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Galeacysta etrusca Corradini & Biffi 1988, dinoflagellate cyst marker of Paratethyan influxes into the Mediterranean Sea before and after the peak of the Messinian Salinity Crisis

More than a thousand specimens of Galeacysta etrusca complex from eleven Upper Miocene and Lower Pliocene localities of the Paratethyan and Mediterranean realms have been studied using a biometric approach in part relating to the degree of separation between endocyst and ectocyst. Four stable biometric groups have been statistically distinguished, the occurrence or prevalence of which appears closely linked to environmental conditions irrespective of the realm. Group “ a” is related to brackish conditions, group “ b” to marine conditions, group “ c” to freshwater, and group “ d” to high nutrient levels. Based on an accurate chronology provided by calcareous nannoplankton bioevents and recognition of the Messinian Erosional Surface, this study reveals: - the high sensitivity of Galeacysta etrusca complex for reconstructing paleoenvironments and the connection– isolation phases of basins ; - the detailed history of this species which originated in the Pannonian Basin at ca. 8 Ma before invading the Dacic Basin at about 6 Ma, then migrating into the Mediterranean during high sea-level connections (the “ Lago Mare” events just before and after the peak of the Messinian Salinity Crisis, i.e. at 5.60 and during the interval 5.48– 5.33 Ma, respectively) and, finally, into the Black Sea at 5.13 Ma ; - an improved paleogeographic reconstruction for the Mediterranean and Paratethyan realms with focus on the location of corridors and the timing of when they were active. Field observations and dinoflagellate cyst data lead us to consider that the reflooding of the Mediterranean Basin by Atlantic waters occurred at 5.48 Ma, i.e. significantly before 5.33 Ma that is the age of the Zanclean GSSP.

Galeacysta etrusca complex; Paratethys– Mediterranean; Messinian; Zanclean; “ Lago Mare”

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