20 



AUPJFEKOUS GEAVELS OF THE SIERRA NEVADA 



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ings at various times since 1841. The granite comes in to the northeast of 

 the metamorphic Tertiary (and perhaps, in part, Cretaceous) rocks, and forms 

 the divide between the branches of the Santa Clara and the Great Basin, or 

 Mohave Desert, the edge of this granite, next the plain, being overlain with 

 stratified beds of recent volcanic materials. This granitic belt forms the con- 



r 



initiation of the San Gabriel Range, and connects, in the region between the 

 Canada de las Uvas and the Tejon Pass, with the great metamorphic and 

 granitic masses of the Sierra Nevada, the crystalline rocks being apparently 

 continuous, but the disturbance and upheaval of the Tertiary and Cretaceous 

 formations not being discernible to the east of the Tejon Pass. 



All these Miocene strata of the Santa Inez and San Rafael chains belong 

 to the east and west system of upheaval, already noticed as characterizing 

 this part of the Coast Ranges. The principal disturbance of the strata must 

 here have occurred at the close of the Miocene epoch, since the Pliocene is 

 everywhere unconformably deposited on the underlying strata in a nearly 

 horizontal position, as also quite unaltered. 



Leaving Santa Barbara and Ventura counties, and passing northward into 

 San Luis Obispo, Monterey, and Santa Clara to the Bay of San Francisco, 

 we find the trend of the ranges, as before noticed, to be almost uniformly 

 parallel with the coast, which here runs about N. 30° W. The same sand- 

 stones and bituminous shales with which we have already become acquainted 

 form the mass of the mountains, until we reach a point opposite the north 

 end of Tulare Lake, which may properly be considered as the southern ex- 

 tremity of the Monte Diablo Range. Here the Cretaceous group begins 

 to form a part of the Coast Ranges, making up almost the whole of that 

 member of them which lies east of the San Benito River, 

 ceous appear granitic and highly metamorphic granitoid rocks, which are 

 developed in considerable quantity in the Gavilan Range, as well as in the 

 Santa Lucia Mountains. This latter range extends along the coast from 

 Point Pinos to San Luis Obispo, and, being almost inaccessible from the quan- 

 tity of chaparral with which its ragged slopes are covered, has received but 

 little attention from the Geological Survey. The Miocene Tertiary, and the 

 Cretaceous rocks in the region north of the 36th parallel, as far as Monte 

 Diablo, are also much metamorphosed over irregular areas ; and, when so 

 changed, the planes of stratification cannot usually be satisfactorily made 

 out. The ranges are, however, chiefly monoclinal, the valleys sometimes 

 occupying the bottom of synclinal curves. The Cretaceous mass of the 



With 







