85-568: The vicuña ( Lama vicugna ) or vicuna (both / v ɪ ˈ k uː n j ə / , very rarely spelled vicugna , its former genus name) is one of the two wild South American camelids , which live in the high alpine areas of the Andes ; the other camelid is the guanaco , which lives at lower elevations. Vicuñas are relatives of the llama , and are now believed to be the wild ancestor of domesticated alpacas , which are raised for their coats. Vicuñas produce small amounts of extremely fine wool , which
170-455: A Mohs hardness of 2 to 4, dense limestone can have a crushing strength of up to 180 MPa . For comparison, concrete typically has a crushing strength of about 40 MPa. Although limestones show little variability in mineral composition, they show great diversity in texture. However, most limestone consists of sand-sized grains in a carbonate mud matrix. Because limestones are often of biological origin and are usually composed of sediment that
255-457: A bloom of cyanobacteria or microalgae . However, stable isotope ratios in modern carbonate mud appear to be inconsistent with either of these mechanisms, and abrasion of carbonate grains in high-energy environments has been put forward as a third possibility. Formation of limestone has likely been dominated by biological processes throughout the Phanerozoic , the last 540 million years of
340-434: A carbonate rock outcrop can be estimated in the field by etching the surface with dilute hydrochloric acid. This etches away the calcite and aragonite, leaving behind any silica or dolomite grains. The latter can be identified by their rhombohedral shape. Crystals of calcite, quartz , dolomite or barite may line small cavities ( vugs ) in the rock. Vugs are a form of secondary porosity, formed in existing limestone by
425-612: A central quartz grain or carbonate mineral fragment. These likely form by direct precipitation of calcium carbonate onto the ooid. Pisoliths are similar to ooids, but they are larger than 2 mm in diameter and tend to be more irregular in shape. Limestone composed mostly of ooids is called an oolite or sometimes an oolitic limestone . Ooids form in high-energy environments, such as the Bahama platform, and oolites typically show crossbedding and other features associated with deposition in strong currents. Oncoliths resemble ooids but show
510-449: A change in environment that increases the solubility of calcite. Dense, massive limestone is sometimes described as "marble". For example, the famous Portoro "marble" of Italy is actually a dense black limestone. True marble is produced by recrystallization of limestone during regional metamorphism that accompanies the mountain building process ( orogeny ). It is distinguished from dense limestone by its coarse crystalline texture and
595-949: A composition reflecting the organisms that produced them and the environment in which they were produced. Low-magnesium calcite skeletal grains are typical of articulate brachiopods , planktonic (free-floating) foraminifera, and coccoliths . High-magnesium calcite skeletal grains are typical of benthic (bottom-dwelling) foraminifera, echinoderms , and coralline algae . Aragonite skeletal grains are typical of molluscs , calcareous green algae , stromatoporoids , corals , and tube worms . The skeletal grains also reflect specific geological periods and environments. For example, coral grains are more common in high-energy environments (characterized by strong currents and turbulence) while bryozoan grains are more common in low-energy environments (characterized by quiet water). Ooids (sometimes called ooliths) are sand-sized grains (less than 2mm in diameter) consisting of one or more layers of calcite or aragonite around
680-412: A considerable fraction of the limestone bed. At depths greater than 1 km (0.62 miles), burial cementation completes the lithification process. Burial cementation does not produce stylolites. When overlying beds are eroded, bringing limestone closer to the surface, the final stage of diagenesis takes place. This produces secondary porosity as some of the cement is dissolved by rainwater infiltrating
765-519: A diameter of 12 μm. The fiber of cashmere goats is 14 to 19 μm, while angora rabbit is 8 to 12 μm, and that of shahtoosh from the Tibetan antelope , or chiru, is from 9 to 12 μm. Vicugna Vicugna Lama is a genus containing the South American camelids : the wild guanaco and vicuña and the domesticated llama , alpaca , and the extinct chilihueque . Before
850-483: A drop of dilute hydrochloric acid is dropped on it. Dolomite is also soft but reacts only feebly with dilute hydrochloric acid, and it usually weathers to a characteristic dull yellow-brown color due to the presence of ferrous iron. This is released and oxidized as the dolomite weathers. Impurities (such as clay , sand, organic remains, iron oxide , and other materials) will cause limestones to exhibit different colors, especially with weathered surfaces. The makeup of
935-621: A few million years, as this is the most stable form of calcium carbonate. Ancient carbonate formations of the Precambrian and Paleozoic contain abundant dolomite, but limestone dominates the carbonate beds of the Mesozoic and Cenozoic . Modern dolomite is quite rare. There is evidence that, while the modern ocean favors precipitation of aragonite, the oceans of the Paleozoic and middle to late Cenozoic favored precipitation of calcite. This may indicate
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#17330852470281020-455: A few thousand years. As rainwater mixes with groundwater, aragonite and high-magnesium calcite are converted to low-calcium calcite. Cementing of thick carbonate deposits by rainwater may commence even before the retreat of the sea, as rainwater can infiltrate over 100 km (60 miles) into sediments beneath the continental shelf. As carbonate sediments are increasingly deeply buried under younger sediments, chemical and mechanical compaction of
1105-490: A high percentage of the mineral dolomite , CaMg(CO 3 ) 2 . Magnesian limestone is an obsolete and poorly-defined term used variously for dolomite, for limestone containing significant dolomite ( dolomitic limestone ), or for any other limestone containing a significant percentage of magnesium . Most limestone was formed in shallow marine environments, such as continental shelves or platforms , though smaller amounts were formed in many other environments. Much dolomite
1190-435: A limestone sample except in thin section and are less common in ancient limestones, possibly because compaction of carbonate sediments disrupts them. Limeclasts are fragments of existing limestone or partially lithified carbonate sediments. Intraclasts are limeclasts that originate close to where they are deposited in limestone, while extraclasts come from outside the depositional area. Intraclasts include grapestone , which
1275-466: A lower Mg/Ca ratio in the ocean water of those times. This magnesium depletion may be a consequence of more rapid sea floor spreading , which removes magnesium from ocean water. The modern ocean and the ocean of the Mesozoic have been described as "aragonite seas". Most limestone was formed in shallow marine environments, such as continental shelves or platforms . Such environments form only about 5% of
1360-525: A lower diversity of organisms and a greater fraction of silica and clay minerals characteristic of marls . The Green River Formation is an example of a prominent freshwater sedimentary formation containing numerous limestone beds. Freshwater limestone is typically micritic. Fossils of charophyte (stonewort), a form of freshwater green algae, are characteristic of these environments, where the charophytes produce and trap carbonates. Limestones may also form in evaporite depositional environments . Calcite
1445-523: A mechanism for dolomitization, with one 2004 review paper describing it bluntly as "a myth". Ordinary seawater is capable of converting calcite to dolomite, if the seawater is regularly flushed through the rock, as by the ebb and flow of tides (tidal pumping). Once dolomitization begins, it proceeds rapidly, so that there is very little carbonate rock containing mixed calcite and dolomite. Carbonate rock tends to be either almost all calcite/aragonite or almost all dolomite. About 20% to 25% of sedimentary rock
1530-448: A plausible source of mud. Another possibility is direct precipitation from the water. A phenomenon known as whitings occurs in shallow waters, in which white streaks containing dispersed micrite appear on the surface of the water. It is uncertain whether this is freshly precipitated aragonite or simply material stirred up from the bottom, but there is some evidence that whitings are caused by biological precipitation of aragonite as part of
1615-449: A radial rather than layered internal structure, indicating that they were formed by algae in a normal marine environment. Peloids are structureless grains of microcrystalline carbonate likely produced by a variety of processes. Many are thought to be fecal pellets produced by marine organisms. Others may be produced by endolithic (boring) algae or other microorganisms or through breakdown of mollusc shells. They are difficult to see in
1700-413: A sheep. The llama and alpaca are only known in the domestic state, and are variable in size and color, being often white, black, or piebald. The wild guanaco and vicuña are of a nearly uniform light-brown color, passing into white below. The vicuña and guanaco share an obvious family resemblance and may be difficult to tell apart at a distance. The vicuña is smaller and slenderer in its proportions, and has
1785-529: A shorter head than the guanaco. The guanaco has an extensive geographical range, from the high lands of the Andean region of Ecuador and Peru to the open plains of Patagonia , and even the wooded islands of Tierra del Fuego . It constituted the principal food of the Patagonian Indians, and they use its skin for the material from which their long robes are made. It is about the size of a European red deer , and
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#17330852470281870-560: Is also favored on the seaward margin of shelves and platforms, where there is upwelling deep ocean water rich in nutrients that increase organic productivity. Reefs are common here, but when lacking, ooid shoals are found instead. Finer sediments are deposited close to shore. The lack of deep sea limestones is due in part to rapid subduction of oceanic crust, but is more a result of dissolution of calcium carbonate at depth. The solubility of calcium carbonate increases with pressure and even more with higher concentrations of carbon dioxide, which
1955-669: Is an elegant animal with a long, slender, gracefully curved neck and slim legs. The vicuña ranges throughout the Western Andes. Limestone Limestone ( calcium carbonate CaCO 3 ) 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 CaCO 3 . 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
2040-482: Is an uncommon mineral in limestone, and siderite or other carbonate minerals are rare. However, the calcite in limestone often contains a few percent of magnesium . Calcite in limestone is divided into low-magnesium and high-magnesium calcite, with the dividing line placed at a composition of 4% magnesium. High-magnesium calcite retains the calcite mineral structure, which is distinct from dolomite. Aragonite does not usually contain significant magnesium. Most limestone
2125-402: Is carbonate rock, and most of this is limestone. Limestone is found in sedimentary sequences as old as 2.7 billion years. However, the compositions of carbonate rocks show an uneven distribution in time in the geologic record. About 95% of modern carbonates are composed of high-magnesium calcite and aragonite. The aragonite needles in carbonate mud are converted to low-magnesium calcite within
2210-474: Is clusters of peloids cemented together by organic material or mineral cement. Extraclasts are uncommon, are usually accompanied by other clastic sediments, and indicate deposition in a tectonically active area or as part of a turbidity current . The grains of most limestones are embedded in a matrix of carbonate mud. This is typically the largest fraction of an ancient carbonate rock. Mud consisting of individual crystals less than 5 μm (0.20 mils) in length
2295-416: Is commonly white to gray in color. Limestone that is unusually rich in organic matter can be almost black in color, while traces of iron or manganese can give limestone an off-white to yellow to red color. The density of limestone depends on its porosity, which varies from 0.1% for the densest limestone to 40% for chalk. The density correspondingly ranges from 1.5 to 2.7 g/cm . Although relatively soft, with
2380-420: Is controlled largely by the amount of dissolved carbon dioxide ( CO 2 ) in the water. This is summarized in the reaction: Increases in temperature or decreases in pressure tend to reduce the amount of dissolved CO 2 and precipitate CaCO 3 . Reduction in salinity also reduces the solubility of CaCO 3 , by several orders of magnitude for fresh water versus seawater. Near-surface water of
2465-545: Is converted to low-magnesium calcite. Diagenesis is the likely origin of pisoliths , concentrically layered particles ranging from 1 to 10 mm (0.039 to 0.394 inches) in diameter found in some limestones. Pisoliths superficially resemble ooids but have no nucleus of foreign matter, fit together tightly, and show other signs that they formed after the original deposition of the sediments. Silicification occurs early in diagenesis, at low pH and temperature, and contributes to fossil preservation. Silicification takes place through
2550-503: Is deposited close to where it formed, classification of limestone is usually based on its grain type and mud content. Most grains in limestone are skeletal fragments of marine organisms such as coral or foraminifera . These organisms secrete structures made of aragonite or calcite, and leave these structures behind when they die. Other carbonate grains composing limestones are ooids , peloids , and limeclasts ( intraclasts and extraclasts [ ca ] ). Skeletal grains have
2635-460: Is described as coquinite . Chalk is a soft, earthy, fine-textured limestone composed of the tests of planktonic microorganisms such as foraminifera, while marl is an earthy mixture of carbonates and silicate sediments. Limestone forms when calcite or aragonite precipitate out of water containing dissolved calcium, which can take place through both biological and nonbiological processes. The solubility of calcium carbonate ( CaCO 3 )
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2720-617: Is described as micrite . In fresh carbonate mud, micrite is mostly small aragonite needles, which may precipitate directly from seawater, be secreted by algae, or be produced by abrasion of carbonate grains in a high-energy environment. This is converted to calcite within a few million years of deposition. Further recrystallization of micrite produces microspar , with grains from 5 to 15 μm (0.20 to 0.59 mils) in diameter. Limestone often contains larger crystals of calcite, ranging in size from 0.02 to 0.1 mm (0.79 to 3.94 mils), that are described as sparry calcite or sparite . Sparite
2805-462: Is distinguished from micrite by a grain size of over 20 μm (0.79 mils) and because sparite stands out under a hand lens or in thin section as white or transparent crystals. Sparite is distinguished from carbonate grains by its lack of internal structure and its characteristic crystal shapes. Geologists are careful to distinguish between sparite deposited as cement and sparite formed by recrystallization of micrite or carbonate grains. Sparite cement
2890-448: Is from 75 to 85 cm (around 3 ft); its weight is from 35 to 65 kg (under 150 lb). It falls prey to the cougar and culpeo . There are two subspecies of vicuña: While vicuñas are restricted to the more extreme elevations of the Andes in modern times, they may have also been present in the lowland regions of Patagonia as much as 3500 km south of their current range during
2975-560: Is one of the first minerals to precipitate in marine evaporites. Most limestone is formed by the activities of living organisms near reefs, but the organisms responsible for reef formation have changed over geologic time. For example, stromatolites are mound-shaped structures in ancient limestones, interpreted as colonies of cyanobacteria that accumulated carbonate sediments, but stromatolites are rare in younger limestones. Organisms precipitate limestone both directly as part of their skeletons, and indirectly by removing carbon dioxide from
3060-473: Is otherwise chemically fairly pure, with clastic sediments (mainly fine-grained quartz and clay minerals ) making up less than 5% to 10% of the composition. Organic matter typically makes up around 0.2% of a limestone and rarely exceeds 1%. Limestone often contains variable amounts of silica in the form of chert or siliceous skeletal fragments (such as sponge spicules, diatoms , or radiolarians ). Fossils are also common in limestone. Limestone
3145-472: Is produced by decaying organic matter settling into the deep ocean that is not removed by photosynthesis in the dark depths. As a result, there is a fairly sharp transition from water saturated with calcium carbonate to water unsaturated with calcium carbonate, the lysocline , which occurs at the calcite compensation depth of 4,000 to 7,000 m (13,000 to 23,000 feet). Below this depth, foraminifera tests and other skeletal particles rapidly dissolve, and
3230-514: Is secondary dolomite, formed by chemical alteration of limestone. Limestone is exposed over large regions of the Earth's surface, and because limestone is slightly soluble in rainwater, these exposures often are eroded to become karst landscapes. Most cave systems are found in limestone bedrock. Limestone has numerous uses: as a chemical feedstock for the production of lime used for cement (an essential component of concrete ), as aggregate for
3315-473: Is very expensive because the animal can only be shorn every three years and has to be caught from the wild. When knitted together, the product of the vicuña's wool is very soft and warm. The Inca valued vicuñas highly for their wool, and it was against the law for anyone but royalty to wear vicuña garments; today, the vicuña is the national animal of Peru and appears on the Peruvian coat of arms . Both under
3400-560: The IUCN still supports active conservation programs to protect vicuñas, though they lowered their status to least concern in 2018. In 2015, French luxury group LVMH said that " Loro Piana saved the species." The Italian company has been criticized for underpaying local communities collecting the wool. In 2022, the Argentine government's National Council for Scientific and Technical Investigation estimated that "Andean communities receive around 3% of
3485-644: The Late Pleistocene and Early Holocene . Fossils of these lowland camelids have been assigned to a species known as Lama gracilis , but genetic and morphological analysis between them and modern vicuña indicate the two may be the same. Vicuñas are native to South America's central Andes . They are found in Peru , northwestern Argentina , Bolivia , and northern Chile . A smaller, introduced population lives in central Ecuador . Vicuñas live at altitudes of 3,200 to 4,800 m (10,500–15,700 ft). They feed in
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3570-498: The Spanish conquest of the Americas , llamas, alpacas, and chilihueques were the only domesticated ungulates of the continent . They were kept not only for their value as beasts of burden, but also for their flesh, hides, and wool . Although they were often compared to sheep by early writers, their affinity to the camel was soon perceived. They were included in the genus Camelus in
3655-718: The Suina or pigs , the Tragulina or chevrotains , and the Pecora or true ruminants , to each of which the Tylopoda have some affinity, standing in some respects in a central position between them, sharing some characters from each, but showing special modifications not found in any of the others. Discovery of the extinct fauna of the American continent of the Paleogene and Neogene periods, starting with
3740-738: The Systema Naturae of Linnaeus . In 1800, Cuvier moved the llama, alpaca, and guanaco to the genus Lama , and the vicuña to the genus Vicugna . Later, the alpaca was transferred to Vicugna ; both were eventually returned to Lama by the American Society of Mammalogists in 2021, the return of the Vicunga genus however is not supported by all, for example the Royal Society maintaining their separate classification (Vicunga pogo and Vicunga vicunga) in multiply mentioned references before and after
3825-464: The culpeo . The behavior of vicuñas is similar to that of the guanacos. They are timid animals and are easily aroused by intruders due, among other things, to their extraordinary hearing. Like the guanacos, they frequently lick calcareous stones and rocks, which, together with salt water, is its source of salt. Vicuñas are clean animals and always deposit their excrement in the same place. Their diets consist mainly of low grasses which grow in clumps on
3910-424: The guanaco and smaller. A key distinguishing element of morphology is the better-developed incisor roots for the guanaco. The vicuña's long, woolly coat is tawny brown on the back, whereas the hair on the throat and chest is white and quite long. Its head is slightly shorter than guanaco's, and the ears are slightly longer. The length of the head and body ranges from 1.45 to 1.60 m (about 5 ft); shoulder height
3995-646: The 19th-century paleontologists Leidy , Cope , and Marsh , has revealed the early history of this family. Llamas were not always confined to South America; their remains are abundant in the Pleistocene deposits of the Rocky Mountains region, and in Central America ; some of these extinct forms were much larger than any now living. None of these transitional forms has been found in Old World strata; North America
4080-622: The Convention for the Conservation and Management of the Vicuña, was signed between Bolivia, Chile, Ecuador and Peru on 20 December 1979 in Lima . It explicitly allowed only Argentina to sign it if it also signed the 1969 La Paz Convention (Article 12; Argentina joined in 1981), and did not allow other countries to accede to the convention 'due to its specific character' (Article 13). The 1979 Convention did allow
4165-496: The Earth's history. Limestone may have been deposited by microorganisms in the Precambrian , prior to 540 million years ago, but inorganic processes were probably more important and likely took place in an ocean more highly oversaturated in calcium carbonate than the modern ocean. Diagenesis is the process in which sediments are compacted and turned into solid rock . During diagenesis of carbonate sediments, significant chemical and textural changes take place. For example, aragonite
4250-565: The New World llamas became restricted to South America following the peopling of the Americas by Paleo-Indians and the accompanying extinction of the megafauna . A possible variety is the hueque or chilihueque that existed in central and south-central Chile in pre-Hispanic and early colonial times. Two main hypotheses on their status among South American camelids are given: the first one suggests they are locally domesticated guanacos and
4335-707: The US Peace Corps, Nature Conservancy, World Wildlife Fund, and the National Agrarian University of La Molina established a nature conservatory for the vicuña called the Pampa Galeras – Barbara D'Achille in Lucanas Province , Ayacucho . During that time, a game warden academy was held in Nazca, where eight men from Peru and six from Bolivia were trained to protect the vicuña from poaching. To cooperate on
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#17330852470284420-430: 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. About 20% to 25% of sedimentary rock is carbonate rock, and most of this is limestone. The remaining carbonate rock is mostly dolomite , a closely related rock, which contains
4505-434: The base of roads, as white pigment or filler in products such as toothpaste or paint, as a soil conditioner , and as a popular decorative addition to rock gardens . Limestone formations contain about 30% of the world's petroleum reservoirs . Limestone is composed mostly of the minerals calcite and aragonite , which are different crystal forms of calcium carbonate ( CaCO 3 ). Dolomite , CaMg(CO 3 ) 2 ,
4590-657: The beds. This may include the formation of vugs , which are crystal-lined cavities within the limestone. Diagenesis may include conversion of limestone to dolomite by magnesium-rich fluids. There is considerable evidence of replacement of limestone by dolomite, including sharp replacement boundaries that cut across bedding. The process of dolomitization remains an area of active research, but possible mechanisms include exposure to concentrated brines in hot environments ( evaporative reflux ) or exposure to diluted seawater in delta or estuary environments ( Dorag dolomitization ). However, Dorag dolomitization has fallen into disfavor as
4675-602: The community of Lucanas conducts a chaccu (herding, capturing, and shearing) on the reserve each year to harvest the wool, organized by the National Council for South American Camelids (CONACS). In Bolivia, the Ulla Ulla National Reserve was founded 1977 partly as a sanctuary for the species. Their numbers grew to 125,000 in Peru, Chile, Argentina, and Bolivia. Since this was a ready "cash crop" for community members,
4760-476: The conservation of the vicuña, the governments of Bolivia and Peru signed the Convention for the Conservation of the Vicuña on 16 August 1969 in La Paz , explicitly leaving the treaty open to accession by Argentina and Chile. Ecuador acceded on 11 February 1976. The Convention prohibited their international trade and domestic exploitation, and ordered the parties to create reserves and breeding centres. A follow-up treaty,
4845-488: The countries relaxed regulations on vicuña wool in 1993, enabling its trade once again. The wool is sold on the world market for over $ 300 per kg. In 2002, the US Fish and Wildlife Service reclassified most populations as threatened, but still lists Ecuador's population as endangered. While the population levels have recovered to a healthy level, poaching remains a constant threat, as do habitat loss and other threats. Consequently,
4930-566: The daytime on the grassy plains of the Andes Mountains but spend the nights on the slopes. In these areas, only nutrient-poor, tough, bunch grasses and Festuca grow. The sun's rays can penetrate the thin atmosphere , producing relatively warm temperatures during the day; however, the temperatures drop to freezing at night. The vicuña's thick but soft coat is a unique adaptation that traps layers of warm air close to its body to tolerate freezing temperatures. Chief predators include pumas and
5015-462: The depositional fabric of carbonate rocks. Dunham divides the rocks into four main groups based on relative proportions of coarser clastic particles, based on criteria such as whether the grains were originally in mutual contact, and therefore self-supporting, or whether the rock is characterized by the presence of frame builders and algal mats. Unlike the Folk scheme, Dunham deals with the original porosity of
5100-469: The deposits are highly porous, so that they have a spongelike texture, they are typically described as tufa . Secondary calcite deposited by supersaturated meteoric waters ( groundwater ) in caves is also sometimes described as travertine. This produces speleothems , such as stalagmites and stalactites . Coquina is a poorly consolidated limestone composed of abraded pieces of coral , shells , or other fossil debris. When better consolidated, it
5185-406: The earth's oceans are oversaturated with CaCO 3 by a factor of more than six. The failure of CaCO 3 to rapidly precipitate out of these waters is likely due to interference by dissolved magnesium ions with nucleation of calcite crystals, the necessary first step in precipitation. Precipitation of aragonite may be suppressed by the presence of naturally occurring organic phosphates in
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#17330852470285270-399: The first refers to the grains and the second to the cement. For example, a limestone consisting mainly of ooids, with a crystalline matrix, would be termed an oosparite. It is helpful to have a petrographic microscope when using the Folk scheme, because it is easier to determine the components present in each sample. Robert J. Dunham published his system for limestone in 1962. It focuses on
5355-572: The formation of distinctive minerals from the silica and clay present in the original limestone. Two major classification schemes, the Folk and Dunham, are used for identifying the types of carbonate rocks collectively known as limestone. Robert L. Folk developed a classification system that places primary emphasis on the detailed composition of grains and interstitial material in carbonate rocks . Based on composition, there are three main components: allochems (grains), matrix (mostly micrite), and cement (sparite). The Folk system uses two-part names;
5440-429: The geologic record are called bioherms . Many are rich in fossils, but most lack any connected organic framework like that seen in modern reefs. The fossil remains are present as separate fragments embedded in ample mud matrix. Much of the sedimentation shows indications of occurring in the intertidal or supratidal zones, suggesting sediments rapidly fill available accommodation space in the shelf or platform. Deposition
5525-527: The ground. Vicuñas live in family-based groups of a male, 5 to 15 females, and their young. Each group has its territory of about 18 km (6.9 sq mi), which can fluctuate depending on food availability. Mating usually occurs in March–April. After a gestation about 11 months, the female gives birth to a single fawn, which is nursed for about ten months. The fawn becomes independent at about 12 to 18 months old. Young males form bachelor groups, and
5610-451: The lower jaw, the three incisors are long, spatulate, and procumbent; the outer ones are the smallest. Next to these is a curved, suberect canine, followed after an interval by an isolated minute and often deciduous simple conical premolar; then a contiguous series of one premolar and three molars, which differ from those of Camelus in having a small accessory column at the anterior outer edge. The skull generally resembles that of Camelus ,
5695-410: The ocean basins, but limestone is rarely preserved in continental slope and deep sea environments. The best environments for deposition are warm waters, which have both a high organic productivity and increased saturation of calcium carbonate due to lower concentrations of dissolved carbon dioxide. Modern limestone deposits are almost always in areas with very little silica-rich sedimentation, reflected in
5780-463: The position taken by the American Society of Mammalogists . These New World camelids alongside camels , are the sole extant representatives of a distinct section of Artiodactyla (even-toed ungulates) called Tylopoda , or "hump-footed", from the peculiar bumps on the soles of their feet. This section consists of a single family, the Camelidae , the other sections of the same great division being
5865-426: The reaction: Fossils are often preserved in exquisite detail as chert. Cementing takes place rapidly in carbonate sediments, typically within less than a million years of deposition. Some cementing occurs while the sediments are still under water, forming hardgrounds . Cementing accelerates after the retreat of the sea from the depositional environment, as rainwater infiltrates the sediment beds, often within just
5950-482: The relative purity of most limestones. Reef organisms are destroyed by muddy, brackish river water, and carbonate grains are ground down by much harder silicate grains. Unlike clastic sedimentary rock, limestone is produced almost entirely from sediments originating at or near the place of deposition. Limestone formations tend to show abrupt changes in thickness. Large moundlike features in a limestone formation are interpreted as ancient reefs , which when they appear in
6035-427: The relatively larger brain cavity and orbits and less developed cranial ridges being due to its smaller size. The nasal bones are shorter and broader, and are joined by the premaxilla . Ears are rather long and pointed. No dorsal hump is present. Feet are narrow, the toes being more separated than in the camels, each having a distinct plantar pad. The tail is short, and the fur is long and ruffled looking like that of
6120-460: The rock. The Dunham scheme is more useful for hand samples because it is based on texture, not the grains in the sample. A revised classification was proposed by Wright (1992). It adds some diagenetic patterns to the classification scheme. Travertine is a term applied to calcium carbonate deposits formed in freshwater environments, particularly waterfalls , cascades and hot springs . Such deposits are typically massive, dense, and banded. When
6205-538: The rule of the Inca and today, vicuñas have been protected by law, but they were heavily hunted in the intervening period. When they were declared endangered in 1974, only about 6,000 animals were left. Today, the vicuña population has recovered to about 350,000, and although conservation organizations have reduced its level of threat classification, they still call for active conservation programs to protect populations from poaching, habitat loss , and other threats. Previously,
6290-759: The second suggests they are a variety of llamas brought from the north into south-central Chile. Chilihueques became extinct in the 16th or 17th century, being replaced by European livestock. The causes of its extinction are unknown. According to Juan Ignacio Molina , the Dutch captain Joris van Spilbergen observed the use of chilihueques by native Mapuches of Mocha Island as plough animals in 1614. [REDACTED] [REDACTED] [REDACTED] [REDACTED] [REDACTED] These characters apply especially to llamas. Dentition of adults:-incisors 1/3 canines 1/1, premolars 2/2, molars 3/2; total 32. In
6375-479: The sediments increases. Chemical compaction takes place by pressure solution of the sediments. This process dissolves minerals from points of contact between grains and redeposits it in pore space, reducing the porosity of the limestone from an initial high value of 40% to 80% to less than 10%. Pressure solution produces distinctive stylolites , irregular surfaces within the limestone at which silica-rich sediments accumulate. These may reflect dissolution and loss of
6460-662: The sediments of the ocean floor abruptly transition from carbonate ooze rich in foraminifera and coccolith remains ( Globigerina ooze) to silicic mud lacking carbonates. In rare cases, turbidites or other silica-rich sediments bury and preserve benthic (deep ocean) carbonate deposits. Ancient benthic limestones are microcrystalline and are identified by their tectonic setting. Fossils typically are foraminifera and coccoliths. No pre-Jurassic benthic limestones are known, probably because carbonate-shelled plankton had not yet evolved. Limestones also form in freshwater environments. These limestones are not unlike marine limestone, but have
6545-530: The upper jaw is a compressed, sharp, pointed laniariform incisor near the hinder edge of the premaxilla , followed in the male at least by a moderate-sized, pointed, curved true canine tooth canine in the anterior part of the maxilla. The isolated canine-like premolar which follows in the camels is not present. The teeth of the molar series which are in contact with each other consist of two very small premolars (the first almost rudimentary) and three broad molars , constructed generally like those of Camelus . In
6630-464: The use of the vicuña under strict circumstances if the animal population had recovered sufficiently. In combination with CITES (effective in 1975), as well as USA and EU trade legislation, the Conventions were highly successful, as the vicuña population substantially grew as a result. The estimated population in Peru was 66,559 in 1994, 103,161 in 1997, 118,678 in 2000, and 208,899 in 2012. Currently,
6715-406: The value generated by the vicuña fiber chain." Its wool is famous for its warmth and is used for apparel, such as socks, sweaters, accessories, shawls, coats, suits, and home furnishings, such as blankets and throws. Its properties come from the tiny scales on the hollow, air-filled fibres, which causes them to interlock and trap insulating air. Vicuñas have some of the finest fibers in the world, at
6800-430: The vicuña was not considered domesticated, and the llama and the alpaca were regarded as descendants of the closely related guanaco . However, DNA research published in 2001 has demonstrated that the alpaca may have vicuña parentage. Today, the vicuña is mainly wild, but the local people still perform special rituals with these creatures, including a fertility rite. The vicuña is considered more delicate and gracile than
6885-533: The water by photosynthesis and thereby decreasing the solubility of calcium carbonate. Limestone shows the same range of sedimentary structures found in other sedimentary rocks. However, finer structures, such as lamination , are often destroyed by the burrowing activities of organisms ( bioturbation ). Fine lamination is characteristic of limestone formed in playa lakes , which lack the burrowing organisms. Limestones also show distinctive features such as geopetal structures , which form when curved shells settle to
6970-553: The water. Although ooids likely form through purely inorganic processes, the bulk of CaCO 3 precipitation in the oceans is the result of biological activity. Much of this takes place on carbonate platforms . The origin of carbonate mud, and the processes by which it is converted to micrite, continue to be a subject of research. Modern carbonate mud is composed mostly of aragonite needles around 5 μm (0.20 mils) in length. Needles of this shape and composition are produced by calcareous algae such as Penicillus , making this
7055-459: The young females search for a sorority to join. This deters intraspecific competition and inbreeding. Until 1964, hunting of the vicuña was unrestricted, which reduced its numbers to only 6,000 in the 1960s. As a result, the species was declared endangered in 1974, and its status prohibited the trade of vicuña wool. In Peru, during 1964–1966, the Servicio Forestal y de Caza in cooperation with
7140-416: Was likely deposited in pore space between grains, suggesting a high-energy depositional environment that removed carbonate mud. Recrystallized sparite is not diagnostic of depositional environment. Limestone outcrops are recognized in the field by their softness (calcite and aragonite both have a Mohs hardness of less than 4, well below common silicate minerals) and because limestone bubbles vigorously when
7225-680: Was the original home of the Camelidae family. The ancestor of modern camels crossed Beringia into Eurasia and Africa about 7 million years ago. The ancestor of the modern llamas entered South America via the Isthmus of Panama about 3 million years ago, as part of the Great American Interchange . The Old World camels were gradually driven southward into regions of Asia and Africa, perhaps by changes of climate , and having become isolated, they have undergone further special modifications. Meanwhile,
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