Lincolnshire limestone
Encyclopedia
The Lincolnshire limestone is a feature of the Inferior Oolite Series
of the (Bajocian
) Middle Jurassic
strata of eastern England
. It was formed around 165 million years ago, in a shallow, warm sea on the margin of the London Platform and has estuarine beds
above and below it. The maximum known thickness is 40.2 metres, at around TF9730, while four kilometres further west it is 18.3 metres thick at its outcrop in the upper Witham
valley. It fades out in the south, around Kettering
in Northamptonshire
.
There are two sub-divisions, the Upper and Lower Lincolnshire limestones respectively. The dividing marker is the 'Crossi' bed which is distinguished by the fossils of Acanthothris crossi it contains. The Crossi bed forms the top of the Lower Lincolnshire limestone. The bottom of the Lower Lincolnshire limestone has some of the characteristics of the underlying Lower Estuarine Series
, in that it tends to contain more than usual amounts of sand. A stone from this part of the formation which was commercially exploited is the Collyweston stone slate
which was used for roofing for several centuries. It is now largely replaced in new work by concrete imitations.
Much of the rest of the Lower Lincolnshire limestone is oolitic. It formed in warm, shallow seas where evaporation concentrated the dissolved calcium carbonate and wave action rolled the precipitated material into tiny balls. It takes its name from its similarity to the hard roe of fish.
Oolite
Oolite is a sedimentary rock formed from ooids, spherical grains composed of concentric layers. The name derives from the Hellenic word òoion for egg. Strictly, oolites consist of ooids of diameter 0.25–2 mm; rocks composed of ooids larger than 2 mm are called pisolites...
of the (Bajocian
Bajocian
In the geologic timescale, the Bajocian is an age or stage in the Middle Jurassic. It lasted from approximately 171.6 Ma to around 167.7 Ma . The Bajocian age succeeds the Aalenian age and precedes the Bathonian age....
) Middle Jurassic
Jurassic
The Jurassic is a geologic period and system that extends from about Mya to Mya, that is, from the end of the Triassic to the beginning of the Cretaceous. The Jurassic constitutes the middle period of the Mesozoic era, also known as the age of reptiles. The start of the period is marked by...
strata of eastern England
England
England is a country that is part of the United Kingdom. It shares land borders with Scotland to the north and Wales to the west; the Irish Sea is to the north west, the Celtic Sea to the south west, with the North Sea to the east and the English Channel to the south separating it from continental...
. It was formed around 165 million years ago, in a shallow, warm sea on the margin of the London Platform and has estuarine beds
Estuary
An estuary is a partly enclosed coastal body of water with one or more rivers or streams flowing into it, and with a free connection to the open sea....
above and below it. The maximum known thickness is 40.2 metres, at around TF9730, while four kilometres further west it is 18.3 metres thick at its outcrop in the upper Witham
River Witham
The River Witham is a river, almost entirely in the county of Lincolnshire, in the east of England. It rises south of Grantham close to South Witham, at SK8818, passes Lincoln at SK9771 and at Boston, TF3244, flows into The Haven, a tidal arm of The Wash, near RSPB Frampton Marsh...
valley. It fades out in the south, around Kettering
Kettering
Kettering is a market town in the Borough of Kettering, Northamptonshire, England. It is situated about from London. Kettering is mainly situated on the west side of the River Ise, a tributary of the River Nene which meets at Wellingborough...
in Northamptonshire
Northamptonshire
Northamptonshire is a landlocked county in the English East Midlands, with a population of 629,676 as at the 2001 census. It has boundaries with the ceremonial counties of Warwickshire to the west, Leicestershire and Rutland to the north, Cambridgeshire to the east, Bedfordshire to the south-east,...
.
There are two sub-divisions, the Upper and Lower Lincolnshire limestones respectively. The dividing marker is the 'Crossi' bed which is distinguished by the fossils of Acanthothris crossi it contains. The Crossi bed forms the top of the Lower Lincolnshire limestone. The bottom of the Lower Lincolnshire limestone has some of the characteristics of the underlying Lower Estuarine Series
Lower Estuarine Series
The Lower Estuarine Series, also called in more modern publications, the Grantham Formation, is a relatively complex but generally thin set of geological strata which are usually considered as a group. It forms a lower part of the Inferior Oolite Series, which lies in the Middle Jurassic...
, in that it tends to contain more than usual amounts of sand. A stone from this part of the formation which was commercially exploited is the Collyweston stone slate
Collyweston stone slate
Collyweston stone slate is a traditional roofing material found in England.It is not a proper slate but a limestone found in narrow beds. The slates are quarried near the village of Collyweston in Northamptonshire, near Stamford and close to the borders of Lincolnshire and Rutland. It is...
which was used for roofing for several centuries. It is now largely replaced in new work by concrete imitations.
Much of the rest of the Lower Lincolnshire limestone is oolitic. It formed in warm, shallow seas where evaporation concentrated the dissolved calcium carbonate and wave action rolled the precipitated material into tiny balls. It takes its name from its similarity to the hard roe of fish.