Organic geochemical changes in Pliocene sediments of ODP Site 1083 (Benguela Upwelling System)

Pancost, Richard D., Boot, Christopher S., Aloisi, Giovanni, Maslin, Mark, Bickers, Claire, Ettwein, Virginia, Bale, Nicole and Handley, Luke (2009) Organic geochemical changes in Pliocene sediments of ODP Site 1083 (Benguela Upwelling System) Palaeogeography, Palaeoclimatology, Palaeoecology, 280 (1-2). pp. 119-131. DOI 10.1016/j.palaeo.2009.06.006.

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Abstract

The intensification of the Northern Hemisphere Glaciation (INHG) was a major event in the development of the current climate state, and as one of the most productive regions in the world's oceans, the behaviour of the Benguela Upwelling System (BUS) following the INHG is of wide interest. To investigate post-INHG changes in productivity and organic matter accumulation, total organic carbon and biomarker accumulation rates were determined for sediments from COP Site 1083 and compared to alkenone-derived sea surface temperatures and nitrogen isotopic compositions. These data indicate that the interval between 2.6 and 2.4 Ma was characterized by dramatic changes in upwelling intensity and organic carbon export on the northern edge of the modern BUS. The upwelling is reflected by significant changes in alkenone-derived SST estimates between glacial and interglacial intervals, with a total variability of 16 degrees C. The studied interval is also characterized by large changes in organic matter export as reflected by changes in TOC and biomarker accumulation rates, which show maxima during OIS 98 and during the transition from OIS 97 to 96. Intervals of elevated TOC are also characterized by elevated concentrations of sedimentary microbial biomarkers and lower %CaCO(3), suggesting that enhanced delivery of labile organic matter to the seafloor resulted in enhanced remineralisation with released CO(2) being consumed by CaCO(3) dissolution. However, in apparent contrast to recent Pleistocene sediments at the same site, organic matter export after the INHG was not solely driven by upwelling intensity. Of the three Pliocene glacial-interglacial cycles examined (OIS 101 to 96). each is unique with respect to the timing and magnitude of changes in organic matter accumulation. Each is also characterized by different algal assemblages as inferred from biomarker distributions, with OIS 97 and 96 particularly dominated by diatoms. We suggest that these differences reflect the important but evolving role of Southern Ocean waters in the Pliocene BUS: nutrient depletion of SO waters occurred during parts of Pliocene glacial intervals such that even intense upwelling did not persistently result in enhanced organic matter accumulation rates. (C) 2009 Elsevier B.V. All rights reserved.

Document Type: Article
Keywords: Meeresgeologie; Maleimides; Sterols; Archaeol; Nitrogen Isotopes; Northern Hemisphere Glaciation; Benguela Upwelling System; MATUYAMA DIATOM MAXIMUM; LONG-CHAIN ALKENONES; MARINE-SEDIMENTS; CALCITE DISSOLUTION; SURFACE SEDIMENTS; GEPHYROCAPSA-OCEANICA; NITRATE UTILIZATION; NEOGENE ; SEDIMENTS; EMILIANIA-HUXLEYI; SINKING PARTICLES
Research affiliation: OceanRep > GEOMAR > FB2 Marine Biogeochemistry > FB2-MG Marine Geosystems
Refereed: Yes
DOI etc.: 10.1016/j.palaeo.2009.06.006
ISSN: 0031-0182
Projects: ODP
Date Deposited: 10 Jan 2012 09:46
Last Modified: 23 Jan 2017 13:31
URI: http://eprints.uni-kiel.de/id/eprint/13343

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