Download A PROFILE OF SOUTHERN CALIFORNIA GEOLOGY Richard H

© AAPG Pacific Section, 2007 - Metropolitan Oil Fields and their Environmental Impact, 1973
A PROFILE OF
SOUTHERN CALIFORNIA GEOLOGY
Richard H. Jahns
PREFACE
The Field Trip Committee of the Pacific Sections of the American Association of Petroleum Geologists, Society
of Economic Paleontologist and Mineralogists, and Society of Economic
Geophysicists bids welcome to all field
trip participants.
The new guidebooks cover a large
segment of the southern one-third of
the State and present both descriptive
and interpretive information on some
of the diverse and complex geology of
the region. In addition to such subjects
as the environmental aspects of metro-
politan oil field development and future
sources of geothermal power, a striking variety of geologic features and
scenic routes are included. Moreover,
at the suggestion of the Technical Program Committee, a number of papers
in the technical sessions and symposia
apply directly to specific facets of several field trips.
We wish to offer our heartfelt thanks
to the more than 50 individuals who organized, contributed to, and implemented the field trips. To those who
volunteered articles or services but
were turned down for lack of space or
time, our sincere apologies. We also
wish to express our gratitude to those
companies that provided manpower
and facilities in support of publication.
Furthermore, we extend our appreciation to the landowners and public
officials who permitted access and
visiting privileges.
The Field Trip Committee
Chairman - J. C. Vedder, USGS
Printing Chairman & Editor Doug Traxler
T
7
0
0
0
\\ \ ,,\~
|
//i
~D
//
I
,,,,;.j
~n
f
/ •
I
\
r j
,
I
I
I
I
s ~
o
,/
' ' ~ - m~
--7
/
I
!
7-
J
,4b
\
~.~.
0
A PROFILE OF SOUTHERN CALIFORNIA GEOLOGY
Richard H. Jahns
GENERAL RELATIONSHIPS
Southern California has been described in many contexts as a
land of variety and abundance.
This happy designation is quite appro-
priate when applied geologically,
as the region is one of numerous and
remarkably diverse rock types, mineral deposits,
geomorphic features.
structural elements,
and
The diversity reflects an unusually complex geologic
history whose latest chapter still is being written in terms of vigorous
diastrophism,
erosion, and sedimentation.
strong contrasts in present topography,
It also is responsible for
cl~m~te, vegetation,
and land
use from one part of the region to another.
Within an area of about 90,000 square miles in southern California
are several mountain ranges whose crests rise above the 10,000-foot contour,
at least fifty lesser ranges of major extent, precipitous canyons and
broad valleys at many levels, and two basins that in large part lie below
sea level.
Several bold, canyon-gashed
scarps rise 8,000 to i0,000 feet
within horizontal distances of only a few miles from their bases; in contrast are areas over which the maximum topographic relief is less than 500
feet for tens or even hundreds of square miles.
In terms of standard classifications,
the climatic types within
this region range from arid to humid and from hot to cold, the life zones
from lower Sonoran to alpine.
The Geolo$ic Section
For purposes of this broad description, southern California can
be most simply divided into a coastal belt, about 65 miles in average width,
and a much more extensive interior region.
In both these areal divisions
the geologic sections comprise igneous, sedimentary,
and metamorphic rocks
and a considerable variety of surficial deposits, and they range in age from
Precambrian to Holocene.
Throughout the coastal belt the rocks can be readily grouped into
two major sequences that are separated by a profound unconformity.
erate to very great differences
in lithology,
Mod-
structure, and degree of
metamorphism distinguish the rocks beneath this break from those that lie
above it.
The oldest rocks above the unconformity are marine strata of
Upper Cretaceous age, and in most areas the youngest rocks beneath it are
plutonic types dated as mid-Cretaceous
radiometric and stratigraphic means.
or earliest Upper Cretaceous by both
A similar two-fold division can be
made among the rocks exposed on the sea floor adjacent to the present coastline, and the great unconformity also is easily recognized over large areas
in western parts of the interior region.
The rocks of the older sequence are predominantly plutonic, metasedimentary,
and metavolcanic
types.
Many of these form parts of Precambrian
terranes that are widely exposed in the interior region but only in one
small part of the coastal belt.
Post-Precambrian
rocks also are abundant
in the interior, and are overwhelmingly preponderant within the older
sequences of the coastal belt, chiefly as batholithic masses of late Mesozoic
age and as remnants of earlier layered sections of both continental and
ocean affinities.
Within the interior region,
the intensity of deformation
and metamorphism in most of the layered rocks decreases toward the east,
where correlations have been established with the thick Mesozoic,
Paleozoic,
and youngest Precambrian sections of the Colorado Plateau province and
adjacent parts of the Great Basin.
The rocks of the younger sequence occur as marine and nor~arine
strata of Upper Cretaceous,
Tertiary,
and other volcanic accumulations
and Quaternary age, and as lava flows
of Tertiary and Quaternary age.
Dominant
in the coastal belt are elastic marine sedimentary rocks, most of which
were laid down in large basins over long periods of time and under a wide
range of environmental conditions.
Many of the sections are very thick,
and most are marked by rapid lateral variations and numerous unconformities.
The sedimentary rocks in the interior region are chiefly fluviatile and
lacustrine,
and were deposited mainly in smaller,
over much shorter periods of time.
essentially isolated basins
Volcanic rocks constitute a minor part of
the younger sequence in the coastal belt, but are widespread and very abundant
in the interior region,
Accumulations of oil and gas occur almost wholly within strata
of the younger sequence, and in areas that are within or adjacent to the
coastal belt.
In such areas the rocks of the older sequence, which under-
lie the Cenozoic basin sections or are exposed on adjacent ground that is
structurally high, are referred to collectively as "basement" by many
geologists.
Structure
The older structural features in most of the layered rocks that
lie beneath the great unconformity reflect two or more episodes of mild to
very severe deformation,
at least one of which commonly appears to have
been associated either with the emplacement of plutonic igneous rocks or
with the eastward thrusting of oceanic rocks beneath an ancient margin of
the North American continent.
Thespatial
folding, shearing, metamorphism,
and temporal pattern of faulting,
and igneous activity generally is complicated
or even masked by the effects of younger deformation,
and thus far has been
satisfactorily deciphered in only a few relatively small areas.
So complex
are most of the end products that their complete structural history remains
to be determined.
The younger structural features, which affect rocks that lie above
the great unconformity,
are perhaps the most fundamental elements in the
present framework of Southern California geology.
The extremely complex
history of the region during Cenozoic time is based upon a central theme of
repeated faulting, much of it on a grand scale and much of it evidently related to changesinconfiguration
faults
of adjacent oceanic crust.
have been primarily responsible for the definition,
Movements along
deepening,
shift-
ing, and more detailed modification of sedimentary basins, and for the uplift
of mountain masses from which enormous quantities of clastic materials have
been derived.
The Cenozoic rocks themselves have been dislocated and other-
wise disturbed, and so much of this diastrophic activity has persisted into
recent geologic times that most of the present physiographic
the region are intimately related to faulting.
features in
Folding and warping also
have disturbed many of the younger rocks to significant and even to very
important degrees, but in general their role in the broad structural framework has been subordinate to that of faulting.
The compilation in Figure i shows most of the known major faults
in a large part of southern California.
Nearly all of these have been
active during parts of Cenozoic time, and many can be confidently regarded
as active today.
The histories of some may date back into Mesozoic time,
and a few of those in the interior region are known to be still older.
Best represented among the principal elements of the fault pattern are nearvertical breaks whose major components of movement have been strike-slip
(e.g., San Andreas, San Gabriel, San Jacinto, Elsinore, Garlock), along
with gently- to steeply-dipping breaks whose major components of movement
have been dip-slip in a thrust or reverse sense (e.g., Sierra Madre,
Banning, Santa Ynez, White Wolf).
Normal faults with large displacements
are very rare in the coastal belt, but are prominent in parts of the interior region.
The structural evolution of southern California during Cenozoic
time not only is significant in a purely tectonic sense, but is fundamental
to the reconstruction of regional paleogeography and the histories of individual sedimentary basins.
A highly generalized paleogeographic map intended
to show relationships in late Oligocene time, for example, may be inaccurate
and even grossly misleading unless appropriate corrections can be made for
large post-Oligocene displacements along lateral faults that transect the
area.
This and many other problems demand a more complete resolution of
the nature, timing, and causes of fault movements in southern California.
The interplay of these movements has been very complex on both local and
regional scales, and determination of directions and amounts of net slip
along individual breaks in many instances is compounded by evidence of
reoriented movement.
The problem has been under vigorous attack via avenues
ranging from highly detailed mapping to piecing together the puzzles of
plate tectonics (see, e.g., Dickinson and Grantz, 1968).
GEOLOGIC INVESTIGATIONS
Systematic studies of southern California geology date from more
than a century ago, when the first reasonably accurate geologic maps (Blake,
1856; Antisell, 1857) appeared as outgrowths from early surveys for routes
of transportation.
Additional investigations were made in the fifties and
sixties under the aegis of the State, and from the time of its organization
in 1880 the State Mining Bureau was active in many areas.
A great deal
of early work also was done by members of the U.S. Geological Survey, which
was organized in 1879, and by teachers and students of the University of
California and Stanford University.
Attention was focused mainly on geo-
logic mapping, studies of mining districts, and on special stratigraphic,
structural, mineralogic and paleontologic problems.
Geologic knowledge was applied directly to the search for oil
and gas beginning at about the turn of the century, and within a few years
detailed studies of stratigraphy and structure led to discovery and development of new fields, as well as to improved understanding of fields that had
been found earlier on the basis of surface seepages.
The general trend of
investigations in petroleum geology is clearly shown in the published record,
as the earlier and largely descriptive sunm~aries (e.g., Goodyear, 1888;
Eldridge, 1903) were followed by a long series of detailed reports, mainly
by members of the U.S. Geological Survey, outlining the results of intensive
studies in specific areas and districts (e.g., Eldridge and Arnold, 1907;
Arnold and Anderson, 1910; Arnold and Johnson 1910; Pack, 1920; English,
1921, 1926; Kew, 1924; Hoots, 1931; Woodring et al., 1932, 1940).
The work
of these men, and of numerous oil-company geologists, members of university
staffs, and other investigators, provided a sound, basis for further interpretations of the shallow crust, as well as for the pursuit of many specific
lines of inquiry in large parts of the region.
Owing to the essential restriction of known accumulations of oil
and gas to the San Joaquin Valley area and to the coastal belt, these parts
of southern California have received much more detailed attention than the
bulk of the interior region.
This attention, moreover, has been focused
chiefly upon the rocks that postdate the great unconformity,
as it is within
them that nearly all the accumulations of commercial value have been found.
On the other hand, it should be emphasized that petroleum geology by no
means has stood alone in southern California,
as many other areas and geo-
logic features have been studied extensively in connection with projects
involving metalliferous
water resources,
deposits,
earthquakes,
occurrences of the industrial minerals,
and engineering
structures.
A host of ad-
ditional activities, many of a purely research nature, has added considerably
to the breadth of geologic coverage.
As investigations
creasingly diversified
of southern California geology have become in-
in their nature and aims, and as the investigators
themselves have represented a growing number of interests and affiliations,
attempts have been made to summarize the existing information,
instances,
to include broad interpretations.
considerable variations
in purpose,
and, in some
The published results show
coverage, and quality.
One early summary
(Hill, 1928), for example, represents an effort to place the problem of
earthquakes
in a new perspective for residents of the State, and its general
usefulness has been thereby limited.
Four decades ago, the Sixteenth Inter-
national Geological Congress stimulated the preparation of a guidebook
(Gale et al., 1932) that is brief but provides a more satisfactory
of southern California geology.
In many ways it has set the pace for the
larger and more elaborate guidebooks
1952; Jahns, 1954; Higgins,
sampling
that have appeared since (e.g., Laiming,
1958).
More complete summary coverage of the stratified rocks came soon
thereafter, with publication of a classic volume on the geology of the State
(Reed, 1933).
In this work, careful integration and interpretation of an
impressive wealth of data effectively brought some order out of chaos.
It
was the forerunner of a more specialized volume dealing with the structural
evolution of southern California
(Reed and Hollister,
oil and gas in the State was later summarized
1936).
The geology of
in a third massive work
(Jenkins et al., 1943), which remains today as a standard reference in its
field.
The geology of southern California was most recently and comprehensively
outlined in Bulletin 170 of the State Division of Mines (Jahns, 1954),
which includes the contributions of 103 authors representing many different
organizations.
This treatise provides general and detailed discussions of
both topics and areas, as well as several geologic guides and numerous maps,
and it is the source of much information quoted in later publications.
A modern geologic map of California was prepared by the State
Division of Mines 35 years ago (Jenkins, 1938), and a completely new edition
was recently completed on a larger scale and in much greater detail.
It
comprises sections that have been issued separately, and some of these
already have been revised on the basis of newly available information.
Com-
prehensive reports on minerals (Murdoch and Webb, 1956), geomorphic features
(Hinds, 1952), mineral deposits (Jenkins et al., 1950; Wright et al., 1957),
and engineering geology (Lung and Proctor, 1966) are among the other contributions to the summary record for recent decades.
THE GEOLOGIC PROVINCES
Southern California is readily divisible into eight natural provinces, in large part on the basis of distinctive physiographic characteristics
but more fundamentally on the basis of geologic history since mid-Mesozoic
time.
The distribution, areal dimensions, and major topographic elements of
these provinces are indicated in Figure 2, and a comparison with Figure 1
will show the relationships between these features and the pattern of
major faults.
Sierra Nevada
The southern part of the Sierra Nevada proper is fundamentally a
huge asymmetric, westward-tilted block that is bounded on the east by a
zone of high-angle faulting and disappears to the west beneath the thick
sedimentary fill of the San Joaquin Valley.
This block consists-mainly of
plutonic rocks that represent the composite Sierra Nevada batholith of late
Mesozoic age, together with older metamorphic rocks that are subordinate
but widely distributed.
Resting upon these crystalline rocks are scattered
patches of lower Tertiary fluviatile sediments, Tertiary and Quaternary
volcanic rocks,~and Quaternary glacial and post-glacial deposits.
The Tehachapi Mountains,
at the south end of the province,
consist
chiefly of the same kinds of pre-Cenozoic rocks, but appear to have a much
more complex internal structure.
This range trends northeast rather than
north, and it is bounded on both sides by major fault zones.
Within it
are large masses of Tertiary noumarine strata and associated volcanic rocks,
and along its margins are moderately
rocks.
to steeply tilted sections of Tertiary
Both the Tehachapi Mountains and the Sierra Nevada appear to have
been affected by several episodes of uplift during Cenozoic time, and the
most recent and possibly greatest of these took place during Pleistocene
time.
Basin-Range Province
The part of the Basin-Range province that lies in southern California is characterized by north-trending
basins, and an interior drainage.
ranges,
Pre-Cenozoic
intervening valleys and
rocks are exposed in most
of the ranges, and include a wide variety of sedimentary,
plutonic types.
volcanic,
Many have been mildly to intensely metamorphosed.
and
This older
sequence is the only one in southern California that contains carbonate rocks
in great abundance.
The Cenozoic rocks are more patchy in terms of both
initial and present distribution.
They are nonmarine,
and occur mainly as
volcanic accumulations,
coarse-grained
basin fill, and as deposits formed
in numerous short-lived
lakes of Tertiary and Quaternary age.
Taken together,
the older and younger sequences in this region represent the extreme age
range known within the State.
Many of the mountain ranges are essentially fault blocks, and some
of the valleys are fault-bounded
nor the history of deformation
troughs, but neither the structural pattern
in the region is at all simple.
The province
is in part bounded on the south by the Garlock fault zone (Pig. i), along
which there has been much left-lateral movement,
and it is bounded on the west
by the Sierra Nevada fault zone, along which dip-slip components of movement
probably have been dominant.
Within the province are many other high-angle
faults, as well as flat to moderately-dipping
thrust faults.
Widespread
faulting and warping of Quaternary age is reflected by many features of the
present topography.
Mojav e Desert
The Mojave Desert region, most extensive of the geologic provinces,
is in large part a gigantic fault-bounded wedge that points westward.
consists dominantly of pre-Cenozoic
and metamorphic
widespread.
It
rocks, among which Precambrian igneous
rocks and Mesozoic plutonic and volcanic rocks are most
This very complex section resembles that in the Basin-Range
province to the north, except that stratified rocks are much less abundant.
The Cenozoic section comprises volcanic and hypabyssal
intrusive rocks,
along with fluviatile and lacustrine sediments reflecting a complex history
of basin formation that began in middle Miocene time and has continued to the
present.
Much of the province lies between the left-lateral Garlock fault
on the north and the right-lateral San Andreas fault on the southwest
(Fig. i).
Within it are north- to northeast-trending
folds, steeply-dipping
faults, and some major thrusts of Mesozoic age, as well as more open folds,
low-angle normal and thrust faults, and steeply-dipping
age.
faults of Cenozoic
Many of the high-angle faults trend northwest and show evidence of
Quaternary movement
that can be correlated with the San Andreas stress-
strain system.
Colorado Desert
The Colorado Desert is an elongate,
low-lying depression whose
alluviated floor is in part occupied by the Salton Sea.
It is separated
from the Gulf of California by the delta of the Colorado River.
This de-
pression marks the general site of a former basin of middle and late Cenozoic
sedimentation,
and a thick section of fine- to very coarse-grained,
nonmarine strata,
ginal parts.
together with some volcanic rocks,
dominantly
is exposed in its mar-
The sedimentary sequence consists mainly of alluvial-fan and
lacustrine deposits, but also included are marine beds that were laid down
in a shallow, northward-extending
Pliocene time.
arm of the Gulf of California during early
Considerable exploration for oil and gas has been directed
toward this section,
thus far without notable success, but the Salton basin
appears to hold considerable promise as a source of geothermal energy.
The basin fill rests upon igneous and metamorphic rocks of preCenozoic age in some areas, and is in fault contact with them in others.
The northeast side of the province is traversed longitudinally by several
subparallel breaks of the San Andreas fault zone, and its highly irregular
western margin is in part outlined by several major fault zones that trend
northwest.
Many of these faults cut and offset rocks that are as young as
Quaternary.
The recent history of the basin, which has been associated with
opening of the Gulf of California along the East Pacific rise during the
past 5 million years, has involved subsidence,
local volcanic activity,
folding and intermittent movements along faults in both the marginal and
interior areas, and occupation by at least one large fresh-water
lake during
late Quaternary time.
San Joaquin Valley
The San Joaquin Valley, or southern part of the Great Valley of
California,
is one of the two most important areas in the State from the
standpoint of petroleum production and reserves.
Now an ~Tmense, nearly
flat-floored plain that is largely covered by alluvium,
this structurally
low region has been an elongate basin of deposition since mid-Cretaceous
time.
Beneath the valley floor is a remarkably thick and varied section of dominantly
clastic sedimentary rocks.
More than 25,000 feet of Upper Cretaceous marine
strata rests upon a heterogenous basement terrane, and in turn is overlain
by a considerably thicker sequence of younger formations that include both
marine and nonmarine strata as well as some volcanic rocks.
The broad trough of sedimentary deposits is asymmetric, with a
relatively steep westerly flank and a gently inclined easterly flank that
lies upon the western part of the Sierra Nevada fault block.
During much of
Tertiary time this basin was occupied by an inland sea, and a variety of
lithologic facies accumulated contemporaneously
subside.
as its floor continued to
Several episodes of uplift and depression are attested by uncon-
formities and by lithologic contrasts within the sedimentary section, and
many open folds, developed chiefly in mid-Pleistocene
both the marginal and interior parts of the basin.
time, are present in
Several prominent lines
of folding project southeastward and east-southeastward
10
into the basin from
its western margin, and relatively severe deformation in the southern end
and along the western side of the valley is expressed by numerous thrust
faults and overturned sections of stratified rocks.
Southern Coast Ranges
The southern part of the Coast Ranges province is characterized
by a distinct topographic and structural grain that trends northwest to
north-northwest.
A thick section of Upper Cretaceous and Cenozoic sedi-
mentary rocks, mainly marine and mainly clastic, is exposed over most of the
area.
Some of these strata contain important accumulations of oil and gas,
principally in the Santa Maria and Cuyama basins.
An older and in part highly disordered assemblage of rocks lies
unconformably beneath the Cenozoic strata, and in places is juxtaposed
against them along faults.
It comprises felsic plutonic rocks and mildly
metamorphosed but intricately deformed rocks of the Mesozoic Franciscan complex, which includes clastic sedimentary rock types, chert, limestone,
various schists, basalt, diabase, and
serpentinite of oceanic affinities.
The province is sliced almost longitudinally by two major fault
zones, the San Andreas on the northeast and the Nacimiento on the southwest
(Fig. i), as well as by many other subparallel breaks with northwesterly
trend.
The Nacimiento zone appears to express a profound break, probably an
ancient zone of subduction along which Franciscan rocks are now in contact
with continental granitic rocks to the northeast.
are late Mesozoic in age, form
The plutonic rocks, which
the core of a crustal block that appears to
have been a highland mass during much of Tertiary time, while sediments were
being deposited in the flanking areas.
middle Miocene,
Cenozoic deformation,
late Pliocene, and mid-Pleistocene
numerous folds, faults, and unconformities
especially in
times, is reflected by
in the sedimentary section.
Transverse Ranges Province
Trending essentially eastward across the regional grain of southern
California is the Transverse Ranges province, which comprises elongate mountain
ranges and valleys,
chains of hills, and broad basins that are geologically
11
very complex.
Its eastern half, which is prevailingly mountainous,
composed for the most part of plutonic, metasedimentary,
rocks that pre-date the great unconformity.
is
and metavolcanic
Tertiary sedimentary rocks,
both marine and nor~arine, are preserved locally.
The western half of the province is featured by diverse sections
of Tertiary and
Quaternary
sedimentary rocks, in places enormously thick,
that were deposited in several large basins.
These and associated volcanic
rocks rest upon and against older sedimentary rocks, as well as still older
crystalline rocks that are in part correlative with those exposed in areas
farther east.
The basins of Cenozoic deposition did not, in general, corres-
pond to the outlines of the present lowland areas, so that many of the basin
sections are now exposed in relatively mountainous
country.
Of great importance as a source of petroleum is the Ventura basin,
which extends over a large area now drained mainly by the Santa Clara River
north of Los Angeles
(Fig. 2).
of the ocean west of Ventura.
Tertiary, and
60,000 feet.
common.
Quaternary
Much of it also lies beneath the shallow waters
The basin fill includes Upper Cretaceous,
strata whose maximum aggregate thickness is nearly
Rapid lateral variations
in lithology and thickness are very
In one central part of the basin, for example,
is 15,000 feet of
elastic Pliocene strata, whereas only 4 miles to the south the Pliocene
section is less than 2,000 feet thick.
The sedimentary rocks have been deformed into a broad synclinorium
that is complicated by numerous intra-basin folds and faults.
The largest
individual features are deep fan synclines with both limbs overturned;
limbs are broken by outward-dipping
inward and upward movements
the
thrusts and reverse faults that represent
toward the axial regions of the folds.
The his-
tory of the entire basin, especially during middle and late Cenozoic time,
appears to have involved a highly complex interplay of broad and local subsidence, folding, and faulting, accompanied by deposition of predominantly
elastic sediments in local sub-basins at some times and over much larger areas
at others.
Almost the entire section is cut off at the east by the San
Gabriel fault, and most of its stratigraphic units cannot be correlated with
temporally equivalent units in contiguous basins on the other side of this
major break.
12
The province as a whole resembles the adjoining Coast Ranges and
Peninsular Ranges provinces in several respects, but is distinguished from
them by its east-west structural trends.
Elongate, generally steep-sided
folds, many of them ruptured along their axes or on one or both flanks by
gently- to steeply-dipping compressional faults, are characteristic of the
present basinal areas and those western ranges that consist mainly of sedimentary rocks.
The other ranges are best regarded as great up-thrown
blocks, bounded mainly by faults that dip gently to very steeply, that have
had both thrust and left-lateral components of movement, and that appear to
converge downward beneath the blocks.
The San Gabriel Mountains (Fig. 3)
represent a very complex block that is structurally high, and within this
range are the only rocks in the coastal belt of southern California that
definitely have been dated as Precambrian.
The entire province appears to
have been under severe north-south compression during late Cenozoic time.
Several episodes of intense deformation, including a late Mesozoic
orogeny and accompanying widespread plutonic intrusion, are recorded by the
older rocks of the province.
The Cenozoic section contains unconformities,
some of them extensive, that reflect a variety of disturbances in both basin
and source areas.
A great mid-Pleistocene orogeny produced intense folding
and uplift, and was responsible for development of the major elements of
the present topography.
The great San Andreas-San Jacintofault zone slices
across the eastern part of the province at an acute angle, and the San Gabriel
fault zone is somewhat similarly disposed farther west (Fig. I).
Marine
terraces of Pleistocene age are prominent features of the coastal landscape,
and lie at elevations of as much as 1,200 feet above present sea level.
Some
of them have been warped and broken by faults.
Peninsular Ranges Proyince
The Peninsular Ranges province is characterized by a northwesttrending topographic and structural grain that butts abruptly against the
Transverse Ranges grain in the general latitude of Los Angeles.
The inland
parts of the province include several high mountain ranges, and are underlain
chiefly by plutonic, metasedimentary, and metavolcanic rocks of Paleozoic
13
and Mesozoic age.
The igneous rocks include widespread representatives
the great composite Southern California batholith.
of
Patches of younger vol-
canic rocks and nonmarine sediments of middle and late Cenozoic age are
present locally.
A coastal plain of irregular outline is marked by numerous marine
terraces.
It is underlain by dominantly clastic marine and nonmarine strata
of Upper Cretaceous,
Tertiary,
and Quaternary age, and by scattered volcanic
rocks of Tertiary and Quaternary age.
This section thickens to more than
30,000 feet in the Los Angeles basin at the northwestern end of the province,
where it evidently accumulated in a subsiding area under widely varying
conditions of sedimentation.
In many respects this basin resembles other
Cenozoic basins in the adjoining Transverse Ranges province, but its major
structural features have the typical Peninsular Ranges trend.
The Los Angeles basin has yielded nearly one-half of all the
petroleum thus far produced in the State. The present topographic basin is
a coastal lowland area, nearly 1,000 square miles in extent, whose floor is
marked by elongate low ridges and groups of hills
(Figs.
4, 5).
Both this
and some adjoining areas were covered at various times in the past by marine
waters, and received sediments in much the same manner as the Ventura basin
to the northwest.
Shifts in the rate of subsidence,
structural adjustments
along the margins and floor of the basin, and major elevations of nearby
source areas were largely responsible for changes in the shape and extent of
the marine embayment,
repeated changes in the nature and rate of sedimentation,
and for the development of many unconformities
in marginal parts of the basin.
During middle and late Miocene time the embayment was very large
and was connected with the waters of the Ventura basin.
ment was somewhat smaller,
The Pliocene embay-
though at first very deep in the central part of
the basin a few miles southeast of the present Los Angeles Civic Center.
During Pliocene and Pleistocene times the depression was gradually filled with
sediments, until much of its surface finally lay above sea level.
The post-
lower Miocene strata reached a maximum thickness of more than 20,000 feet.
14
The basin area is transversed by subparallel zones of deformation
that trend northwest to west-northwest.
One of these, the Newport-lnglewood,
can be likened to the Nacimiento fault zone of the Coast Ranges to the
northwest (Fig. 1), in that it expresses a major boundary between basement
rocks of oceanic and continental origins.
The buried crystalline rocks of
the basln floor are divided by faults into large blocks that lie at contrasting levels, and these irregularities are reflected in various degrees
by undulations and folds in the overlying sedimentary section.
Most of the
known and inferred faults extend upward into the basin fill, commonly with
decreasing amounts of displacement at successivley higher levels.
out upward into zones of folding and warping.
Some die
Especially prominent on the
present surface of the basin are two northwest-trending lines of anticlinal
uplift along which enormous quantities of petroleum have been concentrated
(Fig. 6).
Most of the folds are open, but their flanks are complicated by
unconformities, faults, and small-scale wrinkling.
Many of the anticlines
are known to contain deformed cores of basement rocks at depth.
The folding
affects strata as young as latest Pleistocene, and in large part is plainly
reflected by the present topography (Figs. 4-6).
The entire Peninsular Ranges province can be regarded as an uplifted and westward-tilted mass that has been broken into several elongate
blocks by major faults that trend northwest.
Most of these faults have been
intermittently active during large parts of Cenozoic time, and adjacent fault
blocks commonly have had distinctly different histories.
The continental
borderland, offshore from the Los Angeles basin and the higher ground to the
southeast, is distinguished by prominent, steepsided ridges that appear to
be horst-like in structure, and by intervening depressions that in general
have the form of closed basins.
The ridges are composed mainly of foliated
rocks that resemble the Franciscan section of the Coast Ranges to the northwest, and in places are covered with sedimentary and volcanic rocks of Tertiary
age.
Younger sediment also veneers the ridges and forms considerable thick-
nesses of fill in the basins.
15
OIL AND GAS
Historical Sketch
Commercial production of petroleum from occurrences in southern
California dates from 1866, when a shallow well was completed in the northcentral part of the Ventura basin.
Initial development of the Pico Canyon
area, at the eastern end of the same basin, began a decade later and was
followed by successful drilling along the northern margin of the Los Angeles
basin.
Important discoveries subsequently were made along the eastern and
western borders of the San Joaquin Valley and in the Santa Maria basin of
the Coast Ranges province.
All the early production resulted from drilling
in areas where surface seepages had been recognized.
Beginning shortly after 1900, studies of surface geology were
applied to the extension of existing oil fields and to the search for new ones.
The last significant discovery attributable solely to drilling near seepages was made in 1904.
Exploration of areas on the basis of structure
recognizable from surface exposures led to development of most of the State's
major fields during the following three decades.
Production rates increased
from an average of about 12,000 barrels per day in 1900 to more than 90,000
barrels per day in 1905 and 270,000 barrels per day in 1914.
During each
year from 1923 to 1930 the average daily production was well over 600,000
barrels, and in 1929 it reached a high of approximately 800,000 barrels.
Although many of the earlier structural interpretations represented
the integration of surface observations with data obtained from wells, it
was not until the mid-thirties
upon subsurface investigations.
that significant new emphases were placed
The seismograph proved to be a valuable tool,
and within a period of only a few years it led to discovery of the prolific
Wilmington field in the Los Angeles basin and several important fields in
the San Joaquin basin.
Another new approach
now commonly referred to as
stratigraphic, facies, or environmental analysis, was largely responsible
for additional discoveries, especially in the San Joaquin basin.
This method,
involving consideration of all available surface and subsurface data on
lithology, paleontology, and structure, is aimed at the reconstruction of
16
tectonic and sedimentary environments in order to establish targets for
drilling.
Its effectiveness in southern California has not been confined to
the search for traps of a purely stratigraphic nature, and it played a major
role, for example, in the discovery of the important structural-trap
occurrences in the Cuyama Valley district of the Coast Ranges province.
To date the total production of petroleum in California has amounted
to approximately 15 billion barrels, a substantial fraction of the nation's
total.
This output represents the contributions
from more than 65,000 wells
in nearly 300 oll fields,most of which lie in the southern part of the State.
Some pertinent production comparisons can be drawn from the following
tabulation, which is based on data from the California Division of Oil and
Gas.
Petroleum Productions Bbl x 106
Field
Geologic Province
Net 1971
Cumulative
Wilmington
Peninsular Ranges
73
1480
Midway-Sunset
San Joaquin Valley
34
1123
Kern River
San Joaquin Valley
26
549
Huntington Beach
Peninsular Ranges
16
863
Ventura
Transverse Ranges
i0
750
San Ardo
Coast Ranges
10
238
Belridge, South
San Joaquin Valley
9
171
McKittrick
San Joaquin Valley
9
184
State of California
327
17
~
15,000
Nearly 24 trillion cubic feet of natural gas has been produced
in the State to the present time.
By 1958 about four-fifths of this total
had come from oil fields, with the remainder obtained from dry-gas fields,
most of which are in the northern San Joaquin Valley and the Sacramento
Valley.
Since that year the relative production of dry gas has steadily
increased,
and in 1971 it exceeded that from oil zones for the first time.
Oil, gas, natural gasoline, and condensate together have contributed heavily
to the total value of California's mineral output; when the annual value of
this output first topped the billion-dollar
level in 1948, more than three-
quarters of it came from petroleum and allied fuels.
Occurrence
Most of the oil and gas in California occurs in the southern half
of the San Joaquin Valley,
Coast Ranges province,
the southwestern and
southeastern corners of the
the western half of the Transverse Ranges province.
The most productive areas-are the San Joaquin basin and the Los Angeles basin,
each of which has accounted for roughly 45 percent of the State's total
output.
Much of the remainder has come from the Ventura basin.
Strata of Miocene and Pliocene age have yielded nearly four-fifths
of the oil thus far obtained, and they constitute the dominant reservoir
rocks within every producing district.
In addition,, significant amounts of
oil have been extracted from Eocene and Oligocene strata in the Ventura basin,
from Cretaceous~
Eocene, Oligocene,
and Pleistocene
strata in the San Joaquin
basin, and from fractured basement rocks in several fields, mainly in the
Los Angeles basin.
Sandstone is the most widespread and abundant reservoir
rock, and has yielded about 98 percent of the total production.
der has been obtained from conglomerates
occupies fractures,
The remain-
and from rocks in which the oil
chiefly in shales, cherty or otherwise siliceous shales,
schists, and igneous rocks.
Carbonate rocks are extremely
sections of the oil fields, and no significant
rare in the Cenozoic
limestone or dolomite reser-
voirs are known.
The concentrations
of oil and gas plainly are attributable to a
variety of controls, and many attempts have been made to classify the known
18
pools according to the type of trap involved.
The situation is complicated
by the widespread occurrence of more than one accumulation factor for
individual pools, by contrasting controls from one pool to another within
the same field, and by intrinsic difficulties in establishing a workable
classification of traps.
Only a few generalizations need be offered here.
About 85 percent of the known accumulations are associated with
folds, which include
domes and elongate anticlines with double closure,
anticlines and other folds in which closure is effected by one or more
faults or sets of faults, and folds in which truncations,
pinch-outs,
or
other lithologic factors are at least partly responsible for the trapping.
More than one-half of the accumulations are associated with faults, some of
which probably influenced localization of the oil and some of which probably
or certainly did not.
Also common are stratigraphic
traps, most of them
ascribable to depositional or erosional discontinuities,
meability barriers,
to more subtle per-
or to tar seals at or near the surface.
Anticlines and faulted anticlines,
some with stratigraphic
traps
on their flanks, are most characteristic of the Los Angeles and Ventura basins.
Most accumulations
stratigraphic.
category.
in the Santa Maria basin are anticlinal,
and several are
Those in the Cuyama basin belong in the faulted-anticline
All three types are well represented in the San Joaquin basin,
where at least half of the pools are attributable to two or more major factors
acting in combination.
Neither salt-dome nor volcanic-plug
traps are known
in southern California.
An outstanding
feature of many southern California oil fields is
their high productivity per unit of surface area.
The average recovery for
all fields to 1958 was more than 30,000 barrels per acre, and that for fields
in the Los Angeles basin about I00,000 barrels per acre.
The Long Beach field
(Fig. 6) has yielded oil in the astonishing amount of more than 500,000 barrels
per surface acre.
The principal explanation for these high recovery ratios
lies in the occurrence of several producing horizons,
many fields.
one above another,
The "sands" in general are well saturated,
in
and their aggregate
thicknesses commonly are measured in hundreds or even thousands of feet.
The recovery data are not nearly so impressive, however, when they are equated
19
against both surface areas of the fields and thicknesses of the producing
zones.
More detailed treatment of numerous areas and oil fields in
southern California is provided elsewhere in this volume, and much additional
information of value is available in the earlier published record (e.g.,
Jenkins et al., 1943; Laiming, 1952; Oakeshott et al., 1952; Jahns, 1954).
20
REFERENCES
Antisell, Thomas, 1857, Geological report in Report of Lieutenant John G. Parke,
Corps of Topographical Engineers, upon the routes in California to
connect with the routesnear the thirty-fifth and thirty-second
parallels: Reports of explorations and surveys to ascertain the
most practicable and economical route for a railraod from the
Mississippi River to the Pacific Ocean, 33rd Cong., 2nd sess.,
Senate Ex. Doc. No. 78, vol. 7, 204 p.
Arnold, Ralph, and Anderson, Robert, 1910, Geology and oil resources of the
Coalinga district, California: U.S. Geol. Survey, Bull. 398, 354 p.
Arnold, Ralph, and Johnson, H.R., 1910, Preliminary report on the McKittrickSunset oil region, Kern and San Luis Obispo Counties, California:
U.S. Geol. Survey, Bull. 406, 225 p.
Blake, W.P., 1856, Geological report in Report of Lieutenant R.S. Williamson,
Corps of Topographical Engineers, upon the routes in California
to connect with the routes near the thirty-fifth and thirty-second
parallels: Reports of explorations and surveys to ascertain the
most practicable and economical route for a railroad from the
Mississippi River to the Pacific Ocean, 33rd Cong., 2nd sess.,
Senate Ex. Doc. No. 78, vol. 5, 310 p.
Dickinson, W.R., and Grantz, Arthur (editors), 1968, Proceedings of Conference
on Geologic Problems of San Andreas Fault System: Stanford Univ.
Pubis. Geol. Scis., vol. II, 374 p.
Eldridge, G.H., 1903, The petroleum fields of California:
Bull. 213, p. 306-321.
U.S. Geol. Survey,
Eldridge, G.H., and Arnold, Ralph, 1907, The Santa Clara Valley, Puente
Hills, and Los Angeles oil districts, southern California: U.S. Geol.
Survey, Bull. 309, 266 p.
English, W.A., 1921, Geology and petroleum resources of northwestern Kern
County, California: U.S. Geol. Survey, Bull. 721, 48 p.
English, W.A., 1926, Geology and oil resources of the Puente Hills region,
southern California: U.S. Geol. Survey, Bull. 768, ii0 p.
Gale, H.S., and others, 1932, Southern California, Sixteenth Internat.
Geol. Congress, Guidebook 15, 68 p.
Goodyear, W.A., 1888, Petroleum, asphaltum, and natural gas in California:
California Min. Bur., Rept. 7, 117-178.
Higgins, J.W. (editor), 1958, A guide to the geology and oil fields of the
Los Angeles and Ventura regions, 204p., Amer. Assoc. Petrol. Geol.,
Pacific Sect., Los Angeles, California.
Hill, R.T., 1928, Southern California geology and Los Angeles earthquakes,
232 p., Southern California Acad. Sciences, Los Angeles.
21
Hinds, N.E.A., 1952, Evolution of the California landscape:
Mines, Bull. 158, 240 p.
California Div.
Hoots, H.W., 1931, Geology of the eastern part of the Santa Monica Mountains,
Los Angeles County, California: U.S. Geol. Survey, Prof. Paper
165-C, p. 83-134.
Jahns, R.H. (editor), 1954, Geology of southern California: California
Div. Mines, Bull. 170, i0 chapters, 34 map sheets, 5 geol. guides.
Jenkins, O.P., 1938, Geologic map of California, first edition, California
Div. Mines.
Jenkins, O.P., and others, 1943, Geologic formations and economic development of the oil and gas fields of California: California Div. Mines,
Bull. 118, 773 p.
Jenkins, O.P., and Staff, California Div. Mines, i950, Mineral commodities
of California: California Div. Mines, Bull. 156, 443 p.
Kew, W.S.W., 1924, Geology and oil resources of a part of Los Angeles and
Ventura Counties, California: U.S. Geol. Survey, Bull. 753, 202 p.
Laiming, Boris (editor), 1952, Guidebook: field trip routes, oil fields,
geology, 290 p., Amer. Assoc. Petrol. Geol. -- Soc. Econ. Paleont. Mineral.-Soc. Explor. Geoph., Joint Ann. Meeting, Los Angeles, California.
Lung, Richard, and Proctor, Richard (editors), 1966, Engineering geology
in southern California, 389 p., Special Publ. of Assoc. Engineering
Geol., Los Angeles Sect., Glendale, California
Murdoch, Joseph, and Webb, R.W., 1956, Minerals of California:
Div. Mines, Bull. 173, 452 p.
California
Oakeshott, G.B., Braun, L.T., Jennings, C.W., and Wells, Ruth, 1952, Exploratory
wells drilled outside of oil and gas fields in California to December 31,
1950: California Div. Mines, Special Report 23, 77 p.
Pack, R.W., 1920, The Sunset-Midway oil field, California, Part I. Geology
and oil resources: U.S. Geol. Survey, Prof. Paper 116, 179 p.
Reed, R.D., 1933, Geology of California, 355 p., Amer. Assoc. Petrol. Geol.,
Tulsa, Oklahoma.
Reed, R.D., and Hollister, J.S., 1936, Structural evolution of southern
California, 157 p., Amer. Assoc. Petrol. Geol., Tulsa, Oklahoma.
Woodring, W.P., Roundy, P.V., and Farnsworth, H.R., 1932, Geology and oil
resources of the Elk Hills, California, including Naval Petroleum
Reserve No. i: U.S. Geol. Survey, Bull. 835, 82 p.
Woodring, W.P., Stewart, Ralph, and Richards, R.W., 1940, Geology of the
Kettleman Hills oil field, California; stratigraphy, paleontology, and
structure: U.S. Geol. Survey, Prof. Paper 195, 170 p.
Wright, L.A. (editor), 1957, Mineral commodities of California:
Div. Mines, Bull. 176, 736 p.
22
California
"\
:! J'
..i#
' ";:
'1
.,~cf
,
.,
-Z
,,,
, ..(.,...:
,.
B
"~¢ - T "" -
O
'~.~.
"-
I. ,.~
~-'~
,
I. ~
.,f..
|
"
:,
:' ~
:..~.
,.
~
I-,~"
.
.
.
",~ '~ X-..-'~-
.~:>
:.
~,
L:,.
~,
.
"'~
2
,l.- ..
v~.. :..,
..
O
.,t~." ~
I_.'"
~;~I
.
•
"
,
~
~
.!~y-~-~.... . ~,~:
o-~
""--- .... ~I~
.
,
"
'.~
~
~
...~
.
.
'
i ~
"~,__~
..
.
. ~
~,
.
,
:,;,
Y
.
~
\~.
'
""
~:.':
'
, /
.,>
aC
.
"
\A
'\
!
Y
|~
,., /
~.
~
",.
.
"~.
.,
..{
:,
%
)., ,: ,.- .,~_.~.- ~
#_'" ~+'-
' ~:.,.....
~...
-
.~,
Ii
Oh"
23
aC
FIGURE 3. The San ]acinto fault zone, looking southeastward toward the Santa Rosa Mountains. Streams are
offset along the main break in central part of view, and a sag area appears in center foreground. Hemet Valley
at left and the broad Anza surface at right contrast markedly in altitude. Photograph by J. S. Shelton and R.C.
Frampton.
24
FIGURE 4. Southeastward view across parts of the San Gabriel Valley and the surface of the Los Angeles basin
toward Santiago Peak in the Santa Ana Mountains. The San Jose and Chino Hills, appearing as low, dark ridges
in middle distance, are underlain by Tertiary sedimentary rocks and represent structural uplifts within the basin.
The atmosphere is clouded at tow levels by haze and smoke rather than smog, as this photograph was taken from
the San Gabriel Mountains in 1905.
Photograph courtesy of William C. Miller.
FIGURE 5. Nightime view southwestward across a part of the surface of the Los Angeles basin from Mt. Wilson
in the San Gabriel Mountains, 1950. Several elongate structural highs that trend northwestward appear as dark
areas extending across the lowland surface. The Repetto Hills, parts of the Newport-Inglewood uplift, the Palos
Verdes Hills, and Catalina Island can be s e e n at successively greater distances in left-hand part of view, and
the Baldwin Hills, which mark a more northwesterly part of the New~ort-Inglewood uplift, are in right-center
distance.
Photograph courtesy of William ~. Miller.
25
0
~
~
~0 0
"~
~ ~,.. c,..~.
~
~ ".,.~
-~2 ~
26
0~