Los Angeles herald., 1910-09-25
nv w R HAMILTON


TN a region in which the geology is
so complicated as in California it
a has an important bearing upon
the core of the entire Coast range.
have been subjected to profound dis
turbances, and, unlike most OF the
eastern oil fields, the condition at one
locality is no criterion as to conditions
a few miles, or even few feet, away.
For this reason the oil operators are
coming to depend more and more upon
the geologist to explain the Vagaries
of the oil sands. The following notes
are written for the purpose Of giving
the ordinary reader an idea of one OF
the most important phases Of the IN
dustry, the occurrence of petroleum.
All rocks of the earth's crust are
generally classified by biologists into
three classes; First, massive, erup-
tive or intrusive, which includes those
like the GRANTEES which have s1ildl-
fled below the earth's crust, anu the
lavas which have been erupted IN
molten state; second, sedlnlthtary,
which embraces all classes which have
been formed by the breaking up OF
portions of the crust of the earth ana
the redeposition as sands, clayS, gray
els, limestones, etc. 1t also incIudeS
an important class of rocks Whlch are
formed by the accumulation of the
bodies of minute animals AID plants
metamorphic, or schistos5, which en-
braces a class of rocks which have
been formed by the alteration OF the
two former classes, and sont3 rocks of
which the origin is obscure.
The first and third classes make up
the greater portion of the Sierra Ne
vada of California and probably form
Paleozoic, secondary or Mesozolc,
They are of great Importance In some
of the other mineral industries of the
state, especially those of gold, silver,
copper and quicksilver. For petrole-
Um, however, they are of little inter-
est as no important deposits have
been found within them. Our discus
sion will therefore be confined TO the
sedimentary rocks.
ORIGIN OF SEDINIENTARIES
The sedimentary rocks may be sepa-
rated into several classes, according
to their origin and mode OF toposi-
tion. They are also classified accord
ing to the sequence in which they
We're deposited in the differcnt past
ages. The order of succession is as
follows, the Oldest first: Primary or
Paliozoic, secondary or McsoZolc,
Tertiary or Cenozoic, quartertiary or
post-tertiary. In the Appalachian re-
gion the oil occurs in the Paleozoic.
In Colorado it occurs an the Mesozolc.
Practically all the California OIL Is
produced from the leIlld y. li+Ou5h
there are minor deposits in the Ere-
taceous, which is at the top Of the
MesoZoic.
The tertiary is better represented in
California than in any other equal area
in North America. The total thickness
of tertiary sediments amounts to about
$4,000 feet, which indicates that some
profound disturbances have taken
place This thickness of sediments is
not all represented in one locality, nor
is any one formation continuous and
uubroken over as great distances as
we find some of the older formations
of the plateau region of Utah and Ari-
zona
The oldest formation of the tertiary
and the oldest which is of Importance
as a producer of oil is the Eocene. In
the Coalinga district it is composed
partly of white silicious shales, which
are made up of the microscoplcal
marine organisms called diatoms. 1t
is presumed that the organic matter OF
these plants contained the hydro
carbons which is now petroleum
Shales of this character are found IN
many places in the coast ranges, from
Mendocino to Orange, but are not con-
fined to any particular horizon. They