简介：TheGSSPoftheTortonianStage,whichperdefinitionmarksthebaseoftheTortonianand,hence,theboundarybetweentheSerravallianandTortonianStagesoftheMiddleandUpperMioceneSubseries,hasrecentlybeendefinedandratifiedbytheIUGS.Theboundarystratotype-sectionisMontedeiCorvi(Italy)wheretheTortonianGSSPisnowformallyatthemid-pointofthesapropelofsmall-scalesedimentarycycleno.76,closetothelastcommonoccurrences(LCOs)ofthecalcareousnannofossilDiscoasterkugleriandtheplanktonicforaminiferGlobigerinoidessubquadratusandassociatedwiththeshortnormalsubchronC5r.2n.TheGSSPlevelcoincidescloselywithoxygenisotopeeventMi-5andtheassociatedglacio-eustaticsea-levellow-standofsupercycleT3.1andconcurrentdeep-seahiatusNH4,andisdatedastronomicallyat11.608Ma.TheMonteGibliscemisectionisacceptedasanauxiliaryboundarystratotypebecausethebetterpreservationofthecalcareousmicrofossilsinthissectionenablesquantitativeanalysesandtheconstructionofastableisotoperecord.