Gypsum-lined degassing holes in tumuli

Small, circular holes, lined with a thin gypsum veneer, and closely associated with gypsum tumuli (domes), occur at Salar de Pajonales, a salt flat in the northern Andes, Chile. We propose a model in which the formation of the gypsum-lined holes, and less commonly the formation of the tumuli itself, is controlled by the unique juxtaposition of physiographic, geologic and hydrologic conditions. On a regional scale, Salar de Pajonales is unusual compared to other salars, as it is located close to a large magmatic inflation centre (Lazufre), lies along strike of major regional structural trends, is a large ephemeral lake and contains high salt concentrations. On a basin scale, the lined holes are only present along strike of lineaments that are directly linked to the local stress regime. In turn, these lineaments control the location of degassing and subsequently the formation of the lined holes in the gypsum tumuli and, in part, the tumuli themselves. The purpose of this paper is to (1) present peculiar lined-holes in gypsum tumuli from Salar de Pajonales, Chile, (2) compare their spatial distribution to physiographic, geologic and hydrologic parameters to constrain the controls on formation, (3) propose a new model of the formation of the lined-holes that is compatible with the observations and the collocation and synchronous relationships and constraints and (4) provide a new exploration model that could assist with search for life on Mars and other planets.image