KANGKS OK NORTHEASTKRN NKVADA 223 



Pinon nuu/e. — The Pinon range, which lies next went tVoiu the Hum- 

 boldt rant^je;'^ consists in the central })ortion of a magnificent anticlinal 

 fold, with a curved, although in general north-and-south, axis. The 

 southern termination of the fold is removed by a transverse northeast- 

 and-southwest fault which has faulted down the rocks to the south. 

 Mr King believes that this is the same fault as that which has cut off 

 the end of the Diamond range (which lies southeast of the Pinon range), 

 and has terminated it on the north. North of the Humboldt river, ac- 

 cording to Mr King, the same anticlinal fold continues, but is soon cleft 

 by a north-and-south fault, by which the entire eastern portion of the 

 mountains for 40 miles has been dropped out of sight. 



Mr Walcottf has made a section across the southern end of the Pinon 

 range, at Ravens nest. The section shows an anticlinal fold cut by two 

 north-and-south faults. One of these faults, in the center of the range, 

 has been estimated by the present writer, from the section given, to have 

 a vertical separation of nearly 4,000 feet, while the other has a vertical 

 separation of about 6,000 feet. Neither of these faults has any influence 

 on the topography except that the first named one has determined a 

 longitudinal shallow valley of erosion. 



Considering the displacement which is believed by Mr King to deter- 

 mine the southern end of the range, it is not clear to the writer why the 

 self-same fault is thought here to upthrow the mountains on the north 

 side, while at tlie northern end of the Diamond range, close by, it is 

 supposed to upthrow an equally high and important range on the south 

 side. In case this is really a single fault, we must explain the opposing 

 phenomena by erosion. 



We can only expla,in a section like that given by Mr Walcott by ad- 

 mitting that the topography is entirely due to erosion; it is not the 

 direct expression of the dislocation. The anticlinal structure in the 

 neighborhood of Pinto peak may be explained like that of the Hum- 

 boldt range, for here the highly resistant Cambrian quartzites form the 

 center of the anticline and the summit of the range. 



Resume of structure in northeastern Nevada. — The different mountain 

 ranges just described seem in each case to be due essentially to erosion. 

 The crests of the ranges are sometimes eroded sj^nclines, and where 

 the whole of a lofty mountain-mass has a governing anticlinal structure 

 this is generally to be explained by the difference in resistance of the 

 rocks. The faults which have actually been determined are shown 

 in nearly every case to have no primary effect upon the topography, 

 although they sometimes determine gullies or valleys by reason of their 



* Ibid. 



t Monograph xx, U. S. Geol. Survey, p. 201. 



