192 
OIL DISTRICTS OF SOUTHERN CALIFORNIA. 
southeast, although there are some indications of steep northerly 
dips immediately southeast of the lagoon. The superficial or Pleis¬ 
tocene deposits become thicker and coarser toward the southeast, 
those in the SE. I sec. 28 attaining a thickness of 190 feet and con¬ 
sisting of clay in the upper 20 feet and sand and gravel in the lower 
portion. Deposits of asphaltum appear to be common at the base 
of the Pleistocene, and in at least one of the wells heavy oil was 
encountered not far below the middle of the formation. (See fig. 
17.) Water is usually found in these superficial beds, as in the area 
north of the lagoon. 
From the base of the Pleistocene down to the bottom of the deepest 
wells the rocks appear to be largely clayey shale, interbedded at 
varying intervals with hard “shell” layers. Some sandy beds and 
a few pebbly lenses are also encountered in drilling. Indications 
of oil are abundant throughout certain horizons of the shale, but no 
really important productive sands have yet been found in the area. 
The wells near the lagoon on the south strike moderately productive 
sands between 700 and 1,000 feet, while those somewhat farther 
away get good showings of oil at less depths. In the territory a mile 
or so southeast of the lagoon the shale contains here and there thin 
oil-bearing strata beneath the “shell” beds from 400 feet down, but 
nothing approaching a pay sand has been reached here. Salt water 
is reported as very troublesome below a depth of about 500 feet in 
this last locality. It is also found in most of the other wells of the 
southern area. The wells near the lagoon usually yield flowing 
water. 
The three following logs are characteristic of their respective 
localities. 
Log of well near the middle of the north line of sec. 28, T. 1 S., R. H W. (immediately 
southeast of the lagoon), Salt Lake field. 
[Elevation, 175 feet.] 
Alluvium and clay. ... 
“Dead” oil sand and water. 
Clayey shale; occasional layers of hard “shell” averaging 2 feet in thickness and 
in places confining small quantities of oil and gas beneath them. 
Good oil sand flowing 1 barrel per day. 
Clayey shale similar to that from 80 to 700 feet. 
Clayey shale, but no oil sand or signs of oil in it. 
Thick¬ 
ness. 
Depth. 
Feet. 
Feet. 
40 
40 
40 
80 
620 
700 
5 
705 
765 
1,470 
730 
2,200 
