The GSSP of the Messinian Stage, which per definition

marks the base of the Messinian and, hence, the bound-ary between the Tortonian and Messinian Stages of the Upper Miocene Subseries, has recently been defined and ratified by the IUGS. The boundary stratotype sec-tion is Oued Akrech (Morocco) where the Messinian GSSP is now formally designated at the base of the red-dish layer of sedimentary cycle no.15. This point coin-cides closely with the first regular occurrence (FRO) of the planktonic foraminiferal Globorotalia miotumida group and the first occurrence (FO) of the calcareous nannofossil Amaurolithus delicatus, and falls within the interval of reversed polarity that corresponds to C3Br.1r. The base of the reddish layer and, thus, the Messinian GSSP has been assigned an astronomical age of 7.251 Ma