A buried glaciofluvial channel in the Anděl Col, northern Bohemia :new evidence for the middle pleistocene ice sheets extent in Western Sudetes

Abstract

This study presents a new finding of glaciofluvial sediments filling a buried channel in the Andel Col (522 m a.s.l.) in the Jizera Mts., on the Czech-Polish border. At least 550 m long and 55-100 m wide channel filled by glaciofluvial sediments was determined by geophysical methods in the lowermost part of the col. The base of the channel was found at a depth of 14-19 m under the present ground surface, descending from east to west draining the ice sheet front in the same direction. The channel is incised in the bedrock representing thus a Nye channel and is filled by >13 m of glaciofluvial sand, gravel and mud, which is covered by 1-2 m thick colluvial deposits. The large part of the glaciofluvial package was deposited in subglacial environment reflecting the ice sheet decay events of higher release of the material from the ice sheet. The upper glaciofluvial part of sediments was deposited in front of the slowly decaying ice sheet front. No subglacial tills have been found in the col area, which is not unusual for such an exposed site. We reconstruct the maximum altitude limit of the ice sheet in the col as being at least at ~540 m and the ice thickness in the Andel Col being few tens of metres. The Andel Col is the highest known area in Northern Bohemia covered by an ice sheet and improves thus our knowledge about the maximum vertical extent of Middle Pleistocene ice sheets in Western Sudetes.