Quantitative dynamic modelling of basin development in the central and eastern North Sea region – coaxial stretching and strain localization

Abstract

A new two-dimensional dynamic lithosphere model is used to simulate the Late Palaeozoic to end Danian evolution of the Norwegian-Danish Basin and the post Permian evolution of the Central North Sea including the Central Graben. The transient heat equation and the equations of motion are solved using the finite element method. The lithosphere deforms by brittle and ductile processes through an elasto-visco-plastic rheology depending on temperature, pressure, strain-rate and material parameters. Strain softening dependent on accumulated strain is incorporated. Deposition, erosion and compaction of sediments are simulated. Results show that it is possible to satisfy observations of crustal structure, sediment thickness and surface heat flow for both basins taking all major tectonic and thermal events into consideration. The evolution of the Norwegian-Danish Basin is modelled using a Late Carboniferous – Early Permian thermal event, main rift phase in Early Permian and a minor extensional phase in Triassic. For the Central North Sea two thermal and three tectonic events are simulated: Late Carboniferous – Early Permian and Middle Jurassic thermal events, Early Triassic and Late Jurassic extension, and Late Cretaceous compression. Results show that strain softening may lead to strain localization during extension and therefore may explain observations of upper mantle dipping reflectors in the North Sea. A pure shear dominated extensional regime may change into a simple shear system.