Mechanical stratigraphy and the transition from trishear to kink-band fault-propagation fold forms above blind basement thrust faults: A discrete-element study

We employ a discrete-element technique to investigate the influence of mechanical stratigraphy on the transition from trishear to kink-band fault-propagation fold forms above a blind basement thrust fault. We find that a 'classic' trishear fold, consisting of a broad, upwards-widening monocline with limb dips increasing towards the fault tip, occurs where the cover stratigraphy is weak and has no strong mechanical layering. In contrast, we find that marked, bedding-parallel mechanical layering in the cover promotes much narrower, kink-like fold geometries with more constant limb widths and dips. We discuss the modelling results in terms of their implications for structural interpretation and the application of kinematic models of fault-related folding in contractional settings.