Vol. 4] Smith. — Upper Region of Main Walker River. 



3 



formity upon the worn surface of the Bedrock Complex, com- 

 prises Tertiary sandstones and conglomerates together with an 

 earlier and a later andesite, andesitic tuft' and breccia, rhyolite 

 and basalt. These Tertiary rocks have a prevailingly westward 

 dip and are repeatedly monoclinal. Still later in age, lying hori- 

 zontally upon these arc beds which arc questionably Quaternary 

 or late Tertiary, and also formations of undoubtedly Quaternary 

 age. The ridges bound areas that are rudely rectangular. Min- 

 eral veins are numerous, and several of these possess value. 



PHYSICAL FEATURES OP THE REGION. 



The immediate area mapped is shown on the two accompany- 

 ing plates, 1 and 2. The second is a continuation of the first 

 at the southeast corner, and contains one ridge, Whirlwind 

 Mountain. PL 1 contains three, two of which entirely cross 

 the area ; the other lies along the western border part way. Their 

 trend is northerly and southerly, and between each are valleys 

 having long alluvial slopes to the west ; much shorter slopes come 

 down to meet these slopes from the west, in which event they 

 meet along a line, but in some instances they meet on a margin 

 of a plain or piaya. Where the meeting is along a line it may 

 be readily recognized as an axis of drainage. These two fea- 

 tures, the line and plain, may meet, and if the latter has a suffi- 

 ciently low outlet the drainage line is continued toward the out- 

 let. As the western slope of the alluvium is much the longer, 

 so also is the slope above the alluvium toward the crest of the 

 more or less bare rock. The eastern slope is much the steeper 

 as well as the shorter. 



The westernmost or first ridge is separated from the second 1 

 by a broad canon which is rather too wide to be termed a canon 

 and may be designated a canon-valley, and is known as Churchill 

 Canon. The northward extension of this valley is a canon from 

 the west. This canon disconnects the first ridge at its northern 

 end from a plateau or "benchland," a portion of which comes 



1 Mr. C. H. Asbury of the Carson Indian School was very kind in endeav- 

 oring to obtain the Indian name of this ridge. Through Mr. E. C. Dyer, 

 an interpreter, he ascertained that its name was Sing-ats '-e. 



