TERTIARY AND QUATERNARY DEFORMATION. I"21 



uplifts, is in fact principally the result of a very complicated system of 

 orographic movements. These are clearly shown by dislocations of Ter- 

 tiary and Quaternary deposits which I have surveyed and mapped, but 

 to describe them is not practicable within the limits of this preliminary 

 paper. The main features for the present purpose are the eastern and 

 western divisions of the range, the intermediate mountain Claremont, 

 and the depression partly occupied by the American valley on the north- 

 eastern side of this mountain and Spanish ranch and Meadow valley on 

 the southwestern side of it, which depression is drained by Spanish creek 

 and its branches. Some of the principal elevations above sea-level are: 

 Outlet of American valley. 3,353 feet : outlet of Spanish ranch, 3,618 feet : 

 highest point on Grizzly ridge (barometrical), 7,952 feci ; Spanish peak 

 (barometrical), 6,990 feet; Claremont. 6,962 feet, 



Pre-Mesozok: Rocks. 



Eruptive Granite. — The principal exposures of the pre-Mesozoic rocks 

 in the Sierra are the two areas of greatest uplifting already described. 

 The eastern one extends from the southern end of the range to the 

 northern flank of mount Haskell, between the North Yuba and the 

 Middle Feather, where the pre-Mesozoic rocks pass beneath the Mesozoic. 

 The western area of pre-Mesozoic rocks extends from the northern end of 

 the range to the Great valley between Yuba and American rivers. Both 

 areas include isolated and peninsular tracts of Mesozoic rocks. 



The granites form by far the greater part of the pre-Mesozoic rocks; 

 indeed, they make up the core and the great mass of the range and of 

 each of the two divisions of the range. I have not seen granite over- 

 Lying or penetrating sedimentary strata in the Sierra proper, but on the 

 easterly slope of one of the nearer basin ranges, a little south of Beck- 

 worth pa.-s i which is at the In 'ad of the Middle fork of the Feather), there 

 are dike-; of granite penetrating gneiss. I must add that my observations 

 of the granites have been, with few exceptions, limited to the northern 

 half of the range. 



Sedimentary Slates "nil Quartzites. — While the core and mass of Spanish 

 peak mountain are of granite,* and the upper part of its eastern lace is 

 also of granite, lower down on this face, next to the granites, a series of 

 slates ami quartzites outcrop. The quartzites are evidently the slates, 

 altered by silicificatiori, for they retain the slaty structure, sometimes 



♦ Professor LWendell who kindly exumined microscopically a specimen < ' m it <■ 



fur , wrote of it, October 22, 1888: "The Spanish p . ortho dase, phigio- 



. ! i . . hornblende and biotiti litil constituents; this makes it :i hornblende-grunitit< 



nbusch), li i- ili'- in.-- 1 widely spread granitic rock in ling t" m 



experience." 1 1 cerl duly is the prevailing granite of the northern half of th • range. 



I. VII I- B Six . \<i.. \ in.. '■. 1891, 



