Proposed stratotype for the base of the Lawsonian Stage (Cambrian Stage 10) at the First Appearance Datum of Eoconodontus notchpeakensis (Miller) in the House Range, Utah, USA

Bulletin of geosciences

Miller JF¹  Evans KR¹  Freeman RL¹  Taylor JF¹  Ripperdan RL¹ 

关键词: Cambrian;    Furongian;    Lawsonian;    Stage 10;    chronostratigraphy;    conodonts;    trilobites;    brachiopods;    carbon isotopes;    HERB Event;   

DOI  :  

来源: Czech Geological Survey

【 摘 要 】

ThenameLawsonianStageisproposedasthehigheststageoftheCambrianSystem(Stage10).ThebaseoftheproposedLawsonianStageisattheFirstAppearanceDatum(FAD)oftheeuconodontEoconodontusnotchpeakensis(Miller,1969).Thathorizon,thebaseoftheE.notchpeakensisSubzoneoftheEoconodontusZone,is3mabovethebaseoftheRedTopsMemberoftheNotchPeakFormationattheSteamboatPasssectionintheHouseRange,westernUtah,USA.TheconodontfaunaoftheEoconodontusZoneiswidespreadinNorthAmericaandoccursinAsia,Australia,Europe,andSouthAmericainfaciesthatincludecratonicnearshoresandstones,shallowandintermediate-depthplatformcarbonates,deep-waterramp,continentalslopedeposits,anddeep-oceanradiolarianchert.ThishorizonliesatorslightlybelowthetopoftheIllaenurustrilobiteZoneofwesternNorthAmericaandwithinthelowerpartoftheSaukiellajuniaSubzoneoftheSaukiaZoneinareaseastoftheRockyMountains.Thesetrilobiteandconodontfaunascanbetracedintoslopedepositscontainingcosmopolitantrilobites.ThehorizonisnearlycoincidentwiththeboundarybetweentheBillingsellaandtheFinkelnburgiacalciticbrachiopodZones;rangesoforganophosphaticbrachiopodsalsocharacterizethehorizon.Ahigh-amplitude,negative,carbon-isotopeexcursion,theHERBEvent,occursintheEoconodontusnotchpeakensisSubzone.ThisdistinctivegeochemicalsignalisknowninwesternUtah,Australia,China,andinpoorlyfossiliferousslopedepositsinNewfoundland,Canada.Theproposedboundaryfitsbetweentwocloselyspacedsequence-stratigraphicboundariesdescribedfromUtahandTexas,USA.

【 授权许可】

Unknown