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Mesozoic-Cenozoic Basin Features and Evolution of Southeast China

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Mesozoic-Cenozoic Basin Features and Evolution of Southeast China

    Mesozoic-Cenozoic Basin Features and

    Evolution of Southeast China

    Vo1.81No.4PP.573-586ACTAGEOLOGICASINICAAug.2007

    Mesozoic-CenozoicBasinFeaturesandEvolutionofSoutheastChina

    SHULiangshu',ZHOUXinmin,DENGPingandZHUWenbin

    1StateKeyLaboratoryforMineralDepositsResearch.DepartmentofEnrthSciences, NanjingUniversity,Nanjing210093,China

    2InstituteofGeology,ChineseAcademyofGeologicalSciences,BeijinglO003ZChina Abstract:TheLateTriassictoPaleogene(T

    E)basinoccupiesanareaof143100km2,be.mgthesixth

    areaofthewholeofSEChina;thetotalareaofsynchronousgranitoidisabout1273O0km:itprovides

    akeyforunderstandingthetectonicevolutionofSouthChina.Fromanew1:1500IOOgeologicalmapof

    theMesozoic-CenozoicbasinsofSEChina.combined,thanalysisofgeometricalandpetrological

    features,somenewinsightsofbasintectonicsareobtained.Advancesincludepetrotectonicassemblages,

    basinclassificationofgeodynamics,geometricfeatures,relationsofbasinandrange.Accordingto

    basin-forminggeodynamicalmechanisms,theMesozoic-CenozoicbasinofSEChinacanbedivided

    intothteetypes,namely:1)para-forelandbasinfotinedfromLateTriassictoEarlyJurassic(T_J1)

    undercompressionalconditions;2)riftbasinsformedduringtheMiddieJurassic(J2)underastrongly

    extensionalsetting;and31afaulteddepressionformedduringEarlyCretaceoustoPaleogene

(KI-E)

    underback-arcextensionaction.Fromtherockassemblagesofthebasin.thefaulteddepressioncanbe

    subdividedintoavolcanic-sedimentarytypeformedmainlyduringtheEarlyCretaceous(K1)andared

    -

    bedtypeformedfromLateCretaceoustoPaleogene(K2-E).Statisticaldatasuggestthattheareaofall

    para-forelandbasins(T3__J1)is15120kmz,oneofriftbasins(J2)occupies4640km2,andallfaulted

    depressionsequalto124330kmincludingtheK2

    _Ered.bedbasinsof37850km.TheEarlYMesozoic

    (TJ1)basinandgraniteweremostlyco-generatedunderapost-collisioncompressionbackground.

    whilethebasinsfromMiddleJurassictoPeogene(JrE)weremainlyconstralnedbyregional extensionaltectonics.Threegeolo#calandgeographicalzonesweresurveyed,namely:1)theWuyishan

    separatingzoneofpaleogeographyandclimatefromM-ddieJurassictoTertiary;21theM-ddie

    Jurassicriftzone:and3)theGanjiangseparatingzoneofLateMesozoicvolcanism.Threetypesof

    basin-graniterelationshipshavebeenidentified,includingcompressional(afew1)'strike.sHp(afew),

    andextensional(common).Athree?stagegeodynamicalevolutionoftheSE.Chinabasinismooted:an

    EarlyMesozoicbasin-graniteframework;atransitionalMiddleJurassictectonicre#me; intracontinentalextensionandred-bedfaulteddepressionssincetheLateCretaceous. Keywords:basin-granitetectonics,geodynamicalevolution,Mesozoic-Cenozoic,paleogeographic-

    paleoclimaticsettings,SEChina

1Introduction

    Mesozoic-Cenozoicintracontinentalbasins,situated onthewesternmarginofthePacificOceaninSEChina (F1),consistoffourphasebasin,namelytheLate

    TriassicEarlyJurassic(T3_J1),theMiddleJurassic(J2), theEarlyCretaceous(K1)andtheLateCrctaceous- Paleogene(K2-E).TheresidualLateTriassicandMiddle Jurassicbasinscontainreservesofimpo~antcoalbeating

    sequencesandabundantcoalresources(Xueta1..1984; Correspondingauthor.E-marl:lsslu2003@yahoo.com.cn RenandChen,1989;NIGMR,1987).Variousbasinsand graniticmountainrangesconstituteadistinctivebasin

    granitelandscape(Shueta1.,2004),whichhasbeencalled theSouthChinaMesozoicBasinRangeTectonicsfGilder

    eta1.,1991,1996;Li,2O00).ThesmallscaleresidualT

    J1basinsandgranitesdatedat240205Maareexposedin

    theintralandareas(Cheneta1.,2002:Shueta1.,2004; Zhoueta1.,2006);largescaleKlvolcanicaccumulated

    depressionsfollowedbygraniticcomplexesoccupytheSE Chinacoastalregion(Jahneta1.,1990;ZhouandLi,2000: Wangeta1.,1990;Lapierreeta1.,1997;Xueta1.,1999;

574Mesozoic-CenozoicBasinFeaturesandEvolutionofSoutheastChinaShuetal

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    lb0.1.0.1:!O.l30~faultzone

    Fig-1.TectonicframeworkofSEChina(modifiedfromErnst,1983;Faureeta1.,

1989;GeologicalSurveyofJapan,1992;He,1994;Grosvenoreta1.,1995;Charvetet

    a1.,l999;Reneta1.,1999;ShuandZhou.2002). ?Jiangshan

    -

    Shaoxing.Pingxiangfaultzone;?Lishui?Zhenghe?Dapufaultzone;?Changle.Nan'at faultzone;?Ganjiangfaultzone;?Tan.Lufaultzone;?Sihui.Wuchuanfaultz0ne. Niuetal2004);andtheK2-Ered.beddepressionsare distributedonlyonthenorthernandwesternsidesofthe WuyiMts.

    nepetrotectonicunitsoccurinthestudiedregion. namelytheJiangnanNeoproterozoicorogen,theSouth ChinaEarlyeozoicorogen,andtheSE.Chinacoastal LateMesozoicvolcanic.intrusioncomplexzonewitha stronggravitationalanomaly(Yaneta1.,2004).The WuyishanEarlyPaleozoicorogenisdelineatedbetween tworegionalscalefaultzones:theShaoxing.Jiangshan. Pingxiangfaultzonetothenorth(ShuandCharvet1996; Shueta1.,2006),andtheLishui.Zhenghe.Dapufaultzone tothesoutheast.TheNNEtrendingGanjiangfaultzoneis thewesternboundaryofLateMesozoicvolcaniczone (ZhOHandLi,2000).SincetheLateTriassic.SEChina hasbeeninaterrestrialenvironmentwherethemedium. smallscalebasinsandgranitesarewelldeveloped(Shu andCharvet1996;Shueta1.,2003:Wangeta1.. 2000;

    WangandZhou,2002).ResidualMesozoicCenozoic

    basinsaredistributedmainlyintheSE.Chinaregion:the coastal,GanzhouHangzhou,Ganjiang,EasternNanling, WuyishanandChangde.Luxizones(Fig.2,.

    TheMesozoic-Cenozoicbasinsoccupyanactualarea

of143100km2,equaltoone.sixththeterrestrialareaof

    thewholeofSEChina,thuspresenting akeytounderstandingthetectonic evolutionofSouthChina.Although studiesonthecompositionand

    geologicalbackgroundofthese Mesozoic-Cenozoicbasinshavebeen done(RenandChen,1989;Reneta1., 1998;Gildereta1.,1991),thegeometry andgeodynamicsofthebasinsarestill poorlyunderstood.Thetempora1. spatialrelationshipsbetweenbasinand granitehasrarelybeenstudied,andthe statisticaldataforsize,number,actual areaanddistributionofthebasinshave notbeenpublishedwithalackofa precisebasindistributionmap.Inthe pastfiveyears,combiningfield investigationwithstructuraland petrologicalanalysis,theauthors cardedoutasystemicstudyof

    geometricfeaturesandgeodynamic evolutionoftheSE.Chinabasin,and compiledageologicalmap

    (1:1500000).Thispaperwillpresent theseresults,providingnewevidence fortheMesozoictectonicevolutionof SEChina.

    2GeologicalfeaturesoftheMesozoic. Cenozoicbasins

2.1Threetypesofbasin

    SincetheLateTriassic,SEChinahasbeendominatedby fluvialandlakeenvironmentsexceptforthewesternFuiian andnorthernGuangdongsegmentswhereathinsuccession ofshallowsea-shoresedimentswasdepositedduringtheT -

    Jl(FBGMR,1985;GBGMR,1988;HBGMR.1988;

    JBGMR,1984).FollowingAllenandAllen(1990).we divideSEChinabasinintothreetypes:para.forelandbasin. riftbasin,andfaulteddepression.

    Para-forelandbasinTheso.calledpara.forelandbasin (Cheneta1.,1996)hasasmallersize(decadeskmfor singlebasin)andisthinner(1essthan2000m1,compared withtheforelandbasinbuttheyhaveasimilartectonic location(foothil1),composition(molasses),and background(compression).TheT3-Jlpara.forelandbasin ofSEChinaresultedfromtheloadofoverlappingthrust slabsduringpostcollision.Thistypeofbasinextendsin thesubEWdirectiontothewestoftheGanjiangfault. andextendsalongtheNEdirectiontotheeast.Deposits

    haveirregularandcoarsefragmentsinthelowerpart,and finesiltstoneandmudstoneintheupperpart(Fig.3B.C.

    Vo1.8lNO.4ACTAGEoLoGICASINICAAug.2007575 Fig.2.GeologicalmapoftheMesozoic-CenozoicbasinintheSEChinaregion.

    ?JiangshanShaoxingPingxiangfaultzone;?LishuiZhengheDapufaultzone;?ChangleNan'aofaultzone;?Ganjiangfaultzone;?SihuiWuchuanfault

    ZOne

    D,F,G),indicatingafluvialtolacustrineenvironment.In

theverticalsection,thebottompartispurplegray

    molassesoverlyingPermianlimestoneandfragmentary rocks(Fig.4),andupwardstherearegraywhitecoarse

    feldsparquartzsandstone,sandstone,coalbearing

    siltstoneandmudstone.

    TheLateTriassicSeriesoftheparaforelandbasinis

    calledtheAnyuanFormationinnorthernJiangxi(Fig.4; JBGMR,1984);theJiaokengFormationinsouthwestern Fujian(FBGMR,1985);theWuzhaoFormationin

    Vo1.81No.4ACTAGEOLOGICASINICAAug.2007577 CoarsesandstoneLimestoneQuartzsandstone

    Mudstone&siItstoneMarliteConglomerate

    Fig.4.LateTriassicmolasseoverlyingPermianstratain Shanglivillage,PingxiangCity,JiangxiProvince. Pl,MaokouFormation;P21,LepingFormation;T3a,Auyuan Formation.

    southerrlZhejiang(ZBGMR,1989);theWenbinshan FormationineasternGuangdong(GBGMR,1988);the ShenkouGroupinnorthernGuangdongSOUthemHunan

    (GBGMR,1988;HBGMR.1987);andtheShaowushan GroupinwesternGuangdong(GBGMR.1988).Thenanle oftheEarlyJurassicSeriesistheLinshanFormationin thewholestudiedareas.TheT3-J1rocksunconformably overliethepreMesozoicbasement,andsometimes,

    contactwiththebasementbyanormalfault(Fig.3E,G). basinThisbasinwasformedduringJ,andis

exposedmainlyinthewesternFujiannorthernJiangxi

    northernGuangdongsouthernHunanzone(Fig.5).Most

    basinsextendinthesubEWdirection.whilethe

    DongkengLinjiangandRuchengbasins(Fig.2,Fig.5) aledistributedinthesubS.Ndirection.Bothboundaries

    oftheriftbasinalepulledtowarditscenteralongnormal faults,formingadeepsubsidence.Thebimodalvolcanic rocks,tholeiites,Aqpegranitesandagabbrogranite

    syenitesuite.whicharedatedat160180Maarewell

    developedintheDongkengLinjiangBasin(Li,2000;Li

    eta1.,2003:Cheneta1.,2002).

    FaulteddepressionSincetheEarlyCretaceous,the wholeofSEChinahasbeenunderanextensional background,formingnumerousextensionaltypefaulted

    depressions.totaling123340km.86.2%oftheareaofthe wholeMesozoic-Cenozoicbasin.

    Thefaulteddepressioncanbesubdividedintotwosub

    types.Oneiscalledthepurplecoloredvolcanic

    sedimentaryfaulteddepression.whichiscomposedof EarlyCretaceousrhyolite,weldedtuif,greenbasalt,dacite andsedimentaryrocks(Fig.2,Fig.3B,F,G);theseoften coexisttogetherwithagranitethatisdatedat140-105 Ma(Zhoueta1.,2006).ZhouandLi(2000)usedthe modelofplatesubductionplusbasalticunderplatingto interpretthegeodynamicgenesisoftheK1volcanic

    graniticcomplexesinSEChina.Theothertypeisthered

    bedfaulteddepressionthatconsistsofLateCretaceous- Paleogenegypsumsaltbearingsandstone,siltstoneand mudstonewitholivinebasaltintercalationsfFig.3B)dated

at994MabyzirconUPbSHRIMP(Shueta1.,2004;

    Yueta1..2004).Inthecoastalareas,graypurple

    conglomerateandcoarsesandstonearedevelopedinthe bottompartoftheUpperCretaceousSeries(Fig.3B), indicatingashort-timeupliftingevent,correspondingto thecollisioneventinSWJapandatedat10285Ma

    (Ichikawaeta1.,1990).

    Mostfaultedbasinsshowanasymmetrichalf-grabenor

    shape,namely,onesideofbasinisborderedbya dustpan

    steepnormalfaultandtheothersideisanangular unconformity(Fig.3A).Thestratadipisalwaystoward themalndetachedfaultandthestrataarethickestnearthe

    mainfault.Thefaultedbasinsaredevelopedmainlyonthe preJurassicbasement.Sometimes,theyconstituteapart ofthemetamorphiccorecomplexorthemagmaticthermal dome,suchasatWugongMts(Faureeta1.,1996;Shuet a1.,1998)andZhuguangMts(Shueta1.,2004). 2.2Sizeanddistributionofbasin

    TotalareaofbasinTheageofthebasinisconstrained bythestandardfossilsandtheagedataoftheigneous rocks.Statisticalresultsfroml10geologicalmaps (1:200o00)demonstratethatthetotalareaofthebasin fromLateTriassictoNeogeneis143100km.occupying onesixthoftheterrestrialareaofthewholeofSEChina, similartothetotalareaofgraniteformedinthesame period,127300km(Zhoueta1.,20o6).

    TheTrJ1basinItsactualareais15120km,

    occupying10.6%ofthewholebasin.alittlelargerthan theareaofcoevalgranites,14300km.MostoftheTs-J1

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