澧阳平原末次冰期-早全新世气候环境演变研究

Environmental Change Recorded by Sediments from Liyang Plain in the Middle Reaches of Yangtze River

通过对澧阳平原野外考察、典型剖面YC自然沉积剖面的系统采样、室内地球化学元素Li、Rb、Sr、Ba和Li/Ba、Rb/Sr比值的分析,以及沉积物年代样品的OSL和AMS14C年代测定,探讨了长江中游地区澧阳平原末次冰期-早全新世的气候环境变化过程。结果表明,MIS3阶段晚期（31.80~23.80 ka BP）暖湿期记录明显,对应的沉积物含大量黑色铁锰膜和铁锰结核,地球化学元素Li含量、Rb含量、Rb/Sr比值、Li/Ba比值出现峰值,而Sr含量、Ba含量出现低谷,表明此时期冬季风减弱,夏季风增强,降水量增大,温度上升,风化作用显著增强。澧阳平原YC剖面很好的记录了56.00~6.96 ka BP的气候环境演变过程,大致经历了冷干期（56.00~31.80 ka BP）、相对暖湿期（31.80~23.80 ka BP）、冷湿期（23.80~10.60 ka BP）、暖湿期（10.60~6.96 ka BP）4个气候变化阶段。

Based on the field investigations and sampling as well as laboratory analysis of geochemistry elements（Li,Rb,Sr,Ba,Li/Ba,Rb/Sr）,optically luminescence（OSL） and AMS 14C dating of natural profile in YC country in Liyang plain,this paper revealed the high-resolution climatic events from the last glacial to the earlier Holocence.The results show late period of MIS 3（31.80-23.80 ka BP）with rather warm and wet climate condition recorded by the YC profile from geochemical evidences,the sediments of the correspondent stratigraphy have much more iron-manganese nodules,and have high values of Li contents,Rb contents,Rb/Sr ratio and Li/Ba ratio,but have low values of Sr content and Ba content in this layer,which indicating that winter monsoon weakened,and summer monsoon increased,and the precipitation increased and the temperature rose in this area,therefore the weathering action became intensive.Moreover,sediments of YC profile have well recorded the climatic environmental change during 56.00-6.96 ka BP in Liyang plain.Four stages of climatic change can be found in Liyang plain.Four stages of climate change are as follows： cold and dry period（56.00-31.80 ka BP）,relative warm and wet period（31.80-23.80 ka BP）,cold and wet period（23.80-10.60 ka BP） and warm and wet period（10.60-6.96 ka BP）.