The long-term geomorphic evolution of shield surfaces is poorly understood, especially of glaciated shields where saprolites and correlative sediments have been removed by glacial erosion. We know the rough picture of land uplift and erosional unloading during the Cenozoic and we know of the existence of stepped surfaces on the shield. However for further studies of the long term geomorphology of glaciated shields, we first need to assess the patterns and depth of glacial erosion on the shield bedrock landforms in order to reconstruct the preglacial land surface.
Large scale topography controls ice inception on that surface and influences ice dynamics during glaciation. Large-scale relief is a trigger for selective erosion and for ice streaming and bed materials affect the ice flow and the composition of tills. Yet the quantitative impact of glacial erosion on shield bedrock is barely known.
The patterns of erosion, deposition and redistribution of loose material on the shield surface are well known. The interesting question is if the bedrock surface of the northern shields only was the surface for redistribution, largely unaffected, or if the surface itself was modified and to what degree?
A detailed and convincing quantification of removal of bedrock by ice does not exist. Studies show that the ice erosional impact can be modest. However these are results of regional studies and wider studies of the northern shields are desirable, with the final aim of a quantification of the glacial erosional removal of bedrock for entire cratons.
Field investigations on the basis of identification of promising field localities in a digital elevation model (DEM), and in combination of GIS-analysis of combinations of the DEM with databases of bedrock geology and tectonics, are a new and powerful tool to identify patterns of glacial erosion over large areas and eventually to quantify the depths of glacial erosion on glaciated shield surfaces.
The presentation will show current results for northern Fennoscandia and future possibilities to assess patterns and quantities of glacial erosion in glaciated shield areas, with a focus on DEM-analysis.