Changing seas in the late Miocene Northern Aegean: A Paratethyan approach to Mediterranean basin evolution

The Northern Aegean region evolved during the Miocene as a restricted land-locked basin with small ephemeral connections to both the Eastern Paratethys (former Black Sea) and Mediterranean. Its biostratigraphic data show mixed Paratethys-Mediterranean components, but the Paratethys fauna has generally been neglected for chronologic reconstructions. Here, we review this biostratigraphic data from a Paratethyan perspective and present revised paleogeographic reconstructions of the Northern Aegean throughout the late Miocene. In the Tortonian, all sub-basins show mainly fluvio-deltaic terrestrial environments with a series of scattered lakes that are predominantly fed by local rivers and short-lived Paratethys connections. The first persisting marine conditions, still alternating with brackish Paratethyan environments, indicate a middle Messinian (late Maeotian) age (6.9-6.1 Ma), when the region formed a semi-isolated (Egemar) sea with multiple marine influxes. The termination of marine conditions is very well documented by a marked palaeoenvironmental change to the brackish water environments that correlate to the Maeotian/Pontian boundary (6.1 Ma) in Eastern Paratethys. During the Messinian Salinity crisis (5.97-5.33 Ma), the Northern Aegean was a brackish water system (Lake Egemar) that formed a passageway for Paratethyan overspill waters towards the Mediterranean. We conclude that the thick evaporites of the Northern Aegean domain do not reflect the classic Mediterranean MSC sequences, but are more likely related to older (Badenian or Maeotian) salinity incursions.