Aging of marine organic matter during cross-shelf lateral transport in the Benguela upwelling system revealed by compound-specific radiocarbon dating
Sinninghe Damste, Jaap S.
Eglinton, Timothy I.
MetadataShow full item record
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.
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.
Suggested CitationGeochemistry Geophysics Geosystems 8 (2007): Q09004
Showing items related by title, author, creator and subject.
Direct application of compound-specific radiocarbon analysis of leaf waxes to establish lacustrine sediment chronology Uchikawa, Joji; Popp, Brian N.; Schoonmaker, Jane E.; Xu, Li (2006-12-18)This study demonstrates use of compound-specific radiocarbon analysis (CSRA) for dating Holocene lacustrine sediments from carbonate-hosted Ordy Pond, Oahu, Hawaii. Long-chain odd-numbered normal alkanes (n-alkanes), ...
Compound-specific radiocarbon dating of the varved Holocene sedimentary record of Saanich Inlet, Canada Smittenberg, R. H.; Hopmans, Ellen C.; Schouten, Stefan; Hayes, John M.; Eglinton, Timothy I.; Sinninghe Damste, Jaap S. (American Geophysical Union, 2004-05-01)The radiocarbon contents of various biomarkers extracted from the varve-counted sediments of Saanich Inlet, Canada, were determined to assess their applicability for dating purposes. Calibrated ages obtained from the marine ...
Timescales of lateral sediment transport in the Panama Basin as revealed by radiocarbon ages of alkenones, total organic carbon and foraminifera Kusch, Stephanie; Eglinton, Timothy I.; Mix, Alan C.; Mollenhauer, Gesine (2009-12)Paired radiocarbon measurements on haptophyte biomarkers (alkenones) and on cooccurring tests of planktic foraminifera (Neogloboquadrina dutertrei and Globogerinoides sacculifer) from late glacial to Holocene sediments ...