Interaction between deformation and sedimentation in a multidecollement thrust zone: Analogue modelling and application to the Sub-Andean thrust belt of Bolivia

Abstract : Fold and thrust belts are influenced by the presence of decollement levels, as well as the amount of shortening and synkinematic sedimentation. These parameters are studied at the scale of a thrust belt using a field approach, combined with analogue and numerical modelling. In this study, we use analogue modelling to test the evolution of a single structure during sedimentation in a domain containing three prekinematic decollement levels. The development of this structure in the analogue experiments shows that the expression of the deformation is strongly dependent on sedimentation rate: (i) the structure propagates forward in an overall asymmetric shape if the sedimentation rate is slower than the uplift velocity, or (ii) the structure grows vertically and its vergence changes at the surface if the sedimentation rate is similar to the uplift velocity, or (iii) the structure grows vertically with a double vergence at the surface and at depth if the sedimentation rate is higher than the uplift velocity. The results of the experiments are compared with structures in the Subandean thrust belt to aid the interpretation of poor seismic data.