Czwartorzędowe ruchy tektoniczne a rzeźba przełomu Dunajca przez Beskid Sądecki

Witold Zuchiewicz


Quaternary tectonics and the relief of the Dunajec River gorge in the Beskid Sądecki Mountains (Polish Western Carpathians)

The paper discusses the influence of young tectonics upon the morphogenesis of the antecedent gorge of the Dunajec River cutting the flysch rocks of the Beskid Sądecki Mountains (the Polish Western Carpathians) (fig. 1). The method applied was the method of detailed geomorphological survey and 35 levelling cross-sections across the valley were performed. In the slopes and in the bottom of the Dunajec River gorge there are preserved parts of four Pleistocene gravel covers (glaciations: Günz, Cracovian, Middle Poland, Baltic). These are rock terraces of relative height: 154 — 161 metres, 47 — 96 metres, 17 — 55 metres and 9 — 18 metres. The rock socle cut during the Great Interglacial (Mindel-Riss) is characteristic for maximum deformations in its longitudinal cross-section. They are particularly conspicuous in the middle and the northern parts of the Kłodno block and in the southern part of the Wietrznica block (fig. 2, 3). In the central part of the gorge the deformations are very weakly marked. The least distortions appear in the erosion plains of the Eem Interglacial. Zones of local deformation of cross-section are prominent in the vicinity of Kłodne, Chlebki and Wietrznica. The above statements allow for the distinction of two blocks raised in Pleistocene. They are the regions of Kłodne — Brzegi and Wietrznica — Boczów. Some deformations are marked in the longitudinal cross-section of rock socles of Holocene terraces. Conspicuous increase of them can be observed at Kłodne and Wietrznica. Above and beneath the gorge the rock basement of the youngest terraces plunges below the recent river bed level. The depth of the consecutive dissections of the rock socles of the Quaternary river terraces are commonly taken for the indication of uplifting. In order to calculate the rate of uplifting movements the dimensions of the consecutive dissections have 'been related to the Ericson and Wallin’s absolute chronological scale of Quaternary. The following intervals in time have been taken into consideration: Günz — Holocene, Mindel — Holocene, Riss — Holocene, Würm — Holocene and Early Dryas— Holocene. The comparison of the results obtained indicates the increasing uplifting intensity in Neopleistocene and in post glacial time (corresponding values in mm per annum : 0.105, 0.05, 0.053, 0.12, 0.7). Double speed drop of the uplifting between Günz — Holocene and Mindel — Holocene can be explained by the loading of the Beskidy foreland by the Cracovian ice sheet. The folded Beskid Sądecki Mountains are cut by faults into several blocks. The respective tectonic units, after the final phase of Alpine orogeny had formed block morphostructures of orders II, III, IV, in Quaternary subjected to different positive movements. Especially intensive uplifting had been marked within the Kłodne and Wietrznicą blocks. The investigations which have been carried out allowed for the isolation of a set of geomorphological characteristics. Their simultaneous appearance in the given territory of the Western Carpathians can indicate the presence of young uplifting movements: 1) deformations in the longitudinal cross section of river terraces, 2) considerable relative heights, 3) convex slope profile with a tendency to become steeper, 4) greater number of the first order valleys and their length in relation to valleys of other orders, 5) increase in slope of the valley and river bed bottoms, 6) presence of river beds cut into bed rock, 7) emphatic supremacy of incision over other channel processes.

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