A Quantitative Assessment of the Sea Level Drop in the Messinian Mediterranean

Abstract:

In the Late Miocene progressive restriction of the gateway(s) between the Mediterranean Sea and the Atlantic Ocean initiated the Messinian Salinity Crisis (MSC). The restriction caused a salinity rise and the formation of extremely thick evaporite deposits within the Mediterranean basin. Subsequently, the closure of the connection between the Mediterranean Sea and Atlantic Ocean resulted in a dramatic sea level drop.

The lithosphere adepts to changes in loads (sediments and water) on the surface by flexural adjustment of the Earth's surface. This can have a significant impact on the connectivity of basins and the temporal evolution of the sea level drop in each basin. The Mediterranean Sea is characterized by two deep basins with different amounts of river input (western/eastern Mediterranean basin) separated by the relatively shallow Sicily sill. The temporal evolution of the sea level drop in the western/eastern Mediterranean basin is therefore very sensitive to the temporal and spatial evolution of the Sicily gateway and hence flexure response of the earth surface due to the changes in waterload. However, studies of the MSC sea level drop haven't taken this flexural response into consideration (e.g. Meijer and Krijgsman, 2005).

Here we use an elastic model (TISC) coupled with a simple hydrology model to calculate the temporal evolution of the sea level drop in and the flexural response of the western and eastern Mediterranean basins. Preliminary results show that when sea level drops below the Sicily sill, the rate of sea level increases in the western but decreases in the eastern Mediterranean. Following a relative sea level drop of ~1300 m, resulting in a flexural uplift of ~700m, the eastern Mediterranean reaches equilibrium. At the time the western Mediterranean (flexural uplift of ~900m) reaches an equilibrium it is almost completely desiccated. The magnitudes of the sea level drops and flexural response are, however, highly dependent on the hypsometry, fresh water budgets, and strength of the lithosphere.