Notes on Neogene basin history of the Western Alboran Sea and its implications for the tectonic evolution of the Rif-Betic orogenic belt

Abstract

Several recent tectonic models for the Alpine deformation in the Rif-Betic Cordillera have proposed some form of uplift of the hiterland of the thrust belt (presently the Alboran Sea), which as it collapsed and extended, drove thrusting in the more external zones. This thrusting episode occurred predominantly during the Middle and Upper Miocene; consequently if the tectonic model is correct, nasin fill of the same age underlying the Alboran Sea should be extensively affected by large scale extensional features. This is not the case in the Western Alboran Basin where seismic reflection and well data indicate that little if any Upper Miocene extension has occurred, and deformation of the Miocene section is predominantly by shale diapirism. Although the crust under the Alboran sea is thinned the timing of the thinning is unknown. It may either be attributed to a pre-Miocene extensional phase, or to delamination of the lower crust perhaps caused by subduction during the Oligocene.