The Naica Caves, Chihuahua, Mexico

Abstract

The caves of Naica (Chihuahua, Mexico) have been known since the beginning of the nineteenth century, when they were intersected by mines. They became world famous in 2000 when the mining activities intersected three small caves, which hosted gigantic gypsum crystals. Their genesis and evolution is strictly related to rising thermal fluids induced by Tertiary intrusive magmatic activity, giving rise to polysulfide deposits. Speleogenesis began about 1.5 Myr BP, induced by rising thermal water. This process lasted for a relatively short time. Later evolutionary stages varied from cave to cave, reflecting alternately deep-seated phreatic, epiphreatic, and vadose environments. Deposition of the giant gypsum crystals began ~400–350 Kyr BP, when the water temperature dropped below 58 °C. Their growth suddenly ceased in 1985, when mine dewatering dried up the caves. Besides the giant gypsum crystals, Naica caves contain a wide variety of other cave minerals (over 40), ten of which are new for the cavern environment. In addition, they include fossil pollen trapped in the gypsum lattice, which allow reconstruction of the external climate of 350 Kyr BP, and microorganisms new to science, which were preserved in the fluid inclusions of the gypsum crystals for tens or even hundreds of thousands of years. In 2015, mining intercepted a major thermal water source, which flooded the mine, and the Cueva de los Cristales and other caves at −290 m were flooded by more than 160 m of hot water.