ZO DELOS AND RALPH ARNOLD 
shales, much contorted, are exposed along the sea cliff from 
Point Fermin to Timm’s Point, and at Deadman Island, where 
they form the basement series. After the desposition of the 
Miocene shales the beds were elevated, contorted, and subjected 
to erosion. Following this a submergence took place during 
the Pliocene epoch, and a deposit of fine yellowish-brown, clayey 
sand was laid down on the surface of the eroded Miocene shales. 
The maximum thickness of this Pliocene at San Pedro is fifty 
feet; 
In post-Pliocene times this sandstone was elevated and sub- 
jected to erosion; the Deadman Island and Timm’s Point brown 
sands being all that is left of the Pliocene near San Pedro. 
A later submergence brought the surface of the Pliocene 
again below sea level and deposits of fine gray sand, fos- 
siliferous in places, were laid down on it. The maximum 
thickness of the gray sand formation at San Pedro is fifty feet. 
This gray sand formation rests unconformably on the Pliocene 
at Deadman Island, but is probably conformable with the Plio- 
cene at Timm’s Point. On account of its fauna, lithologic char- 
acteristics, and unconformable position on beds of late Pliocene 
age the gray sand formation, called the lower San Pedro series, 
is thought to be of Pleistocene origin. 
A period of uplift more or less pronounced followed the depo- 
sition of the lower San Pedro series. This uplift brought about 
conditions favorable to the formation of lagoonal, sand dune, 
and shore deposits. These deposits, which are called the upper 
San Pedro series, consist of coarse gravels and sands, which are 
characterized by the abundance of their fossil contents, by false 
bedding, and by indications of the changing conditions which 
prevailed during the period of their deposition. Evidence 
which indicates that the upper San Pedro series rests unconform- 
ably upon the subjacent formations is found at all the outcrops 
of this formation which have been examined by the writers. 
The upper San Pedro gravels and sands rest upon the Miocene 
shales at Crawfish George’s, on the Pliocene at Timm’s Point, 
and on the lower San Pedro series at Deadman Island and the 
