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



by Mr Spurr, and this map may assist the reader of the present paper 

 in getting an idea of the geology of this interesting region. Many 

 Cambrian fossils were collected, mostly in an excellent state of preser- 

 vation, which, with others obtained later by F. B. Weeks, probably will 

 be made the basis of future publications by the U. S. Geological Survey. 



On his generalized geological map the rocks here included under "pre- 

 Cambrian complex" are called by Spurr "Intrusive granitic rocks com- 

 plexly injecting Paleozoic strata/ 7 This, however, is misleading, inas- 

 much as the complex is composed largely of gneisses and schists which 

 were probably made gneissic and schistose before the Cambrian was laid 

 down, and in that case would not be intrusive in the Cambrian. How- 

 ever, the white granite and pegmatite associated with these ancient 

 gneisses are intrusive to some extent in the basal green schists, quartzite, 

 and dolomite which underlie the fossiliferous Cambrian rocks. As this 

 white granite is intimately associated with the pre-Cambrian, it was 

 mapped and described as a part of the pre-Cambrian complex, although 

 evidently later in age than the bulk of the gneisses and schists which are 

 intruded by it. This latter granite (alaskite of Spurr) and pegmatite 

 was nowhere seen intruded in fossiliferous Cambrian rocks. 



The evidence of the continuity of sedimentation from the Upper Cam- 

 brian into the graptolite beds of the Ordovician appears to be quite 

 plain in one section near Emigrant pass, at the north end of the Silver 

 Peak range. Further collections from this section should bring forth 

 interesting data. There is probably no field in Nevada where there are 

 better exposures of the older Paleozoic series, and the region merits fuller 

 investigation. 



Geographic Features 

 extent and topography of the quadrangle 



The Silver Peak quadrangle comprises a portion of the Great basin 

 lying immediately east of the Inyo mountains. It is thus in the western 

 part of the Basin region. It is limited by the parallels of 37° 30' and 

 38° north latitude and by the meridians 117° 30' and 118° west longi- 

 tude. The larger portion of the area lies in Esmeralda county, Nevada, 

 but the extreme southwest corner is in Mono county, California. There 

 are portions of several mountain groups represented in the quadrangle, 

 including nearly all of the Silver Peak range. In the northeast corner 

 are the foothills of Lone mountain ; along the east border are the foothills 

 of the Montezuma mountains; near the southeast border the Palmetto 

 mountains, and the hills in the extreme southwest corner belong to the 



