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1、J.LakeSci.(湖泊科学),2009,21(5):741-748http://www.jlakes.org.E-mail:jlakes@niglas.ac.cn©2009byJournalofLakeSciences*1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(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
2、道SC714孔2cm间隔取样和AMSC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.关键词:东江;沉积记录;粒度;磁化率;澄湖;太湖平原Grain-sizechar
3、acteristicsandtheirpaleoenvironmentalsignificanceofSC7coresedimentsinLakeChenghu,JiangsuProvince,ChinaSHIKai,DAIXuerong,SHIYuxin&YULizhong(DepartmentofGeography,SchoolofResourcesandEnvironmentalScience,EastChinaNormalUniversity,Shanghai200062,P.R.China)Abstract:ThesedimentofLakeChenghu,l
4、ocatedinthesoutheasternareaofSuzhou,ismainlycomposedof‘hardclay’(akindofsedimentconsistingofsiltandclay),andhasbeenfeaturedwithlakedepressionsandapaleo-channelinthecentralarea.Thepaleo-channel,alongthedirectionofNNW-SSE,isaccordwiththeDongjiangRiverrecordedinhistoricaldocuments,anditssed
5、imentsmaybecomegoodarchivesofenvironmentalevolutionofthehardclayplainfromrivertolake.Thegrain-size14characteristicsofcoreSC7ofLakeChenghu,AMSCandtheirmagneticsusceptibilitywereanalyzedinthispaper,thenthesedimentarycharacteristicsandpaleoenvironmentalsignificancewerediscussed.Theresultsin
6、dicatethatthesedimentsofLakeChenghumainlyconsistedoffine-mediumsiltandclay,andthepercentageoffine-mediumsiltwasabout53%-65.8%,clayabout19.7%-40.1%.Thegrain-sizeparametersofthesedimentsabove336cmwasdifferentfromhardclay,andmagneticsusceptibilitywassignificantlyhigher.Grain-sizeparametersa
7、ndmagneticsusceptibilityofthesedimentsshowthatthesedimentaryenvironmentofLakeChenghuhadexperiencedfourmainphasesfromrivertolakeaftertheformationofhard-clayplain,andalsoprovidednewevidenceforthecausesofriver-floodinglakesinTaihuPlain.Italsosuggestedthattheformationofsurfac
