Conference:
EEDEN, Environments and Ecosystems Dynamics of the Eurasian Neogene, Birth of the New World., 12-16 November 2003, Stara Lesna, Slovakia.
Author:
Speranta-Maria Popescu, Maria Süto-Szentai
Abstract:
Dinoflagellates are famous by respect both to their motile and encysted forms. The latter (i.e. the dinocysts) only interest geologists because of their preservation in old to recent marine sediments. The conditions of passage from the motile to the encysted forms and vice versa are not well known, but it is generally assumed that, apart from the annual cycle of life, some influence may be due to environmental stresses. The morphological response of dinocysts to stress in salinity has been evidenced in the Holocene deposits of the Black Sea (BLKS 9810 core) when it was invaded by the Mediterranean salted waters. These morphological changes concerned the endemic species as well as the immigrants. Quite similar morphotypes have been observed in the DSDP Site 380A when the Mediterranean waters entered the Black Sea just after the Messinian salinity crisis. Comparable causes producing similar effects, it has been decided to revisit the Miocene of the Paratethys. The approach is based on (1) pollen record in order to identify climatic changes, (2) dinocyst record which informs on sea-surface paleotemperature and paleosalinity i.e. on the occurrence of Mediterranean water influxes into the Paratethys realm. A special effort has been done on the time span going from Sarmatian to Dacian. It is first concluded that taxonomy needs to be seriously revised (more than 50% of the species being invalid with respect to the international nomenclature) in the light of the successive changes noted in dinocyst morphology forced by changes in salinity. The method uses cultures of living dinoflagellates submitted to various stresses in salinity and observations on Scanning Electronic Microscope of the resulting dinocysts to be compared to the fossil ones from the Paratethyan Late Neogene. A new understanding of the Mediterranean-Paratethys relationships and exchanges is expected from this investigation.