984 resultados para 61-1


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The Kamchatka Peninsula of northeastern Russia is located along the northwestern margin of the Bering Sea and consists of zones of complexly deformed accreted terranes. Along the northern portion of the peninsula, progressing from then orthwestem Bering Sea inland the Olyutorskiy, Ukelayat, and Koryak superterranes area acreted to the Okhotsk-Chukotsk volcanic-plutonic bell in northern-most Kamchatka. A sedimentary sequence of Albian to Maastrichtian age overlap terranes and units of the Koryak superterrane and constrains their accretion time with this region of the North America plate. Ophiolite complexes, widespread within the Koryak superterrane, are associated with serpentinite melanges and some of the ophiolite terranes include large portions of weakly serpentinized hyperbasites, layered gabbro, sheeted dikes, and pillow basalts outcropping as internally coherent blocks within a sheared melange matrix. Interpretation of magnetic anomalies allow the correlation of the Ukelayat with the West Kamchatka and Sredinny Range superterranes. The Olyutorskiy composite terrane may be correlated with the central and southern Kamchatka Peninsula Litke, Eastern Ranges and Vetlov composite terranes. The most "out-board" of the central and southern Kamchatka Peninsula terranes is the Kronotsky composite terrane, weil exposed along the Kamchatka, Kronotsky and Shipunsky Capes. Using regional geological constraints, paleomagnetism, and plate kinematic models for the Pacific basin a regional model can be proposed in which accretion of the Koryak composite terrane to the North America plate occurs during the Campanian-Maastrichtian, followed by the accretion of the Olyutorskiy composite terrane in the Middle Eocene, and the Late Oligocene-Early Miocene collision of the Kronotsky composite terrane. A revised age estimate of a key overlapping sedirnentary sequence of the Koryak superterrane, calibrated with new Ar40/Ar39 data, supports its Late Cretaceous accretion age.

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Leg 61 of the Deep Sea Drilling Project (DSDP) was concerned with drilling a single continuously cored multiple re-entry hole at site 462 in the Central Nauru Basin (Fig. 1). Preliminary results of this drilling, which penetrated more than 1 km beneath the sea floor, were presented earlier. One major result was the discovery of a late Cretaceous off-ridge volcanic/intrusive complex of basaltic composition and great thickness (>500 m). We now present trace element abundance data for these basalts. Results of the drilling provide further support for a relatively long-lived thermal and magmatic event in the late Cretaceous resulting in voluminous and widespread magmatism in the central and western Pacific consistent with earlier suggestions. The trace element data show that most of the rocks produced during this event have trace element characteristics intermediate between those of normal and transitional mid-ocean ridge basalts (N- and T-type MORB) and different from Hawaiian basalts. These results indicate that basalts which are depleted in light rare earth elements (LREE) relative to the heavy REE may, in certain conditions, be erupted as voluminous intra-plate eruptions far from active ridge crests.

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Data on zooplankton abundance and biovolume were collected in concert with data on the biophysical environment at 9 stations in the North Atlantic, from the Iceland Basin in the East to the Labrador Sea in the West. The data were sampled along vertical profiles by a Laser Optical Plankton Counter (LOPC, Rolls Royce Canada Ltd.) that was mounted on a carousel water sampler together with a Conductivity-Temperature-Depth sensor (CTD, SBE19plusV2, Seabird Electronics, Inc., USA) and a fluorescence sensor (F, ECO Puck chlorophyll a fluorometer, WET Labs Inc., USA). Based on the LOPC data, abundance (individuals/m**3) and biovolume (mm3/m**3) were calculated as described in the LOPC Software Operation Manual [(Anonymous, 2006), http://www.brooke-ocean.com/index.html]. LOPC data were regrouped into 49 size groups of equal log10(body volume) increments, see Edvardsen et al. (2002, doi:10.3354/meps227205). LOPC data quality was checked as described in Basedow et al. (2013, doi:10.1016/j.pocean.2012.10.005). Fluorescence was roughly converted into chlorophyll based on filtered chlorophyll values obtained from station 10 in the Labrador Sea. Due to the low number of filtered samples that was used for the conversion the resulting chlorophyll values should be considered with care. CTD data were screened for erroneous (out of range) values and then averaged to the same frequency as the LOPC data (2 Hz). All data were processed using especially developed scripts in the python programming language. The LOPC is an optical instrument designed to count and measure particles (0.1 to 30 mm equivalent spherical diameter) in the water column, see Herman et al., (2004, doi:10.1093/plankt/fbh095). The size of particles as equivalent spherical diameter (ESD) was computed as described in the manual (Anonymous, 2006), and in more detail in Checkley et al. (2008, doi:10.4319/lo.2008.53.5_part_2.2123) and Gaardsted et al. (2010, doi:10.1111/j.1365-2419.2010.00558.x).

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Seven quartered sections of Pliocene to Mesozoic (Cenomanian) cores from the Nauru Basin contain primarily marine organic matter admixed with detectable amounts of terrigenous organic matter. The mixture is immature with respect to organic genesis. Chemical properties of this organic matter are compared with properties of other deep-ocean cores from DSDP sites in the central Pacific.