KAX(JKS OF KASTKRN CKNTIIAL NKVADA 220 



to (lefornijition or, more often, directly to erosion ;ictin<; U))on tlie folded 

 and faulted rocks. In this place it is i)lainly due to the latter process. 

 There are a series of faults which strike in general northwest and soutli- 

 east, transverse to tlie trend of the mountains at this ])oint. These faults 

 are not directl}^ expressed in the topograph}^ for sometimes the down- 

 thrown side ap]H'ars as a scar]) and sometimes the upthrown, depending 

 upon the relative resistance of the beds, while more fre(|uently there is 

 no effect u])on the to})ograph3'', excei)t, perhaps, the formation of a 

 gulch.* Therefore the Diamond range is, so far as known, one of erosion. 



E(/(ui range. — The Egan range consists of a number of adjacent folds 

 which have been well dissected b^' erosion. In the extreme northern 

 end the prevailing structure is anticlinal, and farther south it changes 

 to synclinal. At the southern end there is an alternating series of oi>en 

 folds which are not expressed in the topography. Here the writer sus- 

 pected a number of east-and-west faults along lines marked b}^ deep 

 transverse gaps, but not by scarps. 



In general, therefore, this range seems to be one of erosion. 



Pancake range. — The faulted syncline of Newark mountain and the 

 Alhambra hills, which is found in the Eureka district of the Diamond 

 range, is continued southeast across the intervening valley to the Pan- 

 cake range. 



At the south end of the Pancake range, at Twin springs, a number of 

 north-and-south faults were observed in the Pliocene sediments. Some 

 of these faults have a vertical separation of several hundred feet and are 

 marked by gullies, but not by scarps. 



The Pancake range, therefore, is largely one of erosion. To this must 

 be added vulcanism, for a large part of it is built up of lava. 



Hot Creek range. — At Hot creek the range is essentially a faulted anti- 

 cline, supported on the west by a heavy buttress of rhyolite, which far- 

 ther north envelopes and hides the Paleozoic core. Observed faults run 

 north and south, while others, strongly suspected, are east and west. 

 Some of the north-south faults are marked by gulches and some by 

 normal scarps (see plate 25, figure 5). 



The anticlinal ridge with no core of relatively great resistance, and 

 the normal fault-scarps suggest strongly the theory of origin by direct 

 deformation. The question, at first puzzling, as to why erosion has been 

 so comparatively impotent here finds a plausible answer when we con- 

 sider that the lavas must have originally covered this portion of the 

 range as they do now a few miles farther north. This covering must 

 have j)rotected the Paleozoic strata from erosion ; but in the lava buttress 



* See Atlas, Monograph xx, U. S. Geol. Survey. 



