ENVIRONMENTAL CHANGES IN THE SE AND NE BLACK SEA DURING THE LATE QUATERNARY: PALYNOLOGICAL EVIDENCE

Late Quaternary sediments of the Black Sea have gained great interest since the late 1990s with the controversy of the timing and amplitude of the reconnection of the Black Sea with the Mediterranean at the beginning of the Holocene. The opposing hypotheses, “catastrophic flooding” versus “gradual inflow”, have generated numerous studies in the SW and NW, but only a handful in the SE and NE. In addition, the Black Sea has unique physical and chemical properties which makes it difficult to use conventional geochemical and palaeoceanographical proxies to reconstruct respectively chemical and physical conditions of water masses. Therefore estimations of surface water conditions have been based on assemblages of organic-walled dinoflagellate cysts that are well preserved in these anoxic environments. Vegetation of the adjacent lands is also well reflected from the pollen records.

To assess the synchronicity of changes at the scale of the basin during the Holocene, a marine sequence (AK2575) collected off Arkhipo Osipovka, on the NE shelf, has been studied using a multi-proxy approach (pollen, dinocysts, ostracods, mollusks). Comparison with dinocyst records from the SW and the SE shows strong similarities but also highlights some discrepancies that may be explained by local influence.

Records older than the Holocene are rare and challenging to date due to a lack of stratigraphical markers. One sequence, 22-CG3, from the southern region of the Black Sea, contains the Last Interglacial (LIG) interval as well as the Holocene. Dinocyst assemblages for both interglacials are dominated by Lingulodinium machaerophorum and Spiniferites ramosus, but the occurrence of Tuberculodinium vancampoae, Spiniferites pachydermus and Bitectatodinium tepikiense during the LIG suggests a warmer and more saline environment compared to the present interglacial.

Pollen records also allowed to understand how climatic conditions are linked to regional and/or northern hemisphere forcing.