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Lookup NU author(s): Professor Thomas Wagner, Dr Helen Talbot
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Normal 0 false false false DE JA X-NONE We have investigated the delivery of terrestrial organic carbon (OC) to the Amazon shelf and deep sea fan based on soil-marker bacteriohopanepolyols (BHPs; adenosylhopane and related compounds) and branched glycerol dialkyl glycerol tetraethers (GDGTs), as well as of 14C dating of bulk organic matter. The microbial biomarker records show persistent burial of terrestrial OC, evidenced by almost constant and high BIT values (0.6) and soil-marker BHP concentration [80-230 µg/g TOC (total organic carbon)] on the late Holocene shelf and even higher BIT values (0.8-0.9), but lower and more variable soil-marker BHP concentration (40-100 µg/g TOC) on the past glacial deep sea fan. Radiocarbon data show that OC on the shelf is 3-4 kyr older than corresponding bivalve shells, emphasizing the presence of old carbon in this setting. We observe comparable and unexpectedly invariant BHP compositions in both marine sediment records, with a remarkably high relative abundance of C-35 amino-BHPs including compounds specific for aerobic methane oxidation on the shelf (avg. 50% of all BHPs) and the fan (avg. 40%). Notably, these marine BHP signatures are strikingly similar to those measured from a methane-producing floodplain area in one of the Amazonian wetland (várzea) regions. This observation indicates that BHPs measured in the marine sediments may have initially been produced within wetland regions of the Amazon basin and therefore document persistent export from terrestrial wetland regions with subsequent re-working in the marine environment, both during recent and past glacial climate conditions.
Author(s): Wagner T, Kallweit W, Talbot HM, Mollenhauer G, Boom A, Zabel M
Publication type: Article
Publication status: Published
Journal: Organic Geochemistry
Year: 2014
Volume: 67
Pages: 85-98
Print publication date: 15/12/2013
ISSN (print): 0146-6380
ISSN (electronic): 1873-5290
Publisher: Elsevier Ltd.
URL: http://dx.doi.org/10.1016/j.orggeochem.2013.12.003
DOI: 10.1016/j.orggeochem.2013.12.003
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