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

Late glacial and Early Holocene sediment sequences from Northern Estonia were investigated using diatom and pollen analysis and the accelerator mass spectrometry (AMS) 14 C dating. The results of diatom analysis indicate that freshwater 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 in certain 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 14 C dates on aquatic plant macrofossils suggest a reservoir effect more than 1000 year for the brackish phase of the Yoldia Sea.