2001-西宁黄土堆积记录的最近13万年高原季风气候(10)

PLATEAUMONSOONVARIATIONSDURINGTHEPAST0.13MA

INDICATEDBYLOESSDEPOSITATXINING,NORTHEAST

QINGHAI,CHINA

LuHuayu①　　MaHaizhou②③　　TanHongbing②　　LiZhen③　　MiaoXiaodong①AnZhisheng①　　WangXiaoyong①　　CaoGuangchao③　　JefVandenberghe④

(①StateKeyLaboratoryofLoessandQuaternaryGeology,InstituteofEarthEnvironment,ChineseAcademyofSciences,Xi′an710054;②InstituteofSalineLake,ChineseAcademyofSciences,Xining830008;③DepartmentofGeography,

QinghaiNormalUniversity,Xining830008;④FacultyofEarthSciences,FreeUniversity,Amsterdam)

Abstract

ClimatevariationsatXiningarea,northeastQinghai2XizangPlateauischaracteristicofalterna2tionsofplateausummerandwintermonsooncirculation,whichisgeneratedbythermodynamicandkineticeffectoftheimmenseQinghai2XizangPlateau.Themonsgeologicaltimewaspaidlessattentionpreviously.However,isforourunderstandingofclimatechangetheplateauupliftaswellastheQinghai2XizangPlateau,presentanexcellentrecordofthevariationsinthePleistoceneandeveninthePlioceneEpochs.Theloesssedimentismorethan200metersthick,intercededbypaleosols.Itwasshowedthatloesswasdepositedincold2drytime,wherethepaleosolwasdevelopedduringwarm2humidepisodes.Theloessandpaleosolformationsarecorrelatedtotheglacialandinterglacialperi2ods,respectively.

Theloess2paleosolsequenceofthelast0.13Maweresampledbydiggingditchandwellinordertoobtainun2contaminatedsamples,sincesecondaryloesscoverinthisregionisquitethicker.Theloessdeposit,locatedatlowterraceofHuangshuiRiver,wassampledatinter2valof5～10centimeter.A442mloess2paleosolprofileatTuxiangdaowassampled.Blackloamisfoundinupperpartoftheexposure,anditisregardedastypicalsedimentformedduringtheHoloceneOptimumsinNorthChina.Malanloess,whichwasformedduringthelastglacialperiodandcorrelatedtomarineisotopestage2～4,isintercededwithverythin2ner,weakpaleosols.UnderlyingtheMalanloessisreddishpaleosol,correlatedtothetimeofmarineisotopestage5.Thermoluminescence(TL)andopticallystimulatedluminescence(OSL)datingoftheloessdepositprovedthattheloesswasformedduringthelastglacialcy2cle.Inordertogetparallelrecords,wesampledaloessdepositathighaltitudeterraceatPanzishan,Xining,fromawell.Thewellis17metersindepth,andthebottomofthelastinterglacialpaleosolisat13.5mdeep.Stratigraphiccorrelationbetweentwositesisverygoodandshowstheloess2paleosoldepositwasformedduringthelastglacialcycle.Adetailedpalaeomagneticinvestigationhasn′tfoundtheBlakeexcursion.However,stratigaphiccorre2