Constraints on the origin of sedimentary organic carbon in the Beaufort Sea from coupled molecular 13C and 14C measurements

摘要: Abstract The type and flux of organic carbon (OC) delivered from the continents to sea can both influence, be influenced by, climate change on regional global scales. In order develop a more complete view OC delivery in climatically sensitive Arctic region, we measured stable radiocarbon isotopic signatures individual lipid biomarkers products kerogen pyrolysis surficial sediments several sites Mackenzie Shelf adjacent slope Beaufort Sea. Even numbered fatty acids exhibit trend increasing 14C age with chain length, modern values for nC14–nC18 homologues thousand years old those ≥ nC24. Such depleted longer-chain likely reflect supply vascular plant that has been pre-aged millennia prior Their corresponding δ13C support C3 land source. molecular distributions 13C solvent-extractable alkanes point at least two sources: higher leaf waxes 14C-‘dead’ component derived erosion organic-rich sedimentary rocks exposed within River drainage basin. Δ14C n-hydrocarbon demineralized also suggest mixed ancient plant-derived precursors On bulk level, contents, C/N ratios, an overall decrease terrigenous input (mainly River) distance offshore, whereas measurements no suggesting somewhat constant component. A coupled mass balance approach based is used construct budget terrestrial, marine, petrogenic burial shelf. Results indicate roughly 40–50% currently being buried Sea weathering rock. composed marine terrestrial input, supporting qualitative description sources given by patterns above. This suggests balances utilizing as endmembers semi-quantitatively deconvolve multiple sediments.