The Evolution Of East Asian Monsoon During 5.82?4.77kaBP Recorded By A High-Resolution Stalagmite ?¹⁸O From ShuiDong Cave, Liaoning Province

The holocene?Since about 11.5 ka B.P.?is experiencing inter-glacial periods of the earth.The holocene climate change is mild and smooth,compared to the previous ice age.Later people found that the holocene occur nine times rapidly climate changing events and their cycle is 1500 years.5.5 ka events occurred in the middle holocene,and its characteristic is dry and cold.Not only the occurring time are different in the different areas,different geological carriers of existing ancient climate records,but also its internal structure is unclear,and the stalagmite records instructing Asian monsoons are also differences.Therefore the climate reconstruction results are uncertain of middle-late holocene monsoon.It will directly affect the middle-late holocene monsoon changes to understanding of the characteristics and mechanism.So more high resolution records,especially the precise,the high resolution and the continuous growth of monsoon climate from typical monsoon region,can solve these problems.Northeast China area,locating the edge of the typical east Asian monsoon region.It affected by humidity air from the ocean in the summer and Siberian cold-dry airflow in the winter.As a result,the northeast region is the key to research the ancient climate.In this study,stalagmite TW704 in ShuiDong of Benxi Liaoning province,will be chosen to reconstruct high resolution proxy index of EASM,based on MC-ICP-MS-²³⁰Th dating and high resolution stable oxygen isotope analysis.The second purpose of this study is to discuss the evolution process and the internal structure of 5.5 ka event and its forcing mechanism.The last analyzes the cultural development in northeast China and the relationship between climate change.The following conclusions can be drawn:?1?From 10 ²³⁰Th ages and 235 oxygen isotope data points,the stalagmite from ShuiDong reconstructs the time sequence of carbon and oxygen isotope from 5.88 to 4.83 ka B.P.?relative to AD 1950?,and its average resolution is about four years.?2?Stalagmites TW704 indicates decade-scale and century-scale variability of the EASM,in the entire study period?5.82?4.77ka B.P.?,it shows a significant weak-strong-weak century-scale oscillation,including two weak monsoon the center of the stage time respectively 5.54 and 4.95 ka B.P..?3?TW704 oxygen isotopic records are difference compare with Oman stalagmite record,and TW704 records basically consistent with the southwest Dongge cave stalagmites DA records within the scope of the error,but the TW704 records of two weak monsoon period is more significant.?4?Although TW704 oxygen isotopic sequence spectrum analysis results show a significant 11 and 22 years solar cycle,but comparing with solar activity indicators(Total Solar Irradiance,Sunspot Number and ¹⁰Be),there is no obvious corresponding relation between them,there are even contrary trend in century-scale,especially weak monsoon stage??5.0 kaB.P.?,is the strongest period of solar activity of this period.So the solar activity is not the forcing of weak monsoon event.By contrast,TW704 records have good corresponding relationships with ENSO event.It shows that stalagmites oxygen isotopes in response to ENSO change.?5?This time?5.82?4.77 kaB.P.?is the middle-late HongShan culture of human culture?BC4000?BC3000 years?and late XiaoHeYan cultural and XiaoZhuShan upper culture?BC3000?BC2000 years?of the late neolithic age in western Liaoning.The transition of the two stages during the summer monsoon weakened quickly,summer monsoon weakened suddenly may lead to reduce precipitation and the agricultural productivity in the region.That may affect the stability of the HongShan culture,but in view of the climate to adapt to the complex relationship between environment and human,the climate change is the root cause of the decline of HongShan culture still need more evidence,including archaeological evidence.