Subglacjalne pochodzenie przełomowych dolin zachodniej części progu środkowotriasowego i ciągu pagórów okolic Gogolina

The western part of the Middle Triassic Ridge is cut by two narrow gorges. At present the Odra River is running through the western gorge in the vicinity of Krapkowice and a small stream, right-bank tributary of this river, through the eastern one, passing 1–2 km to the east of the former. These erosive forms were hitherto interpreted as epigenetic gorges of the Odra. A row of elongated hills built of gravel and sands is found at southeasterly prologation of the eastern erosive gorge. The field study carried out at a site located at one of these hills indicates direct connections and subglacial origin of these erosive forms and hills. Most probably the eastern gorge represents a fragment of a subglacial tunnel valley, which continues northwards into the zone of the present-day Odra channel. The hills located at prolongation of the gorges are interpreted as eskers. Because of the high similarity, the western gorge valley is most probably also of subglacial origin. The studied part of the subglacial drainage system most probably originated in result of an outburst flood of subglacial water temporarily stored at the bottom of the ice-sheet. The tunnel valley and eskars were formed during Odranian glaciation.