Paleocene surface exposure ages imply an early development of hyperaridity in the Atacama Desert

The (hyper-) arid climate of the Atacama Desert preserves traces of ancient landforms. Clusters of cosmogenic ²¹Ne exposure ages of pebbles from Early Miocene sediment surfaces indicate the preservation and continuous exposure (low to no erosive surface activity) since the Late Eocene, with distinct phases of low fluvial activity and deposition during the Neogene. A reduction of significant fluvial activity since ~10 Ma, and the complete absence since ~1-2 Ma, indicate extreme hyperarid conditions.  Single exposure histories of Paleocene age, with age clusters during the Eocene and Oligocene, demonstrate remarkable landscape stability throughout the Cenozoic. Phases of fluvial activity, i.e. the end of a fluvial period and the beginning of continuous exposure to cosmic rays, coincide closely with trends and aberrations in regional and global Cenozoic climate variability.