Structural and textural response to dynamics of fluvioglacial processes of the Rzymsko esker sediments, Central Poland

Abstract

The study was conducted in the Rzymsko esker, in the Eastern part of the Turek Upland Plain, within the range of the Warta Glaciation (Saalian II). The form was accumulated in a tunnel valley, which was partially filled with esker sediments. Lithofacies analysis, extended by a detailed analysis of clasts, made it possible to identify a considerable variability of sedimentation conditions. At the initial stage, transport and accumulation of sediments took place in the conditions of high energy hydraulic flows or hyperconcentrated flows. The flow energy rose cyclically, which was recorded as sediments coarsening. Deposits of boulders as well as massive and cross-bedded gravels were identified, a record of catastrophic glacial floods. During the later stage of esker formation, sandy and gravelly sediments were accumulated in an open crevasse. The strong erosional force of subglacial water is confirmed by an extremely high content of local rocks in the gravelly fraction (30–87%) and its very good roundness. Zingg shape analysis (1935) revealed a clear predominance of oblate forms among local clasts and equant fennoscandian erratics. A dependency was also found between the processing method and petrographic characteristics.