TECTONIC EVOLUTION OF THE MID-POLISH TROUGH - MODELING IMPLICATIONS AND SIGNIFICANCE FOR CENTRAL-EUROPEAN GEOLOGY

The Polish Basin forms the easternmost part of the Permian-Mesozoic no rthwest European basin. The depocentral axis of the Polish Basin, the Mid-Polish Trough (MPT), is superimposed on the boundary between the w est European Phanerozoic and east European Proterozoic crustal domains , within the Trans-European Suture Zone. The presence of this fundamen tal crustal boundary may be paramount in structurally controlling the position of the MPT, concentrating stresses during post-Variscan wrenc h and extensional tectonics in central Europe. Tectonic subsidence ana lysis of the preserved and reconstructed stratigraphic record of the P olish 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-Kimmeri dgian (similar to 157-152 Ma) and beginning in the Cenomanian (similar to 97 Ma). The Oxfordian-Kimmeridgian episode is interpreted as corre sponding to a second extensional event, which correlated with intensif ied 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 Paleo cene. Forward modelling results, in view of existing geophysical inter pretations which show the presence of a deep Moho and a very high seis mic velocity lower crustal layer beneath the MPT, suggest that Permo-M esozoic basin development may be related at least in part to the intru sion of mantle material into and densification of the lower crust rath er than exclusively to crustal extension and thinning.