Conference:
4th Congress “Environment and Identity in the Mediterranean – the Messinian Salinity Crisis”, Corte, France, 19-25 July, 2004.
Author:
Speranta-Maria Popescu.
Abstract:
Relationships between the Mediterranean Sea and the Paratethys realm are debated from a long time. Normal connections between these seas are generally considered to have ended in the late Miocene. Two successive Mediterranean nannoplankton influxes belonging to NN11 and NN12 zones have been evidenced in the Dacic and Euxinian basins. Nannoplankton is accompanied by typical marine dinocysts: Spiniferites mirabilis, Spiniferites bentorii, Tectatodinium pellitum, Spiniferites hyperacanthus, identified within the Dacic Basin. More recently, dinocysts such as Galeacysta etrusca, and morphotypes of Spiniferites cruciformis and Pyxidiniopsis psilata (= Impagidinium sp.; Corradini & Biffi, 1988) the usual endemic Paratethyan species have been regularly found in the Mediterranean area (Corradini & Biffi, 1988) and added to the “Lago Mare” biofacies (Bertini et al., 1994, 1995). These data indicate the existence of high sea level cross exchanges between the Mediterranean Sea and the Eastern Paratethys just before and after the Messinian salinity crisis. Moreover, dinocyst assemblages show a large number of marine species morphotypes in the western part of the Dacic Basin, which probably originate from adaptation to low salinity. Palynological analysis from Site 380 (Black Sea) shows a very poor assemblage of Paratethyan dinocysts in the late Miocene, a bloom of freshwaters acritarchs (between 5.33 Ma and 5.11 Ma) being followed by an assemblage grouping brackish and marine dinocysts. The presence of typical marine taxa in the western part of the Dacic Basin, the development of marine taxa morphotypes in the eastern part of the basin and the presence of freshwaters acritarchs just after Messinian salinity crisis in the Euxinian Basin suggest that: (1) the “proto-Bosphore” was closed at this time, and (2) the Dacic Basin should have been directly connected to the Mediterranean Sea, being itself episodically connected to the Black Sea. Dinocysts are highly sensitive to environmental changes, especially to salinity changes. As a consequence, they can adapt to new conditions with some important morphological changes. The Paratethyan endemic species Galeacysta etrusca is a demonstrative example.