Late Weichselian and early Holocene shore displacement in the central Baltic, based on stratigraphical and morphological records from eastern Småland and Gotland, Sweden

Abstract: The glacial unloading and resulting isostatic land uplift have together with hydro-isostasy, eustatic rise of sea-level and geoidal changes, ruled the shore displacement of Fennoscandia. Within the Baltic basin, periods of damming and shifts of outlet further complicated the shore displacement during the period studied, c. 12,200-8400 BP. Information on the Baltic history was derived from shoreline observations and studies on sediment cores from lakes formerly directly affected by the Baltic. These cores were analysed with respect to pollen, diatoms, and lithology to determine sequences of Baltic sediments, and dated by a combination of radiocarbon dates and biostratigraphy. The studied areas of southeastern Sweden, mainly central Gotland and the Oskarshamn area, eastern Småland, display a similar course of shore displacement. The Late Weichselian period shows a regression of a slightly decreasing rate between c. 12,200 and 10,300 BP. Then followed a fast drop (25 m) of the Baltic's water level; the final drainage of the Baltic Ice Lake. During the next c. 700 yr, the Yoldia stage, a regression of c. 17 m occurred. This period is mainly characterized by fresh-water diatoms in the Baltic, but at c. 10,000 BP there is evidence of a shortlasting (100-150 yr) period with brackish water. The Ancylus transgression, of c. 11 m, began c. 9600 BP and culminated c. 9300 BP. It was followed by a fast regression of 5-10 m, thereafter the rate of regression decreased. Shoreline gradients shows that the fastest shoreline tilting occurred around 10,000 BP, thus c. 2000 years after deglaciation.