重庆新崖洞4.5ka以来气候变化的石笋微量元素记录及环境意义

根据重庆新崖洞石笋XY6已有的碳氧同位素成果,进一步探讨微量元素指标(Mg/Ca,Sr/Ca,Ba/Ca及Mg/Sr)的气候及环境意义。认为Mg/Ca比值可以作为古降水的气候指标,极好地记录这4 500 a来的气候干湿变化,尤其对4 000 a B.P.左右的季风降水减少有明显的响应。此外,Mg/Ca与碳氧同位素记录反映的气候信息也基本一致。Sr/Ca和Ba/Ca与Mg/Ca比值的变化也有相似性,但其作为气候指标的稳定性较差,易受到地表植被、土壤微生物活动等众多因素的干扰。

Climate Change Since 4.5 ka B.P. Recorded by Trace Elements in a Stalagmite from Xinya Cave in Chongqing

High-resolution stalagmite records serve as excellent proxy of investigating past climatic and environmental changes, and multiproxy studies have enormous potential in identifying process controls and fulfilling the potential of speleothems in paleoclimatical and palaeoenvironmental analysis. In this paper, climate change and environmental significance of trace-element ratios from stalagmite XY6(such as Mg/Ca, Sr/Ca, Ba/Ca, Mg/Sr) were discussed by comparing with the stable oxygen and carbon isotopes results of stalagmite XY6 from Xinya Cave in Chongqing.The results showed that the Mg/Ca ratio can be used as a climatic proxy of precipitation, indicating the climate change since 4.5 ka B.P., and agreed well with the climatic change revealed by oxygen and carbon isotopes records. Notably, the Mg/Ca ratio was sensitive to the event of abrupt decline in precipitation at 4.0 ka B.P. Although the time series of Sr/Ca and Ba/Ca ratios coincides roughly with to the variation of Mg/Ca, they were readily disturbed by many factors such as vegetation and soil microbes, thus are less stable.