Of sills and straits: a quantitative assessment of the Messinian Salinity Crisis

Improved chronology of the Messinian stage and available quantitative estimates of the evaporites allow the development of a simple modelling of the water and salt budgets of the two main Mediterranean Sea Basins during the late Miocene Salinity Crisis. Most of the geographic features of the Mediterranean are still analogous to what they were in Messinian times. Though still submerged in part, a continuous tectonic chain, extending from the Betic cordilleras to the Alps along the Maghreb and Italy, explains a delayed shift, from one basin to the other, in the sedimentation. The succession of sedimentary phases results from a simple, enduring tendency to the closure of the Western Strait, and does not indicate any break in the tectonic evolution. The model accounts for the Messinian evaporites without major changes in the climatic-hydrological parameters by comparison to the present: the conditions of this uncommon geological event are not extraordinary. For the first time, a geological and palaeoceanographic event is assessed in terms of flow-rate and amount of water consumed.