The most recent data on stratigraphy and lithofacies analyses of Paleozoic strata of SW Poland as well as of the adjoining areas have been taken into account in order to introduce a hypothesis stating that the Barrundian (Prague basin) succession constitutes sedimentary infill of a marginal sea separated by an island arc from the open ocean. At present the remnants of this arc can be traced along the zone of Paleozoic inliers extending from the Kłodzko metamorphic terrain on the east up to the Karkonosze-Lusatia block on the west, while the fragments of Paleozoic oceanic crust occur in the Góry Kaczawskie and Góry Bardzkie Mts and also in the northern part of the Fore-Sudetic block. It is suggested here that the oceanic crust together with the overlying Góry Sowie Mts gneiss unit might have been accreted to the continental crust of the Bohemian massif along an oblique strike-slip zone during the Middle to Late Devonian times. Significant strike-slip displacements took also place there during the Tournaisian and Namurian A.
