History of geological development of Northern Bulgaria during the Paleozoic

We describe the paleogeographic environment and conditions of sedimentation during the Devonian, Carboniferous, and Permian periods. Lithologic-facies maps, compiled for the first time, clarify features of the transgressive, stable, and regressive phases of the Paleozoic sedimentation cycle. On the basis of the tectonic regime, the regional structural plan, and the nature of the sedimentary associations, we recognize two stages in the Paleozoic history of development of Northern Bulgaria: Ordovician-Early Carboniferous and Late Carboniferous - Permian. We give distinguishing features of each stage and reach conclusions as to the inheritance of the principal structural elements of the platform type during the development.—Authors.