in some way intimately connected with the presence of this 

 continuation of the metamorphic axis of the main range. It became a 

 subject of frequent observation, as our work extended into the middle 

 and southern portions of the range, that the sedimentaries often reached 

 to within a mile and less of those points where the crystalline nucleus of 

 the range had reached the maximum of upheaval, and this without 

 greatly disturbing the sedimentaries; while at other localities, where 

 there was not apparent cause, indeed where the Archaean rocks do not 

 even show themselves, evidences of some of the most remarkable dis- 

 turbances were encountered, showing the unequal action of the elevatory 

 forces, especially at the extremities of the great uplift in which origi- 

 nated the range. That the above fold belongs to one of the latter 

 exhibitions there can be little doubt ; and hence the unprofitableness 

 of the endeavor, with the limited time at our disposal, to trace the fold 

 southward to any distance, where the elevatory forces seem to have been 

 far more uniformly distributed, as evidenced at numerous points where 

 we succeeded in extending our sections across the range, and where the 

 minor inequalities in the sedimentaries are altogether subordinate to 

 the great displacement. 



The outline sketch from Station XXXII exhibits the relations of the 

 sedimentaries to the metamorphics in this northern portion of the range, 

 where the former constitute the highest elevation, 10,300 to 10,500 feet. 

 A little west of south rises the rugged spur which defines the northern 

 border of the wide Archaean area, on the western flank of which rise up 

 the volcanics, as shown in section B of the accompanying plate of sec- 

 tions across the Teton Bange. Almost in line with the western promon- 



