THE RECORDS OF CLIMATIC CHANGE FROM A STALAGMITE DURING THE LATE TIME OF THE MIDDLE HOLOCENE IN NINGLANG AREA,YUNNAN

Research on climatic changes in the Holocene plays an important role in paleoclimatology. At present, the research of climatic change in Holocene is using various geological records or proxies. The time sequence of paleo-climatic change in Ninglang area between 4 500 aBP and 2 000 aBP has been reconstructed by α-U series dates and analysis of the oxygen isotopes from a stalagmite in Xianren cave in Ninglang, Yunnan. Our study results have shown that the paleoclimatic environment change can be divided into six stages:①warm and dry climate environment from 4 500 aBP to 4 000 aBP;②cold and dry climate environment from 4 000 aBP to 3 400 aBP, which is an abrupt change in the climatic evolution of middle Holocene;③the warm and humid climate environment from 3 400 aBP to 3 100 aBP;④cold and dry climate environment from 3 100 aBP to 2 650 aBP;⑤warm and humid climate environment from 2 650 aBP to 2 400 aBP;⑥cold to cool and humid climate environment from 2 400 aBP to 2 000 aBP. The monsoon change from the stalagmite record on the short time scale since the late time of middle Holocene is obviously affected by the strength of the solar radiation in the middle and low latitude regions and air circumfluence in Northern Hemisphere. The main driving mechanism of Indian monsoon evolution is controlled by change of the solar radiation. Stalagmite record revealed that Indian summer monsoon moved forward rapidly, and climate undulation on a century scale resulted in the change of the solar radiation.