川东北宋家洞高分辨率石笋δ^(13)C记录与D/O事件5-1

A high-resolution speleothem δ^(13)C record from Songjia Cave in NE Sichuan, Central China and D/O event 5 to 10

基于川东北宋家洞石笋SJ1的399个稳定碳同位素组成(δ13C)数据建立了末次冰期中晚期(14~43 ka)高分辨率δ13C时间序列。SJ1的δ13C变化与已发表的该石笋稳定氧同位素组成(δ18O)变化趋势非常一致,清晰地记录了该地区植被对D/O事件5-10的敏感响应。东亚夏季风气候控制的地表植被(包括C3和C4植被比例C3/C4变化和植被密度变化)和土壤微生物活动变化可能是影响SJ1的δ13C变化的主要因素。在这些D/O事件发生时δ13C变轻,指示了C3/C4植被比例上升和植被密度增加。此外,受降水控制的岩溶地下水流速影响的水-岩相互作用,石笋表面滴水时间间隔、洞穴空气的CO2分压和洞穴通风效应等因素影响的CO2脱气作用和先期碳酸盐沉积也可能对SJ1的δ13C变化产生了影响。

A stalagmite （S J1） collected from Songjia Cave in NE Sichuan, China, established with 399 δ^13C data, provides a high-resolution spleothem δ^13C time series covering the late part of the last glacial period （14-43 ka）. The S J1 δ^13C record appears to be consistent with the change trend of the published S J1 δ^18O record, which clearly documents the changes in vegetation during D/O events 5 to 10. The S J1δ^13C record may be mainly controlled by East Asian monsoon-driven changes in vegetation above the cave （changes in proportion of C3 to C4 plant and/or density of vegetation） and soil microbial activity. The δ^13C record decrease is coupled with the D/O events, indicating that the proportion of C3 to C4 plant and density of vegetation both increase at that time. In addition, some other factors such as water-rock interaction influenced by the flow rates of groundwater which is controlled by precipitation, CO2 degassing and prior calcite precipitation which was influenced by drip rates over a speleothem surface, cave air pCO2 and cave ventilation, may also influence the S J1 δ^13C record. The big value of δ^13C in the top section of SJI may be related to bigger precipitation and shorter residence time of soil water.