Chronostratigraphy of late pleistocene fluvial deposits in the Wisłok River valley between Rzeszów and Łańcut, South Poland

This paper presents results of absolute dating of alluvial sedimentary series forming a rendzina terrace (higher floodplain) 7-8 m high above the Wisłok River channel and a sandy terrace 8-10 m high in the Subcarpathian Pradolina section of the Wisłok River valley. The organic mud infilling fossil depressions (palaeochannels?) in the lower part of the rendzina terrace have been dated by the radiocarbon method to more than 38,500 BP. The organic series occurring within the sandy terrace yielded three ages >36,000 BP. Results of palynological analyses carried out on both sites indicate tundra or forest-tundra environments with water-filled depressions at the time of organic sediments deposition. The top of the 8-10 m high sandy terrace is built of fluvial sands and eolian cover sands with dunes in the uppermost part. Their age has been established by means of the OSL method to 11.2±0.9 ka BP. The younger alluvial inset fill is formed of sands and silts with involutions occurring under Holocene muds. They were deposited by a braided river during the Upper Plenivistulian as indicated by two other OSL dates of 22.2±2.2 ka BP and 14.0±1.5 ka BP. Within the rendzina terrace the youngest series of Vistulian age is built with peats and silts, infilling the wide depression at the foots of sandy hillocks, dated to about 11,800 BP.