Ui The American Geologist. August, 1894 
50* i" the north and a vertical thickness of about 5,000 feet. 
The thickness of the Tejon strata cannot be less than 1,000 
feet and is probably much more. The lower portion of the 
Tejon beds consists of white sandstones, sometimes much red- 
dened by iron oxide, and overlying the sandstone is a consid- 
erable body of white shale. This shale is beautifully exposed 
on the north side of a canyon which extends in an approxi- 
mately east and west direction, draining- westerly into San 
Carlos creek. This east and west canyon was named De los 
Reyes canyon. 
The Chico strata contain some conglomerate at the base of 
the series, the pebbles of which are of various rocks, quartz- 
porphyry pebbles being abundant. We did not detect this 
rock in place, however, in the area of older rocks to the south.* 
There are also some dark shales with limestone nodules in 
San Carlos creek above the New Idria P. O. : but tawny sand- 
stones comprise the bulk of the Chico strata at New Idria. 
and the line of contact of these tawny sandstones with the 
overlying white sandstones was used as the line of demarca- 
tion between the Chico and Tejon formations on the geologi- 
cal mapf of the New Idria district. The only determinable 
fossils in the Chico beds, however, came from near the base of 
the series, as stated in the quotation from Dr. White. The 
line of division is therefore an arbitrary one, but it is certain 
that the white sandstone is of Tejon age, since it contains 
characteristic i'ossils. As stated by Mr. Becker and Dr. White, 
the Chico and Tejon strata at New Idria are apparently con- 
formable, and this is likewise the case at Mount Diablo. t 
The following lists of fossils, collected chiefly by II. W. 
Turner, will aid the future student of the Chico-Tejon series 
there. All of them are from Tejon strata, overlying with ap- 
parent conformity the Chico series: 
l>< los Reyes canyon. — This drains into the canyon of San 
Carlos creek from the easl al a point one mile north, by com- 
*The abundance of ■ quartz-porphyrj or quartz-porphyrite pebbles in 
the conglomerate of the Chico formation a1 New Idria and at Mount l>ia- 
blo, and in the Knoxville beds at Knoxville, is rather remarkable, inas- 
much as mi quartz-porphyn was found in place in the areas i»t' older 
rocks al am of i hese points. 
[■Atlas accompanying monograph XIII. (J. S. Geol. Survey. 
; hull. Geol. Soc. Am., vol. n: II. W. Turner's paper on .Mi. Diablo. 
