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dc.contributor.authorHoltvoeth, Jens  Concept link
dc.contributor.authorWagner, Thomas  Concept link
dc.contributor.authorSchubert, Carsten J.  Concept link
dc.date.accessioned2010-04-19T19:03:22Z
dc.date.available2010-04-19T19:03:22Z
dc.date.issued2003-12-31
dc.identifier.citationGeochemistry Geophysics Geosystems 4 (2003): 1109en_US
dc.identifier.urihttps://hdl.handle.net/1912/3251
dc.descriptionAuthor Posting. © American Geophysical Union 2003. This article is posted here by permission of American Geophysical Union for personal use, not for redistribution. The definitive version was published in Geochemistry Geophysics Geosystems 4 (2003): 1109, doi:10.1029/2003GC000590.en_US
dc.description.abstractLate Quaternary sections (1.2 Ma) of ODP-Site 1075 from the Congo deep-sea fan are investigated to reconstruct variations of terrigenous organic matter supply to the eastern equatorial Atlantic. To characterize the organic matter (OM) with regard to marine and terrigenous amounts we used elemental analysis (C, N, S), stable carbon isotopes (bulk δ13Corg), Rock-Eval pyrolysis, and terrigenous biomarkers (lignin phenols from CuO oxidation). The records of total organic carbon (TOC) contents, Corg/Ntot ratios, bulk OM degradation rates (Corg/Corg*), and the ratios of hydrocarbons (HC) from low-mature versus HC from high-mature OM (lm/hm) reveal pronounced cyclic changes in OM abundance, preservation, and reactivity that are closely related to the precessional controlled record of insolation, and thus, to variations in upwelling intensity and fluvial run-off. Primary productivity off the Congo is stimulated by both, enhanced nutrient supply in response to trade-induced upwelling during arid African climates (insolation minima) and fluvial nutrient delivery during humid stages (following insolation maxima), especially due to the contribution of dissolved silica that is taken up preferably by diatoms. However, results stemming from a multiparameter approach reveal that the fluvial supply of degraded OM and black carbon (BC) associated with fine-grained sediments from soil erosion is a decisive factor for the preservation of marine OM and, in addition, significantly influences the geochemical signature of bulk and terrigenous OM. Riverine and eolian supply of C4 plant matter, as well as enhanced concentrations of BC, during arid and arid-to-humid transitional climate stages, may lead to a severe underestimation of terrigenous organic carbon, if its amount is calculated from bulk isotopic ratios using binary end-member models. During the humid stages, it is the massive supply of 13C-enriched soil OM with low Corg/Ntot ratios that may suggest a mainly marine composition of bulk OM. In fact, terrigenous OM governs bulk OM geochemical signatures in the sediments of the Congo deep-sea fan, a result that is contradictory to earlier studies, especially to the conventional interpretation of the bulk δ13Corg signal.en_US
dc.description.sponsorshipThis research was funded by the Deutsche Forschungsgemeinschaft, grant Wa 1036/5, and kindly supported by the Max-Planck Society.en_US
dc.format.mimetypeapplication/pdf
dc.language.isoen_USen_US
dc.publisherAmerican Geophysical Unionen_US
dc.relation.urihttps://doi.org/10.1029/2003GC000590
dc.subjectCongo deep-sea fan
dc.subjectTerrestrial organic matter
dc.subjectLignin
dc.subjectOrganic matter reactivity
dc.subjectInsolation forcing
dc.subjectQuaternary tropical Atlantic
dc.titleOrganic matter in river-influenced continental margin sediments : the land-ocean and climate linkage at the Late Quaternary Congo fan (ODP Site 1075)en_US
dc.typeArticleen_US
dc.identifier.doi10.1029/2003GC000590


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