桂林响水洞6.00 ka B P以来石笋高分辨率的气候记录

High Resolution Climatic Records of Stalagmite from Xianshui Cave in Guilin since 6.00 ka B P

通过对桂林响水洞的石笋进行高精度的TIMS U系测年和C、O同位素分析 ,建立了中全新世 6 .0 0kaBP以来桂林地区高分辨率的古气候变化时间序列。石笋剖面的C、O同位素记录揭示 ,桂林地区中全新世 (6 .0 0kaBP)以来的季风气候变化 ,大致可分为 2个气候期 :6 .0 0～ 3.5 7kaBP为气候适宜期 ,显示东亚夏季风由强盛逐渐变为减弱的趋势 ,为气候温暖湿润期 ;3.5 7～ 0 .37kaBP为降温期 ,显示东亚夏季风减弱 ,冬季风增强以及气候的大幅度波动。在这一降温期 ,间夹多次短暂的温暖期。石笋同位素记录的研究结果表明 ,在 6 .0 0～ 0 .37kaBP间的中全新世———气候适宜期 ,δ18O值由偏负逐渐向偏正的变化趋势 ,反映东亚夏季风由强变弱 ,降雨由多变少 ,气温由高变低的变化趋势。

The time sequence of high resolution paleoclimatic change since the middle Holocene——6.00 ka B P has been reconstructed by ages of the high precision TIMS U series and an analysis of carbon and oxygen isotopes of stalagmite from Xianshiu cave in Guilin. Carbon and oxygen isotopic records of stalagmite section reveal that the monsoon climate changes since the middle Holocene——6.00 ka B P can be divided approximately into two climate periods:① Climate optimum time of 6.00～3.57 ka B P,during which the East Asian (or Southeast) Monsoon changed gradually from strong to weak and the climate was warm and humid; ② Temperature falling period of 3.57～0.37 ka B P,when the East Asian Summer Monsoon became weak, the Winter Monsoon became strong and the climate experienced considerable variation. This temperature falling period was intercalated with many short warm periods. Isotope records of stalagmite show that δ 18 O values of stalagmite change from negative to positive, suggesting that, during the middle Holocene climate optimum period (6.00～0.37 ka B P), the East Asian Summer Monsoon evolved from strong to weak, the Winter Monsoon changed from weak to strong, the rainfall gradually decreased, and the air temperature gradually fell.