20 AURIFEROUS GRAVELS OF THE SIERRA NEVADA. 
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- 
tinuation of the San Gabriel Range, and connects, in the region between the 
Cafiada 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. 50° 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. With the Creta- 
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 
