Improved modelling of the Messinian Salinity Crisis and conceptual implications

This paper presents the last developments of a simple oceanographic modelling of the water and salt budgets of the Mediterranean Sea during the late Miocene Salinity Crisis. The Messinian Mediterranean is treated as analogous to the present one, i.e. divided into two main basins separated by a sill at shallow or intermediate depth. When the supply of marine water from the Atlantic is progressively reduced, both basins undergo a rise in salinity, until saturation is reached: this is when the true evaporitic sedimentation begins, before the level drawdown. The partition of the Mediterranean into two mains basins causes a shift in the evaporitic sedimentation from the distal (eastern) basin to the proximal (western) basin, so that the evaporitic deposits are not fully contemporaneous in the western and the eastern basin. The drawdown is limited by the equilibrium of the evaporation and chemical activity of the brines at the surface, against the surface area and evaporation. Attempts at adjusting the model both to an accurate stratigraphic frame and to a rough budget of the evaporites shows that the Upper Evaporites and brackish-water Lago-mare series must have been deposited as secondary deposits, after the closure of the Atlantic passages was completed. The present evaporitic potentialities of the Mediterranean Sea remains quite as strong as during the Miocene, so that climatic change cannot be inferred from the MSC itself.