Impact of water depth on the distribution of iGDGTs in the surface sediments from the northern South China Sea: applicability of TEX86 in marginal seas
The TEX 86 H paleothermometer on the base of isoprenoid glycerol dialkyl glycerol tetraethers (iGDGTs) has been widely applied to various marine settings to reconstruct past sea surface temperatures (SSTs). However, it remains uncertain how well this proxy reconstructs SSTs in marginal seas. In this study, we analyze the environmental factors governing distribution of iGDGTs in surface sediments to assess the applicability of TEX 86 H paleothermometer in the South China Sea (SCS). Individual iGDGT concentrations increase gradually eastwards. Redundancy analysis based on the relative abundance of an individual iGDGT compound and environmental parameters suggests that water depth is the most influential factor to the distribution of iGDGTs, because thaumarchaeota communities are water-depth dependent. Interestingly, the SST difference (ΔT) between TEX 86 H derived temperature and remote-sensing SST is less than 1°C in sediments with water depth>200 m, indicating that TEX 86 H was the robust proxy to trace the paleo-SST in the region if water depth is greater than 200 m.
KeywordsiGDGTs distribution South China Sea (SCS) sea surface temperature water depth
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We thank each member of the organic geochemistry group in the State Key Laboratory of Biogeology and Environmental Geology for technical support. We also thank Y. Qin, X. Chen and L. Gong from China University of Geosciences for help with data processing. We also thank Changbing Yang and Angelo R. Yang from The University of Texas in Austin for the language polishing. The research was funded by the National Natural Science Foundation of China (Grant No. 41376090), the “Strategic Priority Research Program” of the Chinese Academy of Sciences (XDA11020102), The Project of China Geological Survey (DD20160138), and Marine Safeguard Project (GZH201200503).
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