Centrifuge modelling of thrust systems in the brittle crust: Role of frictional décollement geometry

Centrifuge analogue modelling has provided significant insights into the evolution and architecture of fold and thrust systems. However, all previous works focused on the deformation of viscous and/or plastic layers, and did not analyze the development of structures in the brittle crust. In this work, we present the results of analogue centrifuge models reproducing compression of purely brittle upper crustal layers. We run enhanced gravity models investigating the role exerted by frictional décollements on the evolution and architecture of thrusting and compared the results with new normal-gravity models with similar set-up. In line with the results of previous experimental works, our models show that the presence of a low-friction basal décollement significantly influences the evolution and pattern of thrust systems. By reducing the basal friction of the experimental wedge or the sector of the wedge where the low-friction décollement is located, this layer promotes experimental wedges with low tapers and low heights in the inner portion. Moreover, when a low-friction basal décollement occurs, the tectonic wedge is characterized by an increase in wavelength of thrust sheets toward the foreland, compared to the purely brittle models. Results show a good comparison between centrifuge and normal gravity models, indicating that the centrifuge technique can be successfully used to model shortening in the brittle crust and therefore to analyze the evolution and architecture of thrust systems.