The Characteristics And Provenances Of Sediments In The Inner Shelf Of The East China Sea:Constrains On The Index Of Paleoenvironment Since 4.7ka

Sediments from the inner shelf of the East China Sea?ECS?with its high deposition and continuously sedimentary record which is sensitive to enviromental change is a important recorder of regional responses to global paleoclimatic and paleoenvironmental changes.Based on the precise AMS¹⁴C dating data,We analyze grain size,clay minerals and trace elements of S05-3 sediment cores,investigating the sediment provenances of the southern part of the inner shelf of East China Sea,deducing the evolution of East Asia Monsoon in the past 4.7ka.Comparing clay minerals of S05-3 sediment cores in the southern part of the inner shelf of East China Sea with clay minerals from different potential source areas,the results indicate that sediments in the study area came from the Yangtze River,the Yellow River and rivers from Taiwan,while every potential source area making different contribution in the different historical sediment periods.In the period of4.7-4.2ka,sediments from the Yantze River and Taiwan's river is the main source of sediments of the southern part of the inner shelf of East China Sea.From 4.2ka to3.2ka,sediments of study area mainly consists of the sediments of the Yanze River and the Yellow River.Since 3.2ka,sendiments from all of potential source areas had some affect on the study area.The evolution of East Asia Monsoon in the past 4.7ka can be deduced based on the grain size sensitive components,the ration of Rb/Sr and montm orillonite/kaolinite.Refering to the?¹⁸O of GSP2 and stalagmite of Dongge Cave and the evidence of cooling of different materials in other regions,9 high values could be recognized corresponding to the cooling events caused by the East Asia Monsoon,which are4600a BP?C1?,4200a BP?C2?,3650a BP?C3?,2800a BP?C4?,2300a BP?C5?,1900a BP?C6?,1000a BP?C7?,500a BP?C8?,300a BP?C9?.The core S05-3 records 4strengthen periods of the East Asia Monsoon:weak and stable during 4.7-4.2ka BP;increased and began to fluctuate during 4.2-3.2ka;a little weak with highly fluctuation during 3.2-2.0ka BP;the East Asia Monsoon incresed slighly with fluctuations weakened.