Reorganización de las zonas internas del tercio occidental de las Cordilleras Béticas: criterios e implicaciones tectónicas

Résumé

In this work, we discuss the main tectonic division of the western part of the Internal Zones of the Betic Cordilleras. Classically, the Internal Zones have been differentiated in three main complexes: the NevadoFilabride, Alpujarride and Malaguide, in ascending order. A review of recent publications about this subject shows that the distinction of these groups has been based upon inappropriate criteria and the results of its application have not been questioned yet. We consider that for a major tectonic division to be valid, the boundaries of the main complexes have to be located along lithospheric suture zones. The Internal Zones of the Betic Cordilleras preserve two suture zones, one in the Nevado-Filabride Complex and another in the socalled Western Alpujarrides. This second suture zone is defined by the Ronda peridotites in association with the eclogites of the underlying Ojen nappe. The application of this new approach changes the classical division in the Internal Zones. In the Western Alpujarride, the tectonic suture separates two domains: 1) the Los Reales nappe (including the Ronda peridotite massifs) and the Malaguide Complex in the hangingwall and 2) the materials that form underlying alpujarride units as Ojen, Guadaiza, and Yunquera in the footwall rock. This new division is supported by other geological evidence, as the intrusion in the Los Reales nappe and the Malaguide Complex of a dolerite dyke swarm about 25 Ma ago, which does not exist in the infrasuture nappes. Geological and palaeomagnetic data allow to relate the supra-suture block to the African border during a Mesozoic rifting event related to the oppening of the Neotethys and the lower block to a more septentrional domain, that was subducted during the Miocene.