Lower Paleozoic low-grade metamorphic units from the Central Balkan Zone, Bulgaria: tectonic relationships, framework and geodynamic significance

The Central Balkan Zone belongs to the north-vergent fold-and-thrust belt of Alpine orogen. In this zone, pre-Permian low-grade rocks, metamorphosed during Variscan orogeny, were later reworked at two main stages compressional tectonics. Several tectono-stratigraphic subdivisions these metamorphic rocks previously presented, based on a purely stratigraphic approach in absence detailed structural studies and, most importantly, reliable paleontological and geochronological records. study, we propose new framework from Zone, applying critical analysis existing data combined with lithological observations. Based relationships constraints, several entities, such as Korduna, Bilo Zvezdets units, established together reassessment recognized Diabase-Phyllitoid Complex (DPC). Both DPC Unit are now defined Cambrian–Lower Ordovician (?) mélange complexes part an accretionary wedge and/or forearc basin formed along north Gondwanan margin. Bilo, Murgash Etropole mountains, tectonically uninterrupted Cambrian–Upper section, characterized by normal gradient nonmetamorphosed terrigenous is recognized. deposition sediments related subduction Prototethys early evolution Rheic Ocean. An inverted southern slopes Zlatitsa-Teteven mountains through Korduna units syn-metamorphic deformation Stargel-Bulovanya Tectonic Zone.