Xie2013GeologyDJHarchaeology

Geologydoi:10.1130/G34318.12013;41;827-830Geology ZhuMeyers,LinfengGong,ChaoyongHu,JunhuaHuang,ShihongZhang,YanshengGuandJunyingShuchengXie,RichardP.Evershed,XianyuHuang,ZongminZhu,RichardD.Pancost,PhilipA. stalagmiterecordsandtheirimpactsonprehistoricculturesincentralChinaConcordantmonsoon-drivenpostglacialhydrologicalchangesinpeatand  Emailalertingservicesarticlescitethisarticletoreceivefreee-mailalertswhenne://©2013GeologicalSocietyofAmericaonJuly22,2013geology.gsapubs.orgDownloadedfromGEOLOGY|August2013|ficproxiesofmonsoonalrainfallarelimited.Wepresentheretwonewindependentproxyrecordsfrompeatlandandstalagmitearchivesthatindicateahighdegreeofconcordancebetweenmonsoon-drivenhydrologicalchangesoccurringsincethelastdeglaciationinabroadregionofcentralChina.ThewetperiodselevatedthewatertableintheDajiuhupeatland,asrecordedbyreducedmassaccumulationratesofhopanoids,biomarkersforaerobicmicrobes,confirmedbymolecularphylogenicanalyses.Thehopanoid-basedreconstructionissupportedbythefirstreportoftheenvironmentalmagnetismparameterARM/SIRM(anhystereticremanentmagne-tization/saturationisothermalremanentmagnetization;ratiooffinemagneticparticlestototalferrimagneticparticles)inastalag-mitefromHeshangCaveincentralChina.HeavyrainfallresultedintheenhancedtransportofcoarseparticlestothecaveandthuslowARM/SIRMvaluesinthestalagmite.Thehydrologicalcondi-tionsinferredfromthetworecordsrevealthreerelativelylongwetperiodsincentralChina:13–11.5k.y.ago,9.5–7.0k.y.ago,and3.0–1.5k.y.ago.ArchaeologicalevidenceforthehydrologicalimpactsonregionalpopulationscomesfromtheobservationthattemporalshiftsamongsixdistinctiveculturesoftheNeolithicPeriodtotheIronAgeincentralChinaoccurredduringwetperiodsorfloodepisodes.Spatiotemporaldistributionsof1600prehistoricsettle-mentsitescorrelatewiththeproxy-inferredfluctuatinghydrologicalconditions,withenhancedfloodingriskforcingmajorrelocationsofhumansettlementsawayfromriparianzones.INTRODUCTIONVariationsintheAsianmonsoonhaveattractedincreasingatten-tioninrecentdecadesbecauseofgrowingappreciationoftheirimpactsonhumanlivesandeconomiesinthepast,present,andfuture.Arecentinvestigationofcaveδ18OrecordsinnorthChinaledtothesuggestionthatdecreasedambienttemperature,resultingfromweakeningofthesummermonsoon,wasthemaincauseforthecollapseofancientcul-tures(Zhangetal.,2008),althoughtheδ18Orecordsfromindividualsta-lagmitesarelikelyinfluencedbymultipleprocesses(Dayemetal.,2010;Pausataetal.,2011).Giventhatancientanthropogenicactivitieswouldhavebeenconcentratedpredominantlyinlowlandareasofmajorrivercatchments(Iriarteetal.,2004),ancientcivilizationsintheseregionswouldhavebeenmoreresponsivetoriskfromincreasedfloodingthantemperaturechanges.Therefore,weexploreheretheimpactofthemon-soon-drivenhydrologicalconditionsonancientcivilizations,focusingonthemiddlereachesoftheYangtzeRiverincentralChina.Thisregionisnotonlypronetoextremedroughtandfloodingduetomonsoonalvariations(Anetal.,2000),butalsohasanexceptionallyrichhistoryofancientculturesandsettlementscoveringaperiodofmorethan5000yr(LiuandChen,2012).Regionalpaleohydrologicalreconstructionisextremelychalleng-ingbecauseofthescarcityofproxiesofancienthydrologicalconditions(Boothetal.,2004).Moreover,thewidespatialvariabilityinhydrologi-caleventsnotonlyleadstohydrologicalconditionsbeyondthepredic-tivecapabilitiesofthepresentgenerationofgeneralcirculationmodels,butalsocausesdifficultiesindeconvolvingregionalfromlocalsignals(Barberetal.,2000).WepreviouslyestablishedtheHoloceneprecipita-tionhistoryinsouthChinabycomparingthedifferenceinoxygenisotopecompositionfromtwospatiallyseparatedstalagmites(Huetal.,2008).WenowreconstructthehydrologicalconditionsincentralChinausingtwonewindependentproxies,theaerobicmicrobialbiomarkersfromapeatdepositandtheenvironmentalmagnetismparameterinastalagmite.MATERIALANDMETHODSTheaerobicmicrobialbiomarkerrecordforpaleohydrologicalcon-ditionsisderivedfromtheDajiuhupeatland(31°28′50″N,110°00′09″E),alargefenlocatedintheShennongjiaMountainsnorthofthemiddleYangt