Littorina and post-Littorina sedimentological processes in the Odra Channel in light of multidisciplinary investigations of a sediment core, Pomeranian Bay, southern Baltic Sea

Abstract

A multi-proxy study was performed on a gravity core supplemented by acoustics profiles and new radiocarbon dates of macrofossils found in the sedimentation history of the Odra Channel during the Holocene. The channel is located in the western part of Pomeranian Bay and was shaped by a pre-Odra river that flowed northwest along the Peene valley and the eastern part of Rügen Island during a drop in Yoldia Sea level. The acoustic profiling enabled identification of glacial till, the Baltic Ice Lake and Littorina sediments. The studied core penetrated only marine sediments deposited during Littorina and Post-Littorina stages and was the subject of grain size, geochemical and diatom analyses. The age of appearance of a marine environment in the studied area was estimated at 7200 yrs BP. The performed studies enabled division of the core into three phases of environmental evolution: the Littorina I phase occurred during the time span 7200–6000 yrs BP and is described as a shallow water brackish basin with a low rate of sea level rise and favourable conditions for biogenic production, the Littorina II phase dated at 6000–3800 yrs BP reflects a deep marine environment with relatively high salinity and greater current velocity, and the last phase, Post-Littorina, covered the last 3800 yrs BP and turned out to be a strongly energetic environment with decreasing salinity. The change from Littorina II to Post Littorina phase correlates clearly with a change in the acoustic reflection. Core analyses could be associated with extreme stormy cold events known as Bond events dated at 5900–5500 yrs BP and 4200 yrs BP evidencing the final destruction of the Odra Bank barrier.