LATEGLACIAL OF LAKE ONEGA - CONTRIBUTION TO THE HISTORY OF THE EASTERN BALTIC BASIN

New stratigraphy data especially diatom analyses are presented from the area north of Lake Onega relevant to the discussion on possible Lateglacial connection between the Baltic Sea and White Sea. Following the deglaciation 12,000-11,000 years ago Lake Onega basin was occupied by a system of ice dammed lakes which drained to the Lake Ladoga basin. When the ice retreated from the threshold leading to the White Sea 11,000 years ago the water level dropped and since that the lake was controlled by its thresholds to the White Sea and the Baltic basin. Lake Onega has remained distinctly above the spa level and no Late Weichselian sea connection existed between the White Sea and Baltic basins. The marine diatoms frequently found in sediments are reworked older fossils as also suggested by some earlier workers. Lake Onega drained to the White Sea basin over the Maselga threshold and also to Lake Ladoga between 11,000 and 10,000 radiocarbon years ago, and to the White Sea alone between 10,000 and 9500 years ago, and the present outlet of Lake Onega, River Svir, originated 9500 years ago.