New age constraints from the SW Baltic Sea area - implications for Scandinavian Ice Sheet dynamics and palaeo-environmental conditions during MIS 3 and early MIS 2

The study of two cliff outcrops from the Jasmund Peninsula provides new information on the ice-sheet dynamics and palaeo-environmental conditions during MIS 3 and the ensuing transition to MIS 2 in the southwestern Baltic Sea region. We identified interstadial fluvial sediments, with mollusc and vertebrate fauna, which were deposited between 47 and 42 ka in a steppe-like landscape. A subsequent cooling phase led to the formation of a proglacial lake, between 30 and 22 ka, indicated by varve-like, rhythmically bedded silty clay. This proglacial lake formation can be correlated to the blocking of the Baltic Basin by the Kattegat ice advance, previously dated to c. 29–26 ka. The transition from proglacial to terminoglacial lacustrine deposits reflects the immediate advance of the Scandinavian Ice Sheet (SIS) into the study area after the transition from MIS 3 to early MIS 2. The SIS finally reached the area at 23±2 ka (Brandenburgian phase; advance from the northeast). A subsequent ice retreat accompanied by the deposition of meltwater sediments was followed by a re-advance of the SIS, resulting in a glaciotectonic deformation event across the study area. The age control for our study is based on optically stimulated luminescence (OSL). The investigated Pleistocene sediments show ice-free conditions during MIS 3 and early MIS 2, indicating that neither the Ristinge nor the Klintholm advance reached the SW Baltic Sea coast of Jasmund.