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EN
The article presents the results of geological and geomorphological research concerning load-cast structures outcropping in the alluvial terrace sediments of theWisłok River in the Fore-Carpathian Erosional Valley. Given the large dimensions of these structures, reaching 1.5 m in some places, as well as their strong accumulation and diversity (i.e. drop-like and pocket-like structures), the authors attempted to establish the environmental factors that had determined the development of the structures in periglacial deposits of the Weichselian Glaciation. The structures were analysed in two accessible outcrops where sediments are represented by flood rhythmite and organic deposits, overlain by channel sands. Sandy load-cast structures occur in flood rhythmite and loamy deposits. The formation of load-cast structures probably started due to earthquakes in the Upper Pleniglacial period. The various shapes of load-cast structures were constrained by the various physical properties of the sediments and the escape of water during the deformation process.
EN
The paper presents the results of geomorphological studies and pollen analysis performed for alluvial deposits at 2 sites situated in the Wisłok River valley. The deposits consist of thin layers of organic muds filling palaeochannels or thermo-karst lakes of the Wisłok River, dated at the Interpleniglacial (Grudziądz Interstadial) of the Vistulian Glaciation. These deposits build the lower part of a sand terrace, 8-12 m high, and outliers of this terrace buried by overbank alluvial sediments within a floodplain. The samples for pollen analysis were taken from a natural undercut in the Wisłok River channel and from a sand pit dug to a greater depth. The pollen diagrams prove the existence of trees (forest-steppe) including primarily Pinus sylvestris, Betula t. alba, Pinus cembra and Larix. The diagrams do not show a clear tendency of a plant succession and thus of any distinct climate changes. The sedimentation took place under cool, boreal climate conditions. The occurrence of several layers of organic and sand deposits in the sections does not reflect rhythmic warm/cold climatic oscillations documented in the Interpleniglacial alluvial sequences in Western European rivers, but is a result of vertical channel fluctuations and facies changes.
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