New insights into the glacial history of southwestern Poland based on large-scale glaciotectonic deformations – a case study from the Czaple II Gravel Pit (Western Sudetes)

Abstract

This paper presents the results of structural and sedimentological studies carried out in the outcrops of Quaternary (Middle Pleistocene) deposits near the village of Czaple in Lower Silesia, Western Sudetes. Fluvial sands, gravels and glacial tills traditionally assigned to the Middle Polish Pleistocene Glaciations (Odranian Glaciation) crop out in the active gravel pit Czaple II. In these deposits, the authors have recognised and documented numerous mesoscale glaciotectonic deformation structures that were previously undescribed from the mountainous part of the Sudetes. These structures represent effects of sediment deformation in both proglacial and subglacial settings, and include such features as asymmetrical and disharmonic folds, thrusts, steeply inclined reverse faults, normal faults and conjugate sets of fractures. Based on the orientation of kinematic indicators associated with the faults and fracture planes (slickensides, hackles, grooves, R-shears) within the fine-grained sediments and in sands and gravels, an S- and SE-directed horizontal compression due to ice-sheet advance is postulated. This direction is consistent with some relevant other data from the Sudetes, indicating that the Odranian ice sheet advanced into the area of the Sudetes from the north, north-east and north-west.