Glaciotectonic deformation within a flute from the Isfallsglaciären, Sweden

Abstract

The internal structure of a glacial flute in an area of fluted moraine outside the glacier Isfallsglaciaren in the Kebnekaise massif, Lapland, northern Sweden, has been observed along a series of sections. The till in the flute is underlain by glaciofluvial or glaciolacustrine sediment that has been subject to extensive glaciotectonic deformation. The flute-forming process is discussed and it is suggested that the flute was initiated beneath the warm-based part of the glacier, by the sediment moving into the low pressure area in the lee side of a clast, associated with a deforming bed. It is suggested that deformation increased both down the lee and outwards from the centre line. These results were compared with fabric data from two other flute sites from Norway where similar deformation patterns were observed. It is suggested that because the deformation pattern in the flutes formed beneath both cold toe and warm based glaciers are similar, then the warm based deforming bed model is valid for both, followed by either passive freezing by the frozen toe moving over them or active freezing by the release of pressure from the surrounding ice, causing the water-saturated till in the cavity to refreeze to the basal ice.