Hydrographic thresholds in the western Baltic sea: Late Quaternary geologyand the Dana River concept

Since the final Weichselian deglaciation the water exchange between Kattega t and the Baltic Sea and hence the palaeogeographical development of the (w estern) Baltic has been controlled by a number of sills. Major thresholds a re found at the southern entrance of the Great Belt and in the Darss Sill a rea. The easternmost of these structures is formed by Late Weichselian sand s at a level of 24 m below present sea level (bsl) at the Falster-Rugen san d plain. A second threshold consisting of till was found within the Kadet C hannel at a level of 23-24 m bsl. Thus, we exclude water exchange between M ecklenburg Bay and the Arkona Basin at levels below 24 m since the end of t he Pleistocene. A high resolution sediment echosounder survey at the triple junction area of Langeland Channel, Vejsnaes Channel and Winds Grave Chann el showed outcropping glacial deposits. Narrow channels incised at a level below 25 m bsl are filled partly with fine grained organic rich late- and p ostglacial sediments. Assuming no substantial crustal movements in this are a in the Holocene no Ancylus Lake drainage at a level deeper than 25 m bsl is likely to have occurred here. (C) 2001 Elsevier Science B.V. All rights reserved.