Differential vertical movements in the eastern North Sea area from 3-D thermo-mechanical finite elemental modelling

Abstract

The response of a heterogeneous lithosphere to a compressional stress field is studied using a three-dimensional thermo-mechanical finite element model. Weak zones in the lithosphere thicken and act as loads that pull down the lithosphere in regions around the weak zones. Strong zones are subjected to less lithospheric thickening than the surroundings and produce surface depressions and uplift in the surrounding areas. The model is used to study the Late Cretaceous and Paleocene differential vertical movements in the eastern North Sea area. The Sorgenfrei-Tornquist Zone is assumed to be a pre-existing weak crustal zone, which inverts during compression and produces marginal basins by loading the lithosphere. The area of the Silkeborg Gravity High is an example of a pre-existing strong crustal zone which subsides during compression. Moho topography in the area gives rise to lateral strength variations, which result in surface uplift where Moho is deep and subsidence where Moho is shallow. These effects, together with the lateral variations of the thermal structure and the stress field, determine the overall Late Cretaceous-Paleocene distribution of vertical movements of the area. This has implications for the pattern of erosion, sediment transport and the distribution of sediment facies.