Preliminary research on climate evolution and driving mechanism during the Middle Holocene in Xundian, Yunnan

By dating ages of TIMS-U series and analyzing carbon and oxygen isotope and content of organic carbon in XR1 stalagmite from Xianren Cave in Xundian, Yunnan, the paper reconstructs monsoon climate change pattern during the middle Holocene in Xundian. It can be divided into three climate periods approximately: (1)8.0～6.0ka B.P. was warm and wet period; (2)6.0～5.1ka B.P. was climate change period. During the period, climate changed from wet and warm to cold and dry; (3)5.1～2.1ka B.P. was climate recovering period. In the period, the climate changed from cold and dry to the average climate level of the Middle Holocene. After contrasting organic carbon variation to δ18O record, it reveals that organic carbon in stalagmite can reflect climate change. But organic carbon variation lags to climate change. At last, on the basis of δ18O record and summer solar radiation at 33°N latitude, the driven factors of climate change in Xundian, Yunnan Province during the mid-Holocene is analyzed. The result show the climatic changing trend in Xundian, Yunnan Province was controlled by summer solar radiation at 33°N latitude and may affected by volcanic activity during the mid-Holocene.