The mechanics of an accretionary wedge affected by a layer with varying rheology, viscosity, and thickness

Abstract

An accretionary wedge evolves wide extended, flat and with a characteristic thrust system, if the wedge décollement is located in a viscous evaporite. The deformation processes of such wedges are complex and until now not fully understood. Therefore, in this present work 2D numerical sandbox experiments are developed in which an incoming sediment sequence is accreted against a fixed vertical wall due to a moving box bottom. The experiments contain a brittle incoming sequence in which either a brittle Mohr Coulomb layer or a viscoelastic-plastic layer (Burger s rheology) is embedded. The first study focuses on the differences which occur in the mechanics of two wedge experiments if either a weak viscoelastic-plastic or a low-friction brittle layer is embedded between two high friction brittle layers. To find out the viscosity under which the wedge deforms most likely as it would grow on top of an evaporite, the second study analyzes the effects of different viscous materials on wedge mechanics. Finally, the calibrated model is used to study the effects of different incoming sediment thicknesses on the accretion process.