MARINE GEOLOGY AND GLACIOLOGY
Ice stream Weichselian Young Baltic Ice RESEARCH

Stig A. Schack Pedersen, Geological Survey of Denmark and Greenland, Thoravej 8, DK-2400 Copenhagen NV, Denmark. sasp@geus.dk
Leif Aabo Rasmussen, Geological Survey of Denmark and Greenland, Thoravej 8, DK-2400 Copenhagen NV, Denmark.

During the systematic mapping of the northern part of Lolland and the Smålandsfarvandet archipelago till fabrics have been measured in the Lolland Till Formation. The till represents the prominent lithostratigraphic unit deposited by the Late Weichselian Young Baltic Ice advance, which from its main centre in the eastern Baltic transgressed over the southern part of Denmark. The western limit of this ice sheet is situated in eastern Jylland and central part of Kattegat.

The till fabric analysis here presented are based on common principles known to the international glacial geologists as for instance outlined by Visser (1989). In the till fabric analysis the stereoplot program SSWIN was applied and the Kamb (sigma) counting was selected for the calculating operation. The direction of the fabric (large arrow in the stereograms presented in the Fig. 1) is given by the maximum density distribution, eigenvector 3 (E3). The evaluation of the fabric is based on Volmer's Fabric Indexes in a cluster-girdle-uniform triangular distribution plot, hereafter referred to as the cgu-index. In this diagram a cluster distribution corresponds to one well defined direction, a girdle distribution corresponds to two or more directions in the same plane, and finally the uniform distribution represents no preferred direction. A girdle distribution in the till fabric analysis normally refers to fabric axes distributed in the horizontal plane or in a weakly plane tilted away from the direction of shear movement. From the girdle analysis it can not be seen whether the distribution of clasts is an A-axis or B-axis orientation, which is only interpreted from the contouring display in the stereogram.

Various aspects of interpretation of till fabric diagrams are discussed, and the main question to be addressed is the liability of interpretations based on a statistically not well defined cgu-index.

The interpretation for the flow of the Young Baltic Ice in the south-eastern Baltic and southern part of Denmark advocates a main stream from east towards west with a substantial northerly spreading vector during the progressive advance. It is inferred that a similar spreading towards the south affected northern part of Germany as also indicated by Stephan (1994).

Till fabrics Vejrø-Torrig Vig area
Vejrø	Rågø	Egholm
Torrig Vig	Kragenæs Øre	Kragenæs S
Till fabrics Birket-Fejø area
Birket	Skalø	Klintgård
Skoven	Nørrehede A	Nørrehede B
Till fabrics Smålandsfarvandet
Isemosebjerg	NV-Kyst A	NV-Kyst B
Ved havnen	Østerklint	Askø
Till fabrics Sakskøbing Fjord area
Klintegård	Saltvig	Blans Hoved
Skifterne	Oreby	Vestermark

References:
Stephan, H.-J. 1994: Det Jungbaltische Gletschervorstoss in Norddeutschland. Schr. naturwiss. Ver. Schlesw.-Holst., 64, 1-15.
Visser, J.N.J. (1989) Stone orientations in basal glaciogenic diamictite: four examples from the Permo-Carboniferous Dwyka Formation, South Africa. Jour. Sed. Petrology, 59, 935-943.

Edited by: Niels E. Poulsen, GEUS