中文摘要：

基于陕南祥龙洞石笋XL2的19个230Th年龄、218个氧同位素分析以及896个Sr/Ca分析数据,高分辨率重建了4200～1972a B.P.期间陕南地区季风降雨变化.重建结果显示陕南地区这一时期季风降雨有显著的127～105a和57a周期,可能分别受控于太阳活动、PDO和/或AMO的变化.重建时段有3次百年尺度的干旱事件,分别发生于2200～2100a B.P.,2900～2700a B.P.和3600～3400a B.P.,其中2900～2700a B.P.干旱事件对应于北大西洋地区2.8ka冷事件.对比研究显示,尽管祥龙洞石笋和董哥洞石笋δ18O记录整体一致,但除了2900～ 2700aB.P.干旱事件之外,其他两次干旱事件在董哥洞石笋记录中并不明显.而尽管总体上祥龙洞和和尚洞石笋δ18O记录的差异要大,但XL2的3次干旱事件在和尚洞记录都有明显体现.有精确年代控制的祥龙洞、董哥洞及和尚洞石笋氧同位素记录的差异,揭示晚全新世我国季风降雨在十一百年尺度存在区域差异.

英文摘要：

Southern Shaanxi is located on the south slope of the Qinling Mountains,and the climate here is controlled by monsoon system.The advancement and retreatment of Asian summer monsoon have an important influence on precipitation variations in this region.We collected an aragonite stalagmite XL2 from Xianglong Cave （32°59′51″N,106°19′41″E; 940m a.s.l） in southern Shaanxi Province,Central China.19 subsamples,50～ 100mg,were drilled parallel to the growth planes of XL2 and dated with U-series methods at the Minnesota Isotope Laboratory.218 powdered subsamples （ca.50μg） were drilled out along the central growth axes of the stalagmite for stable isotope analyses at the Institute of Earth Environment,Chinese Academy of Sciences.Sr and Ca counts of the stalagmite were measured using the Itrax core scanner at the First Institute of Oceanography,State Oceanic Administration at 0.1mm resolution.A total of 896 Sr/Ca data were then obtained.The results suggested that XL2 grew from 4200 a B.P.to 1972a B.P.,and its growth rates varied between 0.03 and 0.18mm/a.The average resolution of the δ18O series is about 10a,and the average resolution of the Sr/Ca series is about 2a.The δ18O and Sr/Ca ratios show coherent variations （r =0.20,n =218,p＜0.01）.For example,they both increased in ca.2700a B.P.,3500a B.P.and 3800a B.P.,but decreased in ca.2450a B.P.,3200a B.P.and 3900a B.P.The positive correlationship of the two series indicates that there were both controlled by monsoon precipitation variations.We thus use the proxy records of the stalagmite to reconstruct high-resolution monsoon precipitation variations in this region during the period of 4200～ 1972a B.P.There are three centennial scale droughts during the reconstructed period,which occurred in 2200 ～ 2100 a B.P.,2900～2700a B.P.and 3600～3400a B.P.The reconstruction show significant periodicities at 127～ 105a and 57a,which may be related to solar activity and PDO/AMO,respectively.The δ18O record of XL2 is similar with the δ18O record of DAS