Conference:
32nd International Geological Congress, Florence, Italy, 20-28 August, Sessions: T-34.02 Sea-Level change since the last glacial maximum and G-19.02 Climate and paleoenvironmental changes during the Quaternary: palynological evidence
Author:
Speranta-Maria Popescu.
Abstract:
During the Late Holocene, the Black Sea and the Marmara Sea were concerned by important environmental changes. Before the last invasion by Mediterranean waters (at 12 ka BP in the Marmara Sea and 7,150 ka BP in the Black Sea), the two seas evolved independently (perched basins), being characterised by fresh- to brackish waters. The invasion by Mediterranean waters modified paleogeography and environmental conditions. Was such an invasion a progressive or catastrophic event? High resolution palynology (pollen grains and dinocysts) was performed on five cores: two in the Black Sea, two in the Marmara Sea, and one within the Bosphorus Strait. Pollen data document the response of the vegetation to climatic changes: the Younger Dryas cold period is characterised by a strong increase in herbs and steppe elements; the following Holocene is marked by an increase in thermophilous trees. Two dinocyst assemblages have been recorded, which succeed one another near a sapropel: (1) stenohaline species, such as Pyxidinopsis psilata and Spiniferites cruciformis, endemic species of the Black Sea and Marmara Sea, almost exclusively constitute the dinocysts assemblages of samples underlying the sapropel; (2) they are suddenly replaced within the sapropel 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 high resolution dinocyst analysis results in the evidence of connections between the Black Sea – Marmara Sea – and Mediterranean Sea earlier than generally expected and in a new chronology for this event.