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The distribution of metalliferous sediments adjacent to active spreading centers is of both scientific and economic interest. Metal-rich waters emanating from active hydrothermal vents have been traced in intermediate level water masses far beyond the ridge crest, but the greatest concentrations of metal oxides in sediments occur near the vents. There, however, it is possible that the oxides may be redistributed and possibly further concentrated by redeposition. We document one such case of redeposition for Messinian sediments cored at Deep Sea Drilling Project Site 599, which, along with the other DSDP Leg 92 sites, was the first on the East Pacific Rise to be drilled using the hydraulic piston corer.
Site 599 (19°27.09^primeS, 119°52.88^primeW; water depth = 3,654 m), drilled in a small basin about 600 km from the present ridge crest, recovered 41 m of mostly Miocene calcareous oozes characterized by alternating light (mostly yellowish brown to dark yellowish brown) and dark (mostly dark reddish brown) zones from 10 to 100 cm thick and/or bands 2-5 cm thick. A sharp contact at sample point 599-3-3, 21 cm, separates fine-grained light-colored in-situ sediments of calcareous nannofossil Zone CN9b below from a coarser grained and darker metalliferous-rich unit above, which contains older nannofossils derived from Zone CN8b. Indicative of downslope transport of metalliferous materials during the Messininan, this example may explain much of the sediment banding seen throughou the section.
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