322 G. D. LOUDERBACK — STRUCTURE OP THE HUMBOLDT REGION 



Peak Triassic," the formation so easily, according to the account quoted, 

 removed by erosion. 



That great erosion has occurred in the bedrock series there is ample 

 proof, but it was evidently chiefly during the interval between the post- 

 Jurassic folding and the laying down of the volcanic series over a coun- 

 try of low relief. The post-basaltic erosion of the intermontane valleys 

 is practically nil, and the erosion within the mountains, judged from its 

 effects on the volcanic series, has not proceeded very far. 



Recent faulting. — Faulting of the Recent period has been frequently 

 reported in the Basin region, and Russell presents a map* showing the 

 lines along which he has determined Recent fault scarps. The best 

 example of such faulting found during the present investigations is 

 along the west base of the Star Peak mountain block. A very distinct 

 scarp was traced for 6 or 8 miles, and, according to Russell, it continues 

 along the whole length of the range. It varies in height from 4 or 5 up 

 to 30 or 40 feet, depending apparently on topographic slope, character 

 of rock, etcetera. This fault scarp presents a striking contrast with the 

 Lahontan shore cliffs which are so common in that part of the Great 

 basin, for while the horizontal base line of the shore cliffs winds about 

 projections or into recesses, the fault scarp climbs up over the alluvial 

 slopes and drops down into the intervening hollows. No deposits are 

 too late for it to traverse, and even the alluvial cone coming from Rocky 

 canyon, which is one of the larger drainage lines, shows the fault scarp, 

 here several feet in height, running across its apex. Plate 18, figure 2, 

 is a view of the Star Peak range looking southeast from the alluvial cone 

 of Rocky canyon. The fault scarp can be traced quite distinctly along 

 the base of the range for almost a mile. 



Such recent faults may be considered evidence that the old fault planes 

 are still planes of weakness, and that the great crust blocks have not 

 yet perhaps reached their final condition of equilibrium. Such planes 

 are evidently possible loci for future movements. 



TABLE MOUNTAIN AND THE EAST RANGE 



Location and extent. — The Table Mountain or East range (the Pah Ute 

 range of the Fortieth Parallel Survey) is the first range east of the Hum- 

 boldt mountains. It is a rather long and high range, and for the present 

 purpose was studied only in the vicinity of Table mountain, a flat- topped, 

 basalt covered portion about 30 miles east of Lovelock. 



The bedrock complex.— The character of the bedrock complex is so sim- 

 ilar to that in the Humboldt mountains that, for the present purpose, it 

 needs but slight notice. Nothing distinctly Jurassic was observed. The 



*U. S. Geol. Survey, Monograph xi, plate xliv. 



