Sedimentary basin destruction inferred from the evolution of drainage systems in the Betic Cordillera, southern Spain

Abstract

The Guadix continental basin developed during the uppermost Miocene, the Pliocene and the Pleistocene. One axial fluvial system and two transverse systems are interpreted in its alluvial infill. In addition there are areas of lacustrine sedimentation, permanent in the eastern sector and ephemeral in the western part of the basin. From a sedimentological point of view, the Holocene drainage network shows significant similarities with that which occupied the ancient basin, although there are some differences in location. These provide information about the processes involved in the transformation of the sedimentary basin into an erosional basin with external drainage. Most of the data seem to indicate that the capture of drainage from the Guadix Basin by the Guadalquivir River was accelerated principally by tectonic processes related to a recent uplift of a sector of the Betic Cordillera, together with the disappearance of subsident points of the Basin. The high rate of Holocene erosion is partially conditioned by the type of sediment deposited in the basin (a low degree of lithification, textural heterogeneity, etc.) in comparison with the basement, and mainly by the position of the ancient basin in relation to the new relative base level, located almost 500 m lower than the position actually occupied by the Pleistocene relative base level of the basin.