Bimodal Plio-Quaternary glacial erosion of fjords and low-relief surfaces in Scandinavia

International audienceGlacial landscapes are characterized by dramatic local relief, but they also commonly exhibit high-elevation, lowreliefsurfaces. These surfaces have been attributed to glacial headward erosion and periglacial processes in Alpinesettings. However, the timing and processes responsible for their formation in northern high-latitude regions remainelusive. Here, we infer the topographic evolution of western Scandinavia during the Plio-Quaternary glaciations(0-2.8 Ma) by linking onshore erosion to offshore sedimentation. We estimate the rate of fjord erosion from geophysicalrelief and compare that with the erosion reflected by offshore sedimentation. We find that the sedimentsgenerated by fjord erosion (65-100 103 km3) over the entire western Scandinavia during the Plio-Quaternaryglaciations accounts for only 35–55% of the equivalent bedrock erosion deduced from total sediment volume depositedoff the coast of Norway. This large mismatch implies that during this period, significant erosion (300-400m) must have also taken place away from the fjords at high elevation and thus indicates a bimodal distribution ofglacial erosion. Furthermore, comparing the distribution of the high-elevation, low-relief surfaces with estimatesof the long-term glacier equilibrium line altitude supports the idea that effective erosion in extensively glaciatedareas limits topographic height, a process known as the glacial buzzsaw. We therefore conclude that glacial andperiglacial processes have a substantial impact on the formation of low-relief surfaces observed in glaciated mountainbelts and high-latitude continental margins