Quantitative aspects of stratigraphic onshore-offshore relationships along the western margin of southern Norway: implications for Late Mesozoic and Cenozoic topographic evolution

One of the most debated topics in Norwegian geology relates to the long-term topographic evolution of the Norwegian margin and the link between onshore topography and offshore stratigraphy during the Phanerozoic. Different workers have attempted to address this topic quantitatively by relating calculated offshore sediment volumes to onshore sediment production rates and/or geomorphological observations at various spatial and temporal scales. Here, we review some of the recent advances with emphasis on the onshore-offshore coupling between landscapes and stratigraphy. We find that the different methods are associated with various strengths, weaknesses and fundamental assumptions that are hard to constrain with existing data. We also present new data from Eocene and Oligocene deep-water deposits that help to constrain the Palaeogene landscape topography along the western margin of southern Norway. We conclude that the great variability in sediment supply rates and stratigraphic organisation observed in the Jurassic to Palaeogene succession can best be explained by recurrent periods of tectonic reactivation of hinterland topography in the latest Jurassic, earliest Palaeocene and earliest Oligocene. Although relatively short-lived periods of climate deterioration also influenced sediment production and transport during these time periods, we suggest that first-order fluctuations in sediment flux can best be explained by long-term tectonic rejuvenation of the onshore topography.