Quaternary evolution of the Fennoscandian Ice Sheet from 3D seismic data

The Quaternary seismic stratigraphy and architecture of the mid-Norwegian continental shelf and slope are investigated using extensive grids of marine 2D and 3D seismic reflection data that cover more than 100,000 km2 of the continental margin. At least 26 distinct regional palaeo-surfaces have been interpreted within the stratigraphy of the Quaternary Naust Formation on the mid-Norwegian margin. Multiple assemblages of buried glacigenic landforms are preserved within the Naust Formation across most of the study area, facilitating detailed palaeo-glaciological reconstructions. We document a marine-terminating, calving Fennoscandian Ice Sheet (FIS) margin present periodically on the Norwegian shelf since at least the beginning of the Quaternary. Elongate, streamlined landforms interpreted as mega-scale glacial lineations (MSGLs) have been found within the upper part of the Naust sequence N ( 1.9-1.6 Ma), sugesting the development of fast-flowing ice streams since that time. Shifts in the location of depocentres and direction of features indicative of fast ice-flow suggest that several reorganisations in the FIS drainage have occurred since 1.5 Ma. Subglacial landforms reveal a complex and dynamic ice sheet, with converging palaeo-ice streams and several flow-switching events that may reflect major changes in topography and internal ice-sheet structure. Lack of subglacial meltwater channels suggests a largely distributed, low-volume meltwater system that drained the FIS through permeable subglacial till without leaving much erosional evidence. This regional palaeo-environmental examination of the FIS provides a useful framework for ice-sheet modelling and shows that fragmentary preservation of buried surfaces and variability of ice-sheet dynamics should be taken into account when reconstructing glacial history from spatially limited datasets.