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Age and General Characteristics of the Calimicrobialite near the Permian-Triassic Boundary in Chongyang, Hubei Province

By Frank Morgan,2014-06-20 03:57
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Age and General Characteristics of the Calimicrobialite near the Permian-Triassic Boundary in Chongyang, Hubei Province

    Age and General Characteristics of the Calimicrobialite near the Permian-Triassic Boundary in Chongyang, Hubei Province JournaloJChinaUniversityofGeosciences.Vo1.17.No.2,P.121125,June2006 PrimedinChina

    ISSNJ0020705

    AgeandGeneralCharacteristicsofthe

    …一'?J?''rI1''CalimicrobialiteneartnePermtan...1riasslc

    BoundaryinChongyang,HubeiProvince

    YangHao(杨浩)

    GraduateSchoo1.ChinaUniversitYofGeosciences,Wuhan430074,China; FacultYofEarthSciences.ChinaUniversityofGeosciences,Wuhan430074,China ZhangSuxin(张素新)

    StateKeyLaboratoryofGeologicalProcessesandMineralResources, ChinaUniversitYofGeosciences,Wuhan430074,China

    JiangHaishui(江海水)

    GraduateSchoo1.ChinaUniversitYofGeosciences,Wuhan430074,China; FacultyofEarthSciences,ChinaUniversityofGeosciences,Wuhan430074,China WangYongbiao(王永标)

    FacultyofEarthSciences,ChinaUniversityofGeosciences,Wuhan430074,China;StateKeyLaboratory

    ofGeologicalProcessesandMineralResources,ChinaUniversityofGeosciences,Wuhan430074,China

    ABSTRACT:ThecalimicrobialitesofChongyang(崇阳),Hubei(

    )Province,occurabovethemass

    extinctionlineintheLatePermianreeffacies.Belowtheboundaryarethespongereeflimeston

e.crinoid

    limestoneandalgae-foraminiferbioclasticlimestoneoftheChangxing(

    )Formation.Thecalimicro

    bialitesaregenerallycomposedofmid-coarsegrainsandmicrolitecalcitewithastructureof"graniphyic

    fabric"andstromatolite.Thefossilsdiscoveredinthecalimicrobialitesincludeglobularcyanobacteria.

    ostracods.micro-gastropods,bivalves.fishteethandsomemicro-problematicalfossils.Conodontfossils

    ofHindeodusparvus.H.typicalisandH.1atidentatuswerealsofoundinthecalimicrobialites.Ac-

    cordingtotheconodonts.thecalimicrobialitesspannedthelatestPermianandearliestTriassicinthe

    ChongyangSection.TheupperpartabovethefirstoccurrenceofHindeodusparvusshouldbeattributed

    totheearliestTriassic,andthelowerparttotheChanghsingian.Thesedimentarystructure,fossilcom-

    positionandconodontzonationoftheChongyangcalimicrobialitescanbewellcorrelatedwiththecalimi-

    crobialitesfoundinotherareasofSouthChina.

    KEYWORDS:calimicrobialite,conodont,end-Permian,EarlyTriassic.Hubei. INTR0DUCT10N

    CalimicrobialitesnearthePermian-Triassic

    boundaryareaspecialsedimentaryframeworkwhich

    isformedonthetopofreefsorisolatedcarbonate

    platformsaftertheendPermianextinction.Calimi-

    crobialiteinSouthChinawasfirstfoundbyLehr-

    ThispaperissupportedbytheNationalNaturalScienceFoundationof

    China(Nos.40232025,40572002)andtheNationalScienceFundfor

    DistinguishedYoungScholars(No.40325004).

    *Correspondingauthor:2003yanghao@163.corn ManuscriptreceivedDecember5,2005

    ManuscriptacceptedMarch15.2006.

    mann(1999)inBianyang,Guizhou.Almostsimuha neously,Kershaweta1.(1999)reportedcalimicrobi

    alitesinEastSichuan.DiscoveryofPermianTriassic

    calimicrobialitesinSouthChinahasattractedmuch attention.Basedonthisformerwork,similarsedi- mentarystructureswerefoundbyWangeta1. (2005)inTiandong,Guangxi;Xiushui,Jiangxiand Chongyang,Hubei.However,nochronologically significantconodontswerefoundinChongyangat thattime.

    AllthecalimicrobialitesinSouthChinawere producedonthePermianTriassicboundary(PTB)

l22

    andtheyshouldbeproductsofthesamegeological event,accordingtotheeventstratigraphy.Howev

    er,theageofcalimicrobialitescanonlybedetermined byfossilswithchronologicalsignificance.Presently, conodontfossilsareoftenrecognizedasthekeytolo

    catethePTB:soresearchintotheirdistributionin thecalimicrobialitesisanimportantmeansofconfir

    mingtheageofthecalimicrobialitesindifferent5ec

    tions.BecausethecalimicrobialitesinSouthChina weredepositedonthetopofeitherPermianshallow

    marinereeffaciesorisolatedcarbonateplatformfaci es,conodontfossilsareusuallyveryscarce.Previous research(Iehrmanneta1.,2003;Kershaweta1.,

2002)foundHindeodusparvusinthecalimicrobial

    itesofBianyang,GuizhouProvince,andEastSi

    chuan.Similarconodontfossilshaverecentlybeen foundinthecalimicrobialitesfromChongyang,Hu

    beiProyince.

    CALIMICR0BlALITECHARACTERlSTlCS

    CalimicrobialitesnearthePTBarewidelydis

    tributedinSouthChina(Wangeta1.,2005;Fang, 2004).IntheChongyangSection,calimicrobialites havealsobeenfoundnearthePTB.ontopofthe LatePermianreef.similartothosefoundinIaolong

    dong,Chongqing(Kershaweta1.,2002).Bycon

    trast,ealimicrobialitesinBianyang,Guizhouand Pingguo,Guangxiwereonisolatedcarbonateplat forms.ThoughtheChongyangcalimicrobialitewas onthetopofareeffacies.alayerofalgaeforaminif

    erabioclasticlimestonestillexistsbetweenthetopof thereefandthecalimicrobialite.Therearetwopossi

    blereasonsforthisphenomenon:(1)thestratum outcropwaslimitedandthetopofthereefcoremay nothavebeenexposedonthesection;(2)thereef probablydisappearedearlierthanthealgae,foramini

    feraorotherorganisms.

    THESECTl0N0FCALIMICR0BlALITEIN

    CH0NGYANG

    TheChongyangSectionhasbeendescribedby Wangeta1.(2005).Furtherworkhasshownsome changesbothincalimicrobialitetypeandstructurein thissection.TheChongyangcalimicrobialiteshavea "

    graniphyicfabric"structure,whichcanbecompared withthecalimicrobialitesinGuizhouandGuangxi. Coarsecalcitesareinterspersedinthemicrolitecal

    cite,whichproducesthegraniphyicfabricstructure (Fig.1).IntheChongyangcalimicrobialites.the sedimentarystructureshowsanobviouschangefrom YangHao,ZhangSuxin,JiangHaishuiandWangYongbiao thebottomtothetop.Inthebottom,thecalimicro bialiteshavesomestromatolitestructurebesidesthe maingraniphyicfabricstructure.Thisisabout12cm thick.Abovethisaremostlygraniphyicfabricstruc

    turedcalimicrobialiteswithathicknessof56m.

    Higherup,thecalimicrobialitesaremainlycomposed ofmicrolitewithsome"graniphyicfabricstructure" calimierobialiteconglomeration.Theconglomeration sizeisaboutseveraltensofcentimeters.Atthevery topofthecalimicrobialite.thereis1.3mthicknessof grainstoneoroolite.Thisismuchlikemanyareasin SouthChina.Thegrainstoneortheoolitelimestoneis overlainbythetypicalTriassicpoorly-fossiliferouslami

    natedmicrites.Thelithologyandstratumrelationshipof thecalimicrobialitesareshownintheFig.2. Figure1.Thestructureof

    thecalimicrobialites.×4.

    "graniphyicfabric"in

    AgeLitllofaciesLithologycharactersConodonts .

    

    laminatedl

    mictites

ifer

    .

    s

    ?

    Greymidthinbeddedoolites

    Greyandblackmicrobialites,containi{{l5%-30%graniphyicfabric.1ocallythrombolitic

    lGreyandblackmicrobialites,contain

    董壁60%-90%graniphyicfabric,locallythrombolitic

    4m占謇/Greyandblackmicrobialites,withfgraniphyicfabric,locallyslromatolite

    :II-lIPTB-eventhorizOn——_JlGreyandblackbioclasticlimestone lcontainscrinoid,

    algae-foraminifer,

    II

    lthebioclasticovor8O%.

    0

    Figure2.Thecalimicrobialitestratigraphiccolumn intheChongyangSection,HubeiProvince.

AgeandGeneralCharacteristicsoftheCalimicrobialitenearthePermianTriassicBoundaryi

    nChongyang

    Theboundarybetweenthecalimicrobialitebase andthealgaeforaminiferbioclasticlimestoneiSeasily recognized.However,theremaybetwodifferentdi visionsforthetopofthecalimicrobialites.Thefirst schemeistoregardthebottomofthegrainstoneor ooliteasthetopofthecalimicrobialite.becausethe "

    graniphyicfabricstructure"ispeculiartocalimicro

    目一

    !

_

    (a)

    Huaying,Sichuan

    25

    20

    1.5

    t.0

    05

    0.0

    (b)

    Pingguo,Guangxi

    123

    bialiteandseldomseeninnormallimestone.while oolitecanbefoundnmanyplaces.ThesecondiSto definethetopofthegrainstoneortheooliteasthe topboundaryofcalimicrobialitebecauseooliteiSalso regardedasakindofcalimicrobialite(Daieta1., 1996).

    (c)

    Bianyang,Guizhou

    (d)

    Choagyang,Hube

    Figure3.ComparisondiagramofHindeodusparvushorizonofthecalimicrobialitesinSouth

    China.The

    HuayingSectionisfromKershaweta1.(2002);conodontzonesandtheBianyangSectionaref

    romLehr-

    manneta1.(2003).

    THEAGE0FTHECALIMlCROBIALITE

    Conodontfossilsarethekeyfossilsforglobal

PermianrTriassicboundarydefinitionandthefirstOC——

    currenceofHindeodusparvusiSrecognizedasthe beginningoftheTriassic(Yineta1.,2001,1986; LaiandZhang,1999).Hindeodusparvusfirstap

    pearedatthebottomofBed27ci13.theMeishanSec

    tion.However,themainextinctionhorizoniSatthe bottomofBed25.whichiSlowerthanthebiostrati

    graphicalboundary.Allthecalimicrobialitesfound SOfarinSouthChinahaveappearedimmediately abovetheextinctionboundary.butthereiSstilla distancebetweentheextinctionboundaryandtheho

    rizonofthefirstoccurrenceofHindeodusparvus (Fig.3).IntheHepingSection,thethicknessofthe calimicrobialitesiS13.5mandHindeodusparvus wasfound0.65mabovethebottomofcalimicrobial

    ite(Iehrmanneta1.,2003).InthePingguoSection inGuangxi.thethicknessofthecalimicrobialitesiS about4.6mandHindeodusparvuswasfoundabout

l24

    4

    7

    YangHao,ZhangSuxin.JiangHaishuiandWangYongbiao 2

    6

    9

    Figure4.Theconodontsinthecalimicrobialites.Occurrence:theChongyangSection,8.4ma

    bovethebot

    tomofcalimicrobialite.12.Hindeodusparvus(KozurandPiatakova,1976),1.sideview,

×200;2.

    sideview,×300;3.Hindeoduslatidentatus(Kozureta1.,1975),sideview,×

    400;4.Hindeodustypi-

    calis(Sweet,1970),sideview,×290;5.Hindeodussp.,sideview,×

    300;6.Hindeoduseurypyge

    (Nicolleta1.,2002),sideview,×240;7

    8.Hindeodusfnflatus(Nicolleta1.,2002);7.sideview,×

    300;8.sideview,×400;912.Hindeodussp.;9.Sbelement,sideview,×300;10.sideview,×250;

    11.sideview,X280;12.Scelement,sideview.X270;Bar:200ttm.

    1mabovethebase(Iehrmanneta1.,2003).Inthe HuayingshanSectioninChongqing,thethicknessis onlyabout1.4mandHindeodusparvuswasfound about1mabovethebottomofthecalimicrobialite (Kershaweta1.,2002).

    11specimensweresampledforconodontanalysis intheChongyangSectionandwell--preservedcono-

    dontfossilswerefoundonlyintheNos.34and35

AgeandGeneralCharacteristicsoftheCalimicrobialitenearthePermian

    TriassicBoundaryinChongyang

    samples(Fig.4).Bycomparisonwiththereported conodontsnearthePTB(Zhaoeta1..2005;Kozur, 2004;Nicolleta1.,2002;Yineta1.,2001;Laiand Zhang,1990),threespeciesofconodontfossilshave beenidentified.TheyaretheHindeodusparvus.H. typicalisandH.1atidentatus,Hindeodusparvus andH.atidentatuswerefoundabout8.4mabove thebottomofthecalimicrobialiteandH.typicalisat about8m.CorrelatedwiththeGlobalStratotype

    SectionatMeishan,ZhejiangProvince,thePTBof theChangyangSectionistemporarilydefinedatthe horizon8.4mabovethebottomofthecalimicrobia[

    ite.

    Amongthefoursectionsmentionedabove,

    HindeodusparvusintheHuayingshanandChong

    yangsectionsappearstobehigherabovethebottom ofthecalimicrobialitesthanintheothertwosec

    tions.Theremaybemanyfactorsleadingtodifferent distributionsofconodontfossils.Onereasonisthat theHuayingshanandChongyangsectionsarereeffa cicswhichhaveshallowerwatersthanthatofcom

    moncarbonateplatforms.Generally,conodontlos silsarenoteasilypreservedatthetopofreeffaciesin shallowwaters.Theotherreasonmayhavesome

    thingtodowiththeextentofresearch.Withmore worktobedoneontheconodontfossils,Hindeodus parvusmaybefoundatalowerhorizoninthecalimi

    crobialiteofthereeffaciessection.Nevertheless.all theHindeodusparvusfoundsofararewithintheca

    limicrobialites.Soweproposethatthelowerpartof thecaljmicrobialitesshouldbelongtotheIatePermi anandtheupperpartshouldbelongtotheEarlyTri

    assic.

    FOSSILASSEMBLAGEINTHECALIMICR0BIAL

    lTES

    Figure5.Globularbacteriaalgaefossils.

    125

    ThefossilsintheChongyangcalimicrobialiteare

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