Graduate Thesis Or Dissertation
 

Cenozoic biogenic silica sedimentation in the Antarctic Ocean, based on two deep sea drilling project sites

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  • The Antarctic Ocean during the Cenozoic experienced four periods of increased surface productivity: the Middle Eocene; the beginning of the Miocene; the Middle Miocene; and near the Miocene-Pliocene boundary. The fourth increase in productivity began five million years ago and has since progressively increased to the present level of intense surface productivity. The major control of Antarctic surface productivity is climate. Opal production in the Neogene increased during glacial times, due to the intensification of upwelling south of the Polar Front, caused from accelerated atmospheric circulation and an increased volume production of Antarctic Bottom Water. Cenozoic variations in surface productivity are also related to the tectonic changes in the Antarctic Ocean basin, which altered the patterns of surface and thermohaline circulation. Antarctic Surface Waters became more conducive to biological productivity with the progressive latitudinal and thermal isolation of Antarctica, The efficiency of surface productivity has progressed to such an extent that much of the global silica supply has been transferred to the Antarctic at the expense of other productive oceanic regions such as the Central Equatorial Pacific. In the Neogene, the preservation or dissolution of calcium carbonate is influenced by the rate of upwelling south of the Polar Front. During glacial times, the upwelling of COB_rich Circumpolar Deep Water accelerates and effectively raises the calcite compensation depth.
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