Late Cretaceous–Cenozoic evolution of the North German Basin—results from 3-D geodynamic modelling

Abstract

The Late Cretaceous–Cenozoic evolution of the North German Basin has been investigated by 3-D thermomechanical finite element modelling. The model solves the equations of motion of an elasto-visco-plastic continuum representing the continental lithosphere. It includes the variations of stress in time and space, the thermal evolution, surface processes and variations in global sea level. The North German Basin became inverted in the Late Cretaceous–Early Cenozoic. The inversion was most intense in the southern part of the basin, i.e. in the Lower Saxony Basin, the Flechtingen High and the Harz. The lower crustal properties vary across the North German Basin. North of the Elbe Line, the lower crust is dense and has high seismic velocity compared to the lower crust south of the Elbe Line. The lower crust with high density and high velocity is assumed to be strong. Lateral variations in lithospheric strength also arise from lateral variations in Moho depth. In areas where the Moho is deep, the upper mantle is warm and the lithosphere is thereby relatively weak. Compression of the lithosphere causes shortening, thickening and surface uplift of relatively weak areas. Tectonic inversion occurs as zones of preexisting weakness are shortened and thickened in compression. Contemporaneously, the margins of the weak zone subside. Cenozoic subsidence of the northern part of the North German Basin is explained as a combination of thermal subsidence and a small amount of deformation and surface uplift during compression of the stronger crust in the north. The modelled deformation patterns and resulting sediment isopachs correlate with observations from the area. This verifies the usefulness and importance of thermomechanical models in the investigation of intraplate sedimentary basin formation.