Vol. 6] Beid: The Geomorphogeny of the Sierra Nevada. 141 



Range actually meet and their union is made perfectly evident. 

 On Lakeview Hill the contact plane of granodiorite and schist 

 dips south, entirely different from the adjacent area, on the 

 block just west, that dips east. The contact plane north of Car- 

 son likewise dips southerly. Lakeview Hill, therefore, is struc- 

 turally a part of the Washoe Mountains, and not of the Sierra 

 Nevada. The latter range is bounded strictly on the east by a 

 line of north-south faulting only. A further bond of union is 

 established between the ranges by the presence upon the hills 

 north of Carson of horizontal remains of the old erosional surface. 

 A view southwest from the town shows the hills east of Lakeview 

 as flat-topped as if smoothed by a giant plane. The presence of 

 the Tertiary gravels in these hills is evidence of the same order. 

 Small areas of schist are found in the Pine Nut Range east of the 

 map limits. Granite occurs southeast of Mt. Davidson, in the 

 Virginia Range. It is evident that the older rocks form the base- 

 ment upon which rest the vast thickness of lavas that make up 

 the main mass of the Nevada ranges. This basement must be 

 broken and displaced in a complex manner, as proven by the 

 varying elevations at which the several areas of older rocks are 

 found. 



From the field investigations of the writer, the diorite of Mt. 

 Davidson is of indefinite relationship to the older and later rocks. 

 If the Davidson plateau be the correlative of the plateau in the 

 Sierra Nevada, that antedates the period of vulcanism there, and 

 if the various volcanics of the two ranges be of similar ages, we 

 may need to reopen the Comstock question of ages and identi- 

 ties of the various eruptive rocks upon this new basis, for a final 

 settlement. However, from the various outcrops of those rocks 

 that belong unquestionably to the Basement Complex, it would 

 appear that in general the upper limits of these rocks slope 

 gently downward to the east. 



Just beyond the Pine Nut Range to the east lies Smith Valley, 

 and this is bounded on the east by another north-south range, 

 the Sing-ats-e. Here the volcanic rocks are again in relatively 

 small amount, with corresponding large development of old sedi- 

 mentaries intruded by granitic rocks. 8 The structure of the 



s Of. D. T. Smith, Univ. Calif. Publ., Bull. Dept. Geol., vol. 4, no. 1. 



