Linking offshore stratigraphy to onshore paleotopography: The Late Jurassic-Paleocene evolution of the south Norwegian margin
The temporal link between onshore topography and offshore stratigraphy is of key importance for understanding the long-term development of continental margins. The Mesozoic and Cenozoic landscape topography of southern Norway has long been a matter of debate due to the absence of concrete data reflecting ancient onshore relief. We here present quantitative estimates of paleotopography in southern Norway during three key time intervals (Late Jurassic, Late Cretaceous, and Paleocene) based on the observed volume of sediment stored in point-sourced depocenters along the margin. The aim is to determine the syndepositional paleolandscapes that are in best agreement with the observed distribution, geometry, lithology, and volume of different offshore depositional units. Probability ranges of estimated paleorelief are based on Monte Carlo simulations of a relief prediction model. The results suggest that the late Phanerozoic sedimentary successions along the margin best reflect: (1) a Late Jurassic landscape with a maximum relief of ∼1.6 km; (2) a more subdued Late Cretaceous topography of <0.5 km in the south and up to ∼0.5 km in the north; and (3) a Paleocene topography of up to ∼1.1 km in the north and ∼0.5 km in the south. The temporal and spatial variability in offshore deposition and the linked onshore topography strongly suggest that relief must have been rejuvenated several times during the late Phanerozoic in response to tectonic activity along major fault systems. This quantitative assessment not only sheds new light on the topographic evolution of the south Norwegian margin, it also provides a potential tool with which to investigate the topographic evolution of continental margins and the close coupling between onshore relief and offshore stratigraphy in nearby sedimentary basins.