The former Houghton Regis chalk quarry reveals a fossil-rich Cretaceous seabed, including the distinctive Totternhoe Stone and its reworked shells. The quarry is now an important wildlife site where fossils are for observation and photography: collecting and hammering are not permitted.
FIND FREQUENCY: ♦♦♦♦ – A rich recorded chalk fauna, but fossils must be left in place. This is an observation and photography site.
CHILDREN: ♦♦ – High quarry faces, steep slopes and water require close supervision; stay on the paths.
ACCESS: ♦♦♦♦ – Established approaches use the Icknield Way and paths from Houghton Road; allow for slopes, steps and muddy ground.
TYPE: – Disused chalk quarry and wildlife reserve. Collecting and hammering are not permitted.
DIRECTIONS
♦ For the western approach, use the White Lion on Chalk Hill, LU6 1RS, as the landmark on Watling Street (A505, formerly A5). Ask the pub before leaving a vehicle in its private car park and follow current parking signs. Cross the main road only where safe and follow the signposted Icknield Way down towards the track beside the cottages.
♦ From the track, turn left and follow the Icknield Way right through the alley between two properties. Continue to the field, follow its lower edge and take the path on the right uphill towards the gap in the hedge and the quarry. The approach from the main road is approximately 300 m, mainly uphill.
♦ An alternative approach starts in Millers Way. Use legal parking without obstructing residents, then return to Houghton Road and follow the footpath through the houses towards the gates and kissing-gate entrance. The route into the quarry is approximately 1 km and more level than the western approach.
♦ Inside the reserve, follow the established paths and current signs. Observe the chalk from a safe distance rather than heading to the foot of a face; do not enter fenced areas or the lake margins.
♦ Ref: 51.90126°N, 0.53519°W
FOSSIL HUNTING
The chalk faces and loose fragments at Houghton preserve evidence of a marine community dominated by bivalves and brachiopods. Fossil collecting and hammering are not permitted here. Study and photograph fossils from authorised paths without disturbing the rock or habitats; do not enter the lakes or climb the quarry faces to reach a fossil bed.
In fallen material visible beside the paths, distinguish soft, fine chalk from the slightly gritty, harder Totternhoe Stone. Its grittiness comes mainly from broken fossil material rather than ordinary quartz sand. The basal part is especially fossiliferous, with brown phosphatic pebbles and mineralised internal moulds of shells. These are casts of the inside of a shell, so a specimen may retain its overall shape while lacking the original shell surface.
Thin scallop-like valves of Entolium, the small attached bivalve Plicatula inflata and rounded terebratulid brachiopods are characteristic of the recorded Totternhoe Stone fauna. The ribbed brachiopod Orbirhynchia mantelliana is also common in this bed. Many shells were washed out of older sediment and redeposited here, even when their preservation looks fresh. A rich mixed assemblage therefore does not mean that every animal lived at the same moment on the seabed represented by its enclosing rock.
Other documented fossils include the belemnite Actinocamax primus and ammonite moulds identified as Acanthoceras rhotomagense, Cunningtoniceras, Turrilites costatus and common straight-shelled Sciponoceras baculoides. These records demonstrate reworking from several earlier Cenomanian horizons. They are a scientific record of the quarry, not a promise of readily available finds on a present-day walk. Keep a suspected unusual ammonite or other significant fossil in place for photography and seek specialist advice before any further investigation.
The chalk below the Totternhoe Stone contains a different association. Inoceramus of the virgatus group is abundant low in the measured section, with Plicatula inflata and some shells recorded as Inoceramus crippsi. Brachiopods change upwards from Monticlarella? rectifrons to Grasirhynchia grasiana. Higher in the quarry, oyster-rich horizons with Pycnodonte and then Amphidonte help distinguish different levels. Recording the precise position and matrix is consequently more useful than labelling everything simply ‘Houghton chalk’.
Trace fossils are worth noticing too. Branching Thalassinoides burrows descend from the Totternhoe Stone into the chalk beneath, carrying gritty sediment into the older bed. The detailed log also records Teichichnus above the stone and a higher horizon rich in Chondrites. These structures preserve animal activity rather than shells and can explain bedding relationships that are difficult to recognise from an isolated fossil.
Significant discoveries, geological research and conservation milestones at Houghton Regis Quarry.
Early 20th century – A substantial Totternhoe Stone collection
Amateur geologist E. A. Martin assembled an extensive fossil collection from the Totternhoe Stone at Houghton Regis. Preserved in the national geological collection, it records the rich mixed fauna of the bed and provides material for later interpretation of fossil reworking.
1970s – Cement production ends
Blue Circle cement production at Houghton Regis ceased during the 1970s. The abandoned chalk workings subsequently developed into a varied landscape of exposed rock, grassland and marl lakes, giving the former industrial quarry both geological and wildlife significance.
1988 – Marl lakes receive national protection
The marl lakes formed in the disused quarry were notified as a Site of Special Scientific Interest. Their unusual chalk-water habitats and associated wetlands became a defining conservation interest of the former industrial site.
1990 – The wider quarry is recognised for wildlife
A survey of the wider reserve led to its recognition as a County Wildlife Site, extending the conservation story beyond the separately protected marl lakes. This change helps explain the emphasis on careful observation and habitat protection during visits.
1994 – Detailed quarry succession published
The Geological Survey’s Leighton Buzzard memoir published a composite log and detailed fossil account for Houghton Regis. It documented the eroded Totternhoe Stone contact, reworked Cenomanian fauna, higher oyster horizons and the local reversal of regional dip, establishing the quarry’s modern geological framework.
2022 – Drone mapping records the changing quarry habitat
A high-resolution drone survey recorded the former quarry’s landform and habitats. Hundreds of overlapping photographs were used to produce an aerial mosaic, elevation model and three-dimensional record, supporting conservation work across the large excavated site.
GEOLOGY
Houghton Regis Quarry cuts through a substantial part of the Cenomanian Chalk and reaches the basal Melbourn Rock. The 1994 Geological Survey description records about 30 m of exposed succession, from roughly 5 m below the Totternhoe Stone to a small high-level Melbourn Rock cap. Those figures describe the recorded quarry exposure, not the thickness of every formation or the amount accessible today. The local beds dip about 2° north-west, reversing the usual regional dip direction.
The lower part belongs to the West Melbury Marly Chalk Formation. It alternates clay-rich chalk with more calcareous, slightly gritty layers formed partly from redistributed sediment. Erosion then cut into this seabed before the Totternhoe Stone accumulated. The stone forms the base of the Zig Zag Chalk Formation here: a harder, fossil-fragment-rich layer with phosphatic clasts and a conspicuously mixed fossil assemblage. It is a good example of why the age of a fossil and the age of the sediment enclosing it can differ.
The prominent ledge is more complicated than a single uniform ‘stone band’. A second, finer-grained detrital chalk lies above the Totternhoe Stone, separated in places by a thin marl. Scouring removed that marl locally, and later burrowing blurred the boundary. Farther up, the succession becomes more uniform grey chalk but retains oyster-rich markers. These local changes make the quarry valuable for studying erosion, sediment transport and changing marine communities within the Chalk sea.
At the top of the recorded section, the yellowish-green Plenus Marls and nodular Melbourn Rock mark the base of the Holywell Nodular Chalk Formation within the White Chalk Subgroup. Older accounts include much of the succession under ‘Lower Chalk’, but modern lithostratigraphy places the Plenus Marls with the overlying formation. The highest beds were already difficult to reach when the Survey described them; their position is best understood from the quarry profile rather than by approaching an unsafe face.
Explore the recorded chalk succession, erosion surfaces and fossil horizons at Houghton Regis Quarry.
Scope of the measured sections
The Geological Survey’s Houghton Regis sections at TL 005236 and its detailed composite at TL 004236 document about 30 m of quarry exposure. The base is about 5 m below the Totternhoe Stone; the highest small cap reaches basal Melbourn Rock. The description below follows those historical observations. Vegetation, talus and flooding affect what is visible now, and the composite is not a single continuously accessible face.
CHALK GROUP
GREY CHALK SUBGROUP
West Melbury Marly Chalk Formation
Basal exposed calcisiltitic chalk
The bottom of the detailed composite is a slightly gritty, detrital chalk. Shells of the Inoceramus virgatus group are abundant towards the top of this lowest exposed bed. Its base is the limit of the quarry log, not the base of the formation.
Lower marly chalk
A more clay-rich chalk interval overlies the basal gritty bed. The plotted fossil horizons include abundant Inoceramus of the virgatus group, Plicatula inflata, subordinate shells recorded as Inoceramus crippsi and locally Pycnodonte; the symbols do not show every species throughout the whole bed. Partly oxidised pyrite nodules are also recorded. This low assemblage is Lower Cenomanian and no earlier than the dixoni Zone.
Lower micritic and calcisiltitic alternations
The succeeding chalk alternations include locally cemented patches, pale phosphatised and unphosphatised chalk intraclasts and partly oxidised pyrite nodules. Monticlarella? rectifrons occurs low in this interval. The gritty, more calcareous beds show considerable redeposition of sediment, distinguishing Houghton from the nearby Barton and Sundon sections.
Sponge-bearing interval
The detailed composite records a meandriform sponge and a spongiferous limestone among these lower alternations, alongside Inoceramus of the virgatus group and Plicatula. Rare plant debris is also documented in the chalk below the Totternhoe Stone. These are observations from the Houghton section, not fauna borrowed from a neighbouring quarry.
Higher pre-Totternhoe calcisiltite
In the highest gritty chalk, Grasirhynchia grasiana replaces the lower Monticlarella? assemblage. Intraclasts and pyrite occur in the figured harder layer. The Inoceramus virgatus group becomes less frequent upwards and was traced to about 1.5 m below the Totternhoe Stone.
Chalk immediately beneath the Totternhoe Stone
The chalk overlying the highest calcisiltite also contains Grasirhynchia grasiana. Its upper surface was eroded and burrowed before the stone accumulated; locally the bed is reduced to only 15 cm. This is a preserved thickness, not a measurement of how much sediment was removed. No further thicknesses have been inferred from the diagram for these unnumbered lower beds.
Age and correlation immediately below the erosion surface
Neither a definite Dixoni Limestone nor the overlying chalk with abundant Orbirhynchia mantelliana was recognised here. This could reflect local expansion, erosion or a limestone equivalent that remained uncemented or lies below the exposure. The bed immediately beneath the Totternhoe Stone yielded benthic foraminifera of Zone 11(i), suggesting earliest Middle Cenomanian sediment, but younger microfossils introduced through burrowing remain a possible explanation. The boundary should therefore not be reconstructed as a complete standard southern-English sequence.
Zig Zag Chalk Formation
Totternhoe Stone Member
Eroded base and sediment-filled burrows
The Totternhoe Stone rests on a pronounced scour. At some points the erosion surface approaches the base of the underlying marly bed, while branching Thalassinoides burrows carry calcarenitic sediment down into the older chalk. The erosional and burrowed contact is evidence of interrupted deposition and reworking, rather than a simple gradual change from one uniform chalk to another.
Totternhoe Stone, up to 0.9 m
The member forms a hard, massive, fossil-fragment-rich bed. Brown phosphatic intraclasts are concentrated in its lowest 0.4 m but occur as high as 0.7 m above the base. Abundant Orbirhynchia mantelliana, thin-shelled Entolium, Plicatula inflata and terebratulid brachiopods occur with phosphatised internal moulds of originally aragonite-shelled gastropods and ammonites. The stone passes upwards into more fissile marly chalk. The whole prominent ledge containing this and the succeeding beds is about 4.5 m thick; that figure is not the thickness of the Totternhoe Stone itself.
Reworked fossil assemblage
The recorded Actinocamax primus, Acanthoceras rhotomagense, Cunningtoniceras, Turrilites costatus, common Sciponoceras baculoides and Inoceramus tenuis demonstrate derivation from older Cenomanian horizons. Even brachiopods and bivalves that appear little worn may have been redeposited. Actinocamax primus points to the equivalent of the Folkestone Cast Bed, whereas Inoceramus tenuis shows that reworking reached at least as far down as the underlying limestone in the costatus Subzone. Much of the Orbirhynchia mantelliana was interpreted as derived from the highest regional band of that species, with a possible contribution from the second band. These are correlations of the source material, not additional exposed Houghton beds. The enclosing stone probably postdates the mid-Cenomanian break above the highest Orbirhynchia mantelliana band.
Marl immediately above the Totternhoe Stone
The stone passes rapidly upwards into a more fissile, marly chalk. This separating layer is locally absent because the next harder bed rests on a scoured surface. It is therefore not a continuous marker of uniform thickness across the quarry.
Younger calcisiltitic chalk
Above the separating marl is a finer-grained detrital chalk containing fewer phosphatic pebbles than the Totternhoe Stone. Scouring and later burrowing can make the two harder beds appear to merge where the marl is absent. The higher calcisiltite lacks abundant Orbirhynchia mantelliana, apart from rare broken shells, and its log includes Teichichnus. This is a younger lookalike bed rather than simply a second Totternhoe Stone layer.
Upper marly transition
The younger calcisiltite passes rapidly upwards into marly chalk. The composite shows a burrowed surface within the upper part of this lower bed group, recording further animal mixing of the seabed.
Micritic chalk with Concinnithyris
Above the more rhythmic lower succession, the rock becomes more uniform pale-grey chalk containing Concinnithyris subundata. This change distinguishes the softer, less obviously bedded higher chalk from the prominent harder ledge below.
Higher micritic chalk and sparse mineralised material
The figure records isolated phosphatic material and a partly oxidised pyrite nodule in the higher micritic chalk. These symbols are individual observations; they do not establish additional named or separately measured beds.
Unexposed interval
An explicit unexposed gap separates this lower detailed section from the next marly, oyster-bearing interval. No thickness or invented bed succession is supplied for the gap. The general quarry section and the detailed composite must be read together rather than joined into a falsely continuous face.
Pycnodonte–Chondrites horizon, about 7.5 m above the stone’s base
An oyster-rich horizon with Pycnodonte and abundant Chondrites occurs about 7.5 m above the base of the Totternhoe Stone. The detailed figure also marks Inoceramus pictus at its marly interval. A possible correlation with the highest Middle Cenomanian jukesbrownei Zone was proposed by comparison with Totternhoe, but Houghton lacks the recorded Inoceramus atlanticus shell beds and mineralised hardground of those neighbouring sections.
Amphidonte horizon, about 6 m higher
A second oyster concentration lies roughly 6 m above the Pycnodonte marker. Its relatively coarse-grained chalk contains Amphidonte and was interpreted as almost certainly belonging to the basal Upper Cenomanian guerangeri Zone. The overlying chalk was inaccessible in the Survey account, so the two measured marker offsets should not be treated as a fully logged continuous upper succession.
WHITE CHALK SUBGROUP
Holywell Nodular Chalk Formation
Plenus Marls Member
High-level coloured marls
The general section marks roughly 10 m of inaccessible upper chalk, with yellowish-green Plenus Marls visible near its top. In current terminology these marls form the base of the Holywell Nodular Chalk Formation, above the Zig Zag Chalk Formation, and belong to the Upper Cenomanian. No exact Houghton member thickness or individual numbered marl-bed log is supplied by the quarry account; regional values are therefore not substituted here.
Melbourn Rock Member
Small basal cap
The nodular base of the Melbourn Rock caps a small high point near TL 00512344. Only its basal part is documented in the approximately 30 m quarry succession. The wider member spans the Cenomanian–Turonian transition, but the Houghton description does not establish a complete local member or a precisely located stage boundary.
Structure and exposure limits
The quarry account gives a dip of about 2° north-west, while the memoir’s wider structural discussion records 2–3° north-west. Houghton lies on a north-east–south-west anticlinal roll between Sundon and Houghton Regis, reversing the normal regional dip direction. An associated gravity anomaly led to a suspected link with a deeper basement structure, but that link was not established directly. Talus, lakes and inaccessible upper faces separate the logged exposures, and neighbouring quarry successions cannot replace the actual Houghton record.
References
Shephard-Thorn, E. R., Moorlock, B. S. P., Cox, B. M., Allsop, J. M. and Wood, C. J. (1994). Geology of the country around Leighton Buzzard. British Geological Survey memoir, sheet 220. Houghton Regis Quarry section, Figure 24, Structure chapter and Lime and cement account.
Hopson, P. M. (2005). A stratigraphical framework for the Upper Cretaceous Chalk of England and Scotland. British Geological Survey Research Report RR/05/01.
BGS Lexicon: West Melbury Marly Chalk Formation; Zig Zag Chalk Formation; Totternhoe Stone Member; Holywell Nodular Chalk Formation; Plenus Marls Member; Melbourn Rock Member.
SAFETY
Keep to established paths, away from the tops and bases of high chalk faces. Loose chalk, steep slopes and talus can be unstable, and a prominent fossil layer is not a safe route across a face. Use binoculars to study the upper beds.
The quarry contains steep-sided water, wet ground and sensitive lake-edge habitats. Do not swim, wade or venture onto soft margins; keep children closely supervised. Chalk paths can become slippery when wet, and vegetation may conceal holes and abrupt changes of level.
EQUIPMENT
Take walking boots with good grip, a hand lens, binoculars and a camera. A small scale and notebook are useful for recording fossils in place without disturbing them. Do not bring hammers or chisels for collecting: this is an observation and photography visit.
CLEANING AND TREATING
No specimens should be taken from this visit. For previously and lawfully acquired Houghton material, begin with a soft dry brush and retain a little of the matrix that records the fossil’s horizon. Chalk shells and thin brachiopod or bivalve valves can be much more fragile than a phosphatic internal mould. Test stability before using any water, avoid prolonged soaking of marly pieces, and let damp specimens dry slowly at room temperature.
Do not use household acids, bleach or routine varnish: these can damage calcitic shells and destroy useful surfaces. Hard matrix is best reduced cautiously under magnification. Leave unusual ammonites, trace-fossil relationships and potentially important assemblages unprepared until a specialist has assessed them.
IDENTIFY YOUR FINDS
Need help identifying a fossil? Share clear photos, where you found it and its size with the community.
FURTHER READING
BGS: geology of the Leighton Buzzard district, including Houghton Regis Quarry
BGS: modern stratigraphic framework for the Chalk
Wildlife Trust: drone mapping at Houghton Regis Chalk Pit
Natural England: Houghton Regis Marl Lakes SSSI citation
Houghton Regis neighbourhood plan: Chalk Pit Nature Reserve
ACCESS RIGHTS
Houghton Regis Chalk Pit contains the Houghton Regis Marl Lakes SSSI and the wider County Wildlife Site. Fossil collecting and hammering are not permitted. The neighbourhood plan describes access via existing footpaths as being for general walking and enjoyment of nature only. Stay on the paths and follow current signs.
The Wildlife Trust previously managed the reserve but states that this ended around 2015–2016, so an old Trust contact should not be assumed to represent the current landowner or manager. Organised scientific study needs specific agreement with the present manager. The Marl Lakes SSSI is protected for its lake and wetland habitats; its consent paperwork includes specimen removal, chalk extraction and rock-face alteration and does not create a visitor collecting permit.
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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