Thorncombe Beacon yields a diverse range of species of ammonites, shells (including brachiopods and bivalves), some superb starfish specimens, crinoids, belemnites and much, much more. However, the rocks are very hard so it can be a lot of work to extract fossils.
DIRECTIONS
♦ Thorncombe Beacon is best reached via Seatown. Follow the narrow lane, just opposite the Castle Inn in Childeock. This road is not suitable for large vehicles, because of its width. There is a small car park, run by the Anchor Inn, at Seatown, which is highly recommended, as parking elsewhere is very limited.
♦ Parking along the roadside at the bottom is possible between the 1st October and the 24th May. The double yellow line parking restrictions only apply in peak season.
♦ Thorncombe Beacon is on your left (east) from the car park at Seatown.
♦ There is a charge for parking at Seatown.
♦ Postcode to parking: DT6 6JU. Google maps link.
♦ Fossil Location: What3Words: ///perused.silver.bless
PROFILE INFO
FIND FREQUENCY: ♦♦♦♦ – Fossils are frequently found, however they are less likely to be found loose. This is a specialist location in which you ideally need heavy lump hammers and heavy duty chisels to split blocks.
CHILDREN: ♦ – The foreshore at Thorncombe Beacon is very rocky. This site is only suitable for families with older children, as some of the boulders are extremely hard and large. Although you can find fossils on the foreshore, most have to be split from the rock using a geological hammer.
ACCESS: ♦♦♦ – There is a car park practically on the beach, with toilets and a pub next to it. However it can be a difficult walk when the beach between Seatown and Thorncombe Beacon Cliff is built up with pebbles, and then a field of large boulders awaits you round the corner.
TYPE: – This is a foreshore and cliff location, so fossils can be found in both. Fossils are found in rocks on the foreshore,
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FOSSIL HUNTING
Thorncombe Beacon is a well-known fossil collecting site on the Dorset coast, but it is important to note that it lies within a Site of Special Scientific Interest (SSSI) and forms part of the Jurassic Coast World Heritage Site. Collectors must therefore follow the Fossil Code of Conduct at all times. Hammering directly on the cliff or bedrock is not permitted, and digging into the cliff or foreshore is strictly forbidden. The land is privately owned and damage has previously been caused by people using power tools and other inappropriate methods. Such activity is illegal and may result in prosecution. Fossil collecting should therefore be limited to loose material that has naturally fallen onto the foreshore.
Most fossils at Thorncombe Beacon come from loose blocks of the Junction Bed, a distinctive series of yellow, iron-rich limestones that weather out onto the beach from the cliffs above. These rocks often occur as layered blocks scattered across the foreshore and can contain large numbers of fossils. Many specimens can be found simply by searching the surface of these rocks, as weathering frequently reveals ammonites and shells. Carefully splitting loose blocks can sometimes reveal beautifully preserved fossils within the rock.
Ammonites are particularly abundant in the Junction Bed and include a wide variety of species typical of the Middle Jurassic. Common forms include Amaltheus margaritatus and Lytoceras fimbriatum, but collectors may also encounter species such as Pleuroceras spinatum, Amaltheus stokesi, Amaltheus subnodosus, Harpoceras serpentinum, Harpoceras falciferum, Dactylioceras commune, Dactylioceras tenuicostatum, Hildoceras bifrons, Eleganticeras elegantulum, Tiltoniceras antiquum, Tiltoniceras scissum, Coeloceras crassum and Paltarpites. Many of these ammonites occur as flattened impressions within the limestone, while others may be preserved three-dimensionally within nodules.
Other fossils are also common within the Junction Bed. Belemnites are frequently encountered, particularly species such as Passaloteuthis and Acrocoelites. Crinoid fragments are abundant and occasionally more complete stems can be found preserved within the limestone. Brachiopods such as Terebratula and Rhynchonella are also present, along with numerous bivalves including Gryphaea, Pecten and Trigonia. Gastropods are less common but may occasionally be discovered within the rock. Trace fossils produced by burrowing organisms can also be seen on bedding surfaces.
One of the most interesting fossils found at Thorncombe Beacon is the brittlestar Palaeocoma egertoni. These delicate fossils are often discovered simply lying within weathered rocks on the foreshore rather than inside freshly split blocks. They originate from the Eype Starfish Bed, a distinctive bedding plane that occurs within the Thorncombe Sands Member and the Downcliff Sands Member. These beds occasionally weather out onto the beach, revealing beautifully preserved brittlestars preserved flat on the bedding surfaces. Because they are extremely fragile, specimens should be handled with great care if encountered.
It is also worth keeping an eye on the foreshore for occasional slips of Upper Greensand, which may sometimes become exposed after storms or periods of cliff collapse. In its freshly exposed state this rock can be relatively soft, becoming harder as it dries and oxidises in the air. Fossil shells can sometimes be found within these deposits and, when the rock is still soft, they can be extracted quite easily. As with all collecting along this stretch of coast, however, only loose material should be collected and the cliffs themselves should never be disturbed.
GEOLOGY
Thorncombe Beacon forms one of the highest cliffs on the Dorset coast, rising to around 157 metres above sea level. The cliff exposes a complex succession of Lower Jurassic rocks overlain by much younger Cretaceous deposits, providing an excellent example of the geological history of the Jurassic Coast. From the top of the cliff downward, the sequence records a transition from the Early Cretaceous back into the Lower Jurassic marine sediments that form much of this coastline.
At the top of the cliff lie the Upper Greensand Formation and the Gault Formation, both deposited during the Early Cretaceous. The Gault consists mainly of dark marine clays that accumulated in relatively deep water conditions. Above this sits the Upper Greensand, a glauconitic sandstone that formed in a shallow marine environment as sea levels fluctuated during the Cretaceous. These Cretaceous rocks cap the cliff and form the upper slopes of Thorncombe Beacon.
Beneath the Cretaceous deposits are the Lower Jurassic rocks of the Bridport Sand Formation, which make up a large part of the cliff face. These rocks consist mainly of yellow-brown sands and sandstones that were deposited in shallow marine environments during the Early Jurassic. The sands weather easily and are prone to slumping, which is why large quantities of material regularly fall from the cliff and accumulate on the foreshore below.
Within the Bridport Sand Formation are several distinct members that can be recognised along the cliff. The Downcliff Clay Member forms a darker, more clay-rich interval within the sequence and represents a brief change in sedimentation conditions when finer material was deposited in quieter marine waters. Immediately beneath this lies the Beacon Limestone, historically known as the Junction Bed, which forms a distinctive fossil-rich limestone horizon. This bed marks a boundary between different depositional phases within the Lower Jurassic sequence and is the source of many of the ammonites found along the beach.
Below the Beacon Limestone lies the Thorncombe Sands Member, consisting mainly of fine-grained sands and sandstones. These sediments were deposited in shallow marine conditions and form an important part of the cliff section. At the base of this member is the distinctive Eype Starfish Bed, a thin but well-known bedding plane famous for its fossil brittlestars. This horizon occurs at the boundary between the Thorncombe Sands Member and the underlying Downcliff Sands Member.
The Downcliff Sands Member consists of micaceous siltstones and sandy sediments that were deposited in relatively calm marine conditions. Fallen blocks from this bed sometimes appear on the foreshore, and it is within these slabs that the brittlestar Palaeocoma egertoni can occasionally be found preserved on bedding surfaces. These fossils are extremely delicate and difficult to extract intact, which is why complete specimens are rarely recovered.
At the base of the exposed sequence lies the Eype Clay Member, a darker clay unit belonging to the Lower Jurassic. These marine mudstones represent quieter offshore deposition and form the lowest visible beds along this section of the coast. The Eype Clay occasionally contains nodules belonging to the Eype Nodule Bed, although these are often obscured by slumped material from higher in the cliff.
This is a full stratigraphic breakdown of the Lower Jurassic succession exposed at Thorncombe Beacon, Dorset. It covers the classic Eype Clay, Down Cliff Sand and Thorncombe Sand sequence beneath the Cretaceous cap, with the principal named horizons used by collectors and researchers, including the Three Tiers Sandstone, Eype Nodule Bed, Day’s Shell Bed and Eype Starfish Bed.
LIAS GROUP
Dyrham Formation (Lower Jurassic: Pliensbachian)
Eype Clay Member
The Eype Clay Member forms the lower part of the Thorncombe Beacon cliff section and consists mainly of pale grey, micaceous, variably silty mudstone with numerous small siderite nodules. It continues eastwards from Seatown beneath Thorncombe Beacon and is commonly obscured in places by slipped material from the overlying sands.
Typical ammonites include Amaltheus margaritatus, Pleuroceras spinatum and related upper Pliensbachian forms, with bivalves, brachiopods and benthic fauna also common.
Three Tiers Sandstone
A sandstone horizon at the base of the Eype Clay Member used by BGS to define the lower boundary of the member. It forms a useful lower marker beneath the mudstone-dominated Eype Clay succession.
Lower Eype Clay
Pale grey silty mudstones with scattered siderite nodules and thin sandy partings. Fossils are present throughout, though generally more scattered than in the better-known shellier horizons higher in the member.
Eype Nodule Bed
A conspicuous nodule band in the middle of the member, marked by rounded calcareous or sideritic nodules. This is one of the main internal marker horizons at Thorncombe Beacon and can be more fossiliferous than the surrounding mudstones.
Middle Eype Clay
Pale to medium grey silty mudstones with many nodules and local sandy partings. This interval forms much of the lower soft-cliff profile and yields ammonites, bivalves and crinoid debris.
Day’s Shell Bed
A fossil-rich shelly horizon close to the top of the member, lying about 0.9 m below the Starfish Bed. It is an important marker immediately beneath the overlying sandy interval.
Upper Eype Clay
Silty mudstones and sandy mudstones transitional upwards into the Down Cliff Sand Member. Fossils include upper Pliensbachian ammonites, bivalves and shell-rich concentrations near the top.
Total Thickness Of Eype Clay Member: Approximately 60 Metres
Down Cliff Sand Member
The Down Cliff Sand Member succeeds the Eype Clay and consists mainly of fine-grained sand, silty sand and sandy mudstone. At Thorncombe Beacon it forms a more resistant part of the cliff and includes the famous starfish-bearing basal sandstone.
Typical fossils include upper Pliensbachian ammonites, bivalves, crinoid debris and the classic brittle stars from the Starfish Bed.
Eype Starfish Bed
A famous fine-grained sandstone at the base of the Down Cliff Sand Member. Its underside preserves brittle stars and crinoid remains, including Palaeocoma and Balanocrinus, and it is one of the most distinctive marker beds on this part of the Dorset coast.
Lower Down Cliff Sands
Fine-grained sandstones and sandy mudstones overlying the Starfish Bed, forming a ledge-forming interval. Fossils are less evenly distributed than in the Eype Clay, but shelly concentrations and ammonites occur.
Upper Down Cliff Sands
Sand and silt with subsidiary sandy mudstone, transitional upward into the more sandstone-dominated Thorncombe Sand Member.
Total Thickness Of Down Cliff Sand Member: Approximately 10–20 Metres
Thorncombe Sand Member
The Thorncombe Sand Member forms the upper Jurassic part of the cliff at Thorncombe Beacon and consists mainly of yellow-weathering silty very fine-grained sands, locally bioturbated and with hummocky cross-bedding. An impersistent limestone about 0.3 m thick may occur in the middle of the member.
Fossils are generally less abundant than in the mudstone units below, but bivalves, trace fossils and occasional ammonites occur, commonly in harder sandstone bands and dogger-like concretions.
Lower Thorncombe Sands
Yellow-weathering silty sands and sandy silts forming resistant ledges above the Down Cliff Sand Member.
Main Thorncombe Sandstone Sequence
Sand-dominated cliff-forming succession with strong bioturbation and more massive weathering than the units below. Fallen sandstone blocks from this interval commonly show trace fossils clearly on bedding surfaces.
Impersistent Mid-Member Limestone
A local limestone horizon, typically around 0.3 m thick where present, within the Thorncombe Sand Member.
Total Thickness Of Thorncombe Sand Member: Approximately 20–35 Metres
Gault Formation (Lower Cretaceous)
Gault Clay
Soft marine clay capping the Jurassic sands beneath the Upper Greensand. At Thorncombe Beacon this forms part of the Cretaceous cap above the Lower Jurassic cliff sequence.
Upper Greensand Formation (Lower Cretaceous)
Upper Greensand Cap
Golden-brown to greenish sandstone forming the uppermost cap of Thorncombe Beacon. This resistant unit gives the hill much of its prominent profile above the softer Jurassic beds below.
Total Thickness Covered Here: Approximately 95–125 Metres
References
British Geological Survey Lexicon of Named Rock Units: Eype Clay Member; Down Cliff Sand Member; Thorncombe Sand Member; Dyrham Formation.
British Geological Survey Memoir: Geology of South Dorset and South-East Devon and its World Heritage Coast.
Discovering Fossils: Seatown and Thorncombe Beacon field guides.
Wessex Coast Geology: Seatown, Thorncombe Beacon and Eype sections.
UK Fossils: Thorncombe Beacon fossil collecting guide.
EQUIPMENT
Thorncombe Beacon is a location where you often have to work for your finds, but it is important to remember that it lies within a Site of Special Scientific Interest (SSSI) and forms part of the Jurassic Coast World Heritage Site. As such, hammering directly on the cliff or bedrock is not permitted, and collecting should only be carried out on loose material that has naturally fallen onto the foreshore.
Most fossils are found within loose blocks of the Beacon Limestone (formerly known as the Junction Bed) that have weathered out of the cliffs. A strong geological hammer can be useful for breaking apart loose rocks and nodules that may contain fossils, and a splitting chisel may help to open layered blocks more cleanly. Safety goggles are strongly recommended when splitting rocks.
Because many fossils from this location can be fragile, particularly brittlestars such as Palaeocoma egertoni, it is advisable to bring wrapping materials such as tissue, newspaper or bubble wrap to protect your finds. Small specimen boxes or containers can also be useful to prevent delicate fossils from being damaged during transport.
Sturdy walking boots with good grip are recommended, as the foreshore can be uneven and slippery, particularly after wet weather or high tides. As always along this stretch of coast, collectors should remain aware of tide times and avoid working too close to the unstable cliffs.
SAFETY
Common sense should always be used when collecting fossils at Thorncombe Beacon, and checking tide times before setting out is essential. If you are walking from Seatown, it is particularly important to double-check the tides, as once you round the headland at Thorncombe Beacon you cannot see how high the tide is at Seatown. The tide frequently reaches the base of the cliff along this stretch of coast and it is easy to become cut off once you are past the headland. For this reason, it is safest to plan your trip around low tide and begin your return journey while the tide is still falling or at its lowest point.
The cliffs at Thorncombe Beacon are very high and prone to frequent rockfalls and landslips. Large sections of the cliff regularly collapse without warning, particularly after heavy rain or stormy weather. Fossil hunters should never work directly beneath the cliffs and should keep a safe distance at all times, as falling rocks and debris pose a serious danger.
The foreshore itself can also be hazardous. The beach is made up of large, uneven and often slippery rocks, many of which are coated in algae or become slick when wet. Walking across these rocks can be difficult and there is a significant risk of slipping or twisting an ankle, especially when carrying equipment or concentrating on searching for fossils. Sturdy walking boots with good grip are strongly recommended to help reduce the risk of injury.
As with all coastal collecting, always remain aware of changing sea conditions, watch for rising tides and avoid collecting during rough weather or poor visibility. Taking care and planning your visit properly will ensure that fossil collecting at Thorncombe Beacon remains both safe and enjoyable.
CLEANING AND TREATING
Begin by removing any loose sediment very carefully using a soft toothbrush. Take your time, as many fossils—particularly pyritic specimens—are fragile and easily damaged. Once cleaned, fossils should be desalinated by soaking them in fresh water for at least 24 hours to remove residual salt. After soaking, allow specimens to dry naturally at room temperature. Do not dry them on radiators or other heat sources, as rapid drying can cause cracking or long-term damage.
Once fully dry, we recommend sealing fossils with Paraloid B-72, dissolved in acetone. This is a museum-grade consolidant that is widely available in pre-mixed bottles. Paraloid B-72 is stable, long-lasting, and does not yellow or react chemically over time. Importantly, it is also fully reversible, making it suitable for scientifically important or display-quality specimens.
Some collectors prefer to treat ammonites with artists’ varnish. This is acceptable for common species that are not of scientific importance, as it enhances colour and contrast and can make a specimen really “pop”. However, varnish is not reversible and is therefore not recommended for rarer or research-grade fossils.
ARTICLES
ACCESS RIGHTS
This site is an SSSI and forms part of the UNESCO World Heritage Jurassic Coast. This means you can visit the site, but hammering the bedrock is not permitted. For full information about the reasons for the status of the site and restrictions please download the PDF from Natural England – SSSI Information – West Dorset
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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