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76-540: Although the main activity in Cabra is primary industry, it is noted as a source of red polished limestone . As a settlement, Cabra has existed over centuries, under many different rulers. In 2005, the municipality had a population of 20,940, most of whom (19,523) lived in Cabra township. Cabra is located in the Province of Córdoba in the autonomous community of Andalusia in southern Spain. The municipality's mean altitude

152-455: 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

228-463: 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

304-434: 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

380-616: 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

456-567: A chained King Boabdil el Chico to their shields. In 1522, a brotherhood of the True Cross, a formal religious order whose tradition was the practice of self-flagellation, formed in Cabra. On 7 November 1938, during the Spanish Civil War , Cabra was bombed by Republican planes. Cabra was not a strategic objective as the front lines were at a distance. The official figures were 101 dead and over 200 injured. Cabra main industry

532-449: 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

608-949: 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

684-412: 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

760-483: 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

836-637: 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

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912-455: 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

988-490: 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

1064-435: 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

1140-471: 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

1216-525: 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

1292-523: 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

1368-448: 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

1444-449: 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

1520-513: Is 452 m (1,483 ft) and it covers 229 km (88 sq mi). The town is built in a valley between the Sierra de Cabra and the Sierra de Montilla, which together form the watershed between the rivers Cabra and Guadajoz. It has a population density of 91.4 inhabitants per km². The geographical mean coordinates are 37°28′N 4°27′W  /  37.467°N 4.450°W  / 37.467; -4.450 , 72 km (45 mi) from

1596-436: Is a Spanish city in the province of Córdoba , autonomous community of Andalusia . It is situated about 45 miles (70 km) from the provincial capital, Córdoba . It has a population of around 30,000 people. The name of the town comes from the bridge over the river Genil . The town is an agricultural centre, also known for its Semana Santa celebration, contracted in the local vernacular to " mananta ". Puente Genil

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1672-462: Is agriculture. Up to 45% of the population work in and over 85% of the land is involved in primary industry. Cabra's key products are olives, olive oil, grapes, and wine. The industrial sector occupies approximately 30% of the population and produces textiles, fabricated metal, and furniture. The remainder of the Cabran population is employed in service industries and tourism. A regional hospital serves

1748-560: 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

1824-482: 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

1900-402: 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

1976-474: 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

2052-416: 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

2128-420: 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

2204-545: 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

2280-503: 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

2356-460: 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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2432-617: 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

2508-462: 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

2584-560: 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

2660-473: 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

2736-472: 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

2812-518: 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

2888-729: The Partido Popular , 4. In 2011, Fernando Priego Chacón of the Partido Popular became the mayor of Cabra. 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

2964-795: The Caliphate of Cordova fell. Cabra came under the control of Granada. Under Alfonso the VIth , Granada and Seville were feudatories of Castile. In 1079, the Battle of Cabra took place. Rodrigo Díaz de Vivar (El Cid), with the Castilian troops of Alfonso the VIth , fought on the side of the Sevillian king Al-Mu'tamid ibn Abbad against Granada. El Cid conquered the ruler of Granada Abdallah and his ally García Ordóñez . El Cid fell out of favour with Alfonso VI . Abdallah of Granada , together with

3040-642: The Order of Calatrava , the control of Cabra passed through a number of lords. In 1333, Cabra was besieged by the King of Granada, who, after knocking down the castle and its walls, imprisoned the population. Between 1342 and 1344, after his rescue of Carba, Alfonso XI ordered that the Master of Cabra re-populate the area. In 1344, the land of Cabra was given to Lady Eleanor de Guzmán . Alfonso XI's edict read, and gave Cabra additional franchises and liberties, among which

3116-644: The river Cabra , there is a reproduction of a plaque dedicated to this aqueduct . On 17 March, 45 BC, the Battle of Munda took place near Igabrum. This was the last battle of the Second Civil War of the Republic of Rome between Julius Caesar and the Optimate supporters of Pompey . Igabrum was under the jurisdiction of the Astigitano convent, one of the four Roman provinces of Andalusia . In

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3192-597: The 4th century AD, Igabrum embraced Christianity and became an episcopal centre. In the 600s, Sinagio, who assisted Juan, the Concilio Iliberitano, of the 3rd Reconcile of Toledo, Deodato, Bacanda, Gratino, and Constantino, lived there. The church of San Juan Bautista del Cerro was the central church and may have been constructed on the Roman Fortuna temple. After the fall of the Roman Empire ,

3268-591: The Christian faith perhaps up to the invasion of the Almohades . In 889 AD, Christians in Moorish Spain , including Cabra, under Samuel ( Omar ibn Hafsún ) rebelled against Muslim rule. Samuel regained control of Spain as far as Córdoba . He was defeated at Poley ( Aguilar de la Frontera ). Samuel and his son ruled their land from Bobastro , until Abderramán III forced them into exile in 928. In 1031,

3344-496: 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

3420-773: The Emir Ali ibn Yusuf . Christians living in Andalus who did not flee to Aragon were punished severely in reprisals and deported to Morocco . In 1148, the region was invaded by the North African almohades . In 1217, Fernando III inherited the Kingdom of Castile from his mother, Doña Berenguela , and in 1230, the Kingdom of León from his father, Alfonso the IXth . In 1240, Fernando III peacefully re-conquered Cabra, where

3496-576: The Roman Empire. Livy regarded Licabrum as a well-furnished and well-defended fort. The Roman general Gaius Flaminius besieged and conquered Licabrum. Its commander, Corribilo, was imprisoned. This is recorded in Livy 's Ab Urbe Condita ( City ), Pliny the Elder and Strabo referred to the many people and marvels of knowledge and wealth in Licabrum. The Greeks may have built a grand temple dedicated to

3572-650: The Spanish word Cabra (from Latin capra ) means goat . The city of Cabra has been settled since Paleolithic times. The Turdetani , the Andalusian descendants of Tartessos , lived in the area. As part of the Tartessoian kingdom and during Carthaginian and Roman times, Cabra was a market town. In the Roman era, the town was called Licabrum . In the 3rd century BC, Licabrum was involved in an uprising against

3648-430: 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

3724-434: 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 ,

3800-657: 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

3876-525: 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 . Puente Genil Puente Genil ( Spanish pronunciation: [ˈpwente xeˈnil] )

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3952-581: The crown. In 1439, the King Juan II of Castile appointed Don Diego Fernandez de Cordoba and Montemayor the Lord of Cabra, and in 1455, Enrique IV of Castile was appointed Count of Cabra. During this time, there was frequent infighting between the feudal lords of the Kingdom of Castile . For example, Don Diego Fernandez de Cordoba and Montemayor captured his cousin, Don Gonzalo Fernández de Córdoba and Aguilar, and imprisoned him in Cabra castle. Don Gonzalo

4028-466: 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

4104-469: 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

4180-406: 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

4256-399: 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

4332-572: 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;

4408-429: 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

4484-517: The goddess Tyche which was then adopted by the Romans for the goddess, Fortuna . In addition, there was a temple dedicated to the Greek god, Apollo . Cabra was the site of an aqueduct 5 miles (8.0 km) in length, which was constructed by Marco Cornelio Novano Bebio Balbo, the provincial flamen and Roman prefect of the college of engineers of Igabrum (a later name for Licabrum). At the source of

4560-475: The inhabitants shared his customs and religion. Fernando III increased Cabra's area to include the majority of Andalusia which was under the control of his step-brother, Rodrigo Alfonso de León. The parliaments of León and Castile merged under the reign of Fernando III, marking the rise of the Crown of Castile . León, Toledo, Jaen, parts of Andalusia, and the conquered Arab dominions became the Kingdom of Castile. From

4636-410: 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

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4712-581: The province's capital, Córdoba . The municipality hosts a nature reserve, the Parque Natural de las Sierras Subbéticas. Around Cabra, there are eight smaller villages, including Gaena , Las Huertas Bajas and La Benita . The area is known for its stone, called mármol rojo de Cabra . It is not a marble but a pink to red limestone capable of high polish. Apparently Popular etymology from Latin Licabrum/ Egabro (via Arabic Qabra?), as

4788-426: 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

4864-482: 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

4940-460: 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

5016-723: The rulers of Seville and Badajoz , pressed for the end of the parias and requested the aid of the Almoravids . The North Africans entered the Iberian peninsula in 1086, defeating Alfonso VI in the Battle of Sagrajas near Badajoz. Cabra was conquered by the Almoravids in 1090. Around 1124, King Alfonso I of Aragon attacked Andalusia, crossing Alcalá la Real , Luque , Baena , Écija , Cabra and Lucena . On 10 March 1126, in Arnisol, Alfonso I of Aragon conquered Abu Bakr, son of

5092-479: 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

5168-662: 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

5244-742: The southern part of the Córdoba province. Don Luis Aguilar y Eslava donated property to allow the foundation of the Royal College of the Immaculate Conception of Cabra. Over time, this school of humanities, now called IES Aguilar y Eslava , has grown in importance as a place of learning in Andalusia. In the 2004 Spanish General Election , the Partido Socialista Obrero Español received 49.05% of

5320-479: The town, named Egabro , became a centre of Visigoth power for the surrounding area. It was a bishopric between the 6th and 8th centuries. It spanned the area from Lopera in the north to Benamejí or Antequera in the south, and to Puente Genil in the west. After the Muslim conquest, the town was named Qabra and became the capital of the surrounding area, Cora. Bishops such as Recafredo and Reculfo preserved

5396-712: The vote in Cabra, the Partido Popular , 29.04%, the Partido Andalucista , 14.07% and Izquierda Unida , 5.17%. From 2007 to 2011, the Mayor of Cabra was María Dolores Villatoro Carnerero, of the Partido Socialista Obrero Español . Carnerero's party governed in coalition with Izquierda Unida . Her party had 6 municipal councillors in the town's ayuntamiento , the Partido Andalucista had 6, Izquierda Unida , 5 and

5472-533: 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

5548-553: 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

5624-416: 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

5700-557: Was released in 1476 through the intercession of Ferdinand and Isabella . In 1483, at the Battle of Martin Gonzalez (Lucena), the second Count of Cabra, Don Diego Fernández de Córdoba y Carrillo de Albornoz , defeated the last King of Granada , Boabdil el Chico ( a Moor ), who was then imprisoned in Cabra castle. Ferdinand and Isabella allowed those who had supported them in this battle to add an image (a barracks symbol) which depicted

5776-401: Was the granting of Cordoba jurisdiction and exemptions from the martiniega tax. Eleanor de Guzmán 's son, Enrique II of Castile , was born in Cabra, and was baptised king in the church of San Juan Bautista del Cerro. In 1380, the title Count of Cabra was inherited by his son, Enrique de Castilla y Sousa, ( Duke of Medina Sidonia ). After this Count of Cabra's death, the title reverted to

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