Lower to Middle Ordovician trilobite faunas along the Ural border of Baltica

Bulletin of geosciences

Pärnaste H¹  Bergström J¹ 

关键词: Ordovician;    trilobites;    Urals;    Baltica;    palaeogeography;   

DOI  :  

来源: Czech Geological Survey

【 摘 要 】

RecentrevisionoftheOuml;landiantrilobitefaunasinBaltoscandiaandtheUralMountainsthrowsnewlightonthedevelopmentofthetrilobitefaunasinBalticaandpossiblemigrationlinkstosurroundingterranes.Thetrilobiteassemblagesof104generaontheUraliansideofBalticashowdifferentdevelopmentpatternsforthesouthandnorththroughtheTremadociantotheDarriwilian.TheoldestUraliantrilobites-disputablyoflatestCambrianorearliestOrdovicianage-arrivedprobablyfromtheSiberianandKazakhterranesbeingrepresentedbymostlyendemicgenerasuchasKujandaspisandJdyia,butalsowithpandemicAkoldinioidiaandMicragnostus.ThefollowingKidryasian,KolnabukianandKuagachianfaunaschangegraduallytoshowincreasingdifferencebetweenthesectionsintheSouthUralsandthoseinthenorthernPolarUralsorPay-Khoy.InKidryasiantheolenidsdominateintheSouthUralsastheydoinmanyotherregionsduringtheearlyTremadocian.TheKolnabukiantrilobitesrepresentthemostdiversetrilobiteassociationintheregion,andarecomparabletotheCeratopygefauna.TheKuagachianfaunacontainsafewadditionalelements,increasingthedifferencebetweensouthandnorthbutwithreducedgenericdiversity.Theroutesoffaunalexchangearemodifiedtoo.ThusduringtheEarlyOrdovicianmigrationbetweentheUraliansideofBalticaandtheBaltoscandia,KazakhandAltai-SayanterranesbecomesmoreimportantthanthatbetweentheUraliansideofBalticaandtheSiberia,NorthandSouthChinaplates.TheDarriwilianKarakoľ-MikhailovskianfaunalassociationshowsaclearseparationbetweennorthandsouthUralswiththeformerregion,asinBaltoscandia,dominatedbyasaphids,whileinsouthareefalillaenid-cheiruridassociationofLaurentiangeneraoccurs.ThisisratherintriguinggiventhewidelyacceptedpalaeogeographicaldisparatepositionandlatitudeofLaurentiaatthetime.

【 授权许可】

Unknown