256 DBSCEIPTIVE GEOLOGY. 



glomerate, and containing a varying admixture of broken feldspar crystals. 

 Interstratified with, these quartzites are several beds of greenish clays, from 

 50 to 100 feet in thickness, sometimes hardened into argillaceous slates, and 

 containing a little mica. The lower beds consist, in general, of more com- 

 pact, fine-grained quartzites, of a lighter color, passing into a white opaque 

 quartz-rock, which has only been observed in this part of the range. 



On the eastern side of the canon, the immense mass of Tokewanna 

 Peak, which reaches an altitude of 13,458 feet, is formed of beds of the 

 purple and red quartzites, dipping 16° north. The steeper dips of 52°, 

 found on the Bear River Ridge, were not observed here, though the Upper 

 Coal-Measure strata reach 45°; and may probably be caused there by a 

 local change of strike, or a curving in of the beds toward the axis of the 

 range. The geological axis on this side of the canon runs through the 

 saddle in the ridge, beyond the second peak south of Tokewanna, while the 

 main summits beyond this point are formed of similar beds, dipping 5° to 

 6° southward. The thickness of the upturned beds of the Weber Quartzite 

 belonging to the northern member of the fold cannot be less than 10,000 feet 

 at this point. The sudden character of the change of dip at the axis would 

 seem to indicate a dislocation, and probable displacement along its line, but 

 whether the downthrow be to the northward or southward can hardly be 

 determined by the lithological character of the beds, which show only such 

 very general distinctions at different horizons, that it is impossible to trace 

 a correspondence of strata on these grounds without an. exceedingly minute 

 and detailed examination. 



The main crest of the range is made up of beds of quartzite dipping 

 5° to 7° southward, which have been carved out by the action of n^vd-ice 

 into huge, shallow, semicircular basins, scantily covered by timber, and 

 containing numberless little shallow lakes and ponds, which are inclosed by 

 almost perpendicular walls and ridges, sometimes rising into peaks two and 

 three thousand feet above their general level. 



On the spurs between the east and west branches of Black's Fork, north 

 of Tokewanna Peak, the beds of the Upper Coal-Measure group can be 

 traced by the narrow ridges of limestone, projecting like walls above the 

 general surface, here and there, and by the transverse depressions and 



