Reconstruction of terrestrial input changes in sediments in the Western Pacific warm pool using bacterial membrane lipids

The West Philippine Sea is a part of the Western Pacific Warm Pool. To reconstruct its thermodynamic changes and terrestrial input changes in the geological history is of great significance for understanding the role of the Warm Pool on a global geological time scale. In this paper, the glycerol dialkyl glycerol tetraethers (GDGTs) of archaea and bacteria is used to reconstruct the temperature and terrestrial input proxy changes for the core XT-47 taking from the West Philippine Sea. The BIT index on top layer of 0～260 cm, corresponding to 16.6～18.8 ka, varies between 0.01～0.2, and the average sea surface temperature reconstructed with TEX^H₈₆ is 22.5°C. The absolute sea surface temperature at the bottom layer from 260 cm to 632 cm, (18.8～4 000 ka) reconstructed by TEX^H₈₆ fluctuates drastically between 0.6°C and 26°C; BIT＞0.3 within these depth range, shows a gradual increase trend, exceeding the threshold for the validity of paleotemperature reconstruction of TEX^H₈₆ defined by terrestrial input proxy-BIT, which leads to a serious deviation of the TEX^H₈₆ reconstructed paleotemperature within this depth range. Taking 260 cm and 400 cm as boundaries, the sedimentary facies of the core has changed significantly. In a descending order, the upper layer is a large number of laminar diatom mats, the middle layer is interbedded pelagic clay and diatom clay, and the lower layer is pelagic clay deposit; simultaneously, obvious differences in the composition of branched GDGTs (brGDGTs) are observed, indicating that their sources may also be different. Based on the above analysis, we propose that brGDGTs below 260 cm are marine in-situ autochthonous deposits; while that below 260 cm, terrigenous brGDGTs dominate, which are mainly transported as aeolian dust. The results suggest that the changes in terrestrial input can indirectly reflect the strength of the East Asian winter monsoon, and the results may provide new insights for the study of sea-land interactions between high and low latitudes.