GEOLOGIC EVOLUTION OF THE BETIC CORDILLERAS IN THE WESTERN MEDITERRANEAN, MIOCENE TO THE PRESENT

The Betic Cordilleras were formed during the Eo-, Meso- and Neo-Alpine evolution of the Western Mediterranean area. During the Neo-Alpine stage the northward subduction of the African plate took place and the Algerian-ProvenÇal Basin opened, with the creation of oceanic floor. Associated space problems produced the expulsion and extensive stretching of the Internal Zones to the west, which in turn disrupted and deformed the External Zones of the Betic and Rif Cordilleras. These occurrences essentially took place in the Burdigalian, and continued with diminished intensity into the Middle Miocene. Following the suturing of the transcurrent contact between the Internal and External Zones, important N60°-90° E and NW-SE faults occurred. The Betic Cordilleras are characterized as having been deformed by regional horizontal shortening (compression) oriented WNW-ESE or NW-SE, which gradually rotated to the NNW-SSE in the Late Miocene, when its most important intramontane Neogene basins were formed. The Alboran Basin, with a thinned continental crust, was formed as a western prolongation of the opening of the Algerian-Provençal Basin, with its basic features already apparent in the Burdigalian. The volcanism present in the southeast of the Betic Cordilleras and in northeast Morocco, crossing the Alboran Basin, is mainly Late Miocene in age. It is linked to fracturing and exhibits chemistry related to the different thickness of the crust. © 1990.