Strike-slip movements in the Polish Lowlands

Abstract

Seismic and borehole data from the Zechstein-Mesozoic structural complex have been explored from the viewpoint of possible strike-slip motions in the platform cover of the Polish Lowlands. This is the only source of information since reliable seismic data are lacking from beneath the Zechstein. Many places have been found in the Zechstein-Mesozoic complex where the axes of non-salt and salt anticlines are shifted in a left-lateral sense and NW-SE direction by a distance of a few kilometres (Figs. 1 and 2). Greater displacement of a group of anticlines has been noted at the boundary between the Pomeranian and Kujavian segments of the Mid-Polish Trough (MPT) which is coincident with a bend of the Mid-Polish Swell (MPS - see Figs. 1 and 3). However, because of lack of free space for accomodation of strike-slip movements in the syn-Alpine epoch, it is concluded that these displacements are apparent and that they were inherited after the earlier, syn-Variscan system. The latter was composed of a set of conjugate faults: major, right-lateral, trending NW-SE and minor, left-lateral, trending NE-SW. This system has been intermittently rejuvenated during the Permian-Mesozoic basin evolution (Figs. 4 and 7) and during its syn-Alpine inversion, mainly in a dip-slip sense, in a regime of vertical movements.