117 BALTICA Volume 23 Number 2 December 2010 : 117-126 Reconstruction of the land–sea changes on the Juminda Peninsula, North Estonia, during the last 10 300 years Leili Saarse, Jüri Vassiljev, Atko Heinsalu Saarse, L., Vassiljev, J., Heinsalu, A., 2010. Reconstruction of the land–sea changes on the Juminda Peninsula, North Estonia, during the last 10 300 years. Baltica, 23 (2), 117-126. Vilnius. ISSN 0067–3064. Abstract New results of litho–, bio– and chronostratigraphic data from the Aabla Bog were used for creation of the GIS–based shore displacement model with a grid size of 50 x 50 m. Palaeogeographical maps for the Juminda Peninsula in northern Estonia were constructed for the last 10 300 years. The southern part of the peninsula had emerged from the waters of the Gulf of Finland before the Ancylus Lake transgression. The highest shorelines between 18.5 and 20.5 m above sea level (a.s.l.) formed during the Litorina Sea transgression at about 7800 calibrated years BP (cal. yr BP). After the Litorina Sea transgression the area of the peninsula enlarged mostly northwards and westwards due to land uplift. Diatom stratigraphic analysis indicates deposition of sand in an isolated shallow freshwater lake, not in a lagoon of the Litorina Sea, as was concluded earlier, and suggests that the Litorina Sea maximum water level was below the Aabla basin threshold elevation at 21–21.5 m a.s.l. Keywords Litorina Sea, palaeogeography, diatoms, radiocarbon dates, shoreline displacement, North Estonia. Leili Saarse[saarse@gi.ee], Jüri Vassiljev [vassilje@gi.ee], Atko Heinsalu [heinsalu@gi.ee], Institute of Geology at Tallinn University of Technology, Ehitajate tee 5, 19086 Tallinn, Estonia. Manuscript submitted 26 June 2010; accepted 8 Novemebr 2010. INTRODUCTION The problems concerning the Baltic Sea shoreline and sea level as well as palaeoenvironmental changes have been in the focus of research for a long time (e.g. Munthe 1910; Berglund 1964, 1971; Kessel, Raukas 1979; Björck 1995; Eronen et al. 2001). In the circum– Baltic Sea areas relative sea level rise was primarily governed by global sea–level rise and isostatic uplift (e.g. Fairbridge 1960; Ekman 1996; Uścinowicz 2006) due to melting of the ice–sheet and decrease in the global ice volume (Peltier 2002). Northern areas around the Baltic Sea experienced isostatic uplift and sea level regression, whereas isostatic subsidence in the southern areas caused transgressions. Owning to isostatic uplift ancient beach formations, lagoons and coastal lakes remained at different levels, and their deposits have been widely used to reconstruct the water level changes and shore displacement curves (e.g. Berglund 1971; Kessel, Raukas 1979; Svensson 1989; Björck 1995; Miettinen 2002; Gelumbauskaitė 2009). After deglaciation northern and western Estonia underwent rapid uplift, up to 26 mm yr –1 (Kessel, Miidel 1973), which at present has slowed down to 2–2.8 mm yr –1 (Torim 2004). In Estonia the early post–glacial history of the Baltic Sea from Baltic Ice Lake through the Yoldia Sea to Ancylus Lake has been discussed in numerous recent publications (e.g. Saarse et al. 2003, 2007; Vas- siljev et al. 2005; Veski et al. 2005; Heinsalu, Veski 2007; Rosentau et al. 2009), but the development of the Litorina Sea has received little attention (Saarse et al. 2009a). Episodic saline water ingression into the Baltic Sea basin started about 9800 cal yr BP (Eronen et al. 1990; Andrén et al. 2000), however, signiicant rise in salinity occurred between 8500 and 8000 cal. yr BP, marking the onset of the Litorina Sea (Andrén et al. 2000; Berglund et al. 2005). The development of fully brackish water conditions in the Baltic Sea basin was a time–transgressive process that lasted several hundred years (Hyvärinen et al. 1988; Kunzendorf, Larsen 2009). The onset of the Litorina Sea in the area of the Gulf of Finland coincides with the transgres- sion that resulted from the rising global ocean level. After the Litorina Sea transgression several islands emerged in the southern part of the Gulf of Finland.