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38-691: The Glamorgan Heritage Coast lies between Ogmore-by-Sea and St Athan (with Nash Point at its midpoint) on the South Wales coast. There is a Heritage Coast Centre located at Dunraven Park, Southerndown , at the western end of the coast, providing an information point and education centre. The coast includes the Southerndown Coast Site of Special Scientific Interest at its heart, a 3.1-mile (5.0 km) section from Ogmore-by-Sea, particularly interesting for its exposed Triassic alluvial fan deposits of carboniferous limestone . There

76-470: 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

114-466: 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

152-593: A warm, shallow, subtropical sea and are rich in fossils, especially corals , crinoids and brachiopods . About 300 million years ago movements in the Earth's crust deformed and folded the rocks, as a result of which the rocks above the Carboniferous Limestone were worn away. Deposition resumed during the Triassic Period when the area was a desert with hills of limestone, and a dry plain where

190-798: 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, is known as the Carboniferous Limestone Supergroup . Within Great Britain

228-422: 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

266-449: Is an Iron Age promontory fort (as well as a 19th-century lighthouse) at Nash Point and an ancient cairn or cromlech at Cwm Marcross. The stretch of coast made the news in 2014 when coastal erosion left a towering stack of limestone "about five times the height of a house" separated from the main cliffs near Dunraven Bay. In 2016 four large sculptures were to be created by artist Howard Bowcott, to be placed at strategic points along

304-428: 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

342-520: 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

380-606: 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

418-584: 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

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456-541: 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

494-669: The Bristol Channel is now. Short violent storms caused flash-floods which carried debris down the hillsides and deposited it as alluvial fans of coarse, red conglomerate at the edge of the plain. These Triassic lie unconformably on the Carboniferous Limestone. About 205 million years ago, at the beginning of the Jurassic Period , the sea began to drown the land and the limestone hills became islands before finally being submerged. Sutton Stone, which contains pebbles of carboniferous limestone, represents rocks deposited close to

532-681: 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

570-460: 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

608-1181: 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

646-657: 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

684-526: 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

722-561: The beach. The rocky shoreline is well known as a rock climbing location. It is an interesting place geologically with a variety of fossils clearly visible. Many people use the car park by the estuary to the River Ogmore after entering the village, others move on to Southerndown . Ogmore has many beaches; along the path from the car park are Hardee's Bay and Horseshoe Bay. Further on below Brig Y Don hill there are deeps with caves and secluded coves, many only accessible at times permitted by

760-399: 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

798-689: 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

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836-709: 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

874-667: The coastline. Ogmore-by-Sea Ogmore-by-Sea ( Welsh : Aberogwr , meaning "Mouth of the River Ogmore ") is a seaside village in St Brides Major community in the Vale of Glamorgan , Wales. It lies on the western limit of the Glamorgan Heritage Coast of south Wales . The population in 2011 was 878. A polished flint axe-head of Seamer type was found at Ogmore Mill in 1976. Just like its counterparts in Cornwall , Ireland and Brittany ,

912-571: 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

950-421: 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

988-472: 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

1026-424: 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

1064-422: 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

1102-402: 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

1140-641: 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

1178-455: The same building; it celebrated its 50th anniversary in 2018. Ogmore-by-Sea is about three miles (five kilometres) south of Bridgend and about twenty miles (thirty kilometres) west of Cardiff . The beaches look out on Tusker Rock , and have sand at low-tide and sharp rocks at high-tide. The River Ogmore estuary is flanked by Ogmore beach on one side and the dunes of Merthyr Mawr on the other. The estuary makes bathing unsafe from most of

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1216-470: The shape of the landscape, and the coastline was moulded into its present shape by both subaerial and marine erosion, both of which continue today. Ogmore centre was built in the 1930s for the benefit of children from all over South Wales. It was closed in the mid-1990s, but was reopened as a Trust in 1998 and continued as such until 2007. Southerndown Golf Club and Portobello House are nearby. Carboniferous Limestone Carboniferous Limestone

1254-538: The shore of these islands. In deeper water the Southerndown Beds were deposited. Finally, when deep water covered the area the alternating limestones and shales of the Blue Lias were deposited. After the early Jurassic no evidence of geological events is preserved until the end of the last ice age , about 10,000 years ago. Fluctuating sea levels caused by the growth and melting of the ice sheets affected

1292-613: 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

1330-652: 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

1368-521: The tide. The rocks exposed along the stretch of coast near Ogmore-by-Sea were laid down between 340 and 195 million years ago. They are all sedimentary rocks, originally deposited as lime, mud, sand and coarse pebbles, and over long periods of time these were compacted and solidified into limestone , shale and conglomerate . The oldest rocks are hard, grey limestones that make up the Carboniferous Limestone . These were laid down in

1406-415: The use of false lights so that passing ships would mistake a flickering light as a lighthouse or ship at anchor and be lured to destruction, but there is no historical evidence for that. In 1954, a church was begun in one of the houses in the village. It grew too big for the house and in 1968, a building was erected to provide a place in which the group could meet. The church is still there now and meets in

1444-469: The west-facing beach and coast was notorious as a graveyard for ships during strong on-shore winds (south-westerly winds from the Atlantic ). Many ships, in particular, were destroyed on Tusker Rock , a brutal reef slightly out to sea that is totally covered at high tide. There are urban legends of organised shipwrecking at Ogmore (and all across the Vale of Glamorgan coastline) like tales from Cornwall of

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