Mineralogy and micromorphology of an Atacama Desert soil, Chile: A model for hyperarid pedogenesis

The Atacama Desert is the oldest and driest desert on Earth. Hyperarid soils in this desert are dominated by rare (or exclusive) salt minerals and assemblages. Previous research details salt origins and abundance, however pedogenic processes involved in salt distribution are not adequately explained. Therefore, the main goal of this investigation was to identify and document evidence for hyperarid pedogenesis (via salt mineralogy and soil micromorphology) at a field site, Oficina Ercilla, located ∼80 km northeast of Antofagasta, Chile within the Central Depression and hyperarid core of the Atacama Desert. This study presents an interpretational model for hyperarid pedogenesis, which supports the salt heave hypothesis proposed by Buck et al. (2006). Hyperarid pedogenesis incorporates many known pedogenic processes (e.g. eolian deposition, clast shatter, pressure solution). However, salt heave processes dominate with a self sustaining feed-back loop initiated and perpetuated by long term influx and retention of salt minerals.