Tectonic units from the Sierra Espuña - Mula area (SE Spain): implication on the triassic paleogeography and the geodynamic evolution for the Betic-Rif Internal Zone

Abstract

Tectonic units of the Sierra Espuña-Mula area are described in order to characterize the palaeogeographic passage from the Alpujarride to the Malaguide Complexes through the “intermediate units”. Moreover, the Meso-Cenozoic cover of the Malaguide units in this area show the transition from the Malaguide to the “Internal Dorsal”. Both features are relevant for the palaeogeographic reconstruction and geodynamic evolution of the Betic-Rif Internal Zone (BRIZ) in the framework of the Alpine Perimediterranean Chains. These data, together with others from other sectors of the Betic-Rif Cordillera enable us to propose a palaeogeography during the Triassic rifting with two subsident areas related to two oceanic branches (the Nevadofilabride-Alpujarride to the north, and the Maghrebian, to the south) separated by a continent or shallow marine area (the Malaguide). These branches were closed during post-rifting geodynamic evolution including two different piling phases: a first top-to-the-north in the northern branch (Alpine tectogenesis, Latest Cretaceous-Middle Oligocene); a second top-to-the-south in the southern branch (Maghrebian tectogenesis, Late Oligocene-Early Miocene). The opposite arrangement of units in the Betic with respect to the Rif required clockwise rotations to form the Gibraltar Arc, confirmed by data from the literature. These rotations are related to the westward displacement and subsequent collision of the BRIZ against the African and Iberian palaeomargins.