Laguna Negra is a lake in the

Catamarca Province Catamarca () is a province of Argentina, located in the northwest of the country. The province had a population of 429,556 as per the , and covers an area of 102,602 km2. Its literacy rate is 95.5%. Neighbouring provinces are (clockwise, f ...

Argentina Argentina, officially the Argentine Republic, is a country in the southern half of South America. It covers an area of , making it the List of South American countries by area, second-largest country in South America after Brazil, the fourt ...

. It lies on the Puna high plateau next to two other lakes and

salt flats Salt flats, Salt flat, Salt Flats, or Salt Flat may refer to: Geology *Salt pan (geology), a flat expanse of ground covered with salt and other minerals *Dry lake, an ephemeral lakebed that consists of fine-grained sediments infused with alkali sal ...

. The lake is less than deep and forms a rough rectangle with a surface of . Laguna Negra loses its water through

evaporation Evaporation is a type of vaporization that occurs on the Interface (chemistry), surface of a liquid as it changes into the gas phase. A high concentration of the evaporating substance in the surrounding gas significantly slows down evapora ...

, and is replenished through

surface runoff Surface runoff (also known as overland flow or terrestrial runoff) is the unconfined flow of water over the ground surface, in contrast to ''channel runoff'' (or ''stream flow''). It occurs when excess rainwater, stormwater, meltwater, or other ...

and

groundwater Groundwater is the water present beneath Earth's surface in rock and Pore space in soil, soil pore spaces and in the fractures of stratum, rock formations. About 30 percent of all readily available fresh water in the world is groundwater. A unit ...

which ultimately originate to a large part from

snowmelt In hydrology, snowmelt is surface runoff produced from melting snow. It can also be used to describe the period or season during which such runoff is produced. Water produced by snowmelt is an important part of the annual water cycle in many part ...

. The waters of the lake are salty. On the southeastern shore of the lake,

microbialite Microbialite is a benthic sedimentary deposit made of carbonate mud (particle diameter less than 5 μm) that is formed with the mediation of microbes. The constituent carbonate mud is a type of '' automicrite'' (or ''authigenic carbonate mu ...

s grow in the shallow water. These are structures formed by

carbonate A carbonate is a salt of carbonic acid, (), characterized by the presence of the carbonate ion, a polyatomic ion with the formula . The word "carbonate" may also refer to a carbonate ester, an organic compound containing the carbonate group ...

and microorganisms including

diatom A diatom (Neo-Latin ''diatoma'') is any member of a large group comprising several Genus, genera of algae, specifically microalgae, found in the oceans, waterways and soils of the world. Living diatoms make up a significant portion of Earth's B ...

s and various

bacteria Bacteria (; : bacterium) are ubiquitous, mostly free-living organisms often consisting of one Cell (biology), biological cell. They constitute a large domain (biology), domain of Prokaryote, prokaryotic microorganisms. Typically a few micr ...

. These structures have a layered internal structure and colours ranging from green to orange-pink to black. They have been compared to

Precambrian The Precambrian ( ; or pre-Cambrian, sometimes abbreviated pC, or Cryptozoic) is the earliest part of Earth's history, set before the current Phanerozoic Eon. The Precambrian is so named because it preceded the Cambrian, the first period of t ...

stromatoliths, which were among the oldest forms of life on Earth.

Regional and local

Laguna Negra lies at an elevation of in the Tinogasta Department,

, and near the

San Francisco Pass The San Francisco Pass is a pass over the Andes mountains which connects Argentina and Chile. The highest point of this pass is at AMSL. Location The pass is located at and connects the Argentine province of Catamarca with the Atacama Regi ...

between

Chile Chile, officially the Republic of Chile, is a country in western South America. It is the southernmost country in the world and the closest to Antarctica, stretching along a narrow strip of land between the Andes, Andes Mountains and the Paci ...

and Argentina. The path to

Monte Pissis Monte Pissis is an extinct volcano on the border of the La Rioja and Catamarca provinces in Argentina, to the east of the Chilean border and about north of Aconcagua. The mountain is the second-tallest volcano in the world and the third-highest ...

passes close to the lake. It covers a surface of and has the rough shape of a rectangle. The average depth of the lake does not exceed . The lake periodically floods its beaches. To the northwest, a salt flat separates the lake from its neighbours to the north and covers over half of the lake basin. A prominent

alluvial fan An alluvial fan is an accumulation of sediments that fans outwards from a concentrated source of sediments, such as a narrow canyon emerging from an escarpment. They are characteristic of mountainous terrain in arid to Semi-arid climate, semiar ...

borders Laguna Negra to the southeast and its northward growth has generated a shallow water area at the southeastern margin of the lake (''Stromatolite Belt''). The waters of the lake are

hypersaline A hypersaline lake is a landlocked body of water that contains significant concentrations of sodium chloride, brines, and other salts, with saline levels surpassing those of ocean water (3.5%, i.e. ). Specific microbial species can thrive i ...

, their principal salt is

calcium chloride Calcium chloride is an inorganic compound, a Salt (chemistry), salt with the chemical formula . It is a white crystalline solid at room temperature, and it is highly soluble in water. It can be created by neutralising hydrochloric acid with cal ...

, although they have been described as mesosaline too.

Arsenic Arsenic is a chemical element; it has Symbol (chemistry), symbol As and atomic number 33. It is a metalloid and one of the pnictogens, and therefore shares many properties with its group 15 neighbors phosphorus and antimony. Arsenic is not ...

is present at high concentrations. The high salinity prevents the water from freezing except at the margins of Laguna Negra, where salinity is lower due to

inflow Inflow may refer to: * Inflow (hydrology), the water entering a body of water * Inflow (meteorology) Inflow is the flow of a fluid into a large collection of that fluid. Within meteorology, inflow normally refers to the influx of warmth and mo ...

Calcite Calcite is a Carbonate minerals, carbonate mineral and the most stable Polymorphism (materials science), polymorph of calcium carbonate (CaCO3). It is a very common mineral, particularly as a component of limestone. Calcite defines hardness 3 on ...

and

aragonite Aragonite is a carbonate mineral and one of the three most common naturally occurring crystal forms of calcium carbonate (), the others being calcite and vaterite. It is formed by biological and physical processes, including precipitation fr ...

reach saturation concentration at points where groundwater enters the lake, leading to

precipitation mainly along the southeastern margin of the lake. Conditions in the lake environments are

alkaline In chemistry, an alkali (; from the Arabic word , ) is a basic salt of an alkali metal or an alkaline earth metal. An alkali can also be defined as a base that dissolves in water. A solution of a soluble base has a pH greater than 7.0. The ...

and the consumption of

carbon dioxide Carbon dioxide is a chemical compound with the chemical formula . It is made up of molecules that each have one carbon atom covalent bond, covalently double bonded to two oxygen atoms. It is found in a gas state at room temperature and at norma ...

by degassing and

photosynthesis Photosynthesis ( ) is a system of biological processes by which photosynthetic organisms, such as most plants, algae, and cyanobacteria, convert light energy, typically from sunlight, into the chemical energy necessary to fuel their metabo ...

facilitates carbonate precipitation. The lake is fed mainly by

and by runoff that enters mainly from the southwestern side. The water mainly originates through annual

. Laguna Negra has no surface outflow and is a closed lake; the lake waters evaporate in the strong wind and at high temperatures, leading to the precipitation of salts such as

gypsum Gypsum is a soft sulfate mineral composed of calcium sulfate Hydrate, dihydrate, with the chemical formula . It is widely mined and is used as a fertilizer and as the main constituent in many forms of plaster, drywall and blackboard or sidewalk ...

halite Halite ( ), commonly known as rock salt, is a type of salt, the mineral (natural) form of sodium chloride ( Na Cl). Halite forms isometric crystals. The mineral is typically colorless or white, but may also be light blue, dark blue, purple, pi ...

and

polyhalite Polyhalite is an evaporite mineral, a hydrated sulfate of potassium, calcium and magnesium with formula: . Polyhalite crystallizes in the triclinic system, although crystals are very rare. The normal habit is massive to fibrous. It is typica ...

in a sequential manner from carbonates to salts.

Regional context

Laguna Negra is the southernmost of three lakes aligned in north–south direction; the other two are Laguna de la Salina/Laguna Tres Quebradas to the north and Laguna Verde in the middle. They form the Laguna Verde Saline Complex, also known as Laguna Verde Complex or Salar de la Laguna Verde. The Salar de Tres Quebradas salt pan separates Laguna Verde from Laguna Tres Quebradas. Together these two lakes have a water surface of . Lava flows from surrounding volcanoes have closed off the southern outlet of the valley occupied by the lakes. Smaller lakes exist nearby such as Laguna Azul northeast of Laguna Negra. File:ISS035-E-25019.jpg, alt=Space image of a white plain embedded in mountainous terrain, with a brownish lake to the south. A green lake lies in the middle directly next to the white area, while to the north lies a black lake, Laguna Negra, with Laguna Verde in the middle and Laguna Tres Quebradas/Laguna de la Salina to the north File:ISS035-E-25019 (cropped).jpg, alt=High-elevation photo of a brown lake with a white-brownish plain next to it, Laguna Negra, up is to the north-northwest The lakes lie in the southernmost Puna, a high plateau at an elevation of where a dry climate and

Cenozoic The Cenozoic Era ( ; ) is Earth's current geological era, representing the last 66million years of Earth's history. It is characterized by the dominance of mammals, insects, birds and angiosperms (flowering plants). It is the latest of three g ...

uplift generated the Laguna Verde Saline Complex when block faulting generated separated drainage basins separated by north–south trending mountain ranges. The terrain consists mainly of volcanic rocks such as

basalt Basalt (; ) is an aphanite, aphanitic (fine-grained) extrusive igneous rock formed from the rapid cooling of low-viscosity lava rich in magnesium and iron (mafic lava) exposed at or very near the planetary surface, surface of a terrestrial ...

and

andesite Andesite () is a volcanic rock of intermediate composition. In a general sense, it is the intermediate type between silica-poor basalt and silica-rich rhyolite. It is fine-grained (aphanitic) to porphyritic in texture, and is composed predomina ...

; some summits exceed elevation above sea level such as the high Cerro Pissis.

Evaporite An evaporite () is a water- soluble sedimentary mineral deposit that results from concentration and crystallization by evaporation from an aqueous solution. There are two types of evaporite deposits: marine, which can also be described as oce ...

sand Sand is a granular material composed of finely divided mineral particles. Sand has various compositions but is usually defined by its grain size. Sand grains are smaller than gravel and coarser than silt. Sand can also refer to a textural ...

and

silt Silt is granular material of a size between sand and clay and composed mostly of broken grains of quartz. Silt may occur as a soil (often mixed with sand or clay) or as sediment mixed in suspension (chemistry), suspension with water. Silt usually ...

cover the terrain around the lake.

Climate, vegetation and fauna

The climate at Laguna Negra is cold,

arid Aridity is the condition of geographical regions which make up approximately 43% of total global available land area, characterized by low annual precipitation, increased temperatures, and limited water availability.Perez-Aguilar, L. Y., Plata ...

with strong winds. Temperature is highly variable, ranging between in summer and between in winter. Annual precipitation is less than and falls mainly as

snow Snow consists of individual ice crystals that grow while suspended in the atmosphere—usually within clouds—and then fall, accumulating on the ground where they undergo further changes. It consists of frozen crystalline water througho ...

. Evidence from other lakes in the region suggests that the environment was wetter than today between about 15,000–14,000 and 13,500–11,300 years before becoming dry during the middle

Holocene The Holocene () is the current geologic time scale, geological epoch, beginning approximately 11,700 years ago. It follows the Last Glacial Period, which concluded with the Holocene glacial retreat. The Holocene and the preceding Pleistocene to ...

. After about 4,000 years BP precipitation has increased again. Presently, the climate is dominated by the

South Pacific High The South Pacific High is a semi-permanent subtropical anticyclone located in the southeast Pacific Ocean. The area of high atmospheric pressure and the presence of the Humboldt Current in the underlying ocean make the west coast of Peru and nort ...

anticyclone A high-pressure area, high, or anticyclone, is an area near the surface of a planet where the atmospheric pressure is greater than the pressure in the surrounding regions. Highs are middle-scale meteorological features that result from interpl ...

which draws dry air into the region. During summer, an

Atlantic The Atlantic Ocean is the second largest of the world's five oceanic divisions, with an area of about . It covers approximately 17% of Earth's surface and about 24% of its water surface area. During the Age of Discovery, it was known for se ...

anticyclone conversely transports moister and warmer air to the area, resulting in the formation of

convective Convection is single or multiphase fluid flow that occurs spontaneously through the combined effects of material property heterogeneity and body forces on a fluid, most commonly density and gravity (see buoyancy). When the cause of the convec ...

clouds and precipitation. Climatic conditions together with the thin atmosphere at high elevations and high

UV radiation Ultraviolet radiation, also known as simply UV, is electromagnetic radiation of wavelengths of 10–400 nanometers, shorter than that of visible light, but longer than X-rays. UV radiation is present in sunlight and constitutes about 10% of t ...

limit the complexity of life at Laguna Negra, in particular of nonmicrobial life. In this sector of the Andes,

peatland A peatland is a type of wetland whose soils consist of Soil organic matter, organic matter from decaying plants, forming layers of peat. Peatlands arise because of incomplete decomposition of organic matter, usually litter from vegetation, du ...

s are the key ecosystems, with the dominant plant species being '' Distichia muscoides'', '' Oxychloe andina'' and ''

Plantago rigida ''Plantago rigida'', colloquially known as "Colchón de agua" (water mattress), is a species of flowering plant in the plantain family found in the high-altitude páramo biome of South America. Distribution Bolivia, Colombia, Ecuador, Peru, Ven ...

'' as well as

graminoid In botany and ecology, a graminoid refers to a herbaceous plant with a grass-like morphology, i.e., elongated culms with long, blade-like leaves. They are contrasted with forbs, herbaceous plants without grass-like features. The plants most ...

s and

grass Poaceae ( ), also called Gramineae ( ), is a large and nearly ubiquitous family (biology), family of monocotyledonous flowering plants commonly known as grasses. It includes the cereal grasses, bamboos, the grasses of natural grassland and spe ...

es.

Mite Mites are small arachnids (eight-legged arthropods) of two large orders, the Acariformes and the Parasitiformes, which were historically grouped together in the subclass Acari. However, most recent genetic analyses do not recover the two as eac ...

s are their most important fauna.

Salt marsh A salt marsh, saltmarsh or salting, also known as a coastal salt marsh or a tidal marsh, is a coastal ecosystem in the upper coastal intertidal zone between land and open saltwater or brackish water that is regularly flooded by the tides. I ...

grasses of the genus ''

Spartina ''Spartina'' is a genus of plants in the grass family, frequently found in coastal salt marshes. Species in this genus are commonly known as cordgrass or cord-grass, and are native to the coasts of the Atlantic Ocean in western and southern Eu ...

'' grow at the southern end of the lake, and

copepod Copepods (; meaning 'oar-feet') are a group of small crustaceans found in nearly every freshwater and saltwater habitat (ecology), habitat. Some species are planktonic (living in the water column), some are benthos, benthic (living on the sedimen ...

s have been observed in ponds; both are linked to areas with lower salinity. The lakes are an important bird conservation site, and were added to the "South Sub-site of the Ramsar Sites, Lagunas Altoandinas y Puneñas de Catamarca"

Ramsar Site A Ramsar site is a wetland site designated to be of international importance under the Ramsar Convention,8 ha (O) *** Permanent 8 ha (P) *** Seasonal Intermittent < 8 ha(Ts) **

microbial mat A microbial mat is a multi-layered sheet or biofilm of microbial colonies, composed of mainly bacteria and/or archaea. Microbial mats grow at interfaces between different types of material, mostly on submerged or moist surfaces, but a few surviv ...

s and

microbialites Microbialite is a benthic sedimentary deposit made of carbonate mud (particle diameter less than 5 μm) that is formed with the mediation of microbes. The constituent carbonate mud is a type of '' automicrite'' (or ''authigenic carbonate mud'') ...

occur at Laguna Negra and have diverse shapes. Their formation results mainly from the localized precipitation of

s where new water enters Laguna Negra. At the southern end of the lake,

travertine Travertine ( ) is a form of terrestrial limestone deposited around mineral springs, especially hot springs. It often has a fibrous or concentric appearance and exists in white, tan, cream-colored, and rusty varieties. It is formed by a process ...

crusts are found; they might form at sites of groundwater entry. Active

tufa Tufa is a variety of limestone formed when carbonate minerals precipitation (chemistry), precipitate out of water in ambient temperature, unheated rivers or lakes. hot spring, Geothermally heated hot springs sometimes produce similar (but less ...

formation has been observed, making Laguna Negra one of only two lakes in the region where it takes place. White incrustations are formed by evaporation, when

salt In common usage, salt is a mineral composed primarily of sodium chloride (NaCl). When used in food, especially in granulated form, it is more formally called table salt. In the form of a natural crystalline mineral, salt is also known as r ...

precipitates. Laguna Tres Quebradas north of Laguna Negra also features microbialites, which cover an area of in the

river delta A river delta is a landform, archetypically triangular, created by the deposition of the sediments that are carried by the waters of a river, where the river merges with a body of slow-moving water or with a body of stagnant water. The creat ...

of the Salado River. In the ''Stromatolite Belt'', a large area at the southeastern part of the lake where water depths do not exceed , they form laminar crusts,

oncoid Oncolites are sedimentary structures composed of oncoids, which are layered structures formed by the growth of one or more species of microorganisms, usually containing cyanobacteria. Oncolites are very similar to stromatolites, but, instead of ...

s and

stromatolite Stromatolites ( ) or stromatoliths () are layered Sedimentary rock, sedimentary formation of rocks, formations (microbialite) that are created mainly by Photosynthesis, photosynthetic microorganisms such as cyanobacteria, sulfate-reducing micr ...

s that are accompanied by microbial mats. These microbialites are found mainly in the northeastern Stromatolite Belt, while its central and western portions feature abiotic carbonate precipitation. A subdivision in a plant-grown sector, a non-mineralized sector and a carbonate precipitation sector is possible. Oncoids make up the bulk of the Stromatolite Belt. They can have smooth forms and ridged, pillar- or shrub-like protrusions and reach dimensions of over . They can be buried in mud, submerged or partially emerged, and sometimes covered with

. Colours range from green-yellow over orange to snow white, and the structures have the appearance of rocks strewn onto and emerging from the shallow lake. The oncoids have a concentrically layered internal structure, with the various layers often having different colours; the colour variations relate to compositional differences. The microscopic texture has been described as sparry, "micritic" and "botryoidal". Other growth forms are laminar crusts and column-shaped or flat stromatoliths. Oncoids also occur in the Salado river north of Laguna Tres Quebradas. Microbial mats have colours ranging from back over pinkish-orange to greenish, and their structure ranges from pustular to stratified. Most are associated with oncoids. Greenish mats occur next to groundwater springs and often are found floating on bubbles, and black mats are found on partially exposed carbonates. The black mats are formed mainly by filamentous

cyanobacteria Cyanobacteria ( ) are a group 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 cyanobacteri ...

of the '' Rivularia'' family. Layered microbial mats, where different layers have different colours, are found within deep ponds. So-called "diatom blooms" are linked to white carbonate precipitates that form bright spots on the coloured mats. The colours of the microbial constructs are due to

carotenoid Carotenoids () are yellow, orange, and red organic pigments that are produced by plants and algae, as well as several bacteria, archaea, and fungi. Carotenoids give the characteristic color to pumpkins, carrots, parsnips, corn, tomatoes, cana ...

and

scytonemin Scytonemin is a secondary metabolite and an extracellular matrix (sheath) pigment synthesized by many strains of cyanobacteria, including ''Nostoc'', '' Scytonema'', ''Calothrix'', '' Lyngbya'', ''Rivularia'', '' Chlorogloeopsis'', and ''Hyella'' ...

pigments, which serve to protect the microorganisms from

Radiometric dating Radiometric dating, radioactive dating or radioisotope dating is a technique which is used to Chronological dating, date materials such as Rock (geology), rocks or carbon, in which trace radioactive impurity, impurities were selectively incorporat ...

of the carbonate structures is difficult owing to the scarcity of datable material, but uranium-thorium dating performed on one oncolite indicates that it began to develop in the

Late Holocene Late or LATE may refer to: Everyday usage * Tardy, or late, not being on time * Late (or the late) may refer to a person who is dead Music * ''Late'' (The 77s album), 2000 * Late (Alvin Batiste album), 1993 * Late!, a pseudonym used by Dave Groh ...

. Observations indicate that the growth of the oncoliths is still ongoing.

Biology and scientific importance

There are both

autotrophic An autotroph is an organism that can convert abiotic sources of energy into energy stored in organic compounds, which can be used by other organisms. Autotrophs produce complex organic compounds (such as carbohydrates, fats, and proteins) us ...

and

heterotrophic A heterotroph (; ) is an organism that cannot produce its own food, instead taking nutrition from other sources of organic carbon, mainly plant or animal matter. In the food chain, heterotrophs are primary, secondary and tertiary consumers, but ...

microorganisms in Laguna Negra. Autotrophs include

, as well as

green sulfur bacteria The green sulfur bacteria are a phylum, Chlorobiota, of obligately anaerobic photoautotrophic bacteria that metabolize sulfur. Green sulfur bacteria are nonmotile (except ''Chloroherpeton thalassium'', which may glide) and capable of anoxyg ...

and

purple sulfur bacteria The purple sulfur bacteria (PSB) are part of a group of Pseudomonadota capable of photosynthesis, collectively referred to as purple bacteria. They are anaerobic or microaerophilic, and are often found in stratified water environments includi ...

which conduct

anoxygenic photosynthesis Anoxygenic photosynthesis is a special form of photosynthesis used by some bacteria and archaea, which differs from the better known oxygenic photosynthesis in plants in the reductant used (e.g. hydrogen sulfide instead of water) and the byproduc ...

;

sulfur Sulfur ( American spelling and the preferred IUPAC name) or sulphur ( Commonwealth spelling) is a chemical element; it has symbol S and atomic number 16. It is abundant, multivalent and nonmetallic. Under normal conditions, sulfur atoms ...

deposits form during the process. Heterotrophic organisms include

polysaccharide Polysaccharides (), or polycarbohydrates, are the most abundant carbohydrates found in food. They are long-chain polymeric carbohydrates composed of monosaccharide units bound together by glycosidic linkages. This carbohydrate can react with wat ...

degrading and

sulfate-reducing bacteria Sulfate-reducing microorganisms (SRM) or sulfate-reducing prokaryotes (SRP) are a group composed of sulfate-reducing bacteria (SRB) and sulfate-reducing archaea (SRA), both of which can perform anaerobic respiration utilizing sulfate () as termina ...

. There is a layering in metabolic activity, with regular photosynthesis at the surface, anoxygenic photosynthesis in intermediary layers and sulfate reduction at depth. Many microorganisms are

extremophile An extremophile () is an organism that is able to live (or in some cases thrive) in extreme environments, i.e., environments with conditions approaching or stretching the limits of what known life can adapt to, such as extreme temperature, press ...

s and tolerate high salinity and intense

. Precipitation of carbonates is often associated with life and may be induced by the latter for various reasons, although at Laguna Negra it can also occur independently from biological activity. Subtle environmental variations and changes influence the life in the lake and the structure of the microbial mats. The microbial mats are found in the less saline sector of Laguna Negra, implying that reduced salt stress favours their development.

Stromatolites Stromatolites ( ) or stromatoliths () are layered sedimentary formations ( microbialite) that are created mainly by photosynthetic microorganisms such as cyanobacteria, sulfate-reducing bacteria, and Pseudomonadota (formerly proteobacteria) ...

have been found elsewhere in the Puna, at

Socompa Socompa is a large stratovolcano (composite volcano) on the border of Argentina and Chile. It has an elevation of and is part of the Chilean and Argentine Andean Volcanic Belt (AVB). Socompa is within the Central Volcanic Zone, one of the segme ...

and Tolar Grande. They are considered to be among the oldest forms of life on Earth and a key indicator in the search for

extraterrestrial life Extraterrestrial life, or alien life (colloquially, aliens), is life that originates from another world rather than on Earth. No extraterrestrial life has yet been scientifically conclusively detected. Such life might range from simple forms ...

. The forms found at Laguna Negra resemble these of ancient

stromatolites more than these of recent

Proterozoic The Proterozoic ( ) is the third of the four geologic eons of Earth's history, spanning the time interval from 2500 to 538.8 Mya, and is the longest eon of Earth's geologic time scale. It is preceded by the Archean and followed by the Phanerozo ...

stromatolites, and the conditions encountered at the lake may resemble these of

Early Earth Early Earth also known as Proto-Earth is loosely defined as Earth in its first one billion years, or gigayear (Ga, 109 y), from its initial formation in the young Solar System at about 4.55 Ga to some time in the Archean eon in approximately 3.5 Ga ...

and Early Mars and could thus be used as an analogue to interpret deposits on Mars. Analyses of

isotope fractionation Isotope fractionation describes fractionation processes that affect the relative abundance of isotopes, a phenomena that occurs (and so advantage is taken of it) in the study geochemistry, biochemistry, food science, and other fields. Normally, ...

processes at Laguna Negra also demonstrate that oxygen and carbon isotope variations are not necessarily proof of biological activity.

Microbes

Cyanobacteria and diatoms form aggregates together and with other microorganisms. The aggregates in turn are embedded in

exopolysaccharide Extracellular polymeric substances (EPS) are natural polymers of high molecular weight secreted by microorganisms into their environment. EPS establish the functional and structural integrity of biofilms, and are considered the fundamental compo ...

capsules where carbonates precipitate. Living diatoms are often found at the margin of aggregates while their interiors feature " entombed" diatoms. The bacterial species '' Rivularia halophila'' was discovered at Laguna Negra; it is the first ''Rivularia'' species known from hypersaline inland waters. Another species identified and named there is '' Exiguobacterium chiriqhucha'', although that species was originally discovered elsewhere.

Regional and local

Regional context

Climate, vegetation and fauna

Biology and scientific importance

Microbes

Notes

References

Sources

External links