Mediterranean-Paratethys connectivity during the Messinian salinity crisis: The Pontian of Azerbaijan

• We create a cyclostratigraphic age model for Late Miocene sediments deposited in the Caspian Sea.
• Micropaleontology indicates brackish-marine conditions throughout the Messinian salinity crisis.
• Signs of a desiccation of the Caspian Sea related to the MSC are not observed in our record.
• During the Messinian salinity crisis the Paratethys formed a sea of similar surface area as the Mediterranean.
• Continental Eurasia up to the Himalaya contributed to the hydrological budget of the Mediterranean Sea.

Prior to the onset of the Messinian Salinity Crisis, a connection was established between the Mediterranean Sea and the Paratethys region to the north. Rivers currently draining into the Caspian Sea thereby became important for the Mediterranean hydrological budget. The role of this connection and the influence of the Paratethys on the hydrological budget of the Mediterranean Sea during the Messinian Salinity Crisis is however poorly understood because of a lack of records in the Paratethys with a high-resolution (cyclostratigraphic) age model. Here, we present a high-resolution integrated stratigraphic study of a key section in the Caspian Sea region (Azerbaijan), to assess the connectivity of the Caspian Sea during the salinity crisis. The studied section spans the time interval between ~ 6.16 Ma and < 5.38 Ma, and records continuous deposition under brackish-marine conditions. We show the connection between the Mediterranean Sea and the Caspian Sea formed at 6.12 ± 0.02 Ma. Across the onset of the Messinian Salinity Crisis, the studied section changes from anoxic to oxic conditions and an abundant ostracod fauna develops. A sea-level drop in the order of 100–200 m is evident from changes in the ostracod faunal assemblage and is dated at 5.6 Ma. The top of the section marks a second sea-level drop and the complete freshening of the record. The Pontian phase of Mediterranean-Paratethys connectivity represents a maximum size of Paratethys at a time of minimum Atlantic-Mediterranean connectivity. Enhanced Paratethys outflow water at this time likely led to increased stratification and affected the Mediterranean throughout the Messinian Salinity Crisis.