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The Vicchio outcrop in the Tuscan Apennines contains excellent exposures of a Miocene methane-derived carbonate system, made up of more than 80 carbonate bodies enclosed in marly sediments. Facies analysis, composition and a detailed biostratigraphic study of the carbonates and enclosing Vicchio Marls allowed us to document the role of climatic changes and eustasy on seepage in these ancient deposits. Results of our study indicate that the stratigraphic horizon bearing seep-carbonates is constrained by two planktonic foraminiferal events, the Acme End (AE) of Turborotalita cf. T. quinqueloba (13.75 Ma) and the Acme₁ Beginning (A₁B) of Paragloborotalia siakensis (13.32 Ma), encompassing about 400,000 years. The AE of T. cf. T. quinqueloba approximates the mid-Miocene global cooling event (Mi3b), as defined by the δ¹⁸O maxima (13.78 Ma). The glacio-eustatic sea level drop associated with this …