The history of the Yoldia Sea in Northern Estonia: palaeoenvironmental conditions and climatic oscillations

Late glacial and Early Holocene sediment sequences from North ern Estonia were investigated using diatom and pollen analysis and the accelerator mass spectrometry (AMS) 14C dating. The results of diatom analysis indicate that fresh water conditions prevailed during the initial and final phases of the Yoldia Sea in the investigated area. A near-bottom saline water current that penetrated into the Baltic Sea Basin during the brackish phase of the Yoldia Sea spread into the Gulf of Finland at ca. 11 300-11 200 calendar years BP. Coastal upwelling probably caused mixing of the water column and the circulation of brackish water up to the surface incertain near-shore areas in the Gulf of Finland. A slight change in the pollen composition may suggest deterioration in the climate and can be correlated to the Preboreal Oscillation. AMS 14C dates on aquatic plant macrofossils suggest a reservoir ef fect more than 1000 year for the brackish phase of the Yoldia Sea.