Dense shelf water cascading and Messinian Canyons: A new scenario for the Mediterranean salinity crisis

Abstract

The salt giant beneath the deep Mediterranean seafloor is the impressive record of the “Messinian salinity crisis,” a dramatic event that occurred about 6 Ma ago following the reduction of the connections with the Atlantic Ocean. According to the shallow-water deep-basin model, developed for these deposits ([Hsü and others, 1973a][1], [1973b][2], [1978a][3], [1978b][4]), the Messinian evaporites formed in a deep but desiccated Mediterranean, while shelves and slopes underwent subaerial erosion due to fluvial rejuvenation triggered by a 1500 m sea level drawdown. Deeply incised Messinian canyons in the continental slopes surrounding the Mediterranean are the main argument supporting this scenario. Using a state of the art model and idealized but realistic numerical simulations, here we demonstrate that the activation of downslope flows of hypersaline, dense waters, in a process similar to present-day “dense shelf water cascading,” but much more energetic, may account for both slope erosion and progressive salinity rise leading to the formation of deep-seated supersaturated brines. Our findings support a deep-water deep-basin model ([Schmalz, 1969][5], [1991][6]; [De Benedetti, 1976][7], [1982][8]; [Dietz and Woodhouse, 1988][9]), thus implying that evaporite deposition may have occurred in a non-desiccated basin with strongly reduced ocean connections. [1]: #ref-57 [2]: #ref-58 [3]: #ref-59 [4]: #ref-60 [5]: #ref-103 [6]: #ref-104 [7]: #ref-26 [8]: #ref-27 [9]: #ref-29