Peinado is a stratovolcano in Catamarca Province, Argentina. It consists of a volcanic cone with a summit crater, surrounded at its foot by lava flows erupted from flank vents. It began erupting about 100,000 years ago, with the last eruption about 36,800 years ago. Future eruptions are possible.
The volcano is part of the Andean Central Volcanic Zone and located within a cluster of calderas and large volcanoes, including the Laguna Amarga caldera just west of Peinado. The climate of the region is cold and dry, but may have been moister in the recent past. North of Peinado lies the salt lake Laguna Peinado.
Geography and geomorphology
Peinado lies in Argentina's Catamarca Province, close to the border with Chile and about from the Paso San Francisco. Geographically, it is in the Cordillera Occidental of the Central Andes. The region is largely uninhabited, due to the extreme climatic conditions.
The volcano is a high steep cone, which reaches an elevation of above sea level and features a wide and deep summit crater with an ephemeral crater lake. There is no perennial snow cover or glaciers on the mountain. Twelve vents - two of which are buried by lava flows - form cones on its flanks and have produced hundreds of lava flows, which built a lava apron surrounding the volcano that buries the lower parts of the cone. The cone is formed by lava blocks, lavas, pyroclastics and scoria; the lava flows have for the most part dark and brown colours. The total volume of the edifice is about , covering an area of . Claims that the volcano overlies a caldera lack supporting evidence.
Just west of Peinado lies the eastern margin of the Pliocene Laguna Amarga caldera; its ignimbrites underlie Peinado and lava flows from Peinado have spilled across its borders on to the caldera floor. On the eastern side, the volcano is bordered by the Sierra de Calalaste. To the north lies the Salar de Antofalla, which ends close to Peinado, and the Laguna Peinado lake. A field of monogenetic volcanoes, the Peinado volcanic field, lies around Peinado. They consist of lava flows, maars, scoria cones and tuff rings, with volumes reaching , and were emplaced between 600,000 and 150,000 years ago.
Lake
Laguna Peinado is a lake with an area of and a depth of . It lies at elevation at about . It is a salt lake with alkaline waters, fed mostly by groundwater and meltwater. An additional water source are hot springs with temperatures reaching , which deposit travertine. Volcanic carbon dioxide outgassing appears to occur at the lake. The lake presently has no outflow, but it may have spilled northward into the Salar de Antofalla during periods of higher lake level. Directly north of Laguna Peinado lies another lake, Laguna Turquesa, with an average depth of and a surface area of ; the lakes may have been connected before 2005. At the northern end of the basin, coastal terraces reach thicknesses of and lengths of several , they extend to Laguna Turquesa.
Lake sediments consist of an alternation of organic muds, calcite and travertine, with limestones occurring in coastal areas and muddy deposits in deeper waters. The carbonates form micrites, packstones, rudstones and wackestones, and they contain fossil diatoms and ostracods.
There is evidence of a progressive increase in water levels, followed by a decrease, which may somehow relate to the Little Ice Age. They may be correlative with regional changes in humidity, but difficulties in dating lake deposits prevent the determination of a definitive causal relationship.
The lakes of the Altiplano have drawn attention in the 21st century owing to the frequently extreme climatic and hydrological conditions they experience. Former stromatolites occur on the lowest lake terrace, they display laminated textures and were probably built by cyanobacteria when the lake levels were low and conditions more favourable to stromatolite growth than plant development. Recent lake level declines have not prevented the deposition of microbe-produced rocks. Stromatolites are visible just underneath the water surface.