Neotectonics and Plio-Quaternary landscape development within the eastern Huércal-Overa Basin (Betic Cordilleras, southeast Spain)

Abstract

The Huércal-Overa Basin is one of a series of Neogene sedimentary basins located within the Betic Cordillera of southeast Spain. Its geological and geomorphological history has been controlled by tectonic activity culminating in basin inversion during the Plio-Quaternary. Deformation of the Huercal-Overa Basin is associated with left-lateral strike-slip faulting in relation to its position within the Trans-Alboran shear zone. In this paper, we focus upon the eastern portion of the Huercal-Overa Basin and make the first attempt to reconstruct the long-term landscape development during the Plio-Quaternary. This is done through integration of geological and geomorphological data obtained through field observations and GIS and remote sensing techniques. In particular, this paper provides a case study that contributes to the understanding of landscape development within tectonically active shear zones. Within the eastern part of the Huércal-Overa Basin, the main tectonic activity is associated with the left-lateral strike-slip Lorca-Alhama fault (oriented NE–SW). During the Late Pliocene and Early Pleistocene, the interaction of this fault with older Miocene ENE–WSW to E–W orientated structures formed a subsiding area with pull-apart basin characteristics termed the Cubeta del Saltador. Subsidence within the Cubeta del Saltador enabled sedimentary infilling by braided rivers with sediment being derived from the Sierra de Las Estancias to the north and the Sierra de Almagro to the south. Sedimentary deformation has resulted in the development of a series of progressive unconformities, angular unconformities and faulting within the alluvial sediments. Towards the end of this stage of landscape development, an increase in tectonic activity resulted in the creation of elevated tectonic highs in the north (Alto de la Garita del Diablo) and east (Loma de Garcı́a) of the Cubeta del Saltador. From the middle Pleistocene onwards, a progressive decrease in tectonic activity is recorded. Alluvial sediments infilled the Cubeta del Saltador. These were dominated by braided river sediments that formed part of a fan-shaped alluvial distributary system derived from the Sierra de las Estancias to the north. In contrast, smaller debris-flow-dominated alluvial fans were derived from the Sierra de Almagro along the southern margin. Currently, the study area presents an asymmetric configuration, reflecting the different topographic characteristics of the northern and southern limiting mountain fronts.