Wind-driven upwelling in the ocean around Antarctica helps regulate the exchange of carbon dioxide (CO2) between the deep sea and the atmosphere, as well as the supply of dissolved silicon to the euphotic zone of the Southern Ocean. Diatom productivity south of the Antarctic Polar Front and the subsequent burial of biogenic opal in underlying sediments are limited by this silicon supply. We show that opal burial rates, and thus upwelling, were enhanced during the termination of the last ice age in each sector of the Southern Ocean.
View Article and Find Full Text PDFThree records of oxygen isotopes in biogenic silica from deep-sea sediment cores from the Atlantic and Indian sectors of the Southern Ocean reveal the presence of isotopically depleted diatomaceous opal in sediment from the last glacial maximum. This depletion is attributed to the presence of lids of meltwater that mixed with surface water along certain trajectories in the Southern Ocean. An increase in the drainage from Antarctica or extensive northward transport of icebergs are among the main mechanisms that could have produced the increase in meltwater input to the glacial Southern Ocean.
View Article and Find Full Text PDFMore than 50 cores ranging in age from Pliocene to Lower Miocene have been recovered from the East Pacific Rise. Near the crestal regions the sediment cover is thin or lacking, and only Pleistocene sediments were recovered. On the flanks, the sediment thickness increases and pre-Pleistocene sediments are encountered.
View Article and Find Full Text PDFMinute bodies (less than 80 microns) of isotropic silica, originally precipitated by terrestrial plants, are found together with freshwater diatoms in falls of dust over the ocean. Eolian transport from Africa can explain the occurrence of similar plant remains in deep-sea sediments of the equatorial Atlantic as far west as the Mid-Atlantic Ridge.
View Article and Find Full Text PDFCores recovered from horizon A are Late Cretaceous (Maestrichtian) in age and consist o alternating layers of calcareous turbidites and "red clay." The presence of red clay suggests that the water depth in this area during Cretaceous time was at least as great as at present-more than 5100 meters. A middle Cretaceous (Cenomanian) core consisting of interbedded sand and gravel and light-to-dark-gray lutite was taken in the same area from a layer stratigraphically below the horizon; the presence of hydrogen sulfide and iron sulfide may indicate anaerobic conditions that may be attributable to local ponding of sediment in Cenomanian time.
View Article and Find Full Text PDFThe first occurrence of deep-sea Lower Cretaceous (Albian) sediments in the Pacific Ocean is reported from the Shatsky Rise at 31 degrees 51'N, 157 degrees 20'E. Seismic-profile records indicate that the core was taken between the extensive seismic reflectors A and B. Two hundred meters of unconsolidated sediment lies between the core site and basement (B) and suiggests that the sediment just above basement may be at least as old as Middle Jurassic.
View Article and Find Full Text PDFLower Miocene microfossils occur in basaltic glass in two dredge hauls from the crestal area of the Mid-Atlantic Ridge near 30 degrees N. From the ridge and adjoining abyssal hills 43 pre-Pleistocene cores were identified, including one Cretaceous and four Eocene. Dredgings and cores now available suggest that the upper layer of the crust of the ridge is constructed of layers of interbedded sediments and basalt flows.
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