210 GEOLOGY OF THE EUKEKA DISTRICT. 



ing a displacement of 13,000 feet, that have determined the orographic 

 blocks. A study of the structural details as presented in this work shows 

 that the folding and flexing of the beds are largely due to lateral com- 

 pression. The grandest effects of this lateral compression are seen along 

 the central portions of the mountains between the Spring Valley and 

 Rescue faults. It is here that the greatest energy has been displayed. 

 Within these lines lie the abrupt anticlinal fold of Prospect Ridge, the 

 sharp synclinal fold of Spring Hill between the Hoosac and the Pinto, and 

 the broad syncline in the Nevada limestone between the Pinto and the 

 Rescue faults. Westward of Spring Valley the structure stands out in 

 marked contrast with the mountain blocks included between these great 

 faults. Receding from the fault, the plication of strata becomes more and 

 more gentle to the west without any violent orographic disturbance, the 

 limestones falling away in broad sweeping rolls with relatively low angles 

 of dip. East of the Rescue fault a powerful compression of strata is shown 

 by anticlinal and synclinal folds in the region of Diamond Peak. 



Faulted anticlines. The structure whicli, in the opinion of the writer, is 

 most common in the Great Basin ranges, that of a faulted anticline with a 

 downthrow along the axial plane, is not brought out in the sheet of geolog- 

 ical sections, but is nevertheless well represented in the district, both in the 

 Fish Creek Mountains and at Newark Mountain. In both these uplifts 

 the displacement is accompanied by an escarpment along the fault which is 

 coincident with the axial plane. In the Fish Creek Mountains we have a 

 broad, gently inclined, westerly dipping limestone body, with the axis of 

 the anticlinal near the eastern edge of the uplift, the downthrow measuring 

 about 600 feet. On Newark Mountain, which is a sharp single ridge, the 

 downthrow also occurs along the eastern crest of the uplift, the escarpment 

 measuring, approximately, 1,000 feet. In both instances the easterly dip- 

 ping beds extend down the mountain slope until lost beneath valley accu- 

 mulations. On the west side of Newark Mountain the flexible White Pine 

 shale affords an excellent example of plication without fracture. Details in 

 regard to the structural features of both the Fish Creek Mountains and 

 Newark Mountain will be found in the chapter devoted to the descriptive 

 geology of those areas. 



