1913] 



Louderback: The Monterey Series 



203 



Within the quadrangle itself it varies only up to about 500 feet 

 in thickness. 



The "Monterey shale" includes the clay shales and lime- 

 stones, and the siliceous shales in all from 5000-7000 feet thick. 

 He considers that it lies conformably over the Vaquero sandstone, 

 and states that "it seems probable that these sandstones and 

 conglomerates were in origin, partly at least, contemporaneous 

 with the bituminous Monterey shale, the former representing the 

 shore deposits, and the latter representing deposits formed at 

 a considerable distance from land." The "Monterey shale" is 

 also shown to contain volcanic ash beds. The conformable series. 

 Vaquero sandstone — Monterey shale, is separated from both 

 earlier and later deposits by marked unconformities. 



It will be noted that the separation of the series is on a purely 

 lithologic basis, and the Vaquero sandstones of one part of the 

 field are believed to be contemporaneous and to have originally 

 graded laterally into the Monterey shale in another part. They 

 are, therefore, merely depositional facies of the same series of 

 deposits, as believed by the present writer. The unfortunate 

 thing about Fairbanks' work is that he omitted the outward 

 sign of the essential unity that he believed in — the name of the 

 series as a whole, and presented it in his columnar section as 

 two separate entities, representing two different periods of depo- 

 sition, which idea his descriptions oppose. 



San Mateo County, Harhl and Arnold, 1904. — In this same 

 year (1904) Haehl and Arnold in discussing the "Miocene Dia- 

 base of the Santa Cruz Mountains in San Mateo County, Cali- 

 fornia," 42 presented these two divisions as representing different 

 time intervals, — different faunal stages. They described* "the 

 lower Miocene" as "a series two or three thousand feet thick of 

 massive, coarse, yellowish sandstone layers, interbedded with a 

 few layers of varying thickness of dark colored argillaceous shale, 

 the whole overlain by three or four hundred feet of thin bedded 

 siliceous shales. The lower part of this series of beds, including 

 most of the sandstone, appears to have the same fauna and occupy 

 the same stratigraphic position as the Vaquero sandstone of the 

 Salinas Valley. The name 'Vaquero' will, therefore, be used 



« Proc. Am. Phil. Soc, vol. 43, pp. 16-."3 (1 904). 



