The Late Jurassic is the third epoch of the Jurassic Period, and it spans the geologic time from 161.5 ± 1.0 to 145.0 ± 0.8 million years ago (Ma), which is preserved in Upper Jurassic strata .
61-528: The Purbeck Group is an Upper Jurassic to Lower Cretaceous lithostratigraphic group (a sequence of rock strata ) in south-east England . The name is derived from the district known as the Isle of Purbeck in Dorset where the strata are exposed in the cliffs west of Swanage . The Purbeck Group is famous for its fossils of reptiles and early mammals . This sequence of rocks has gone by various names in
122-474: A Site of Special Scientific Interest (SSSI). Albion Stone PLC now extract all their stone through mining which dramatically reduces the impact on the environment and local residents. Jordan's Mine is currently the biggest mine on Portland. Bowers Quarry has been operational since the late 18th century. It has been leased from The Crown Estate since 1979, and in 2002 it became the site of the first Portland stone mine by Albion Stone PLC. Extraction from this site
183-592: A Portland stone façade to complete its stripped Classical design. After the Second World War (1939–1945), the bombed out centres of many English towns and cities, such as Plymouth , Bristol , Coventry and London were reconstructed using vast facades of Portland stone. Many of the buildings surrounding the flagship Parkinson Building at the University of Leeds are clad in Portland stone, including
244-680: A building stone throughout the British Isles , notably in major public buildings in London such as St Paul's Cathedral and Buckingham Palace . Portland stone is also exported to many countries, being used for example at the United Nations headquarters in New York City. Portland stone formed in a marine environment, on the floor of a shallow, warm, sub-tropical sea probably near land (as evidenced by fossilised driftwood, which
305-493: A machine. Slots are cut into the top, bottom, sides and middle of the stone. A flat steel pillow is inserted into the middle cut and slowly inflated with water. The stones are gently broken off at the back without placing any stress on the resulting blocks. This method of extraction is significantly more expensive than blasting, but results in a higher yield thereby saving valuable reserves for future generations. The environmental benefits are substantial as mining significantly reduces
366-541: A mine as an extension from an existing quarry). Albion Stone Plc began the process to open this mine in 2015 and reserves are estimated to last for 50 years (2066). Independent Quarry and Admiralty Quarry are both owned by The Crown Estate and have been leased since 1982. These quarries have been worked since the mid-19th century with the final dimension stones coming out of Independent in 2006, although some stocks of Portland stone block still remain. Coombefield Quarry , located near Southwell has been open cast quarried over
427-659: A popularity amongst masons and architects that has endured ever since. The East side of Buckingham Palace , the official London residence of King Charles III , including the balcony, was faced with Portland stone, first in 1854 and again in 1913. The Victoria Memorial (unveiled 1911) is also made of it. Inigo Jones (1573–1652) used Portland stone to build the Banqueting Hall in Whitehall in 1620. Sir Christopher Wren used nearly one million cubic feet to rebuild St. Paul's Cathedral and many other minor churches after
488-455: Is Rufus Castle at Church Ope Cove, Portland. The original structure was probably built around 1080, rebuilt around 1259 and rebuilt yet again around 1450, which is the likely date of the walls seen today. The first known Portland stone quarries were situated on the northeastern coast of the Isle, close to Rufus Castle, where huge landslips made the stone more easily accessible, and the proximity of
549-755: Is also built with Portland stone, as are the public buildings in Cardiff's civic centre. Architect Charles Holden significantly used the stone in his major commissions of the 1920s and 1930s, including Senate House and 55 Broadway , the home of the London Underground . The 1929 steel framed building (one of the first erected in the United Kingdom) of the London School of Hygiene & Tropical Medicine , based in Keppel Street, has
610-467: Is also worth noting that stone tends to split much more easily parallel to bedding planes (called graining) than perpendicular to them (called cutting). In 1999, Italian stone cutting equipment, originally designed for use in Tuscany 's marble quarries was imported by Albion Stone and applied to the extraction of Portland stone. This new technology eliminated the need for blasting, significantly improved
671-422: Is not uncommon). When seawater is warmed by the sun, its capacity to hold dissolved gas is reduced; consequently, dissolved carbon dioxide (CO 2 ) is released into the atmosphere as a gas. Calcium and bicarbonate ions within the water are then able to combine, to form calcium carbonate (CaCO 3 ) as a precipitate. The process of limescale build up in a kettle in hard-water areas is similar. Calcium carbonate
SECTION 10
#1732780811386732-484: Is now completely underground, with the original Bowers Mine in the extreme southern end of the quarry and the High Wall Extraction on the eastern and south east boundaries. High Wall Extraction is a series of small mines that extract otherwise wasted stone that sits between the final faces of the quarry and the actual boundary of the site. Stonehills Mine is the first completely new mine on Portland (not
793-468: Is part of the Inmosthay Quarry in the centre of the island, which also includes Fancy Beach. The quarry has been worked since the late 19th century. Albion Stone leases the southern section from The Crown Estate and purchased the northern part of the site in 2006. The majority of the southern reserves lie under the grounds of the local cricket club. To avoid disturbing the site at surface level,
854-568: Is privately owned by Portland Stone Firms. Open cast quarrying provides quicker extraction of raw block dimension stone whilst maintaining its integrity. The majority of buildings in London today use Portland which has been quarried using the same methods over the last 60 years. Broadcroft Quarry is located on the eastern side of the island and is a part of the open cast quarries used for St Paul's Cathedral. Privately owned by Portland Stone Firms Limited there are over 20 years of reserves left and still being actively quarried. The coastal strip toward
915-418: Is the principal constituent of most limestones. Billions of minute crystals of precipitated calcium carbonate (called calcite ) accumulated forming lime mud (called micrite ) which covered the sea floor. Small particles of sand or organic detritus, such as shell fragments, formed a nucleus, which became coated with layers of calcite as they were rolled around in the muddy micrite. Portland stone measures 3.5 on
976-705: Is typically between 45 and 120 metres (148 and 394 ft) thick. In the Weald of East Sussex the Purbeck Group has a typical thickness of between 77 and 186 metres (253 and 610 ft). In most places the Purbeck Group rests conformably upon the Portland Group and it is conformably overlaid by the Wealden Group ; but there are in some districts distinct indications that the Portland Group
1037-400: Is very extensively exposed on the Isle of Portland , where many of the individual beds are known by distinctive names. The chief building stones of Upwey belong to this part of the Purbeck Group. In the past, many geologists have ranged the Purbeck Group with the overlying Lower Cretaceous Wealden Group on account of the similarity of its fresh-water faunas; but the marine fossils, including
1098-524: The Great Fire of London in 1666. All of the stone used by Wren was transported by sailing barge from Portland to the centre of London via the sea and then up the Thames. Wren's widespread use of Portland stone firmly established it as London's "local stone" and as one of the best-loved British building stones. Other famous London buildings constructed of Portland stone are The British Museum (1753) with
1159-933: The Michael Sadler Building, the Chemistry and Engineering buildings and the new Laidlaw Library. Oxford typically uses oolitic limestone in its buildings, and the Ashmolean Museum has been refurbished using a large amount of Portland stone. Portland stone has also been used across the world. Examples include the UN building in New York, the Casino Kursaal in Belgium and the Auckland War Memorial Museum . Most of
1220-608: The Mohs scale of mineral hardness . The calcite gradually accumulated (by accretion) around the fragments of shell in concentric layers, forming small balls (of less than 0.5 mm diameter). This process is similar to the way in which a snowball grows in size as it is rolled around in the snow. Over time, countless billions of these balls, known as " ooids " or "ooliths" (from the Greek for "egg-shaped" or "egg-stone"), became partially cemented together (or lithified) by more calcite, to form
1281-717: The Purbeck marble and Unio -bed, in the lower part. The Middle division (50 ft (15 m)), mainly thin limestones with shaly partings, contains the principal building stones of the Swanage district; near the base of this subdivision there is a 5 in (13 cm), bed from which an interesting suite of mammalian remains has been obtained; in this portion of the Purbeck Group there are some marine bands. The Lower Purbeck consists of fresh-water and terrestrial deposits, marls, and limestones (the famous Portland limestone ) with several fossil soils known as dirt beds . This division
SECTION 20
#17327808113861342-730: The Spilsby Sands and in Yorkshire by portions of the Speeton Clay . The rocks predominantly comprise calcareous mudstones though also include clays , shales and marls with marly , tuffaceous and shelly limestones , occasional oolitic and sandy strata, and evaporites . Nodules of chert are present in some of the limestones. The thickness of the formation in Wiltshire is 80 to 90 ft (27 m), but in Dorset it
1403-650: The Weald-Artois anticline . Purbeckian aged deposits occur even further south in the Charente . In north-west Germany three subdivisions are recognized in strata of the same age: in descending order Purbeck Kalk , Serpulit and Münder Mergel . The Purbeck Group outcrops follow the line of the Jurassic outcrop from Dorset, through the Vale of Wardour, Swindon , Garsington , Brill and Aylesbury . In East Sussex,
1464-408: The genus level ( Megalosaurus sp (theropod indet), Opisthias ) are among the fossils that have been recovered from the formation. Fossil eggs referable to the oogenus Mycomorphoolithus are also known from the Purbeck Group. The silicified stumps and trunks of cycads and coniferous trees , often surrounded by great masses of calcareous concretions ( burrs ), are very noticeable in
1525-556: The plesiosaurs and the chelonians ( Chelone , Pleurosternum ) are representative reptiles . The mammals, mostly determined from lower jaws, found in the beds mentioned above include Plagiaulax , Amblotherium , Stylodon , Dorsetodon , Triconodon , Spalacotherium and several others. The isopod crustacean Archaeoniscus brodiei is very common in the Purbeck of the Vale of Wardour . Reptile remains diagnostic to
1586-666: The "New Build (Modern Non-Load-bearing Stone) Award" in the 2006 Natural Stone Awards. Portland stone has been designated by the International Union of Geological Sciences as a Global Heritage Stone Resource . Following the First World War, Sir Edwin Lutyens used Portland stone (quarried from the bottom of Wakeham) to construct the Cenotaph in London's Whitehall. Erected in 1920, The Cenotaph commemorates
1647-530: The 14th century. Extraction as an industry began in the early 17th century, with shipments to London for Inigo Jones ' Banqueting House . Wren 's choice of Portland for the new St Paul's Cathedral was a great boost for the quarries and established Portland as London's choice of building stone. The island was connected by railway to the rest of the country from 1865. Albion Stone PLC has been quarrying and mining Portland stone since 1984. Portland Stone Firms Ltd have been quarrying Portland stone since 1994. Jordans
1708-582: The 1930s. Manchester buildings with Portland stone exterior include 100 King Street (1935), Arkwright House (1937), St. James Buildings (1912), Manchester Central Library (1934), Kendal Milne (1939) and Sunlight House (1932). Two of Liverpool's Three Graces , the Cunard Building and the Port of Liverpool Building , are clad in Portland stone which surrounds their reinforced concrete frames. The Nottingham Council House , completed in 1929,
1769-753: The Dorset region the oldest and lowermost Purbeck Limestone below the Lulworth in Wiltshire , Oxfordshire and Buckinghamshire has been given its own status as the Haddenham Formation . In East Sussex the Purbeck Group is formally subdivided into the Blues and Greys Limestones members The sequence was traditionally divided into three, though along different lines viz. Upper, Middle and Lower. The Upper Purbeck comprises 50 to 60 ft (15 to 18 m). of fresh-water clays and shales with limestones,
1830-706: The Jurassic. Listed here are only a few of the many Jurassic animals: Portland limestone Vale of Wardour : Tisbury Member, Wockley Member, Chilmark Member Portland stone is a limestone geological formation (formally named the Portland Stone Formation ) dating to the Tithonian age of the Late Jurassic that is quarried on the Isle of Portland in Dorset , England. The quarries are cut in beds of white-grey limestone separated by chert beds. It has been used extensively as
1891-575: The Portlandian, being the first to describe the patch-reef facies and Dorset-wide sedimentation details. Ian West of the School of Ocean and Earth Sciences at Southampton University completed a detailed geological survey of Withies Croft Quarry before the Portland Beds were quarried by Albion Stone plc. Stone has been quarried on Portland since Roman times and was being shipped to London in
Purbeck Group - Misplaced Pages Continue
1952-694: The Purbeck Formation. Ensom in 1985 and Clements in 1993 detailed the stratigraphy of the Worbarrow Tout and Durlston Bay sections respectively, with the former considering there to be 12 members in the Purbeck Limestone Formation, while the latter had an additional two members within the Lulworth and Durlston Formations of the Purbeck Limestone Group. The Members of Ensom and Clements were lowered to
2013-479: The Purbeck Group outcrops at three locations north and northwest west of Battle, East Sussex and at Netherfield. They also occur at several other locations east of Heathfield, East Sussex and at Beak's Wood near Burwash . Deposits of evaporite minerals such as gypsum and anhydrite , within the Purbeck Group are mined and processed in Mountfield, East Sussex . In Lincolnshire they are represented in part by
2074-518: The building of Chelsea Barracks , Wilkins Terrace at UCL University College London , St James's Market Haymarket, London and Green Park tube station . Portland stone is prevalent in Manchester despite the historical preferred use of hard-wearing materials, such as Burmantofts and sandstone to resist the harsh industrial environment. Portland stone was mostly used in Manchester during
2135-418: The company has applied and received permission to extract the stone using mining rather than quarrying techniques. The reserves to the north will be quarried using the diamond bladed cutting machines, hydro bags and wire saws to shape the blocks. This process avoids the use of dusty and noisy blasting as the primary extraction method, thereby protecting the surrounding environment, which has been designated as
2196-508: The dirt beds of Portland and near Lulworth . Chara is found in the fresh-water cherts of the Middle Purbeck. [REDACTED] This article incorporates text from a publication now in the public domain : Chisholm, Hugh , ed. (1911). " Purbeckian ". Encyclopædia Britannica . Vol. 22 (11th ed.). Cambridge University Press. pp. 657–658. Upper Jurassic In European lithostratigraphy ,
2257-525: The fishes, ally the Purbeck more closely with the Upper Jurassic rocks of other parts, and it may be regarded as the equivalent of the upper Volgian of Russia . Contemporaneous rocks are also present in the neighbourhood of Boulogne-sur-Mer , where they are characterized by thin limestones with Cyrena and gypsiferous marls. These French outcrops occur, just like those in England, in the core of
2318-436: The forces necessary to loosen the stone to the point where it can be easily removed using large wheeled loaders . Splitting stone, using pneumatic drills is arduous work and so wire-saws have been introduced into the quarries, replacing much of the plug and feather cutting. Mining in Portland is done by using a room and pillar method. The mine is advanced by extracting the stone using an abrasive tool chain cutter mounted on
2379-455: The impact on wildlife and the local community with reduced noise and dust. Portland's freestone has almost certainly been used as a building material since Roman times. The many well crafted Roman sarcophagi (stone coffins and matching lids, hewn from single large blocks of Portland stone) that have been unearthed locally over the years, testify to the skill of their makers. The earliest known building to be constructed using Portland stone
2440-795: The important civic and administrative buildings which survive from 18th and 19th century Dublin , Ireland, known then as "the second city of the Empire", are of Portland stone, including City Hall (1779), the Houses of Parliament (1767), the Custom House (1791), the National Gallery (1864) and the General Post Office (1818). More recent projects include the BBC Broadcasting House in London, which won
2501-409: The last 80 years and is one of three privately owned quarries by Portland Stone Firms Ltd, the largest landholder on the island. The quarry is nearing the end of its life and will be regenerated as a holiday caravan park to boost local tourism on the island. Perryfield Quarry is found towards the middle of the island and being actively open cast quarried. There are over 20 years of reserves left which
Purbeck Group - Misplaced Pages Continue
2562-559: The latter being abundant in the Cinder bed of the Middle Purbeck. The fresh-water mollusca include Viviparus ( Paludina ), Planorbis , Melanopsis , Unio , Cyrena . A large number of insect genera has been found in the Middle and Lower Purbeck Group. Dinosaurs ( Owenodon , Echinodon [known from "Isolated skull elements of at least [three] individuals."]), crocodylians ( Goniopholis , Petrosuchus ), Cimoliosaurus ,
2623-571: The millions of people killed in this and subsequent conflicts. The RAF Bomber Command Memorial in London's Green Park commemorates the 55,573 crew members of the RAF's Bomber Command who were killed between 1939 and 1945. The gravestones for British personnel killed in the First and Second World Wars were made out of Portland stone. The Commonwealth War Graves Commission use Portland Limestone supplier Albion Stone's Portland Basebed. Portland stone
2684-553: The name " Malm " indicates rocks of Late Jurassic age. In the past, Malm was also used to indicate the unit of geological time, but this usage is now discouraged to make a clear distinction between lithostratigraphic and geochronologic/chronostratigraphic units. The Late Jurassic is divided into three ages, which correspond with the three (faunal) stages of Upper Jurassic rock: During the Late Jurassic Epoch, Pangaea broke up into two supercontinents , Laurasia to
2745-830: The new WCEC extension in Portland Roach which was short-listed for the Stirling Prize in 2017, Somerset House (1792), the General Post Office (1829), the Bank of England , the Mansion House and the National Gallery . Tower Bridge is partly clad in Portland stone (along with Cornish granite ). Portland stone was used in 1923 to build the supporting pillar of the Grace Gates at Lord's Cricket Ground . Recently, Portland stone has been used in
2806-534: The north, and Gondwana to the south. The result of this break-up was the spawning of the Atlantic Ocean . However, at this time, the Atlantic Ocean was relatively narrow. This epoch is well known for many famous types of dinosaurs , such as the sauropods , the theropods , the thyreophorans , and the ornithopods . Other animals, such as some crocodylomorphs and the first birds , appeared in
2867-428: The oolitic limestone that is called Portland stone. The degree of cementation in Portland stone is such that the stone is sufficiently well cemented to allow it to resist weathering, but not so well cemented that it cannot be readily worked (cut and carved) by masons. This is one of the reasons why Portland stone is so favoured as a monumental and architectural stone. Geoff Townson conducted three years doctoral research on
2928-560: The past including amongst others the Purbeck Beds , Purbeck Formation , Purbeck Limestone Formation and Purbeck Stone . Rocks of this age have in the past been called the Purbeckian stage by European geologists. The Purbeckian corresponds with the Tithonian to Berriasian stages of the internationally used geologic timescale . The stratigraphic organisation of the Purbeck Group has varied significantly over time since it
2989-476: The quarries' environmental performance and removed the potential for any possible damage to the stone being quarried through shock. Full account of the local jointing pattern is made when deciding the position and orientation of cuts. Once the quarry faces have been cut, the stone is gently displaced hydraulically. This is done using "hydro-bags", which are thin, flat, steel bags or envelopes that when inflated with water under moderate pressure, are capable of producing
3050-500: The refurbishment of the British Museum 's central court, the planned Portland stone was controversially substituted with Anstrude Roche Claire stone from France, another similar (but cheaper) oolitic limestone. The term, "Portland cement", was coined by Joseph Aspdin who in 1824 patented a hydraulic binder created by burning a mixture of limestone and clay , resembling the previously existing Roman cement and presenting
3111-485: The rock from its natural bed, hopefully undamaged. Stone was cut using plugs and feathers , where a series of short, small diameter (typically 30 mm) holes are drilled in a line where a cut is to be made. One plug and two feathers were inserted into each hole and each plug is hit in turn with a sledgehammer until the stone yields to the extreme tensile stresses produced. Most stone is many times weaker in tension than in compression, plugs and feathers utilise this fact. It
SECTION 50
#17327808113863172-502: The sea allowed the quarried stone blocks to be moved over relatively large distances by barge. Portland stone was used to build the Palace of Westminster in 1347, the Tower of London in 1349 and the first stone London Bridge in 1350. Exeter Cathedral and Christchurch Priory , also constructed during the 14th Century, are built of Portland stone. Its superb characteristics have ensured
3233-482: The southern tip of the island has permission to be worked by Portland Stone Firms and will provide in excess of 30 years of reserves. Permission has been granted for this to be open cast quarried. Once quarries have been worked they are then restored. The Portland Sculpture and Quarry Trust was formed in 1983 and is dedicated to preserving a knowledge and understanding of stone and the landscape from which it comes. The main non-working quarry remains Tout Quarry in which
3294-479: The span of southern England. In the Wessex Basin (or Vectian Basin) area of Dorset where the Purbeck was first recognized, the younger Durlston Formation can be divided into the Peveril Point Member and Stair Hole Member, while the older Lulworth Formation is divided into the Worbarrow Tout Member, Ridgeway Member, and Mupe Member. Within the Weald Basin , the Lulworth and Durlston Formations can be recognized, but their subdivisions are undifferentiated, while outside
3355-402: The status of Beds by Westhead and Mather in 1996 as they were of limited applicability outside of their originally-observed sections, with them only recognizing five members of the Lulworth and Durlston Formations, each encompassing multiple of the Beds of earlier studies. The British Geological Survey recognises three formations and five members of the Purbeck Group, exposed differently across
3416-421: The trust is based, where a workshop is held every year. Tout Quarry has been donated to the Portland Sculpture and Quarry Trust by Portland Stone Firms Limited. Traditionally small diameter holes (35 mm) were drilled horizontally under each rock and charged with a small quantity of gunpowder , chosen because of its relative non-shattering properties. When fired the gunpowder produced a "heave" which dislodged
3477-439: Was first labelled in 1816 for a section of limestone on the Isle of Purbeck. The labels Purbeck Limestone, Purbeck stone, Purbeck series and Purbeck strata were all used by Webster in 1816, with Purbeck Beds first used by Sir William Buckland in 1818. Works from 136 to 1884 provided some descriptions and labels of the locally-known beds, and the divisions of the Purbeck into upper, middle, and lower units. The label of Lulworth Beds
3538-415: Was formerly worked from the Lower Purbeck at Swanage. No zonal fossil has been recognized for the British Purbeckian strata, but the horizon is approximately equivalent to that of Pensphinctes transilorius of the European continent. The Purbeckian equivalents of Spilsby and Speeton are in the zone of Belemnites lateralis . Other marine fossils are Hemicidaris purbeckensis and Ostrea distonta ,
3599-417: Was given to the strata below the Cinder Bed in 1963 by Casey, who called the remaining section the Durlston Beds. These were elevated to the status of Lulworth and Durlston Formations by Thompson in 1975, who introduced the Purbeck Group as their parent unit. Cope and colleagues considered the Purbeck as a formation in 1980, naming it the Purbeck Limestone Formation, while El Shahat and West in 1993 called it
3660-422: Was uplifted and worn away to some extent prior to the deposition of the Purbeck Group. The building stones of the Purbeck Group have already been mentioned; the Purbeck or Paludina " marble ", a grey or greenish limestone full of shells, was formerly extensively employed in cathedrals and churches. Stone tiles or slats were once used locally for roofing from the Lower Purbeck of Portland, Swanage and Swindon. Gypsum
3721-403: Was used for the Armed Forces Memorial in Staffordshire , England. Designed by Liam O'Connor Architects and Planning Consultants, it was completed in 2007 at a cost of over £6 million and bears the names of over 16,000 service personnel of the British Armed Forces killed since the Second World War. Portland stone is recognised to be of a high quality, but is somewhat expensive. In the case of
SECTION 60
#1732780811386#385614