Reconstruction of ice sheet movement from the orientation of linearglacial landforms and glaciotectonic deformations near Kronowo (western Mazury, Poland)

Ice sheet movement in northeastern Poland is reconstructed from analysis of the spatial orientation of glacial landforms and glaciotectonic deformations. The orientations of both positive and negative glacial landforms (morpholineaments) of the Vistulian Glaciation were analysed. These landforms form 4 sets and follow an original crevasse system (joint net) within the ice sheet, probably resulting from horizontal stress exerted as the ice advanced from the north. Esker deposits have been glaciotectonically deformed to form a compressional fan fold, due to limited movement of the ice sheet prior to deglaciation. This movement caused the ice crevasses to be tightened and cut by strike-slip faults. Movement here was from the NNW, as determined from the orientation of deformations. Thus, the ice-flow direction changed at least by 10° during the last phase of the Vistulian Glaciation. If the ice rotated the northeastern portion of the esker, this change may have amounted to 30°.