198 



University of California Publications. 



[Geology 



Structure and Genesis of Mt. Davidson. — Mt. Davidson is a 

 diorite mass bounded on all sides by faults, and has risen rela- 

 tively to the surrounding country. The Comstock lode occupies 

 the fissure made by the east fault bounding the mass. The west 

 fault now shown in the Hale and Norcross tunnel is not occupied 

 by a vein in the tunnel, because the compressive stresses have 

 been too great. Farther search, both along this fault, and partic- 

 ularly farther west, may easily result in the finding of ore. There 

 are no reasons for assuming the non-existence of ore in the west 

 country, nor elsewhere in the faulted region surrounding Mt. 

 Davidson, especially to the south, where the country is more frac- 

 tured and broken. 



A further word concerning Mt. Davidson may not be amiss, 

 although the subject has not been fully investigated, on account 

 of the time necessary. On the Carson sheet* the mass of Mt. 

 Davidson is seen to be a roughly rectangular mass approximately 

 two by one and one-half miles, with the major axis north and 

 south, bounded on all sides by steep slopes. The eastern slope 

 is noted for the Comstock lode. The surface of this mountain 

 mass is that of an old eroded region, as noted by Becker t (page 

 184 et seq.), which has been uplifted above the surrounding 

 country. One standing on the summit of Mt. Davidson cannot 

 fail to be struck with the mature character of the topography. 

 This eroded, gently rolling surface exists well preserved in the 

 Sierra Nevada to the west, now broken and displaced by later 

 faulting action. The history of the Sierra and Virginia ranges is 

 identical in the main features. These statements will be proved 

 by a citation of facts in a subsequent paper now in preparation. 

 The results of this conception are obvious and far reaching. The 

 location of the Comstock is well known on the east. On the 

 south are other ore bodies in the American Flat region, but all 

 of the south has not been prospected. One well developed west 

 fault has recently been shown in the Hale and Norcross tunnel, 

 and more will follow. The maximum faulting on the west is 

 farther to the west than the present face of this tunnel. To the 



* Carson Topographic Sheet, U. S. G. S. 

 t G. F. Becker, op. cit. 



