GEOLOGY OF THE SOUTHERN COAST RANGES 567 
studied, and no detailed description will be attempted in the 
present paper. 
In the following outline the main types of igneous rocks 
occurring in this field will be given and arranged in groups 
according to age: 
Granite, - - - - - - [Earlier than the Jurassic. 
arlier than the Cretaceous. Intru- 
Peridotite, - S ° : sive in Golden Gate series. 
Basalt, intrusives and surface flows, } E 
Diabase, - - - - - \ 
Earlier than the Middle Cretaceous. 
Possibly pre-Cretaceous. Intrusive 
in Golden Gate series. 
Dacite granophyre, - = = 
Andesite granophyre,-— - - 
Earlier than the Chico. Intrusive in 
Diabase, - : 5 <I :: Knoxville beds. 
l 
) 
Peridotite serpentine and _ related jeoties than the Chico. Intrusive 
feldspathic rocks, including dia- ' in the Knoxville and preceding 
base, gabbro, and pyroxenite, - diabase. 
Rhyolite,  - - - - - 
Augite teschenite, and olivine dia- | All probably earlier than San Pablo 
base, - : - : - - + formation. Intrusive in Monterey 
Quartz basalt, - - - - lee Seniess 
Biaszilis’ < - - - = } 
The granite covers a large extent of country east of the upper 
Salinas River. It is remarkably uniform, consisting of quartz, 
biotite, orthoclase, plagioclase, and titantite. Large orthoclase 
phenocrysts give a porphyritic aspect in places. Numerous 
dikes of a finer-grained granite intersect it. Nothing is known 
concerning the age of the granite, save that it forms the south- 
eastern continuation of the crystalline axis of western Monterey 
county, on which the Golden Gate series rests with a basal con- 
glomerate. It is certainly much older than the Jurassic. 
The dikes of basic pre-Cretaceous intrusives in the Golden 
Gate series are almost innumerable, and, as they are generally 
much altered, weather away readily and are difficult to map 
accurately. Owing to the disturbances which the series has 
undergone, it is also almost impossible to distinguish in all cases 
the surface basalts from the dikes with similar appearance. The 
