GEOLOGY AND PALEONTOLOGY OF PALOS - Pubs Warehouse

32
GEOLOGY AND PALEONTOLOGY OF PALOS VERDES HILLS, CALIFORNIA
chiefly of rather soft porcelaneous shale and silty shale,
is almost 100 feet thick at the top of the cliff but thins
south westward down the cliff, evidently through grada­
tion into the sandstone forming the overlying unit.
The upper sandstone forms the 100-foot sheer cliff
at the Point (pi. 9) and has approximately that thick­
ness. It consists of blue-schist sandstone, bituminous
and phosphatic shale, and breccia. The sandstone is
of coarser grain than that in the lower unit and contains
pieces of schist generally a few inches long but excep­
tionally as much as 7 feet long. The beds of sandstone
are as much as 5 to 10 feet thick. Some contain bone
fragments, one of which was observed to have a brilliant
blue coat, presumably viyianite. The bituminous and
phosphatic shale is thin-bedded, and some layers
contain diatoms. The thickness of the beds of breccia
ranges from a fraction of a foot to several feet.- Most
of the beds consist of shale fragments ranging in length
from a few inches to several feet (pi. 10, B). Layers
of shale can be traced into breccia composed of shale
fragments of identical composition and embedded in
a sandstone matrix like that interbedded with the shale.
Breccia composed of sandstone or of mixtures of shale
and sandstone is relatively rare. The breccias were
formed evidently while the sediments were being
deposited; that is, they are evidently penecontem-
poraneous, and the shale and sandstone were consol­
idated enough to form fragments when they were
ruptured. The rupturing may have been due to
earthquake jars and submarine sliding. The entire
upper sandstone has other curious depositional features.
At the base of many of the beds of sandstone is a scour
discontinuity, as may be seen on plate 10, B. Discord­
ant contacts, including truncation of minor folds, are
common. Isolated fragments of shale occur hi sand­
stone, and sandstone grades laterally into shale.
On the west side of Point Fermin (pi. 9, A) the shale
underlying the upper sandstone appears to be thicker
than on the east side, but much of it is obscured by
talus. As exposed on the cliff it consists of porce­
laneous and silty shale underlain by silty shale, phos­
phatic shale, and thin beds of fine-grained blue-schist
sandstone. A 3-foot bentonitic tuff is included in the
shale 15 feet below the irregular contact at the base
of the upper sandstone. Foraminifera of the Bolivina
modeloensis zone were found in silty shale at the foot
of the cliff about 65 feet stratigraphically below the
base of the upper sandstone (locality 16).
-Half a mile to a mile northwest of Point Fermin
blue-schist sandstone including a few beds of brecciated
shale is exposed along the sea cliff. This sandstone
corresponds apparently to the lower sandstone on the
east side of Point Fermin. The mineralogy of a sample
of sandstone from this area was described by Wood-
ford. 61 Silty shale at the top of the cliff, along the
road leading to Whites Point, contains Foraminifera
of the Bolivina modeloensis zone (locality 14). This
shale appears to overlie the sandstone just mentioned.
The upper and middle parts of the Altamira are not
satisfactorily differentiated in the area inland from
Whites Point. Silty shale interbedded with cherty
shale at locality 15 contains Foraminifera assigned
doubtfully to the Bolivina modeloensis zone. Phos­
phatic shale was not observed in this region.
FOSSILS
FORAMINIFERA
Identifiable Foraminifera were found in the upper
part of the Altamira shale only at localities near Point
Fermin and Whites Point. Leached and crushed
Foraminifera were observed in the more typical phos­
phatic and bituminous shale of other areas. The
material collected is assigned by Kleinpell to his
Mohnian stage, the base of which corresponds to the
base of the upper Miocene according to current Coast
Range usage. The faunas from localities 14 and 16,
and doubtfully from locality 15, are referred to the'
Bolivina modeloensis zone (zone E of preliminary
paper) 62 and that from locality 17 to the overlying
Bulimina uvigerinaformis zone (zone F of preliminary
paper). Locality 17 is close to the top of the Altamira
shale according to the stratigraphic classification
adopted.
The following species were identified by Kleinpell:
81 Woodford, A. O., The San Onofre breccia: California Univ., Dept. Qeol. Sci..
Bull., vol. 15, p. 210, 1925.
62 Woodring, W. P., Bramlette, M. N., and Kleinpell, R. M., op. cit. (Am. Assoc.
Petroleum Geologists Bull., vol. 20), pp. 125-149.
Foraminifera'from upper part of Altamira shale member of Monterey shale
[Identifications by R. M. Kleinpell. R, rare; F, few; C, common; A, abundant]
Species
Elphidium granti Kleinpell (Elphidium aff. E. crispum (Linne))(Kleinpell, pi. 1$, figs 1, 11) '.... ..-..-....-...--..-.--..-..
Bolivina fioridana Cushman.. _ .................................... -.... ... ... ..........................................
Seo footnotes at end of table.
Bolivina modeloensis zone
' 15
F
R
R
R
F
C
14
(?)
R
F
R
C
C
R
A
R
R
Localities
16
R
F
R
R
R
R
C
R
F
R
F
R
Bulimina
uvigerina­
formis zone
17
R F
R
R
R
R
(?)
C
R