Deep Mediterranean's Messinian evaporite giant: How much salt?

Abstract

Abstract Evaporite giants can precipitate out of high salinity waters in semi-enclosed ocean basins when the rate of evaporation outstrips the inflow of new saline and fresh waters. The thick saline series deposited in the deep Mediterranean during the Miocene Epoch's late Messinian age (between 5.97 and 5.3 Ma) is among the youngest of such salt giants in Earth history. During this event, also known as the Messinian Salinity Crisis, voluminous evaporites accumulated in the deep basins when the main inflow of saline water to the Mediterranean through the Gibraltar Straits was severely diminished. The evaporites are interbedded with sediments eroded from the shelves and slopes or mass-transported downslope. Recent advances in geochronology and better understanding of the geodynamic history of various basins have led to insights about the timing of the salinity crisis and the tectonics and role of Gibraltar passage and other western narrows from the Atlantic to the Mediterranean. New estimates based on ocean-wide seismic facies analysis presented here reveal that there is between 821 ± 50 and 927 ± 50 thousand cubic km of late Messinian salt, and a total of up to 1.2 ± 0.1 million cubic km of salt plus associated sediment tied up in the deep Mediterranean basins. This suggests that after the initial restriction the Mediterranean had to be either continuously supplied with brine, or partially to completely refilled several times to produce the total salt edifice. The amount of Atlantic saline water needed to amass this evaporite giant is between 7 and 8 times the modern-day Mediterranean's equivalent of saline water. Our new volumetric estimates have implications for the Mediterranean's Messinian sequestration and desiccation scenarios and should lead to more meaningful geodynamic models and provide constraints for many of the controversies that still surround this major event in geological history. Maps of salt distribution in various basins also have important implications for sub-salt exploration geoscience.