Geographia Polonica (1988) vol. 53

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Depositional models and ice-front dynamics in northwestern Poland: a methodological approach

Stefan Kozarski

Geographia Polonica (1988) vol. 53, pp. 43-52

Abstract

Ice marginal deposits and forms together with the so-called directional elements oftills, streamlined forms and striated rocks are a fundamental source of informationabout the directions of movement and extent lines of Pleistocene ice sheets. Theirinformative functions are best in areas of the last glaciation because of freshness ofsedimentological and geomorphic record. Hence, they have been most successfully usedin establishing the maximum extent of the last Scandinavian ice sheet and its waningphases in the North Polish Plain at an over-regional (Bartkowski 1969; Galon 1968,1972; Roszko 1968; Różycki 1973) and regional (Bartkowski 1967; Karczewski andRoszko 1972; Kliewe and Kozarski 1979; Kozarski 1962; Rotnicki 1963; Żynda 1967)spatial scale. The growing knowledge on glaciarization processes and ice sheet extensionbrought also increasing information about ice-front dynamics. It results from descriptionspresented in literature on this subject that attention has been mostly focused ontwo extreme states of ice-front behaviour namely:(1) the state of high activity and advance recorded by the presence of thrust ridgescontaining glaciotectonic structures, and(2) the state of complete passiveness represented by disintegration features, i. e.dead-ice forms and deposits containing gravity deformation structures.The first state is easily detectable, wheras the other one poses more interpretationproblems because the preceding it slow ice-front advance and/or dynamic equilibriumrecorded by deposits, except some cases (Kasprzak and Kozarski 1984; Kozarski 1978,1981; Roszko 1968), has been ignored. Direct causes comprised here déficiences in toogeneral programmes and very few detailed research procedures which did not promotecareful identification and advanced interpretation of deposits occurring in marginalzones. As a consequence simplifications in the reconstruction of déglaciation processappeared with an exaggerated preference for the model of vast zonal ice-sheet wastage.This gave rise to search for new approaches in studies of deposits in marginal zonesso that a better, broad and objective basis might be provided for a reconstruction of thelast ice sheet behaviour in frontal parts during déglaciation.

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Stefan Kozarski, Committee of Geographical Sciences, Polish Academy of Sciences