Interaction deformation/sedimentation in a multidecollement thrust analogue modelling. Application to Bolivian subandean
Abstract
Fold and thrust belts are influenced by the presence of décollement levels, the amount of shortening, and the amount of synkinematic sedimentation. These parameters have been studied at thrust belt scale in field approach, analogue and numerical modelling. The effect of synkinematic sedimentation with one décollement level has been studied at the scale of a single structure, and only one study has addressed the effect of synkinematic sedimentation with two décollement levels. Here we used analogue modelling to test the evolution of a single structure during sedimentation in a domain presenting two prekinematic décollement levels. The evolution of these experiments shows that the expression of the deformation is very dependent on the sedimentary ratio: (i) or the structure propagate frontward in asymmetric global shape if sedimentation ratio is lower than the uplift velocity, (ii) or the structure increase vertically and its vergence change with development in opposite sense if the sedimentation ratio is similar to the uplift velocity, (iii) or the structure is very symmetric in surface and at depth, with associated uplift if sedimentation ratio is higher than the uplift velocity. The results of the experiments were compared to the Subandean thrust belt in order to help seismic interpretation.