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NARROW
GeoRef Subject
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all geography including DSDP/ODP Sites and Legs
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Middle Valley (1)
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ODP Site 858 (1)
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Pacific Ocean
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East Pacific
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East Pacific Rise (1)
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Northeast Pacific
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Gorda Rise (1)
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Gulf of California
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Guaymas Basin (1)
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Juan de Fuca Ridge (1)
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North Pacific
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Northeast Pacific
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Gorda Rise (1)
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Gulf of California
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Guaymas Basin (1)
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Juan de Fuca Ridge (1)
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commodities
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metal ores (1)
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elements, isotopes
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isotope ratios (1)
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isotopes
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stable isotopes
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O-18/O-16 (1)
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metals
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rare earths (1)
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oxygen
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minerals
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Primary terms
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stable isotopes
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metal ores (1)
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metals
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rare earths (1)
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Ocean Drilling Program
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Leg 139 (1)
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Leg 169
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ODP Site 1035 (1)
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ODP Site 1036 (1)
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ODP Site 856 (1)
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oxygen
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O-18/O-16 (1)
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Pacific Ocean
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East Pacific
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East Pacific Rise (1)
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Northeast Pacific
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Gorda Rise (1)
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Gulf of California
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Guaymas Basin (1)
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Juan de Fuca Ridge (1)
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North Pacific
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Northeast Pacific
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Gorda Rise (1)
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Gulf of California
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Guaymas Basin (1)
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Juan de Fuca Ridge (1)
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sea water (1)
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Evolution of the Miocene-Recent Woodlark Rift Basin, SW Pacific, inferred from sediments drilled during Ocean Drilling Program Leg 180
Abstract The results of drilling during Ocean Drilling Program Leg 180 provide insights into fundamental processes of continental break-up, because rifting can be related to westward propagation of a spreading centre into continental crust. A generally north–south transect of holes was drilled across the Woodlark Rift on the uplifted northern rift margin on the Moresby Seamount (Sites 1114 and 1116), on the hanging wall of the low-angle (25–30°) extensional Moresby Detachment Fault (Sites 1108, 1110–1113 and 1117) and across the downflexed northern rift margin (Sites 1118, 1109 and 1115). The results, when placed in the regional tectonic context, document a history of Palaeogene ophiolite emplacement, followed by Miocene arc-related sedimentation. Regional uplift and emergence of the forearc area took place in Late Miocene time. Submergence to form the Woodlark Rift began in latest Miocene time, marked by widespread marine transgression and shallow-water deposition, accompanied by input of air-fall tephra and volcaniclastic sediments. During Pliocene time, deposition within the rift basin was dominated by deep-water turbidites, including high-density turbidites in the south. Strong extension along the north-dipping Moresby Detachment Fault was active during Pleistocene time, associated with uplift of the Moresby Seamount and shedding of fault-derived talus, mainly of meta-ophiolitic origin. During Pleistocene time, a carbonate platform was constructed to the NW, trapping clastic sediment and resulting in a switch to slower, more pelagic and hemipelagic deposition within the Woodlark Rift Basin. The marked change in rift basin configuration during Pleistocene time may relate to westward propagation of the Woodlark oceanic spreading centre at c. 2 Ma.
Abstract Five fallout tephra layers and 13 heterolithological volcaniclastic deposits drilled at Holes 1115A, 1115B, 1115C, 1109C, 1109D and 1118A, during Leg 180 on the downflexed northern margin of the western Woodlark Basin, have been dated by singlecrystal laser 40 Ar/ 39 Ar analyses. The fallout tephra layers range in age from 0.135 ± 0.008 Ma to 2.84 ± 0.03 Ma. Sedimentation ages determined for the volcaniclastic deposits range from 1.75 ± 0.29 Ma to 3.79 ± 0.01 Ma, closely matching the nannofossil, planktonic foraminifer and palaeomagnetic chronostratigraphies of the holes. However, two volcaniclastic deposits from 516.91m below seafloor (mbsf) and 632.5 mbsf in Hole 1118A are significantly older than indicated by biostratigraphic and palaeomagnetic data, probably because of the presence of older reworked volcanic crystals. The youngest ash layer is derived from explosive eruptions in the Dawson Strait area of the D’Entrecasteaux Islands, whereas the four older tephra layers are attributed to explosive eruptions in the Moresby Strait area of the D’Entrecasteaux Islands. The 40 Ar/ 39 Ar ages of volcaniclastic sand layers in Holes 1115C and 1118A indicate a transition from a shallow-water succession (<150m) to a deeper-water succession (150–500 m) with rapid deposition of volcaniclastic sands, mainly by turbiditic currents, at 3.8 Ma. This transition is related to the subsidence of the margin during rifting of the Woodlark Basin. Two volcaniclastic deposits with ages of 13.84 ± 0.02 Ma and 14.04 ± 0.03 Ma, respectively, provide important time markers in the middle Miocene sedimentary sequence at Hole 1115C, where biostratigraphic ages are scarce. Our 40 Ar/ 39 Ar ages represent the first marine record of Miocene to Pleistocene volcanism in the area of eastern Papua.