苏州澄湖sc7孔沉积物粒度特征及其古环境意义 史凯09湖泊科学

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1、LakeSci．(湖泊科学)，2009，2l(5)：741—748http：／／www．jlakes．org．E—mail：jlakes@niglas．ac．cn02009byJournalofLukeSciences苏州澄湖SC7孔沉积物粒度特征及其古环境意义史凯，戴雪荣“，师育新，俞立中f华东师范大学资源与环境科学学院地理学系，上海200062)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

2、隔取样和AMS”C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，中一细粉砂和粘土分别占53％一65．8％和19．7％一40．1％；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、河流一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．关键词：东江；沉积记录；粒度；磁化率；澄湖；太湖平原Grain—sizecharacteristicsan

3、dtheirpaleoenvironmentalsignificanceofSC7coresedimentsinLakeChenghu，JiangsuProvince，ChinaSHIKai，DAIXuerong，SHIYuxin&YULizhongepartmentofGeography，SchoolofResourcesandEnvironmentalScience，EastChinaNormalUniversity，Shanghai200062，PR．China)Abstract：ThesedimentofLakeChenghu，locatedinthesoutheas

4、ternareaofSuzhou，ismainlycomposedof‘hardclay’(akindofsedimentconsistingofsiltandclay)，andhasbeenfeaturedwithlakedepressionsandapaleo—channelinthecentralarea．Thepaleo—channel，alongthedirectionofNNW-SSE，isaccordwiththeDongjiangRiverrecordedinhistoricaldocuments，anditssedimentsmaybecomegoodarc

5、hivesofenvironmentalevolutionofthehardclayplainfromrivertolake．ThegrainsizecharacteristicsofcoreSC7ofLakeChenghu，AMSCandtheirmagneticsusceptibilitywereanalyzedinthispaper,thenthesedimentarycharacteristicsandpaleoenvironmentalsignificancewerediscussed．TheresultsindicatethatthesedimentsofLake

6、Chenghumainlyconsistedoffine—mediumsiltandclay,andthepercentageoffine—mediumsiltwasabout53％～65．8％．clayabout19．7％一40．1％．Thegrain—sizeparametersofthesedimentsabove336cmwasdifferentfromhardclay,andmagneticsusceptibilitywassignificantlyhigher．Grain-sizeparametersandmagneticsusceptibilityofthese

7、dimentsshowthatthesedimentaryenvironmentofLakeChenghuhadexperiencedfourmainphasesfromrivertolakeaftertheformationofhard-clayplain，andalsoprovidednewevidenceforthecausesofriver-floodinglakesinTaihuPlain．Italsosuggestedthattheformationofsurfacesedimentshad