Limestone is a type of carbonate sedimentary rock which is the main source of the material lime. It is composed mostly of the minerals calcite and aragonite, which are different crystal forms of CaCO3. Limestone forms when these minerals precipitate out of water containing dissolved calcium. This can take place through both biological and nonbiological processes, though biological processes, such as the accumulation of corals and shells in the sea, have likely been more important for the last 540 million years. Limestone often contains fossils which provide scientists with information on ancient environments and on the evolution of life.
Sandstone is a clastic sedimentary rock composed mainly of sand-sized silicate grains, cemented together by another mineral. Sandstones comprise about 20–25% of all sedimentary rocks.
Stromatolites or stromatoliths are layered sedimentary formations (microbialite) that are created mainly by photosynthetic microorganisms such as cyanobacteria, sulfate-reducing bacteria, and Pseudomonadota. These microorganisms produce adhesive compounds that cement sand and other rocky materials to form mineral "microbial mats". In turn, these mats build up layer by layer, growing gradually over time.
Cyanobacteria, also called Cyanobacteriota or Cyanophyta, are a phylum of autotrophic gram-negative bacteria that can obtain biological energy via oxygenic photosynthesis. The name "cyanobacteria" refers to their bluish green (cyan) color, which forms the basis of cyanobacteria's informal common name, blue-green algae, although as prokaryotes they are not scientifically classified as algae.
The Inn is a river in Switzerland, Austria and Germany. The 518 km (322 mi) long river is a right tributary of the Danube, being the third largest tributary of the Danube by discharge. The highest point of its drainage basin is the summit of Piz Bernina at 4,049 m (13,284 ft). The Engadine, the valley of the En, is the only Swiss valley whose waters end up in the Black Sea.
Tufa is a variety of limestone formed when carbonate minerals precipitate out of water in unheated rivers or lakes. Geothermally heated hot springs sometimes produce similar carbonate deposits, which are known as travertine or thermogene travertine. Tufa is sometimes referred to as meteogene travertine.
El Tatio is a geothermal field with many geysers located in the Andes Mountains of northern Chile at 4,320 metres (14,170 ft) above mean sea level. It is the third-largest geyser field in the world and the largest in the Southern Hemisphere. Various meanings have been proposed for the name "El Tatio", including "oven" or "grandfather". The geothermal field has many geysers, hot springs, and associated sinter deposits. These hot springs eventually form the Rio Salado, a major tributary of the Rio Loa, and are a major source of arsenic pollution in the river. The vents are sites of populations of extremophile microorganisms such as hyperthermophiles, and El Tatio has been studied as an analogue for the early Earth and possible past life on Mars.
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.
Salar de Atacama, located 55 km (34 mi) south of San Pedro de Atacama, is the largest salt flat in Chile. It is surrounded by mountains and lacks drainage outlets. To the east, it is enclosed by the main chain of the Andes, while to the west lies a secondary mountain range called Cordillera de Domeyko. The landscape is dominated by imposing volcanoes such as Licancabur, Acamarachi, Aguas Calientes, and Láscar, the latter being one of Chile's most active volcanoes. These volcanoes are situated along the eastern side of the Salar de Atacama, forming a north–south trending line that separates it from smaller endorheic basins.
Thrombolites are clotted accretionary structures formed in shallow water by the trapping, binding, and cementation of sedimentary grains by biofilms of microorganisms, especially cyanobacteria.
Girvanella is a fossil thought to represent the calcified sheath of a filamentous cyanobacterium known from the Burgess Shale and other Cambrian fossil deposits. Specimens are also known from the Early Ordovician San Juan Formation, Argentina.
Microbially induced sedimentary structures (MISS) are primary sedimentary structures formed by the interaction of microbes with sediment and physical agents of erosion, deposition, and transportation. The structures commonly form when microbial mats are preserved in the sedimentary geological record. There are 17 main types of macroscopic and microscopic MISS. Of those, wrinkle structures and microbial mat chips are the most abundant in the fossil record. Other MISS include sinoidal structures, polygonal oscillation cracks, multidirected ripple marks, erosional remnants and pockets, or gas domes.
The extinct genus Hedstroemia was once thought to be a rivulariacean cyanobacterium. It forms oval blobs composed of sinuous tubes that have rounded outlines and occurs in conjunction with Solenopora.
Sphaerocodium is a fossil that represents the remains of bacteria in the phylum Cyanobacteria, often called blue-green algae.
Cerro Archibarca is a volcano in the Andes, in Salta Province, Argentina. It covers a surface area of 20 square kilometres (7.7 sq mi). Lava flows descend from a conical edifice. It was active 11 million years ago. The youngest deposits are eroded andesites on the northern side.
Antofalla is a Miocene-Pliocene volcano in Argentina's Catamarca Province. It is part of the volcanic segment of the Andes in Argentina, and it is considered to be part of the Central Volcanic Zone, one of the volcanic zones of the Andes. Antofalla forms a group of volcanoes that are aligned on and behind the main volcanic arc. Antofalla itself is a remote volcano.
Tata Sabaya is a 5,430-metre (17,810 ft) high volcano in Bolivia. It is part of the Central Volcanic Zone, one of several volcanic belts in the Andes which are separated by gaps without volcanic activity. This section of the Andes was volcanically active since the Jurassic, with an episode of strong ignimbritic volcanism occurring during the Miocene. Tata Sabaya lies in a thinly populated region north of the Salar de Coipasa salt pan.
"Porostromata" is an antiquated form taxon that refers to fossil cyanobacteria. The term porostromate is also used as a descriptor of textures and microstructure of stromatolites and oncolites which contain tubules or other cellular structures.
"Spongiostromata" is an antiquated form taxon that refers primarily to fossil cyanobacteria. "Spongiostromate" is also used to describe stromatolites and oncolites that do not preserve clear tubules or other cellular microstructure.
Laguna Negra is a lake in the Catamarca Province of Argentina. It lies on the Puna high plateau next to two other lakes and salt flats. The lake is less than 2 metres deep and forms a rough rectangle with a surface of 8.6 square kilometres (3.3 sq mi). Laguna Negra loses its water through evaporation, and is replenished through surface runoff and groundwater which ultimately originate to a large part from snowmelt. The waters of the lake are salty.
