Buckling of orogens: Insights from analogue modelling

Abstract

Three-dimensional analogue models are employed to investigate whether oroclines may develop by horizontal buckling. A first series of experiments demonstrates that a crustal ribbon carried by a subducting plate cannot buckle and detach from its mantle root because it weakens and deforms when entering the subduction zone, such that little compressive stress is transferred through the ribbon. A second series of experiments shows that the aspect ratio of the ribbon impacts the wavelength of buckling and that the experimental tank employed is too small (maximum equivalent length is < 1500 km) to generate multiple buckles. Finally, a third series of experiments shows that if the plate boundaries surrounding the ribbon resist its horizontal lateral motion, thrusts or strike-slip fault systems may be generated in the ribbon thereby preventing buckling. We conclude that oroclinal buckling is favoured when a crustal ribbon is pulled by subduction, causing backarc extension. Hence, buckling and bending models for orocline formation are not mutually exclusive but reinforce each other.