云南宁蒗地区中全新世晚期气候变化的石笋记录

通过对云南宁蒗县永宁区仙人洞石笋进行α-U系测年和碳氧同位素分析,建立了4 500~2 000 aBP的古气候变化时间序列。研究结果表明,永宁地区在4 500~2 000 aBP间石笋记录的冷暖事件所反映出的气候变化,大致可分为6个气候阶段:4 500~4 000 aBP气候温暖干旱;4 000~3 400 aBP气候寒冷干旱,是中全新世晚期的一次重要的气候演变转折时期;3 400~3 100 aBP气候温暖湿润;3 100~2 650 aBP气候寒冷干旱;2 650~2 400 aBP气候温暖湿润;2 400~2 000 aBP气候冷凉湿润。中全新世晚期以来,石笋记录的这些短时间尺度的气候事件,明显受中-低纬度太阳辐射强度以及北半球大气环流的影响,太阳辐射强度的变化是控制印度季风演变的主要动因。石笋记录揭示印度季风的快速推进或退出(萎缩)以及百年尺度上的气候波动是太阳辐射量变化造成的结果。

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.