Wybrane geochemiczne cechy osadów wypełniających starorzecza w dolinie Dolnej Pilicy w okolicach Warki

Research of deposits filling the oxbow lakes in the Pilica valley near Warka has proved that they are highly varied lithologically and geochemically. Heavy metals in these deposits were used to identify the periods of varying influence of man (anthropopressure). The lithological variety of the deposits filling the oxbow lakes reflects the changes in the distance of the cut-off oxbow lake from the active channel and in the different conditions of deposition. The deposits originated in different ages, filling the oxbow lakes in the Pilica valley, demonstrate same similarities as regards the variability of textural features and the heavy metals content to the channel and non-channel deposits accumulated in the Vistula river over different periods of time (Szwarczewski 1999). The decreasing content of trace minerals, corresponding to the distance from the active channel and the depth of the profile, which has been revealed in the channel and high water deposits, is not so strongly marked in the case of deposits filling the oxbow lakes. This is due to a discontinuity in the sedimentation record, which - in the river valleys - mainly depends on the intervals between, and duration of floods, as well as the scope of regulation works. Long periods of drought, with limited precipitation, coupled with comprehensive regulation works (which shorten the river course and result in incision processes) may led to the creation of sedimentation gaps in the floors of river valleys, particularly within oxbow lakes.