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1、spe424-0123pagesTheGeologicalSocietyofAmericaSpecialPaper4242007Cenozoicmassextinctionsinthedeepsea:WhatperturbsthelargesthabitatonEarth?EllenThomas*CenterfortheStudyofGlobalChange,DepartmentofGeologyandGeophysics,YaleUniversity,NewHaven,Connecticut06520-8109,USAABSTRACTDeep-seabenthi
2、cforaminiferaliveinthelargesthabitatonEarth,constituteanimportantpartofitsbenthicbiomass,andformdiverseassemblageswithcommoncos-mopolitanspecies.Moderndeep-seabenthicforaminiferalassemblagesarestronglyinfluencedbyeventsaffectingtheirmainfoodsource,phytoplankton(arelationshipknownasbent
3、ho-pelagiccoupling).Surprisingly,benthicforaminiferadidnotsuffersignificantextinctionattheendoftheCretaceous,whenphytoplanktoncommunitiesunderwentsevereextinction.Possibly,bentho-pelagiccouplingwaslessstrongthantodayinthewarmoceansoftheCretaceous–Paleogene,becauseofdifferencesintheproc
4、essoffoodtransferfromsurfacetobottom,orbecausemorefoodwasproducedchemosyntheticallyontheseafloor.Alternatively,aftertheend-Cretaceousextinctionthefoodsupplyfromthephoticzonerecoveredinlesstimethanpreviouslythought.Incontrast,deep-seabenthicforaminiferadidundergosevereextinction(30%–50%
5、ofspecies)attheendofthePaleocene,whenplankticorganismsshowrapidevolu-tionaryturnover,butnomajorextinction.Causesofthisbenthicextinctionarenotclear:netextinctionratesweresimilarglobally,butthereisnoindependentevidenceforglobalanoxiaordysoxia,norofgloballyconsistentincreaseordecreaseinp
6、ro-ductivityorcarbonatedissolution.Theextinctionmightbelinkedtoaglobalfeatureoftheend-Paleoceneenvironmentalchange,i.e.,rapidglobalwarming.Cenozoicdeep-seabenthicfaunasshowgradualfaunalturnoverduringperiodsofpronouncedcoolingandincreaseinpolaricevolume:thelateEocene–earlyOligocene,the
7、middleMiocene,andthemiddlePleistocene.Duringthelatterturnover,taxathatdecreasedinabundanceduringtheearliertwoturnoversbecameextinct,possiblybecauseofincreasedoxygenationoftheoceans,orbecauseofincreasedseasonalityinfooddeliv-ery.TheEocene-Oligocenewasthemostextensiveoftheseturnovers,an
8、dbent