456 DESCEIPTIVE GEOLOGY. 



dip, assume gradually an eastern dip as one penetrates tlie bills. These 

 beds belong without doubt to the Wahsatch limestones, and the upright 

 quartzite beds must therefore represent the base qi the Weber Quartzites, 

 turned up steeply against the flanks of the Aqui Mountains. 



Aqui Mountains. — Beyond Tooelle and Rush Valleys, to the west- 

 ward, rises a second high mountain-ridge, having a north and south trend, 

 parallel to the Oquirrh Mountains, known by the Indian name of Aqui or 

 Onaqui. Its central portion, of which the culminating point, Bonneville 

 Peak, rises nearly 7,000 feet above the level of Salt Lake, is a broad 

 mountain mass, some 10 miles in width, cut by deep canon-gorges, and 

 Covered with a considerable growth of timber. To the north, it extends 

 in a sharp narrow ridge, of gradually-decreasing elevation, to the shores of 

 Salt Lake, the continuation of its line of elevation being seen in Stansbury 

 and Carrington Islands. To the south of the central mass, it is a rather 

 flat-topped ridge, having an elevation of only about 4,500 feet above the 

 adjoining valleys, which extends beyond the limits of the map, connecting 

 with the group of hills that enclose Rush Valley on the south. 



The geological structure of this range, as well as could be determined 

 by the limited observations made, is that of an anticlinal, whose axis, as far 

 as a few miles south of Bonneville Peak, has a due north and south trend, in 

 a line with the main crest of the ridge, bending, south of this point, slightly 

 to the eastward. Along this axis, in the central portion of the range, a line 

 of fault has been developed, resulting in an upthrow of the western member 

 of the fold, which reaches its maximum of not less than 10,000 feet at 

 Bonneville Peak, and gradually decreases to the north and south as the 

 axis of the anticlinal descends. 



The southern portion of the range, as seen on the map, is formed of 

 limestones, having a gentle western dip, and striking diagonally across the 

 range a little to the west of north. The higher beds of these limestones 

 contain many arenaceous and sometimes quartzite beds, and would appear 

 to correspond to the alternating beds of the upper part of the Wahsatch 

 limestone. Beyond the limits of the map, to the southward, are seen bodies 

 of quartzite, apparently overlying these, which probably represent the 

 Weber Quartzite. Toward Reynold's Pass, the limestones become more 



