Dapingian-lower Darriwilian (Ordovician) stratigraphic gap in the Faraghan Mountains, Zagros Ranges, south-eastern Iran

Bulletin of geosciences

Popov LE¹  Ghobadi Pour M¹  Tolmacheva TY¹  Ehsani M-H¹  Álvaro JJ¹  Ghavidel-Syooki M¹ 

关键词: chitinozoans;    conodonts;    acritarchs;    brachiopods;    stratigraphy;    Gondwana;   

DOI  :  

来源: Czech Geological Survey

【 摘 要 】

TheLower-MiddleOrdoviciansedimentsexposedintheFaraghanMountains,south-easternZagrosRanges,representacondensedsuccessionofsiliciclastic-dominatedrocksrichinpalynomorphassemblages(acritarchsandsubsidiarychitinozoans)andsparseshellyconcentrationsbearingbiostratigraphicallysignificantbrachiopodsandconodonts.TheLowerOrdovicianZard-KuhFormationcomprisescoarse-grainedsiliciclasticdepositsrichinCruzianaichnofossils.Thelower80moftheoverlyingSeyahouFormation,lateFloiantoKatianinage,formaheterolithicsuccessioncomposedofblackandgreenshales,subarkosesandsiltylimestones.Itslowerpartispunctuatedbyacentimetricphosphoarenitethatcontainslingulatebrachiopods(Atansoriayaserisp.nov.)andconodonts(Baltoniodusaff.B.triangularisLindstrouml;mandDrepanoistodussp.)thatsuggestalatestFloianage.ThetopofthecondensedphosphoareniteismarkedbyaconsiderablehiatusthatrangestheDapingianandearlyDarriwilianinterval.Overlyingthehiatus,theSeyahouFormationcomprisestwofossiliferouslevels,theoldestdatedasmid-DarriwilianwithchitinozoanscharacteristicoftheSiphonochitinaformosaZone,andtheyoungestoftheKatianAcanthochitinabarbataZone.MidOrdovicianphosphogenesisassociatedwithstarvation,reworking,resedimentation,andtheonsetofdistinctstratigraphicgapswasacomplexprocessrecordedthroughouttheArabianmarginofGondwana.IntheZagrosRanges,maximumfloodingandphosphateprecipitationaresuggestedasthecounterpartoftheHelskjerDrowningEventofBaltoscandiaandthethird-ordermaximumfloodingsurfacethatpunctuatestheSiphonochitinaformosaZoneinNorthAfrica.

【 授权许可】

Unknown