Controls on the location of compressional deformation on the NW European margin

The distribution of Cenozoic compressional structures along the NW European margin has been compared with maps of the thickness of the crystalline crust derived from a compilation of seismic refraction interpretations and gravity modelling, and with the distribution of high-velocity lower crust and/or partially serpentinized upper mantle detected by seismic experiments. Only a subset of the mapped compressional structures coincide with areas susceptible to lithospheric weakening as a result of crustal hyperextension and partial serpentinization of the upper mantle. Notably, partially serpentinized upper mantle is well documented beneath the central part of the southern Rockall Basin, but compressional features are sparse in that area. Where compressional structures have formed but the upper mantle is not serpentinized, simple rheological modelling suggests an alternative weakening mechanism involving ductile lower crust and lithospheric decoupling. The presence of pre-existing weak zones (associated with the properties of the gouge and overpressure in fault zones) and local stress magnitude and orientation are important contributing factors.