Analogue modelling of the inversion of multiple extensional basins in foreland fold-and-thrust belts

Abstract

Abstract. The presence of pre-existing rheological heterogeneities in the lithosphere plays a significant role during subsequent stages of deformation in essentially every geological process. Extensional basins located in foreland fold-and-thrust belts will alter the spatio-temporal evolution of its associated orogen. It remains unclear how far horizontal stresses can act and reactivate extensional structures due to their intrinsic irregular patterns of deformation deflection and localisation. Overprinting events and relative dating uncertainties in the geological record make it difficult to interpret how stresses were transferred across a heterogeneous crust. Here we examine the inversion of extensional basins in foreland fold-and-thrust belts by using three-dimensional analogue experiments that simulate first an extensional stage, followed by a shortening stage. Our results show how extensional basins proximal to the orogenic front effectively localise deformation in the shape of thrusts and prevent stress transfer beyond their location. Basins that are located at large distances from the orogenic front also show evidence of mild inversion at early stages but are characterised only by basin infill contraction and uplift. When multiple extensional basins are present, the degree and type of inversion will depend primarily on their relative location and distance to the orogenic front. Here we also prove that the presence of additional extensional features in the vicinity of a basin can be a first-order controlling factor in their overall reactivation history. We share additional insights of how a fold-and-thrust belt evolves once the extensional basins have been incorporated by the advancing wedge, and we provide comparisons with natural examples that shed light on some still unanswered questions related to the process of basin inversion in orogenic belts.