Geology and tectonics of the Betic Zone, SE Spain

Abstract

The southern margin of the Iberian continent comprises a complex geological history, which can be traced back into the Proterozoic when a gneissic basement was formed. A cover of Nevado-Filabride rocks was deposited onto this Proterozoic basement during the Palaeozoic. The Permian intrusion of the Bédar granite suggests that the Palaeozoic sedimentary rocks now exposed in the Betic Cordilleras have been affected by the Hercynian orogeny, similar to that of Palaeozoic rocks in the adjoining Ossa Morena zone. The Hercynian basement was probably covered by Alpujarride carbonates in the Mesozoic, when rifting opened Tethys and intruded 140 Ma old basic dyke swarms. The Palaeozoic basement of the Betic Cordilleras comprises a suture of Late Cretaceous subduction (80–85 Ma B.P.). This can be inferred from (HP,LT)-metamorphic facies obducted in coeval thrust slices of Nevado-Filabride rocks. The Nevado-Filabride nappes include Mesozoic carbonates transformed into marbles (Macael). The suture was probably annnealed after the closure of Tethys. The Mesozoic boundary between Africa and Europe and the rifting in Tethys ceased during the Palaeogene when the Atlas Mountains were formed (36 Ma B.P.). Subsequently, relative movements between Africa and Europe in the Neogene were accommodated by strike-slip faults. These define the Iberian microplate moving eastward by Atlantic spreading and possibly subducting under Italy. Neogene deformation of Iberia is most intensive in southeastern Spain due to emplacement of a mantle diapir under the Alboran area. This occurred early in the Neogene (Aquitanian) and caused nappe spreading involving Alpujarride and Malaguide rocks. The subsequent Neogene history has now been studied in great detail and is reviewed here. It involves clear examples of calc-alkaline volcanism — most probably not related to subduction, seismic motion along strike-slip faults within the Iberian microplate, and syntectonic deposition in intermontane Neogene basins.