Vol. 6] Eeid: The Geomorphogeny of the Sierra Nevada. 121 



both flowing in deeply notched canons. Very little water flows 

 in either branch except during stormy weather. The granodiorite 

 appears to be peculiarly nonresistant to stream erosion along the 

 drainage lines and great quantities of coarse granite have been 

 deposited on the alluvial fan below. For the reasons already 

 given, in this area of rocks that possess slight variations in re- 

 sistance to erosion, such condition is best explained as the result 

 of rock fracturing and weakening along fault planes. And on 

 both branches there are granite walls that can hardly be regarded 

 as other than fault-scarps. Furthermore, there is another bit of 

 evidence to substantiate the idea of faulting. The plateau rem- 

 nant east of Marlett Lake ends abruptly against a fault-scarp 

 striking nearly east-west. This scarp is proved to be due to a 

 fault by the hypsometric discordance between the two nearby 

 plateau remnants. The prolongation of the line of this scarp 

 leads directly to the line of the south fork of the creek just dis- 

 cussed. There is a well-developed scarp between this line and 

 Ash Canon, and no stream has ever cut at its base. 



More examples of east-west faulting and drainage following 

 these faults could be given, but there is no need. Sufficient facts 

 have been cited to show the great number of east-west cross- 

 faults, with the consequent drainage. 



Of the north-south consequent streams there are a number 

 of good examples in the Carson topographic area. The upper 

 part of Franktown Creek is clearly flowing in a longitudinal 

 valley due to faulting, as shown in the section along the old river 

 channel. The small creeks at the southwest corner of Washoe 

 Valley are likewise longitudinal streams. A fine example of such 

 a stream is found just south of Marlett Lake, west of Snow Val- 

 ley Peak. The faults which have resulted in the down-dropped 

 block under the lake appear to have converged and joined west of 

 Snow Valley Peak, and continued southward along the line of 

 the creek just noted. The origin of the canon is proved by the 

 existence of this fault line prolonged from the north, in the pres- 

 ence of steep unnotched granite fault-scarps ; and the dislocation 

 of the old plateau surface. The upper portion of this canon is 

 almost U-shaped, very suggestive of glacial action. The complete 

 absence of glacial deposits and scorings, the uniform disintegra- 



