Important Geological Sites
Shotley Quarry on the Bulwick Estate
Important Geological Sites
By Ian Clarke
Northamptonshire RIGS Coordinator
Northamptonshire is not famous for its rock exposures and Rockingham Forest is no exception. Since iron ore quarrying ceased in the late 1970s, the area's geology is largely hidden below the surface or displayed as building stone. One way of conserving and highlighting what lies beneath is through Regionally Important Geological Sites (RIGS).
Every RIGS (also sometimes known as a Local Geological Site) is assessed on four criteria: scientific, educational, historical, and aesthetic. Northamptonshire’s sites cover the whole range of Northamptonshire’s Lower and Middle Jurassic geology, from the Marlstone Rock and Upper Lias in the west of the county, through the Northampton Sand Ironstone belt around Northampton, Wellingborough, Kettering and Corby, and up to the Lincolnshire Limestones of the north east area. Many of the ironstone sites are reminders of Northamptonshire’s vanished iron ore extraction industry. The South Northants area still needs further exploration to identify potential sites.
RIGS status, unlike Sites of Special Scientific Interest, confers no statutory protection to a site, but landowners and local authorities are notified in the hope that these sites can be left visible and accessible for further study by geologists. Many of the sites also provide useful wildlife habitats. We are grateful to the Wildlife Trust’s Northamptonshire Biodiversity Records Centre for its help in record keeping and administering Northamptonshire’s RIGS.
In December 2018, Dr Diana Sutherland retired from her long-held voluntary post as guardian of Northamptonshire’s RIGS. Since then, a group of four volunteers from the Nene-Tees Branch of the Open University Geological Society have got together to pick up Diana’s work. We'd very much welcome help from anyone else with an interest in geology. Please get in touch.
There are over 70 RIGS in Northamptonshire and, as most of them have not been looked at for 10-15 years, the volunteer group is concentrating on updating the condition monitoring forms for the best, most easily accessible sites. So far, we have visited and updated the records of about 15 sites in the Northampton, Corby, Rothwell, and Daventry areas. Problems that we have encountered include sites that are badly overgrown with vegetation and difficulty in identifying and contacting landowners.
An example of what can be done at a RIGS is at Irchester Country Park. Here, in conjunction with Northamptonshire County Council, a successful Heritage Lottery bid enabled the provision of the Ironstone Heritage Trail, a viewing platform, and some clearance of the Wembley Pit face, making a very valuable educational facility and useful geoconservation.
Geological maps
Did you know that geological maps are available online. Go to the British Geological Survey's Geology Viewer
and you'll be able to produce detailed maps of the area like the example shown on the left.
There is more to read about the quarried landscapes of Rockingham Forest here.
RIGS in the Rockingham Forest
There are several RIGS within the Rockingham Forest area and three of the most accessible ones are described below.
Prior's Hall, Corby
Lower and Upper Lincolnshire Limestone.
This site is one of the few remaining exposures of the very extensive iron ore quarry system in the Corby area. After major expansion from 1941, Priors Hall became one of the deepest and largest ironstone quarries in the area. Work ceased in 1979. (Test this link please)
The rock exposed in the cliff at Prior’s Hall is Lincolnshire Limestone, a Middle Jurassic rock which was deposited on top of the Northampton Sand. It had to be removed in order to reach the ironstone. At the base of the cliff is a hard limestone “pavement” used as solid ground by machinery during quarrying. The Lincolnshire Limestone is an important rock in its own right, providing good quality building stone. Weldon stone is a particularly fine example, being used locally eg at Kirby Hall and the gatehouse at Rockingham Castle, and further afield, for example, at King’s College, Cambridge.
East Carlton Countryside Park
An exposure of the Northampton Sand Ironstone
This was the raw material for Corby’s iron and steel industry for over 50 years. Some beds contain around 25-30% iron, which was increased to 40% by “calcining”---heating the ironstone to a high temperature for several weeks at a time to drive off impurities.
The ironstone formed in the Middle Jurassic between about 174 and 170 million years ago. It is a sandy, sideritic ironstone, greenish grey when fresh, and weathers to brown limonitic sandstone, often with boxstone structure.
Formed in a shallow sea, the Northampton Sand Formation includes bands of mudstone and limestone and has a fossil fauna of bivalves, brachiopods, and ammonites. The fossils are uncommon in weathered sections. Shell fragments and worm burrows can be seen in some of the stone blocks of the kitchen building in the park.
Priors Hall. Grid reference SP931901
Find out more about Prior's Hall here on the Places to Visit page. And join me for a free guided tour of the site on 21st February 2025 - details and booking here
East Carlton. Grid reference SP837894
Visit this page of North Northants Council's website for more details and a map of East Carlton Countryside Park
Building stone at East Carlton, probably taken from the quarry
King's Cliffe Park
Here there are the remains of medieval quarries which worked Lincolnshire Limestone (King's Cliffe stone) which was used in a number of important buildings locally and further away. King’s Cliffe stone is one of the several varieties of Lincolnshire Limestone and has been an important building stone. King’s Cliffe stone itself has its own variations, from a porous oolite with some shell fragments and a cross-bedded, banded texture, to a coarsely shelly, spar-cemented rock with fossils and small bits of limestone.
King’s Cliffe stone was used locally at Fotheringhay bridge, Apethorpe Church tower, and in many of King’s Cliffe’s houses. It was also used in important buildings further afield, including King’s College Chapel, Cambridge (1460), Trinity College, Cambridge, and Burghley House., Stamford.
The village produced two families of master masons, the Thorpes and the Frisbys. Thomas Thorpe (the third of three generations of Thomases) was the master mason for Kirby Hall near Corby, and his son John went on to become an architect and surveyor for royal estates. There is a memorial, dated 1623, to the Thorpes in King’s Cliffe church.
King’s Cliffe Park is an historic quarry, now managed as farm grassland but still has small exposures of Lincolnshire Limestone along with the hills and hollows left by medieval quarrying.
KIng's Cliffe Park. Grid reference TL015972
You can access this site from the public footpath at Huskisson's Lodge TL014978, You have to walk down the gravel drive to get to a stile.
More information about the quarrying around King's Cliffe can be found on the KIng's Cliffe Heritage website. Try typing "quarry" in the site's search box
For further information about Regionally Important Geological Sites please contact me :
Ian J Clarke
Northamptonshire RIGS Coordinator
01327 705114
Find out more about The Deeps,
Collyweston on the Places to Visit page.
Some more RIGS in the Rockingham Forest area
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The Deeps Collyweston, a Wildlife Trust Local Nature Reserve, TF003037.
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Rothwell East, SP812819.
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Rothwell Gullet, a Wildlife Trust Local Nature Reserve, SP808818.
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Duddington Quarry, SK999012. Still a working quarry,
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Shotley Quarry, approx SP937970, just off a public footpath on the Bulwick Estates.
There are one or two others but they are either inaccessible because of vegetation or they've been obliterated by new road building.
The Deeps Collyweston. Grid reference TF003037
Ian Clarke worked for over 30 years in Northants' public libraries, mostly in Corby and Daventry. His interest in geology developed later in life and he achieved a BSc with the Open University, studying a number of Earth Science courses. He is an active member of the Nene-Tees branch of the Open University Geological Society, participating in and helping to organise field trips.
Ian's favourite geological moment was being able to visit one of geology’s iconic sites, the Burgess Shale, high up in the Canadian Rockies. Here are found remarkable fossils of strange marine creatures from around 510-505 million years ago.