苏州澄湖SC7孔沉积物粒度特征及其古环境意义  

Grain-size characteristics and their paleoenvironmental significance of SC7 core sediments in Lake Chenghu, Jiangsu Province, China

作　　者：史凯[1] 戴雪荣[1] 师育新[1] 俞立中[1] 

机构地区：[1]华东师范大学资源与环境科学学院地理学系,上海200062

出　　处：《湖泊科学》2009年第5期741-748,共8页Journal of Lake Sciences

基　　金：国家自然科学基金项目(40571170)

摘　　要：苏州澄湖湖底主要由硬粘土组成,同时残留有湖沼洼地和古河道.古河道大致呈NNW-SSE延伸,与历史文献所载"古三江"之一的东江基本一致,保存着硬粘土平原形成后从河流到湖泊环境演化的良好沉积记录.通过对湖心区古河道SC7孔2cm间隔取样和AMS14C测年、粒度、磁化率等测试分析,初步探讨了该孔的沉积粒度特征及古环境意义.研究结果表明,沉积物粗粉砂含量极少或不含,中—细粉砂和粘土分别占53%-65.8%和19.7%-40.1%;与河床硬粘土相比,粉砂含量较低,粘土含量较高,平均粒径较小,为正偏(硬粘土为极正偏),磁化率也明显较高.多种粒度指标和磁化率指标均表明,澄湖的形成具有河流、河流—湖泊过渡到湖泊的阶段性演化特点,为太湖平原湖荡区湖泊的河泛成因提供了新的证据.现代澄湖则明显受到人类活动的扰动影响.The sediment of Lake Chenghu, located in the southeastern area of Suzhou, is mainly composed of ＇hard clay＇ （a kind of sediment consisting of silt and clay）, and has been featured with lake depressions and a paleo-channel in the central area. The paleo-channel, along the direction of NNW-SSE, is accord with the Dongjiang River recorded in historical documents, and its sediments may become good archives of environmental evolution of the hard clay plain from river to lake. The grain-size characteristics of core SC7 of Lake Chenghu, AMS14C and their magnetic susceptibility were analyzed in this paper, then the sedimentary characteristics and paleoenvironmental significance were discussed. The results indicate that the sediments of Lake Chenghu mainly consisted of fine-medium silt and clay, and the percentage of fine-medium silt was about 53%-65.8%, clay about 19.7%-40.1%. The grain-size parameters of the sediments above 336cm was different from hard clay, and magnetic susceptibility was significantly higher. Grain-size parameters and magnetic susceptibility of the sediments show that the sedimentary environment of Lake Chenghu had experienced four main phases from river to lake after the formation of hard-clay plain, and also provided new evidence for the causes of river-flooding lakes in Taihu Plain. It also suggested that the formation of surface sediments had been seriously affected by human activities.

关 键 词：东江 沉积记录 粒度 磁化率 澄湖 太湖平原 

分 类 号：P512.2[天文地球—地质学]