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Mesozoic and Cenozoic Geology and Paleontology. 19 
sandstones, without any appearance of eruptive rock, and also with 
very little metamorphism. 
. The unaltered sandstones extending along the Gavilian Range, near 
the San Juan valley, and forming the San Juan hills, which extend to 
the Pajaro river, are referred to the Miocene. In these hills the strata 
are very heavy bedded, and have a dip everywhere to the south. The 
materials of which they are made up are often coarse, and sometimes 
large enough to form a conglomerate, among the pebbles of which jas- 
per and other metamorphic rocks predominate. 
In the vicinity of the Bay of Monterey the granite is flanked by Mi- 
ocene sandstone. Both rocks are considerably altered, for a distance 
of about 20 feet from the junction; the sandstone is softened and dis- 
integrated, and the granite discolored. The metamorphism has so af- 
fected both rocks that it is not easy to determine the exact line of 
junction. 
The Miocene sandstones are displayed in some places in the region 
between the Canada de las Uvas and Soledad Pass, nearly 2,500 feet 
in-thickness, From the summit of the higher upturned strata, a wide 
belt of Tertiary rocks may be seen skirting the Coast Ranges, and 
worn into rounded hills, which are generally barren, especially on the 
west side of the Tulare valley. 
The Pliocene beds between Merced Lake and Mussel Point, on the 
peninsula of San Francisco, are made up of a bluish sandstone, of 
which the grains are cemented by carbonate of lime, interstratified with 
hard, fine conglomerates, of which the pebbles are evidently derived 
- from the adjacent jaspery rocks of Cretaceous uge. These strata con- 
tain Scutella interlineata, Crepidula princeps, both of which are ex- 
tinct, together with several species still living on the coast. 
At the head of Pleasant valley, the strata are overlaid by beds of 
volcanic ashes, interstratified with gravels, the whole series being con- 
formable and dipping at a low angle tothe east. They appear to be of 
Pliocene age, and identical in most respects with the sedimentary vol- 
canic beds to the north of Kirker’s Pass. 
To the north of San Pablo are low hills of very recent strata, which 
are nearly horizontal, and which rest unconformably on the edges of 
the Tertiary. They are referred to Post-pliocene age. 
From Tres Pinos, 13 miles from San Juan, to Booker’s, a distance of 
about 13 miles in a direct line, the road follows the Arroyo Joaquim 
Soto, a branch of the San Benito. Along this road there are vast de- 
posits of gravel, or entirely unconsolidated detritus, and which form a 
