Environmental Changes in the pre-Messinian Mediterranean Region

Abstract:

The Messinian Salinity Crisis (MSC) is an extreme event which occurred in the Mediterranean Basin at the end of the Miocene (5.97 to 5.33 Ma) resulting in thick evaporite deposits. There is evidence of restriction of the Atlantic-Mediterranean corridor several million years before the first evaporites. These pre-MSC successions are dominated by precession-controlled lithological variations which are putative responses to changing fluvial runoff. Recent climate simulations indicate that runoff into the Eastern Mediterranean is influenced by monsoonal precipitation from the North African continent. The Sorbas Basin in Spain and the Pissouri Section on Cyprus both contain pre-MSC successions from the margins of the Mediterranean Basin. We analysed biomarkers in conjunction with existing faunal records to understand whether simulated runoff changes were manifested in the sedimentological record and organic matter assemblages. This multi-proxy dataset allows us to compare the environmental evolution of the western vs. eastern basins prior to the MSC and allows us to test both climate models for Messinian climate variabitly and conceptual models for sedimentation. In the Sorbas Basin, pronounced orbital changes in faunal assemblages reflect Mediterrannean influences into the local Sorbas system; however, these are not manifested in biomarker assemblages, which are likely governed by more local hydrological processes, which in the Western Mediterranean lacked a strong precessional control. In the Pissouri Basin, however, terrigeous OM inputs sources exhibit strong orbital variations, suggesting a close link to precessionally driven changes in rainfall. Together, these results validate the sapropel formation hypothesis in the Mediterranean and confirm a strong precessional control on the African monsoon during the late Miocene; however, they also reveal the complex controls on the hydrology and sedimentology of marginal Mediterranean basins, such as the Sorbas Basin.