103-593: Carboniferous Limestone is a collective term for the succession of limestones occurring widely throughout Great Britain and Ireland that were deposited during the Dinantian Epoch of the Carboniferous Period . These rocks formed between 363 and 325 million years ago. Within England and Wales, the entire limestone succession, which includes subordinate mudstones and some thin sandstones,
206-506: A D-class IB1 inflatable lifeboat . Cosy Corner is a park area, which over the years has housed a theatre, cinema, roller skating rink and ballroom. The Jennings Building, built in 1832, is a grade II listed building and Wales' oldest maritime warehouse. The building was identified as a potentially important facility as part of the Porthcawl Regeneration Strategy ; it houses three hospitality businesses. At
309-455: 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
412-535: A Roman Catholic girls' school, the school is now owned and operated by the Cognita Group . This is a state school which provides education for ages 3–11 and is participating in the Foundation Phase. It is a large primary school , with approximately 500 pupils, surrounded by extensive grounds. It has a conservation area and is in the process of building a pond. It has a large outdoor play area and
515-463: 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
618-620: A sensory garden . There is an outdoor classroom which is used for a range of activities. This is a state school located in Nottage. The school was built and opened for teaching in 1971 and has since been extended to incorporate the growing needs of the surrounding area and community. The school has been awarded the Eco-schools Green Flag and the BECTA ICT excellence award . This is a mixed state school for pupils between
721-434: 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
824-616: 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
927-449: 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
1030-949: 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
1133-412: 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
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#17327653715701236-470: A distinct South Wales-Mendip province which extends from Pembrokeshire in the west through southern Carmarthenshire , Glamorgan and south Powys to Monmouthshire , Gloucestershire and north Somerset . These rocks continue eastwards at depth beneath Oxfordshire . The Carboniferous Limestone sequence of South Wales and the Bristol area is currently (2012) subdivided thus: The limestone found north of
1339-483: 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
1442-637: 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
1545-455: 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
1648-584: A grand pavilion, a funfair named Coney Beach (modelled on Coney Island in New York ), a museum, three golf courses and the site of the former black obelisk. Built in 1887 to commemorate Queen Victoria 's Golden Jubilee , Porthcawl's promenade runs along the seafront from Lock's Common in the west to the harbour, before joining the Eastern Promenade and leading to Coney Beach and Griffin Park. It
1751-466: A greater distance across the limestone as underground channels and chambers fill up. Large sinkholes are called 'swallowholes' or 'potholes'. Gaping Gill , Alum Pot and the Buttertubs are well-known examples. Dry valleys are valleys without streams. Watlowes Valley is an excellent example. It was formed originally by a subglacial meltwater stream which existed during the last major Ice Age . After
1854-490: 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
1957-435: 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
2060-471: 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
2163-525: 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
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#17327653715702266-523: 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
2369-434: A new promenade, town square and car parking. The nearest railway station to Porthcawl is Pyle . Transport for Wales operates services to Cardiff Central , Swansea , Carmarthen and Manchester Piccadilly . Porthcawl railway station once served the town, sited at the top of Station Hill, but was closed in 1963. First Cymru and Stagecoach South Wales operate local bus routes, which include: The A4229 road links
2472-448: 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
2575-449: 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
2678-689: A rich heritage in the area with Porthcawl RFC . The town has lifeguard clubs that train the lifeguards that guard Coney Beach and Trecco Bay, as well as Rest Bay and Sker beaches. Porthcawl hosts a free weekly Parkrun at 9am each Saturday. It starts on the Lower Promenade in front of the Grand Pavilion, heads out to Rest Bay and finishes near to the pier. The famous world championship boxing match between WBC world featherweight champion Howard Winstone and his challenger, Jose Legra , which Legra won by fifth round technical knockout,
2781-410: A tourist-oriented beach at Trecco Bay, at the east end of the town; a sandy beach at Rest Bay , which lies to the north-west of the town; and the quiet and sandy Pink Bay leading out towards Sker Point where a tarmac-covered car park serves a sandy beach. There are many hotels, including the prominent Seabank Hotel , and guest houses as well as a funfair called Coney Beach . Four rocky points line
2884-458: Is a male voice choir formed in 1980 with 17 members. The choir has 45 members. Each year, the choir performs with a celebrity guest; in 2011, this was Lesley Garrett . Porthcawl has seven beaches: Five rocky points line the Porthcawl shore; from east to west, these are: Newton Point, Rhych Point, Porthcawl Point, Hutchwns Point and Sker Point . There are three scheduled monuments in
2987-612: Is a town and community in the Bridgend County Borough of Wales . It is located on the south coast, 25 miles (40 km) west of Cardiff and 19 miles (31 km) south-east of Swansea . Historically part of Glamorgan and situated on a low limestone headland on the South Wales coast, overlooking the Bristol Channel , Porthcawl developed as a coal port during the 19th century, but its trade
3090-422: Is a hard sedimentary rock made largely of calcium carbonate. It is generally light-grey in colour. It was formed in warm, shallow tropical seas teeming with life. The rock is made up of the shells and hard parts of millions of sea creatures, some up to 30 cm in length, encased in carbonate mud. Fossil corals, brachiopods and crinoids are frequently in evidence as components of Carboniferous Limestone; indeed
3193-560: 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
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3296-428: Is an area of almost bare, flat rock and is arguably the most fascinating feature of any area of Carboniferous limestone. They develop after the rock has been exposed by the scouring action of an ice sheet or glacier . Existing joints are subsequently exploited by the action of chemical weathering carbonation to form deep grykes and rounded blocks called clints . Grykes have a habitat of their own, which encourages
3399-482: 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
3502-402: 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
3605-474: 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
3708-416: 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
3811-520: Is completely dry, and a great attraction to rock climbers. A gorge is a steep-sided valley , often formed in a limestone area as the result of the collapse of a roof above a cave system. Gordale Scar is an excellent example. Caves are common subsurface features in limestone landscapes. In the Yorkshire Dales , there are numerous caves, three of which – Ingleborough Cave , White Scar Caves and Stump Cross Caverns – are now show caves for
3914-420: 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
4017-545: 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
4120-503: 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
4223-460: 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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4326-617: 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
4429-462: 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
4532-882: Is known as the Carboniferous Limestone Supergroup . Within Great Britain the suite of rocks known traditionally as the Carboniferous Limestone Series was deposited as marine sediments in three distinct ‘provinces’ separated by contemporary landmasses. One of these landmasses was the Wales-London-Brabant Massif , an east–west aligned belt of land stretching through central Wales and the English Midlands to East Anglia and on into Belgium . The limestones deposited to its south form
4635-604: Is named for the limestone which characterises the heart of the Peak District and through which deep gorges have been cut by rivers such as the Wye, Dove and Manifold . The limestone is concealed beneath younger rocks to the east and west and to the north through the South Pennines . To the north the limestone is exposed once again in east Lancashire and in the Yorkshire Dales . There are numerous limestone hills in
4738-560: 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
4841-473: 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
4944-472: 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
5047-672: Is reputed to have healing properties. Newton village homed St John's School, an independent day school established in 1921, which closed in c2016. It is also home to St Clare's School, which is also an independent day school and was established in 1938 by the Poor Clares order of nuns. The following festivals operate in the town: Porthcawl is one of the top locations in Wales for surfing , with both national and regional competitions held at Rest Bay. Other alternative sports, such as skateboarding and rollerblading , are also popular with
5150-518: 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
5253-579: Is the most abundantly available rock. However it is extensively quarried for other purposes: 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
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#17327653715705356-582: The Arnside and Silverdale AONB and in the southern Lake District e.g. Whitbarrow Scar with coastal exposures around the northern margins of Morecambe Bay such as Humphrey Head . An outcrop extends from Kirkby Stephen along the western side of the Vale of Eden and wraps around the northern margin of the Lake District as far as Cleator Moor . North again, it is a major landscape forming feature in
5459-540: The Black Mountain to Cribarth above the upper Swansea Valley . It is here referred to as the ‘north crop’ as distinct from a sub-parallel outcrop, the ‘south crop’ which defines the southern rim of the South Wales Coalfield . The outcrop continues through Ystradfellte to Pontneddfechan , Penderyn and Pontsticill . It then runs near the southern margin of the national park via Trefil and
5562-680: The Great Orme at Llandudno , the neighbouring Little Orme and a zone of country in inland Denbighshire running through Denbigh and Ruthin . A broader belt forms high ground immediately east of the Clwydian Hills extending south to form the impressive west-facing Eglwyseg escarpment north of Llangollen and continuing as a broken outcrop southwards beyond Oswestry . There are a few outcrops in Shropshire such as Titterstone Clee Hill and at Little Wenlock . The White Peak
5665-458: The Llangattock escarpment to Blorenge where it turns southwards. A very narrow ‘east crop’ and ‘south crop’ run by Cwmbran and north of Cardiff. It turns west again to meet Swansea Bay at Porthcawl . West of the bay, the rock forms the renowned southern coast of Gower between Mumbles Head and Worms Head . There are further occurrences in the Vale of Glamorgan , both inland and on
5768-1180: The North Pennines and thence through Northumberland to the Northumberland Coast where it extends to the Scottish border at Berwick-upon-Tweed . There are scattered outcrops along the north coast of the Solway Firth . Limestones occur in southern Ayrshire and in a very broken band running northeastwards through the Pentland Hills towards Edinburgh . There are limited outcrops on the coasts of East Lothian and Berwickshire , isolated outcrops in Fife and Stirlingshire and further occurrences around Greenock and Dumbarton . Carboniferous Limestone occurs most famously around The Burren in County Clare , western Ireland where it produces one of western Europe's most important karst landscapes. Carboniferous Limestone
5871-470: The cawl to be a corruption of Gaul , and that the area was an ancient landing point for Gaulish and Breton, or later Frankish and Norman knights. Porthcawl is a holiday resort in South Wales and is home to a large static caravan park known as Trecco Bay , which is owned and operated by Parkdean Resorts . It has an extensive promenade and several beaches, two of which are Blue Flag beaches :
5974-496: 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
6077-651: The Porthcawl Community area: Newton dates from the 12th century. St. John 's Church, founded by the Knights of the Order of St. John of Jerusalem 800 years ago and originally built as a fortress, overlooks the village green. The Jolly Sailor pub , the oldest in Porthcawl, and the Ancient Briton pub also overlooks the green. To the south of the church lies St John's Well, the water from which
6180-657: The Wales-London-Brabant Massif and south of the emergent Southern Uplands block is identified as a separate northern province. It is characterised by the presence of numerous ‘blocks’ and ‘basins’ each with its own particular depositional style. To the north of the Southern Uplands are the limestones of the Scottish Midland Valley stretching from Ayrshire and Arran in the west to Fife , Lothian and Berwickshire in
6283-526: The Yorkshire Dales and Brecon Beacons. Typically from 1–20 m deep and 1–60 m across, they form as a result of the subsurface collapse of limestone or through the more gradual dropping of surface material into caves. Streams flowing from higher impermeable slopes sink into the ground when they reach permeable limestone. During dry spells all water sinks very quickly on reaching the limestone, through sinkholes . In wetter conditions water flows
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#17327653715706386-430: 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
6489-461: The ages of 3 and 11 years, which includes a Foundation Phase Area admitting pupils of nursery age. This is a mixed state school with approximately 235 pupils. St John's School was a co-educational independent school, located in the village of Newton. The school provided preparatory, secondary and tertiary education leading to GCSE qualifications. The school closed at the end of July 2014. The Porthcawl Male Voice Choir, or Côr Meibion Porthcawl ,
6592-428: The area to take place, and also protecting more than 440 existing properties from flood risk. The first phase of Porthcawl's regeneration, Porthcawl Harbourside , was launched on 28 March 2008. A 17-acre (69,000 m ) site has been marketed to developers for a substantial mixed use scheme. The scheme is envisaged to include a new foodstore, extra retail space, leisure and community facilities, up to 450 houses/flats,
6695-434: 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 ,
6798-657: 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
6901-590: 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 . Porthcawl 51°29′N 3°41′W / 51.48°N 3.69°W / 51.48; -3.69 Porthcawl ( [pɔrθˈkaul] )
7004-399: The ceiling as the water continues to drip. When the water drips on to the floor of the cavern some evaporation occurs here also leaving a trace of limestone. Again over thousands of years a stalagmite is formed. A stone pillar is formed when a stalagmite and stalactite meet. Because it is brittle, the use of Carboniferous Limestone for building stone tends to be limited to those areas where it
7107-688: The coast. An important outlier is that of the Forest of Dean basin which forms the cliffs of the Wye Valley , straddling the England/Wales border and extends southwestwards through Chepstow to Undy . The larger part of the Mendip Hills are formed from Carboniferous Limestone, showing notable geomorphological features, including Cheddar Gorge , Burrington Combe and the show cave of Wookey Hole . The Avon Gorge west of Bristol and
7210-707: The coastal cliffs at Clevedon and Weston-super-Mare are cut in this rock. The limestone islands of Flat Holm and Steep Holm are prominent in views across the mouth of the Severn Estuary . There are limited outcrops on the Isle of Man and more extensive ones in Anglesey notably along the Menai Strait , around Benllech and towards Puffin Island . The Carboniferous Limestone belt extends eastwards to form
7313-466: 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
7416-469: 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
7519-406: 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
7622-646: The east. Though of Carboniferous age, the limestones of this Scottish province are not assigned to the Carboniferous Limestone Supergroup. The Carboniferous Limestone is widespread throughout Ireland. The Carboniferous Limestone is a significant landscape-forming rock unit in each of the depositional provinces of Great Britain within which it is found. Within Pembrokeshire the Carboniferous Limestone forms
7725-535: The end of Porthcawl jetty stands a white lighthouse built in 1860, as a navigational aid. It was the last coal and gas-powered lighthouse in the United Kingdom. It switched to being powered by North Sea gas in 1974, before becoming powered by electricity in 1997. The jetty and surrounding area are popular spots for sea fishing. The historic ships the PS Waverley , the last seagoing paddle steamer in
7828-421: The fact that the rocks are now above sea-level and no longer horizontal. The 'classic limestone walk' is a circular 10 km route from the field centre on the north side of Malham Tarn to the village of Malham, UK via Watlowes Valley and back again via Gordale Scar . Surface depressions, typically funnel-shaped and variously known as shakeholes, sinkholes , solution hollows and dolines are very common in
7931-399: 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
8034-572: 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;
8137-465: The former PADS skate park by the Harbour and the new bowl park off Heol Y Goedwig . There are three golf courses to the north of the town including Royal Porthcawl Golf Club , which attracts players from around the world. Porthcawl is home also home to football side Porthcawl Town Athletic F.C. , which boasts 1st, reserve and 3rd teams, as well as numerous junior teams. Rugby Union also has
8240-429: 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
8343-472: The growth of shade-loving ferns such as hart's tongue and dog's mercury . During the last Ice Age, a stream is thought to have poured over Malham Cove - the most spectacular feature in the Yorkshire Dales. At the end of the Ice Age the limestone, which had been frozen solid, once again became permeable, allowing the water to disappear through its joints. Now Malham Cove is a high cliff (83 m high) – it
8446-424: The ice retreated, the valley was further developed by a meltwater stream flowing across the limestone while it was frozen solid. Watlowes Valley is a particularly good example of a dry valley because it has a textbook profile - the south-facing side is less steep than the north-facing side. This results from the weathering and mass movement processes that have operated in the post-glacial period. A limestone pavement
8549-422: The limestone is pervious. As this happens the limestone is dissolved and removed in solution. Caverns are often found below the surface in the limestone and as the lime-rich water finds its way underground it begins to drip from the roof of the cavern. It is cold underground so there is little evaporation but some does take place leaving a trace of limestone on the roof. Over thousands of years a stalactite forms from
8652-410: 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
8755-402: The public. In Ireland there is a large number of show caves open to visitors - Crag Cave , Ailwee Cave and Marble Arch Caves . The stalagmite and stalactite are the two main subsurface features in a Carboniferous Limestone area. These are formed when rainwater - a weak carbonic acid capable of dissolving limestone - percolates through it via the grykes and joints underground. This means
8858-426: 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
8961-482: 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
9064-641: The rock is full of fossils. Carboniferous Limestone has horizontal layers (beds) with bedding planes, and vertical joints. These joints are weaknesses in the rock, which are exploited by agents of both denudation and weathering . They also lead to an important characteristic of Carboniferous Limestone – its permeability . Water seeps through the joints in the limestone. This creates a landscape geologists call karst , which lacks surface drainage but which has all manner of characteristic surface and subsurface features. The Carboniferous Limestone has been folded and faulted by massive Earth movements which can be seen by
9167-460: 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
9270-569: The seafront on the site previously occupied by the Esplanade Hotel, which dated back to the late 1880s. The Royal Society of Architects in Wales awarded 'Esplanade House' a Welsh Housing Design Award in 2006, but the architecture has proved unpopular with many local residents who have nicknamed it "the bottle bank". Porthcawl Lifeboat Station, built in 1995, is situated near the harbour. The station operates an Atlantic 85-class lifeboat and
9373-479: 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
9476-662: 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
9579-498: The shore: Hutchwns Point, Porthcawl Point (on which a lighthouse stands), Rhych Point and Newton Point. Porthcawl, like many British resorts, has suffered a decline in its holiday trade, especially since most of the South Wales Valleys coal pits closed. A major feature of the summer was the miners' fortnight, when large numbers of miners took their annual break. Tourist attractions in the area include sandy beaches,
9682-612: The spectacular coastal cliffs at St Govan's Head along from which are features such as Huntsman's Leap and the Green Bridge of Wales , a natural arch. It forms prominent headlands such as those of Stackpole Head and Lydstep Point and the cliffs at Tenby . A narrow, intensely quarried outcrop runs inland from Carmarthen Bay through Carmarthenshire from Kidwelly , entering the Brecon Beacons National Park at Llandyfan and extending westwards through
9785-472: The town council wards: Newton , Nottage , Porthcawl East Central, Porthcawl West Central and Rest Bay . These elect a total of five county councillors. Porthcawl is represented by the following parliamentary constituencies: There are six English medium schools in Porthcawl: four primary schools, one comprehensive school and one private school. Porthcawl Comprehensive School , on the western side of
9888-733: The town, has 1,500 pupils (aged 11–18) and 80 teaching staff. Both Ruth Jones and Rob Brydon attended this school. As at 2011, it was the only school to have received a new Band 1 assessment in the Bridgend County from the Welsh Government. St Clare's School is a co-educational independent school, located in the village of Newton (an eastern part of Porthcawl), in Bridgend County Borough. The school provides preparatory, secondary and tertiary education leading to GCSE and A-level qualifications. Originally
9991-533: 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
10094-553: 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
10197-572: The world, and the MV Balmoral sail from this area during the summer months. Prior to 1996, the town was divided into the Porthcawl East and Porthcawl West wards, electing a total of seven councillors to Ogwr Borough Council . Subsequent to the creation of Bridgend County Borough Council and as a result of The County Borough of Bridgend (Electoral Arrangements) Order 1998 , the town was divided into five county wards corresponding to
10300-421: Was held in Porthcawl on 24 July 1968. Porthcawl waterfront is proposed for substantial regeneration as part of the 7 Bays Project . The Planning Guidance outlines proposals that will result in the comprehensive regeneration of Porthcawl's waterfront, stretching from Cosy Corner and the harbour in the south, to Trecco Bay in the east. The plan includes the construction of new sea defences, enabling regeneration of
10403-416: 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
10506-492: Was restored in 1996. There are many cafes, bars, restaurants and hotels along the promenade, which offer views across the Bristol Channel . The Grand Pavilion , built at a cost of £25,000 in 1932, is the venue for shows, including the annual pantomime . The singer, actor and civil rights activist Paul Robeson once performed 'live' at the Pavilion via a transatlantic telephone link . Controversial luxury flats now dominate
10609-451: Was soon taken over by more rapidly developing ports such as Barry . In the north-west of the town, in the dunes known as Kenfig Burrows , are hidden the last remnants of the town and Kenfig Castle , which were overwhelmed by sand in about 1400. Porth is a common Welsh element meaning "harbour" and the cawl here refers to " sea kale ", which must have grown in profusion or even been collected here. Local folk etymology holds
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