Spatial variability of Holocene sediments in light studies of cores from the Arkona Basin, south-western Baltic Sea

Abstract

Presented studies performed on two gravity cores with acoustic profiles, new radiocarbon dates from macrofossils, and results from previous studies, have outlined the spatial variability of Arkona Basin sediments. Analyses of diatoms, grain size, and geochemistry revealed characteristics of the depositional environment developed during the Ancylus and Littorina stages. New geochemical data, along with previous results from western Arkona Basin using the PCA method, revealed division sediments across three groups, explained by terrigenous silica, organic matter, and calcium content factors. The grain size distribution together with geochemical parameters confirmed the existence of the erosional brackish-water basement, visible in the acoustic profiles as the distinct reflector R3. Reflector R3 is located at the boundary between Ancylus Lake and Littorina Sea sediments and stands base of the initial Littorina Sea. Comparing grain size characteristics of the sediments deposited during the Littorina Sea stage revealed spatial diversity of the depositional environment in the Arkona Basin. The western cores located close to Darss Sill during the onset of the Littorina stage confirmed a calm depositional environment, while in the northern part of the basin, dynamic activity of bottom currents was observed. During the second phase of the Littorina stage, dated around 6 - 5 ka cal. BP, there was an intensification of sediment transport and deposition processes, accompanied by the appearance of marine diatom forms in the western cores. Simultaneously, relatively calm depositional conditions existed in the northern and central parts of the basin.