Glycerol dialkyl glycerol tetraethers signature in sediments of the East China Sea and its implication on marine and continental climate and environment records

摘要

Glycerol dialkyl glycerol tetraethers (GDGTs) were determined in surface sediments from the East China Sea (ECS) in order to evaluate their potential for palaeo-climate and environmental reconstructions. Isoprenoid GDGTs (isoGDGTs) ranged from 516.75 ng/g to 1365 ng/g and crenarchaeol (cren) and caldarchaeol (GDGT-0) were the main components. IsoGDGTs were mainly derived from marine planktonic Thaumarchaeota. Branched GDGTs (brGDGTs) ranged from 12.3 ng/g to 123.5 ng/g and were dominated by GDGT-I and GDGT-II. The fractions and distributions, combined with branched/isoprenoid tetraether index (BIT) and methylation and cyclization indexes of brGDGT (MBT-CBT) suggested that brGDGTs in the ECS were mainly derived from terrestrial soils and they could be used to reconstruct climates. The TEX86-derived sea surface temperatures (SST) were close to the satellite-derived SST in autumn. The MBT/CBT-derived mean annual air temperatures (MAATs) and CBT-derived pH values in inner shelf by local and global calibrations matched well with the measured MAATs and soil pH in the lower Changjiang River basin, which seem to be appropriate for palaeo-climate and environment reconstructions of the continent around the ECS. Besides, cren and methane index showed a sensitive response to dissolved oxygen variation, suggesting their potential as palaeo-redox proxy.