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1、EarthandPlanetaryScienceLetters190(2001)181^196www.elsevier.com/locate/epslTheearlyPaleozoiccarboncycleYvesGodde¨risa;*,LouisM.Franc°oisa,Ja¨nVeizerb;caLaboratoiredePhysiqueAtmosphe¨riqueetPlane¨taire,UniversityofLie©ge,4000Lie©ge,BelgiumbOttawa-CarletonGeoscien
2、ceCenter,UniversityofOttawa,Ottawa,ON,CanadaK1N6N5cInstitutfu«rGeologie,MineralogieundGeophysik,RuhrUniversita«t,44780Bochum,GermanyReceived26April2000;accepted10May2001AbstractAreviewofO,C,SrandSisotopetrendsfortheentirePhanerozoicshowsthatthepresent-dayvalueso
3、fisotopesignalsaresimilartothoseattheProterozoictermination.Thesharprisein87Sr/86SrsinceV65MahasbeenattributedtoanupliftandsubsequentmetamorphismanderosionassociatedwiththeHimalayasandTibet.Thisorogenicevolutionhasbeenpostulatedtohaveinfluencedtheglobalorganican
4、dinorganiccarboncyclesandclimateaswell.Asimilarlarge-scaleorogeny,thePan-Africanevent,alsodominatedtheNeoproterozoic(Vendian)times,andthesimilarityofmodernandNeoproterozoicisotopevaluesforseawatermaythereforehavehadacomparabletectoniccause.Inthiscontribution,wep
5、resenttheresultsofanumericalmodelofthecoupledC^alkalinity^S^SrcyclessuggestingthattheearlyPaleozoic(fromearlyCambriantolateDevonian)evolutionofSr,O,CandSseawaterisotopesignalscouldhavebeentheconsequenceofprogressiveoxidationofalargereducedcarbonreservoirexhumedd
6、uringthePan-Africanorogeny.TheN18Omeasuredinbrachiopodshellsisusedasaforcingofthemodel,postulatingthatanychangeintheoxygenisotopiccompositionofseawateristheresultofadisequilibriumintheorganiccarbonsubcyclethroughthecouplingoftheoxygenisotopicandcarboncycles.Thec
7、alculatedN13C,87Sr/86SrandN34Sareingoodagreementwiththedata,asisthereasonablecalculatedhistoryforatmosphericpCO2anditsrelationtoglobalclimate.ß2001ElsevierScienceB.V.Allrightsreserved.Keywords:carboncycle;models;lowerPaleozoic;seawater;isotoperatios1.Introductio
8、noftracersre£ectingtectonics(87Sr/86Sr,187Os/186Os,44Ca/40Ca),lifeand/orredoxstate(N34S,Seawateranditsisotopiccompositionisargu-N13C)andthephysicalpropertiesoftheocea
