260 H. W. TURNER GEOLOGY OF THE SILVER PEAK QUADRANGLE 



true of nearly all occurrences in these foothills. An exception is to be 

 noted in the basin 6.5 miles southeast of Cow camp, where there is a later 

 white pumice (presumably rhyolitic) overlying andesite-breccia and con- 

 glomerate. This pumice should probably be correlated with the pumice 

 beds of the Monocline, which are possibly of early Pleistocene age. 



LATITE 



The alkali-rich andesite or latite of the ridges north of Piper peak 

 distinctly overlies the rhyolite-tuffs of that region. 



LATER DACITE 



The occurrence of a dacite near the base of the Esmeralda formation, 

 at the north end of the Silver Peak range, has already been noted. This 

 is undoubtedly older than the bulk of the true rhyolites. At many points 

 there are layers of a later dacite intercalated in the rhyolitic tuffs. This 

 is the dark glassy variety represented by analysis number 53. These 

 layers can be seen along the south base of Ehyolite ridge and to the 

 southwest of Piper peak as well as at many other points. We thus have 

 eruptions of dacite of two periods — one near the beginning and one near 

 the middle of the Tertiary volcanic period. 



HYPERSTHENE-BASALT 



The coarse basalt of the Piper Peak ridge overlies rhyolitic pumice at 

 many points. It also overlies the massive alkali-rich andesite or latite of 

 the north end of the high ridge that extends north from Piper peak. 



OLIVINE-BA SALT 



An older basalt has already been referred to. Near the west end of 

 Piper peak ridge there are olivine-basalts which form layers in rhyolitic 

 tuffs and gravel beds; but these layers are pretty certainly intruded 

 sheets and of the same age as the similar basalts which cap the same 

 gravels of the Esmeralda formation in the vicinity. Basalt overlies 

 andesite about 2 miles northeast of Barrel spring. 



Olivine-basalt overlies rhyolitic tuffs and pumice at the Monocline and 

 other neighboring points; also on the high butte 5 miles southwest of 

 Silver Peak ; also on the table mountain 5 miles southwest of Piper peak, 

 and, as already noted, on the high ridge west of Ice House canyon. In 

 general it may be said that the basalts form the latest lavas of the 

 quadrangle. 



PLEISTOCENE BASALT 



Finally there may be mentioned the basalt of the Clayton Valley crater, 

 undoubtedly of Pleistocene age and representing the last volcanic erup- 

 tion of the quadrangle. 



