鄱阳湖沉积物粒度特征及其对形成演变过程的示踪意义  

Poyang Lake Sediments Grain Size Characteristics and Its Tracing Implication for Formation and Evolution Processes

作　　者：董延钰[1] 金芳[1] 黄俊华[1] 

机构地区：[1]中国地质大学地质过程与矿产资源国家重点实验室,武汉430074

出　　处：《地质科技情报》2011年第2期57-62,共6页Geological Science and Technology Information

基　　金：国家重点基础研究发展计划"973"项目(2011CB808800);地质过程与矿产资源国家重点实验室专项经费项目(MSFGPMR201007)

摘　　要：通过对鄱阳湖大汊湖ZK04钻孔沉积物的粒度分析,揭示了该地区沉积物粒度特征。结果表明,从湖滨到湖心沉积物粒度呈由砾石→粗砂→细砂→粉砂→黏土等逐渐变细的正旋回,其沉积时代可分为6个阶段：第1阶段（601~530 cm）,M、KG、SD、SK都为曲线中最高峰,频率为4峰型,该阶段气候暖湿,彭蠡泽形成;第2阶段（530~380 cm）,M、KG、SD、SK在曲线中最小且平稳,频率曲线呈双峰型马鞍状,内部由下至上可分为湖湾相、深湖相、浅湖相;第3阶段（380~168 cm）,M、KG、SD、SK都比较大,频率曲线呈双峰型,沉积环境从湖相过渡到三角洲前缘相;第4阶段（168~100 cm）：平均粒径较小且稳定,KG,SD,SK都比较大且有波动,频率曲线为4峰或3峰型,彭蠡泽越过湖口;第5阶段（100~70 cm）,平均粒径逐渐增大,KG、SD、SK都比较小,频率曲线为双峰型,水下三角洲不断向前推进;第6阶段（70~0 cm）,粒径波动频繁,KG、SD、SK在总体较低的水平上有少许波动,气候冷干,人类活动加剧,湖泊面积萎缩。粒度变化及沉积环境演变显示出鄱阳湖在4 500 a以来呈现河湖相交替发展的现象。This paper analyzes the grain sizes of sediments from Poyang Lake to reveal the pattern of their distribution.From lake side to the middle of the lake,the grain sizes show a fining-upwards sequence decreasing from gravel,coarse sand,fine sand,silty sand to clay.Their deposition times can be divided into six different stages.In the first stage（601-530 cm）,M,KG,SD and SK were all in the peak,showing the frequency curve of a four peak type.During this stage the climate of the stage was warm and wet and Penglize（the ancient Poyang Lake） was formed.In the second stage（530-380 cm）,M,KG,SD and SK were the smallest and smooth with the frequency curve of bimodal saddle shape.The internal bottom-up phase can be divided into the lake,deep lake and shallow lake.In the third stage（380-168 cm）,M,KG,SD and SK were larger with the frequency curve of two peaks.The sedimentary environment was transitioned from the lacustrine phase to the delta front.In the fourth stage（168-100 cm）,the grain size was small and stable and KG,SD and SK are relatively large and fluctuant,showing the frequency curve of four peaks or three peaks.Pengyize（lake） was connected with Poyang lake.In the fifth stage（100-70 cm）,the average grain size increased and KD,SD and SK were smaller,showing the frequency curve of double peaks.In the sixth stage（70-0 cm）,the grain size changed with frequent fluctuations and KG,SD and SK were overall lower with minor fluctuations.The climate was cold and dry,and Poyang Lake shrank.The variation of grain sizes and sedimentary environments indicate that Poyang Lake have been alternately changed from river to lakes since 4 500 a ago.

关 键 词：粒度 鄱阳湖 沉积相 

分 类 号：P584[天文地球—岩石学]