A Model for the evolution of the Weald

Abstract

The Weald Basin developed through the Jurassic–Lower Cretaceous as an extensional basin founded upon E–W trending low-angle faults that were probably Variscan thrusts, subsequently reactivated as normal faults. Later, the basin was inverted and uplifted into a broad dome, whilst the London Basin to the north, and the Hampshire–Dieppe Basin to the south, subsided as flanking basins during the late Palaeocene–Eocene. Seismic sections across the Weald indicate that inversion resulted from north-directed stress. A stratigraphic reconstruction based on a N–S profile across the Weald and flanking basins serves as a template for a forward, 2D thermo-mechanical model that simulates the evolution of the Weald Basin through crustal extension and its inversion, and subsidence of the flanking basins, through compression. The model provides a physical explanation for this sequence of events, requiring a region of crust of reduced strength relative to its flanks. This weak region is the location of crustal-scale Variscan thrusts that have been reactivated subsequently. The strong crust on the flanks is essential for the development of flanking basins during inversion and uplift of the Weald.