Relationships between strike-slip movement and fold trends in thin-skinned tectonics: Analogue models

Abstract

In thin-skinned tectonics, a sediment cover has been sheared off from an underlying basement. In many cases, such detachments are located in salt horizons. During deformation, faults and narrow anticlinal folds can develop in the cover. Analogue models show that fold axis patterns are related to the compression direction and to the position and shape of the faults. In each model, a multilayer made of paraffin wax and grease represents the cover sliding over a rigid basement made of plexiglass. In each of the three experiments a fault is cut before deformation. This fault may be located: (1) in the basement; (2) in the cover, with a limited length; or (3) in the cover, with an unlimited length. The fold axis patterns are very heterogeneous around a limited-length fault in the multilayer where the fold axes deviation can reach 90° around the fault tips. They are quite homogeneous around an unlimited-length fault, irrespective of its location. An unlimited-length fault mainly induces a slight deviation of the fold axes due to strike-slip movement. The detachment horizon reduces the transmission of stresses from the basement and in such cases, the final deformation is very sensitive to local heterogeneities inside the overriding multilayer.