Article:
Abstracts book of 13th Congress RCMNS, 2-6 September 2009, Naples, Italy “Earth System Evolution and the Mediterranean Area”, 2-6 September 2009, Naples, Italy, Acta Naturalia de “L’Ateneo Parmense”, Parma: 45 (1), p.107.
Authors:
Speranta-Maria Popescu, Jean-Pierre Suc, Georges Clauzon, Mihaela Carmen Melinte-Dobrinescu, Gilles Escarguel, Florent Dalesme, Gwénaël Jouannic, Martin J. Head, Maria Sütö-Szentai, Koralka Bakrak, Kenneth Mertens, Dries Vercaurten, Bertrand Meyer.
Abstract:
Relationships between the Mediterranean and Paratethys have been debated for a long time. High sea-level exchanges between these two seas are documented by the presence of: (1) marine organisms, especially calcareous nannoplankton and marine dinoflagellate cysts in the Paratethys basins; (2) brackish endemic dinoflagellate cysts, molluscs (dreissenids, lymnocardiids) and ostracods (Cyprideis pannonicagroup) in the Mediterranean area, as constituents of “Lago Mare” biofacies. Such connections are generally considered to have been reduced even interrupted in the Late Miocene, when the Mediterranean became temporarily isolated from the Atlantic Ocean. Isolation led to the Messinian Salinity Crisis, peaking with a severe drop in Mediterranean sea-level which resulted in the deposition of thick evaporites in central basins and intense subaerial erosion of the margins. Two successive falls in sea-level have been evidenced: (1) the first one, between 5.96-5.60 Ma, characterized by low amplitude, that caused the deposition of evaporites in the more-or-less isolated marginal basins and some erosion in the most proximal parts of river valleys; (2) the second one, between 5.60 to 5.46 Ma characterized by high amplitude, that caused the almost complete desiccation of the Mediterranean Sea and consequently evaporite deposition within central basins; on the land a huge subaerial erosion is widely recorded as a consequence of river activity. A huge erosion also impacted the Eastern Paratethys. Different hypothesis concerning the gateway between Mediterranean and Paratethys were proposed, the most known concerns the “proto-Bosporus” gateway. The second possibility is trough the Balkans. The supposed “proto Bosporus” gateway was tested, using the late arrival of marine dinoflagellate cysts at DSDP Site 380 in the Black Sea, that supposes that this gateway was still closed in the earliest Zanclean. This assumption is also supported by (1) the huge erosional surface passing at the base of the Zanclean deposits in the same locality, (2) the reconstruction of a complex fluvial erosional network in the Dardanelles Strait and Marmara Sea area at the time of the desiccation of the Mediterranean. Using the morphological changes of the Paratethyan dinoflagellate cyst Galeacysta etrusca, the presence of marine organisms and the evidence of Gilbert-type delta fans, we demonstrate that a probable gateway between the Mediterranean and Paratethys was trough the Balkans region. More difficult to explain are the connections between the Paratethyan (Pannonian and Dacic) basins themselves because these two basins were already evolving towards brackish conditions before the Messinian Salinity Crisis. Previous hypotheses suggested that the corridor between the Pannonian and Dacic basins before the Messinian Salinity Crisis (i.e. at the Portaferrian) was located at the present-day Iron Gates. The discovery of the Messinian Erosional Surface below the Iron Gates shows that this passage was cut by the proto-Danube River during the desiccation of the Mediterranean. As supported by dinoflagellate cyst records both in the Pannonian and Dacic basins, we propose a more reliable gateway in the area of the Timok Valley and Niš-Belgrade area at the Portaferrian.