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NARROW
GeoRef Subject
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all geography including DSDP/ODP Sites and Legs
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Mexico
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Baja California (1)
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Sonora Mexico (1)
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North America
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Peninsular Ranges Batholith (2)
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Peninsular Ranges (2)
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San Miguel Island (2)
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Santa Cruz Island (1)
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United States
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California
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Anza-Borrego Desert State Park (1)
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Channel Islands (1)
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Imperial County California (1)
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Salton Trough (1)
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San Diego County California
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San Diego California (3)
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Santa Ana Mountains (1)
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Santa Barbara County California (2)
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Southern California (3)
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Texas (1)
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fossils
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Invertebrata
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Mollusca
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Bivalvia (1)
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geochronology methods
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paleomagnetism (1)
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U/Pb (2)
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geologic age
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Cenozoic
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Tertiary
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Neogene (2)
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Paleogene
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Eocene
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lower Eocene (1)
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middle Eocene (1)
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upper Eocene
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Poway Conglomerate (3)
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Paleocene
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upper Paleocene (2)
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Mesozoic
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Cretaceous
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Upper Cretaceous
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Campanian (1)
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Maestrichtian (1)
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Rosario Formation (1)
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Senonian (1)
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Jurassic
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Upper Jurassic
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Tithonian (1)
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igneous rocks
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igneous rocks
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volcanic rocks
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rhyolites (2)
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metamorphic rocks
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turbidite (1)
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minerals
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carbonates
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dolomite (1)
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silicates
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orthosilicates
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nesosilicates
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zircon group
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zircon (1)
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Primary terms
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absolute age (2)
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Cenozoic
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Tertiary
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Neogene (2)
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Paleogene
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Eocene
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lower Eocene (1)
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middle Eocene (1)
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upper Eocene
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Poway Conglomerate (3)
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Paleocene
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upper Paleocene (2)
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deformation (1)
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faults (1)
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geochemistry (3)
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ground water (1)
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igneous rocks
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volcanic rocks
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rhyolites (2)
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Invertebrata
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Mollusca
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Bivalvia (1)
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Mesozoic
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Cretaceous
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Upper Cretaceous
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Campanian (1)
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Maestrichtian (1)
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Rosario Formation (1)
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Senonian (1)
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Jurassic
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Upper Jurassic
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Tithonian (1)
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Mexico
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Baja California (1)
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Sonora Mexico (1)
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North America
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Peninsular Ranges Batholith (2)
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paleogeography (1)
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paleomagnetism (1)
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plate tectonics (1)
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sea-level changes (1)
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sedimentary petrology (3)
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sedimentary rocks
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carbonate rocks (1)
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clastic rocks
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conglomerate (5)
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fanglomerate (1)
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mudstone (1)
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sandstone (3)
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sedimentary structures
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planar bedding structures
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cross-stratification (1)
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flaser bedding (1)
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laminations (1)
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sedimentation (5)
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sediments (1)
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stratigraphy (5)
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tectonics (1)
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United States
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California
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Anza-Borrego Desert State Park (1)
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Channel Islands (1)
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Imperial County California (1)
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Salton Trough (1)
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San Diego County California
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San Diego California (3)
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Santa Ana Mountains (1)
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Santa Barbara County California (2)
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Southern California (3)
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Texas (1)
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sedimentary rocks
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sedimentary rocks
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carbonate rocks (1)
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clastic rocks
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conglomerate (5)
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fanglomerate (1)
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mudstone (1)
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sandstone (3)
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turbidite (1)
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volcaniclastics (1)
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sedimentary structures
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sedimentary structures
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planar bedding structures
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cross-stratification (1)
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flaser bedding (1)
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laminations (1)
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sediments
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sediments (1)
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turbidite (1)
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volcaniclastics (1)
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Upper Jurassic Peñasquitos Formation—Forearc basin western wall rock of the Peninsular Ranges batholith
Improved depositional age constraints and stratigraphic description of rocks in San Diego require designation of a new Upper Jurassic formation, herein named the Peñasquitos Formation after its exposures in Los Peñasquitos Canyon Preserve of the city of San Diego. The strata are dark-gray mudstone with interbedded first-cycle volcanogenic sandstone and conglomerate-breccia and contain the Tithonian marine pelecypod Buchia piochii. Laser-ablation–inductively coupled plasma–mass spectrometry (LA-ICP-MS) zircon 206* Pb/ 238 U ages of 147.9 ± 3.2 Ma, 145.6 ± 5.3 Ma, and 144.5 ± 3.0 Ma measured on volcaniclastic samples from Los Peñasquitos and Rancho Valencia Canyons are interpreted as magmatic crystallization ages and are consistent with the Tithonian depositional age indicated by fossils. Whole-rock geochemistry is consistent with an island-arc volcanic source for most of the rocks. The strata of the Peñasquitos Formation have been assigned to the Santiago Peak volcanics by many workers, but there are major differences. The Peñasquitos Formation is marine; older (150–141 Ma); deformed everywhere and overturned in places; and locally is altered to pyrophyllite. In contrast, the Santiago Peak volcanics are nonmarine and contain paleosols in places; younger (128–110 Ma); undeformed and nearly flat lying in many places; and not altered to pyrophyllite. The Peñasquitos Formation rocks have also been assigned to the Bedford Canyon Formation by previous workers, but the Bedford Canyon is distinctly less volcanogenic and contains chert, pebbly mudstones, and limestone olistoliths(?) with Bajocian- to Callovian-age fossils. Here, we interpret the Peñasquitos Formation as deep-water marine forearc basin sedimentary and volcanic strata deposited outboard of the Peninsular Ranges magmatic arc. The Upper Jurassic Mariposa Formation of the western Sierra Nevada Foothills is a good analog. Results of detrital zircon U/Pb dating from an exposure of continentally derived sandstone at Lusardi Creek are consistent with a mixed volcanic-continental provenance for the Peñasquitos Formation. A weighted mean U/Pb age of 144.9 ± 2.8 Ma from the youngest cluster of detrital grain ages is interpreted as the likely depositional age. Pre-Cordilleran arc zircon age distributions (>285 Ma) are similar to Jurassic deposits from the Colorado Plateau, with dominant Appalachian-derived Paleozoic (300–480 Ma), Pan African (531–641 Ma), and Grenville (950–1335 Ma) grains, consistent with derivation either directly, or through sediment recycling, from the Colorado Plateau Mesozoic basins and related fluvial transport systems. Appalachian- and Ouachita-like detrital zircon age distributions are characteristic of Jurassic Cordilleran forearc basins from northeast Oregon to west-central Baja California, indicating deposition within the same continent-fringing west-facing arc system.
Neogene sturzstrom deposits, Split Mountain area, Anza-Borrego Desert State Park, California
Abstract The Neogene stratigraphic section in the Split Mountain area exposes megabreccia deposits up to 12 km long with volumes up to 3 × 10 8 m 3 . Shattered-rock domains still portray the bedrock distribution of lithologies. Jigsaw-puzzle fabric occurs on a variety of scales from microscopic to outcrop. Broken and stretched pegmatites tend to rise upward as step-ups in the inferred down-flow directions. Upper Miocene subaerial megabreccias about 65 m thick disturbed the underlying strata to depths less than a meter during their emplacement. This includes producing grooved and decapitated stones both in the substrate and below shear surfaces especially within the basal few meters of the megabreccia deposits. The lower portions of a megabreccia are rich in step-ups, ramps, and crushed-rock streamers that rise upward in the down-flow direction. After flooding of the basin by the ancestral Gulf of California, a lower Pliocene megabreccia moved across the sea floor deforming underlying sedimentary layers by injections and sunken megabreccia lobes that locally caused tightly folded bottom-sediment packages >35 m thick to rise as diapirs. Near the leading edge, on the southwest corner of the deposit, there is a small volume of more traditional sandy conglomerate deposited as the mass rapidly slowed and stopped. Both subaerial and subaqueous megabreccias contain lithologic domains that preserve the distribution of bedrock lithologies, jigsaw-puzzle fabric, step-ups and crushed-rock streamers; these features all require non-turbulent flow. These huge volumes of shattered bedrock moved 10–12 km distance in late Miocene as dry subaerial masses, and again across the floor of an early Pliocene inland sea. All the observed features strongly indicate flow as sturzstroms.
Provenance investigations using magnetic susceptibility
THICK-BEDDED, COARSE-GRAINED DEEP-WATER DEPOSITS, CRETACEOUS AND PALEOGENE, CENTRAL CALIFORNIA
The Great Valley basin holds a remarkably thick and complete sedimentary record of the history of the Mesozoic-Cenozoic active tectonic margin of central California (Dickinson and Seely, 1979). In addition, the fill of this basin hosts some of the most significant petroleum reserves in the United States (Graham, 1987). Thus, the excellent exposures of upturned basin fill, which crop out for 700 km along the western margin of the north-south elongate basin, afford superb opportunities to examine the depositional style and stratigraphic architecture of the Great Valley basin. Prominent among the strata of the basin are thick sequences of exceptionally thick-bedded, and coarse-grained deep-marine Cretaceous and Paleogene strata which crop out in the Diablo Range near Coalinga in central California (Figure 1). During the 1960’s-1980’s, these strata were studied extensively because of their importance as recorders of paleogeographic and paleotectonic conditions during a critical period in continental margin history (e.g, Dickinson and others, 1979; Nilsen and McKee, 1979; Nilsen, 1987; Moxon and Graham, 1987). Specifically, the Upper Cretaceous Panoche Group and Paleocene-Eocene Lodo Formation comprise deep-marine turbidite sediments which were deposited in a forearc basin setting. Over the 70 million year period recorded by these deposits, the Great Valley basin evolved from a broad, deep-water trough in the Cretaceous to a segmented, residual, borderland-style basin, the San Joaquin sub-basin of the Great Valley basin, during the Paleogene (Nilsen and Clarke, 1975; Dickinson and others, 1979).
THE PALEOGENE CANTUA SANDSTONE, SOUTHERN DIABLO RANGE, CALIFORNIA: FACIES ARCHITECTURE OF A SAND-RICH, STRUCTURALLY-CONTROLLED, DEEP-SEA DEPOSITIONAL SYSTEM
The Paleogene Cantua Sandstone Member of the Lodo Formation was deposited primarily by sand-rich, high-density sediment gravity flows fed by a submarine canyon into a structurally controlled, relatively deep-marine, basin bounded to the north, south, and east by shallow-marine shelves. The Cantua Sandstone probably represents, at least in part, the deep-water equivalent of the deltaic-neritic Gatchell sandstone which is an important petroleum reservoir at the East Coalinga Extension Field (Ryall, 1974; Graham and Berry, 1979; Harun, 1984). Graham and Berry (1979) interpreted portions of the Cantua in the subsurface to be “supra-fan” deposits. Nilsen (1981) interpreted outcrops of the Cantua Sandstone as dominantly “supra-fan” and middlefan channel deposits. These general characteristics and interpretations serve as a basis for classifying the Cantua Sandstone as a sand-rich, point-sourced submarine fan (Reading and Richards, 1994). It is important to note, however, that the morphologic term fan is probably not applicable to the Cantua Sandstone system because it was deposited in a confined, rather than unconfined, basin.
Submarine fan channel and levee complexes have long been recognized as an integral component of deep-sea depositional systems (Buffington, 1952). Ancient channel/levee complexes show promise for oil and gas development and production (Imperato and Nilsen, 1988, 1990), particularly in an era where exploration is moving into deep-water and more distal depositional setting targets. We need to achieve a better understanding of the internal arrangement of channel, levee, and distal overbank facies within deep-sea depositional systems. This knowledge may lead to more refined basin analyses, more detailed reservoir characterizations, and more accurate reservoir models.
NEOPROTEROZOIC CARBONATE SUCCESSIONS, DEATH VALLEY, CALIFORNIA: COMPARISON AND CONTRAST WITH PHANEROZOIC EXAMPLES
The study of Phanerozoic carbonate platforms has had a long, successful scientific history producing a wealth of information regarding carbonate genesis and implications for unraveling paleoclimatic and paleooceanographic conditions, eustatic variations, and basin evolution (e.g., Heckel, 1974; Ginsburg and Klein, 1975; Wilson, 1975; Hardie, 1977; Goldhammer and others 1987; Read, 1985; Tucker and Wright, 1990). Over the past decade or so, several workers have had similar success in documenting and understanding the genesis of Precambrian carbonate rocks (e.g., Bertrand-Sarfarti and Moussine-Pouchkine, 1983; Beukes, 1987; Derry and others, 1989; Eriksson, 1977; Grotzinger, 1986a,b, 1989; Hoffman, 1975; Kaufman and Knoll, 1995; Knoll and Swett, 1990; Tucker, 1983; Zempolich and others, 1988). In fact, it is a consequence of studies on Precambrian carbonates that we in the geoscience community are presently in the privileged position of witnessing firsthand the exciting insights being obtained to help resolve problems as fundamental as the evolution and emergence of early life to secular variations in atmospheric and oceanic composition of the earth system (e.g., Grotzinger, 1994; Knoll, 1991; Knoll and Walter, 1992).
CYCLE AND SEQUENCE STRATIGRAPHY OF MIDDLE TO UPPER CAMBRIAN CARBONATES, BONANZA KING FORMATION, SOUTHERN GREAT BASIN
The Bonanza King Formation forms imposing mountainside exposures in several tilted fault block ranges in the southern Great Basin of Nevada and eastern California (Fig. 1). The shallow-marine carbonates that characterize the Bonanza King were deposited during the early drift phase of development of the Cordilleran passive margin, which originated in response to breakup of a Late Proterozoic supercontinent around 600 to 550 Ma (Stewart and Suczek, 1977; Bond and others, 1984; Levy and Christie-Blick, 1991). The broad continental margin was oriented essentially east-west within tropical latitudes (10 to 15° N; Scotese and McKerrow, 1990), conducive for the development of thick accumulations of carbonates.
LATERAL CONTINUITY OF MIDDLE CAMBRIAN PERITIDAL CYCLES, SOUTHERN NEVADA: IMPLICATIONS FOR THEIR ORIGIN
The origin and stratigraphic implications of meterscale peritidal cycles have been the source of heated debates, resulting in two schools of thought. One group favors the random, discontinuous, autocyclic accumulation of sediment in a localized area under constant subsidence as the controlling mechanism behind peritidal cycles (Ginsburg, 1971; Pratt and James, 1986; Waters and others, 1989; Cloyd and others, 1990). The other group proposes allocyclic mechanisms as the driver behind the deposition of rhythmic arrangements of lithofacies on carbonate platforms, preferably high-frequency, sea level fluctuations (Fischer, 1964; Grotzinger, 1986; Goldhammer and others, 1993; Koerschner and Read, 1989; Osleger and Read, 1991; Elrick, 1995).
TERTIARY SEDIMENTOLOGY AND DEPOSITIONAL HISTORY OF THE SANTA MONICA MOUNTAINS OF CALIFORNIA
This field conference emphasizes analysis of depositional processes and depositional environments for Tertiary sedimentary rocks in the Santa Monica Mountains of southern California. Figure 1 is a location map to field conference stops in the western Santa Monica Mountains. The last paper in this field conference guidebook volume is an article by Fritsche that summarizes the depositional processes from which sedimentary rocks originate. Rocks resulting from these processes that can be seen on this field conference are indicated by stop number and lithology within the appropriate sections of the Fritsche article.
STRATIGRAPHY AND SEDIMENTARY STRUCTURES OF THE PALEOGENE SUCCESSIONS IN THE WEST CENTRAL SANTA MONICA MOUNTAINS, LOS ANGELES COUNTY, CALIFORNIA
PRELIMINARY PETROGRAPHIC STUDY OF COARSE-GRAINED PALEOCENE SANDSTONES OF THE SOUTHERN TRANSVERSE AND NORTHERN PENINSULAR RANGES, CALIFORNIA
Exposures of non-marine and in places marine sandstone of the Paleocene Las Virgenes Sandstone occur in the Transverse Ranges. Stratigraphically equivalent non-marine and marine sandstones occur in the Paleocene Silverado Formation of the Peninsular Ranges (see Colburn, this volume, for location map). The Las Virgenes Sandstone is exposed in the Santa Monica Mountains, which border the northern side of the Los Angeles basin. The Silverado Formation is present in the Santa Ana Mountains and in the San Joaquin Hills, both of which border the southeastern portion of the basin. A petrographic analysis of the Las Virgenes and Silverado sandstones may yield clues concerning the origin of these two units presently exposed in distinct geomorphic provinces.
SEQUENCE STRATIGRAPHY ALONG A TECTONICALLY ACTIVE MARGIN, PALEOGENE OF SOUTHERN CALIFORNIA
This field trip emphasizes the relationships between worldwide sea-level change, tectonic elements, and sequence development for Eocene and Oligocene rocks in the San Diego embayment and Ventura Basin. Participants will be exposed to criteria for recognition of unconformities, systems tracts, and parasequences developed in submarine canyon, deltaic, tidal, shoreface and coastal plain environments. The stratigraphic signature of tectonics and eustasy will be a pervasive theme. The objectives of this field trip are threefold: 1) Develop fades models for sediments deposited in fluvial, tidal, deltaic, shoreface, shelf, and deep-water environments; 2) Evaluate evidence for facies changes versus unconformable relationships in interpreting sedimentary sequences; and 3) Demonstrate the application of sequence-stratigraphy principles to tectonically active basins with complex stratigraphic relationships. In addition observations from wells, aerial photographs, and outcrops will be integrated in the Transverse Ranges to develop paleogeographic reconstruc tions of the basin and evaluate the influence of structural evolution on sequence development.
STRUCTURE AND HYDROCARBON EXPLORATION IN THE TRANSPRESSIVE BASINS OF SOUTHERN CALIFORNIA
This field trip is an overview and reappraisal of the prolific oil basins of southern California (Fig. 1A) using exploration methods now commonly used in international exploration. As a result of the dramatic decline in oil and gas exploration in California during the last decade these mature and well known basins have received limited modern hydrocarbon research and it is hoped that our field trip and guidebook will outline some of the important aspects and questions of these intriguing petroleum systems. We have used balanced cross sections and other types of structural analyses integrated with basin modeling, geochemical and geophysical data to gain new insights into the structure, trapping mechanisms, and petroleum systems (Magoon and Dow, 1994) in a setting combining strike-slip and convergence (transpression). Southern California geology also has the scientific advantage, but societal disadvantage, of earthquakes (Fig. IB) which provide useful data about the deeper structure which will be presented during the trip. Our field examples are in the eastern Ventura basin, Ridge Basin, southern San Joaquin basin, Cuyama basin and western Ventura basin as well as a transect of the western Transverse Ranges (Fig. 1A).
EARLY MIOCENE CRUSTAL EXTENSION AND BASIN DEVELOPMENT: CENTRAL MOJAVE DESERT, SOUTHERN CALIFORNIA
The Mojave Desert region of southern California is geologically defined as the wedge-shaped area bounded to the north by the Garlock fault, and to the south by the San Andreas fault (Fig. 1). The east boundary is less easily defined and is arbitrarily placed along the Colorado River. Geographically, the region centers around the town of Barstow and the Tertiary geologic elements that are the focus of this field trip lie within a 60 km radius of Barstow.
ABSTRACT The Salton Trough region of southern California records Neogene deformation and sedimentation related to both the classic San Andreas strike-slip system and Mesozoic compression and convergent margin magmatism. Besides these Mesozoic and late Tertiary tectonic features, an intervening deformational, sedimentalogical, and magmatic episode of crustal extension has profoundly affected the region. This extensional deformation is part of a much larger region of crustal extension across much of western North America, including the regions now called highly extended terranes. The Salton Trough originally opened as a half graben basin within this extensional terrane and contained multiple detachment faults within the array of domino and listric faults that offset the region west of eastern New Mexico, east of the Rio Grande Rift. This stacked array of extensional faults collectively extended the crust, offsetting Mesozoic fabrics such as the Santa Rosa Mylonite zone and the Chocolate Mountains thrust. Faults developed during this segmentation of Mesozoic features have often been mistakenly identified as faults of Mesozoic age. Crustal attenuation and weaknesses created during regional detachment faulting appears to have localized the presence of many of the major faults within the San Andreas transform system. Strike-slip motion on these younger faults has translated the extensional terrane laterally, but has not disrupted much of the terrane except in position. The extensional terrane provides some key piercing points that can be used to help constrain motion on the San Andreas system, both in the Salton Trough and to the west in the California Continental Borderlands. The rigid beam of the Peninsular ranges appears to have acted as a boat between highly extended terranes in the current Salton Trough region and the Borderlands. Detachment faults just offshore in coastal California are thought to mimic the geometries and timing of detachment faults exposed along the margins of the Salton Trough.
Abstract Gneissic and granitic rocks sit structurally above the Mesozoic Orocopia Schist in the Orocopia and Chocolate Mountains of southeastern California (fig. 1). The gneissic and granitic units were originally emplaced above the schist along a Late Mesozoic thrust as is generally believed. In the Orocopias, the east-dipping system of faults that currently juxtapose the units, however, is a major system of anastamosing normal faults, which records a continuum of deformation from ductile mylonitic textures to brittle fault gouge. The middle to upper-crustal deformation by large-scale extension is a continuation of the highly extended terrane along the Colorado River and that to the west in the California Continental Borderlands. This crustal extension in the Orocopia-Chocolate Mountains region helped localize the San Andreas fault system and is itself offset along the San Andreas to numerous exposures west of the main strand of the San Andreas, including many oil-bearing basins.
In coastal southern California, west of the principal strand of the San Andreas fault system, structural features formed since the Cretaceous have primarily been attributed to transform motion along the San Andreas fault system (Fig. 1). Where extensional deformation is clearly present in coastal southern California, it has generally been attributed to wrench faulting associated with strike-slip motion of the San Andreas fault system (e.g., Wilcox and others, 1973; Crowell, 1974). Strike-slip versus extensional models for the evolution of coastal southern California had previously been discussed but widely dismissed in favor of transform tectonics by most workers. The continued refinement of the plate configurations for the Cenozoic and the re-evaluation of some of the structural features in coastal southern California suggest that there was indeed a distinct Miocene extensional event. This deformation occurred contemporaneously with the extensional events of the Colorado River region and other portions of the Basin-and-Range province of the western United States and Mexico. Recently, however, the presence of regional detachment fault systems have been verified by regional seismic reflection profiles processed by the U.S.G.S.
The Salton Trough was formed by the late Cenozoic interaction of three major geologic systems: the Gulf of California, Colorado River, and San Andreas fault (Fig. 1). On this field trip we will examine the stratigraphic record of these three systems as exposed in the western Salton Trough. Each day will be spent in one of the three localities ~ Split Mountain, Fish Creek Basin, and Coyote Mountains ~ that provide the best leverage on chronology, facies, and paleogeography of the early Salton Trough. Although the Salton Trough is not a significantly petroliferous basin, we will also examine sedimentary geometries, lateral variability, and reservoir-seal relationships as they might pertain to exploration and production in analogous basin settings.