川东北狮子洞石笋54～46ka高分辨率δ^(13)C变化与影响因素

The high-resolution speleothem δ^(13)C record during 54～46 ka from the Shizi Cave in NE Sichuan, Central China and influencing factors

对采自川东北狮子洞的编号SI3石笋(发育时间在54~46 ka)进行了高分辨率碳同位素(δ^(13)C)测试。石笋SI3的δ^(13)C与δ^(18)O变化趋势基本一致,表明夏季风气候控制的地表植被和其他因素如水-岩相互作用、滴水时间间隔和洞穴通风作用等是影响SI3的δ^(13)C变化的主要因素。在寒冷事件H5发生时SI3的δ^(13)C与δ^(18)O的变化存在显著差异。推测δ^(13)C更早变轻与先期碳酸盐沉积作用减弱有关,可能指示洞穴通风作用和洞外冬季风在H5发生早期就开始减弱,即冬、夏季风在这一时期可能发生了脱耦现象。

Stalagmite SI3, which is 241 mm in length, was collected from the Shizi Cave （32°24′N,107°10′E） in NE Sichuan, Central China. Ten precise ^230Th dates indicate that SI3 developed during 54-46 ka. A total of 236 sub-samples were measured for stable carbon isotopic composition （δ^13C） to investigate its paleoclimatic and paleoenvironmental significance. The δ^13C and δ^18O records of SI3 show a similar long-term trend during 54-46 ka, implying that the δ^13C of SI3 was significantly influenced by ground vegetation and other factors such as water-rock interaction, dripping interval and ventilation of the Shizi Cave. In addition, theδ^13C and δ^18O records of SI3 show significant differences during the H5 cold event that δ^13C shifted to negative values much earlier than δ^18O, which is possibly related to relatively less CO2 degassing and prior calcite precipitation, and in turn to weaker ventilation of the cave and winter monsoon, suggesting a decoupling between winter and summer monsoons during the H5 cold event.