Un olistostroma con cantos y bloques del Paleozoico Inferior en la cuenca carbonífera del Guadalmellato (Córdoba). Parte II: Bioestratigrafía y afinidades paleogeográficas

Resumo

The Mississippian (Serpukhovian) Guadalmellato olistrostrome, about 9 km northwest of Adamuz (province of Córdoba), includes abundant pebbles and cobbles bearing Lower Paleozoic fossils. They were deposited as debris-flows into slope facies and mixed there with olistoliths coming from local Visean limestones. The fossiliferous debris were deposited in an “inverted mountain” sequence, according to the progressive erosion of a Paleozoic basement lying below the eroded Visean platform. The studied fossils characterize at least 15 Ordovician, Silurian and Lower Devonian paleontological assemblages. The clastics were derived from an unknown source area adjacent to the Carboniferous Guadiato Basin. The paleobiogeographic affinities of these assemblages display a clear ‘Central-Iberian influx’ only during the Middle and Upper Ordovician, whereas the Lower Ordovician and Silurian fossils and biofacies belong to units with scarce to inconsistent correlation with coeval successions in either the Ossa-Morena Zone or the Central-Iberian Zone of the Iberian Massif. Careful review of the Paleozoic record for the entire Obejo-Valsequillo Domain, differentiated among the Los Pedroches Variscan batolith and the Ossa-Morena Zone, reveals that this domain is not a “southern allochtonous unit” defined as an extension of the Central-Iberian Zone. The tectonostratigraphic context of the Serpukhovian olistostrome of the Guadalmellato valley is similar to that of Devonian to Carboniferous Variscan syntectonic units known from localities in France, Germany and Great Britain. All of them include fossiliferous Ordovician to Devonian rocks, or pebbles from pre-Ordovician metamorphic units, whose peri-Gondwanan source areas are enigmatic or of rather problematic location.