GEOLOGY AND PALEONTOLOGY OF PALOS - Pubs Warehouse

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correlation with the Franciscan of the Coast Ranges. The Franciscan, an extensive description of which has been published recently by Taliaferro, 24 consists chiefly, however, of arkosic sandstone, shale, radiolari.au chert, limestone, and volcanic rocks. Glaucophane schist and other metamorphic rocks are local and relatively rare rock types associated with intrusive igneous rocks. In view of these relations Woodford 25 designated the metamorphic rocks of the Palos Verdes Hills and the similar more extensive rocks of Santa Catalina Island as the Catalina metamorphic facies of the Franciscan. The absence of unaltered sedimentary rocks indicates that the mctamqrphics of the Palos Verdes Hills and Santa Catalina Island are older than the Franciscan, an alternative considered by Woodford. 26 This matter has been emphasized by Taliaferro, 27 who objected to including these metamorphics in the Franciscan. It may be advantageous to designate them as the Catalina schist. If the .metamorphics of the Palos Verdes Hills are older than Franciscan, they are Jurassic or older. On the basis of strat.igraph.ic relations in southern Oregon and less satisfactory evidence in the California Coast Ranges, Taliaferro 2S concluded that the age of the Fran ciscan can be restricted to narrow limits in the late Upper Jurassic Tithonian (used in the broad sense to include Port!andian) and possibly uppermost Kim- mcridgian. MIOCENE SERIES MONTEBEY SHALE GENERAL RELATIONS Strata of Miocene age rest directly on the Franciscan (?) schist. The Miocene deposits overlap the schist, basement .northward, the strata overlying the schist on the north, slope of the hills being younger than those on the south slope of the central part of the hills, where the base of the Miocene section is not exposed. The Miocene deposits include a variety of rocks, but hard silica-cemented shale and soft shale containing siliceous microfossils are the thickest and most con spicuous constituents. Early investigators of the geology of this region recognized that these unusual rocks are similar lithologically to those elsewhere in the Coast Ranges designated at that time the Miocene bituminous shale and later the Monterey shale. The >« Tnlinferro, N. L., Franciscan-Knoxvillo problem: Am. Assoc. Petroleum Geolo gists Bull., vol. 27, pp. 109-219, 7 pis., 7 figs., 1943. " Wood ford. A. 0., op. cit., p. 49. '» Woodford, A. 0., op. cit., p. 02. « Tnlinferro, N. L., op. cit., pp. 122-125. " Taliaferro, N. L., Geologic history and structure of the central Coast Ranges of California, in Jenkins, 0. P., and others, Geologic formations and economic develop ment of the oil and gas fields of California: California Div. Mines Bull. 118, pt: 2, pp. 125-120,1941; Geologic history and correlation of the Jurassic of Southwestern Oregon and California: Gool. Soc. America Bull., vol. 53, pp. 85-87, 1942; Franciscan-Knox- villo problem: Am. Assoc. Petroleum Geologists Bull., vol. 27, pp. 190-195,1943. MIOCENE SERIES 13 stratigraphic nomenclature of the Miocene section in coastal southern California became confused, however, at a later date by the introduction of two local forma tion names for Miocene strata including shale of Mon terey type Modelo formation proposed for strata in the Santa Clara Valley in the Ventura Basin northwest of the Palos Verdes Hills, and Puente formation pro posed for strata in the Puente Hills on the north border of the Los Angeles Basin northeast of the Palos Verdes Hills and by the raising of Monterey to group rank to include the underlying Vaqueros sandstone. The Miocene strata in the Palos Verdes Hills have been assigned generally to the Modelo formation and the corresponding Miocene subsurface section in the ad joining Los Angeles Basin to the Puente formation. It has been proposed recently to restore the name "Mon terey shale" as a formation name for Coast Range Miocene strata including shale of Monterey , type regardless of varying stratigraphic position within the Miocene. 29 According to this proposal, the Miocene strata in the Palos Verdes Hills are assigned to the Monterey shale. The Monterey shale of the Palos Verdes Hills is of middle to upper Miocene age. It has a maximum ex posed thickness of about 2,000 feet. The underlying schist does not crop out, however, in the area where the oldest strata are found. Outcrop data show a southward increase in thickness through the addition of older strata at the base of the section. Subsurface data in the Point Fermin and Long Point areas indicate that the maximum thickness of the Miocene is at least 4,000 feet. LITHOLOGY Details of the stratigraphy and lithology of the Monterey ( shale were not determined in many areas, owing to meager exposures, to the apparent absence of distinctive lithologic units throughput hundreds of feet of strata, to minor structural complications that prevent determination of stratigraphic position on a basis of regional structure, and to changes in thickness and facies. The main features of the stratigraphic and lithologic succession seem to be well defined in some areas, but in other areas recognition of the main units is difficult, owing to lateral variations. On the basis of the succession in areas where the relations are fairly certain, the Monterey shale of the Palos Verdes Hills is divided into three named and mapped members, the principal features of which are summarized in the follow ing table: 28 Woodring, W. P., Stewart, Ralph, and Richards, R. W., Geology of the Kettle- man Hills oil field, Calif.; stratigraphy, paleontology, and structure: TJ. S. Geol. Survey Prof. Paper 195, pp. 122-123,1940 [1941]. (The history of the name "Monterey" and the arguments involved in the proposal to use Monterey shale as a formation name are discussed in this publication.) Woodring, W. P., Bramlette, M. N., and Kleinpell, R. M., Miocene stratigraphy and paleontology of Palos Verdes Hills, Calif. Am. Assoc. Peteroleum Geologists Bull., vol. 20, No. 2, pp. 127,131,1936.
14 GEOLOGY AND PALEONTOLOGY OF PALOS VERDES HILLS, CALIFORNIA Subdivision Malaga mudstonemember... Valmonte diatomite member. Altamira shale member: Upper part...------- Middle part- Lower part. 1 See footnote, p. 39. Thick ness (feet) 300-600 300-500 100-300 400-675 276+ Subdivisions and principal features of Monterey shale in Palos Verdes Hills Principal lithologic constituents Radiolarian mudstone. Diatomite, diatomaceous shale, diatomaceous mudstone. Phosphatic shale, bituminous shale. Cherty shale, porcelaneous shale, chert, limestone. Silty,shale, sandy shale- Bramlette's terminology 30 for the siliceous rocks of the' Monterey is adopted in the present report. The terms used are defined briefly as follows: Chert: Hard massive dense vitreous rock composed prin cipally of silica. Laminated chert: Laminated but nonplaty rock similar to the chert mentioned above. Cherty shale: Hard platy dense vitreous rock composed prin cipally of silica. The most common type in the Palos Verdes Hills. Porcelaneous mudstone: Hard massive nonlustrous rock composed of silica and fine-grained elastics. Porcelaneous shale: Hard laminated platy nonlustrous rock composed of silica and fine-grained elastics. Diatomite: Soft massive or laminated rock containing abun dant diatoms. Diatomaceous mudstone: Soft massive rock composed of fine-grained clastic material containing diatoms. Diatomaceous shale: Soft layered or laminated rock com posed of fine-grained clastic material containing diatoms. Radiolarian mudstone: Soft massive rock composed of fine grained clastic material in which Radiolaria are more conspicuous than diatoms. Diatomite, diatomaceous mudstone, and diatoma ceous shale are loosely defined field terms. There are, of course, gradations between the three types. The term "diatomite" is used for rock at least 50 percent of which consists of diatoms. Rhythmically bedded shale refers to alternations of different rock types in units several feet or several inches thick. A finer lamination consisting of alterna tions of the same types is superimposed generally on the coarser units. Rhythmic bedding is characteristic of the fine-grained Monterey rocks, the term being used in the descriptive matter only for striking ex amples. The term "phosphatic shale" is used for shale containing layers and nodules of phosphatic material, probably impure cellophane. The phos phatic shale in the upper, part of the Altamira member and in the Valmonte member is soft. Phosphatic shale or siltstone in the middle part of the Altamira is generally hard and siliceous or calcareous. The term "bituminous shale" is used for tough, brown shale rich in organic matter. The three divisions of the Altamira member include coarse-grained clastic rocks sandstone, conglomerate, and breccia which are locally thick. Such material was not observed in the other two members of the Monterey shale. . Many of the sandstones contain a '° Bramlette, M. N., The Monterey formation of California and the origin of its siliceous rocks: U. S. Geol. Survey Prof. Paper (in preparation). Minor lithologic constituents Diatomite, diatomaceous shale, siltstone, limestone, volcanic ash. Mudstone, phosphatic shale, limestone, black chert, cherty shale, volcanic ash. Cherty shale, porcolaneous shale, silty shale, limestone, diatomaceous silt, diatomaceous shale, sandstone (locally thick), local brec- ciated shale, bentonitic tuff, volcanic ash, Silty shale, siltstone, diatomite, diatomaceous shale, phosphatic shale, sandstone, conglo merate, bentonitic tuff, pumice tuff (Mira leste tuff bed). Cherty shale, porcelaneous shale, limestone, sandstone, bentonitic tuff (including Portu guese tuff bed), local breccia composed of schist debris. Fossils Foraniinifera of Bolivina oWii/wazonc 1 . Radio- laria, diatoms, and other siliceous microfossils. Foraminifera of Bolivina hughesi zone, including Bolivina. decurtata and Bolivina goudkoffi sub zones. Diatoms and other siliceous microfossils. Hyalopecten &B.H. pecktiami. Foraminifera of Bolicina modeloensis and Buli- mina unigerinaformis zones. Diatoms and other siliceous microfossils. Foraminifera of Siphogenerina reedi, Siphogene- rina nuciformis. and Siphogenerina collomi zones. Fish scales. 'Diatoms and other sili ceous microfossils generally rare. Turrilelta ocoyana and other mollusks locally in sand stone. Foraminifera of Siphogenerina branneri zone. Fish scales. Diatoms generally only in lime- . stone concretions. notable quantity of blue soda amphibole derived from blue schist containing glaucophane or other soda am- phiboles. Blue-schist sandstone is a convenient term for such sandstone. Limestone, presumably more or less dolomitic, occurs throughout the Monterey but is much more abundant in the Altamira member than in the others. In many Altamira areas the only natural outcrops are ledges of limestone, and the ground is strewn with pieces of limestone. The limestone occurs as lenses, ranging in thickness from a few inches to several feet, and as con cretions. In the Altamira member the thickest lime stone beds are massive; the thinner beds are massive or laminated, and some of the laminated limestone is siliceous. In the Valmonte and Malaga members con cretions are more abundant than lenses. Concretions in laminated rock are laminated or massive. The Alta mira member contains also thin beds made up largely of dolomite grains having the texture of coarse-grained sand. Volcanic material is likewise common throughout the Monterey. It occurs generally as distinct beds containing virtually no other material. In the Alta mira shale the beds of volcanic material consis-t of more or less bentonitic tuff and pumiceous tuff, with the local exception of vitric ash near the top of the member, whereas in the Valmonte and Malaga members they consist of vitric ash. Owing to their stratigraphic importance two beds of tuff are named: the Portu guese tuff, a thick bentonitic tuff at the top of the lower part of the Altamira and the Miraleste tuff, a thin pumiceous tuff in the middle part of the Altamira. As in many other areas, the lower part of the Mon terey shale is characterized by hard silica-cemented shale, much of which contains molds of diatoms, and the upper part by softer rocks containing abundant pre served diatoms. This distinction affords the most ob vious basis for a lithologic subdivision and might be expected to prove useful in mapping. That this litho logic change does not take place even approximately at the same horizon in different areas in the Palos Verdes Hills is indicated by tracing the Miraleste tuff, as well as by other lithologic data and the foraminiferal faunas. Despite the varying stratigraphic position of the lithologic change, it would ordinarily be regarded as a satisfactory basis for the recognition and mapping of members. Such procedure is beset with special difficulties, however, in the Palos Verdes Hills, owing
Page 1: UNITED STATES DEPARTMENT OF THE INT
Page 4 and 5: IV CONTENTS Stratigraphy and paleon
Page 6 and 7: GEOLOGY AND PALEONTOLOGY OF PALOS V
Page 8 and 9: and paleontology and a general acco
Page 10 and 11: 1902. Arnold, Delos, and Arnold, Ra
Page 12 and 13: 1933. Davis, W. M., Glacial epochs
Page 14 and 15: GEOGRAPHY FIOUIIE 1. Sketch map of
Page 16 and 17: year on the north slope, and small
Page 20 and 21: LITHOLOGIC UNIT MIOCENE SERIES ' 15
Page 22 and 23: shale and porcelaneous mudstone rat
Page 24 and 25: GEOLOGICAL SURVEY PROFESSIONAL PAPE
Page 26 and 27: GEOLOGICAL SURVEY ^ HnMMHMHMHBMHMHM
Page 28 and 29: part of the Altamira shale in the P
Page 30 and 31: slide debris that may conceal a fau
Page 32 and 33: Section of middle part of Altamira
Page 34 and 35: pi) a tic shale, and limestone in t
Page 36 and 37: is in the upper part of the sandsto
Page 38 and 39: Section of upper part of Altamira s
Page 40 and 41: Section of Monlerey shale, includin
Page 42 and 43: MIOCENE SERIES Foraminifera from up
Page 46 and 47: GEOLOGICAL SURVEY PKOFESSIONAL PAPE
Page 50 and 51: there appears to be no displacement
Page 52 and 53: oad from Girard to Mohn Spring in t
Page 54 and 55: nose of a spur on the north side of
Page 56 and 57: is used for the formation in that a
Page 58 and 59: spring of 1938. Owing to urban and
Page 60 and 61: y Crickmay u to the Santa Barbara f
Page 62 and 63: The base of the San Pedro sand is d
Page 64 and 65: y Dr. Hampton Smith, Bryozoa and mo
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GEOLOGICAL SURVEY PROFESSIONAL PAPE
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including numerous specimens of Bit
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gravel as much as 20 feet thick mad
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fossils were found near the seaward
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NORTHERN SAN PEDRO In the northern
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is at an 1 altitude of 365 feet, mu
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son tod by 43 collections in the ma
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fiocl as M. cf. M. varitosa. M. var
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a width of 3.3 millimeters. Only th
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ased on fossils from San Pcdro, is
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Pedro district, is recognized in th
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According to Arnold's description o
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midellids are on record, half of wh
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fortis is widespread and locally ab
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Progabbia cooperi occurs in the Lom
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ANOM1IDAE The Recent California spe
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opuntia survived from the Pliocene
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millimeters) from Puget Sound. The
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lower Pleistocene units, in deposit
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in interpreting the Pleistocene pal
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PLEISTOCENE SERIES 89 Pleistocene m
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There are no shallow-water Littorin
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localities therefore are inferred t
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locality 70 species of gastropods a
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is better known. Calicantharus is a
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The species in the preceding list b
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It is apparent from the preceding t
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graphic or depth range have taken p
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Pedro district. The close faunal si
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age extend over an entire terrace.
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eludes volcanic agglomerate or brec
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San Pedro district, where those str
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during cutting of the Pleistocene m
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GEOLOGICAL SURVEY AIIil'LANE VIEW O
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116 GEOLOGY AND PALEONTOLOGY OF PAL
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G92787 45 10 PLATES 28-37 127
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GEOLOGICAL SUEVEY PROFESSIONAL PAPE
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PLATE 29 [Species and varieties ill
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PLATE 37 [Species illustrated still
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Page Calicantharus fortls..........
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142 INDEX Page kennerlyi, Mercenari
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144 INDEX Page Rissoinidae_________
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