HOLOCENE BLACK SEA ENVIRONMENTS ACCORDING TO PALYNOLOGY

The Mediterranean marine waters enterred the Black Sea during the Holocene, resulting in a sapropele deposition at 7,150 ± 100 yrs BP. Palynology has been performed on the off-shore BLKS98-10 core.

The lower part of the pollen diagram, dominated by herbs, corresponds to the Younger Dryas cooling. The upper part of the core is characterised by increasing percentages of thermophilous trees, that documents the Holocene warming phase.

Two successive dinocyst assemblages have been recorded near the sapropele: - stenohaline species, such as Pyxidinopsis psilata and Spiniferites cruciformis, endemic in the Black Sea, almost exclusively constitute the dinocyst assemblage of samples underlying the sapropele; - suddenly, they are replaced at the sapropele level by euryhaline species, such as Lingulodinium machaerophorum, Spiniferites membranaceus, S. mirabilis, Pentapharsodinium dalei, Operculodinium centrocarpum, etc., i.e. the species transported by the invasive Mediterranean waters.

The climatic warming recorded in the upper part of the core is both documented by pollen data and those of the dinocysts which were able to withstand the new conditions. Species generally living in warm-temperate surface marine waters have been recorded but suffer some transformations in morphology probably caused by change in salinity. The climatic cooling recorded below is emphasized by dinocysts preferring low temperature and little salted waters. Among them, S. cruciformis and P. psilata are still alternating along the core and show relevant changes in morphology (in shape, size and sculpture of the cysts). Such an event (i.e. the flooding of the Mediterranean waters into the Black Sea) was very sudden (recorded on 7 cm only of the core). Among other consequences, it caused relevant changes in dinoflagellate morphology whatever their origin (Mediterranean or Black Sea).