Tectonic controls on the formation and evolution of internally drained systems in the western Betics fold-and-thrust belt (S Spain)

Abstract. We analyse the drainage network in a depressed area within the western Betics fold-and-thrust belt (southern Spain) to investigate the Atlantic-Mediterranean water divide evolution after the Messinian Salinity Crisis (last 5 My). To do that, we made a hydro – geomorphic evaluation of streams and endorheic basins together with a detailed field-based analyses of post-Serravallian structural features. Results from the analysis of stream profiles and the application of SLk and χ indexes showed that Mediterranean streams present a higher incision capacity than Atlantic streams, tributaries of the Guadalquivir river. Moreover, several rivers captures of Atlantic river watersheds and of endorheic basins have been described and quantified. Although the Atlantic-Mediterranean water divide will probably move NW-ward, endorheic basins will still endure, hosted in a depressed area located between two active transpressive zones (the Algonales-Badolatosa and Torcal shear zones). Our results confirm that active tectonics have reshaped the area more intensively than previously considered, and that this modification had significant hydrological implications.