Late Silurian (Ludlow) and Early Devonian (Pragian) conodonts from the Cobar Supergroup, western New South Wales, Australia

Bulletin of geosciences

Mathieson D¹  Talent JA¹  Simpson AJ¹  Mawson R¹ 

关键词: Australia;    New South Wales;    Cobar Supergroup;    late Silurian;    Early Devonian;    conodonts;    conodont phylogeny;    Darling Basin;   

DOI  :  

来源: Czech Geological Survey

【 摘 要 】

LateSilurianandEarlyDevonianconodontsaredocumentedfromoutcroppinglimestonesatnineCobarSupergrouplocalities:theBoothLimestone,theMountainDamLimestone,theBelouraTankLimestoneMemberoftheBaledmundFormation,the“LeridaLimestoneMember”oftheAmphitheatreGroup,andlimestonesinStoneyCreekintheGundabookaNationalPark,intheTroffsFormationintheTrundleGroupandintheDerriwongGroupatMyola.These(withtheexceptionofMyola)andconodontspreviouslydocumentedfromtheWhiteTankandRookerylimestonemembersoftheMeryulaFormationarePragianinage,rangingfromsulcatusZonetotheimpreciselydefinedpireneaeZone,withtheuppermostpartofoneofthem(theBoothLimestone)possiblyextendingintotheearliestEmsian.TheDerriwongGroupcarbonatesarelateLudfordian,crispaZone,inageandaretheonlyremnantsdiscoveredtodateofaSilurianmarineincursion.AgesfortheDevonianlimestonesare:BoothLimestone,lateinthesulcatusZoneto“pireneaeZone”withtheuppermosthorizonpossiblyextendingintothedehiscensZone;MountainDamLimestone,sulcatusZonewiththeuppermostpreservedhorizoninferredtohavebeenlateinthesulcatusZone;theBelouraTankLimestoneMember,sulcatusZone;the?olistolithsconstitutingthe“LeridaLimestoneMember”,sulcatusZone;andlimestonesinStoneyCreekintheGunderbookaNationalPark,“pireneaeZone”.Conodontspreviouslydocumentedfrom“TheRookery”-theWhiteTankandRookerylimestonemembers-areinferredtobesulcatusZone.Intermsofrecentlyrefinedabsoluteages,DevoniancarbonatesedimentationintheCobarSupergroup,thoughlocalised,thusspansasix-or-seven-million-yeartimeslice.TheDevonianlimestonesinvestigatedwereapparentlydepositedduringasingle,basin-widesedimentaryeventthatwasconducivetoaccumulationofcarbonatesedimentsatvariousloci.SeveralconodontspeciesdocumentedherearetaxafoundinCentralAsiaandArcticNorthAmericanlocalities.Previousexamplesofsuchapparentprovincialism,basedonconodontdistribution,havebeennotedtooccurinfaunasfromthepesavisandkindleizones,theimpreciselydefinedpireneaeinterval,andnowforthesulcatusZone.AplethoraofnewspeciesandsubspeciesidentifiedfromtheCobarSupergrouplimestonesappearinthemiddletolateportionofthesulcatusZone,anintervalfromwhichconodontshavenotbeendocumentedascopiouslyasfromothertimeslotsglobally.Newconodonttaxaconsistofonenewgenus,eightnewspecies-onekeptinopennomenclature-andsixnewsubspecies:Heliagnathusgen.nov.(typespeciesHeliagnathusparvilabiatussp.nov.),Panderodusrhytiodussp.nov.,Panderodussp.nov.A,Icriodusampliatussp.nov.,Pelekysgnathusinaequalissp.nov.,Oulodusastriatussp.nov.,Ozarkodinamultistriolasp.nov.,Ozarkodinascoliciformissp.nov.,Amydrotaxiscorniculanstruncussubsp.nov.,Eognathodussulcatuslaneisubsp.nov.,Eognathodussulcatussicatussubsp.nov.,Ozarkodinaselfilenticulasubsp.nov.,Ozarkodinaselfilanceolasubsp.nov.andOzarkodinaselficordatasubsp.nov.BiostratigraphicdatafromthisstudyindicateaseparationintherangesofOzarkodinaselfiandEognathodussulcatus.ApolyphyleticoriginofEognathodusissuggested.BiometricdataarepresentedtodemonstratethatIcriodusampliatussp.nov.occupiesamorphologicalgapbetweenI.steinachensisandI.claudiaeanditsfirstappearanceisamarkeroftheuppersulcatuszone.

【 授权许可】

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