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91-400: Adam's Bridge , also known as Rama's Bridge or Rama Setu , is a chain of natural limestone shoals between Pamban Island , also known as Rameswaram Island, off the southeastern coast of Tamil Nadu , India , and Mannar Island , off the northwestern coast of Sri Lanka . Geological evidence suggests that the bridge was formerly a land connection between India and Sri Lanka. The feature

182-455: 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

273-463: 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

364-529: A sic' , emerged in 1889, E. Belfort Bax 's work in The Ethics of Socialism being an early example. On occasion, sic has been misidentified as an acronym (and therefore sometimes misspelled with periods): s.i.c. is said to stand for "spelled/said in copy/context", "spelling is correct", "spelled incorrectly", and other such folk etymology phrases. These are all incorrect and are simply backronyms from sic . Use of sic greatly increased in

455-472: A bridge constructed by the god Rama to reach the island Lanka and rescue his wife Sita from Ravana . In popular belief, Lanka is equated to present-day Sri Lanka and the bridge is described as "Rama's Setu". Due to lowered sea levels during the Last Glacial Period (115,000–11,700 years Before Present ) where sea levels reached a maximum of 120 m (390 ft) below present values,

546-434: 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

637-616: 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

728-449: 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

819-949: 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

910-412: 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

1001-483: 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

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1092-637: 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

1183-455: 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

1274-490: 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

1365-509: A land connection bridged this in the past, and some Ramanathaswamy Temple records suggest that violent storms broke the link in 1480. Cotton suggested that the channel could be dredged to enable passage of ships, but nothing was done until 1828, when Major Sim directed the blasting and removal of some rocks. A more detailed marine survey of Adam's Bridge was undertaken in 1837 by lieutenants F. T. Powell, Ethersey, Grieve, and Christopher, along with draughtsman Felix Jones, and operations to dredge

1456-435: 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

1547-471: 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

1638-525: 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

1729-523: 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

1820-441: A parenthetical sentence only when used after a complete sentence, like so: ( Sic. ) Some guides, including The Chicago Manual of Style , recommend "quiet copy-editing " (unless where inappropriate or uncertain) instead of inserting a bracketed sic , such as by substituting in brackets the correct word in place of the incorrect word or by simply replacing an incorrect spelling with the correct one. Alternatively, to show both

1911-448: 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

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2002-449: 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

2093-732: A sacred symbol to be appropriated for political purposes strengthened in the aftermath of protests against the Sethusamudram Shipping Canal Project . 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

2184-514: Is 48 km (30 mi) long and separates the Gulf of Mannar (southwest) from the Palk Strait (northeast). Some regions of the bridge are dry, and the sea in the area rarely exceeds 1 metre (3 ft) in depth, making it quite difficult for boats to pass over it. Ibn Khordadbeh 's Kitāb al-Masālik wa-l-Mamālik ( c.  850 ) refers to the structure as Set Bandhai (lit. Bridge of

2275-687: Is a proposed road and rail sea bridge and tunnel that would cross the Palk Strait roughly over, or parallel to, Adam's Bridge. It would span from Dhanushkodi at the tip of Pamban Island in India, to Talaimannar on Mannar Island in Sri Lanka, and would be used for both industrial/economic purposes and to boost tourism. The bridge was first seriously proposed by the Indian and Sri Lankan governments in 2002, shelved after security-related objections by

2366-560: 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

2457-482: 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

2548-402: 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

2639-474: 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

2730-416: 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

2821-420: 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

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2912-545: 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

3003-503: 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

3094-460: 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 )

3185-617: 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

3276-462: 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

3367-778: Is equated to present-day Sri Lanka. However, such a correspondence is not explicit in the Ramayana and a few verses can even be held to be against such an identification; some Sanskrit sources of the first millennium emphasise on the distinction. Robert P. Goldman — who edited the Princeton translation of the epic into English — characterises most of the Ramayana, including the Lanka Kanda , as "kind of [an] elaborate fairy tale" by design ; attempts to probe into its historicity were misguided. John Brockington, noted for his scholarship on Hindu epics, concurs. In extant historical sources,

3458-409: Is insufficient evidence to indicate eustatic emergence and that the raised reef in southern India probably results from a local uplift. In the vicinity of Adam's Bridge/Rama Setu, the water is typically only 1–3 m (3 ft 3 in – 9 ft 10 in) deep. Due to the shallow waters, Adam's Bridge presents a formidable hindrance to navigation through the Palk Strait. Though trade across

3549-403: Is most often inserted into quoted or reprinted material to indicate meticulous accuracy in reproducing the preceding text, despite appearances to the reader of an incorrect or unusual orthography ( spelling , punctuation , grammar, syntax, fact, logic, etc.). Several usage guides recommend that a bracketed sic be used primarily as an aid to the reader, not as an indicator of disagreement with

3640-560: 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

3731-473: 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

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3822-472: 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

3913-518: 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

4004-628: Is that Adam's Bridge is identified popularly as the causeway described in the Ramayana . The political parties and organisations suggest alternate alignment for the channel that avoids damage to Adam's Bridge. The then state and central governments opposed such changes, with the Union Shipping Minister T. R Baalu, who belongs to the Dravida Munnetra Kazhagam and a strong supporter of the project maintaining that

4095-426: Is to inform the reader that any errors in a quotation did not arise from editorial errors in the transcription, but are intentionally reproduced as they appear in the source text being quoted; thus, sic is placed inside brackets to indicate it is not part of the quotation. Sic can also be used derisively to direct the reader's attention to the writer's spelling mistakes and erroneous logic, or to show disapproval of

4186-603: The Archaeological Survey of India found no evidence for the structure being anything but a natural formation. The Archaeological Survey of India and the government of India informed the Supreme Court of India in a 2007 affidavit that there was no historical proof of the bridge being built by Rama. In 2017 the Indian Council of Historical Research (ICHR) announced a pilot study into the origins of

4277-496: 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

4368-482: The India–Sri Lanka divide has been active since at least the first millennium BC, it was limited to small boats and dinghies. Larger ocean-going vessels from the west have had to navigate around Sri Lanka to reach India's eastern coast. Eminent British geographer Major James Rennell , who surveyed the region as a young officer in the late 18th century, suggested that a "navigable passage could be maintained by dredging

4459-598: The Sea). The name Adam's Bridge appeared probably around the time of Al-Biruni ( c.  1030 ). This appears to have been premised on the Islamic belief that Adam's Peak — where the biblical Adam fell to earth — is located in Sri Lanka, and that Adam crossed over to peninsular India via the bridge after his expulsion from the Garden of Eden . The ancient Sanskrit epic Ramayana (8th century BCE–3rd century CE) mentions

4550-509: The Union government to use land passages instead of cutting Adam's Bridge because of the several advantages of land passage. In 2005, the government of India approved a multi-million dollar Sethusamudram Shipping Canal Project . This project aims to create a ship channel across the Palk Strait by dredging the shallow ocean floor near Dhanushkodi . The channel is expected to cut over 400 km (250 mi) (nearly 30 hours of shipping time) off

4641-430: 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

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4732-434: 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 ,

4823-657: 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

4914-531: The bottom with the concave face downwards. This traps a void space that can later be filled by sparite. Geologists use geopetal structures to determine which direction was up at the time of deposition, which is not always obvious with highly deformed limestone formations. The cyanobacterium Hyella balani can bore through limestone; as can the green alga Eugamantia sacculata and the fungus Ostracolaba implexa . Sic We are prepared, under appropriate circumstances, to provide information bearing on

5005-560: The channel were recommenced the next year. However, these and subsequent efforts in the 19th century did not succeed in keeping the passage navigable for any vessels except those with a light draft. The government of India constituted nine committees before independence, and five committees since then, to suggest alignments for a Sethusamudram canal project. Most of them suggested land-based passages across Rameswaram island, and none recommended alignment across Adam's Bridge. The Sethusamudram project committee in 1956 also strongly recommended to

5096-680: The content or form of the material. In the English language, the Latin adverb sic is used as an adverb, and derivatively as a noun and as a verb. The adverb sic , meaning 'intentionally so written', first appeared in English c.  1856 . It is derived from the Latin adverb sīc , which means 'so', 'thus', 'in this manner'. According to the Oxford English Dictionary , the verbal form of sic , meaning 'to mark with

5187-618: The credibly [ sic ] and veracity of any such source. Irin Carmon quoting a law firm The Latin adverb sic ( / s ɪ k / ; thus , so , and in this manner ) inserted after a quotation indicates that the quoted matter has been transcribed or translated as found in the source text, including erroneous, archaic, or unusual spelling, punctuation , and grammar . Sic also applies to any surprising assertion, faulty reasoning, or other matter that might be interpreted as an error of transcription . The typical editorial usage of Sic

5278-541: The current proposal was economically viable and environmentally sustainable and that there were no other alternatives. Opposition to dredging through this causeway also stems from concerns over its impact on the area's ecology and marine wealth, potential loss of thorium deposits in the area and increased risk of damage due to tsunamis . Some organisations oppose this project on economic and environmental grounds and claim that proper scientific studies were not conducted before undertaking this project. The Palk Strait Bridge

5369-466: 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

5460-469: 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

5551-406: 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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5642-503: The entirety of the relatively shallow Palk Strait (which reaches a maximum depth of only 35 m (115 ft)) was exposed as dry land connecting the mainland Indian subcontinent and Sri Lanka. Following the rise to present sea levels during the Holocene , by around 7,000 years ago, the strait became submerged, including the region of Adam's Bridge/Rama Setu. The islands of Adam's Bridge became emergent again following sea level falls in

5733-598: The equation between the two islands appears for the first time only in the Kasakudi Copper Plates of Nandivarman II (r. late-8th century) pertaining to the conquest of Sri Lanka by one of his ancestors; as Ramayana took a life of its own under the succeeding Cholas, the identification profferred, justifying their imperial ambitions to invade the island. The link would then be co-opted by the Aryacakravarti dynasty of Jaffna in presenting themselves as

5824-399: 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

5915-499: The following example from Fred Rodell 's 1955 book Nine Men : [I]n 1951, it was the blessing bestowed on Judge Harold Medina 's prosecution [ sic ] of the eleven so-called 'top native Communists,' which blessing meant giving the Smith Act the judicial nod of constitutionality. Where sic follows the quotation, it takes brackets : [ sic ]. The word sic is often treated as a loanword that does not require italics, and

6006-572: 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;

6097-429: 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

6188-418: The guardians of the bridge. Nonetheless, two reputed medieval commentaries on the Ramayana — Ramanujiya (drafted c. 1500 by Ramanuja) and Tattvadipika (drafted c. 1550 by Mahesvaratirtha) — continued to make a distinction between Lanka and Sri Lanka. Muslim tradition holds that Adam's Bridge was crossed by Adam following his expulsion from the Garden of Eden . Religious beliefs that the geological structure

6279-639: The mid-20th century. For example, in United States state-court opinions before 1944, sic appeared 1,239 times in the Westlaw database; in those from 1945 to 1990, it appeared 69,168 times, over 55 times as many. Its use as a form of ridicule has been cited as a major factor in this increase. The immoderate use of sic has created some controversy, leading some editors, including bibliographical scholar Simon Nowell-Smith and literary critic Leon Edel , to speak out against it. The bracketed form [ sic ]

6370-410: 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

6461-552: The original and the suggested correction (as they often are in palaeography ), one may give the actual form, followed by recte , then the correct form, in brackets. The Latin adverb recte means rightly . An Iraqi battalion has consumed [ recte assumed] control of the former American military base, and our forces are now about 40 minutes outside the city. According to the Journal of Seventeenth-Century Music Style Sheet , there should be no punctuation, for example no colon, before

6552-425: The protests against Sethusamudram Shipping Canal Project . NASA noted: "The images reproduced on the websites may well be ours, but their interpretation is certainly not ours. Remote sensing images or photographs from orbit cannot provide direct information about the origin or age of a chain of islands, and certainly, cannot determine whether humans were involved in producing any of the patterns seen." A report from

6643-426: 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

6734-478: The region from around 5,000 years ago to the present. The bridge starts as a chain of shoals from the Dhanushkodi tip of India's Pamban Island . It ends at Sri Lanka's Mannar Island . Pamban Island is accessed from the Indian mainland by the 2 km (1.2 mi) long Pamban Bridge . Mannar Island is connected to mainland Sri Lanka by a causeway. The lack of comprehensive field studies explains many of

6825-482: 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

6916-460: 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

7007-479: 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

7098-662: 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

7189-420: The source. Sic may show that an uncommon or archaic expression is reported faithfully, such as when quoting the U.S. Constitution : "The House of Representatives shall chuse [ sic ] their Speaker ..." However, several writing guidebooks discourage its use with regard to dialect, such as in cases of American and British English spelling differences . The appearance of a bracketed sic after

7280-500: The strait of Ramisseram [ sic ]". However, little notice was given to his proposal, perhaps because it came from "so young and unknown an officer", and the idea was only revived 60 years later. In 1823, Sir Arthur Cotton (then an ensign ) was assigned to survey the Pamban channel , which separates the Indian mainland from the island of Rameswaram and forms the first link of Adam's Bridge. Geological evidence indicates that

7371-503: The structure, but went on to shelve it. In 2007, the Sri Lankan Tourism Development Authority sought to promote religious tourism from Hindu pilgrims in India by including the phenomenon as one of the points on its "Ramayana Trail", celebrating the legend of Prince Rama. Some Sri Lankan historians have condemned the undertaking as "a gross distortion of Sri Lankan history". The idea of Rama Setu as

7462-550: The style manuals of New Zealand, Australian and British media outlets generally do not require italicisation. However, italicization is common in the United States, where authorities including APA Style insist upon it. Because sic is not an abbreviation, placing a full stop /period inside the brackets after the word sic is erroneous, although the California Style Manual suggests styling it as

7553-498: The then-Governor of Tamil Nadu , and revived for serious consideration in 2023. As of August 2024, its status is that the feasibility studies are nearing completion. The ancient Sanskrit epic Ramayana , in the Yuddhakanda, mentions a bridge constructed by the god Rama with aid from an army of Vanaras (monkeys or forest-dwellers) to reach the island Lanka and rescue his wife Sita from Ravana. In popular belief, Lanka

7644-636: The uncertainties regarding the nature and origin of Adam's Bridge. It mostly consists of a series of parallel ledges of sandstone and conglomerates that are hard at the surface and grow coarse and soft as they descend to sandy banks. The Marine and Water Resources Group of the Space Applications Centre (SAC) of the Indian Space Research Organisation (ISRO) concludes that Adam's Bridge comprises 103 small patch reefs. One study tentatively concludes that there

7735-490: The voyage around the island of Sri Lanka . This proposed channel's current alignment requires dredging through Adam's Bridge. Indian political parties including the Bharatiya Janata Party (BJP), All India Anna Dravida Munnetra Kazhagam (AIADMK), Rashtriya Janata Dal (RJD), Janata Dal (Secular) (JD(S)) and some Hindu organisations oppose dredging through the shoal on religious grounds. The contention

7826-533: 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

7917-553: 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

8008-440: The word analyse in a book review led Bryan A. Garner to comment, "all the quoter (or overzealous editor) [sic] demonstrated was ignorance of British usage". Occasionally a writer places [ sic ] after their own words, to indicate that the language has been chosen deliberately for special effect, especially where the writer's ironic meaning may otherwise be unclear. Bryan A. Garner dubbed this use of sic "ironic", providing

8099-524: Was constructed based their arguments on vague speculation, false implications, and the point that – as with many geological formations – not every detail of its formation has been incontrovertibly settled. Indian Geologist C. P. Rajendran described the ensuing media controversy as an "abhorrent" example of the " post-truth era, where debates are largely focused on appeals to emotions rather than factual realities". NASA said that its satellite photos had been egregiously misinterpreted to make this point during

8190-702: Was constructed by Rama have caused some controversy as believers reject the natural provenance of Adam's Bridge. S. Badrinarayanan, a former director of the Geological Survey of India , a spokesman for the Indian government in a 2008 court case, the Madras High Court , and an episode from the Science Channel series What on Earth? have claimed that the structure is man-made. In the What on Earth? episode, those claiming that Adam's Bridge

8281-416: 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

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