Role of Marine Gateways in the Paleoceanography of the Miocene Mediterranean Sea; A Model Study

Abstract:

During the Miocene, due to the convergence of the African plate and the Eurasian plate, the Mediterranean region was subject to profound paleogeographic changes. The evolving coastline and bathymetry of the Mediterranean Sea and, in particular, the opening and closure of the marine connections between the Mediterranean and the outside oceans, triggered important changes in Mediterranean circulation and, indirectly, also affected the global-scale ocean circulation.

Until about the Middle Miocene the proto-Mediterranean Sea was open to the Indo-Pacific Ocean through the so-called Indian Gateway. Although the exact age of closure of this gateway is still debated, it is accepted that it substantially affected the paleoceanography of the Mediterranean Sea. Later in time, during the Late Miocene, the Mediterranean was only connected to the Atlantic Ocean but by two marine corridors: the Betic and Rifian corridors. Closure of these narrow passages resulted in the Messinian Salinity Crisis, during which a sequence of evaporites was deposited throughout the Mediterranean basin.

In this work we use a regional-scale ocean general circulation model (the Princeton Ocean Model) to gain insight into the role of the evolving gateways. The analysis focuses on large-scale (overturning) circulation, patterns of exchange in the gateways and properties of the Mediterranean water. By comparing our model results to geological data we are able to propose new scenarios or rule out previously proposed ones, and determine the conditions evidenced by the geological observations. More specifically we investigate two different topics: (i) the effects of shoaling and closure of the Indian Gateway and (ii) the functioning of the Late Miocene double gateway to the Atlantic.