Quantification of late Cenozoic erosion in Denmark based on sonic data and basin modelling

Abstract

The amount of section missing because of late Cenozoic erosion is estimated using basin modelling and sonic data from four stratigraphic levels in 68 Danish wells, and is found to be smaller than estimated in previous studies. The missing section increases from zero in the western and southern part of the Danish North Sea to 1000–1200 m towards north-east, on and along the Skagerrak-Kattegat Platform. In a broad intermediate zone, c. 500 m of mainly Paleocene–Miocene sediments are missing where Paleocene sediments subcrop the Quaternary. On the Skagerrak-Kattegat Platform, an additional c. 500 m Upper Cretaceous–Danian Chalk Group were removed where the lower parts of the Chalk are preserved, whereas the missing sediments must have been progressively younger towards south-west where Miocene sediments subcrop the Quaternary. The deep erosion on and along the Skagerrak-Kattegat Platform documents that Neogene uplift and erosion affected the study area prior to glacial erosion during the Quaternary. These results are consistent with Neogene uplift of south Norway as well as of south Sweden centred around the South Swedish Dome that culminates north-east of the Kattegat. There is good correlation between estimates of erosion based on Chalk velocities and on basin modelling. Comparison of different methods indicates that erosion is overestimated when based on sonic data from Lower Jurassic shale in north-eastern Denmark, and this could be due to lithological differences. It is concluded that maximum burial of the Mesozoic succession occurred prior to Neogene erosion throughout the area, and a previous suggestion of deep erosion in the Sorgenfrei-Tornquist Zone during the Late Cretaceous-Paleogene inversion is rejected.