Corallian Group

Last updated

Corallian Group
Stratigraphic range: Oxfordian
~163–153  Ma
Cliff face west of Bran Point - geograph.org.uk - 23884.jpg
Corallian strata exposed near Bran Point
Type Group
Sub-units
Underlies Kimmeridge Clay Formation, Ampthill Clay, Faringdon Sand
Overlies Oxford Clay Formation, West Walton Formation
Thickness100 m (330 ft)
Lithology
Primary limestone, marl, sandstone, siltstone, mudstone.
Location
Region England
CountryFlag of the United Kingdom.svg  United Kingdom
Extent Dorset to Oxfordshire, North Yorkshire

The Corallian Group or Corallian Limestone is a geologic group in England. It is predominantly a coralliferous sedimentary rock, laid down in the Oxfordian stage of the Jurassic. [1] It is a hard variety of "coral rag". Building stones from this geological structure tend to be irregular in shape. It is often found close to seams of Portland Limestone (e.g. Abbotsbury in Dorset, England). It is a younger limestone than its near-neighbour, the Oolitic, as found in the Cotswolds, in Gloucestershire. It is laterally equivalent to and interfingers with units of the Ancholme Group.

Contents

A ridge of Corallian Limestone rises above the Vale of Avon and the Thames Valley in its Oxfordshire stretch. The Oxfordshire Corallian ridge is an escarpment holding back the hanging valley that is the Vale of White Horse and its hardness forced the River Thames to take a wide northern detour, to cut through the low ridge at Oxford. High points along the ridge are Cumnor Hurst and Wytham Hill. The outcrop known as Headington stone was quarried at Headington Quarry on the outskirts of Oxford and used for many of the historic University buildings there.

Hilly outcrops above this corallian ridge, composed of Lower Greensand, occur at Badbury Hill, Faringdon (Folly Hill) and Boars Hill.

Softer sandy deposits occur within the Corallian, found for example at Faringdon, Shellingford and Hatford in Oxfordshire, where the sands and gravels are extensively quarried.

The Corallian Limestone aquifer is present at outcrop in Yorkshire and in the Cotswolds. [2] In Yorkshire it consists of limestones and grits up to about 110 m thick, thinning to about 20 m towards the south of the region, where the limestones are progressively replaced by clay. It is typically well jointed and gives rise to numerous springs. Here it yields up to 15 L/sec. In the Cotswolds the aquifer is up to 40 m thick, give yields of 5 to 10 L/sec, with water quality becoming increasingly saline down dip as the aquifer becomes confined in the Wessex Basin.

In England, Corallian Limestone is to be found in Dorset, [3] Wiltshire, Oxfordshire, Buckinghamshire, Cambridgeshire, Lincolnshire and Yorkshire.

The most noted scholar of the Corallian strata of England was the geologist W.J. Arkell (1904–1958).

See also

Related Research Articles

River Derwent, Yorkshire River in Yorkshire, England

The Derwent is a river in Yorkshire in the north of England. It flows from Fylingdales Moor in the North York Moors National Park, east then southwards as far as its confluence with the River Hertford then westwards through the Vale of Pickering, south through Kirkham Gorge and the Vale of York, joining the River Ouse at Barmby on the Marsh. The confluence is unusual in that the Derwent converges on the Ouse at a shallow angle in an upstream direction.

Stanford in the Vale Human settlement in England

Stanford in the Vale is a village and civil parish in the Vale of White Horse about 3+12 miles (5.6 km) southeast of Faringdon and 5 miles (8 km) northwest of Wantage. It is part of the historic county of Berkshire, however since 1974, it has been administered as a part of Oxfordshire. The 2011 Census recorded the parish's population 2,093.

Vale of White Horse Non-metropolitan district in England

The Vale of White Horse is a local government district of Oxfordshire in England. It was historically a north-west projection of Berkshire. The area is commonly referred to as the 'Vale of the White Horse'. It is crossed by the Ridgeway National Trail in its far south, across the North Wessex Downs AONB at the junction of four counties. The northern boundary is defined by the River Thames. The name refers to Uffington White Horse, a prehistoric hill figure.

Faringdon Market town in Oxfordshire, England

Faringdon is a historic market town in the Vale of White Horse, Oxfordshire, England, 18 miles (29 km) south-west of Oxford, 10 miles (16 km) north-west of Wantage and 12 miles (19 km) east-north-east of Swindon. It extends to the River Thames in the north; the highest ground is on the Ridgeway in the south. Faringdon was Berkshire's westernmost town until the 1974 boundary changes transferred its administration to Oxfordshire. The civil parish is formally known as Great Faringdon, to distinguish it from Little Faringdon in West Oxfordshire. The 2011 Census gave a population of 7,121; it was estimated at 7,992 in 2019. On 1 February 2004, Faringdon became the first place in south-east England to be awarded Fairtrade Town status.

Chalk Group

The Chalk Group is the lithostratigraphic unit which contains the Upper Cretaceous limestone succession in southern and eastern England. The same or similar rock sequences occur across the wider northwest European chalk 'province'. It is characterised by thick deposits of chalk, a soft porous white limestone, deposited in a marine environment.

Geology of Dorset

Dorset is a county in South West England on the English Channel coast. Covering an area of 2,653 square kilometres (1,024 sq mi); it borders Devon to the west, Somerset to the north-west, Wiltshire to the north-east, and Hampshire to the east. The great variation in its landscape owes much to the underlying geology, which includes an almost unbroken sequence of rocks from 200 to 40 million years ago (Mya) and superficial deposits from 2 Mya to the present. In general, the oldest rocks appear in the far west of the county, with the most recent (Eocene) in the far east. Jurassic rocks also underlie the Blackmore Vale and comprise much of the coastal cliff in the west and south of the county; although younger Cretaceous rocks crown some of the highpoints in the west, they are mainly to be found in the centre and east of the county.

Purbeck Group

The Purbeck Group is an Upper Jurassic to Lower Cretaceous lithostratigraphic group 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.

A420 road

The A420 is a road between Bristol and Oxford in England. Between Swindon and Oxford it is a primary route.

Geology of England Overview of the geology of England

The geology of England is mainly sedimentary. The youngest rocks are in the south east around London, progressing in age in a north westerly direction. The Tees-Exe line marks the division between younger, softer and low-lying rocks in the south east and the generally older and harder rocks of the north and west which give rise to higher relief in those regions. The geology of England is recognisable in the landscape of its counties, the building materials of its towns and its regional extractive industries.

Geology of Gloucestershire

Gloucestershire is one of the most geologically and scenically diverse counties in England, with rocks from the Precambrian through to the Jurassic represented. These varying rock-types are responsible for the three major areas of the county, each with its own distinctive scenery and land-use - the Forest of Dean in the west, bordering Wales, the Cotswolds in the east, and in between, the Severn Vale.

Geology of Yorkshire

The Geology of Yorkshire in northern England shows a very close relationship between the major topographical areas and the geological period in which their rocks were formed. The rocks of the Pennine chain of hills in the west are of Carboniferous origin whilst those of the central vale are Permo-Triassic. The North York Moors in the north-east of the county are Jurassic in age while the Yorkshire Wolds to the south east are Cretaceous chalk uplands. The plain of Holderness and the Humberhead levels both owe their present form to the Quaternary ice ages. The strata become gradually younger from west to east.

Inferior Oolite

The Inferior Oolite is a sequence of Jurassic age sedimentary rocks in Europe. It was deposited during the Middle Jurassic. The Inferior Oolite Group as more recently defined is a Jurassic lithostratigraphic group in southern and eastern England. It has been variously known in the past as the Under Oolite, the Inferior Oolite, the Inferior Oolite Series and the Redbourne Group.

Geography of Dorset

Dorset is a county located in the middle of the south coast of England. It lies between the latitudes 50.512°N and 51.081°N and the longitudes 1.682°W and 2.958°W, and occupies an area of 2,653 km2. It spans 90 kilometres (56 mi) from east to west and 63 kilometres (39 mi) from north to south.

Cleeve Common

Cleeve Common is a 455-hectare (1,120-acre) biological and geological Site of Special Scientific Interest in Gloucestershire, England, notified in 1974. It is looked after by a small charity called Cleeve Common Trust, formally Cleeve Common Board of Conservators.

Hornsleasow Quarry Site of Special Scientific Interest in Gloucestershire

Hornsleasow Quarry is a 3.5-hectare (8.6-acre) geological Site of Special Scientific Interest in Gloucestershire, notified in 1974. The site is listed in the 'Cotswold District' Local Plan 2001-2011 as a Regionally Important Geological Site (RIGS).

The Natural Areas of England are regions, officially designated by Natural England, each with a characteristic association of wildlife and natural features. More formally, they are defined as "biogeographic zones which reflect the geological foundation, the natural systems and processes and the wildlife in different parts of England...".

A National Character Area (NCA) is a natural subdivision of England based on a combination of landscape, biodiversity, geodiversity and economic activity. There are 159 National Character Areas and they follow natural, rather than administrative, boundaries. They are defined by Natural England, the UK government's advisors on the natural environment.

Midvale Ridge

The Midvale Ridge is a natural region in South Central England formed by a band of low-lying limestone hills that run from southeast to northwest from the Vale of Aylesbury to Swindon. It has been designated as National Character Area 109 by Natural England, the UK Government's advisors on the natural environment.

The geology of the North York Moors National Park in northern England is provided largely by a thick southerly dipping sequence of sedimentary rocks deposited in the Cleveland Basin during the Jurassic Period. A series of ice ages during the Quaternary period has left a variety of glacial deposits, particularly around the margins of the National Park.

References

  1. "Corallian Group". The BGS Lexicon of Named Rock Units. British Geological Survey. Retrieved 14 December 2014.
  2. "The Corallian Limestone as an aquifer". British Geological Survey. Retrieved 9 December 2016.
  3. "Fifehead Wood Management Plan 2010 - 2015" (PDF). Woodland Trust. p. 6. Retrieved 10 April 2013.[ permanent dead link ]