316 DESCRIPTIVE GEOLOGY. 



west, descending gradually toward Kamas Prairie, while the outcrops of 

 the upturned higher members of the fold close together, its geological 

 axis nearly corresponding with the topographical, or following the line of 

 the main crest to the west of Bald Mountain. The beds of the Weber 

 Quartzite are exposed to the very edges of Kamas Prairie, where they dis- 

 appear beneath the gravels and soil of the valley. In the ridge to the south 

 of Kamas Creek, they already curve around with a northwest strike, dip- 

 ping 20° to the southwest ; and south of the mouth of the upper Weber 

 Canon, the overlying beds of the Upper Coal-Measure are found striking 

 north 55° east, with a dip of 25° to the northwest. The interval between 

 the western end of the Uintas and the mass of the Wahsatch is occupied by 

 the Quaternary Valley of Kamas Prairie, and the trachyte hills between that 

 aiid Provo Valley, so that the exact relation of the beds of these two sys- 

 tems of upheaval cannot be definitely arrived at; but in the tendency of the 

 flanking beds of the Uinta to close together at the western end, and in the 

 finding of little outcrops of Carboniferous limestone and Triassic sandstone 

 in ravines of the trachyte hills, we have sufficient proof that the Uinta up- 

 heaval is quite disconnected from that of the Wahsatch, and that the upper 

 beds, at least as high as the Jurassic, probably once filled this interval. The 

 existence of this trachyte body and other little bodies to the northward 

 indicates a line of. weakness and fracture nearly parallel with the main ridge 

 of the Wahsatch, and crossing it diagonally ftirther north. 



Trachyte Body. — The highest point at which the trachyte beds are 

 found is at Heber Mountain, at the head of Heber Canon, where they form 

 the three highest peaks between the headwaters of the Provo and the Uinta. 

 Here they have apparently overflowed the conglomerate beds of the Uinta 

 Eocene ; still, this fact is not definitely proved, since these Tertiaries are 

 only found to the south of the trachyte body, and nowhere directly under 

 it. On the ridge to the east of Heber Mountain is a considerable accumu- 

 lation of gravel and boulders, containing rounded fragments of both quartz- 

 ite and trachyte, which is probably the remains of a glacial moraine, or 

 may possibly result from the decomposition of beds of Wyoming Conglom- 

 erate, which covers the neighboring ridges at about this elevation. In the 

 latter case, it would be an indication that the trachyte was at least of earlier 



