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



the knotted schist described in the section north of Clayton valley. In 

 these rocks also no fossils were found. To the southeast of Cow Camp 

 springs are several areas composed of mica-schist, red and green slate, 

 with some quartzite and red marble. These areas afforded no fossils. 



The section along Barrel Spring ravine has already been referred to. 

 It abounds in fossils and is intruded at numerous points by dikes of acid 

 metamorphic lavas. A rough measurement of this series of beds along 

 Barrel Spring ravine placed the thickness at over 10,000 feet. Alcatraz 

 island and Goat island, in the Silver Peak marsh, are made up of 

 Olenellus slates and limestone. 



UPPER CAMBRIAN 



The Upper Cambrian is present in several portions of the quadrangle. 

 It consists at the base at some points of a red limestone breccia resting 

 with a distinct unconformity on the Lower Cambrian, as in the group 

 of hills lying 4 miles immediately east of Silver Peak village and at 

 the west side of the north part of the Silver Peak range 4 miles north- 

 east of the mill of the Pacific Borax Company, in Fish Lake valley. 

 Overlying the breccia are successively layers of thin bedded siliceous 

 argillite, thin gray slate showing faint impressions of graptolite remains, 

 brown slates, heavy beds of thin bedded dark limestone, red and brown 

 slate containing well preserved minute disk-shaped shells (linguloids), 

 some trilobites (Acrotreta), abundant fragments of Phyllocarida, and 

 some corals. 



This series is best developed in the vicinity of Emigrant pass, espe- 

 cially to the south of the Emigrant road, on the west side of the range. 

 The shells are well preserved and are regarded by C. D. Walcott as indi- 

 cating an Upper Cambrian age. The beds appear to conformably under- 

 lie the siliceous argillite and slate of the Ordovician, which is chiefly 

 characterized by graptolite remains. Moreover, the Phyllocarida, so 

 common in the Upper Cambrian, are found in layers interbedded with 

 the graptolite slates at the base of the Ordovician, and the linguloids of 

 the Upper Cambrian were found in slates but a few feet under the gray 

 graptolite slate, with no evident unconformity between. 



"While the Upper Cambrian rocks were found in nearly all parts of the 

 quadrangle, they are nowhere so rich in fossils as to the south of the 

 Emigrant road. In nearly all areas the thin bedded limestone forms a 

 conspicuous feature. In the area 5 miles east of B. M. 4996 no fossils 

 whatever were found, and this mass is assigned to the Upper Cambrian 

 largely because of its conformable position below the Ordovician siliceous 

 argillite. 



