摘要
Aglobal-scaleglaciationoccurredatabout600Maago.Asaresult,theEarthbecamethe'SnowballEarth'.Theglaciationcametotheendabruptlywhenatmosphericcarbondioxideincreasedtosuchanextentastobeabout350timesthemodernlevelbecauseofsubaerialvolcanicdegassing.TherapidterminationofglaciationwouldhaveledtowarmingoftheSnowballEarthandextremegreenhouseconditionswouldhavebeencreated.Thetransferofatmosphericcarbondioxidetooceanswouldgiverisetotherapidprecipitationofcalciumcarbonateinwarmsurfaceseawaters,thusformingthecapcarbonaterocksasobservedworldwidetoday.Regionallypersisting,thinlayersofcarbonaterocksdirectlyandubiquitouslyoverlieProterozoicglacialdepositsalmostoneverycontinent,andarecommonlyreferredtoascapcarbonates.Theirunusuallitho-fabrics,stratigraphicallyabruptbasalandupper-levelcontactsandstronglynegativecarbonateisotopicsignatures(δ13Ccarb.valuesrangefrom-7.0‰-0‰)suggestachemicaloceanographicorigin,thedetailsofwhichremainunknown.Itisproposedthattheseenigmaticdepositsarerelatedtothedestabilizationofgaseoushydrateinterrestrialpermafrostfollowingrapidpostglacialwarmingandfloodingofwidelyexposedcontinentalshelvesandinternalbasins.Theauthorscarriedoutstudiesonthegeochemistry,sedimentologyandpalaeontologyoftheSiniancapcarbonatesinGuizhouandHunanprovinces,includingtheoccurrenceofcapcarbonatesofunusualfabrics,stronglynegativecarbonisotopicsignatures,andalotofbitumennodules.Fromtheresultsitissuggestedthatthecapcarbonateswereformedfromsolidmethaneseepage,anditisinagreementwithKennedy'sviewpoint(2001)thatthecapcarbonatesresultedfromtherapidprecipitationofcalciumcarbonateinresponsetosolidmethaneseepage.
出版日期
2003年04月14日（中国Betway体育网页登陆平台首次上网日期，不代表论文的发表时间）
