South-western boundary of the Mid-Polish Trough-new seismic data from the Oświno-Człopa Zone (NW Poland)

The Mid-Polish Swell (MPS), uplifted in the latest Cretaceous-earliest Tertiary at the site of the earlier Permian-Mesozoic Mid-Polish Trough (MPT), is adjoined to the south-west by a chain of salt diapirs which are probably underlain by a system of late Variscan deep faults in the pre-Zechstein basement. The Mesozoic reactivation of this system is responsible for the rapid thickness increase towards the axis of theMPT. Consequently, it may be regarded as the southwestern boundary of the MPT. During the phase of inversion, this system caused the mobilization of the Zechstein salt, the formation of the chain of diapirs and also (indirectly) the uplift of the regional unit of the MPS.