沂沭河流域7 470~2 550 a BP气候变化的元素地球化学记录

地球化学元素比值的变化不仅可以指示气候变化和环境特征,也可以揭示气候异常和突变性气候事件。本文通过对沂沭河流域沭埠岭剖面沉积物淋溶系数、残积系数、CaO/MgO、硅铝率、硅铝铁率等气候代用指标的分析,发现研究区7 470~2550 a BP期间的气候变化经历了五个阶段:(1)7 472~6 043 a BP,气候趋向温暖湿润;(2)6 043~4 801 a BP,稳定的暖湿时期;(3)4 801~3 986 a BP,气候向冷干转变;(4)3 986~3 512 a BP,不稳定时期;(5)3 512~2 552 a BP,气候不稳定的波动时期。

Elemental Geochemistry for Climate Change of Yishu River Basin during 7 470-2 550 a BP

Changes of geochemical elements ratio can not only indicate climate change and environmental characteristics, but also reveal abnormal and abrupt climate events. Based on the analysis of weathering eluvial indexes, eluvial coefficient and the ratios of CaO/MgO, SiO₂/Al₂O₃ and SiO₂/(Al₂O₃+Fe₂O₃) of Shubuling section in Yishu River Basin, climate changes during 7 470-2 550 a BP was divided into five stages:(1) 7 472-6 043 a BP, the period of climate changing into warm and wet;(2) 6 043-4 801 a BP, the period of stable warm and wet;(3) 4 801-3 986 a BP,climate changing into colder and drier;(4) 3 986-3 512 a BP; climate being not stable and flexible; and(5) 3 512-2 552 a BP, the period of climate unstable fluctuation.