Relief and drainage evolution during the exhumation of the Sierra Nevada (SE Spain): Is denudation keeping pace with uplift?

- River incision in Sierra Nevada is conditioned by tectonics and local base level.
- Western Sierra Nevada concentrates main elevation and higher denudation rates.
- Uplift of western Sierra Nevada transforms old longitudinal drainage in water gaps.
- We can establish a steady-state between uplift and denudation in the Central Betics.
- Extension in the central Betics cannot be understood in terms of thin-shell tectonics.

We have performed a geomorphic analysis of the Sierra Nevada, the highest range of the Betic Cordillera (SE Spain), with the aim to elucidate its late Miocene to present-day exhumation history. The qualitative and quantitative analysis is based on filtered topography, local relief, swath-profile analysis, anomalies on stream orientation, bulk erosion volume, hypsometry, and steepness index (ksn). All these parameters are intimately linked to river incision and development of drainage pattern, having been calculated to assess the role of folding and faulting on the evolution of the Sierra Nevada. Moreover, uplift rates in the core of the Sierra Nevada have been deduced from an extrapolation of the position of Late Tortonian to Pliocene coastline deposits. These data have been compared to apatite (U-Th)/He, fission-track and 10Be cosmogenic data from SE Spain in order to evaluate the consistency among uplift, thermal histories and denudation rates. Our preferred tectonic scenario is one that favors fast exhumation of the western Sierra Nevada in a NW-SE overall compressive setting produced by the convergence between the Nubia and Africa plates. Sub-perpendicular to this compression, a westward 4 mm/year extensional hanging-wall displacement promotes uplift and unroofing of the western part of Sierra Nevada.