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1、PALEOCEANOGRAPHY,VOL.25,PA3202,doi:10.1029/2009PA001851,2010ClickHereforFullArticleCarbonisotoperatioofCenozoicCO2:Acomparativeevaluationofavailablegeochemicalproxies1,231BrettJ.Tipple,StephenR.Meyers,andMarkPaganiReceived21August2009;revised16February2010;accepted1Mar
2、ch2010;published17July2010.13[1]Thecarbonisotoperatio(dC)ofplantmaterialiscommonlyusedtoreconstructtherelativedistributionof13C3andC4plantsinancientecosystems.However,suchestimatesdependonthedCofatmosphericCO213(dCCO2)atthetime,whichlikelyvariedthroughoutEarthhistory.F
3、orthisstudy,weusebenthicand131813planktonicdCanddOrecordstoreconstructalong‐termrecordofCenozoicdCCO2.Confidenceintervals13fordCCO2valuesareassignedaftercarefulconsiderationofequilibriumandnon‐equilibriumisotopeeffects13andprocesses,aswellasresolutionofthedata.Wefindth
4、atbenthicforaminiferabetterconstraindCCO2comparedtoplanktonicforaminiferalrecords,whichareinfluencedbyphotosymbiotes,depthofproduction,seasonalvariability,andpreservation.Furthermore,sensitivityanalysesdesignedtoquantifytheeffectsof1318temperatureuncertaintyanddiagenes
5、isonbenthicforaminiferadCanddOvaluesindicatethatthesefactors13acttooffsetoneanother.OurreconstructionsuggeststhatCenozoicdCCO2averaged−6.1±0.6‰(1s),whileonly11.2millionofthelast65.5millionyearscorrespondtothepre‐Industrialvalueof−6.5‰(with90%13confidence).HeredCCO2also
6、displayssignificantvariationsthroughouttherecord,attimesdepartingfrom13thepre‐Industrialvaluebymorethan2‰.Thus,theobservedvariabilityindCCO2shouldbeconsideredinisotopicreconstructionsofancientterrestrial‐plantecosystems,especiallyduringtheLateandMiddleMiocene,timesofpr
7、esumedC4grasslandexpansion.Citation:Tipple,B.J.,S.R.Meyers,andM.Pagani(2010),CarbonisotoperatioofCenozoicCO2:Acomparativeevaluationofavailablegeochemicalproxies,Paleoceanography,25,PA3202,doi:10.1029/2009PA001851.1.Introduction[3]Carbonfluxesintoandoutofocean‐atmospher
8、ere-1313servoirscanvaryovertime[Berner,1998,2006;Kumpand[2]ThedCvalueofatmosphericCO2(dCCO2),alongArthur,1999],andalt
