贵州威宁麻窝山岩溶盆地剖面中Rb、Sr分布及环境信息  

Distribution and Environmental Information of Rb and Sr in the Mawo Karst Basin Sediments of Weining in Guizhou

作　　者：曹振兴[1] 吴攀[1] 顾尚义[1] 彭德海[1] 杨绍章[1] 

机构地区：[1]贵州大学资源与环境工程学院,贵阳550003

出　　处：《地质学报》2013年第2期259-268,共10页Acta Geologica Sinica

基　　金：国家重点基础研究发展规划"973"子项目(编号2006CB403202)"碳酸盐岩风化的生物地球化学过程与成土速率"资助的成果

摘　　要：岩溶盆地的演化清晰地记录了流域侵蚀和化学风化等重要过程,Rb/Sr是有效获取地表过程中环境信息的重要手段之一。本文基于14C定年方法,结合研究剖面中K、Ca等元素的组成特征,对贵州威宁麻窝山岩溶盆地中4个沉积剖面的Rb、Sr分布和地球化学行为进行了分析,并讨论了Rb/Sr指示的环境意义和盆地的演化历程。结果表明,剖面中Rb元素含量普遍高于Sr元素且波动幅度较Sr元素大。此外,Rb与K,Sr与Ca之间均有较好的正相关关系,即在流域物质的侵蚀、搬运和盆地沉积物的形成演化过程中,Sr的活动性明显高于Rb。各剖面Rb、Sr垂直分异程度相似,呈大—小—大交替演变,Rb/Sr以大—小—大规律变化,且剖面间具有较好的一致性,与野外特征相吻合,尤其是剖面颜色变化,均体现盆地沉积环境的多旋回特征。Rb/Sr具有重要的环境意义,能够指示研究区古气候变化,Rb/Sr高时(主要受Rb控制),盆地处于干涸或低水位状态,指示降水量较少的干旱气候;Rb/Sr低时(主要受Sr控制),盆地处于富水的高水位环境,指示降水量较多的湿润气候。在距今40ka时间内,岩溶盆地内至少出现312次干—湿环境的旋回演变,其是恢复喀斯特地区古气候的良好载体。The evolution of karst basin plays a crucial role in earth surface processes, which well records the history of watershed erosion and chemical weathering. Rb/Sr has been widely used for revealing environmental information among different palaeoclimatic archives. In this study, based upon the H C dates and characteristics of K and Ca in the Mawo karst basin sediments from Weining county of Guizhou province, the geochemical behaviour of Rb and Sr were analysed and Rb/Sr were compiled for the palaeoclimate in Northwest Guizhou. The results showed that concentrations of Rb in the four studied profiles were mostly greater than Sr, and strong positive correlations between Rb and K and between Sr and Ca were observed, which further confirmed the notion that Sr was more mobile than Rb in the evolution of Mawo karst basin. The vertical variation of Rb/Sr in all profiles suggested periodic sedimentary environment in the studied area, which corresponded to the field characteristics, especially the color variation of the sediments. High Rb/Sr primarily controlled by Rb indicated the arid climate or a low 1 water level of the basin, otherwise the opposite. There existed 3 1/2 dry-moist climate cycles in the past 40ka of the karst basin that could be used as ideal archive for reconstructing palaeoclimate in karst areas.

关 键 词：岩溶盆地 RB SR 地球化学 古气候 贵州威宁 

分 类 号：P597.3[天文地球—地球化学]