Abstract. We propose a new concept of the Weichselian ice dynamics in the south-western
sector of the Baltic Sea depression. The review of existing geochronological
data from Germany, Denmark and southernmost Sweden in combination with new
optically
stimulated luminescence (OSL) data from the German Oder Lobe area is the basis for a reassessment and
an improvement of previous ice dynamic models. Factors like the pre-existing
topography, glaciotectonic features and the occurrence of till beds and
inter-till deposits of varying origin are also taken into consideration for
our process-based reconstruction of the sedimentary environments close to
the ice margin and hence the ice dynamics of the Scandinavian Ice Sheet
(SIS). During the early MIS 3 (marine isotope stage), the late MIS 3 and MIS 2, the SIS
advanced into present-day terrestrial areas around the south-western Baltic
Sea Basin. The first ice advance during the warming phase in early MIS 3 is poorly
documented as the Ellund–Warnow Advance in Germany but may be correlated with
the numerically dated Ristinge Advance in Denmark and Sweden. The late MIS 3 advance in contrast is reliably documented. It shaped the
landforms of the Brandenburg Advance and the maximum Weichselian ice extent in
the Oder Lobe area in north-eastern Germany and occurred contemporaneously with the
Klintholm Advance in southern Sweden and Denmark. The lack of a
corresponding till in various cliff profiles along the Baltic Sea coastline
between southern Schleswig-Holstein and the island of Rügen can be
explained by the distinct lobate structure of this ice advance, which was
strongly guided by the pre-existing low-lying topography. We propose the
horst of Bornholm, Denmark, acting as an ice divide, with ice-dammed lakes existing on
the lee side between two glacier lobes. This lobate structure had not been
considered in previous conceptual models, which led to seemingly
conflicting chronological and stratigraphical interpretations. Our
introduction of the lobate structure for the first time resolves these
contradictions and integrates the data in a coherent model. The dynamics of the MIS 2 readvance to the Last Glacial Maximum (LGM)
extent were clearly different to the previous advance and were most likely
characterized by a more uniformly advancing ice front with a less lobate
structure which also overrode the horst of Bornholm and the island of
Rügen. This advance reached the maximum Weichselian ice extent in some
parts of the south-western SIS, but, in the Oder Lobe area, it is proven to
have terminated at a lesser extent than the early MIS 3 advance, but it did
shape the most prominent morphological landform record of the last glacial
cycle. In order to advance the reconstruction of Weichselian ice dynamics in the
future, we strongly suggest using both an MIS-based terminology and a
process-based approach in the interpretation of geochronological data to
live up to the dynamic nature of continental ice sheets.
