Organic Geochemistry | 2019
Vertical distribution of isoprenoid GDGTs in suspended particles from the East China Sea shelf and implications for sedimentary TEX86H records
Abstract
Abstract The T E X 86 H (or TEX86) paleothermometer has been widely applied for reconstructing water temperature in marine settings, particularly in marginal seas which often archive paleoclimate records with high temporal resolution. Yet debate remains regarding the water depth at which the T E X 86 H signal is imparted in these settings. In this study, East China Sea (ECS) surface sediments and suspended particulate matter (SPM) from different water depths (0–60\u202fm) were analyzed for lipid biomarkers to better constrain the depth to which the sedimentary T E X 86 H signal corresponds. Our data showed divergent vertical distributions between archaeal lipids and phytoplankton lipids. The maximum concentration of core lipid isoprenoid glycerol dialkyl glycerol tetraethers (core iGDGTs) appeared in bottom waters (2–5\u202fm above the sea floor) at all sites, whereas phytoplankton lipids showed highest abundance in surface waters (0\u202fm). Consistent with the maximum core iGDGTs concentration in bottom waters, the best correlation was observed between SPM T E X 86 H values and 2–4\u202fweeks averaged water temperatures from the bottom waters. Moreover, the SPM core iGDGTs content was higher in bottom waters than in surface sediments, implying that in situ production rather than sediment resuspension leads to the maximum concentration of core iGDGTs in bottom waters. By compiling published surface sediment data from water depths T E X 86 H with bottom water temperature (BWT) exceeds that with sea surface temperature (SST). Therefore, it is proposed that sedimentary T E X 86 H is a BWT proxy in the shallow ECS.