Mid- and late-Holocene shoreline changes along the southern coast of the Gulf of Finland

Abstract

In response to glacio-isostatic rebound in Estonia, a relative sea level fall occurred during the midand late-Holocene, and as a result, lowland regions in northern Estonia have experienced an evolution from sea to land. The midand late-Holocene shoreline changes along the southern coast of the Gulf of Finland were reconstructed, using litho-, bioand chronostratigraphical proxies from four lakes. The lakes are located within the Gulf of Finland drainage system at different altitudes between 18 and 4 m above the present sea level. The isolation from the sea and the onset of freshwater lacustrine sedimentation occurred in Tänavjärv basin at 5400 cal yr BP, in Klooga basin at 4200 cal yr BP, in Lohja basin at 2200 cal yr BP and in Käsmu basin at 1800 cal yr BP. Through the application of GIS-based analysis, a modern digital terrain model and reconstructed past water level surfaces, we present a series of scenarios of shoreline and palaeogeography changes occurring since 7800 cal yr BP. The land uplift rate, which was approximately 2.8 mm yr-1 7800 cal yr BP in the surroundings of Tänavjärv, has decreased to 2.2 mm yr-1 at present and that at Lohja from 2.4 to ca 2.0 mm yr-1, respectively. The relative sea level curves show a land uplift decrease, which is nearly linear since the mid-Holocene.