Cave deposits in Cordillera de la Sal (Atacama, Chile)

Although the Atacama Desert is one of the driest places on earth there are several halite caves in the Oligocene-Miocene outcrop of evaporites that forms the Cordillera de la Sal. The caves contain a variety of deposits including speleothems, allogenic sediments, and archaeological remains that have provided information on cave evolution and proxy information on past climates in the area. This study presents the first report of monocrystalline halite stalactites whose initial formation and subsequent evolution are controlled by (1) the degree of supersaturation of the feeding solution, (2) capillary and/or gravity flow along the speleothem, and (3) air currents in the cave. Also, we report a new cave mineral (atacamite) together with a zeolite (clinoptilolite), where genesis was controlled by thermal fluids rising under pressure along a fault plane. Analysis and radiocarbon dating of the allogenic sediments and archaeologic remains shows that the halite caves of Atacama are very young and that development is rapid during rare floods brought on by sudden, short rainstorms that may only affect a single stream catchment. By contrast, between these rare events, which may be several hundred years apart, there is little or no cave development.