GEOLOGY AND PALEONTOLOGY OF PALOS - Pubs Warehouse

30 GEOLOGY AND PALEONTOLOGY OF PALOS VERDES HILLS, CALIFORNIA
Section of upper and middle parts of Altamira shale member of
Monterey shale in Agua Amarga Canyon at' head of Lunada
Bay Continued
Middle part Continued. A. in.
13. Fissile, somewhat porcelaneous shale___--____ 5
12. Porcelaneous shale.___-_----------___-_-_. 2 2
11. Fissile, somewhat porcelaneous shale___-_-__- 1 3
10.- Hard cherty shale._______________ _______ 9
9. Calcareous siltstone---------------.-.------- 1 2
8. Hard cherty shale._________________1______ 1 11
7. Brown somewhat porcelaneous shale____-_-__ 11
6. Hard cherty shale in layers 1 to 3 inches thick
alternating with softer shale in layers Yz to 1
inch thick__---___-________-________-___ , 5 8
5. Soft, somewhat porcelaneous shale_._____-_-_- 3 1
4. Brown phosphatic shale.____________________ 7
3. Tuffaceous (?) sandstone.------------------ 3
2. Dark brown shale containing phosphatic
stringers ____--_--_-_---__----__---.---- 2 11
1. Calcareous siltstone. Base not exposed------ 2 8
Thickness of section__-_____-_---_------- 135 2
A thickness of approximately 100 feet in the fore­
going section is assigned to the upper part of the Alta­
mira shale. The uppermost part of this division is
exposed in the trough of the syncline on the south side
of Palos Verdes Point under a thin cover of the over­
lying Valmonte diatomite member, where the section
given below was measured. This section and that
measured on Agua Amarga Canyon could not be cer­
tainly tied together, owing to a possible fault in the
area of burnt shale immediately to the left of the
relatively steeply dipping strata shown on plate 8. If
there is no significant break in that area, the base of
the Palos Verdes Point gection is estimated to be about
150 feet above unit 34 of the Agua Amarga Canyon
section, making a total estimated thickness of about
250 feet for the upper part of the Altamira.
Section of upper pait of Altamira shale member and Valmonte
diatomite member of Monterey shale in sea cliff on south side
of Palos Verdes Point
Valmonte diatomite member: _ Ft. in.
16. Diatomaceous and phosphatic shale. Thick­
ness estimated. ____________--_____-__-.,_ 10 0
15. Phosphatic shale. Thickness estimated-__-__ 10 0
14. Lens of diatomaceous shale-.----.-/-----.-- 6
13. Silty phosphatic shale.___________________ 6 6
12. Diatomaceous and phosphatic shale.________ 3 2
Upper, part of Altamira shale member:
11. Phosphatic shale stained greenish yellow and
thin zones of harder shale________________ 6 7
10. Porcelaneous shale ________________________ 6
9. Limestone__________________--_-_____---_ 1 0
8. Phosphatic shale__._______________________ 11,
7. Porcelaneous shale and thin zones of softer
bituminous shale--_-_--_s.__-____-_---___ 3 5
6. Phosphatic shale________-___--___--_---_-_ 10
5. Limestone--.---..---_____________________ 1 3
4. Porcelaneous shale and thin zones of softer
bituminous shale._______ ______..__-____ 4 9
3. Bituminous shale, including a 2-inch layer of
harder shale_____________________________ 2 8
2. Porcelaneous shale. ____--_----_---__------ 1 11
1. Limestone-
Thickness of section.__-_-_--__-___--_-__ 57 6
Bituminous shale and phosphatic shale, locally burnt,
are exposed in highway cuts in the synclinal area in
the eastern part of the Margate residential area inland
from Lunada Bay.
CREST OF HILLS
Phosphatic shale, including toward the top thin
laminae of diatomaceous shale, underlies the flanks of
the broad, shallow syncline along the crest of the hills,
but is well exposed only in the cliffs near the head of
Altamira Canyon and its tributaries and in highway
cuts. In the following section, measured in a tributary
of the middle fork of Altamira Canyon (third canyon
from right in background, pi. 4), strata assigned to
the upper part of the Altamira have a thickness of
about 185 feet (column 2, pi. 3).
Section of Monterey shale, including upper part of Altamira shale
member, in tributary of middle fork of Altamira Canyon
Valmonte diatomite member:
58. Limestone____---__-----------_---_-_..___
* 57. White silty shale______-__-._. _____________
56. Bentonitic clay. ____---_-__-_-_-__________
55. Diatomaceous shale. ______________________
54. Laminated cherty and porcelaneous shale. ___
53. .Diatpmite.------. ---------------.-__.____
.52. Laminated chert.---.-.--... _.-_-._.______
51. White silty shale.----,---------.. -.__-._...
50. Limestone.... ------ ______________________
49. Diatomaceous shale and diatomite..__ _______
48. Laminated cherty and diatomaceous shale____
47. Diatomaceous shale and diatomite_____ ______
46. Laminated chert_ ___-_----__--__-___.__.__
45. Diatomaceous shale. ____---------._.--._..
44. Laminated chert. _ __-_----__.-.--_________
43. White silty shale, thin laminae diatomaceous--
42. Porcelaneous shale. ________________________
41. White silty shale. _________________________
40. Limestone mapped as base of Valmonte diato-
rnite. __ ________________________________
Altamira shale member:
Upper part:
39. Phosphatic shale and diatomaceous shale
in thin laminae. ____________________
38. Poorly exposed brown phosphatic shale;
a few diatoms in some layers. ________
37. Limestone----------------------.---..
36. Poorly exposed brown phosphatic shale...
35. Limestone.... ---_-__- _______________
34. Brown phosphatic shale, lower part poorly
exposed-- .----_-- --.----.---.--...I
33. Limestone _ ____-___l____-____________
32. Poorly exposed brown phosphatic shale
and thin laminae of white diatomaceous
shale. Laminae of diatomaceous shale
more abundant than in unit 30, gradu­
ally less abundant upward- ___- _______
31. Limestone.--------------------------.
30. Poorly exposed brown phosphatic shale
and thin white laminae of diatomaceous
shale, some layers of .which consist
mostly of Thalassiothrix.. _________'____
29. Brown phosphatic shale and thin zones of
porcelaneous shale___--------_-___.__
28. Limestone _ _________________________
27. Brown phosphatic shale including 7 zones
of porcelaneous shale 1 to 3 inches thick.
26. Limestone-... --_------.--------_---.-
25. Unexposed. __--------__.-----_--.----
24. Brown phosphatic shale; a few thin zones
of porcelaneous shale in lower half _____
23. Limestone.^.. _-__------_--------.--.-
22. Unexposed- __---_-----_--_-----___-__
21. Brown bituminous -shale and thin zones of
porcelaneous shale_____-______ _______
20. Brown bituminous shale, a few phosphatic
nodules ______-_-_-____---_____-____
19. Dense limestone __ _ __ ________________
1 8. Unexposed __________ _________-__l-___
1 7. Brown phosphatic shale. _______________
16. Limestone. -___-____-___----_._____.--
15. Brown phosphatic shale_-__-_______.___
14. Limestone containing phosphatic nodules.
13. Brown bituminous shale containing phosphatic
nodules. _____________________
12. Poorly exposed soft shale and thin zones
of porcelaneous shale_ ___-__-_-_-__-.
11. Limestone----____----_--_------_--___
10. Brown bituminous shale, lower part con­
taining scattered phosphatic nodules
and upper part including many thin
phosphatic layers_-_______.__________
ft-
1 0
3
2
6
5 6
10 0
1-6
10
1 6
3 0
11
4 6 3
3 0 5
3 0 3
4 0
11
7 6 7
12 .6
1 0
10 8 6
12 1
15 2
20
2 4
20 14
11
11 1
3 0
0 00
3 10
11
6 11