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The first sphinctozoan-bearing reef from an Ordovician back-arc basin
Biotaandmicrofaciesofthereef.A)Polishedslabofsphinctozoan-coral-microbialboundstone.B-D)Thin-sectionsofrectanglesmarkedinA.Whitetriangles—cavities;yellowtriangles—Streptelasma;redtriangles—Palaeophyllum;S—sphinctozoan(Corymbospongia);E—Epiphyton;K—Kordephyton.Sphinctozoan(chambered)spongeswereimportantreef-buildersandcommoncryptobiontsduringthemid-latePermianandmid-lateTriassic.ThesehypercalcifiedspongescanbetracedfromtheCambrian,butitwasoncethoughtthattheywererestrictedtolevel-bottomcommunitiesuntiltheMiddlePermian.ComparetothePermianandTriassic,therewerejustsporadicandlimitedreportsofreef-buildingsphinctozoans(multi-chamberedsponges)intheEarlyPaleozoic.Recently,Dr.LIQijianfromNanjingInstituteofGeologyandPalaeontology,ChineseAcademyofSciencesandhiscolleaguesProf.LIYueandProf.WolfgangKiesslingdiscoveranoldestsphinctozoan-coral-microbialreeffromtheUpperSanqushanFormation(lateKatian)atWu’aiinZhejiang,southeastChina,whichisalsothefirstreportofOrdoviciansphinctozoansfromtheSouthChina.Thehugereef(about120mthick)ismainlyconstructedbycalcimicrobes(Kordephyton,RenalcisandEpiphyton)withasuiteofcalcareousalgae(mostlyredalga)andaccessorymetazoans(sphinctozoansandrugosecorals).Theelongatedstromatactiscavities(centimeter-scale)filledwithcementpervadeinthenon-laminatedmicrobialboundstone.Bio-andlitho-faciesinthisareaaswellasthecharacteristicsofthemicrobialiteshowthatthereefdevelopedinadeepersubtidalandstressfulsettingthatwasunfavorableformostmetazoanbuilders.Incontrasttothehigh-energystromatolite-sphinctozoanreefsintheLateSilurian,ourcaserepresentsalow-energycommunity,indicatingthatthefirstreef-buildingsphinctozoan(Corymbospongia)mighthavebeenoriginatedfromrelativelydeepenvironmentonseamountsofaback-arcbasinduringtheLateOrdovician.Theresearcharticlewaspublishedin:LiQijian,LiYue&KiesslingWolfgang,2015.Thefirstsphinctozoan-bearingreeffromanOrdovicianback-arcbasin.Facies,61(3):availableonline.(DOI:10.1007/s10347-015-0444-6)
2015-11-27
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Scientists Find the First Fossil Record of Kinorhyncha
SEMimagesofEokinorhynchusrarusgen.etsp.nov.Kinorhyncha,Loricifera,Priapulida,Nematoda,Nematomorpha,Onychophora,TardigradaandArthropodaconstitutetheEcdysozoawhichismajorpartoftheanimalworld.TheKinorhynchaincludes~240extantspeciesofexclusivelymarine,holobenthic,free-living,meiofaunalanimals.Sofar,Kinorhynchahasnofossilrecord,anditsoriginandevolutioniscurrentlyunknown.Recently,inacollaborativeresearchbyDr.ZHANGHuaqiaofromNanjingInstituteofGeologyandPalaeontology,ChineseAcademyofSciences,Prof.XIAOShuhaifromVirginiaTechandotherscientistsrecoveredthreedimensionallyphosphatizedworm-likefossilsfromearlyCambrianrocks,approximately535millionyearsold,innorthernSichuanandsouthernShaanxiProvinces.Thesenewfossilsareinterpretedasearlykinorhynchanimals,representingtheonlyknownkinorhynchfossilsintheentiregeologicalhistory.OneofthenewlydiscoveredfossiltaxaisnamedEokinorhynchusrarus,alludingtoitsrelationshipwithmodernkinorhynchsanditsrarenessinthefossilrecord.Eokinorhynchusrarusisaround2mminlengthandhas20macroannulieachbearingasinglecircletof20~40rectangularplates.Ithasfivepairsofbilaterallyarrangedlargespinosescleritesandasinglelargespinosescleriteontheventralside,eachscleritestraddlingtwoorthreemacroannuli.Therearemanysmallinternallyhollowspinesrandomlydistributedonthetrunk.Dr.ZHANGandcolleaguesfoundthatEokinorhynchusrarushasanumberofsimilaritieswithlivingkinorhynchs,suggestingacloseevolutionaryrelationship.Forexample,thetrunkofEokinorhynchusrarusandlivingkinorhynchshaveanumberofhollowspinesandaredividedintosegments,eachconsistingofarticulatedplates.However,unlikemodernkinorhynchs,Eokinorhynchusrarusisarmouredwithspinesthatarelargerandmoredistinctthanspinesonmodernkinorhynchs.Italsohasmuchmorebodysegmentsthanmodernkinorhynchs.Inlightofthesesimilaritiesanddifferences,Dr.ZHANGsuggestthatEokinorhynchusrarusmaybecloselyrelatedtotheancestorofmodernkinorhynchsandrepresentsthefirstandonlyknownfossilsofKinorhyncha.ThenewdiscoveryindicatesthatKinorhynchaemergedintheearlyCambrianandispartofthe"CambrianExplosion".ThisresearchwasrecentlypublishedinScientificReports,aNaturefamilyjournal.Relatedinformation:HuaqiaoZhang,ShuhaiXiao,YunhuanLiu,XunlaiYuan,BinWan,A.D.Muscente,TiequanShao,HaoGong&GuohuaCao,2015.Armoredkinorhynch-likescalidophorananimalsfromtheearlyCambrian.ScientificReports.Doi:10.1038/srep16521.ReconstructionofEokinorhynchusrarusgen.etsp.nov.
2015-11-27
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New progress on the study of Early Devonian graptolites in South China
SometypicalEarlyDevoniangraptolitesintheQinzhouFm.ThevastmajorityofEarlyDevoniangraptolitesarewidelydistributedwithinthe30°Nand30°Sparallelsofpaleolatitude,withonlyafewknownathigherlatitudes.OnlythreeearlyDevoniangraptolitelocations,i.e.,westYunnan,southeastGuangxi(inlowpaleolatitude),andsouthXizang(Tibet)(inmiddle-highpaleolatitude),havebeenreportedinChina.Recently,anEarlyDevoniangraptolitefaunafromtheQinzhou–YulinregioninsoutheastGuangxi,ChinaisdescribedbyAcademicianCHENXufromNanjingInstituteofGeologyandPalaeontology,ChineseAcademyofSciencesandhiscolleagues.Thisgraptolitefaunaofmoderatediversityincludes3generaand14species,with2newspecies,Uncinatograptusjadaesp.nov.andNeomonograptusaequabilislatussubsp.nov.Basedonthesetaxa,fourbiozonesintheQinzhouFormation,theUncinatograptusuniformisBiozone,thetentativeUncinatograptuspraehercynicusBiozone,thetentativeNeomonograptusfalcariusBiozone,andtheUncinatograptusyukonensisBiozone,areerectedinascendingorder.TheLowerDevoniangraptolitebiozonationinGuangxiagreeswellwiththeglobalstandard.TheresearcharticlewaspublishedinCanadianJournalofEarthSciences.Relatedinformationofthispaper:XuChen,YunanNi,AlfredC.Lenz,LinnaZhang,ZhongyangChen,andLanTang.2015.EarlyDevoniangraptolitesfromtheQinzhou–Yulinregion,southeastGuangxi,China.CanadianJournalofEarthSciences,52(11):1000-1013.doi:10.1139/cjes-2015-0025. Comparisonof6EarlyDevoniansectionsintheQinzhou–Yulinregion,Guangxi,China
2015-11-23
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Unusual Deep Water sponge assemblage was found in the Late Ordovician of South China
RepresentativetaxaoftheLateOrdoviciandeep-waterspongesfromSouthChinaTheend-OrdovicianmassextinctionistheearliestandthesecondlargestamongtheBig-fiveinPhanerozoic.ItoccurredneartheendoftheOrdovicianperiod(between445.6Maand443.7Ma),andhadadevastatinginfluenceonthemarineecosystem.Afternearly40yearsinvestigationinaglobalscale,thereisaconsensusthattheend-Ordovicianmassextinctionwasstepwiseandepisodic,andtwophaseshavebeenrecognized,withaboutonemillionyearsinbetween.Manyfossilshavebeenfoundfromtherockschronostratigraphicallycorrespondingtotheintervalfromthefirstepisodeoftheend-OrdovicianmassextinctiontothelatestOrdovician,suchasbrachiopods,trilobites,corals,graptolitesandsoon.Spongesarerareinthisinterval,andonlylithistidsandstromatoporoidshavebeensporadicallydocumented.Althoughmanynewdiscoveriesshowthatthenon-lithistidspicularsponges(especiallytheBurgessShale-typefaunas)areknownfromabroadrangeoftimes,andnotrestrictedtotheCambrian,therearestilllargegapsinthefossilrecordsofnon-lithistidspicularspongesduringtheLateOrdovician.Sofar,nospongeshavebeenreportedfromtheLateOrdovicianinChina. Recently,Dr.LILixiafromNanjingInstituteofGeologyandPalaeontology,ChineseAcademyofSciencesandhercolleaguesfromNanjingUniversityandGermanyreportauniquespongeassemblagespanningtheintervaloftheend-OrdovicianmassextinctionfromtheKaochiapienFormation(UpperOrdovician-LowerSilurian)inSouthChina.TheresearcharticlewaspublishedinScientificReports. ThisspongeassemblageareoflatestOrdovician(lateHirnantian)toearliestSilurian(earlyRhuddanian)age,justextendingacrosstheOrdovician-Silurianboundary.Itcontainsavarietyofwell-preservedsiliceoussponges,includingbothBurgessShale-typeandmoderntypetaxa.Itisclearthatthisassemblagedevelopedindeepwater,lowenergyecosystemwithlesscompetitorsandmorevacantniches.Itsexplosionmayberelatedtotheeuxinicandanoxicconditionaswellasthenoticeabletransgressionduringtheend-Ordovicianmassextinction.Theexcellentpreservationofthisassemblageisprobablyduetotherapidburialbymudturbidites. ThisunusualspongeassemblagegivesanexcellentinsightintothedeepseapalaeoecologyandthemacroevolutionofPhanerozoicsponges,andopensanewwindowtoinvestigatethemarineecosystembeforeandaftertheend-Ordovicianmassextinction.ItalsoofferspotentialtosearchforexceptionalfossilbiotaacrosstheOrdovician-SilurianboundaryintervalinChina. ThisresearchwassupportedbytheNationalNaturalScienceFoundationofChina(NSFC)andtheStateKeyLaboratoryofPalaeobiologyandStratigraphy(LPS). Relatedinformationofthispaper:LixiaLi,HongzhenFeng,DorteJanussenandJoachimReitner.2015.UnusualDeepWaterspongeassemblageinSouthChina–Witnessoftheend-Ordovicianmassextinction.ScientificReports5:16060;DOI:10.1038/srep16060.AconceptualmodelofthemigrationandtaphonomicprocessofspongesduringthelateHirnantian.
2015-11-19
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Exceptional-preserved clam shrimp eggs found from the Early Cretaceous Jehol Biota
Apaperentitled“Exceptionalpreservationofclamshrimp(Branchiopoda,Eucrustacea)eggsfromtheEarlyCretaceousJeholBiotaandimplicationsforpaleoecologyandtaphonomy”byDr.PANYanhongetal.hasbeenrecentlypublishedinJournalofPaleontology.Fossileggsofclamshrimps(Spinicaudata)arerareandlittleattentionhasbeenpaidtothestudyoftheirshapeandmicrostructures.Inthispaper,Dr.PANreportthediscoveryofexceptional-preservedthree-dimensionaleggsfromnumerousspecimensofEosestheriaellipticaChen,1976fromthelacustrineEarlyCretaceousYixianFormationinwesternLiaoning,China.Thesethree-dimensionallypreservedfossileggsdisplayasphericalshapewithsmoothsurface,partofthetertiaryenvelop,andpossiblythefirstembryoniccuticlethatwerepreviouslyunknownorambiguous.EDSanalysesofthefossilizedenveloprevealedacalciumphosphatecomposition.Thematerialnotonlyfurthersourunderstandingofthebiologyofancientclamshrimps,butalsoaddstoourknowledgeofthefossilizationprocessesthatareresponsiblefortheexceptionalpreservationoftheJeholBiota.Relatedinformationofthispaper:YanhongPan,YaqiongWang,JingengSha,andHuanyulIao,2015.Exceptionalpreservationofclamshrimp(Branchiopoda,Eucrustacea)eggsfromtheEarlyCretaceousJeholBiotaandimplicationsforpaleoecologyandtaphonomy.JournalofPaleontology,v.89,p.369-376.Doi:10.1017/jpa.2015.24． Three-dimensioanllypreservedeggsofEosestheriaellipticaChen,1976 ResultsofenergyX-rayspectrometer(EDS)forselectedpointsanalysisofelementalcompositionsandelementalmapsoftheuncoatedslice
2015-11-13
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Fusuline fauna from Tibet confirms the origin of Qiangtang metamorphic belt
TheQiangtangmetamorphicbeltcoversanarealongerthan500kmincentralQiangtangBasinfromShuanghuintheeastandGangmaCointhewest.Theoriginandformationofthismetamorphicbelthavebeenhighlycontentiousissues.Twobasicbutcontrastingmodels,respectivelythe“insitumodel”andthe“underthrustmodel”,havebeenproposedtoexplaintheformationofthisbelt.The“insitumodel”holdsthattheQiangtangmetamorphicbeltrepresentsthelocationoftheLongmuCo-ShuanghusuturezonealongwhichtheSouthQiangtangBlockwassubductedbeneaththeNorthQiangtangBlockduringtheMiddle-LateTriassic.Bycontrast,the“underthrustmodel”envisagesthatthismetamorphicbeltrepresentsthepalaeotethyanoceaniclithospherethatwasunderthrustabout200kmsouthwardsalongtheJinshasutureandexhumedintheinteriorofasingle“QiangtangBlock”.Akeymethodofexamingthevalidityofeithermodelistodeterminewhetherthelatepalaeozoicstrataandpalaeobiogeographybothnorthandsouthofthismetamorphicbeltbelongtothesameblock.Dr.ZHANGYichunfromtheLatePalaeozoicteamofNanjingInstituteofGeologyandPalaeontology,ChineseAcademyofSciencesandhiscollegueshavefoundaSphaeroschwagerinafusulinefaunaoftheAsseliantimeintheRaggyorcakaLakejustnorthoftheQiangtangmetamorphicbelt.ThediscoveryofthisfusulinefaunaconfirmsthattheNorthQiangtangBlockwaslocatedatthelowlatitudeareasduringtheAsseliantime.Bycontrast,theSouthQiangtangBlockwaslocatedatGondwananmarginthatwasinfluencedbywidespreadglacio-marinedeposits.ItimpliesthattheSouthQiangtangBlockandNorthQiangtangBlockwasnotasingleblockduringtheAsselianbutseparatedbyawidepalaeotethysOcean.Consequently,theQiangtangmetamorphicbeltwasnotoriginatedfromtheoceaniclithosphereunderthrustfromtheJinshasutureinthenorth,butfromthecollisionbetweentheNorthandSouthQiantangblocksmarkedbytheclosureofthemainPalaeotethysOceanalongtheLongmuCo-Shuanghusuturezone.ThisresearchwillbepublishedrecentlyinthejournalGeologicalMagazine. Relatedinformationofthispaper:Zhang,Y.C.,Shen,S.Z.,Zhai,Q.G.,Zhang,Y.J.,Yuan,D.X.DiscoveryofaSphaeroschwagerinafusulinefaunafromtheRaggyorcakaLakearea,northernTibet:implicationsfortheoriginoftheQiangtangMetamorphicBelt.GeologicalMagazine,inpress.doi:10.1017/S0016756815000795 SphaeroschwagerinafusulinefaunafromtheRaggyorcakaLakearea,northernTibet ThedistributionofSphaeroschwagerinaintheTethyanareaduringtheAsselian(EarlyPermian)ThediscoveryofaSphaeroschwagerinafusulinefaunafromtheRaggyorcakalakearea,northernTibetconfirmsthattheQiangtangmetamorphicbeltisnotfromtheJinshasuture
2015-11-13
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First discovery of fossil Orthoptera in Jiuquan Basin and its palaeogeographic significance
ParahaglasibiricaSharov,1968fromtheJiuquanBasinIntheJiuquanBasinofGansuProvince,northwesternChina,theLowerCretaceousXinminpu(Xinminbao)GroupconsistsoftheChijinpu(Chijinbao),theXiagouandtheZhonggouformationsinascendingorder.Abundantinsectfossilshavebeendiscoveredinthesestratasince1947whenthegiantmayflyEphemeropsistrisetalisEichwaldwasdiscoveredintheJiuquanBasin.TypicalcomponentsoftheJeholBiotahavebeenreportedfromthisbasin,includingCoptoclavalongipoda,E.trisetalisandLycoptera.Althoughthesestratahavebeenstudiedforalongtime,itsageisstillindispute.Duringthepasttenyears,ProfessorZHANGHaichunandhisresearchgroupfromtheNanjingInstituteofGeologyandPalaeontology,ChineseAcademyofScienceshaveinvestigatedthesestratainJiuquanandcollectedabundantinsectfossilsfromtheChijinbao,XiagouandZhonggouformations.Recently,postgraduateWANGHeandotherscholarsfromNIGPASfirstlyreportedfossilOrthoptera,ParahaglasibiricaSharov,1968,fromtheChjinbaoFormationintheJiuquanBasin.Thediagnosisofthespeciesisrevisedbasedonthenewspecimen.Todate,morethantenspecimensassignedtoP.sibiricahavebeenfoundintheLowerCretaceousofSiberiaandNorthChina,basedonwhichwediscussitspalaeogeographicandstratigraphicdistributions.Twopossiblemigrationpathsofthespeciesareindicatedasfollows:(1)ThisspeciesinitiallyappearedinnorthernHebeiandwesternLiaoning,ChinaatlatestintheearliestAptian,andfurthermigratednorthwestwardstoTransbaikaliaandwestwardstoGansuProvincesoonlater(early-middleAptian).(2)Oralternatively,itoriginallyoccurredinTransbaikaliaearlierthantheAptianandfurthermigratedsouthwardstonorthernChinaduringtheAptian.ThisresearchwassupportedbytheChineseAcademyofSciences,theNationalBasicResearchProgramandtheNationalNaturalScienceFoundationofChina.ThepaperwaspublishedinCretaceousResearch(WangHe,ZhengDaran,HouXudong,LeiXiaojie,ZhangQingqing,WangBo,FangYan,JarzembowskiE.A.,ZhangHaichun,2016.TheearlyCretaceousorthopteranParahaglasibiricaSharov,1968(Prophalangopsidae)fromtheJiuquanBasinofChinaanditspalaeogeographicsignificance.CretaceousResearch57:40-45).GeographicandstratigraphicdetailsoftheorthoperanParahaglasibiricaDistributionandsuggestedspreadofParahaglasibiricaintheEarlyCretaceous.
2015-10-13
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Late Pennsylvanian to Wuchiapingian palynostratigraphy of the Baode section in the Ordos Basin, North China
TheOrdosBasinissituatedinthewesternpartoftheNorthChinaCraton.Biostratigraphicstudiesmainlyforcorrelationhavebeenpromotedsincethe1980sbytheextensiveoilandgasexplorationactivityinthishydrocarbon-richbasin.However,intervalswithmarinefossilsandcorrelativehorizonsarerareintheBasin,preventingreliablecorrelationandaccurateagecalibration.Palynologyisthemostusefulbiostratigraphictoolforthisbasin,especiallytheLatePennsylvaniantoWuchiapingiandeposits,becauseoftheabundance,diversityandwidespreaddistributionofpalynologicalmaterial.ToestablishacomprehensivemiosporebiozonationwithclearlydefinedbiozonalboundariesfortheLatePalaeozoicdepositsintheOrdosBasinandtofacilitatepalynologicalcorrelationthroughouttheCathaysianpalaeofloristicregion,well-preservedmiosporesarerecordedandillustratedfromthePenchitothelowerpartoftheSunjiagouformationsintheBaodesectionoftheOrdosBasin,byDr.LIUFeng,Prof.ZHUhuaichengandProf.OUYANGShufromNanjingInstituteofGeologyandPalaeontology,ChineseAcademyofSciences.EightpalynologicalbiozonesareproposedfortheLatePennsylvaniantoWuchiapingianinterval.Amongthem,fivebiozonesarerefinedfrompre-existingbiozones.ThebiozonesarecomparablethroughouttheNorthChinaCraton.Incontrast,longdistancepalynologicalcorrelationbetweenNorthChinaandEuramericaonlyextendstotheendoftheBolsovian(earlyMoscovian).Byreferenceofassociatedmarinefossilsandmagnetostratigraphicdata,approximatestratigraphiccorrelationwiththeinternationalstagesispossibleinOrdosBasin.QuantitativeabundancesofsporesandpollenfromtheLatePennsylvaniantoWuchiapingianreflectawet-hotpalaeoclimateintheOrdosBasinbutwithanincreasingtendencyofpalaeoclimaticdryingfromtheEarlyKungurian.ThisdryingtendencycanberecognizedthroughouttheNorthChinaCratonandseemstoberelatedtothesuturingprocessbetweenNorthChinaCratonwiththecombinednortheasternChinablocks.ReduviasporoniteswhichoccursofteninrelativelyhighfrequenciesinmanyPermian–TriassicboundarysectionswasrecordedforthefirsttimefromtheearlyKungurianShansiensisBiozone.Relatedinformationofthispaper:Liu,F.,Zhu,H.C.,Ouyang,S.(2015):LatePennsylvaniantoWuchiapingianpalynostratigraphyoftheBaodesectionintheOrdosBasin,NorthChina.JournalofAsiaEarthScience,111,528-552. SelectedmiosporesfromtheShansiensisBiozone.Specimensareidentifiedbysamplenumber-slidenumber.MiosporelocationonslidesaregivenasEnglandFindercoordinatesVerticaldistributionofmiosporeBiozonesandselectedmiosporesinBaodesection,OrdosBasine,NorthChina.(Dashedlinerepresentsuncertainstratigraphicboundary.L.Sun=LowerpartofSunjiagouForamtion.)
2015-09-29
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An enigmatic Ephedra-like fossil lacking micropylar tube from the Lower Cretaceous Yixian Formation of Liaoning, China
(Left)Generalviewofthespecimen.(Middle)Detailedviewofthefemaleunitarrowedinleftfigure,showingapicalsolidprojection(arrow).(Right)Detailedviewoftheapicalprojectionarrowedinmiddlefigure,showingthethreedimensionallypreservedsolidapicalprojection.Angiospermsandgymnospermsaretwowell-separatedgroupsinseedplantsaccordingtothecurrentunderstanding.ThehugegapbetweenthesetwogroupsconstitutesaseriousthreatagainsttheDarwinism,whichexpectsacontinuoustransitionalseriesbetweenthem.TheLowerCretaceousYixianFormationofLiaoning,Chinaisfamousforitsmegafossilangiosperms,includingsomeearlyangiospermsandputativegnetaleanplants.Recently,ProfessorLIUZhongjianfromNationalOrchidConservationCenterofChinaandProfessorWANGXinfromNanjingInstituteofGeologyandPalaeontology,ChineseAcademyofSciencesdocumentanotherEphedra-likefossilplant,Pseudoephedran.gen.n.sp.,fromtheYixianFormationonthebasisoflightmicroscopic(LM)andscanningelectronmicroscopic(SEM)observations.AlthoughitsgeneralmorphologydemonstratesagreatresemblancetoEphedra,theexpectedmicropylartubecharacteristicofEphedraismissinginPseudoephedra.Insteadasolidprojectionisseenonthetopofthefemaleparts.SuchapuzzlingcharactercombinationmakesPseudoephedraperplexinginseedplantphylogeny.IfputinEphedraceae(Gnetales),Pseudoephedrawoulddestroytheonlysynapomorphy(micropylartube)oftheBEGclade.Ifputinangiosperms,Pseudoephedrawouldbridgetheformerlyhugegapbetweengymnospermsandangiosperms.Apparently,furtherinvestigationisneededtoclarifythepositionofPseudoephedra.Relatedinformationofthispaper:Liu,Z.-J.andWang,X.,2015.AnenigmaticEphedra-likefossillackingmicropylartubefromtheLowerCretaceousYixianFormationofLiaoning,China.Palaeoworld.
2015-09-25
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New progress on the study on Ordovician of South China
ThePagodaFormationisauniqueOrdovicianstratigraphicunitonSouthChinaPaleoplate,andextendswidelyontheYangtzePlatformforover2000kmfromeasttowestand800kmfromnorthtosouth.ThiscarbonateunitdepositsduringtheearlyLateOrdovician,withvariablethicknessesfrommeterstoahundredmeters,andthePagodanetworkstructurehasbeenpuzzlinggeologists,especiallypaleontologists,aboutitsoriginfornearlyacentury.Ithasbeeninterpretedvariouslybydifferentresearchersandputativelyasdesiccationcracks,subaqueousshrinkageorsyneresiscracks,biogenictraces,tectonicfracturingorloadingstructures.TheresearchersonOrdovicianfromNanjingInstituteofGeologyandPalaeontology,ChineseAcademyofSciences,incollaborationwithsedimentologistsandpaleontologistsfromPekingUniversityandWesternUniversity,Canada,havebeencarryingoutthesedimentologicalandpaleontologicalstudyforovertenyears.AndtheirinvestigationshowsasignificantregularityonthelateralandverticaldistributionofthePagodaLimestone’slithologicfeatures,thickness,faunadevelopmentetc.,andthesocalled“time-specific”networkstructurealsochangesinitsmorphologywiththechangeofpaleogeographicbackground.Inlaboratory,bycombiningtheresultsofpaleontology,sedimentology,geochemistry,regionaltectonicsetc.,theresearchgroupputforwardanewexplanationontheoriginoftheUpperOrdovicianPagodaFormationwithnetworkstructureinSouthChina.Such"time-specific"networkstructureisexplainedasaspecialkindofmeganodules.Itsformationrequirespecificpaleogeographicbackground,soSouthChinaPaleoplatemightbelocatedwithinequatorialzone(themainbodyofSouthChinaPaleoplatelocatedwithin10°southandnorthofthethenequator).ThisconclusionfurthersupportsaspecificpositionforSouthChinaduringtheLateOrdovicianandearlySilurian,wheremightbeoneoftheradiationcentresintheporcessoftheGreatOrdovicianBiodiversification.Relatedinformationofthispaper:ZhanRenbin,JinJisuo,LiuJianbo,PatriciaCorcoran,LuanXiaocongandWeiXin.2015.MeganodularlimestoneofthePagodaFormation:Atime-specificcarbonatefaciesintheUpperOrodovicianofSouthChina.Palaeogeography,Palaeoclimatology,Palaeoecology. Fig.1.A:DistributionoftheUpperOrdovicianPagodaFormation,withvariablethicknessesoftheformationdepictedbycirclesofdifferentsizes(upto90m);B:modernfrequencyandintensitymapofhurricane/cyclonetracks,noappearanceofthestrongconvectionweatherabovewithin10°oftheequator;C:theproposedpaleogeographicpositionofSouthChinaduringLateOrdovician,straddledtheequator,lackingofhurricanesandstorms,providingwellbackgroundconditionstotheformationofPagodameganodularlimestone.Fig.2.GeochemicalanalysesofnoduleandcrackofthePagodaLimestone,showingconsistentdifferentiation(ornot)ofC,OandICP-MSelementalcontentsbetweenthem,provingthisnewexplanationofthePagodaLimestone. Fig.3.Comparisonofdifferentkindsofnodularlimestone(C,D,meganodularlimestone,PagodaFormation)andtheirinterpretedorigins(E,F,FshowingtheoriginofthePagodaLimestone).Scalebars=10cm.
2015-09-23