The Baltic Ice Lake in the southwestern Baltic: sequence‐, chrono‐ and biostratigraphy

Abstract

Jensen, J. B., Bennike, O., Witkowski, A., Lemke, W. & Kuijpers, A. 1997 (September): The Baltic Ice Lake in the southwestern Baltic: sequence‐, chrono‐ and biostratigraphy. Boreas, Vol. 26, pp. 217–236. Oslo. ISSN 0300–9483.This multidisciplinary study focuses on late‐glacial deposits in the Mecklenburg Bay ‐Arkona Basin area. The sequence stratigraphical method has been used on shallow seismic and lithological data, in combination with biostratigraphical work and radiocarbon dating. Glacial‐till deposits underlie sediments from two Baltic Ice Lake phases. Varved clay deposits from the initial phase cover the deepest parts of the basins. A prograding delta is observed at the western margin of the Arkona Basin, prograding from the Darss Sill area. The delta system is possibly related to a highstand dated at 12.8 ka. A maximum transgression level around 20 m below present sea level (b.s.l.) is inferred, followed by a drop in water level and formation of lowstand features. The final ice lake phase is characterized by a new transgression. The transgression maximum as observed in the Mecklenburg Bay is represented by transgressive and highstand deltaic deposits. These also indicate a maximum shore level of 20 m b.s.l. The deltaic sediments that contain macroscopic plant remains and diatoms have yielded Younger Dryas ages. Mapping of the late‐glacial morphology of the Darss Sill area reveals a threshold at 23 to 24 m b.s.l. This means that the Baltic Ice Lake highstand phases inundated the Darss Sill, which implies that the westernmost extension of the Baltic Ice Lake reached as far as Kiel Bay. Forced regressive coastal deposits at the western margin of the Arkona Basin mark a lowstand level of around 40 m b.s.l. caused by the final drainage of the Baltic Ice Lake. The lowstand deposits predate lacustrine deposits from the Ancylus Lake, which date to approximately 9.6 ka BP.