Vol. 6] Eeid: The Geomorphogeny of the Sierra Nevada. 



115 



At first glance this form of topography is strongly suggestive, 

 if not a proof, of faulting. But the various stream courses hint 

 at much possibly subsequent drainage. Such condition of the 

 streams would account for some of the topographic features, and 

 would render obscure many more. In the Carson area three of 

 the large creeks flow in longitudinal valleys — the upper portion 

 of Franktown Creek ; Kings Canon Creek ; and the creek flowing 

 south from Snow Valley Peak. A number of smaller streams also 

 flow parallel to the range crest. 



In a crystalline complex faults must be largely inferred, and 

 many may exist without possible proof. A study of the physiog- 

 raphy will frequently do much to elucidate movements in the 

 rocks, but only with great care. In this portion of the Sierra 

 Nevada there are abundant physiographic features that can be 

 used as criteria of faulting, and the whole process is rendered 

 certain by the possibility first of applying exact strati graphic 

 evidence in deciphering the precise nature of the physiography, 

 and then applying the physiographic tests in the crystalline 

 rocks. 



The type-section across the range lies along the line of the old 

 river channel, west of the south end of Washoe Lake. Three 

 main ridge lines and three sub-ridges are developed. The strati- 

 graphic relations are clear. Seven fault-blocks are represented 

 in this section. Of the eight fault-planes bounding these blocks, 

 the existence of but one is not at once proved by the position of 

 the gravels. This is due to the fact that at this point the gravels 

 are scattered over the surface and no section across the fault- 

 plane is to be had. The proof of this fault is adduced through 

 the significance of the topography. A glance at the map on this 

 section shows the crest of a sub-ridge on the east of the fault- 

 plane, forming the apex of the block on that side. Both directly 

 and indirectly this crest of the block can be shown to be due to a 

 fault. First, this fault-line is an extension of the one so clearly 

 denned by displacement of plateau remnants on Snow Valley 

 Peak, and here separating the east and west summit ridges. Sec- 

 ondly, at every place where such sub-ridge crests occur within 

 the area, they can always be proven due to faulting when direct 

 evidence is obtainable. The old plateau surface was character- 



