Osady rzeczne i roślinność interpleniglacjału zlodowacenia Wisły w dolinie Wisłoka między Rzeszowem a Lańcutem

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.