286 CALIFORNIA ACADEMY OF SCIENCES. 



morphic sandstone appear to be conformable, the sand- 

 stone certainly underlying and probably overlying the 

 phthanite. Beyond that, the relations of the formations 

 to each other are not known. There appear to be two 

 beds of the Gavilan limestone, one of which at least is 

 several hundred feet thick. The limestone is found asso- 

 ciated with the metamorphic sandstone and metamorphic 

 slate, also with j-^ounger formations where brought up by 

 faulting. Dr. Becker,* in treating the rocks of the Gavilan 

 Range, calls the limestone the lowestrnember. Its age is 

 unknown. The phthanites, upon the evidence of Radio- 

 laria found in them, have been thought to be of Jurassic 

 or Cretaceous age.f In general, all the metamorphics 

 are thought to be pre-Cretaceous by Mr. H. W. Fair- 

 banks, t 



Above the metamorphics is a great thickness of sand- 

 stones and shale, frequently thin bedded, topped by heavy 

 beds of conglomerate, which, to distinguish, we have 

 called the 



Pescadero Series. — This series comprises all the upper 

 portion of what has been known as the San Francisco 

 sandstone, also rocks thought to be Eocene, and at the 

 top heavy beds of conglomerate which contain Miocene 

 fossils. The relation between this series and the meta- 

 morphic rocks below was not made out, all or nearly 

 all the evidence seeming to indicate that there was no 

 break between this series and the metamorphic sandstone 

 and phthanite below. However, as nearly all the geolo- 

 gists at present actively engaged in studying the meta- 

 morphic rocks agree in placing them unconformably 

 below the lowest Cretaceous and as the Pescadero series 



*U. S. Geol. Surv. Monograph xiii, p. 181. 



tBiill. Dept. of Geol., U. of Cal., vol. i, p. 237, Oct., 1894. 



t American Geologist, vol. ix. Mar. 1892, p. 163. 



