226 J. E. SPUKR — ORIGIN AND STRUCTURE OF THE BASIN RANGES 



to the mountain ridges and with faults. From what we can learn of the 

 structure, where the stratified rocks are exposed, it is a})})arent that ero- 

 sion has operated very powerfully. We find synclinal ridges and anti- 

 clinal ridges, with a hard resistant rock at the core, and faults along 

 which deep valleys have been excavated. On the other hand, we ap- 

 pear to have no sufficient evidence of an}'^ feature of relief being due 

 directly to deformation. Some sup})osed faults have been described in 

 terms implying this direct relation, but it is not clear from the descrip- 

 tions that these faults actually exist. Indeed, as in so many other cases, 

 the existence of the fault seems often to have been assumed from the pres- 

 ence of a scarp. We must conclude, therefore, that the ranges of north- 

 western Nevada, in so far as we have direct evidence on the questions of 

 their structure and origin, are due chiefly to erosion. 



RANGES OF EASTERN CENTRAL NEVADA 



Antelope range. — The Antelope mountains, which lie between the north- 

 ern extension of the Snake range and a portion of the Schell Creek range, 

 are for the most part volcanic. In the southeastern ])ortion, however, 

 are Silurian and Devonian rocks. The attitude of the rocks here, as 

 compared with that of the same rocks on the other side of Antelope val- 

 ley, goes to show that this valley is anticlinal. It is therefore prob- 

 ably one of erosion, and the same inference ai)plies to the Paleozoic 

 foundation of the Anteloi)e range. 



Schell Creek (tad Hi(//d(ui(l nmges. — The Schell creek range contains a 

 number of adjacent anticlines and synclines, which often trend somewhat 

 obliquely with the range. East of Ely there is a longitudinal valley 

 eroded along the axis of an anticlinal fold ; farther south this anticlinal 

 fold seems to cross from the Schell Creek to the Egan range. There are 

 probably some transverse faults. 



The Highland range has a system of petty folds, some longitudinal 

 and some transverse. There are also a num])er of transverse faults, some 

 of which have vertical displacements of several thousand feet. In the 

 mining camp of Pioche there is exi)08ed by mining a system of faults, 

 which is prol)ably a good index to the less observed faults of the range. 

 Tlie faults here are numerous and belong to a north-and-south and an 

 east-and-west system. The main one runs east and west, and along it 

 the relatively downthrown side forms the highest hills, being indeed 

 marked by a continuous cliff, which but for the fact above stated might 

 be considered a ty})ical fault-scarp. The massive metamorphosed lime- 

 stone has resisted erosion better than the brittle, easily frost-fractured 

 quartzite on the upthrown side. Other faults are marked by gullies. 



