Holocene environmental changes during transition Ancylus-Litorina stages in the Gdansk Basin, south-eastern Baltic Sea

Abstract

Two sediment cores have been obtained from the southern and eastern parts of the Gdansk Basin for lithological, geochemical and diatom analysis. The data revealed provides information about environmental changes during the transition of the Ancylus Lake to the Litorina Sea stages. The Ancylus Lake transgression and regression phases have been well traced in the diatom flora of the shallower, eastern slope of the Gdansk Depression, whereas mentioned water level changes have not been detected in the deepwater (southern) part of the basin. The Litorina Sea has been clearly defined according to geochemical, lithological and diatom analysis. The Initial Litorina Sea transition was observed as gradually increasing numbers of brackish water diatoms and higher contents of C org and N in the sediments, when saline water influx reached the basin before 7600±184 cal. yr BP.

Stages of the Baltic Sea evolution in the geochemical record and radiocarbon dating of sediment cores from the Arkona Basin

“…Changes in the geochemical composition confirmed that the environment changed rapidly from the freshwater Ancylus Lake into the marine Littorina Sea as it was described in the previous studies (Emelyanov and Vaikutienė 2013, Kostecki and Janczak-Kostecka 2012, Moros et al 2002. The increasing content of loss on ignition, biogenic silica reflected an increase in the primary production that was stimulated by an inflow of saline, oxygenated water enriched with nutrients.…”

“…The oldest date of 10100 cal BP of a minor marine inflow and the date of 7850 cal BP of a fully marine environment were retrieved in the Bornholm Basin . The onset of marine environment in the Gdańsk Basin was dated at around 7600 cal BP (Emelyanov and Vaikutienė 2013). The youngest date of 7200 cal BP was found in the Arkona Basin (Moros et al 2002, Rößler et al 2011.…”

“…The inflow of sea waters was accompanied by higher concentrations of sulfur that caused bonding of iron into sulfide minerals (Sohlenius et al 2001). Emelyanov and Vaikutienė (2013) reported that the freshwater Ancylus Lake environment could be accompanied by oxygen deficiency that caused dissolution of magnesium and iron ions in the bottom water. Thus, the inflow of oxygenated sea water caused bonding of magnesium and iron into minerals and their deposition at the bottom.…”

“…A similar age of the transition period between the Littorina and PostLittorina stages was determined in the Bornholm Basin (2750 cal BP; Andrén et al 2000) and in the Gulf of Gdańsk (3000 uncorrected 14 C; Witkowski 1994). The most characteristic feature of this stage was a gradual decrease in the marine character of the environment with a slight decline of salinity recorded by diatom composition (Emelyanov and Vaikutienė 2013, Witak and Dunder 2007, Witkowski 1994. A slight decline of the marine character of the environment was also reflected in the geochemical composition, i.e.…”

“…(Lemke et al 1998 (Berglund et al 2005). The latest studies from the southern Baltic basins indicated the onset of the Littorina transgression at 7200 cal BP in the Arkona Basin (Rößler et al 2011) and at 7600 cal BP in the Gdańsk Basin (Emelyanov and Vaikutienė 2013).…”