The Blisworth Limestone Formation is a

geological formation A geological formation, or simply formation, is a body of rock having a consistent set of physical characteristics (lithology) that distinguishes it from adjacent bodies of rock, and which occupies a particular position in the layers of rock expo ...

primarily consisting of

limestone Limestone ( calcium carbonate ) 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 . Limestone forms wh ...

deposited during the

Bathonian In the geologic timescale the Bathonian is an age and stage of the Middle Jurassic. It lasted from approximately 168.3 Ma to around 166.1 Ma (million years ago). The Bathonian Age succeeds the Bajocian Age and precedes the Callovian Age. St ...

stage of the

Middle Jurassic The Middle Jurassic is the second epoch of the Jurassic Period. It lasted from about 174.1 to 163.5 million years ago. Fossils of land-dwelling animals, such as dinosaurs, from the Middle Jurassic are relatively rare, but geological formations ...

, found in 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 ...

ridge which extends north and south through

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 ...

. It was laid down in the shallows of the Jurassic sea and is part of the more widely defined

Great Oolite Group The Great Oolite Group is a Middle Jurassic stratigraphic unit that outcrops in southern England. It consists of a complex set of marine deposits primarily mudstone and bioclastic ooidal and fine grained limestone, deposited in nearshore to shel ...

. It was previously known as the Great Oolite Limestone, White Limestone and the Snitterby Limestone Formation. It is the lateral equivalent of the

White Limestone Formation The White Limestone Formation is a Bathonian geologic formation in the United Kingdom, dating to the Middle Jurassic, 168.3 to 166.1 million years ago. Fossil sauropod tracks have been reported from the formation.Weishampel, et al. (2004). "Din ...

From the Jurassic ridge it extends eastwards below the later deposits and in the North Sea terminology, it is part of the West Sole Group. (Cameron p. 74)

Formation

The Blisworth limestone lies above the Upper Estuarine Series of strata. The latter was formed close to the coast where rivers flowed from the

London-Brabant Island The London-Brabant Massif or London-Brabant Platform is, in the tectonic structure of Europe, a structural high or massif that stretches from the Rhineland in western Germany across northern Belgium (in the province of Brabant) and the North Sea ...

. The land sank a little in relation to the sea so the site lay a little further offshore. In the hot, shallow sea, the water partially evaporated so that the dissolved calcium carbonate (CaCO₃) was

precipitated In an aqueous solution, precipitation is the process of transforming a dissolved substance into an insoluble solid from a super-saturated solution. The solid formed is called the precipitate. In case of an inorganic chemical reaction leading ...

onto minute nuclei to form tiny spheres which together resemble hard fish roe. This is composed of eggs; hence the name oölite. The process goes on today in the seas off the

Bahamas The Bahamas (), officially the Commonwealth of The Bahamas, is an island country within the Lucayan Archipelago of the West Indies in the North Atlantic. It takes up 97% of the Lucayan Archipelago's land area and is home to 88% of the archi ...

(Kirkaldy p. 59). Much of it also contains marine shells, notably of oyster. Subsequently, the site was submerged less deeply so that the overlying Blisworth Clay was deposited in brackish conditions. (Gallois p. 20) The stratum is known as Blisworth Limestone because it was first studied at Blisworth in

Northamptonshire Northamptonshire (; abbreviated Northants.) is a county in the East Midlands of England. In 2015, it had a population of 723,000. The county is administered by two unitary authorities: North Northamptonshire and West Northamptonshire. It is ...

when the Blisworth tunnel was being dug for what is now called the

Grand Union Canal The Grand Union Canal in England is part of the British canal system. It is the principal navigable waterway between London and the Midlands. Starting in London, one arm runs to Leicester and another ends in Birmingham, with the latter s ...

. The tunnel finally opened in 1805.

Occurrence

Blisworth limestone is a generally thin but widely spread deposit in eastern England. It becomes thicker as one progresses southward from north Lincolnshire or westward from Norfolk. In the

King's Lynn King's Lynn, known until 1537 as Bishop's Lynn and colloquially as Lynn, is a port and market town in the borough of King's Lynn and West Norfolk in the county of Norfolk, England. It is located north of London, north-east of Peterborough, ...

district, it is a shelly oolitic limestone 1 to 2 m thick. At Wiggenhall it is around 190m below mean sea level (OD) and at Tydd St Mary, around 140m. (Gallois) At

Bourne, Lincolnshire Bourne is a market town and civil parish in the South Kesteven district of Lincolnshire, England. It lies on the eastern slopes of the limestone Kesteven Uplands and the western edge of the Fens, 11 miles (18 km) north-east of Stamford, 12 mi ...

, at the eastern edge of the Jurassic ridge, it is around 15m below OD. (BGS sheet 144) It is exposed at the surface around the valleys of the East and West Glen rivers (

River Glen, Lincolnshire The River Glen is a river in Lincolnshire, England with a short stretch passing through Rutland near Essendine. The river's name appears to derive from a Brythonic Celtic language but there is a strong early English connection. Naming In ...

) in which vicinity it is 2.4 to 4.8 metres thick. (BGS sheet 143). Its exposure continues southward in a similar relationship to the Jurassic ridge, to the west of

Peterborough Peterborough () is a cathedral city in Cambridgeshire, east of England. It is the largest part of the City of Peterborough unitary authority district (which covers a larger area than Peterborough itself). It was part of Northamptonshire until ...

. (BGS sheet 157) Around

Towcester Towcester ( ) is an affluent market town in Northamptonshire, England. It currently lies in West Northamptonshire but was the former administrative headquarters of the South Northamptonshire district council. Towcester is one of the olde ...

it reaches a thickness of 9m. (Hains & Horton p. 85)

Application

Blisworth limestone is used as a building material, in particular as blocks of stone.

Lilford Hall Lilford Hall is a Grade I listed Jacobean stately home in Northamptonshire in the United Kingdom. The 100-room house is located in the eastern part of the county, south of Oundle and north of Thrapston. History It was started in 1495 as a Tudor ...

in Northamptonshire is made from Blisworth limestone.

References

*British Geological Survey, 1:50,00 Series. (1992) *Cameron, T.D.J. ''et al.'' ''The geology of the southern North Sea'' (1992) *Gallois, R.W. ''Geology of the country around King's Lynn and The Wash'' (1994) *Hains, B.A. & Horton, A. ''British Regional Geology: Central England'' 3rd edn. (1969) *Kirkaldy, J.F. ''Field Geology'' (1988)

Formation

Occurrence

Application

References

See also