THE GLACIALLY SCULPTURED LANDSCAPE IN DRONNING-MAUD LAND, ANTARCTICA,FORMED BY WET-BASED MOUNTAIN-GLACIATION AND NOT BY THE PRESENT ICE-SHEET

The glacial landscape beneath the Maudheimvidda ice sheet in East Anta rctica was most probably formed during a more temperate phase of Antar ctic glaciation than the present. Overdeepened glacial cirques and U-s haped valleys are found in the Heimefrontfjella and Vestfjella mountai n ranges. These glacial landforms, located beneath the ice sheet, have been mapped with radio-echo sounders. The present ice sheet covering these landforms is cold and frozen to its bed, and has a negligible er osive effect on the substrate. Ice sheet thickening during the Quatern ary glacial periods is not believed to have caused any significant inc rease in erosion at the investigated sites. Instead, the glacial morph ology was most likely formed by smaller, temperate glaciers when the A ntarctic climate was warmer than at present. Datings of foraminifera a nd ash layers from the Transantarctic Mountains indicate that the pres ent cold ice sheet was formed 2.5 Ma years ago. Other studies imply th at a cold Antarctic ice sheet has lasted even longer. The glacial land forms in Maudheimvidda may thus be of a pre-Quaternary age.