Cenozoic landscape evolution of the Lambert basin, East Antarctica: the relative role of rivers and ice sheets

摘要

The inception of the Antarctic Ice Sheet at around 34 Ma followed a period of globally warm climatic conditions. The efficacy of glacial erosion since this time is modelled using BEDMAP Antarctic digital elevation data and seismically estimated offshore sediment volumes to derive a DEM of the preglacial topography. Using a GIS, sediment is 'virtually backstacked" on to the present-day topography under dynamic ice sheet conditions to produce a model of the preglacial landscape of the Lambert basin area in East Antarctica. Survival of a preglacial river valley system under the ice suggests that glacial modification of the Lambert region has been modest. The Lambert Graben has focussed erosion for the last 118 million years. Morphometric analysis of the modelled preglacial and present-day subglacial topographies shows parallels with present-day drainage systems in Africa and Australia. We calculate that average rates of glacial and fluvial erosion for the last 118 million years have been similar and are ca. 1-2 m Myr~(-1) and ca. 0.89-1.79 m Myr~(-1) respectively.