Alluvial Fan Surfaces In The Atacama Desert: Implications For Surface Modification Rates, The Earthquake Cycle, And Mars

Abstract

The Atacama Desert of Northern Chile is one of the oldest and driest landscapes on Earth. Many studies have referred to this landscape as relict, equating hyperaridity with abandonment as far as landscape modification is concerned. The presence of 26Ma boulders and 13Ma nitrate deposits do highlight landscape elements that have been unmoved due to a lack of precipitation since the onset of hyperaridity at least 10Ma. Evidence for more recent surface modification has caused some researchers to question the persistence of hyperaridity throughout the late Cenozic, emphasizing the potential for wetter and drier periods or even a delayed onset of hyperaridity overall. A series of recent studies, however, have called this perspective into question. One of the predominant criticisms is the sampling of boulders as representative landscape features for surface activation. Present day mudflows and massive mobilizations of sediment during cm-scale rain events provide evidence that, despite the current hyperarid climate, significant landscape modification events can occur. The work of this thesis focuses on two sets of precipitation-driven alluvial fans in the Coastal Cordillera of the Atacama Desert, first determining a base level of activity and then using those activations to study long-term records of coseismic surface deformation and potential implications for the presence of similar features in young craters on Mars.