Vol. 6] Beid: The Geomorphogeny of the Sierra Nevada. 



97 



show silicification, or better, metasomatic replacement of the 

 original rock by quartz and epidote. The Lakeview rocks were 

 originally probably limestone, perhaps somewhat impure, yet 

 needing the addition of silica from extraneous sources for the 

 formation of the large quantity of lime-bearing silicates. The 

 mineralogy and petrography of the whole metamorphic area 

 needs and deserves attention. There is a widespread dissemina- 

 tion of chalcopyrite and bornite, which has caused considerable 

 prospecting west of Carson. Free gold is also found near Kings 

 Canon in the schists, and seems to be connected with the granitic 

 intrusion and metasomatic changes in the older rocks. 



The Roof of the Batholith. — The irruptive contact is noted 

 for a number of springs, particularly at Cemetary Hill, a mile 

 north of Carson, and at the schist area further north, east of 

 Washoe Lake. This surface, though locally irregular, yet shows 

 in its larger form nearly a plain, with occasional blocks sunk into 

 the granodiorite. At present most of the fragments of the old 

 roof of the batholith are more nearly horizontal than vertical, 

 some quite so. The variations to vertical or highly inclined can 

 be traced to deformation of crust blocks. It is probable that the 

 original contact surface lay nearly horizontal in this area, with, 

 of course, sharp local modifications. Contacts now dip toward 

 the valleys away from the summits. North of Carson the dip is 

 southerly ; west of the town it is easterly. The Lakeview Hill 

 block shows a highly inclined contact plane with a southerly 

 dip, placing this block strictly with the Virginia Range rather 

 than with the Sierra. 



The areas of metamorphics at Genoa Peak and west of Carson 

 show a very gentle easterly dip of the contact. Near Glenbrook 

 the dip is westerly toward the lake. 



The Superjacent Series. 

 River Gravels. — The oldest member of the later rocks present 

 in the area consists of the gravels of a Neocene river channel ly- 

 ing between Lake Tahoe and Washoe Valley, with traces in the 

 Virginia Range. This channel presents one of the many inter- 

 esting features of the region, and because it crosses completely 

 the great fault zone, it possesses an additional value in decipher- 



