Neogene landscape evolution in the andes of north-central Chile between 28 and 32°S: Interplay between tectonic and erosional processes

We combine geomorphological analysis of palaeosurfaces and U-Pb zircon geochronology of overlying tuffs to reconstruct the Neogene landscape evolution in north-central Chile (28-32°S). Prior to the Early Miocene, a pediplain dominated the landscape of the present-day Coastal Cordillera. The pediplain was offset during the Early (Middle?) Miocene, leading to uplift of the present-day eastern Coastal Cordillera and to the formation of a secondary topographic front. During the Late Miocene, the entire Coastal Cordillera was uplifted, with resulting deposition taking place within river valleys similar to those of the present day. A new pediplain developed on top of these deposits between the Early to Middle Pleistocene and was finally uplifted post-500 ka. These three major uplift stages correlate with episodes of increased deformation widely recognized throughout the Central Andes, starting after a Late Oligocene-Early Miocene episode of increased plate convergence. North of 30°S, the previous palaeotopography along the western Coastal Cordillera probably influenced Neogene landscape evolution. The presence of an inherited palaeotopography together with a strong decrease of precipitation to the north of 30°S would have determined differences in landscape development between this area and the area to the south of 30°S since the Early Miocene.