Un karst sous la glace de l'Antarctide ?

Abstract

A new bedrock map of the Dome C area based on all radar data collected during Italian Antarctic Expeditions in 1995, 1997, 1999 and 2001 is presented. The map can clearly distinguish the Dome C plateau, along with some valleys and ridges develop. The plateau develops at three different altimetric levels and its morphology is characterized by hills and closed depressions. There are no visible features which can be ascribed to glacial erosion or deposition. The major valley is 15km wide and 500m deep; its axis is parallel to that of other valleys and ridges in the plateau. The valley bottom is not flat, but contains a saddle in its centre. The morphology of the major valley could be considered as a relict one which was not modified by the overlying ice cap. Two big ridges, characterized by hills, saddles and depressions, lie near the boundaries of the area. The hill and depression landscape may be the results of two different processes the weathering of granitic rocks, with the development of a "Wemi-oranges" and inselberg landscape, or the karstification of limestones, and development of a cone karst. The karstic hypothesis should be the more suitable, but it is impossible to exclude the granitic rock weathering. Both proposed genetic hypotheses call for a warm humide climate and a long period of stability in a continental environment. Consequently, the ice cap did not largely modified the landscape.