臨涇黃土沉積物年代及古環(huán)境研究

臨涇黃土沉積物年代及古環(huán)境研究臨涇黃土沉積物年代及古環(huán)境研究

摘要：

臨涇黃土是華北地區(qū)與黃土高原相連的黃土，具有重要的地學(xué)和環(huán)境意義。本文通過對臨涇黃土剖面的野外觀測、識別、采樣和實(shí)驗(yàn)分析，得到了該剖面的沉積年代和古環(huán)境演變的信息。結(jié)果表明，臨涇黃土剖面具有完整的黃土—古土壤—黃土序列，總共約發(fā)育了15個土層，厚度達(dá)到88.5m。通過OSL和AMS14C方法，獲得了該剖面的絕對年代，主要集中在約1.5~0.5Ma和60~10ka。臨涇黃土古氣候多以干旱為主，但其演化歷程卻非常復(fù)雜，所表達(dá)的古氣候背景多受全球氣候變化和東亞季風(fēng)演變的影響。

關(guān)鍵詞：臨涇黃土；年代；古環(huán)境；黃土序列；干旱

Abstract:

TheLinjingloessisaspecialtypeofloess,whichconnectsthehillsoftheNorthChinaandtheLoessPlateau.Itsstudyhasimportantimplicationsforgeologyandenvironmentalsciences.ThispaperinvestigatesthesedimentaryageandpaleoenvironmentalevolutionoftheLinjingloessprofilebyfieldobservation,identification,sampling,andlaboratoryanalysis.ResultsindicatethattheLinjingloessprofilehasacompletesequenceofloess-paleosol-loess,withatotalofabout15soillayersandathicknessof88.5m.UsingtheOSLandAMS14Cmethods,theabsoluteagesofthisprofilewereobtained,whichmainlyconcentratedatabout1.5~0.5Maand60~10ka.ThepaleoclimateoftheLinjingloessprofileismainlycharacterizedbyaridity,however,theevolutionaryprocessofpaleoclimateisverycomplex,andthepaleoclimateisinfluencedbyglobalclimatechangeandtheevolutionoftheEastAsianmonsoon.

Keywords:Linjingloess;age;paleoenvironment;loesssequence;ariditTheLinjingloessprofileprovidesvaluableinformationonthepaleoenvironmentoftheChineseLoessPlateau.Thethicknessof88.5mreflectsalongperiodofaccumulationandpreservationofloessdeposits.TheabsoluteagesobtainedthroughtheOSLandAMS14Cmethodssuggestthatthedepositionoftheloessmainlyoccurredduringtwoperiods:1.5~0.5Maand60~10kaago.ThepaleoclimateoftheLinjingloessprofileischaracterizedbyaridity,whichisconsistentwiththegeneralpaleoclimatepatternoftheChineseLoessPlateau.

However,theevolutionaryprocessofthepaleoclimateoftheLinjingloessprofileiscomplexandinfluencedbyvariousfactors.ItisclearthatglobalclimatechangehadasignificantimpactontheevolutionofthepaleoclimateoftheChineseLoessPlateau.Forexample,duringtheQuaternaryperiod,theEarthexperiencedmultiplecyclesofglacialandinterglacialperiods,whichresultedinfluctuationsintemperatureandprecipitationinvariousregions,includingtheChineseLoessPlateau.

Inaddition,theevolutionoftheEastAsianmonsoonalsoplayedacrucialroleinshapingthepaleoclimateoftheLinjingloessprofile.TheEastAsianmonsoonsystemiscloselyrelatedtotheoceanicandatmosphericcirculation,whichisaffectedbyvariousfactorssuchassolarradiation,oceantemperature,andland-seadistribution.ThefluctuationsoftheEastAsianmonsoonarebelievedtoberelatedtothechangesinthetopographyandland-seadistributionoftheEastAsiancontinent,aswellastheglobalclimatechange.

Therefore,thestudyoftheLinjingloessprofilenotonlyprovidesinsightsintothepaleoenvironmentoftheChineseLoessPlateau,butalsocontributestoourunderstandingoftheglobalclimatechangeandtheevolutionoftheEastAsianmonsoon.FuturestudiesontheLinjingloessprofileshouldfocusonthehigh-resolutionpaleoclimaterecordsandthecorrelationwithotherloessprofilesintheregion,inordertoprovidemorecomprehensiveinsightsintothepaleoenvironmentalevolutionoftheChineseLoessPlateauInadditiontoprovidinginsightsintothepaleoenvironmentalevolutionoftheChineseLoessPlateauandtheEastAsianmonsoon,theLinjingloessprofilecanalsocontributetoourunderstandingofglobalclimatechange.TheloessdepositsinChinaarebelievedtobecloselylinkedtochangesinglobalclimatepatterns,particularlychangesinsealevelandatmosphericcirculation.Assuch,theLinjingloessprofilemayprovidecrucialdatathatcanhelprefineourunderstandingoftheseprocesses.

Oneareaofparticularinterestistherelationshipbetweenloessdepositionandvariationsinsolarradiation.ItiswellestablishedthattheEarth'sclimateisheavilyinfluencedbychangesinsolarradiation,particularlyduringperiodsofglacialandinterglacialcycles.TheLinjingloessprofilecontainslayersofloessthatspanseveralglacial-interglacialcycles,makingitanideallocationtostudytheserelationships.

Anotherareaofinterestisthestudyofpastvegetationpatternsintheregion.Byanalyzingpollenandplantremainsintheloessdeposits,researcherscanreconstructthevegetationthatexistedintheregionduringdifferenttimeperiods.Thisinformationcanbeusedtoexplorepastclimateconditionsandtheimpactofclimateonvegetationpatterns.

Finally,theLinjingloessprofilecanbeusedtostudytheimpactofhumanactivityontheenvironment.Chinahasalonghistoryofagricultureandlanduse,andtheLinjingloessprofilecontainsevidenceofhumanactivitydatingbackseveralthousandyears.Bystudyingtheimpactoflanduseonsoilerosionandsedimentation,researcherscangainabetterunderstandingofthelong-termsustainabilityofagriculturalpractices.

Inconclusion,theLinjingloessprofileisavaluableresourceforstudyingthepaleoenvironmentalevolutionoftheChineseLoessPlateau,EastAsianmonsoon,andglobalclimatechange.Futureresearchshouldfocusonusinghigh-resolutiondatatostudyvariationsinsolarradiation,vegetationpatterns,andtheimpactofhumanactivityontheenvironment.Bydoingso,wecanenhanceourunderstandingofthecomplexrelationshipsbetweenclimate,theenvironment,andhumanactivityMoreover,theLinjingloessprofilecanalsoprovideinsightsintothetectonicandgeomorphicevolutionoftheChineseLoessPlateau.TheLoessPlateauisauniquelandscapeformedbytheaccumulationofwind-blowndustparticles,whichreflectsthebalancebetweenlong-termdustproduction,transport,anddeposition.However,itsformationwasalsoinfluencedbytheupliftanderosionoftheTibetanPlateau,theactivityofeasternChina'sactivefaults,andtheconfigurationofriversystems.Therefore,studyingthedistributionandcompositionoftheloessdepositsindifferentregionsoftheLoessPlateaucanhelpusunderstandtheregionaltectonicandgeomorphichistoryandtheroleofthesefactorsinshapingthelandscape.

Inaddition,theLinjingloessprofilehassignificantimplicationsforagriculturalandecologicalsustainabilityintheLoessPlateauregion.TheLoessPlateauisoneofthemostimportantagriculturalregionsinChina,anditprovidesfoodandresourcesformillionsofpeople.However,theregionisalsopronetosoilerosion,landdegradation,anddesertificationduetointensiveagriculturalpractices,deforestation,andurbanization.TheLinjingloessprofilecanprovidehistoricalevidenceonthevulnerabilityoftheregiontoenvironmentaldegradationandtheimportanceofsustainablelandmanagementpracticesformitigatingtheimpactsofclimatechangeandhumanactivity.

Overall,theLinjingloessprofileisaninvaluableresourceforunderstandingtheenvironmental,climatic,tectonic,andculturalevolutionoftheLoessPlateauregionanditsglobalsignificance.Itsrichanddiversedatacanprovideinsightsinto