Evidence from authigenic uranium for increased productivity of the glacial Subantarctic Ocean

Publication Type  Journal Article
Year of Publication  2001
Authors  Chase, Z.; Anderson, R. F.; Fleisher, M. Q.
Journal Title  Paleoceanography
Volume  16
Issue  5
Pages  468-478
Journal Date  Oct
ISBN Number  0883-8305
Accession Number  ISI:000171072800003
Key Words  southern indian-ocean; antarctic ice core; north-atlantic; organic-carbon; deep-water; biological productivity; interglacial changes; marine-sediments; atmospheric co2; last glaciation
Abstract  

Authigenic uranium is precipitated in reducing sediments and therefore responds both to changes in particulate organic carbon flux to the sediment and to changes in the oxygen concentration of bottom waters. By examining a large number of cores over a wide latitudinal and depth range in the Atlantic sector of the Southern Ocean, we hope to distinguish between a predominantly productivity-driven authigenic U signal and a circulation or sediment-focusing signal. We find little to no authigenic U in Holocene sediments throughout the South Atlantic Ocean. Glacial sediments north of similar to 40 degreesS lack authigenic U, whereas sediments from the Subantarctic Zone show substantial enrichments in authigenic U relative to the Holocene (up to similar to5.3 ppm). The widespread distribution of glacial U enrichment, even in cores with no glacial-interglacial change in mass accumulation rate, implies that U deposition was not caused by an increased supply of organic carbon via sediment focusing. Authigenic U and organic carbon in a shallow core (similar to 1000 m) from the Subantarctic region show the same glacial increase found in the deep cores. Because this site was well ventilated during the Last Glacial Maximum, its record provides further evidence that increased glacial productivity of the Subantarctic region contributed to the high concentrations of authigenic U found in the glacial sections of deep cores.

Notes  

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