| Popis: |
Reconstruction of fluvial style changes in the San River in the Subcarpathian Basins is based ongeomorphological and sedimentological analyses. The time control of alluvial fills and temporalchanges in the river channel are derived from radiocarbon and optically stimulated luminescencedating combined with independent pollen-based biochronostratigraphy. The results showed that thealluvial plain of the braided (BR) or braided-meandering (BR-M?) river was abandoned before12,800 cal BP. Large meanders (LM) were cut off in the older part of the Younger Dryas (YD; ca.12,600 cal BP), and in the younger part of this period (ca. 12,450 cal BP). The small meanders (SM)developed at the end of the YD and were abandoned at the onset of the Preboreal (PB; ca.11,550cal BP). The erosion phase at the YD-PB transition, reported from many valleys in Central Europe,was not confirmed in the study area. The full cycle of San River channel transformation (BR (BRM?)->LM->SM); was estimated to be approximately 1200 years. According to the palynological data,open pine forests with birch that survived from the end of the Allerød dominated the landscape ofthe river valley during the YD cooling and did not undergo major changes during the warming in theearly PB. Therefore, we assume that the influence of vegetation changes in the San River channelpattern transformation was nonsignificant. The location of the studied palaeochannels in thefloodbasin filled with silty clayey deposits may have influenced the formation of relatively narrowand deep channels, than that of much the wider and shallower meanders from the YD, situatedseveral kilometres downstream of the surveyed sites. |
