VEGETATION DYNAMICS, CLIMATE CHANGES, AND HUMAN ACTIVITY ALONG THE BULGARIAN BLACK SEA COAST DURING THE LATE PLEISTOCENE AND HOLOCENE

This report summarizes data obtained during the investigation of 17 cores from shelf and deep-water zone of the Black Sea, together with 8 cores from coastal lakes and river estuaries. Sediments have been investigated in terms of their pollen content, but dinoflagellate cysts were also counted. The earliest periods (Plenigalcial and Late Glacial) are represented only in marine sediments. For the Holocene progressively more information became available. The evidence indicates that cold and dry conditions prevailed during the Pleniglacial and cold phases of the Late Glacial. Artemisia, Chenopodiaceae, and Poaceae species were dominant and a small number of trees occur in restricted areas on edaphically favorable spots. The Bølling and Allerød warm phases are reflected by an increase of Pinus. Maximum presence of cysts of stenohaline dinoflagellate species Pyxidinopsis psilata and Spiniferites cruciformis, that inhabit brackish water confirmed the aridity of climate, and low sea-level. The vegetation dynamics during the Holocene are consistent with the general climatic improvement. The persistence of the steppe vegetation along the northern Bulgarian Black Sea coast indicates warm summer temperatures during the time of the increased summer insolation and low levels of precipitation. Only during the climatic optimum e.g. Atlantic after 6800±100 BP there was a change from xerothermic steppe with stands of trees to forest-steppe, suggesting increased humidity. Another line of vegetation development and an establishment of an open forest cover is observed on the southern Bulgarian Black Sea coast during the Early Holocene (9945±160 to 8355±75 BP). A long period of existence of balanced mesoxerophyllous oak and hornbeam forests during the climatic optimum (Atlantic) is marked. The human influence is established in pollen diagrams from the submerged Late Eneolithic and Early Bronze Age settlements by the increase of cultivated and anthropophytic taxa. The increase of euryhaline dinoflagellate cysts of Lingulodinium machaerophorum and Spiniferites ramosus, and acritarchs Cymatiosphaera globulosa started at 8355 yrs BP.