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  • 1985-1989  (14)
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  • 1
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    Seabeam and seismic reflection imaging of the tectonic regime of the Andean continental margin off Peru (4°S to 10°S) (1988)
    Elsevier
    In:  Earth and Planetary Science Letters, 87 (1-2). pp. 111-126.
    Details
    Publication Date: 2017-11-08
    Description: Marine geophysical surveys employing Seabeam, multi- and single-channel seismic reflection, gravity and magnetic instruments were conducted at two locations along the continental slope of the Peru Trench during the Seaperc cruise of the R/V “Jean Charcot” in July 1986. These areas are centered around 5°30′S and 9°30′S off the coastal towns of Paita and Chimbote respectively. These data indicate that (1) the continental slope off Peru consists of three distinct morpho-structural domains (from west to east are the lower, middle and upper slopes) instead of just two as previously reported; (2) the middle slope has the characteristics of a zone of tectonic collapse at the front of a gently flexured upper slope; (3) the upper half of the lower slope appears to represent the product of mass wasting; (4) thrusting at the foot of the margin produces a continuous morphologic feature representing a deformation front where the products of mass-wasting are overprinted by a compressional tectonic fabric; (5) a change in the tectonic regime from tensional to compressional occurs at the mid-slope-lower slope boundary, the accretionary prism being restricted to the very base of the lower slope in the Paita area. The Andean margin off Peru is an “extensional active margin” or a “collapsing active margin” developing a subordinated accretionary complex induced by massive collapse of the middle slope area.
    Type: Article , PeerReviewed
    Format: text
    DOI: 10.1016/0012-821X(88)90068-4
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    OceanRep: Article in a Scientific Journal - peer-reviewed
  • 2
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    Convergent Tectonics and Coastal Upwelling: A History of the Peru Continental Margin (1987)
    International Union of Geological Sciences
    In:  Episodes: Journal of International Geoscience, 10 (2). pp. 87-93.
    Details
    Publication Date: 2016-10-07
    Description: The geological evolution of the western margin of South America has long been a challenge to geologists interested in convergent plate tectonics. Late in 1986, scientists on the ODP drillship JOIDES Resolution confirmed that the upper slope of the Peruvian margin consists of continental crust whereas the lower slope comprises an accretionary complex. An intricate history of horizontal and vertical movements can be detected, and the locations of ancient centers of upwelling appear to have varied, partly due to tectonic movements of the margin. In this review of Leg 112, the three scientific leaders on this cruise discuss their results.
    Type: Article , PeerReviewed
    Format: text
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    OceanRep: Article in a Scientific Journal - peer-reviewed
  • 3
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    Migrated Multichannel Seismic-Reflection Records across the Peru Continental Margin (1988)
    National Science Foundation
    In:  Initial Reports of The Deep Sea Drilling Project, 112 . pp. 109-124.
    Details
    Publication Date: 2020-07-28
    Description: We examined multichannel seismic records CDP-1, CDP-2, CDP-3, 1017, and records obtained during the site survey for Leg 112 to evaluate stratigraphy, tectonic evolution, and the structural character of the active margin offshore of Peru. From the reprocessed records we learned that the regionally uniform structure of the margin between 4°S and 14°S is modified by local tectonism. Common elements are crust of continental affinity beneath the middle and upper slope and an accretionary complex below the lower slope. The forearc basins have a varied tectonic history, which led to considerable differences in subsidence history and deformational style. Compressional tectonics dominate the front of the margin, whereas extension accounts for deformation landward of the midslope area.
    Type: Article , PeerReviewed
    Format: text
    DOI: 10.2973/odp.proc.ir.112.107.1988
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    OceanRep: Article in a Scientific Journal - peer-reviewed
  • 4
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    Jean Charcot Seabeam Survey along ODP Leg 112 Northern Transect (1988)
    National Science Foundation
    In:  Initial Reports of The Deep Sea Drilling Project, 112 . pp. 131-137.
    Details
    Publication Date: 2020-07-29
    Description: A marine geophysical survey that used Seabeam, multi- and single-channel seismic reflection, gravity, and magnetic profiling was conducted in two locations along the landward slope of the Peru Trench. This survey was conducted during the SeaPERC cruise of the Jean Charcot in July 1986 (Bourgois et al., 1986a; Bourgois et al., 1986b; Bourgois et al., 1987; Bourgois et al., in press). These areas were two possible drilling locations for ODP Leg 112, which was scheduled to begin in November 1986. The drilling transects center around latitudes of 5°30'S and 9°30'S, along multichannel seismic lines CDP-3 and CDP-2, respectively. The northern transect is located in the Paita Zone (Fig. 1, Box 2), and the southern transect is in the Chimbote Zone (Fig. 1, Box 6). During Leg 112, we drilled two sites (683 and 685) in the Chimbote area. This became the northern transect of Leg 112. Here, we report the Seabeam data acquired during the SeaPERC cruise. Drilling results from Sites 683 and 685, the CDP-2 multichannel seismic record, and the Seabeam data provide a threedimensional view of this region.
    Type: Article , PeerReviewed
    Format: text
    DOI: 10.2973/odp.proc.ir.112.109.1988
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    OceanRep: Article in a Scientific Journal - peer-reviewed
  • 5
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    Geology and petroleum potential of the Shumagin Margin, Alaska (1987)
    Circum-Pacific Council for Energy and Mineral Resources
    In:  In: Geology and Resource Potential of the Western North America and Adjacent Ocean Basins: Beaufort Sea to Baja California. Earth Science Series, 6 . Circum-Pacific Council for Energy and Mineral Resources, Houston, Texas, pp. 157-189.
    Details
    Publication Date: 2015-08-03
    Type: Book chapter , NonPeerReviewed
    Format: text
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    OceanRep: Book chapter
  • 6
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    A large tsunamogenic landslide and debris flow along the Peru Trench (1989)
    AGU (American Geophysical Union)
    In:  Journal of Geophysical Research: Solid Earth, 94 (B2). pp. 1703-1714.
    Details
    Publication Date: 2019-05-13
    Description: Along the continental margin of northern Peru, Sea Beam bathymetry and seismic reflection records reveal features from mass wasting in the middle and lower slope areas. A curved scarp cuts the middle slope and marks a slip surface seaward of which a 20 by 33 km block was displaced 800 m and back rotated 5° as it moved downslope. The front of that block is itself marked by a 1‐km‐high curved scar where the block failed and created a ∼30‐km debris flow avalanche. The avalanche morphology of closed highs and lows without directional fabric covers the lower slope and trench axis seaward of the detached block. If the slip was catastrophic, a local ∼50‐m‐high tsunami was generated. This example documents the type of slope failure commonly inferred as a source of destructive tsunamis. Since the block was detached along faults that displace beds 3–5 km deep, it represents more than a superficial slide where sediment was locally oversteepened. The detached block includes rocks that were part of the continental margin since at least Eocene time in front of which a 15‐km‐wide accretionary complex subsequently developed. Apparently, only low levels of horizontal compression could be transmitted into the upper plate because of weak coupling across the Benioff zone. This may have permitted detachment and mass movement of the block despite the long history of plate convergence here. Tsunamogenic slides and mass wasting at trench depths are difficult to detect without modern high‐resolution techniques.
    Type: Article , PeerReviewed
    Format: text
    DOI: 10.1029/JB094iB02p01703
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    OceanRep: Article in a Scientific Journal - peer-reviewed
  • 7
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    Structure of the frontal part of the Andean Convergent Margin (1985)
    AGU (American Geophysical Union)
    In:  Journal of Geophysical Research: Solid Earth, 90 (B7). pp. 5429-5442.
    Details
    Publication Date: 2019-05-14
    Description: A multichannel seismic reflection record across the central Peru margin and trench was improved by processing 24 rather than the 12 channels previously processed and by thorough migrating to reject the strong diffractions that obscured weaker primary reflections. The increased resolution clarifies the structure of the 15‐km‐wide frontal accretionary complex and the adjacent truncated continental framework against which the trench sediment was imbricated. Resolved are individual thrust slices and packets adjacent to the trench axis, subducting sediment‐filled graben in the ocean crust beneath the lower slope, and a Tertiary stratigraphic section of the upper slope Yaquina Basin which is cut by normal faults. The resolution in this multichannel record provides criteria for reinterpreting single‐channel data off Chile with increased confidence. The previously proposed truncation of the South American continent along much of the Peru‐Chile Trench is confirmed and the development of an accretionary complex in front of the truncated continental crust appears to vary with the amount of sediment seen in the trench axis. The Andean margin frontal structure is similar to that off Central America, the Aleutian Trench, and the Japan Trench which suggests common truncation as well as accretion at the front of convergent margins.
    Type: Article , PeerReviewed
    Format: text
    DOI: 10.1029/JB090iB07p05429
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    OceanRep: Article in a Scientific Journal - peer-reviewed
  • 8
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    Tectonic erosion at the front of the Japan Trench convergent margin (1989)
    Elsevier
    In:  Tectonophysics, 160 (1-4). pp. 75-90.
    Details
    Publication Date: 2019-05-13
    Description: The imaging of a multichannel seismic record was improved by reprocessing using pre-stack techniques. The reprocessed record shows structures that indicate tectonic erosion and gravity collapse at the front of the Japan Trench margin. Much of the lower slope appears to be underlain by a detached, coherent block of continental crust. The lower slope has failed by mass wasting and the resulting apron of slump debris at the base of the slope has become involved in thrust faulting at the front of the subduction zone. Slumping continues as long as debris is removed from the front of the margin by subduction, and the apron cannot build up sufficiently to stabilize the failing lower slope. Truncated beds at the base of the upper plate indicate subcrustal erosion as well, this probably being the main cause of massive subsidence of the margin. Subsidence was the cause of oversteepening, destabilization and subsequent gravity collapse of the leading edge of the upper plate.
    Type: Article , PeerReviewed
    Format: text
    DOI: 10.1016/0040-1951(89)90385-5
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  • 9
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    Ocean Drilling Program Leg 112, Peru continental margin: Part 2, Sedimentary history and diagenesis in a coastal upwelling environment (1988)
    GSA, Geological Society of America
    In:  Geology, 16 (10). pp. 939-943.
    Details
    Publication Date: 2019-05-13
    Description: On the shelf and upper slope off Peru the signal of coastal upwelling productivity and bottom-water oxygen is well preserved in alternately laminated and bioturbated diatomaceous Quaternary sediments. Global sea-level fluctuations are the ultimate cause for these cyclic facies changes. During late Miocene time, coastal upwelling was about 100 km west of the present centers, along the edge of an emergent structure that subsequently subsided to form the modern slope. The sediments are rich in organic carbon, and intense microbially mediated decomposition of organic matter is evident in sulfate reduction and methanogenesis. These processes are accompanied by the formation of diagenetic carbonates, mostly Ca-rich dolomites and Mg-calcites. The downhole isotopic signatures of these carbonate cements display distinct successions that reflect the vertical evolution of the pore fluid environment. From the association of methane gas hydrates, burial depth, and low-chloride interstitial fluids, we suggest an additional process that could contribute to the characteristic chloride depletion in pore fluids of active margins: release of interlayer water from clays without a mineral phase change. The shelf sediments also contain a subsurface brine that stretches for more than 500 km from north to south over the area drilled. The source of the brine remains uncertain, although the composition of the oxygen isotopes suggests dissolution of evaporites by seawater.
    Type: Article , PeerReviewed
    Format: text
    DOI: 10.1130/0091-7613(1988)016〈0939:ODPLPC〉2.3.CO;2
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    OceanRep: Article in a Scientific Journal - peer-reviewed
  • 10
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    Annotated record of the detailed examination of Mn deposits from DSDP Leg 84 (Holes 565 and 568) (1985)
    PANGAEA
    Details
    Publication Date: 2023-08-28
    Description: The Middle America Trench was first drilled in 1979 during Leg 66 off Oaxaca, Mexico and Leg 67 off Guatemala as part of a broad effort to study the mechanics of plate subduction and continental accretion and erosion. Leg 84 was recommended by the JOIDES Advisory Panels specifically to further examine the tectonic and gas-hydrate problems which had been revealed in the previous survey.
    Keywords: 84-565; 84-568; Comment; Deep Sea Drilling Project; Deposit type; DEPTH, sediment/rock; Description; DRILL; Drilling/drill rig; DSDP; Event label; Glomar Challenger; Identification; Leg84; NOAA and MMS Marine Minerals Geochemical Database; NOAA-MMS; North Pacific/SLOPE; North Pacific/TRENCH; Position; Quantity of deposit; Sample code/label; Sediment type; Visual description
    Type: Dataset
    Format: text/tab-separated-values, 32 data points
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    DATA PANGAEA
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