High-resolution Sedimentary Record Of East Asian Monsoon From The Inner Shelf Mud Area Of East China Sea During Late Holocene

The inner shelf mud belt are gradually developed since the Holocene high sea level stand,characterized by high sedimentation rates,good continuity of sedimentary deposits,and have saved abundant environmental information.In this paper,we systematically analyzed the grain size and geochemistry of core MZ05 obtained from the southern part of the East China Sea inner shelf mud area,based on that we reconstructed a high-resolution sedimentary sequence and restoring the evolution history of the East Asian monsoon since the late Holocene.The lithologic characteristics and grain size composition of core MZ05 indicate that the vertical sedimentary phase distribution can be roughly divided into 3 types:coastal sedimentary deposits,transitional sedimentary deposits,and shallow sea sedimentary deposits.A comprehensive study was conducted only in the upper 20m of core MZ05,the AMS¹⁴C dating data revealed that the upper 20m of core MZ05 was formed between 2.90ka B.P.and 1.80ka B.P.Considering the seasonal changes in the direction of currents,rainfall intensity,and the effect of the sediments transported by the Yangtze River on the East China Sea inner shelf mud belt,based on environmentally sensitive grain's content and mean grain size to reflect the intensity of winter coastal current,and the evolution history of the East Asian winter monsoon;the Chemical Index of Alteration?CIA?,Rb/Sr ratio,and SiO₂/Al₂O₃ ratio of the sediment were selected to reflect the chemical weathering intensity in the source area,which restored the evolution history of the East Asian summer monsoon.The reconstruction of the ancient monsoon history indicates that the East Asian winter monsoon in the eastern china during 2.90ka B.P.-1.80ka B.P.can be roughly divided into 3 stages:the strong period of 2.90ka B.P.-2.60ka B.P.,the fluctuation period of 2.60ka B.P.-2.37ka B.P.and the weak period of 2.37ka B.P.-1.80ka B.P.The East Asian summer monsoon can also be divided into 3 stages,which are fluctuation and strong period of 2.90ka B.P.-2.60ka B.P.,fluctuation period of2.60ka B.P.-2.16ka B.P.,and relatively weak period of 2.16ka B.P.-1.80ka B.P..The evolution of winter and summer monsoons in East Asia since the late Holocene has a certain correlation,but there are differences in the extent and duration of the intensity changes,which means that they are not simply reciprocal relations,but also have their own independence and particularity.In addition,the similar monsoon evolution can be found in the South Yellow Sea climate record,Jinchuan peat climate record,and the Lianhua stalagmite?¹⁸O value record.This evidence reveals the good response of large-scale environmental and climate changes in the continental shelf of the East China Sea.