Physical models of thrust wedges

Abstract

Scaled sandbox models have been used to simulate the growth and sequential development of critical thrust wedges in isotropic cohesionless and anisotropic cohesionless materials. Variations in the initial thickness of the layered sequence, the friction of the basal detachment, and the anisotropy of the layered system have been systematically investigated. Imbricate fans of dominantly foreland-vergent thrust systems are developed similar to those found in accretionary prisms and in foreland fold and thrust belts. Critical taper wedges close to theoretically predicted geometries are developed for intermediate values of basal friction (µb = 0.47 whereas for the lower value of basal friction low-taper wedges are formed with tapers less than predicted by theory. Supra-critical wedges are formed when the basal friction equals or is greater than the coefficient of friction in the wedge and the wedge has a high taper closer to the angle of rest for the modelling material. The spacing/thickness ratio of foreland-vergent thrusts increases as the layer thickness increases. The spacing of thrust faults increases with increased basal friction. Higher basal friction or anisotropy within the layered systems favours displacement along foreland-vergent thrusts and suppresses backthrusts.