Stefan Kozarski

Abstract

A time-scale calibrated in radiocarbon years has allowed the last glacial episode in northern Poland to be ascribed to the interval of ca 22 000-13 200 yr BP and its maximum of approximately 20 000 yr BP. An attempt has also been made to present a map of deglaciation isochrones and to approximate the age of major ice-sheet positions; i.e. the Poznań Phase: 18 400 yr BP, the Chodzież Subphase: 17 200 yr BP and the Pomeranian Phase: 15 200 yr BP. Whilst occupying the main positions, the dynamics of the ice sheet front had varied to a higher degree than it was assumed in the former deglaciation models with special preference for the zonal ice sheet waning model. Evidence has been provided by new studies based on the complex facies analysis of marginal phenomena. It allows construction of more realistic depositional models in order to establish a dynamic tendency (D,) of the ice-sheet front on the basis of depositional efficiency (De) estimation. The procedure by means of which models can be constructed is a new methodological proposal in studying the ice-sheet marginal phenomena produced in low energy conditions.

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

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.

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

Stefan Kozarski, Committee of Geographical Sciences, Polish Academy of Sciences
Jan Szupryczyński [jan.szupryczynski@geopan.torun.pl], Institute of Geography and Spatial Organization Polish Academy of Sciences, Kopernika 19, 87-100 Toruń, Poland

Abstract

A considerable growth of interest in the problem of eolian phenomena in West-Central Poland could be traced in the course of the last decade. As a result, numerous papers dealing with this subject have been pu-blished. The growing interest has been followed by a broadening of the scope of problems under consideration. Whereas in previous publications morphological features of the dunes as well as the structural and textural features of their sands has been accentuated, the more recent works are rather concerned with problems of chronology of phases of intensive eolian activity leaving their marks not only in the relief, but also in the formation of cover deposits and the fossilization of Late Würm ice-wed-ges. Thanks to detail investigations in a large number of sites (Fig. 1) the relation between dune sands and peats has been established; in ad-dition, fossil soil appearing in dunes have been examined. The age of peats and fossil soils was determined by means of the pollen analysis, and in some sites archeological materials and radiocarbon 1 dating have also been used as age indicators.

The facts gathered allow for assuming that the main, climate-condi-tioned phases of eolian activity coincided with the Late Würm cold pe-riods. Eolian activity in Holocene, was limited in space, and not caused by climatic changes, but by man intervention in the geographical en-vironment.

Stefan Kozarski, Committee of Geographical Sciences, Polish Academy of Sciences
Bolesław Nowaczyk, Department of Plant Taxonomy and Geography Adam Mickiewicz University Poznań
Karol Rotnicki, Quaternary Research Institute, Adam Mickiewicz University, Poznań, Poland
Kazimierz Tobolski, Quaternary Research Institute, Adam Mickiewicz Universitety, Fredry 10, 61-701 Poznań. Poland

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