Grain Size End Member Characteristics and Paleoclimatic Significance of Loess Deposit in Shengshan Island during the Last Glacial Period
[Objective]The Upper Pleistocene eolian loess accumulation in islands of the East China Sea is an im-portant expansion for loess in China in the eastern Yangtze River delta and its extended sea area.The better study of the eolian loess provenance and its evolution in this region is particularly important for understanding regional paleoenvironmental changes.[Methods]Based on the analyses of optically stimulated luminescence(OSL)dating and magnetic susceptibility,parametric end-member analysis was used to clarify the grain size data for Shengshan Island loess and its paleoenvironmental effect.[Results and Conclusions]Three end-members(EM1-EM3)were identified:EM1 is the clay component transported by the westerly circulation;EM2 is the fine silt component trans-ported over long distances,suspended in the form of floating dust that was deposited when the wind force weakened;and EM3 is the coarse silt component carried by winter winds for short distances and deposited near the land surface.It was inferred from the analysis that EM1 and EM2 were the main sources of dust in the loess profile on Shengshan Island.Combined with the optically stimulated luminescence(OSL)results,the variations of frequency susceptibili-ty,median particle size,Rb/Sr values and the fluctuations of the end-members in the loess profile revealed that the Shengshan Island loess accumulated in marine isotope stage MIS2 experienced paleoclimatic fluctuations from warm and humid to cold and dry,and then to warm and humid in MIS3.The end-member properties also responded to the paleoenvironmental changes during the last glacial maximum and deglaciation period of the MIS2 stage.Climatic fluctuations recorded by the loess deposits also correspond to the trends of deep-sea oxygen isotopes and ancient sea-level changes.Thus the environmental evolution in the shelf areas of the East China Sea were closely related to global paleoclimatic variations.
end-member analysisShengshan Island loesslast glacial periodpaleoclimate changes
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