Effect of fluid pressure distribution on the structural evolution of accretionary wedges

Abstract

Numerical experiments on evolving accretionary wedges usually implement predefined weak basal décollements and constant strength parameters for overlying compressed sequences, although fluid pressure ratio, and therefore brittle strength, can vary strongly in sedimentary basins. A two-dimensional finite difference model with a visco-elasto-plastic rheology is used to investigate the influence of different simplified fluid pressure ratio distributions on the structural evolution of accretionary wedge systems. Results show that a linear increase in fluid pressure ratio towards the base leads to toeward-verging thrust sheets and underplating of strata, while simulations with a predefined décollement form conjugate shear zones supporting box-fold-type frontal accretion. Surface tapers are in agreement with the critical wedge theory, which here is modified for cases of varying fluid pressure ratio. Furthermore, the numerical results resemble findings from natural examples of accretionary wedges. © 2017 John Wiley & Sons Ltd.