Clevedon Beach, beside its famous Victorian pier, exposes a remarkable sequence of rocks from the late Devonian to the Triassic. The main fossil-bearing strata are the Early Carboniferous limestones and shales south of the Pier, where collectors can see crinoid stems and ossicles, brachiopods, corals, trace fossils, fish remains and occasional straight-shelled cephalopods. One important local fossil is the coral Vaughania vetus, recorded from the Avon Group on the Clevedon foreshore.
FIND FREQUENCY: ♦♦♦ – Fossils are common in the right Early Carboniferous beds south of Clevedon Pier, particularly crinoid debris, brachiopods and shell-rich limestone, although much of the fossil material is in solid rock and collecting must respect the SSSI and local restrictions. Loose specimens are most likely after storms and periods of beach scour.
CHILDREN: ♦♦♦ – The seafront is easy to reach and has nearby facilities, but the foreshore contains steeply tilted, slippery rock surfaces and extensive soft mud. Children need close supervision and should not venture onto the outer mudflats.
ACCESS: ♦♦♦♦ – Access is straightforward from Clevedon seafront and the Pier, with parking nearby. The fossil-bearing Carboniferous rocks lie south of the Pier towards and beyond the old landing stage / jetty.
TYPE: Clevedon is a foreshore and rock-platform locality. Fossils occur mainly in Early Carboniferous limestone, shale and associated beds south of the Pier, while Devonian and Triassic rocks and the protected mineralised fault occur around the Toll House and northern part of the beach.
DIRECTIONS
♦ Leave the M5 at Junction 20 and follow signs through Clevedon to the seafront and Clevedon Pier.
♦ The easiest reference point is Clevedon Pier, The Beach, Clevedon, North Somerset. From the Pier, walk south along the foreshore towards the old landing stage / jetty. The principal fossil-bearing Early Carboniferous rocks occur south of the Pier and become more fossiliferous around and beyond the jetty.
♦ Limited free parking is available on The Beach and Elton Road. Paid parking is also available at Salthouse Fields, Old Church Road, Clevedon, BS21 7TU.
♦ Postcode for Clevedon Pier: BS21 7QU; Google Maps
♦ Alternative parking at Salthouse Fields, BS21 7TU: Google Maps
♦ What3Words: ///latter.ladder.called
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FOSSIL HUNTING
For fossil hunting, concentrate on the Early Carboniferous rocks to the south of Clevedon Pier rather than the mineralised cliff beneath the Toll House. Between the Pier and the old landing stage the rocks include thin beds of sandstone, siltstone and mudstone with ripple structures, and fossils are comparatively sparse. Around and just beyond the jetty the succession becomes more limestone-rich and much more fossiliferous. Search loose, naturally weathered material on the foreshore and freshly exposed surfaces after storms, but do not hammer or remove material from protected SSSI exposures.
Crinoids are among the most conspicuous fossils at Clevedon. Some beds are packed with circular crinoid ossicles, the individual plates that made up the stems of these sea-lily relatives, and short lengths of articulated stem can also occur. The red crinoidal limestone known historically as the Bryozoa Bed is an important local marker. British Geological Survey records place this bed at the former landing stage about 150 yards south of the Pier, where it is approximately 9 ft thick and dips steeply towards the south-south-east. Individual crinoid columnals are often abundant, although they usually cannot be identified reliably to species from isolated stem pieces alone.
Brachiopods are also common and can form dense shell-rich layers. The Clevedon Pier geology guide interprets some of these shell beds as storm concentrations, where shells were swept together on the sea floor. In equivalent Avon Group strata of the Bristol–Mendip district, characteristic brachiopods include Chonetes failandensis, Avonia bassa, Eumetria carbonaria and Unispirifer tornacensis. Identification of weathered Clevedon specimens to species should be made cautiously, as many loose shells are incomplete or preserved only as moulds and impressions.
Corals are less abundant than crinoids and brachiopods but can be important finds. Both solitary and colonial corals occur in the Lower Carboniferous succession. The British Geological Survey specifically records the small coral Vaughania vetus — historically called Cleistopora geometrica — from beds on the beach about 270 yards south-south-west of the Pier entrance. Higher and younger Carboniferous limestones in the wider Clevedon district also contain a richer coral fauna; the named species Sychnoelasma clevedonensis is part of the classic Early Carboniferous coral succession of the Bristol–Mendip region, although it should not be assumed that every Clevedon beach coral belongs to this species.
The site also yields vertebrate and cephalopod material. A conspicuous limestone bed close to the jetty contains dark plates and fragments of fish bone, while other beds show branching and anastomosing trace fossils made by soft-bodied sea-floor organisms. Occasional straight, conical cephalopod shells — orthocone nautiloids — occur with crinoid debris. These are much less common than crinoid ossicles or brachiopods, so complete examples are particularly interesting. Fish material should be collected and prepared carefully because thin phosphatic fragments can be brittle and scientifically useful.
Clevedon is especially rewarding because the fossils can be viewed in their geological context. The Carboniferous sequence records the change from river-influenced coastal sediment to a shallow tropical sea, and the abundance of crinoids, brachiopods, corals and other marine fossils increases as the succession becomes more limestone-rich. The best approach is therefore to examine loose blocks and naturally weathered bedding surfaces rather than breaking the bedrock. Remember that the area around the Pier includes the Clevedon Shore SSSI, designated for its nationally important mineralisation; protected exposures and the mineralised fault must be left undisturbed.
Some of the most important geological discoveries, fossil finds and scientific milestones from Clevedon include Arthur Vaughan’s pioneering Carboniferous fossil zonation, the discovery of the Walton Bone Cave, G. E. Bush’s detailed study of the Clevedon coast section, Geological Survey mapping and modern research into Clevedon’s unusual Triassic lake deposits.
1905 — Arthur Vaughan establishes a pioneering Carboniferous fossil zonation
In 1905 the geologist and palaeontologist Arthur Vaughan published his landmark study The Palaeontological Sequence in the Carboniferous Limestone of the Bristol Area. Vaughan used successive assemblages of corals and brachiopods to divide the Lower Carboniferous rocks of the Bristol region into fossil zones, creating one of the earliest detailed biostratigraphical schemes for the British Carboniferous. The lower part of the succession became associated with the name “Clevedonian”, after Clevedon, while Vaughan’s lowest major coral zone was characterised by the fossil then called Cleistopora geometrica. The coral is now known as Vaughania vetus and occurs in the Avon Group at Clevedon. Vaughan’s work made the Bristol–Clevedon district internationally important in the early development of Carboniferous biostratigraphy.
1905–1907 — discovery and excavation of the Walton Bone Cave
In 1905 quarrying at Holly Lane, Walton, on the eastern side of Clevedon exposed a small cave and a remarkable sequence of Pleistocene breccias, sands and silts. The cave and surrounding deposits contained more than 2,000 fossil bones. Sidney Hugh Reynolds investigated and excavated the site, while H. N. Davies studied the cave and surrounding sediments. Mammalian remains examined by Reynolds and Martin A. C. Hinton included horse, bear, wolf, fox, voles and possible Arctic fox and lemming. Hinton also recognised the Alpine vole Microtus nivalis, an important indication of cold Pleistocene conditions. Bird remains were also recovered and included species representing eagles, buzzards, herons, gulls and cormorants. The site became known as the Clevedon or Walton Bone Cave and remains one of the important Quaternary fossil localities of the Bristol region.
1922 — Edward Greenly recognises Clevedon’s wind-blown Ice Age deposits
Geologist Edward Greenly published An Aeolian Pleistocene Deposit at Clevedon in 1922 after studying the deposits exposed at Holly Lane. Greenly recognised that some of the sandy layers covering the fossil-bearing breccias were aeolian — sediments transported and deposited by wind. This was an important step in understanding the Ice Age history of Clevedon. The alternating breccias and wind-blown sediments showed that the landscape had experienced repeated phases of severe frost-shattering, slope movement and deposition during cold Pleistocene conditions. Greenly also reviewed the extraordinary fossil assemblage recovered from the cave and surrounding deposits.
1928 — G. E. Bush describes the Avonian succession along the Clevedon coast
G. E. Bush published The Avonian Succession at Clevedon — A Description of the Coast Section, one of the most important early detailed accounts of Clevedon’s Carboniferous geology. Bush described the sequence exposed along the coast and provided measurements of individual beds. His observations remain quoted in later British Geological Survey publications. In particular, the distinctive red crinoidal “Bryozoa Bed” near the old landing stage south of Clevedon Pier was recorded as being about 9 ft thick, with approximately 45 ft of crinoidal limestone above it. Bush’s work helped establish Clevedon as an important reference locality for the lower Carboniferous succession of the Bristol district.
1927–1929 — further investigation of the Walton fossil deposits
Lionel S. Palmer and palaeontologist Martin A. C. Hinton returned to the Walton deposits and carried out further investigation of the gravels and fossil-bearing sequence. Their work provided additional information on the stratigraphy and fossil content of the site and was subsequently published as Some Gravel Deposits at Walton near Clevedon. The combination of fossil mammals, birds and molluscs with the unusual breccias and wind-blown sediments made the site increasingly important for reconstructing the Pleistocene environments of North Somerset.
1939–1963 — Geological Survey mapping establishes the modern geological framework
A major Geological Survey resurvey of the Bristol district began in 1939 under G. A. Kellaway and F. B. A. Welch. Work was interrupted by the Second World War but continued through the 1940s and early 1950s, with G. W. Green later joining the survey. Their detailed field mapping established the modern structural and stratigraphical framework for Clevedon, including the Devonian Old Red Sandstone, lower Carboniferous rocks, major folds and faults and the younger Triassic deposits. The resulting Bristol District geological map was published at one-inch scale in the early 1960s and provided the basis for much subsequent geological work in the area.
1972–1973 — Lower Carboniferous rocks and trace fossils revisited
Clevedon formed part of an important Geologists’ Association field meeting examining the Lower Carboniferous successions of North Somerset. The work was directed by S. C. Matthews, M. Butler and P. M. Sadler and concentrated on the former Lower Limestone Shale succession at Clevedon and Portishead. Sedimentary structures and trace fossils were studied in detail, helping geologists interpret the change from river-influenced coastal environments into the shallow tropical Carboniferous sea represented by the overlying limestones.
1974 — D. D. Gilbertson and A. B. Hawkins reinterpret Clevedon’s Ice Age history
David D. Gilbertson and A. B. Hawkins carried out a major re-examination of the Pleistocene deposits at Holly Lane. They described a complex succession of breccias and sandy loams banked against an ancient cliff and interpreted the sequence as evidence of changing cold-climate conditions during the Devensian. They also recognised an older marine erosion surface and wave-cut notch beneath the deposits. Their work transformed Holly Lane from simply a “bone cave” locality into an important record of changing sea levels, periglacial activity and landscape evolution around Clevedon.
1993 — Kellaway and Welch consolidate the geology of Clevedon in the BGS Bristol memoir
G. A. Kellaway and F. B. A. Welch’s British Geological Survey memoir Geology of the Bristol District brought together decades of mapping and research across the area. The memoir provides detailed descriptions of the Clevedon coastal succession, including the red crinoidal Bryozoa Bed south of the Pier and the occurrence of the coral Vaughania vetus, formerly called Cleistopora geometrica, near the beach. It also records the complex folding and faulting affecting the Carboniferous rocks around Wain’s Hill, Dial Hill, Salthouse Bay and the wider Clevedon district.
2024 — Maurice E. Tucker and R. Stephen J. Sparks reveal new details of Clevedon’s Triassic lakes
University of Bristol geologists Maurice E. Tucker and R. Stephen J. Sparks published a detailed modern study of the Triassic rocks at Clevedon in Geological Magazine. Their research investigated the yellow dolomites, red silicified bands and nodules, conglomerates and marls exposed around Clevedon Pier and the nearby coast. They showed that the deposits formed around the margins of a large shallow saline and alkaline lake during the Triassic, with flash floods carrying sediment from the surrounding land into the lake. Their microscopic, mineralogical and geochemical work also demonstrated that the conspicuous red chert bands formed through early silicification associated with interactions between fresh floodwater and the saline lake environment. The study provides one of the most detailed modern interpretations of the unusual Triassic geology visible beside Clevedon Pier.
GEOLOGY
Clevedon Beach provides an unusually compact geological section in which rocks from the late Devonian, Early Carboniferous and Triassic can be examined within a short walk around the Pier, with the Permian represented by a major gap in the rock record. The exposed rocks span roughly 140 million years of Earth history, from about 360 to 220 million years ago. Devonian river sandstones, fossiliferous Carboniferous marine beds, Triassic breccias and lake deposits are juxtaposed by unconformities, folding and a major mineralised fault.
The oldest rocks visible beside the Pier are late Devonian Old Red Sandstone, traditionally described here as the Portishead Formation and placed within the Portishead Subgroup. They are exposed below and beside the Toll House and consist mainly of reddish cross-bedded sandstone deposited by large, fast-flowing river systems on a broad continental plain. Cross-bedding preserves the migration of ancient river dunes. These Devonian sandstones are largely unfossiliferous at Clevedon itself, although related Devonian rocks farther along the coast can contain plant and freshwater fish remains.
South of the Pier the succession passes into Early Carboniferous rocks of the Avon Group, the modern BGS name for strata historically called the Lower Limestone Shale. The earliest beds contain sandstone, siltstone and mudstone with ripple structures, recording a shoreline still influenced by rivers. Up-section, limestone becomes more abundant as a shallow tropical sea developed. Fossils include brachiopods, crinoid stems and ossicles, bryozoans, corals, fish remains, trace fossils and occasional orthocone nautiloids. The red crinoidal Bryozoa Bed near the old landing stage is a particularly distinctive unit.
No Permian sedimentary rocks are preserved on Clevedon Beach. Instead, the Permian is represented by a major interval of deformation, uplift and erosion associated with the Variscan mountain-building episode as the continents that formed Pangaea collided. The older Devonian and Carboniferous beds were tilted and locally folded, and erosion cut across them. This produced the pronounced unconformities now visible where much younger Triassic deposits rest against or upon the Palaeozoic rocks.
Triassic rocks around the Toll House belong to the marginal facies of the Mercia Mudstone Group. Angular breccias and conglomerates — historically called the Dolomitic Conglomerate — were deposited by scree, debris flows and flash floods around desert mountains, while pale cream-grey dolomitic, oolitic lake-margin sediments formed in a shallow saline lake. A major fault beneath the Toll House later acted as a pathway for mineral-rich fluids, producing baryte and metal sulphides together with a diverse secondary mineral assemblage. This mineralisation is the principal reason for the Clevedon Shore SSSI designation.
This is a detailed geological breakdown of Clevedon Beach around the Pier, where late Devonian river sandstones, Early Carboniferous Avon Group marine strata and Triassic Mercia Mudstone Group marginal deposits occur within a remarkably short distance. The section also records the missing Permian interval, Variscan folding and erosion, major unconformities, and the nationally important mineralised fault beneath the Toll House.
Section Architecture
Clevedon is not a single continuous vertical cliff section. Devonian sandstone is exposed beneath and beside the Toll House, Triassic breccia and pale lake-margin deposits occur around the same northern part of the beach, and the fossil-bearing Early Carboniferous rocks lie to the south of the Pier towards and beyond the old landing stage. Unconformities and a major fault place rocks of very different ages close together. Beach sand and Severn Estuary mud can cover substantial parts of the foreshore, so the amount of bedrock visible changes after storms and periods of scour.
Structural Note
The Palaeozoic rocks form part of the Clevedon–Portishead structural belt and have been tilted and folded by Variscan deformation. At the old landing stage the red crinoidal Bryozoa Bed dips about 30° towards the south-south-east, and visible folds occur in the Carboniferous rocks farther south. A major approximately east–west fault at the base of the Toll House cliff places Devonian and Triassic rocks against younger units and provided the fracture system through which mineralising fluids circulated. This structural complexity is central to both the geology and the SSSI interest of the beach.
OLD RED SANDSTONE
Portishead Subgroup / Portishead Formation (Late Devonian)
Fluvial sandstones beneath the Toll House
Devonian river-channel sandstones
The oldest rocks immediately around Clevedon Pier are reddish to brown sandstones of Old Red Sandstone facies, traditionally referred to locally as the Portishead Formation. They were deposited by large river systems draining a continental landscape near the end of the Devonian Period. Cross-bedding is conspicuous in places and records migrating dunes and bars on the floors of fast-flowing channels. The original beds were laid down approximately horizontally but now dip steeply because of later Variscan deformation. At Clevedon Beach these sandstones are largely unfossiliferous, reflecting the high-energy river environment in which they formed.
Devonian–Carboniferous transition
From continental rivers to a marine shoreline
Across the Bristol district the uppermost Old Red Sandstone passes upward into beds showing progressively stronger marine influence. This transition records subsidence and flooding at the beginning of Carboniferous time. The lowest Carboniferous rocks retain red and green mudstone, sandstone and siltstone alongside the first marine limestones, showing that river plains, lagoons and shallow coastal water existed side by side. At Clevedon, the contrast between the largely unfossiliferous Devonian sandstones and fossil-bearing strata south of the Pier is one of the clearest ways to recognise this major environmental change.
CARBONIFEROUS
Avon Group (Tournaisian; formerly Lower Limestone Shale)
Lower mixed sandstone, siltstone and mudstone beds south of the Pier
The first Carboniferous exposures south of the Triassic rocks consist of thinly bedded fine sandstone, siltstone and mudstone. Rippled and wavy bedding records waves and tidal currents in very shallow water, while the mixture of sand, silt and mud shows that rivers were still supplying sediment to the coast. Fossils occur but are less abundant than in the limestone-rich beds farther south. These strata represent the early stages of the Carboniferous marine transgression across the former Devonian river plain.
Shirehampton Formation and the Bryozoa Bed
A major local marker is the red crinoidal Bryozoa Bed at the old landing stage about 150 yards south of Clevedon Pier. The BGS records it as approximately 9 ft thick and dipping about 30° to the south-south-east. In modern lithostratigraphical terminology, the Bryozoa Bed characterises the upper Shirehampton Formation, the lower unit of the Avon Group in the Bristol district. It is a haematite-stained bioclastic limestone composed largely of broken crinoid and bryozoan skeletal material and records a much more strongly marine environment than the river-influenced beds below.
Crinoidal limestone above the Bryozoa Bed
Historical descriptions of Clevedon record roughly 45 ft of crinoidal limestone overlying the Bryozoa Bed in the beach succession. These rocks contain abundant disarticulated crinoid ossicles and, locally, lengths of articulated stem. The ossicles accumulated when crinoid skeletons broke apart after death and were concentrated on the shallow sea floor. Some beds can be made largely of skeletal debris, creating a coarse bioclastic limestone. The abundance of crinoid material is one of the most characteristic fossil features of the Clevedon Carboniferous rocks.
Brachiopod-rich shell beds
Shell-rich limestone beds contain numerous brachiopods, and the Clevedon Pier geology guide interprets some as storm deposits in which shells were ripped from living communities and concentrated together. Characteristic brachiopods in equivalent Avon Group strata of the Bristol–Mendip district include Chonetes failandensis, Avonia bassa, Eumetria carbonaria and Unispirifer tornacensis. Loose Clevedon specimens are often incomplete, so species-level identifications should be made only where diagnostic shell form and ornament are preserved.
Avon Group — Fossiliferous marine limestone interval
Fish-rich and trace-fossil horizons
Fish-bone horizon close to the jetty
Immediately beyond the old jetty a conspicuous limestone bed is reported to contain abundant dark plates and fragments of fish bone. The material probably includes dermal skeletal elements from heavily armoured Early Carboniferous fishes, although isolated fragments should not be assigned to a species without specialist study. The concentration demonstrates that vertebrate remains formed part of the shallow-marine ecosystem alongside the much more abundant invertebrates. Small fragments may be easy to overlook because they can resemble dark pebbles against the grey limestone.
Trace fossils in muddy limestone
Several bedding surfaces preserve branching, winding or anastomosing structures produced by soft-bodied animals moving through or across wet sediment. These are trace fossils rather than body fossils and record behaviour such as feeding or burrowing. The Clevedon Pier guide attributes them broadly to worm-like marine organisms but does not assign a formal ichnological species. They are best appreciated on natural bedding surfaces and should be photographed in place rather than removed from protected or scientifically important exposures.
Crinoid-dominated beds
Farther through the fossiliferous Carboniferous sequence are beds in which crinoid debris becomes overwhelmingly abundant. Circular ossicles may cover bedding surfaces or make up a large proportion of the limestone, and short articulated stems can occur among them. Crinoids are echinoderms related to modern sea lilies and feather stars. Their skeletal plates were held together by soft tissue during life but separated rapidly after death, explaining why isolated columnals are far more common than complete crowns.
Corals and orthocone cephalopods
Occasional solitary and colonial corals occur in the fossiliferous limestones, together with straight, conical shells of nautiloid cephalopods commonly described as orthocones. The BGS specifically records the coral Vaughania vetus from the beach south-south-west of the Pier. These less common fossils add considerable diversity to an assemblage otherwise dominated by crinoids and brachiopods, and they reinforce the interpretation of a warm, shallow marine setting during the Early Carboniferous.
Upper Avon Group and nearby Black Rock Limestone
Vaughania vetus coral horizon
Vaughania vetus, historically recorded as Cleistopora geometrica, is an important lower Tournaisian coral in the classic Bristol succession. At Clevedon the BGS records it near a tank on the beach at approximately ST 4018 7162, around 270 yards south-south-west of the Pier entrance. It occurs within the upper part of the old Lower Limestone Shale succession, now assigned to the Avon Group. Because the coral can be uncommon, well-preserved examples have greater scientific interest than the abundant crinoid fragments.
Wider Clevedon Carboniferous succession
The Carboniferous geology continues beyond the immediate Pier beach into Wain’s Hill, Littleharp Bay, Salthouse Bay and the wider Clevedon district, where higher and younger limestones of the Black Rock Limestone and related units are exposed. These strata contain richer coral and brachiopod assemblages than the lowest Avon Group. The Early Carboniferous coral Sychnoelasma clevedonensis is recognised in the Bristol–Mendip regional succession and takes its species name from Clevedon, but it should not be used as a default identification for solitary corals found on the Pier beach without diagnostic comparison.
PERMIAN HIATUS AND TRIASSIC
Variscan deformation and the Permian unconformity
Missing Permian sedimentary record
The Permian Period is not represented by preserved sedimentary rocks on Clevedon Beach. Instead, this interval is recorded by deformation, uplift and erosion related to the Variscan mountain-building episode and the assembly of Pangaea. Rocks that had accumulated during Devonian and Carboniferous time were compressed, tilted and locally folded, then exposed to erosion. By the time Triassic sedimentation began, a rugged landscape of older rocks had been created and large parts of the earlier sequence had been removed.
Tilting and folding of the Palaeozoic beds
The Devonian and Carboniferous strata were originally deposited approximately horizontally but now dip markedly across the foreshore. The Bryozoa Bed near the landing stage, for example, dips about 30° to the south-south-east. Between the more fossiliferous Carboniferous exposures, folds can also be observed where formerly flat beds were compressed into curved structures. These features provide direct evidence of the enormous tectonic forces associated with continental collision during late Palaeozoic time.
Angular unconformities and ancient erosion surfaces
The contact between the older Palaeozoic rocks and the Triassic succession is an unconformity: a surface representing a long interval of deformation and erosion rather than continuous deposition. Around the Toll House, Triassic breccia rests against or above tilted Devonian sandstone, while elsewhere Triassic sediments lie adjacent to Carboniferous rocks. The contrasting orientation and character of the beds make the unconformity one of the most visually striking geological features of Clevedon Beach.
Mercia Mudstone Group Marginal Facies
The coarse Triassic rocks around Clevedon are now assigned by the BGS to the Mercia Mudstone Group Marginal Facies. Older field guides commonly call them the Dolomitic Conglomerate, a useful historical name still encountered in local literature. The unit consists of breccia, conglomerate and coarse sandstone derived largely from nearby older rocks. Around the margins of the Bristol Channel Basin these deposits accumulated close to steep relief under an arid to semi-arid climate, where sediment was moved by rockfall, debris flows and short-lived flood events.
Triassic breccia beneath and around the Toll House
The angular breccia exposed in the low cliff around the Toll House contains poorly sorted fragments of older rock in a carbonate-rich matrix. Its angular clasts indicate very short transport from nearby slopes rather than prolonged movement by a river. The deposit is interpreted as scree and debris-flow material shed from the eroding Pangaean mountains during intense storms. Large fallen blocks of the same breccia can occur on the beach, but because this area overlaps the mineralogical SSSI they should be left in place.
Triassic conglomerates and coarse sandstones north of the Pier
North of the Pier, bedded conglomerates and coarse sandstones record episodic streams and flash floods entering the basin margin. These beds represent the more fluvial part of the Triassic marginal system and demonstrate how rapidly depositional environments changed over short distances, from rocky mountain-front debris to stream channels and shallow lakes. Their coarse grain size and irregular bedding contrast strongly with the pale, fine-grained lake deposits on the main foreshore.
Triassic lake-margin pavement
The pale cream to grey pavement on the beach is part of a distinctive Triassic lake-margin succession. Recent research interprets these rocks as micritic and oolitic dolomites with associated sandstone and siltstone deposited along the shore of a large shallow saline–alkaline lake within the Bristol Channel Basin. Small carbonate ooids formed in the lake water, while fine sediment accumulated during quieter phases. The low-relief pavement is one of the easiest Triassic units to recognise around the Pier.
Ooids, early dolomitisation and silicification
Petrographic work on the Clevedon Triassic shows that many ooids were originally aragonitic and that the carbonate sediment was dolomitised very early, on or just below the lake floor. Silica introduced by fresh water during storms and floods later produced conspicuous silicified bands and nodules, including red chert coloured by finely dispersed haematite. These processes explain why the apparently simple pale pavement contains a complex mixture of dolomite, silicified material and reworked sediment.
Soft-sediment deformation and the possible footprint-like surface
A red muddy layer within the Triassic lake deposits shows unusual hollows and branching shapes. One surface has been compared with a three-toed dinosaur footprint, and dinosaur tracks are known from Triassic rocks elsewhere around the Bristol Channel. However, the Clevedon feature is not proven to be a footprint. An alternative interpretation is deformation of soft, water-rich sediment, possibly related to rapid deposition, dewatering, silica-gel formation or seismic shaking near the basin-margin fault. It should therefore be described as a possible footprint-like feature rather than a confirmed dinosaur track.
Major fault beneath the Toll House
A major fault crosses the beach at the base of the small cliff beneath the Toll House. It separates the Devonian sandstone and Triassic breccia on one side from the pale Triassic lake deposits and Carboniferous rocks on the other. Movement fractured the rocks and created pathways and open spaces through which hot mineral-bearing fluids could circulate. The fault is therefore both a structural boundary and the focus of the mineralisation for which Clevedon is nationally important.
Fault-hosted mineralisation
More than thirty mineral species have been identified around the Clevedon fault. Important primary minerals include baryte, galena, sphalerite, chalcopyrite and tennantite, with colourful secondary products such as malachite and azurite formed by later weathering. The assemblage is comparable with mineralisation elsewhere around the Mendips and Bristol district. Its scientific importance is the reason the immediate area is protected as the Clevedon Shore SSSI, so mineralised rock must not be collected without the appropriate permissions.
CLEVEDON SHORE SSSI AND STRUCTURAL GEOLOGY
Fault-hosted mineralisation and protected exposures
Clevedon–Portishead structural setting
Clevedon lies on the southern side of the Clevedon–Portishead structural high, where Devonian and Carboniferous rocks have been folded and faulted and later Triassic sediments were deposited against an irregular eroded landscape. The steep dips visible on the foreshore, small folds in the Carboniferous beds and the major Toll House fault are therefore parts of the same long tectonic history. These structures also explain why rocks separated by tens of millions of years can be examined within such a short distance around the Pier.
National geological importance and conservation
The Clevedon Shore SSSI is designated primarily for the unusual mineral assemblage associated with the fault and nearby shore exposures. Clevedon Pier’s official geological guidance states that rocks and minerals should not be collected within the SSSI without permission from Natural England and North Somerset Council. Fossil collecting should therefore be conservative: do not hammer, chip or prise material from protected exposures, and concentrate only on naturally loose Carboniferous material in areas where collecting is permitted. Important or unusual specimens are best photographed and recorded before any attempt at removal.
Depositional Environment
The Clevedon succession records an extraordinary sequence of environmental change. Late Devonian sandstones formed in large continental rivers. At the beginning of Carboniferous time the land subsided and was progressively flooded by a warm tropical sea, producing river-influenced muds and sands followed by crinoid-, brachiopod- and coral-bearing limestone. Variscan continental collision later folded and tilted these rocks and erosion removed the Permian record. During Triassic time Clevedon lay in the arid interior of Pangaea, where scree, debris flows and flash floods accumulated around mountain fronts while pale dolomitic sediments formed in shallow saline lakes. Later faulting and fluid flow introduced the metal-rich mineralisation that now gives the site much of its conservation importance.
Thickness and Exposure Note
The beach exposes only parts of a much thicker regional succession and should not be treated as one continuously measurable vertical section. The BGS gives the Shirehampton Formation a regional thickness of about 30–50 m in the Bristol area and the Avon Group as substantially thicker overall, but at Clevedon individual units are interrupted by beach cover, folding, faulting and younger Triassic deposits. Storms can temporarily strip away sand and mud and reveal excellent sections of the old Lower Limestone Shale / Avon Group, while at other times only the harder limestone ribs project through the beach.
References
Clevedon Pier & Heritage Trust. The Geology of Clevedon Pier & Beach and Minerals of Clevedon Pier.
Kellaway, G.A. & Welch, F.B.A. (1993). Geology of the Bristol District. British Geological Survey memoir for Special Sheet 264.
Waters, C.N., Waters, R.A., Barclay, W.J. & Davies, J.R. (2009). A lithostratigraphical framework for the Carboniferous successions of southern Great Britain (onshore). British Geological Survey Research Report RR/09/01.
British Geological Survey Lexicon of Named Rock Units: Avon Group and Shirehampton Formation; BGS regional accounts of the Portishead Formation / Subgroup and Mercia Mudstone Group Marginal Facies.
Tucker, M.E. & Sparks, R.S.J. (2024). Fluvial–lacustrine interactions in the Marginal Triassic, Clevedon, Bristol Channel Basin, UK: deposition, dolomitization and silicification. Geological Magazine, 161, e18.
Ashley, R.W., Wright, V.P. & Marriott, S.B. (2024). The Geology of the Clevedon Coast. In Lavis, S. (ed.), The Geology of the Bristol Region, Geologists’ Association Guide No. 78.
Geological Conservation Review account for Clevedon Shore mineralisation and Natural England Clevedon Shore SSSI information.
SAFETY
Clevedon has one of the largest tidal ranges in Britain, so always check tide times and allow plenty of time to return from the foreshore. The rising tide can advance quickly across the low beach and mudflats. The Carboniferous beds are steeply tilted, uneven and often coated with algae, making them very slippery when wet. Wear sturdy footwear with good grip, avoid climbing on old jetty structures, and take particular care when stepping across bedding edges, pools and broken rock.
Extensive soft mud is exposed at low tide and can be dangerously deep or sticky; do not walk out across the mudflats. Stay on firm rock, gravel or established beach surfaces and supervise children closely. Around the Toll House, keep away from unstable cliff faces and do not investigate the mineralised fault by hammering or prising rock. Parts of the shore are protected within the Clevedon Shore SSSI, so conservation restrictions must be respected as well as normal coastal safety precautions.
EQUIPMENT
Clevedon is primarily a location for careful searching rather than heavy hammering. A hand lens, soft brush and small plastic or wooden pick are useful for examining loose Carboniferous limestone and shale, together with tissue, newspaper or small boxes for protecting delicate brachiopods, corals and fish fragments. A camera or phone is especially useful for recording fossils and sedimentary structures that should remain in situ. Sturdy waterproof footwear with good grip is essential. Because the area around the Pier includes a mineralogical SSSI, do not use geological hammers or chisels on protected bedrock or mineralised exposures; collect only loose material where this is permitted.
CLEANING AND TREATING
Most Clevedon fossils occur in hard Carboniferous limestone. Stable limestone specimens can usually be given a brief rinse in clean fresh water to remove salt and surface mud, followed by slow air-drying, but avoid soaking friable shale, specimens containing visible metallic sulphides, or delicate fish material. Never dry fossils rapidly on a radiator or other heat source.
Preparation is usually mechanical. Brachiopods, corals and crinoids are commonly made of calcite and the surrounding limestone is also carbonate, so acid preparation is generally unsuitable and can destroy the fossil as readily as the matrix. Work slowly under magnification with a fine needle, pin vice or small hand tool, following natural boundaries between fossil and matrix. Air scribes or powered preparation tools should be used only by experienced preparators, particularly for thin shells, corals and phosphatic fish fragments.
If a fossil or its matrix is genuinely friable, a dilute solution of Paraloid B-72 in acetone can be used sparingly as a reversible consolidant, but sound limestone fossils do not need to be routinely coated. Avoid irreversible household varnishes on important specimens. Any specimen showing pyrite or other sulphide minerals should be kept dry and monitored for powdering, cracking or acidic decay; do not soak it in water. Unusual fish remains, well-preserved corals or other potentially significant fossils are best left largely unprepared until they can be identified.
FURTHER READING
The Geology of Clevedon Pier & Beach
Clevedon Pier – Minerals and Clevedon Shore SSSI
British Geological Survey – Avon Group
British Geological Survey – Shirehampton Formation
Tucker & Sparks (2024) – Triassic geology of Clevedon
ACCESS RIGHTS
Part of the shore around Clevedon Pier is the Clevedon Shore SSSI, designated for its nationally important fault-related mineralisation. Clevedon Pier’s official geology guidance states that rocks and minerals should not be collected within the SSSI without permission from Natural England and North Somerset Council. Do not hammer, chip, prise or remove material from the mineralised fault, Toll House cliff or other protected exposures. Fossil hunters should concentrate on naturally loose Carboniferous material south of the Pier and only collect where access and ownership allow. See the Natural England SSSI record and the Clevedon Pier mineral and SSSI information.
It is important to follow our ‘Code of Conduct’ when collecting fossils or visiting any site. Please also read our ‘Terms and Conditions‘
LINKS
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