

■ 



GEOLOGY OF THE SIERRA NEVADA 



°3 



able number of thin shells lapped over each other, like the coats of an 

 onion.* 



This structural arrangement of the granitic masses exhibits itself in a 

 great variety of forms, according as more or less of the original dome has 

 disappeared, either from actual engulfment or from the action of erosive 

 forces. The " dome-structure " of the granite, as it has been called in Geol. 

 ^ is by no means peculiar to the Californian mountains; on the contrary, 

 it is most conspicuously displayed in many other parts of the world, although 

 perhaps nowhere on so grand a scale as in the Sierra Nevada. It was first 

 noticed and described by Von Buch as occurring in the Harz, in the Scandi- 

 navian Range, and in many other regions.! The same phenomena have also 

 been described and figured by Ilelmersen.J 



No one who has studied the Sierra Nevada with any care can doubt the 

 eruptive origin of the granitic nucleus or axis of that chain. The remark- 

 ably homogeneous character of the rock over such a vast area adds weiirht 



to the evidence of an intrusive origin of the granite furnished by its position 

 Hi reference to the sedimentary strata with which it is connected. The inti- 

 mate connection of the volcanic deposits of the Sierra with the granite must 

 ftlso be considered in reference to this question, as will be noticed farthe 



r on. 



I he epoch of the granitic outburst may best be indicated after having made 

 some acquaintance with the geology of the stratified deposits through which 

 ^ has made its way to the surface. 



Of the lithological character of the auriferous slate scries — the bed-rock of 

 'he miners, as already explained — we shall have frequent occasion to speak 

 m the detailed descriptions of the overlying formations, to be given in the 

 next chapter. A few general remarks in regard to the nature of the rocks 

 °i which this series is made up may, however, be introduced at this point, 

 ^nd it will be desirable first to give a brief synopsis of what is known in 

 re gard to their geological age. 



I he geological age of the auriferous rocks of the Sierra Nevada had 

 remained, up to the time of the beginning of the work of the Californian 



a nis is well seen in the photograph of Monnt Hoffmann, in the " Yosemite Book," also in several of 

 anss series of photographs of the Yosemite and its surroundings. See also Geol. I., for a number 



sections and cuts illustrative of this structural arrangement of the granitic masses of the Southern 

 High Sierra. 



+ See Abhandlnngen der Akademie der Wissenschaften zn Berlin. 1842. pp. 57. 



t Memoirs of (he St. Petersburg Academy. Vol. XIV. No. 7, 1889. Stndien iiber die Wanderblocke 



1111(1 clie Muvialgebilde Russlands. 



