166 OIL DISTRICTS OF SOUTHERN CALIFORNIA. 
9 
the Fernando. There is also a more or less persistent layer of Pleisto¬ 
cene gravel, which caps the upturned edges of the older beds over 
portions of the terrace. 
The sandstone between the two white-shale layers, which is the 
principal oil sand in this as well as in the eastern field, consists of 
about 150 feet of coarse }^ellow arkose sandstone in layers 3 to 24 
inches thick, interbedded with minor quantities of fine gray shale. 
Good exposures of this sandstone are found on Court street immedi¬ 
ately west of Lake Shore avenue and also on Burlington avenue a 
short distance north of First street. In the region directly north of 
Westlake Park the color of this same band, which here approaches a 
grit in certain layers, varies from chocolate and purplish gray to 
brown. The discoloration is doubtless due to the petroleum which 
the sands at one time contained. Similar colors were noted in sands 
which are supposed to be stratigraphically equivalent on Sunset 
boulevard northwest of Echo Lake. (See PI. XXI, A.) 
Interbedded with the thin white shale which underlies the sand¬ 
stone are darker, softer shale and fine sandstone which locally appear 
to be petroliferous. A cut in First street west of Burtz street offers 
a good exposure of this oil-bearing shale. These beds occupy the 
hilly country north of the central field, lying in low folds with dips 
that vary from horizontal to 10° or 15° and showing no continuous 
lines of structure. As indicated by well records, they carry traces of 
petroleum as far east and north as the region immediately northwest 
of Echo Lake, but the accumulations are not of economic importance, 
as they are in the same beds northwest of Coronado street in the 
western field. 
The band of white shale above the main oil sand already described 
is not over 50 feet thick, but owing to the resistant qualities of the 
thin flinty laminae of which it is composed it can- be more easily 
traced along its surface outcrop than any other stratum in the 
region. Angular fragments of thin shale strew the surface of the 
ground throughout the greater part of the distance from Lake Shore 
avenue westward to a point 1 miles southeast of Colegrove. If it 
were not for this hard, flinty shale the difficulty of tracing the con¬ 
tinuity of the formations north of the central field would be greatly 
increased. 
Above this flinty shale band lie the soft conglomerate, heavy and 
thin-bedded fine-grained sandstone, and sandy and clayey shale of 
the Fernando. This formation is probably over 2,000 feet thick, only 
the lower part, however, being exposed in the central field. In this 
field the soft, thin-bedded sandstone is confined largely to the lower 
500 feet of the formation. This sandstone appears to be more or less 
petroliferous toward the west end of the field, and as a consequence 
its outcrop is stained rusty red, purple, and pink. This coloration of 
