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Ice-Sheet Dynamics of Warta Glaciation (Saale) in the Marginal Zone of Knyszewicze Area, Northeastern Poland

Rychel J., Woronko B., Karasiewicz M. T., Szymczuk P., Morawski M.

Studia Quaternaria

2015

Vol. 32, Nr 2

79--90

The paper presents a research on a marginal zone near Knyszewicze in the southern part of Sokółka Hills (northeastern Poland). Terminal moraine hills are arranged amphitheatrically in a lobal pattern. Dynamics of the Knyszewicze frontal ice-sheet lobe during the Saale Glaciation and successive stages of the marginal zone near the village of Knyszewicze were reconstructed based on sedimentary and geomorphological analysis, using a digital elevation model and morpholineaments. Three main phases of the Knyszewicze glacial-lobe activity were identified including accumulation of glaciofluvial deposits, advances of the ice margin and ice-lobe retreat. Moraine hills developed at a stable ice-lobe terminus, initially as short end-moraine fans with the following sequence of lithofacies Gh=>SGh=>Sh or Gm=>Gh=>Sh. Such a sequence indicates cyclic sheet-floods. During a small but dynamic advance of the ice sheet terminus, these deposits were moved forward and monoclinally folded, then furrowed with sloping faults due to horizontal pressure. Typical thrust-block push moraines developed in this way. Ice sheet advance took place when permafrost was present in the substratum and very high water pressure occurred at glacial terminus. Inside a lobal configuration of moraines, there is a rich inventory of glacial forms with a classic terminal depression in the central part. Based on this landform pattern, their shape, rhythm and glaciotectonic disturbances, the land relief may be referred to as a hill-hole pair. The structure of Horczaki Knoll, deposited on the sub-Quaternary tectonic structure, significantly contributed to a development of this marginal zone.

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

Morawski W.

Geological Quarterly

2003

Vol. 47, No 4

339–-356

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°.