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1、Palaeogeography,Palaeoclimatology,Palaeoecology193(2003)181^200www.elsevier.com/locate/palaeoTheDryHoloceneMegathermalinInnerMongoliaChen-TungA.Chena;,Hsin-ChiLana,Jiann-YuhLoua;1,Yan-ChengChenbaInstituteofMarineGeologyandChemistry,NationalSunYat-senUniversity,Kaohsiung80424,TaiwanbI
2、nstituteofGeologicalResearchandChemicalMines,MinistryofChemicalIndustries,Zhuozhou072754,PRChinaReceived20March2002;receivedinrevisedform2December2002;accepted12December2002AbstractThepaleoclimatesince14kyrBP(14Cage)wasreconstructedbasedona16.22-m-longsedimentcorecollectedfromLakeYanh
3、aizi,asalinelakelocatednearthenorthernlimitoftheEastAsiansummermonsooninInnerMongolia.Coarsesedimentsweredepositedthereduringashrinkagephaseofthelakewhensanddunesreactivated.Thesesedimentshaveloworganiccarboncontentsbuthighmaturityindices,indicatingthattheyweredepositedinanaridenviron
4、ment.Bycontrast,basedonhighorganiccontentsandlowmaturityindices,finesedimentsweredepositedduringperiodsofhighlakestandinahumidenvironment.Itwasingeneraldrybetween8.0and4.3kyrBP.Theabovedryandwetphasesareconsistentwiththoserecoveredfromthearid^semiaridtransitionzoneelsewhere,butareunli
5、kethewidelyperceivedhumidHoloceneMegathermalreportedineastChinaandthenewlyreconstructedrecordinthealpineRetreatLakeinTaiwan.Thediscrepancymaybeduetoarelativeinsensitivitytohumiditychangesinthesetwoareassincetheyhavebothbeenunderthetotalinfluenceofthesummermonsoon.Ontheotherhand,muchen
6、hancedevaporationoverhighermonsoonprecipitationatLakeYanhaizireducestheeffectivehumidityinthewarmclimatenearthenorthernboundaryofthesummermonsoon.Thisalsoaccountsforthefactthehigh-temperatureHoloceneMegathermal,asrevealedintheOkinawaTroughandthenorthernSouthChinaSea,iscorrelatedtothed
7、ryphasesatLakeYanhaizi.Conversely,the4^2-kyrBPcoldestperiodintheHolocenecorrespondstoawetphaseatLakeYanhaizi.ß2003ElsevierScienceB.V.Allrightsreserved.Keywords:HoloceneMegathermal;InnerMongolia;paleoclimate;EastAsiansummermonsoon;e¡ectivehumidity1.Introductioncellsgrowinganddecayingse
8、asona
