Późnoplejstoceński rozwój doliny Niemna w rejonie Grodna na Białorusi

Leszek Lindner, Aleksander Sańko


Late Pleistocene evolution of the Niemen River valley near Grodno in Belarus.
A b s t r a c t. Based on geological and paleobotanic data, the oldest valley system of the Niemen River is linked in the study area with a river located southward of Grodno, within a parallel valley from the Alexandrian (Mazovian) Interglacial. The foundations of the present-day, almost meridian course of the Niemen River valley, are connected with a system of post-glacial lakes from the Sozhian (Wartanian) Stadial of the Pripethian (Odranian) Glaciation, later filled with organic deposits of the Muravian (Eemian) Interglacial. Analysis of six sites with these deposits (Pyszki, Rumlówka, Poniemuń, Żukiewicze, Bohatyrowicze and Kniażewodce) indicates that they represent three lakes located at different altitudes. During the maximal range of the Dvinian (Main) Stadial of the Poozerian (Vistulian) Glaciation, the lakes were beyond the range of the ice-sheet. At this time, the highest located deposits of the Poniemuń-Żukiewicze lake were covered by sander sediments, whereas the Bohatyrowicze-Kniażewodce and Pyszki-Rumlówka lakes that were located at lower levels, were covered by fluvio-periglacial deposits and varved clays of the Skidel ice-dammed lake. Retreat of the ice-sheet of the Dvinian Stadial, resulting in outflow of water from the Skidel ice-dammed lake through the area with the two lower interglacial lakes, triggered the formation of a system of the Niemen River supra-flood terraces above them. Accumulation of the highest of these terraces (VI), during the first phase of the Skidel lake outflow, marks the beginning of the present-day Niemen River valley formation that probably began in the younger phases of the Dvinian ice-sheet retreat. Further evolution of the valley is linked with the Late Glacial formation of the middle (III-V) supra-flood terraces and with the Holocene formation of the lower (II, I) supra-flood terraces.

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