Conference:
Scientific Workshop ” What happened in southern Romania and Black sea when the Mediterranean Sea desiccated 5.6 Ma ago”, Bucarest, Romania, 29 February – 1 March 2008, Abstract volume, Page 6.
Authors:
Speranta-Maria Popescu, Jean-Pierre Suc, Georges Clauzon, Mihaela Carmen Melinte- Dobrinescu, Gilles Escarguel, Frédéric Quillévéré, Mona-Lisa Cătălina Sîrbescu, Florent Dalesme, Gwénaël Jouannic, Martin Head, Maria Sütő-Szentai, Koraljka Bakrac, Kenneth Mertes, Dries Vercauteren.
Abstract:
Relationships between the Mediterranean and Paratethys have been debated for a long time (Senĕs, 1973; Rögl and Steiniger, 1983; Kojumdgieva, 1987; Marinescu, 1992). High sea-level exchanges between these two seas are documented by the presence of: (1) marine organisms, especially calcareous nannoplankton (Mărunţeanu, 1992; Semenenko and Olejnik, 1995; Mărunţeanu and Papaianopol, 1995, 1998; Drivaliari et al., 1999; Snel et al., 2006) and marine dinoflagellate cysts (Popescu, 2006; Popescu et al., accepted; Popescu and Süto-Szentai, unpublished data) in the Paratethys basins: (2) brackish endemic dinoflagellate cysts (Corradini and Biffi, 1988; Bertini, 1992, 2006; Popescu et al., 2007; Londeix et al., 2007), molluscs (dreissenids, lymnocardiids) and ostracods (Cyprideis pannonicagroup) (Cippolari et al., 1999; Gliozzi, 1999; Ghetti et al., 2002; Basseti et al., 2003, 2004; Esuet al., 2007) 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 (Hsü et al., 1973;Rouchy and Caruso, 2006) and intense subaerial erosion of the margins (Clauzon,1999). Two successive falls in sea-level (Clauzon et al., 1996) 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 5.48 Ma characterized by high amplitude, that provoked 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.
Similar events (huge erosion) also impacted the Eastern Paratethys (Gillet et al., 2003, 2007; Clauzon et al.,2005) where evaporites were recently discovered (Clauzon et al., submitted). Different hypothesis concerning the gateway between Mediterranean and Paratethys were proposed, the most known concerned the “proto-Bosporus” gateway (Hsü et al., 1973; Rögl and Steininger, 1983; Marinescu, 1992). The second possibility was trough the Balkans, an hypothesis proposed by Kojumdgieva (1987). The supposed “proto Bosporus” gateway was tested by Popescu (2006), using the late arrival of marine dinoflagellate cysts at DSDP Site 380 in the Black Sea, that demonstrates the closure of this gateway in the earliest Zanclean. This evidence is also supported by (1) the huge erosional surface passing at the base of the Zanclean deposits in the same locality Gillet et al. (2007), (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 (Clauzon et al., 2008). Using the presence of marine organisms and evidence of Gilbert-type delta fans, we demonstrate that the most probable gateway between the Mediterranean and Paratethys was trough the Balkans region (Clauzon et al., 2005, submitted; Popescu et al., accepted). Most 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 (Archambault-Guézou, 1976; Marinescu, 1992). The discovery of the Messinian Erosional Surface below the Iron Gates (Clauzon et al., 2005; Leever, 2007) 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 (Popescu et al., accepted).