Observations on Debris in the Basal Transport Zone of Mýrdalsjökull, Iceland

Abstract

Mýrdalsjökull is a temperate ice cap with an area of 596 km 2 , covering the volcanic Katlamassif in southern Iceland. Since 1900, extensive areas of ground moraine have been exposed during glacier retreat along the northern margin of the ice cap. The ground moraine surface is characteristically covered by a coarse layer of rock particles 10 to 150 mm in size. At the present glacier front, particles of corresponding size can be seen melting out from the lowermost glacier ice. Samples of ice and debris were collected from the basal transport zone. here generally 20 to 50 mm thick. and the volume, grain size, shape, and surface texture were determined. The orientation of rock particles in the englacial position. in the basal transport zone, and in the under lying lodgement till were analysed. The rock particles that dominate the debris content in the basal transport zone and constitute the coarse surface layer beyond the glacier margin are interpreted as a residual, which has escaped subglacial frictional deposition.