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Aging of marine organic matter during cross-shelf lateral transport in the Benguela upwelling system revealed by compound-specific radiocarbon dating

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dc.contributor.author Mollenhauer, Gesine
dc.contributor.author Inthorn, Maik
dc.contributor.author Vogt, Thomas
dc.contributor.author Zabel, Matthias
dc.contributor.author Sinninghe Damste, Jaap S.
dc.contributor.author Eglinton, Timothy I.
dc.date.accessioned 2010-04-19T20:08:42Z
dc.date.available 2010-04-19T20:08:42Z
dc.date.issued 2007-09-18
dc.identifier.citation Geochemistry Geophysics Geosystems 8 (2007): Q09004 en_US
dc.identifier.uri http://hdl.handle.net/1912/3256
dc.description Author Posting. © American Geophysical Union, 2007. 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 8 (2007): Q09004, doi:10.1029/2007GC001603. en_US
dc.description.abstract Organic matter accumulation and burial on the Namibian shelf and upper slope are spatially heterogeneous and strongly controlled by lateral transport in subsurface nepheloid layers. Much of the material deposited in depo-centers on the slope ultimately derives from the shelf. Supply of organic matter from the shelf involves selective transport of organic matter. We studied these selective transport processes by analyzing the radiocarbon content of co-occurring sediment fractions. Here we present radiocarbon data for total organic carbon as well as three tracers of surface ocean productivity (phytoplankton-derived alkenones, membrane lipids of pelagic crenarchaeota (crenarchaeol), and calcareous microfossils of planktic foraminifera) in core-top and near-surface sediment samples. The samples were collected on the Namibian margin along a shelf-slope transect (85 to 1040 m) at 24°S and from the upper slope depo-center at 25.5°S. In core-top sediments, alkenone ages gradually increased from modern to 3490 radiocarbon years with distance from shore and with water depth. Crenarchaeol, while younger than alkenones, also increased in age with distance offshore. It was concluded that the observed ages were a consequence of cross-shelf transport and associated aging of organic matter. Radiocarbon ages of preserved lipid biomarkers in sediments thus at least partially depend on the relative amount of laterally supplied, pre-aged material present in a sample, highlighting the importance of nepheloid transport for the sedimentation of organic matter over the Namibian margin. en_US
dc.description.sponsorship This work was funded by NSF grant OCE- 0327405 to T.I.E. and by a Spinoza grant to J.S.S.D. from NWO. en_US
dc.format.mimetype application/pdf
dc.language.iso en_US en_US
dc.publisher American Geophysical Union en_US
dc.relation.uri http://dx.doi.org/10.1029/2007GC001603
dc.subject Compound-specific radiocarbon dating en_US
dc.subject Sediment transport en_US
dc.title Aging of marine organic matter during cross-shelf lateral transport in the Benguela upwelling system revealed by compound-specific radiocarbon dating en_US
dc.type Article en_US
dc.identifier.doi 10.1029/2007GC001603


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