Irchester Country Park preserves the last face of Wembley Pit, where Jurassic ironstone, rooted clays and fossiliferous limestone record changing seas and coastal wetlands. Brachiopods, bivalves and other marine fossils can be studied alongside the quarry’s industrial history, with managed paths and viewpoints providing the safest way to explore.
FIND FREQUENCY: ♦♦♦ – Brachiopods and bivalves are the principal recorded finds. What can be seen depends on exposure; obtain permission before collecting.
CHILDREN: ♦♦ – The wider park has family facilities, but the steep quarry slopes and rockfall areas are unsuitable for unsupervised exploration.
ACCESS: ♦♦♦ – Pay-and-display parking and waymarked park trails. Use the managed viewpoints and follow current barriers and signs.
TYPE: – Disused ironstone quarry within a country park and locally designated geological site. Public entry does not give permission to remove fossils.
DIRECTIONS
♦ From the A45/A509 junctions near Wellingborough, follow signs for Irchester Country Park and turn onto Gypsy Lane. The park entrance is on Gypsy Lane, Little Irchester; use the signed entrance rather than looking for a separate quarry entrance.
♦ The council lists the park address as NN29 7DL and gives NN29 7DJ specifically for parking satnavs. Pay-and-display parking is available; the published charge is £3.50 for up to 12 hours, with coin, card and contactless payment or PayByPhone location 810062. Check the machine for current charges.
♦ The upper car park is open all day. The lower car park has seasonal closing times and vehicles left after closing can be locked in overnight. Check the signs on arrival, especially for an afternoon visit.
♦ Inside the park, follow the orange waymarkers for the 3.8 km Ironstone Heritage Trail and its quarry interpretation and viewpoints. Use the managed paths; do not descend a steep quarry slope or cross a barrier to reach fallen rock.
♦ Ref: 52.283761°N, 0.666851°W
FOSSIL HUNTING
Begin by looking at the quarry from the heritage viewpoints. The lower ironstone, the softer sandy and clay-rich slopes and the pale limestone higher in the face represent different parts of the succession. This matters when identifying a fossil: a shell in a pale limestone block should not automatically be labelled as coming from the ironstone simply because this was an ironstone quarry. Check with the country parks team before collecting or using tools, and follow their instructions about any area that may be entered.
Brachiopods and bivalves are the most frequently recorded fossils, particularly in fallen limestone blocks; some were also found loose on the quarry floor. Other recorded finds include gastropods, sea urchins, ammonites, nautiluses, corals and fish teeth. These broader records have no secure bed-by-bed attribution, so concentrate on the shelly limestone rather than relying on finding an ammonite or vertebrate fossil.
Where rock can be examined safely and with permission, start with naturally weathered surfaces. A hand lens helps distinguish a complete shell outline from the many broken shell fragments in the limestone. Photograph both the fossil and its surrounding matrix before trying to identify it; a view of the bedding and nearby shells is often more useful than a close-up alone. Avoid breaking a block merely to expose a better-looking specimen.
The Wellingborough Limestone Member has its own documented association: layered oyster beds with Praeexogyra hebridica, sandy and shelly limestone containing Placunopsis, and the sea urchin Acrosalenia. These records identify a genuine marine component within the Rutland Formation. Compare oyster-rich surfaces, other shell-rich limestone and fine wavy-banded limestone separately rather than treating every pale block as the same bed.
The wavy bands in parts of the Wellingborough Limestone are described as algal limestone. They record biological activity within the sediment rather than the outline of a large shell. Rootlets and dark carbonaceous layers in the lower Rutland sands and clays provide a different kind of evidence, showing where vegetation grew or plant matter accumulated. These features are worth recording in place and are easily lost if a weathered surface is scrubbed or broken.
Higher in the succession, the marly, striped limestone at the base of the Blisworth Limestone contains the brachiopod Kallirhynchia sharpi. An Irchester Country Park example is documented by Northampton Museums. Keep its source bed distinct from the oyster-bearing Wellingborough Limestone below: both are fossiliferous, but they belong to different levels and record different stages in the return of the sea.
A dinosaur footprint cast found in the park in early 2024 adds a rare trace fossil to this predominantly shelly record. The raised cast is sediment that filled an original impression, rather than a bone or a carved footprint. The museum reports the cast as approximately 1 m wide, a measurement of the fossil object rather than an estimate of the dinosaur’s size. Further casts have also been reported. The maker has been tentatively linked to Megalosaurus, but a secure species identification and precise measured horizon are not established by the museum account. Photograph a possible footprint in place, include a scale without touching the surface, and report it to the park team rather than attempting to move it.
Loose material may have moved down from more than one bed or have been disturbed during quarrying, so location alone cannot recover its original horizon. For any authorised specimen, record the date, exact permitted location, rock type and whether it was loose or in place. The shell beds and plant-bearing layers are valuable together: leaving representative features undamaged helps the next visitor understand the whole succession.
Editorial credit: Jon Trevelyan (2014).
Significant discoveries, geological research and conservation milestones at Irchester Country Park.
1924 – Wembley Pit workings begin
The 2018 excursion account dates the Wembley workings from 1924. The preserved quarry face and surrounding spoil record the large-scale extraction that followed. Published sources disagree over the final cessation year, so the end of working is retained more cautiously as the 1940s.
1940s – Ironstone quarrying ends
Commercial extraction ended during the 1940s, leaving the final gullet unfilled. The exposed ironstone and its overlying sands, clays and limestones survived alongside spoil ridges and calcining remains, preserving both a geological section and evidence of how the quarry worked.
1967 – A measured Blisworth section is documented
Hugh Torrens’s 1967 work documented a measured Blisworth Limestone section at the north end of the quarry during his research on the Midlands Great Oolite limestones. This date belongs to the published research record; the later account does not independently establish when the field measurement was made.
1971 – The quarry becomes a country park
Northamptonshire County Council acquired the disused quarry and woodland, including the calcining banks and locomotive sheds. The transition to a public park preserved the industrial landscape while creating opportunities to study and explain the geological section.
1972–1973 – Quarry beds and fossils studied in detail
John Hudson, Roy Clements and Diana Sutherland worked with an adult-education group to measure sections and record fossils. Photographs from 1973 show the contrasting east and west faces, including the prominent Wellingborough Limestone rib and the Blisworth Limestone wall exceeding 5 m at the north-east end.
1982 – A geological guide to the quarry face
Diana Sutherland and John Hudson produced a geological guide devoted to the Country Park quarry face. It drew the site’s stratigraphy and field observations together for visitors and became an important reference for later interpretation of the surviving exposure.
2000 – Regional geological designation approved
Irchester Country Park was approved for designation as a Regionally Important Geological Site. Recognition of the quarry’s varied Jurassic rocks, industrial history and educational potential provided a basis for later conservation and interpretation work.
2008 – A geological management plan prepared
Northamptonshire RIGS Group submitted a site management plan to the county council. It identified the need to restore visibility of the geology and improve interpretation, helping to establish the case for a larger heritage project.
April 2014 – Heritage project approved
The £130,000 project Protecting and Interpreting a Real Jurassic Park was approved. Geological conservation was brought together with wildlife and industrial heritage, supporting a coordinated programme of site management and visitor interpretation.
June 2017 – New trail and quarry viewpoints celebrated
A public event marked the completion of the three-year heritage project. The Ironstone Heritage Trail, quarry viewing platform, information panels and outdoor teaching area connected the exposed succession with the history of ironstone extraction.
Early 2024 – Dinosaur footprint cast found
A dinosaur footprint cast was found in the Country Park, with two further casts subsequently reported. These traces record an animal crossing soft sediment before its impression was filled and preserved. The trackmaker has been tentatively associated with a large meat-eating dinosaur, but its precise species and position in a measured quarry section remain uncertain.
GEOLOGY
Wembley Pit was excavated for iron ore, leaving a long final quarry face through the Middle Jurassic rocks. From bottom to top the principal units are the Northampton Sand Formation, the Rutland Formation and the Blisworth Limestone Formation. Diana Sutherland’s account describes a face through about 20 m of strata. Its lower ironstone was the economic target, whereas much of the sand, clay and limestone above it was removed as overburden, leaving the spoil ridges that now shape the wooded park. Colman’s 2018 excursion report describes the surviving face as over 1 km long; that historical observation does not establish a currently accessible length.
The Northampton Sand belongs to the Inferior Oolite Group and is Aalenian in age. Iron accumulated in a shallow marine setting within small grains and the material cementing them together. Weathering changes the fresh iron-rich rock towards brown, rusty sandstone and ironstone. The younger succession does not follow without interruption: erosion and non-deposition created a substantial break before the Great Oolite Group accumulated above it.
At Irchester, the lower Great Oolite rocks are the Rutland Formation. Its sandy basal beds, now assigned to the Stamford Member, were historically confused with the older Lower Estuarine Series. The modern interpretation removes that apparent extra unit: the Grantham Formation and Lincolnshire Limestone are absent from the local succession. Rootlet-bearing sands and clays, carbonaceous layers and overlying marine shell beds record repeated changes between vegetated coastal ground and shallow water.
The Wellingborough Limestone Member marks a particularly clear marine interval within these varied Rutland deposits. Its resistant limestone made a prominent ledge in the west-end face, contrasting with the softer clay slopes. Oyster-rich beds, sandy shelly limestone and wavy algal bands preserve different conditions within this interval. Dark rooted clays above it show that marine conditions did not persist continuously.
A more widespread marine incursion eventually produced the Blisworth Limestone. At the park its incoming marly beds contain Kallirhynchia sharpi, above which the limestone forms the upper quarry wall. The wall was more than 5 m high at the north-east end in the 1973 record. The contrast between strong limestone and softer underlying clays helps explain the uneven face, scree and dangerous falling blocks; historical photographs and measurements do not establish which beds are safely accessible today.
Detailed Middle Jurassic geology of Irchester Country Park: the ironstone, erosional break, rooted Rutland beds and fossiliferous limestones.
Locality and level of detail
This account follows the Country Park quarry, historically Wembley Pit, from older to younger rocks. The detailed Old Lodge Pit section published for a separate quarry about 1 km to the south must not be read as a numbered log of this face. The surviving park descriptions support the horizons below, but not a complete numbered bed-by-bed subdivision or a uniform thickness for the whole face.
INFERIOR OOLITE GROUP
Northampton Sand Formation
Basal ironstone
The ironstone at the base of the Country Park succession is Aalenian. It is an iron-rich marine sandstone and ooidal ironstone; the wider formation contains berthierine-rich grains and sideritic cement, with weathering producing brown iron oxides. The small grains and iron-rich cement help distinguish this rock from the paler Great Oolite limestones above. Formation-wide subdivisions and their thicknesses cannot be assumed to form a complete exposed park log.
Erosional break above the ironstone
The upper surface of the Northampton Sand is separated from the Rutland Formation by a major stratigraphical break. The district lay close to the Anglo-Brabant landmass, where uplift, emergence and erosion removed or prevented the preservation of intervening deposits. Neither the Grantham Formation nor the Lincolnshire Limestone is represented as a separate unit in this park succession; their absence is part of its geological history.
GREAT OOLITE GROUP
Rutland Formation
Changing coastal conditions and historical terminology
The Rutland Formation records a changing coastal environment rather than a single continuous marine limestone. Its lower sandy deposits, darker clays, rooted surfaces and limestone intervals reflect shifts between plant-covered ground, coastal wetlands and marine incursions. The formation was historically called the Upper Estuarine Series. Bradshaw’s 1978 regional work clarified its changing sedimentary environments, but a regional scheme of named depositional rhythms is not a measured inventory of all the beds present at this park.
Stamford Member
Lower sands, rooted layers and carbonaceous horizons
The lower sandy beds belong to the Stamford Member of the Rutland Formation. Sutherland explains that deposits previously mapped here as the Lower Estuarine Series, subsequently called the Grantham Formation, were reassigned to this younger member. The park description records sandy beds with rootlet horizons and black carbonaceous layers, representing plant-bearing near-shore environments. Exact thicknesses and a numbered subdivision are not established by the accessible park account.
Wellingborough Limestone Member
Oyster-bearing limestone beds
The member forms the conspicuous resistant limestone rib in the historical west-end quarry face. It is part of the Rutland Formation, below the higher Blisworth Limestone. Layered beds containing the oyster Praeexogyra hebridica record marine shell accumulation. The published park account identifies this oyster-bearing component without assigning the layers bed numbers or individual measured thicknesses.
Wavy-banded algal limestone
Other limestone within the member displays fine, wavy algal banding. A photograph taken in 1976 records this feature at the position of a later heritage viewpoint. These laminated surfaces are a distinct part of the local evidence and should not be reduced to a general shell-bed description. The photograph records the former exposure, without establishing that the same surface is visible today.
Sandy and shelly limestone
Sandy to shelly limestone varieties contain the bivalve Placunopsis and the echinoid Acrosalenia. Together with the oyster beds and algal limestone, these document lithological and biological variation within the member. The available account does not specify a numbered internal order for every variety, so they are described as recorded components rather than invented consecutive beds.
Upper Rutland Formation: dark rooted clays
Dark clay beds above the Wellingborough Limestone contain rootlet horizons, indicating intervals of vegetated ground after the marine limestone accumulated. These are upper Rutland deposits, not an extension of the limestone member. Larger tree roots are also discussed in the regional account, but its illustrated 2.7 m root comes from Finedon Hill Quarry and is not an Irchester park measurement.
Blisworth Limestone Formation
Blisworth member names and the park reference section
The 2006 BGS district memoir uses Roade and Irchester members within the Blisworth Limestone. The 2011 Middle Jurassic framework retains Roade but treats Irchester Member as redundant in favour of Ardley Member. The BGS Lexicon’s Irchester entry nevertheless still lists the Country Park as a reference section, with the separate Old Lodge Pit as its type section. These sources therefore preserve differing nomenclature. The member names do not supply a new measured boundary in the park, and Old Lodge’s 6.15 m type section must not be transferred to this face.
Basal marine clays and marly limestone
At the top of the west-end succession, marine clays pass into striped, marly limestone containing Kallirhynchia sharpi. These beds mark the incoming Blisworth Limestone and the establishment of more widespread shallow-marine conditions. The museum’s park specimen independently records this brachiopod from the base of the formation. The exact local subdivision is retained at this fossil-bearing horizon rather than importing numbered Sharpi Beds from Old Lodge.
Upper wall and lateral variation
In 1973 the Blisworth Limestone formed a steep upper wall that thickened to 17 ft, or more than 5 m, at the north-east end. This is a dated observation of one part of the park face, not a uniform cap thickness. The BGS district account also records several metres of the formation’s lower beds at the top of the Country Park face. It does not establish an exposed Blisworth Clay cap here.
Thickness and exposure limits
Historical descriptions used different measures of the face and worked material. Sutherland describes about 20 m of Middle Jurassic strata; the 2018 excursion account describes ironstone around 3 m thick in its machinery account, a worked seam of 3–5 m elsewhere in the same account, and removal of up to 10 m of Rutland and Blisworth overburden. These are not interchangeable measurements of a single complete section. The quarry’s scientific value rests on the preserved contacts and changing environments, not on forcing those figures into one total.
Scree, vegetation and displaced material
The 1973 observations show the Rutland clay slope and limestone rib clearly at the west end, but scree already obscured the lower sandy beds and exposed ironstone was sparse. Vegetation later concealed much of the face, prompting the conservation work and viewing structures. Fallen rock and quarry spoil therefore cannot always be assigned to their original bed from where they now lie.
References
Sutherland, D. (2017). Irchester Country Park – a new Ironstone Heritage Trail. Charnia, September 2017, pp. 3–6. Exact Country Park account, including historical photographs and interpretation of the lower Rutland beds.
British Geological Survey (2006). Wellingborough district: a brief explanation of the geological map, sheet 186. Middle Jurassic framework and the specific Country Park exposure; other quarries are identified separately.
Cox, B. M. and Sumbler, M. G. (2002). British Middle Jurassic Stratigraphy. Geological Conservation Review Series 26, Irchester Old Lodge Pit account, pp. 255–258. Regional and comparison evidence; its numbered measured section is not a Country Park log.
Colman, T. (2018). Irchester and Twywell, excursion of 20 May 2018. Mercian Geologist, 19(3), p. 181. The two localities are discussed separately.
BGS Lexicon: Northampton Sand Formation; Rutland Formation; Stamford Member; Wellingborough Limestone Member; Blisworth Limestone Formation.
British Geological Survey (2011). A stratigraphical framework for the Middle Jurassic strata of Great Britain and the adjoining continental shelf, section 5.2.17. Blisworth Limestone member framework; compare current Lexicon entries for Irchester, Roade and Ardley.
SAFETY
The quarry faces are high and unstable, with loose limestone above softer clay slopes. Stay away from the foot and edge of the face and do not climb the scree to reach a fossiliferous layer. A hard hat does not make entry beneath an unstable face safe. Keep children on managed paths and viewpoints with close supervision.
Clay, leaf litter and uneven rock can be slippery, particularly after rain, and low ground may be wet or flooded. Wear boots with good grip and turn back rather than crossing soft or flooded ground. Carry an offline map and tell someone your plans; do not rely on mobile reception inside the quarry.
EQUIPMENT
For a geology walk, take walking boots, a hand lens, a camera, a notebook and a small photographic scale. Binoculars help with beds high in the face. Leave hammers and chisels at home unless the country parks team has explicitly approved a particular activity; tools do not solve the access or rockfall risks.
CLEANING AND TREATING
For previously or expressly lawfully collected material, begin with a soft dry brush and work under magnification. Shells can be much weaker than their limestone matrix, while clay-rich pieces and carbonaceous plant material may crumble when wetted. Try any cleaning method on a small, unimportant area first and allow damp specimens to dry slowly at room temperature.
Avoid household acids, bleach, prolonged soaking and routine varnishing. Do not force hard limestone away from a shell that is breaking with the matrix; fine mechanical preparation may require specialist help. Keep labels and a little matrix with authorised specimens. Leave possible footprints, unusual vertebrate material and significant plant-bearing surfaces unprepared for specialist assessment.
IDENTIFY YOUR FINDS
Need help identifying a fossil? Share clear photos, where you found it and its size with the community.
FURTHER READING
Diana Sutherland: Irchester Country Park and the Ironstone Heritage Trail (pages 3–6)
Earth Heritage: conserving and interpreting Irchester’s Jurassic quarry (pages 39–41)
BGS: geology of the Wellingborough district
Northampton Museums: the Irchester brachiopod Kallirhynchia sharpi
Northampton Museums: the Irchester dinosaur footprint cast
North Northamptonshire Council: Irchester Country Park and current visitor information
ACCESS RIGHTS
Irchester Country Park is managed by North Northamptonshire Council and the quarry is recognised as a locally important geological site. The council provides public park trails and quarry interpretation, but public entry does not by itself authorise fossil removal, hammering or access below unstable faces. Ask the country parks team what collecting, if any, is currently allowed before taking material.
Keep to the managed paths and viewpoints, obey closures and leave barriers intact. Permission for an organised scientific visit or an earlier collecting event does not apply automatically to another visitor. Any approved work must stay within the manager’s stated areas, methods and limits; unusual or scientifically important finds should be reported before they are disturbed.
It is important to follow our ‘Code of Conduct’ when collecting fossils or visiting any site. Please also read our ‘Terms and Conditions‘
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