An international research team led by a scientist at New Zealand's University of Otago has resolved the mystery of the processes involved in the Mediterranean Sea drying up around 5.6 million years ago.
The event, known as the Messinian Salinity Crisis (MSC), saw the Mediterranean become a 1.5km deep basin for around 270,000 years. It also left a kilometers-deep layer of salt due to seawater evaporation.
The cause of the MSC has been the subject of vigorous scientific debate, but now an international team of researchers led by Otago geologist Dr Christian Ohneiser have used a multidisciplinary approach to solve the puzzle.
The deep record of the Messinian salinity crisis: Evidence of a non-desiccated Mediterranean Sea
Authors:
Lugli et al
Abstract:
This research is focused on a complete reexamination of the evaporite facies present in all the cores that cut through the topmost deposits of the Messinian salinity crisis lying below the floor of the Mediterranean Sea (DSDP Legs 13 and 42A, ODP Legs 107 and 161). This review suggests that the uppermost evaporite units in both western and eastern deep Mediterranean basins consist mainly of clastic (gypsrudite, gypsarenite and gypsiltite) and fully subaqueous deposits (laminar gypsum, selenite and cumulate halite) that are partially affected by burial anhydritization and tectonic-induced recrystallization. No unequivocal evidence of shallow water or even supratidal (sabkha) deposition is in evidence, suggesting that at the very last phase of the salinity crisis the Mediterranean Sea did not experience desiccation, but that deposition took place under permanent subaqueous conditions.
Computational fluid dynamics simulations of the Zanclean catastrophic flood of the Mediterranean (5.33 Ma)
Authors:
Periáñez et al
Abstract:
Numerical simulations of the Mediterranean Sea filling after the Messinian salinity crisis have been carried out with a two-dimensional non-linear depth-averaged hydrodynamic model. It overcomes simplifications and gross estimates of previous 0-D models. Erosion of the seabed has been implemented in the model domain. The highest erosion rates were found in the Alboran Island passage and in the eastern side of the Strait of Gibraltar. Regressive erosion, at a final stage, can account for the incision channel found in Camarinal Sill. This last limits the inflow to some 90 Sv when the cross-section in the eastern side becomes higher. Water level in the Mediterranean increases at a rate of a few meters per day. Detailed views of the induced circulation in the Mediterranean Sea have also been obtained.
Black Sea desiccation during the Messinian Salinity Crisis: Fact or fiction?
Authors:
Arjen et al
Abstract:
The late Miocene Messinian Salinity Crisis (MSC) was an extraordinary geologic event in the Mediterranean Basin marked by massive salt accumulation and presumably basin desiccation as a consequence of the reduced water exchange with the Atlantic Ocean. The discovery of a desiccation deposit in the Black Sea, the so-called Pebbly Breccia unit, was used to claim that the Black Sea also became desiccated during the MSC. Erosional features interpreted from seismic profiles of the Black Sea margin, correlated by some to the Pebbly Breccia unit, were used to support this hypothesis. However, the age of the Pebbly Breccia is poorly constrained, and its origin and relevance to the MSC subject to controversy. Here we present new biostratigraphic (dinoflagellate cyst) data from two key sedimentary successions located in a deep and a marginal setting of the Black Sea Basin. These records demonstrate that the Pebbly Breccia predates the Mediterranean water-level drop during the MSC. We argue that the presumed erosional features in the Black Sea Basin are not related to the MSC and likely represent an older Miocene event.
