Crevasse-fill forms - Bridging the gap in glacial geomorphology between East and West based on a case study from eastern Poland

摘要

Genesis of crevasse-fill forms was clearly explained and ascribed to surging ice based on research made particularly in contemporary-glaciated areas of high latitudes. Nonetheless, the understanding and explanation of their formation is still not conclusive for Pleistocene glacigenic forms developing in crevasses what makes differences in their interpretation visible in glacial geomorphology of the East and West. Those forms in the East are still linked to stagnant Pleistocene ice-sheet dynamics and still named crevasse-fill forms what makes a huge misunderstanding in comparison of these modern and ancient equivalents. This paper makes an attempt to investigate this topic through comparison of features of "stagnant" and "surging" crevasse-fill forms, i.e. their morphology, lithology, location against direction of ice advance and - for the first time - sedimentary environment of crevasse-fill deposits. Recognition of deposits with using lithofacies analysis became a crucial method for classification of Pleistocene glacigenic forms, especially in the East. Thus, research on presented tree examples of so-called "crevasse-fill forms" based on facies analysis of sedimentary environments and their other characteristic features allowed to explain the characteristics of landforms developed from stagnant ice and to exclude them from the group of their "surging" equivalents. This misinterpretation results from different schools of thought in glacial geomorphology of the East and West. Based on presented research, no prerequisites were documented to compare these landforms, because the palaeogeographical conditions of their development are completely different.