Characteristics of salt flow and syn-kinematic sedimentary structures in extensional basins / von Dipl.-Geol. Michael Warsitzka

Salt tectonics can significantly affect structure and depositional patterns of evaporite-bearing sedimentary basins, because rock salt deformation behaviour corresponds to that of a viscous fluid. Consequently, salt is able to flow according to an internal hydraulic-head gradient and produce local subsidence centres in regions of salt expulsion and topographic uplifts (e.g. salt diapirs, salt pillows) in regions of salt influx. In many world-wide salt-bearing sedimentary basins, e.g. the Southern Permian Basin in central Europe, a hydraulic-head gradient and consequent salt flow is induced by phases of regional tectonic extension. In such a tectonic setting, differential basement subsidence, e.g. due to normal faulting of sub-salt basement, may result in gravitationally driven flow towards the basin centre, and differential loading between basin lows and their flanks potentially squeezes salt away from imposed loads and causes upward directed salt flow. In order to investigate effects of syn- and post-extensional salt flow on structure and subsidence pattern of a basin, analogue experiments as well as analytical and numerical modelling are frequently applied. Existing analogue modelling studies dealing with processes of extensionally driven salt tectonics mostly examined brittle deformation and sedimentary structures in the supra-salt overburden, but rarely investigated flow pattern in the viscous substratum. Numerous analytical and numerical modelling studies, in contrast, addressed dynamics of flow in the salt, but only a few included sub-salt normal faulting as a trigger for salt flow. ...