SHOSHONE RANGE. 619 



are in some places a mere thin glaze, and in others a heavy coating nearly 

 a quarter of an inch thick. 



Along the west and north margins of this field of basalt, there outcrops 

 a line of quartzites and quartzitic shales, which form for 15 miles the foot- 

 hills and base of the mountains. Their prevailing strike is a little west of 

 true north, with a dip of about 35° to the east. They are mainly finely- 

 laminated schists, which here and there in the lower horizons and at the 

 base of the quartzitic series, apparently pass into blue quartzitic bands, with 

 a little impure limestone. This quartzitic mass has great thickness, and, 

 from the fact that, as developed to the southward, it is both underlaid and 

 overlaid by limestone, has been referred to the Weber period. Further cor- 

 roboration of this is the occurrence of a bed of impure anthracite in the 

 lower siliceous zone, not far from Argenta, supposed to represent a horizon 

 near the junction of the Weber Quartzite with the Lower Coal-Measure 

 limestone. 



The north and south belt of upturned quartzites, lying along the west 

 side of the Whirlwind basalts, is about 2 miles wide. Continuing its 

 strike to the south, the quartzites are seen to wrap around the east side of a 

 mass of granite, which rises above the quartzite in a high plateau, crowned 

 by several prominent hills. West of this granite, the quartzites for several 

 miles are much broken, but appear to have a general dip to the west for 

 about 4 miles west of the granite, when they curve into an east dip again, 

 making a low, obscure synclinal. That part of the range covered by the 

 Whirlwind basalts is lower and less prominent than the mass immedi- 

 ately to the southwest, from which it is nearly separated by a deep bay of 

 Quaternary accumulations. 



^ South of this narrow neck, the range has its broadest expansion, reach- 

 ing about 16 miles in a direction transverse to its trend. For about 20 

 miles in the direction of the trend, the range is occupied by tlje quartzites 

 already mentioned. They are covered along the east foot-hills by an 

 overlying belt of rhyolite from 2 to 5 miles in width; and, west of Carico 

 Lake, the entire range is overwhelmed by rh3^olite. The granite mass, 

 already mentioned, offers a good example of conoidal structure, on so large 

 a scale that the rude layers might almost be mistaken for a sedimentary 



