CONVERGENCE RATE-DEPENDENT GROWTH OF EXPERIMENTAL VISCOUS OROGENIC WEDGES

Abstract

The effects of convergence rate variations on the evolution of mature orogenic wedges are investigated using temperature-dependent variations in the viscosity of paraffin as an analogue for the natural strength distribution in the crust. Experiments were performed in a thermomechanical shortening apparatus for strain rates ranging between 10-5 and 5x10-5 s-1. Experimental wedges accreted at fast convergence rates show steep surface tapers and narrow deformed areas, whereas at low strain rates they show lower taper topographies and wider deformed areas during self-similar growth. A decrease in convergence rate during deformation corresponds to a change from localised to delocalised deformation in concomitance with the outward migration of the deformation front. The model results provide insights into deformation partitioning, geometry and accretionary mechanisms within orogenic wedges.