细菌细胞膜脂记录的西太平洋暖池约4 Ma以来沉积物风尘陆源输入变化

西菲律宾海作为西太平洋暖池的一部分,重建其在地质历史时期的热力学变化、陆源输入变化,对于理解西太平洋暖池在全球地质时间尺度上的作用具有重要意义。利用古菌与细菌的细胞膜质甘油二烷基甘油四醚(glycerol dialkyl glycerol tetraethers,GDGTs)对西菲律宾海XT-47孔沉积物的陆源输入及其上方水体温度的变化进行重建,发现该沉积柱顶部(0~260 cm,约16.6~18.8 ka)BIT指标为0.01~0.2,TEX^H 86重建的上层海水平均温度为22.5℃,而底部(260~632 cm,约18.8~4000 ka)TEX^H 86重建得到的上层海水温度绝对值波动剧烈(0.6~26℃),在此范围内BIT>0.3,并呈现逐渐增加的趋势,超过BIT界定的陆源输入对TEX^H 86重建古温度有效性的阈值,这导致了该深度范围内TEX^H 86重建古温度变化的严重偏差。以260和470 cm为界,该沉积柱的沉积相出现明显变化,上层为大量纹层硅藻席沉积,中层为远洋黏土和硅藻泥互层,下层为远洋黏土沉积;同时,支链GDGTs(branched GDGTs,br GDGTs)的组成也出现明显差异,说明其来源可能有所不同。基于以上分析,提出260 cm以浅,brGDGTs可能主要为海相原位自生为主;而260 cm深度以下,主要以风尘输送的陆源brGDGTs为主。该结果显示陆源输入的变化可以间接反映东亚冬季风的强弱,本研究为高低纬之间的海陆相互作用研究提供了新的视角。

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^H 86 is 22.5°C.The absolute sea surface temperature at the bottom layer from 260 cm to 632 cm,(18.8~4000 ka)reconstructed by TEX^H 86 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^H 86 defined by terrestrial input proxy-BIT,which leads to a serious deviation of the TEX^H 86 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.