Vor. IIT] ANDERSON—FURTHER STRATIGRAPHIC STUDY 29 
up as much as 20 percent of the aggregate thickness, to which 
their peculiar color and slightly greater induration give an 
exaggerated effect. The strata are essentially sandy through- 
out, though clays are abundant in their upper portion, espec- 
jally north of Coalinga and in the vicinity of Salt creek and 
the Cantua. In the former paper the Etchegoin beds were 
divided into two portions called respectively, the “Etchegoin 
Sands” and the “San Joaquin Clays.” 
The sands of this series are commonly coarse in texture 
and often pebbly, forming beds of conglomerate. Many of 
the pebbles and sand grains are jet black in color, and mingled 
with these is a kaolin-like matter, perhaps a decomposition 
product from volcanic ash. The gray-blue color which is so 
noticeable in these beds may be due to these ingredients and 
to their manner of mixture. This color has not been noticed 
in either of the other series and has generally been found to 
be a safe index to the identity of the Etchegoin beds. It has 
been noticed not only in the Coalinga field, but at McKittrick, 
near Buena Vista lake, at Mount Diablo, and on San Pablo 
bay. 
One or two fossil horizons are to be recognized in the 
Etchegoin beds,—one near their bottom and another some dis- 
tance above; but whether these are persistent or not cannot be 
stated. The most clearly defined and best characterized horizon 
includes some 400 feet of strata in which there are sometimes 
several separate beds of fossils. This horizon occurs near the 
bottom of the series and, as seen in the outcrops in the hills 
west and southwest of Coalinga, contains the following: 
(n) Brown sands with fossils........... 15 feet 
Gam) miGlavarshalesy WL au hivenee tome Bei 5 as AQhere 
Cl) ey Sandstone swath tossilsn domeeeene ee. I@ 
Co) Biuishi ray sandsi),.).. seer eaeae. : SoMa 
Lower fossil horizon 
(j) Gray sands, gravels, and clays ........ (sg) 
CP Sandstone with: fossils ueeaeeen aoe IQ) 
Gy sandsvand scandy (clays: seen ee 80 “ 
(a) eebiuishveray. sands. eae sees yee, 49 “ 
Ghee rAretllaceous: Satids wine Meme lee LOOtR 
Cre bluigaperay sands ).y aelurnedeuness BU 
Ca) Sandstone swith fossils) 24-69 02s ee 8 
