Differential loading by prograding sedimentary wedges on continental margins: An arch‐forming mechanism

Rapid deposition of prograding sedimentary wedges on continental margins will cause excess pore pressure, fluid flow, and compaction as they load the substratum. They may also cause faulting and structural deformation in the sedimentary succession below and in front of the load. Large depositional units are in addition associated with pronounced isostatic subsidence. The magnitude and effects each component has on the basin as a whole is often debated. To address this problem, we use a quantitative approach with a coupled hydromechanical mathematical model based on linear isotropic elasticity. The equations are solved by the finite element method (FEM). In the modeling, a wedge‐shaped load emplaced successively over a period of 1.5 Myr is used to simulate the progradation of a thick sedimentary wedge. Results show that the differential load generates excess pressure below the prograding depocenter with lateral fluid flow in front and a tail of draining pore pressure behind. The sediments are pushed downward and laterally in front of the wedge and vertical and horizontal compressional and shear stresses are generated below the wedge. The formation of the Helland Hansen Arch, located in the Vøring Basin off mid‐Norway, is genetically associated with differential loading. Our results indicate that the whole eastern flank of the arch is a result of differential loading, whereas the western flank is mainly related to thermal subsidence since Paleogene times. Thus, alternative explanations like intraplate stress seem to be irrelevant as a genetic mechanism.