A new formally stratigraphic unit named Ses Olles Formation located at top of the upper Messinian and at base of the Pliocene marine succession in the island of Mallorca has been distinguished, defined and characterized. This unit is made up of lutites, marls and sandy marls containing charofites, rich mollusc faunas characterized by bivalves Lymnocardiinae and Dreissenidae of Paratethyan origin and non-marine gastropods, and low diversified ostracod faunas of Paratethyan affinity, typical of oligo-low mesohaline shallow waters. The stratigraphical position and the paleontological data restrict the age of the former to the late Messinian. The age and environmental conditions correlate these deposits with the Lago-Mare event occurring throughout the Mediterranean before the marine flooding at the beginning of the Pliocene.