Tectonic evolution of the Mid-Polish Trough: Modelling implications and significance for central European geology

The Polish Basin forms the easternmost part of the Permian-Mesozoic northwest European basin. The depocentral axis of the Polish Basin, the Mid-Polish Trough (MPT), is superimposed on the boundary between the west European Phanerozoic and east European Proterozoic crustal domains, within the Trans-European Suture Zone. The presence of this fundamental crustal boundary may be paramount in structurally controlling the position of the MPT, concentrating stresses during post-Variscan wrench and extensional tectonics in central Europe. Tectonic subsidence analysis of the preserved and reconstructed stratigraphic record of the Polish Basin indicates the occurrence of an initial Late Permian-Early Triassic (255-241 Ma) 'rifting' phase that was followed by subsequent episodes of increased tectonic subsidence during the Oxfordian-Kimmeridgian (similar to 157-152 Ma) and beginning in the Cenomanian (similar to 97 Ma). The Oxfordian-Kimmeridgian episode is interpreted as corresponding to a second extensional event, which correlated with intensified rifting and wrench activity within the Arctic-North Atlantic rift system and along the northern Tethyan margin, while the Cenomanian may be considered a precursor of compressional deformations in the basin which culminated in basin inversion in the latest Cretaceous and Paleocene. Forward modelling results, in view of existing geophysical interpretations which show the presence of a deep Moho and a very high seismic velocity lower crustal layer beneath the MPT, suggest that Permo-Mesozoic basin development may be related at least in part to the intrusion of mantle material into and densification of the lower crust rather than exclusively to crustal extension and thinning.