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.