148 
OIL DISTRICTS OF SOUTHERN CALIFORNIA. 
Trochita costellata Conrad (PL XXXII, fig. 3). 
Trochita cf. inornata Gabb. 
Trophon sp. 
Turbo topangensis Arnold (PL XXVIII, fig. 6). 
Turritella ocoyana Conrad (Pl. XLI, figs. 7, 8, 9). 
Turritella variata Conrad (Pl. XLI, figs. 10, 11, 12). 
The above fossils indicate that the beds in which they occur are of 
lower Miocene age and probably equivalent in general to the Vaqueros 
sandstone of central California. 
UPPER PUENTE SHALE. 
GENERAL CHARACTER. 
Above the massive-bedded Puente sandstone and grading into it 
is a mass of strata at least 2,000 feet thick, in which shale beds of 
one sort or another largely predominate. No sharp line of demarca¬ 
tion separates this shale from the sandstone beneath, but as a whole 
they are radically unlike. The two members are differentiated on 
the map (Pl. XVIII) along a line which, it is thought, marks the 
boundary between the preponderance of the sandstone facies on the 
one hand and the preponderance of the shale on the other. The shale 
in the region north of Los Angeles may be roughly divided into two 
approximately equal parts, the lower 1,000 feet consisting of broad 
bands of thinly laminated white to gray shale interbedded with 
similar bands of more or less thick-bedded, coarse yellowish to brown 
sandstone, and the upper 1,000 feet or more being characterized by 
thin-bedded sandy and clayey shale and thin to medium bedded 
sandstone. At the top of the shale series is a band of thin-bedded 
hard white siliceous shale, interstratified with 2 to 4 inch layers of 
brown sandstone. The top of this band is used in mapping as the 
arbitrary line between the Puente formation and the overlying Fer¬ 
nando (Pliocene) sandstone. 
Most of the shale in the lower part of the member, and also many 
of the shale beds interstratified with the Puente sandstone, are of the 
hard white siliceous variety characteristic of the Monterey shale in 
the Coast Range. This shale splits easily along the bedding planes 
into thin, sharp-cornered plates. Fragments of these scales or plates, 
which are very resistant to weathering, are often found scattered 
over the ground and thus indicate the presence of the beds over areas 
in which outcrops may be rare. Abundant minute organic remains 
are usually found in the siliceous layers, but no recognizable mollus- 
can forms have so far been obtained from them in this region. In 
the territory northeast of Los Angeles the structure is complex and 
an exact determination of the position of the shale is impossible; but 
it is probable that most of it belongs to the upper part of the Puente 
formation. In the vicinity of Sycamore Park the rock consists of 
