黄土粒度分布中的超细粒组分及其成因(9)

多个剖面的粒度测量表明 ,黄土高原的黄土和古土壤中普遍存在超细粒组分 ,其平均粒径大致 014 μm,在全样中的含量大致 5%～6%。超细粒组分的含量在黄土中低 ,在古土壤中高;并且同一地层自西北至东南增加 ,这些特征都显示超细粒组分的形成与成壤作用强度相关。一般情况下超细粒组分的粒度在黄土中粗 ,在古土壤中细。

　936第　　四　　纪　　研　　究

5　SunDonghuai,BloemendalJ,

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Grain2size

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SUPPER2FINEGRAINSIZECOMPONENTSINCHINESELOESS

ANDTHEIRPALAEOCLIMATICIMPLICATION

SunDonghuai

(KeyLaboratoryofWestChinaπsEnvironmentalSystems(MinistryofEducation),CollegeofEarthandEnvironmentSciences,

LanzhouUniversity,Lanzhou730000)

Abstract

Grain2sizedatafromsectionsovertheLoessPlateauindicatethatloessandpaleosolinthatareacontain

μm,whichgenerallycomposeabout5%～6%ofthebulksupper2finecomponentswithaveragesizeofabout014

sample.Itisinterestingthatthegrainsizeofsupper2finecomponentsinloessiscoarserthanthoseinpaleosolwhiletheirproportioninloessislowerthanthatinpaleosol.Plusthattheproportionofsupper2finecomponentsinaspecificlayerincreasesfromnorthwesttosoutheastoftheLoessPlateau,wehypothesizethattheformationofsupper2finecomponentswasassociatedwithpedogensis.Supper2finecomponentsarealsofoundinpresentdustfromtheLoessPlateau,butareabsentinthedustfromaridareaofNorthwestChina.Thisprovidesfurtherconfirmationforourhypothesis.

Keywords　　theLoessPlateau,supper2finegrains,pedogensis