A climatic control on the formation of gigantic gypsum crystals within the hypogenic caves of Naica (Mexico)?

Three hypogenic caves recently discovered within the extensive Naica mine of Mexico host spectacular gypsum crystals up to 12 m in length. These caves occur close to another known cave of the area, with which they form a unique 160 m-deep system of hypogenic caves. A unique combination of multi-technique fluid inclusion analysis and pollen spectral analysis from cave and mine gypsum show that the climatic changes occurring at Naica at the time of speleogenesis must have controlled substantially the composition of the infiltrating fluid in these caves, and hence crystal growth. Alternations of wet/fresh and dry/hot climatic periods generated at shallow depths a high-salinity (epifreatic) fluid, which mixed in various proportions with a chemically homogeneous, low salinity deep (freatic) fluid resulting in the growth of gigantic crystals only at greater depths within the cave system. This mechanism generated stable supersaturation conditions for the gigantic crystals to grow, making the hypogenic caves a deep repository of paleoclimatic data