Morphostructural patterns and landform generations in a glaciated passive margin: the Kobberminebugt-Qaqortoq region of South Greenland

摘要

On the west coast of South Greenland, the passive continental margin displays a left-lateral step which is not apparent on the east coast and coincides with a topographic change that marks the transition between Archaean basement rocks to the north and the Ketilidian orogenic belt to the south. Two issues are considered: (1) the origin of the regional topographic asymmetry between the mountains of southeast and southwest Greenland; (2) the origin of the Kobberminebugt-Qaqortoq lowlands (differential early Cenozoic tectonic movements and/or subsequent differential erosion in the uplifted landmass). By identifying and mapping stepped landforms, morphostructural patterns and weathering features, we discriminate between control by differential erosion and tectonic movements. We suggest that the stepped patterns sof erosion surfaces represent a pre-glacial landform evolution related to the uplift of two antiforms along the west and east coast of southern Greenland. In addition, late fault reactivation may have favoured the development of a low coastal surface in less uplifted blocks. A relative chronology of landform development in the study area is given. Although implying a strong involvement of differential erosion, our interpretation of the geomorphology is compatible with a late reactivation of an oblique transfer zone formed during the early Cenozoic rifting.