The Corallian Group or Corallian Limestone is a
geologic group
Geology () is a branch of natural science concerned with Earth and other astronomical objects, the features or rocks of which it is composed, and the processes by which they change over time. Modern geology significantly overlaps all other Eart ...
in
England
England is a country that is part of the United Kingdom. It shares land borders with Wales to its west and Scotland to its north. The Irish Sea lies northwest and the Celtic Sea to the southwest. It is separated from continental Europe b ...
. It is predominantly a coralliferous
sedimentary
Sedimentary rocks are types of rock (geology), rock that are formed by the accumulation or deposition of mineral or organic matter, organic particles at Earth#Surface, Earth's surface, followed by cementation (geology), cementation. Sedimentati ...
rock, laid down in the
Oxfordian stage of the
Jurassic
The Jurassic ( ) is a Geological period, geologic period and System (stratigraphy), stratigraphic system that spanned from the end of the Triassic Period million years ago (Mya) to the beginning of the Cretaceous Period, approximately Mya. The J ...
.
It is a hard variety of "
coral rag
Corals are marine invertebrates within the class Anthozoa of the phylum Cnidaria. They typically form compact colonies of many identical individual polyps. Coral species include the important reef builders that inhabit tropical oceans and sec ...
". Building stones from this geological structure tend to be irregular in shape. It is often found close to seams of
Portland Limestone
Portland stone is a limestone from the Tithonian stage of the Jurassic period quarried on the Isle of Portland, Dorset. The quarries are cut in beds of white-grey limestone separated by chert beds. It has been used extensively as a building sto ...
(e.g.
Abbotsbury
Abbotsbury is a village and civil parish in the English county of Dorset. The settlement is in the unitary authority of Dorset about inland from the English Channel coast. The village, including Chesil Beach, the swannery and subtropical g ...
in
Dorset
Dorset ( ; archaically: Dorsetshire , ) is a county in South West England on the English Channel coast. The ceremonial county comprises the unitary authority areas of Bournemouth, Christchurch and Poole and Dorset (unitary authority), Dors ...
,
England
England is a country that is part of the United Kingdom. It shares land borders with Wales to its west and Scotland to its north. The Irish Sea lies northwest and the Celtic Sea to the southwest. It is separated from continental Europe b ...
). It is a younger limestone than its near-neighbour, the
Oolitic, as found in the
Cotswolds
The Cotswolds (, ) is a region in central-southwest England, along a range of rolling hills that rise from the meadows of the upper Thames to an escarpment above the Severn Valley and Evesham Vale.
The area is defined by the bedrock of Jur ...
, in
Gloucestershire
Gloucestershire ( abbreviated Glos) is a county in South West England. The county comprises part of the Cotswold Hills, part of the flat fertile valley of the River Severn and the entire Forest of Dean.
The county town is the city of Gl ...
. It is laterally equivalent to and interfingers with units of the
Ancholme Group
The Ancholme Group is a geologic group in England. It preserves fossils dating back to the Jurassic period. It has previously been referred to as the Ancholme Clay Group. The group consists of predominantly grey, marine mudstone and silty muds ...
.
A ridge of Corallian Limestone rises above the
Vale of Avon and the
Thames Valley
The Thames Valley is an informally-defined sub-region of South East England, centred on the River Thames west of London, with Oxford as a major centre. Its boundaries vary with context. The area is a major tourist destination and economic hub, ...
in its
Oxfordshire
Oxfordshire is a ceremonial and non-metropolitan county in the north west of South East England. It is a mainly rural county, with its largest settlement being the city of Oxford. The county is a centre of research and development, primarily ...
stretch. The Oxfordshire Corallian ridge is an
escarpment
An escarpment is a steep slope or long cliff that forms as a result of faulting or erosion and separates two relatively level areas having different elevations.
The terms ''scarp'' and ''scarp face'' are often used interchangeably with ''escar ...
holding back the
hanging valley
A valley is an elongated low area often running between hills or mountains, which will typically contain a river or stream running from one end to the other. Most valleys are formed by erosion of the land surface by rivers or streams ove ...
that is the
Vale of White Horse
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 Nat ...
and its hardness forced the
River Thames
The River Thames ( ), known alternatively in parts as the The Isis, River Isis, is a river that flows through southern England including London. At , it is the longest river entirely in England and the Longest rivers of the United Kingdom, se ...
to take a wide northern detour, to cut through the low ridge at
Oxford
Oxford () is a city in England. It is the county town and only city of Oxfordshire. In 2020, its population was estimated at 151,584. It is north-west of London, south-east of Birmingham and north-east of Bristol. The city is home to the ...
. High points along the ridge are
Cumnor Hurst
Hurst Hill or Cumnor Hurst is a biological and geological Site of Special Scientific Interest west of Oxford in Oxfordshire. It is a Geological Conservation Review site.
The site is owned by All Souls College, Oxford, and its mosses and liverw ...
and
Wytham
Wytham ( ) is a village and civil parish on the Seacourt Stream, a branch of the River Thames, about northwest of the centre of Oxford. It is just west of the Western By-Pass Road, part of the Oxford Ring Road ( A34). The nearest village is G ...
Hill. The outcrop known as
Headington stone
Headington stone is a limestone from the Headington Quarry area of Oxford, England.
Geology
Around 160 million years ago, during the Late Jurassic period, Britain was located further south and was submerged beneath a subtropical sea. The warm c ...
was quarried at
Headington Quarry
Headington Quarry is a residential district of Oxford, England, located east of Headington and west of Risinghurst, just inside the Oxford ring road in the east of the city. To the south is Wood Farm. Today the district is also known colloquial ...
on the outskirts of Oxford and used for many of the historic
University
A university () is an institution of higher (or tertiary) education and research which awards academic degrees in several academic disciplines. Universities typically offer both undergraduate and postgraduate programs. In the United States, t ...
buildings there.
Hilly outcrops above this corallian ridge, composed of
Lower Greensand
The Lower Greensand Group is a geological unit present across large areas of Southern England. It was deposited during the Aptian and Albian stages of the Early Cretaceous. It predominantly consists of sandstone and unconsolidated sand that were ...
, occur at
Badbury Hill,
Faringdon
Faringdon is a historic market town in the Vale of White Horse, Oxfordshire, England, south-west of Oxford, north-west of Wantage and east-north-east of Swindon. It extends to the River Thames in the north; the highest ground is on the Rid ...
(Folly Hill) and
Boars Hill
Boars Hill is a hamlet southwest of Oxford, straddling the boundary between the civil parishes of Sunningwell and Wootton. Historically, part of Berkshire until the 1974 boundary changes transferred it to Oxfordshire.
History
The earliest ...
.
Softer sandy deposits occur within the Corallian, found for example at
Faringdon
Faringdon is a historic market town in the Vale of White Horse, Oxfordshire, England, south-west of Oxford, north-west of Wantage and east-north-east of Swindon. It extends to the River Thames in the north; the highest ground is on the Rid ...
,
Shellingford
Shellingford, historically also spelt Shillingford, is a village and civil parish about south-east of Faringdon in the Vale of White Horse in Oxfordshire, England. It was part of Berkshire until the 1974 Local Government Act transferred it to ...
and
Hatford
Hatford is a village and civil parish of some in the Vale of White Horse. It was part of Berkshire until the 1974 boundary changes transferred it to Oxfordshire.
Amenities
As Hatford is so small it has almost no amenities. Hatford has no vil ...
in
Oxfordshire
Oxfordshire is a ceremonial and non-metropolitan county in the north west of South East England. It is a mainly rural county, with its largest settlement being the city of Oxford. The county is a centre of research and development, primarily ...
, where the sands and gravels are extensively quarried.
The Corallian Limestone
aquifer
An aquifer is an underground layer of water-bearing, permeable rock, rock fractures, or unconsolidated materials (gravel, sand, or silt). Groundwater from aquifers can be extracted using a water well. Aquifers vary greatly in their characterist ...
is present at outcrop in
Yorkshire
Yorkshire ( ; abbreviated Yorks), formally known as the County of York, is a Historic counties of England, historic county in northern England and by far the largest in the United Kingdom. Because of its large area in comparison with other Eng ...
and in the
Cotswolds
The Cotswolds (, ) is a region in central-southwest England, along a range of rolling hills that rise from the meadows of the upper Thames to an escarpment above the Severn Valley and Evesham Vale.
The area is defined by the bedrock of Jur ...
. 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
The Wessex Basin is a petroleum-bearing geological area located along the southern coast of England and extending into the English Channel. The onshore part of the basin covers approximately 20,000 km2 and the area that encompasses the Englis ...
.
In England, Corallian Limestone is to be found in
Dorset
Dorset ( ; archaically: Dorsetshire , ) is a county in South West England on the English Channel coast. The ceremonial county comprises the unitary authority areas of Bournemouth, Christchurch and Poole and Dorset (unitary authority), Dors ...
,
Wiltshire
Wiltshire (; abbreviated Wilts) is a historic and ceremonial county in South West England with an area of . It is landlocked and borders the counties of Dorset to the southwest, Somerset to the west, Hampshire to the southeast, Gloucestershire ...
,
Oxfordshire
Oxfordshire is a ceremonial and non-metropolitan county in the north west of South East England. It is a mainly rural county, with its largest settlement being the city of Oxford. The county is a centre of research and development, primarily ...
,
Buckinghamshire
Buckinghamshire (), abbreviated Bucks, is a ceremonial county in South East England that borders Greater London to the south-east, Berkshire to the south, Oxfordshire to the west, Northamptonshire to the north, Bedfordshire to the north-ea ...
,
Cambridgeshire
Cambridgeshire (abbreviated Cambs.) is a Counties of England, county in the East of England, bordering Lincolnshire to the north, Norfolk to the north-east, Suffolk to the east, Essex and Hertfordshire to the south, and Bedfordshire and North ...
,
Lincolnshire
Lincolnshire (abbreviated Lincs.) is a county in the East Midlands of England, with a long coastline on the North Sea to the east. It borders Norfolk to the south-east, Cambridgeshire to the south, Rutland to the south-west, Leicestershire ...
and
Yorkshire
Yorkshire ( ; abbreviated Yorks), formally known as the County of York, is a Historic counties of England, historic county in northern England and by far the largest in the United Kingdom. Because of its large area in comparison with other Eng ...
.
The most noted scholar of the Corallian strata of England was the geologist
W.J. Arkell (1904–1958).
See also
*
List of types of limestone
This is a list of types of limestone arranged according to location. It includes both formal stratigraphic unit names and less formal designations.
Africa Egypt
*Tura limestone, used for the Great Pyramid casing stones
*Mokattam limestone; Gr ...
*
List of fossiliferous stratigraphic units in England
See also
*Lists of fossiliferous stratigraphic units in Europe
* Lists of fossiliferous stratigraphic units in the United Kingdom
References
*
{{DEFAULTSORT:Fossiliferous stratigraphic units in England
England
England is a country ...
References
External links
*
Geological groups of the United Kingdom
Geologic formations of England
Jurassic England
Limestone formations
Geography of Dorset
Jurassic System of Europe
Oxfordian Stage
{{England-stub