.■4 URI FERGUS GRA VELS— INDEPENDENCE HILL FLORA 899 



on both sides of Lake Tahoe little or no movement seems to 

 have taken [)lace. Near Verdi the displacement was probably 

 smaller than turther south. There is, along the first line, excel- 

 lent evidence of the amount of the displacement. It probably 

 did not much exceed 2000 feet, while the aggregate amount of 

 both the late Cretaceous and the Miocene displacement is about 

 5000 feet near the latitude of the little town of Genoa, south of 

 Carson. The best evidence of this displacement is found in 

 the drainage of the West Fork of the Carson River, which from 

 a meandering course in Hope Valley, in Alpine county — the 

 topography of which accurately represents the pre-volcanic 

 Miocene surface — breaks through the eastern scarp in a wild 

 canyon of extremely steep grade, to again resume its meander- 

 ing course in the Carson Valley 2000 feet lower. 



Near the crest the range is at many places, as first pointed 

 out by Dr. G. F. Becker,^ intersected by a system of joint planes 

 on which small movements have taken place, which may aggre- 

 gate to considerable amounts. These joint systems, which 

 probably were produced about the close of the Neocene, appear 

 to accompany and supplement the large normal faults at the 

 eastern base. 



To sum up, the topography about Lake Tahoe has remained 

 similar to its present form probably since the close of the Cre- 

 taceous, while a late Miocene or Pliocene fault of 2000 feet has 

 been formed along the east side of the buttress lying to the 

 east of Lake Tahoe. The displacement here indicated is less 

 by several thousand feet than that shown by the grade of the 

 Neocene rivers as outlined in a previous paper ; this strengthens 

 the belief that we have here to deal with a composite movement, 

 one upward affecting a large area, and one downward consisting 

 of local sinking of moats. \\\ comparing this region with that 

 north of 39° 30' it should be borne in mind that, according to 

 the best evidence, the northerly part during the gravel period 

 stood at considerably lower elevations than the section about 

 Lake Tahoe, as indicated among other things by the absence of 



' Bull. Geol. Soc. Am., Vol. II, pp. 49-74. 



