PALEOZOIC SEDIMENTARY SERIES 243 



The Upper Cambrian beds in the Silver Peak range dip usually to the 

 northeast. In the area 5 miles east of B. M. 4996 they dip easterly, and 

 in the area just east of the Clayton marsh they dip northwest. 



THE ORDOVICIAN SEDIMENTS 



Overlying the Upper Cambrian rocks are thin, black, gray and red 

 slates interbedded with layers of black siliceous argillite and sandstone. 

 The slates contain at a great number of points very abundant graptolites. 

 As noted under the Upper Cambrian, there appears to have been a con- 

 tinuous deposition of sediment from Upper Cambrian time to the Tren- 

 ton horizon of the Ordovician. 



The collections of graptolites were examined by Mr Charles Schuchert, 

 who states that there are two horizons represented — one the Normanskill 

 or lower Trentonian, and the other the Quebec horizon. Nearly all of the 

 graptolites, however, belong to the Normanskill zone. In the Quebec 

 horizon Mr Schuchert found two characteristic genera, Didymograptus 

 and Tetragraptus. 



In the Palmetto mountains and at some other points there are very 

 numerous streaks of light colored felsitic rocks interbedded with the dark 

 siliceous argillite of the Normanskill zone. The microscope shows that 

 the felsitic layers are chiefly old rhyolitic or dacitic lavas and tuffs. It 

 is thus certain that in Ordovician time there were volcanic eruptions in 

 the region. Certain other light colored felsitic-looking layers are in part 

 metamorphosed into garnet, pyroxene, and calcite and epidote. 



Nearly all the north end of the Silver Peak range is composed, where 

 not covered with rhyolite, of the cherts and slates of the Ordovician, 

 containing at several points recognizable graptolites. At many places 

 these beds are highly contorted and faulted and dip in various directions 

 at high angles, the general strike, however, being nearly east and west. 

 At some localities they are intersected by veins of calcite, but no quartz 

 veins were noted in them. In the neighborhood of the Emigrant pass, 

 both to the north and south of the Emigrant road, graptolites may be 

 found in the rocks at many points. In nearly all of this district the beds 

 dip in an easterly direction. 



Tertiary Sedimentary Series 

 esmeralda formation 



General character. — In the central and northern part of the quad- 

 rangle there are beds of light colored marls, slates, and sandstone which 

 were laid down in the waters of a lake. They are designated the "Esme- 



