中文摘要：

基于辽宁本溪庙洞降水和滴水的氢氧同位素，以及滴水碳酸钙沉积的氧同位素两年的观测数据（2012~2013年），本文分析了庙洞滴水氧同位素对大气降水氧同位素的继承性，分析并讨论了洞穴滴水碳酸钙沉积的氧同位素时空变化特征、影响因素及其对石笋古气候重建的指示意义。结果表明：1）庙洞降水δ18Op季节性特征明显，冬季降雪最负（-13.43‰），6~9月降雨次之（-9.82‰），而春秋季降雨最正，当地降水线：δD=7.28δ18O＋7.10（n=21，r=0.97），与东北地区大气降水线平行，但过剩氘更大；斜率小于全球大气降水，与北京石花洞结果更接近。2）庙洞3个观测点的滴水δ18Ow在误差范围内基本相同（约-9.6‰），常年稳定，年际变化微弱（0.2‰），值介于全年降水加权平均值（-9.81‰）与4~10月降雨加权平均值（-9.56‰）之间，更接近于后者，滴水的δD-δ18Ow位于降雨线性回归线的平均位置，与降雪的δD-δ18O回归线明显不同，说明滴水更多记录降雨的平均值，而降雪贡献较小。3）滴水碳酸钙沉积的氧同位素出现显著的空间差异，滴水较快的点，其δ18Oc没有明显的季节变化；相反，滴水慢的点，则出现明显的季节性变化（变幅约为0.4‰），其δ18Oc值相对于滴水快的点整体偏正约0.26‰，这种时空差异可能是由滴率太慢引起的动力分馏造成的，其机制可能与蒸发作用增强和（或）CO2逸出比例增大有关。这种动力分馏机制可能是一些相同时段石笋氧同位素出现系统偏差的潜在原因。4）滴水沉积的δ18Oc值较理论计算值δ18Oct偏正，即使是无明显动力分馏的点也相差约0.59‰，这与最近一些室内模拟实验结果类似，暗示洞穴滴水氧同位素分馏系数较常规经验值（1.0313）略大。

英文摘要：

The Miaodong Cave （41°03＇N,125°31＇E） is located in Huanren County,Benxi City,Liaoning Province,171km northeast of Shenyang City.The location is close to northern margin region of the East Asian Summer Monsoon （EASM）.Its climate is sensible to oscillation of EASM.High-resolution stalagmite δ18O record in this area is important for understanding the evolution and mechanism of EASM.However,interpretation of stalagmite δ18O is never straight forward due to complex karst processes.Thus,knowledge about transfers of seasonal isotopic variability among meteoric precipitation,drip-water and its calcite deposition is crucial for better understanding of stalagmite δ18O.To this end,sub-monthly in situ monitoring of δ18O in the meteoric precipitation,drip-water and calcite deposition rate was carried out at Miaodong Cave,through two hydrological years （from January 2012 to December 2013） to determine the seasonal variability and mechanisms of oxygen isotopic transfer in Miaodong Cave.Oxygen isotopic ration in precipitation （δ18Op,VSMOW） exhibits significant seasonal trend,with most negative values in winter snow （-13.43‰）,and less negative values from June to September （-9.82‰）,while more positive values in spring and autumn rainfall.Annually weighted average value of δ18Op is about -9.81‰,and weighted average value of rainfall （from April to October）δ18Op is -9.56‰.The local Meteoric Water Line （LMWL） has smaller slope,which is different from Global Meteoric Water Line （GMWL） and those of from Southern China,but is similar with that of Beijing region.Unlike to large amplitude variability of δ18Op,values of δ18O in drip water （δ18Ow,VSMOW） of three drip sites （MD1,MD3 and MD4） show extremely constant both on seasonal and spatial scales,with a mean value of-9.6‰,although there is slightly inter-annual variability （about 0.2‰ negative in 2013 than in 2012）.δ18Ow range between annually weighted average of precipitation and weighted average of rainfall ?