HOLOCENE MARINE INGRESSIONS IN THE COASTAL ZONE OF THE POMERANIAN BAY BASED ON RADIOCARBON ASSAYS

In recent years, a team at the Geology and Paleogeography Unit, Marine Sciences Institute, University of Szczecin, has been performing geological, geochronological and paleogeographic surveys in (i) the Szczecin Lagoon and Swina Gate Sandbar and (ii) the estuary section of the Rega river valley near Mrzezyno. These studies have helped to examine and identify not only the distribution of fossil marine sediments but also their lithological and sedimentological characteristics. The age of marine ingressions and regressions in the coastal zone of the Pomeranian Bay were determined using approximately 170 radiocarbon assays. It was found that the marine ingression associated with the 'Littorina transgression' was not synchronous at these two areas. It started earlier in the Mrzezyno area, ca. 8300-8200 cal BP. In that first phase, marine sediments developed as tightly packed sands containing a few fragments of shells. In several profiles, these deposits were separated from the bottom and top with layers of peat, thus allowing an indirect determination of their age. The next phase of ingression began about 7300 cal BP. These younger marine sediments already contained quite numerous shells of marine malacofauna, especially Cardium glaucum, often found in a life position. In the area of the Szczecin Lagoon and Swina Gate Sandbar, the oldest marine ingression started as early as about 7350 cal BP. The quite clear trace is a considerably thicker series of marine sands with numerous sea shells representing marine and brackish-marine environments, including Cardium glaucum shells in a life position, which made it possible to identify the age and the rate of accumulation of marine sands.