GEOLOGY OF THE SOUTHERN COAST RANGES 561 
strike of the lower, as well as by the fact that the upper rests 
indiscriminately upon either the lower Cretaceous or the Golden 
Gate series. A nonconformity is also indicated by the fact 
that where the serpentine in this region, as in other portions of 
the Coast Ranges, comes in contact with the lower Cretaceous, 
the relation is one of intrusion while the Chico rests upon it 
undisturbed. The lower Cretaceous was intruded by the perido- 
tite, upturned and eroded before the deposition of the Chico. 
TERTIARY PERIOD. 
Strata of Middle Tertiary age are widely distributed over 
this region and probably once covered nearly the whole of it. 
The Eocene on the contrary is entirely absent although exten- 
sively developed to the southeast in Santa Barbara and Ventura 
counties. It seems probable that during early Tertiary time this 
portion of the Coast Ranges was above water for if the Eocene 
ever had existed here it would be reasonable to expect some 
remnant of it would be met with. .The Lower, Middle, and 
Upper Neocene are all represented. 
NEOCENE. 
Monterey series (Lower Neocene).—With the beginning of the 
Neocene a subsidance commenced and continued through, or 
nearly through the Miocene. Finally, almost the whole Coast 
Range region was submerged and a thickness of rocks in many 
places of more than 7000 feet was deposited. The most charac- 
teristic feature of the series is the bituminous shales. They 
form its upper portion and reach a thickness of 5000 feet. 
Below them are limestones, clays, volcanic ash, sandstones and 
conglomerates. Erosion has removed a large part of these 
rocks, but the similarity in succession of the characteristic hori- 
zons at various points in the area surveyed points to the fact of 
their former continuity. 
The sandstones and conglomerates at the bottom of the 
series are most prominently developed in the region lying east 
of the Rinconada Valley, between it and the main granite range. 
