Sources and distribution of isoprenoid glycerol dialkyl glycerol tetraethers (GDGTs) in sediments from the east coastal sea of China: Application of GDGT-based paleothermometry to a shallow marginal sea

To shed more light on the applicability of glycerol dialkyl glycerol tetraether (GDGT) based proxies for reconstructing environmental change in shallow marginal seas, we analyzed the GDGT composition of surface sediments from the east coastal sea of China (ECSC). The GDGT distribution in 58 surface sediment samples from the ECSC shows that the isoprenoid GDGTs (iGDGTs) are mainly from autochthonous planktonic Thaumarchaeota and that the relative abundance of the acyclic GDGT (GDGT-0) in the ECSC increases with latitude, whereas that of cyclic GDGTs decreases. The fractional abundances of iGDGTs correlated significantly with annual and seasonal sea surface temperature (SST), especially with summer SST. Based on this, we propose a new calibration of the TEX86H proxy to reconstruct past SST in the ECSC. The new calibration shows a higher calibration coefficient (R2 0.84, p < 0.001), leading to a more robust reconstruction of temperature in China marginal seas. The 90 yr SST record derived with the new calibration for a sediment core from the ECSC is consistent with climate data from NOAA, demonstrating the applicability of the new calibration for summer SST reconstruction in this shallow marginal sea