Convergence rate-dependent growth of experimental viscous orogenic wedges

The effects of convergence rate variations on the evolution of mature oroge nic wedges are investigated using temperature-dependent variations in the v iscosity of paraffin as an analogue for the natural strength distribution i n the crust. Experiments were performed in a thermomechanical shortening ap paratus for strain rates ranging between 10(-5) and 5 x 10(-5) s(-1). Exper imental wedges accreted at fast convergence rates show steep surface tapers and narrow deformed areas, whereas at low strain rates they show lower tap er topographies and wider deformed areas during selfsimilar growth. A decre ase in convergence rate during deformation corresponds to a change from loc alised to delocalised deformation in concomitance with the outward migratio n of the deformation front. The model results provide insights into deforma tion partitioning, geometry and accretionary mechanisms within orogenic wed ges. (C) 2000 Elsevier Science B,V. All rights reserved.