Neogene tectonics in the Western Mediterranean may have caused the Messinian salinity crisis and an associated glacial event
The Messinian Salinity Crisis (MSC) was a catastrophic event which led to the deposition of 10 6 km 3 of evaporite in the Mediterranean between 6.5 and 5 Ma B.P. Stratigraphic investigations have previously suggested that the progressive increase of salinity in the Mediterranean leading to the MSC may have been caused by tectonic narrowing and closure of seaways between the Mediterranean and the Atlantic. Detailed reconstruction of the tectonic history of the Arc of Gibraltar and adjacent Alboran Basin independently suggests: (1) that the early Miocene Guadalquivir and Alboran seaways closed and narrowed, respectively, near the end of the Tortonian, 7 Ma B.P., and (2) that the tectonic Arc of Gibraltar progressively emerged above the sea level during the Messinian (7-5 Ma B.P.) which caused, together with a eustatic glacial lowering of the sea level, the isolation and subsequent dessication of the Mediterranean. This is in agreement with a two-stage history of the MSC previously postulated on the basis of stratigraphical observations: (1) deep-basin/deep-water and (2) deep-basin/shallow-water salt deposition. The closure of the seaways between the Mediterranean and the Atlantic and the associated drop in world-wide oceanic surface salinity may even have caused the Kapitean-Optian glacial event about 5.5 Ma B.P.