Central California Margin Research Articles

Reconstructing the Evolution of the Submarine Monterey Canyon System From Os, Nd, and Pb Isotopes in Hydrogenetic Fe‐Mn Crusts

AbstractThe sources of terrestrial material delivered to the California margin over the past 7 Myr were assessed using 187Os/188Os, Nd, and Pb isotopes in hydrogenetic ferromanganese crusts from three seamounts along the central and southern California margin. From 6.8 to 4.5 (±0.5) Ma, all three isotope systems show more radiogenic values at Davidson Seamount, located near the base of the Monterey Canyon System, than in Fe‐Mn crusts from the more remote Taney and Hoss Seamounts. At the Taney Seamounts, approximately 225 km farther offshore from Davidson Seamount, 187Os/188Os values, but not Pb and Nd isotope ratios, also deviate from the Cenozoic seawater curve toward more radiogenic values from 6.8 to 4.5 (±0.5) Ma. However, none of the isotope systems in Fe‐Mn crusts deviate from seawater at Hoss Seamount located approximately 450 km to the south. The regional gradients in isotope ratios indicate that substantial input of dissolved and particulate terrestrial material into the Monterey Canyon System is responsible for the local deviations in the seawater Nd, Pb, and Os isotope compositions from 6.8 to 4.5 (±0.5) Ma. The isotope ratios recorded in Fe‐Mn crusts are consistent with a southern Sierra Nevada or western Basin and Range provenance of the terrestrial material which was delivered by rivers to the canyon. The exhumation of the modern Monterey Canyon must have begun between 10 and 6.8 ± 0.5 Ma, as indicated by our data, the age of incised strata, and paleo‐location of the Monterey Canyon relative to the paleo‐coastline.

Calibrating amino acid δ13C and δ15N offsets between polyp and protein skeleton to develop proteinaceous deep-sea corals as paleoceanographic archives

Compound-specific stable isotopes of amino acids (CSI-AA) from proteinaceous deep-sea coral skeletons have the potential to improve paleoreconstructions of plankton community composition, and our understanding of the trophic dynamics and biogeochemical cycling of sinking organic matter in the Ocean. However, the assumption that the molecular isotopic values preserved in protein skeletal material reflect those of the living coral polyps has never been directly investigated in proteinaceous deep-sea corals. We examined CSI-AA from three genera of proteinaceous deep-sea corals from three oceanographically distinct regions of the North Pacific: Primnoa from the Gulf of Alaska, Isidella from the Central California Margin, and Kulamanamana from the North Pacific Subtropical Gyre. We found minimal offsets in the δ13C values of both essential and non-essential AAs, and in the δ15N values of source AAs, between paired samples of polyp tissue and protein skeleton. Using an essential AA δ13C fingerprinting approach, we show that estimates of the relative contribution of eukaryotic microalgae and prokaryotic cyanobacteria to the sinking organic matter supporting deep-sea corals are the same when calculated from polyp tissue or recently deposited skeletal tissue. The δ15N values of trophic AAs in skeletal tissue, on the other hand, were consistently 3–4‰ lower than polyp tissue for all three genera. We hypothesize that this offset reflects a partitioning of nitrogen flux through isotopic branch points in the synthesis of polyp (fast turnover tissue) and skeleton (slow, unidirectional incorporation). This offset indicates an underestimation, albeit correctable, of approximately half a trophic position from gorgonin protein-based deep-sea coral skeleton. Together, our observations open the door for applying many of the rapidly evolving CSI-AA based tools developed for metabolically active tissues in modern systems to archival coral tissues in a paleoceanographic context.

Geomorphic process fingerprints in submarine canyons

Abstract Submarine canyons are common features of continental margins worldwide. They are conduits that funnel vast quantities of sediment from the continents to the deep sea. Though it is known that submarine canyons form primarily from erosion induced by submarine sediment flows, we currently lack quantitative, empirically based expressions that describe the morphology of submarine canyon networks. Multibeam bathymetry data along the entire passive US Atlantic margin (USAM) and along the active central California margin near Monterey Bay provide an opportunity to examine the fine-scale morphology of 171 slope-sourced canyons. Log–log regression analyses of canyon thalweg gradient ( S ) versus up-canyon catchment area ( A ) are used to examine linkages between morphological domains and the generation and evolution of submarine sediment flows. For example, canyon reaches of the upper continental slope are characterized by steep, linear and/or convex longitudinal profiles, whereas reaches farther down canyon have distinctly concave longitudinal profiles. The transition between these geomorphic domains is inferred to represent the downslope transformation of debris flows into erosive, canyon-flushing turbidity flows. Over geologic timescales this process appears to leave behind a predictable geomorphic fingerprint that is dependent on the catchment area of the canyon head. Catchment area, in turn, may be a proxy for the volume of sediment released during geomorphically significant failures along the upper continental slope. Focused studies of slope-sourced submarine canyons may provide new insights into the relationships between fine-scale canyon morphology and down-canyon changes in sediment flow dynamics.

Paleoceanographic changes on the Farallon Escarpment off central California during the last 16,000 years

New benthic and planktic foraminiferal assemblage census data and Benthic Foraminiferal Oxygen Index (BFOI) values, previously published marine climate proxy data (stable isotopes and Ca/Cd), and unpublished results of total carbon, organic carbon, and calcium carbonate analyses of sediments recovered off central California on the Farallon Escarpment (1605 m water depth; 37°13.4′N, 123°14.6′W; core F-8-90-G21) document paleoceanographic changes during the latest Quaternary which reflect the intensity and source of North Pacific Intermediate Water (NPIW) and surface productivity. Accelerator mass spectrometry radiocarbon dates of both benthic and planktic species provide an excellent age-depth model for the last 16,000 years, covering the latest glacial, Bølling–Allerød, Younger Dryas, and early, middle, and late Holocene intervals. A Q-mode cluster analysis separated the benthic fauna into three clusters, one Pleistocene and two Holocene, whereas the planktic fauna was divided only into Pleistocene and Holocene clusters. Stable oxygen isotope values show an increase in water temperature of ∼1 °C from the late glacial to late Holocene and a change in faunal composition of the planktic assemblage implies surface waters warmed as well. A general trend of decreasing dissolved oxygen concentration from the Pleistocene (high oxic; 3.0–6.0+ ml/l O 2) to the Holocene (low oxic; 1.5–3.0 ml/l O 2) suggested by the BFOI and Cd/Ca data reflect decreased ventilation as the source of the NPIW shifted from the Sea of Okhotsk to the tropical east Pacific at ∼11,000 cal BP. The middle Holocene cooling reported in other central and northern California margin studies is not apparent in F-8-90-G21, which compares more favorably with studies from southern California and British Columbia. Total carbon and organic carbon values are highest in the Bølling–Allerød, early Holocene, and late Holocene. Similarly, calcium carbonate values are high in the Bølling–Allerød and peak in the early Holocene, but decrease significantly in the latest middle and late Holocene which coincides with a depauparate planktic foraminiferal fauna in the upper 60 cm (∼70000–0 cal BP) of the core and poor preservation of the benthic foraminiferal fauna at 40 cm (∼3000 cal BP). Decoupling is evident between the planktic and benthic faunal response to changing climatic conditions, with the surface-dwelling assemblage often leading the bottom-dwelling assemblage by several millennia.

Fertile abyssal peridotites within the Franciscan subduction complex, central California: Possible origin as detached remnants of oceanic fracture zones located close to a slow-spreading ridge

This paper describes lherzolite and harzburgite within shale-matrix mélanges of the late Mesozoic Franciscan Complex at the western margin of central California. The Cr# ( = Cr/(Cr + Al) atomic ratio) of spinels in the lherzolite is extremely low (0.11 to 0.13), plotting at the low Cr# end of the abyssal peridotite field, although the moderate to high Cr# of spinels in the harzburgite leaves two possible origins as forearc or abyssal peridotite. The relationships between the Fo and NiO contents of olivines, plot along the mantle olivine array and indicate the residual character of the lherzolite. A high Mg# ( = Mg/(Mg + Fe 2+) atomic ratio) for clinopyroxenes is one of the characteristics of the lherzolite, reflecting low-temperature Mg–Fe redistribution with olivine beneath the ocean floor at around 700 °C. The rare earth element patterns of clinopyroxenes in sampled lherzolite show simple light rare earth element-depleted patterns with flat middle and heavy rare earth elements patterns, resembling those obtained for peridotites dredged from the Vulcan Fracture Zone at the American–Antarctica Ridge. This mineral chemistry, in combination with a lack of association with gabbros and sheet–dike complexes, implies that the lherzolite and harzburgite represent fertile abyssal peridotites along oceanic fracture zones near a slow-spreading ridge; the peridotites experienced a low degree of melting during their history. This origin is in contrast to that of the Coast Range ophiolite, the most extensive ophiolitic belt in California, which formed in a supra-subduction zone setting.

Diverse Origins of Xenoliths from Seamounts at the Continental Margin, Offshore Central California

A diverse assemblage of small mafic and ultramafic xenoliths occurs in alkalic lava from Davidson and Pioneer seamounts located at the continental margin of central California. Based on mineral compositions and textures, they form three groups: (1) mantle xenoliths of lherzolite, pyroxenite, and dunite with olivine of4Fo90; (2) ocean crust xenoliths of dunite with olivine 5Fo90, troctolite, pyroxenegabbro, and anorthosite with low-K2O plagioclase; (3) cumulates of seamount magmas of alkalic gabbro with primary amphibole and biotite and anorthosites with high-K2O plagioclase. The alkalic cumulates are genetically related to, but more evolved than, their host lavas and probably crystallized at the margins of magma reservoirs. Modeling and comparison with experimentally derived phases suggest an origin at moderate pressures ( 0 5^0 9 GPa).The high volatile contents of the alkalic host lavas may have pressurized the magma chambers and helped to propel the xenolith-bearing lavas directly from deep storage at the base of the lithosphere to the eruption site on the ocean floor, entraining fragments of the upper mantle and ocean crust cumulates from the underlyingabandoned spreadingcenter.

Preservation of particulate non-lithogenic uranium in marine sediments

Particulate non-lithogenic uranium (PNU), excess U above detrital background levels found in marine particulate matter, is formed in surface waters throughout the ocean. Previous studies have shown that PNU is regenerated completely prior to burial of particles in sediments within well-oxygenated open-ocean regions. However, the fate of PNU has never been examined in ocean margin regions or in anoxic basins. Here we evaluate the preservation of PNU in ocean margin sediments and within semi-enclosed basins using samples from sediment traps deployed at multiple depths and surface sediments. Organic carbon fluxes at the sediment trap locations ranged from 0.1 to 4.3 g/cm 2 kyr, while the dissolved oxygen concentration in the water column ranged from <3 μM to ∼ 270 μM. Preservation of PNU increases with decreasing dissolved oxygen concentration, approaching 100% preservation at oxygen concentration < 25 μM. PNU contributes as much as 40 to 70% of the total authigenic U in sediments in the Santa Barbara Basin and seasonally anoxic Saanich Inlet, and some 10% to 50% of the total authigenic U in sediments off the central California Margin.

Climatic and oceanographic variations on the California continental margin during the last 160 kyr

Organic matter in sediment samples from three ODP sites (Ocean Drilling Program Leg 167) that form a south-north transect was investigated to reconstruct the paleoclimatic and oceanographic conditions on the California continental margin during the last 160 kyr. Alkenone-derived paleosea surface temperatures (SST) are 3 to 6°C colder in glacial stages and reveal a clear relationship with global climate changes; the differences are greater in the north. Latitudinal SST comparison exhibits water mixing of the colder California Current with warmer waters from the south, particularly in the southern central California borderland area. Organic matter accumulation on the California continental margin indicates an interplay between climatic and atmospheric glacial–interglacial variations and spatially and temporally changing nutrient availability along the California coastline. Climatic and atmospheric dependent circulations apparently caused variations in the intensity of coastal upwelling along the southern central California margin and this suggests, due to the close connection of the California Current to the local wind patterns, that the California Current was weaker during glacial and stronger during interglacial periods.

Climatically related millennial-scale fluctuations in strength of California margin oxygen-minimum zone during the past 60 k.y.

A strong oxygen-minimum zone (OMZ) currently exists along the California margin because of a combination of high surface-water productivity and poor intermediate-water ventilation. However, the strength of this OMZ may have been sensitive to late Quaternary ocean-circulation and productivity changes along the margin. Although sediment-lamination strength has been used to trace ocean-oxygenation changes in the past, oxygen levels on the open margin are not sufficiently low for laminations to form. In these regions, benthic foraminifera are highly sensitive monitors of OMZ strength, and their fossil assemblages can be used to reconstruct past fluctuations. Benthic foraminiferal assemblages from Ocean Drilling Program Site 1017, off Point Conception, exhibit major and rapid faunal oscillations in response to late Quaternary millennial-scale climate change (Dansgaard-Oeschger cycles) on the open central California margin. These faunal oscillations can be correlated to and are apparently synchronous with those reported from Santa Barbara Basin. Together they represent major fluctuations in the strength of the OMZ which were intimately associated with global climate change--weakening, perhaps disappearing, during cool periods and strengthening during warm periods. These rapid, major OMZ strength fluctuations were apparently widespread on the Northeast Pacific margin and must have influenced the evolution of margin biota and altered biogeochemicalmore » cycles with potential feedbacks to global climate change.« less

OVERVIEW: Late Cenozoic tectonics of the central and southern Coast Ranges of California

The central and southern Coast Ranges of California coincide with the broad Pacific‐North American plate boundary. The ranges formed during the transform regime, but show little direct mechanical relation to strike-slip faulting. After late Miocene deformation, two recent generations of range building occurred: (1) folding and thrusting, beginning ca. 3.5 Ma and increasing at 0.4 Ma, and (2) subsequent late Quaternary uplift of the ranges. The ranges rose synchronously along the central California margin and are still rising; their long axes are quasiparallel to the plate boundary and strike-slip faults. The upper crustal internal and marginal structures of the ranges are contractional, dominated by folds and thrusts resulting from the convergent component of plate motion. Newly constructed transects using seismic reflection and refraction, plus gravity and magnetic studies, reveal lower crustal basement(s) at depths of 10‐22 km. The upper surface of the basement and Moho show no effect of the folding and thrusting observed in the upper crust. We conclude that horizontal shortening is accommodated at depth by slip on subhorizontal detachments, and by ductile shear and thickening. The ranges are marked by high heat flow; weak rocks of the Franciscan subduction complex; high fluid pressure; bounding high-angle reverse, strike-slip, or thrust faults; and uplift at a rate of 1 mm/yr beginning about 0.40 Ma. Transverse compression manifested in folding within the Coast Ranges is ascribed in large part to the well-established change in plate motions at about 3.5 Ma.

Biogenic sedimentation beneath the California Current System for the past 30 kyr and its paleoceanographic significance

A north‐south transect of 17 cores was constructed along the eastern boundary of the California Current system from 33° to 42°N to investigate the changes in biogenic sedimentation over the past 30 kyr. Percentages and mass accumulation rates of CaCO3, Corg, and biogenic opal were assembled at 500 to 1000 years/sample to provide relatively high resolution. Time‐space maps reveal a complex pattern of changes that do not follow a simple glacial‐interglacial two‐mode model. Biogenic sedimentation shows responses that are sometimes time‐transgressive and sometimes coeval, and most of the responses show more consistency within a limited geographic area than any temporal consistency. Reconstructed conditions during late oxygen isotope stage 3 were more like early Holocene conditions than any other time during the last 30 kyr. Coastal upwelling and productivity during oxygen isotope stage 3 were relatively strong along the central California margin but were weak along the northern California margin. Precipitation increased during the last glacial interval in the central California region, and the waters of the southern California margin had relatively low productivity. Productivity on the southern Oregon margin was relatively low at the beginning of the last glacial interval, but by about 20 ka, productivity in this area significantly increased. This change suggests that the center of the divergence of the West Wind Drift shifted south at this time. The end of the last glacial interval was characterized by increased productivity in the southern California margin and increased upwelling along the central California margin but upwelling remained weak along the northern California margin. A sudden (&lt;300 years) decrease in CaCO3, Corg, and biogenic opal occurred at 13 ka. The changes suggest a major reorientation of the atmospheric circulation in the North Pacific and western North America and the establishment of a strong seasonality in the central California region. A carbonate preservation event occurred at 10 ka that appears to reflect the uptake of CO2 by the terrestrial biosphere as the northern latitudes were reforested following retreat of the glaciers. The Holocene has been a period of relatively high productivity in the southern California margin, relatively strong coastal upwelling along the central California margin, relatively weak upwelling along the northern California margin, and the northward migration of the divergence zone of the West Wind Drift.

Map restoration of an early Pliocene horizon along the Hosgri-Purisima-Lompoc fault system, central California margin: ABSTRACT

The Hosgri fault is the southern part of the San Gregorio-Sur-San Simeon-Hosgri fault system, an important element of the Neogene California transform system. The Hosgri fault proper (top 1-2 km) is located in the hanging-wall of a 10 to 20 km wide zone of mostly E-dipping faults, the Hosgri-Purisima-Lompoc fault system. These faults have undergone Miocene extension, and have been reactivated by post-Miocene contraction or transpression. This wider fault system is truncated against or merges with the E-striking faults in northwestern Santa Barbara Channel. From this starting point of zero displacement, right-lateral displacement on a N- S fault can not be more than the sum of N-S shortening east of it, the N-S extension west of it, and the right-lateral slip fed into it by other faults. We are using a 3-D map restoration technique to quantify the displacements along this fault system. Depth-contoured folded surfaces are flattened using the software UNFOLD, and the restored surfaces are fit back together across faults using an interactive graphic program. Displacements are calculated by comparing the restored surface to the present state with respect to a relatively-fixed block. Our mapping of the early Pliocene top Sisquoc horizon indicates that broad, gentle folds characterizemore » the Point Arguello oil field. Folds located between Point Arguello and Point Sal, are characterized by abrupt changes in amplitude, symmetry, and vergence along strike. The folded surface is unfaulted over wide areas, despite dips up to 45[degrees]. These folds are the result of basin inversion along former rift border faults. Folds are amplified where the basin fill is transpressed against NW-striking restraining bends in a regional NNW-striking system of right-reverse-oblique faults.« less

Integrated crustal structure across the south central California Margin: Santa Lucia escarpment to the San Andreas Fault

The continental margin of south central California has undergone different styles of deformation over the past 30 m.y. as the North America‐Pacific plate boundary has evolved from subduction to transform tectonics. Results presented here identify strike‐slip and compressional structures in the lower crust that probably developed during this period of tectonic transition. An integrated model of crustal structure along deep seismic line PG&amp;E‐3 crosses the entire continental margin west of the San Andreas fault near the latitude of San Luis Obispo. A compressional wave velocity model was developed using coincident marine multi‐channel seismic and onshore/offshore wide‐angle reflection/refraction seismic data and was tested independently with gravity modeling. A high‐velocity layer (6.8–7.0 km/s, about 6 km thick) in the lower crust that extends east possibly as far as the San Andreas fault is interpreted as tectonically underplated oceanic crust. The upper and middle crust of the Patton and Sur‐Obispo Franciscan terranes extends to depths of 14 to 20 km. The velocity and density modeling indicate lower average velocities and densities for the Patton terrane, supporting earlier interpretations that it is a distinct terrane within the Franciscan complex. Abrupt crustal thickening associated with broken and downdropped oceanic crust beneath the Santa Lucia Escarpment probably results from active transform faulting that occurred along the continental slope from about 22 to 16 Ma following the subduction of the Pacific‐Arguello ridge. An imbrication within the oceanic crust centered beneath the coast is evidence for about 15 km of shortening within the oceanic crust. Convergence between the Monterey and Arguello microplates during the final stages of Farallon subduction (about 24 to 16 Ma) probably caused the imbrication.

Generation of the benthic foraminiferal assemblage: Theory and preliminary data

The production of benthic foraminiferal communities is filtered through taphonomic (mainly destructive) processes within the sediments to generate the fossil assemblage. Both the production and the taphonomy depend on bottom water oxygen content and flux of organic carbon to the seabed. An examination of the relationships of processes generating the fossil assemblage to oxygen and organic carbon supply is made using pore water geochemical measurements to estimate carbon flux for locations in the Gulf of Mexico and the central California margin. The locations are plotted in a three dimensional field with bottom water oxygen content, organic carbon flux, and sediment depth as the axes. Then the response of foraminiferal standing stock, taphonomic processes and the developing fossil assemblage to the field is investigated. Variation in the vertical stratification of foraminiferal standing stock and test production, species' stratification, taphonomic process intensity and stratification, and sediment bioturbation lead to marked differences in the way the fossil assemblage is generated across the oxygen content-organic carbon flux field. The result is that the oxygen-carbon flux field has a significant impact on the fossil assemblage through the interaction of biological and biogeochemical processes in the sediments. A model of this interaction is investigated to show how its elements change across the oxygen-carbon flux field and how these affect the generation of the fossil assemblage.

Thrusting of the central California margin over the edge of the Pacific plate during the transform regime

Wide-angle seismic reflection and refraction data, mapped geologic structures, and marine magnetic anomalies provide evidence that oceanic crust underlies the coastal margin of California from Morro Bay northward beyond San Francisco. We interpret the presence of this oceanic slab to be at least partly the result of thrusting of North America over the Pacific plate during Pliocene to Quaternary time, well after the principal subduction regime ended. Likely causes of this thrusting are the change in plate motions at about 3.5 Ma and extension in the Basin and Range province.

Shortening within underplated oceanic crust beneath the Central California Margin

Structures within a tectonically underplated layer of early Miocene age oceanic crust indicate that the lower crust of offshore central California has been deformed under compression prior to the inception of the San Andreas transform system along the continental margin. Shortening in the lower crust is inferred from the geometry of two structures, the Santa Lucia monocline and the Santa Maria antiform, delineated by an integrated interpretation of multichannel and wide‐angle seismic reflection data in conjunction with regional gravity data and teleseismic receiver functions. The 700 km of multichannel seismic data and 300 km of wide‐angle seismic data from the 1986 Pacific Gas and Electric/EDGE seismic experiment form the primary data base used to establish the northwesterly trend and extent of the monocline and the WNW trend of the antiform. In cross‐sectional view, the Santa Lucia monocline is a 30° kink in the oceanic crust, while the Santa Maria antiform is characterized by local thickening of the oceanic crust. These structures are probably the result of convergence between the Monterey and Arguello microplates that took place as subduction along the margin waned. The multichannel seismic reflection data image two Miocene age shelf basins, the Santa Lucia and offshore Santa Maria basins that formed within a transtensional stress regime. The offshore Santa Maria basin directly overlies the Santa Maria antiform, suggesting that either the upper and lower crustal stress regimes were completely decoupled in Miocene time or that the two features formed in different places. Differential slip between the upper crust and lower crust may have been accommodated along a detachment zone located above oceanic crust. Convergence within the oceanic crust and apparent differential motion between upper and lower crust are indicative of the processes that can affect the transition from subduction to an oceanic‐continental transform zone.

Carbon fluxes and burial rates over the continental slope and rise off central California with implications for the global carbon cycle

In situ microelectrode, box‐core pore water gradient, and in situ benthic chamber estimates of organic carbon degradation and CaCO3 dissolution are combined with organic‐C and carbonate‐C accumulation rates to approximate the total carbon flux to the seafloor along two transects of the continental slope and rise off central California. Microelectrode profiles of dissolved O2 demonstrate that sediments at 13 sites, ranging in water depth from 580 to 4080 m, become anoxic below the uppermost 0.4–3 cm of the sediment column. If a current‐swept area of nondeposition on the upper slope is excluded, we find total organic‐C and carbonate‐C fluxes to the seafloor vary from 40 to 100 μmol C cm−2yr−1 and from 32 to 91 μmol C cm−2yr−1, respectively. From the distribution of these fluxes there is no indication that total fluxes or remineralization rates of organic or carbonate carbon are influenced markedly by conditions in the oxygen minimum zone. Instead, the upper continental rise with its system of submarine valleys and fans stands out as the most important locus for carbon deposition and remineralization. When benthic fluxes and burial rates are extrapolated over the whole slope and rise of the region, aerobic respiration is the major mechanism of organic matter oxidation, and organic‐C and carbonate‐C recycling are on average 87% and 98% efficient, respectively. These results suggest that modern sediments on the outer regions of continental margins are important sources of CO2 that is injected directly into ocean deep water. However, if benthic carbon fluxes on the central California margin are typical of margins globally, this injection rate is less than 0.7 Gt C yr−1, which does not indicate a significant anthropogenic enhancement of carbon export to continental slopes and rises.

Introduction to Special Section on EDGE and Related Seismic Projects, Onshore‐Offshore California

The continental margins hold a special interest to Earth scientists because they mark the complex transition from oceanic to continental crust. This transition often involves a number of interacting processes, including subduction, accretion, and deformation of the oceanic lithosphere and growth and modification of the continental lithosphere, particularly the crust. The past decade has seen a great deal of progress in geophysical studies of continental margins, in large part due to the successful application of marine multi channel seismic (MCS) surveys that have provided unprecedented details on the deep structure.An opportunity arose in 1986 to augment, at a relatively modest cost, an MCS survey commissioned by the Pacific Gas and Electric Company (PG) across the central California margin. At the initiative of the Houston Area Research Center (HARC) and Rice University, funds were provided to the M CS contractor to record several additional MCS profries, and land seismographs were deployed to record the marine air gun shots and land shots prepared by the U.S. Geological Survey. Ocean bottom seismographs were deployed on two of the profiles by Oregon State University. This study constitutes the first of many profiles of opportunity completed or planned by EDGE, a National Science Foundation and industry funded consortium of institutions committed to geophysical studies of continental margins.

Interpretation of Continuous-Offset Seismic Data in Central California Margin: ABSTRACT

Interpretation of Continuous-Offset Seismic Data in Central California Margin: ABSTRACT

Deep Structure of Central California Margin from EDGE Seismic Profile RU-3: ABSTRACT

Deep Structure of Central California Margin from EDGE Seismic Profile RU-3: ABSTRACT