贵州七星洞石笋记录的最近2300年气候和环境变化

A high resolution paleoclimate record of the last 2300 years in stalagmite QX-3 from the Qixing Cave,Guizhou Province

基于贵州都匀七星洞石笋(QX-3)8个^(230)Th年代数据和414个δ^(18)O数据建立了研究区过去2360年、分辨率约为5年的石笋氧同位素时间序列。七星洞石笋QX-3δ^(18)O记录与灰度记录高度相关,表明石笋灰度值的变化亦可作为重建古气候和古环境的一个替代指标。功率谱分析显示石笋QX-3δ^(18)O序列具有显著的24~20 a和12~10 a周期,与树轮Δ^(14)C周期有很好对应,为太阳辐射驱动气候变化假说提供又一重要证据。亚洲季风区万象洞、黄爷洞、和尚洞、七星洞和董哥洞的δ^(18)O年代序列曲线对比显示,在长时间尺度上各洞穴的δ^(18)O记录均表现出较一致的气候环境变化特征;但在百年到数十年尺度上存在一定差异,这可能指示了区域降水对亚洲季风变化的响应差异。

Based on 8 accurately dated 230Th ages and 414 stable oxygen isotope compositions （δ18O） obtained from the stalagmite QX-3 from Qixing Cave, Duyun City, Guizhou Province, a 5-year resolution oxygen isotope profile of the past 2300 years was established, which likely documented the precipitation changes at the cave site. Using the scanned image, the grayscale of the polished section of the stalagmite QX-3 was also attained. The grayscale profile of the stalagmite was highly correlated with the δ18O series, indicating that the stalagmites＇ grayscale could be used as a proxy index for paleoclimatic and paleoenvironmental reconstruction. The spectrum analysis of QX-3 δ18O sequence showed that the periods of 24~20 years and 12~10 years were significant （above the 95% confidence level）. These periods corresponded well with that found in the tree-ring reconstructed △14C series, further confirming the forcing of solar activity on the Asian monsoon climate. The comparison of QX-3 δ18O record and other speleothem δ18O records, i.e., the records from Wanxiang Cave, Huangye Cave, Heshang Cave, and Dongge Cave, showed the general consistant characteristics of precipitation changes on the long- term. However, the differences on centennial to decadal time-scales were significant, implying the diverse responses of regional precipitation to the Asian monsoon changes on these time-scales.