A modeling perspective on spatial and temporal variations in Messinian evaporite deposits

During the Messinian Salinity Crisis (MSC), evaporite-dominated sequences formed in marginal and deep basins of the Mediterranean Sea. In the marginal basins, the onset of the MSC is synchronous and a single depositional framework fits all sequences. In contrast, MSC sequences of the western and eastern deep basins appear to comprise a different number of units and differ greatly in thickness. Even though there exist numerous scenarios for deposition in the marginal and deep basins, the link between the two settings is difficult and scenarios are rarely quantitatively supported. We employ a simple box model for the Messinian Mediterranean to examine the causes of (1) spatial variation in thickness and (2) differences in the time of onset of deposition. Model results are compared with actual observations on the MSC sequences. The results show that a large connection between the western and eastern basin is necessary for, and some degree of water column stratification is conducive to, synchronous onset of the MSC in the marginal basins. Moreover, halite deposits in the deep basins are likely to be coeval and have formed in ≈ 60 ka after a (further) restriction of the Atlantic–Mediterranean connection during the MSC, but without a significant sea level drop. A difference in the net salt gain per unit volume caused the different halite deposition rates in the two basins. A scenario with only a simple restriction of the Atlantic–Mediterranean connection during the Late Miocene – without significant changes in the Mediterranean sea level, the fresh water budget, or the size of the Strait of Sicily – is able to explain the synchronous onset of the MSC, the synchronous marginal evaporite formation and the differences in the deep basinal sequences.