Some key problems of the pre-Permian tectonics of Poland

Abstract

Four tectonostratigraphic terranes have been distinguished outside the edge of the East European Craton (EEC) in Poland (Fig. 1a) on a map by W. Pożaryski and P. Karnkowski (1992) and in W. Pożaryski et al. (1992). Two of them (Pomeranian and Łysogóry Terranes) are questioned by the present authors. These areas are rather parts of the EEC passive margin (miogeocline), deformed in Late Caledonian limes into a fold-and-thrust bell (Fig. 1b). The Małopolska Block and Upper Silesian Block are possible terranes, the former being of proximal character. It was detached from the EEC to the southeast of its present position, shifted northwestwards along a transform fault and re-accreted in the Late Caledonian epoch. The origin and tectonic nature of the Upper Silesian Block are disputable. Both terranes were covered by the Devonian-Carboniferous overlap sequence which was tectonically activated towards the end of the Variscan epoch. Apart from the terrane problem, the extent of the outer Variscan foldbelt and its internal structure are considered. It is most probably a Namurian-Westphalian fysch zone with local intramontane depressions. Its front lies approximately along the line: Gorzów-Poznań-Wieluń, thus lying farther to the south than the Variscan front proposed on the discussed map.