GEOLOGY AND PALEONTOLOGY OF PALOS - Pubs Warehouse

GEOLOGY AND PALEONTOLOGY OF PALOS VERDES HILLS, CALIFORNIA
As part of this program a report J was issued on the
geology of the east end of the Santa Monica Mountains,
the adjoining hills in the city of Los Angeles, and the
Puente Hills all along the north border of the Los
Angeles Basin. (See fig. 1.) At the time when this
program was started development of the oil fields was
carried on by small companies, generally with the
advice of practical oil prospectors. The intervening
years have witnessed the rapid growth of the oil industry
and the development of modern oil geology. As oil
development progressed in the Los Angeles Basin the
geology of the basin and its borders was studied inten­
sively by many geologists. Inasmuch, however, as the
results of the work of commercial geologists are not
available for general use, it appeared desirable .for the
Geological Survey to continue the investigations begun
in this area by Eldridge and Arnold. In 1926 a report 2
was issued on the Puente Hills and adjoining parts of
the Sarita Ana Mountains, and in a later publication 3
the geology of the eastern part of the Santa Monica
Mountains was described.
The present report on the geology of the Palos Verdes
Hills is part of the series of publications dealing with
the geology of areas within and bordering the Los Ange­
les Basin. It describes the geology, paleontology, and
mineral resources of the Palos Verdes Hills. The
strata that crop out in the hills are penetrated in oil
fields in the southern part of the Los Angeles Basin.
Special emphasis is devoted to data that may aid in
studying the subsurface section in the basin.
The illustrations of fossils from the different forma­
tions may be useful to both field geologists and labo­
ratory paleontologists. According to the experience of
California geologists, the illustrations of fossils in
early reports of the Geological Survey on California
oil fields are as useful now as at the time when the
reports were issued, despite changes in paleontologic
and stratigraphic nomenclature.
The Palos Verdes Hills include the San Pedro district,
which has become a classic region in California geology
as a result of Arnold's monograph 4 on the Pleistocene
paleontology. About 150 collections of Pleistocene
mollusks were made during the field work on which
the present report is based. It was planned to identify
a sufficient number of these collections to show the
facies and geographic differentiation of the fossils in
the different Pleistocene stratigraphic units. This
plan was abandoned, however, for the identification,
of about 500 species of mollusks would have involved
much work, and such a laborious undertaking would
have delayed unduly completion of the report. Se­
lected species were identified to serve as a basis for a
discussion of the faunas. The omission, of long lists of
Pleistocene mollusks is not a great loss, as Arnold's
collections were exhaustive and other paleontologists
have contributed to the Pleistocene paleontology of
the San Pedro district since the publication of Arnold's
monograph. Arnold's collecting was limited, how­
ever, to a small area along the water front. One
lithologic and faunal unit (Lomita marl) is not repre-
1 Eldridge, G. H., and Arnold, Ralph, The Santa Clara Valley, Puente Hills and
Los Angeles oil districts, southern California: U. S. Geol. Survey Bull. 309, pp. 102-198,
pis. 10-24, figs. 12-17. 1907.
2 English, W. A., Geology and oil resources of the Puente Hills region, southern
California: U. S. Geol. Survey Bull. 768,110 pp., 14 pis., 3 figs., 1926.
s Hoots, H. W., Geology of the eastern part of the Santa Monica Mountains, Los
Angeles County, Calif.: U. S. Geol. Survey Prof. Paper 165, pp. 83-134, pis. 16-34,
figs. 7, 8,1931.
«Arnold, Ralph, The Paleontology and stratigraphy of the marine Pliocene and
Pleistocene of San Pedro, Calif.: California Acad. Sci. Mem., vol. 3, 420 pp., 37 pis.,
1903. (Reprint Leland Stanford Jr. Univ., Contr. Biol. Hopkins Seaside Lab., No.
31,1903.)
sented along the water front and consequently was not
known by Arnold. Many species not recorded by
Arnold have been found in that unit and in others.
FIELD WORK
The field work on which this report is based was
started by W. S. W. Kew in 1921-22 and was continued
by him at intervals until 1924. The geology of the
area controlled at that time by the Palos Verdes Syn­
dicate, comprising about the western two-thirds of the
hills, was mapped on a topographic base (scale, 1:9,600;
contour interval, 5 feet) supplied by the company.
The geology of the remainder of the area was mapped
on the topographic map of the Redondo quadrangle
enlarged from a scale of 1:62,500 to a scale of 1:31,250.
The geologic map of the entire area was compiled on the
same enlarged map of the Redondo quadrangle. Kew
completed the first draft of a report in 1925 after his
resignation from the Geological Survey.
The topographic map' available for publication at
that time was unsuitable on account of the small scale,
and the project was laid aside. By 1928 maps pre­
pared on a scale of 1:24,000 by the Geological Survey
in cooperation with Los Angeles County were avail­
able for the entire area (San Pedro Hill, Wilmington,
and Torrance quadrangles). During the summer of
1930 the geology of the area lying outside the original
holdings of the Palos Verdes Syndicate was mapped by
W. P. Woodring on the new topographic maps enlarged
to a scale of 1:12,000. In view of difficulties en­
countered in transferring the geology from one topo­
graphic map to another and in view of recent advances
in stratigraphy, it later became evident that remapping
of the entire area on a scale of 1:12,000 was desirable.
This work was carried on by Woodring and M. N.
Bramlette during the summer of 1933 and by Woodring
during the summer of 1935. During the field season
of 1933 particular attention was given to the Miocene
Monterey shale, which had been studied previously by
Bramlette at many other localities in the Coast Ranges.
The scale used in mapping is adequate for work of
moderate detail. The results attained, however, can­
not be regarded as more than a detailed reconnaissance,
at least in the area underlain by Miocene strata. In
that area, which embraces the greater part of the hills,
exposures are generally poor, except along some of the
deep canyons and along the sea cliff. Distinctive
lithologic units seem to be rare in the Miocene section,
strata evidently of the same age change in facies from
place to place, and minor structural complications
prevent generally a determination of stratigraphic
position on a basis of regional structure. Neverthe­
less, the broad features of the Miocene stratigraphy
and the succession of foraminiferal zones appear to be
satisfactorily established.
It is difficult to show adequately on the geologic map
(pi. 1) the distribution of rock types along the sea
cliff, for at many places the cliff, is vertical or almost
vertical. Areas covered by talus along the cliff are
not shown on the map, as it would be confusing rather
than helpful to plot them.
Owing to more urgent matters, the preparation of
the report was delayed until 1939. In the meantime
a preliminary account 5 of the Miocene stratigraphy
s Woodring, W. P., Bramlette, M. N., and Kleinpell, R. M., Miocene stratigraphy
and paleontology of Palos Verdes Hills, Calif.: Am. Assoc. Petroleum Geologists
Bull., vol. 20, No. 2, pp. 125-149, 3 figs., 1936.