The oxbow sedimentary subenvironment: its value in palaeogeographical studies as illustrated by selected fluvial systems in the Upper Odra catchment, southern Poland

Abstract

Research was conducted in valleys of sinuous rivers that drain medium-high mountain, foreland basin and upland areas, where loose Quaternary deposits predominate. The cyclic pattern determined for deposits of the oxbow sedimentary subenvironment in the Upper Odra Basin can be expressed as a few alternative sequences. The best-developed cycle occurring on a relatively high level of probability, is represented by the unilateral transition from channel to overbank deposits and upwards-bilateral oscillations between overbank and biochemical, as well as biochemical and slope deposits. In the first stage, oxbow filling processes are usually determined by autocyclic factors (resulting from spatial relations between abandoned channels and the active channel). As a consequence, overbank and/or biochemical sediments usually overlie channel deposits. Later, allocyclic processes could easily dominate autocyclic processes. In these cases, overbank, slope and late-Holocene alluvial fan deposits were delivered to oxbow basins as a result of the influence of outside factors such as climate or human impact. In the Upper Odra catchment, facies succession in the sequences of deposits infilling abandoned channels was mainly determined by climatic factors (in the Late Vistulian, early and mid-Holocene) and anthropogenic factors (in the late Holocene, especially in the last dozen centuries or more). The course of sedimentary processes conditioned by climate and human activity was modified by orographic factors associated with spatial relations among abandoned channels and both the active channel as well as valley slopes. However, the geological structure had a smaller influence on the course of sedimentary processes in the oxbows. The diversity of bedrock lithology in the individual drainage areas determined the thickness and lithological features of the given series of deposits but not the facies succession.

Authigenic and allogenic organic remains as an indicator of geomorphological process activity within the floodplain environment: two case studies from Racibórz Basin, southern Poland

“…These fragments of the valley floors were originally formed by a sinuous river from the Late Vistulian to the middle Holocene. As a result, what predominate in the distal zone of the Kłodnica and Osobło-ga valleys are sand-bed meandering rivers, featuring lateral bars built of up to 3 m upward-fining (from gravelly sand to silty sand) alluvial series (Wójcicki 2006(Wójcicki , 2010. In the second order, a large area within the distal floodplain is occupied by organic plains developed in former oxbow lakes.…”

“…In the second order, a large area within the distal floodplain is occupied by organic plains developed in former oxbow lakes. The oldest organic deposits in palaeochannel fills date to the turn of the Older Dryas and Allerød (11780 ± 120 14 C BP) in the Osobłoga valley and to the turn of the Allerød and Younger Dryas (10850 ± 310 14 C BP) in the Kłodnica valley (Wójcicki 2006). According to pollen analysis and 14 C dating, the biogenic accumulation at the Sławięcice 1 site began in the Preboreal phase of the Holocene (Nita, Wó-jcicki 2005).…”

The Valley-Fill Deposits of the Kłodnica River (Southern Poland): Environmental Drivers of Facies Changes from the Late Vistulian Through the Holocene

“…Nevertheless, most drills were located within oxbow fills where local conditions favoured sedimentation and preservation of deposits (see Lewin and Macklin, 2003). Furthermore biogenic deposits, which appear there, enabled dating of the recorded events (Wójcicki, 2006). In order to classify deposits to individual facies lithological features of sediments were analysed and morphogenesis of landforms, composed of them, was defined (Wójcicki andNita, 2004 andWójcicki, 2006).…”

“…Furthermore biogenic deposits, which appear there, enabled dating of the recorded events (Wójcicki, 2006). In order to classify deposits to individual facies lithological features of sediments were analysed and morphogenesis of landforms, composed of them, was defined (Wójcicki andNita, 2004 andWójcicki, 2006). Depending on the place of deposition, within fluvial facies assemblage, channel and overbank facies were distinguished (Fig.…”

“…In effect of intensive overbank sedimentation, lasting almost the last 2000 years, alluvia of vertical accretion occupy the entire width of the Kłodnica valley floor between Pławniowice and Ujazd. The thickness of these deposits varies usually from 0.2 to 0.8 m, although locally exceeds 1.5 m. Intensive Late-Holocene overbank sedimentation is common in valleys of southern Poland, both in the upper Vistula (Alexandrowicz et al, 1981;Szumański, 1986;Starkel, 2001 andMichno, 2004) as well as in the upper Odra basins (Klimek, 1999, 2002and Wójcicki 2006. According to Łajczak (1995), the largest increase of overbank sedimentation rate at the Carpathian Foreland took place from the beginning of the 16 th to the middle of the 20th centuries.…”