The cliffs at Blue Anchor contain a thin Triassic bone bed from the Rhaetian Penarth series. This is full of reptile, shark, and fish remains, similar to Aust on the River Severn. There are plenty of blocks to split. Jurassic ammonites and reptile bones are also frequently found here.
DIRECTIONS
♦ From the A39, take the B319 or the road from Bilbrook through Old Cleeve to Blue Anchor. Please note, forma access from the B3191, which runs between Watchet and Minehead is now permanently closed to cars due to erosion. Park at the most Eastern side along the promenade and walk east towards Watchet.
♦ On a good day and tides permitting, you can walk from Watchet to Blue Anchor and back. However, the tide can reach very high up the beach at some points and you can be completely cut off. So be careful and make sure you allow plenty of time to get back if you choose this route.
♦ A ramp gains access to the foreshore from the promenade, but is only accessible around three hours after high tide. And this can quickly become cut off soon after low tide.
♦ Postcode to main parking area: Postcode: TA24 6JR
♦ What3Words to the main collecting site: ///cashiers.cactus.indulgent
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PROFILE INFO
FIND FREQUENCY: ♦♦♦ – Blue Anchor is very productive but you have to work for your finds. You will need a good hammer and chisel, as the bone bed is very hard. Search the foreshore for rocks from the bone bed and split these finely. It is also recommended to take samples home and use very small chisels to break them into small pieces. You will be surprised how rich this bed is for teeth.
CHILDREN: ♦♦♦ – As the rocks are very hard, fossils within the bone bed will require heavy hammers to extract. Therefore, this location is not suitable for young children.
ACCESS: ♦♦♦♦ – Access to the beach at Blue Anchor is easy. Park along the seafront and walk down to the beach by means of the concrete slipway.
TYPE: – Blue Anchor is a cliff and foreshore location, although fossils are only really found within the rocks from the bone bed, which can be found scattered along the beach. At the Blue Anchor headland, where you will see some very large rocks, all the beds going eastwards are Jurassic and are covered in our Watchet guide.
FOSSIL HUNTING
Small bones are very common at Blue Anchor, including many fish remains, teeth, spines, small bone fragments and vertebrae. In fact, the fossiliferous Westbury Beds are packed with fish remains. There is also a huge variety of small bones found here, but getting them out and getting them home is a completely different story. It may be easier to look for smaller blocks around the foreshore instead of trying to get bones out of the hard larger blocks, unless you have the right equipment.
The red Triassic cliffs do not contain any fossils, so you will need to walk towards the start of the grey cliffs. At Blue Anchor Point, blocks of bone bed can be seen on the foreshore. Some of these can be huge. Search around these blocks and look for any interesting bones. Once you find a good block, it can take a long time to split it into small pieces. Alternatively, you can take some samples back home for further splitting. Sometimes, nodules can be found that contain larger bones. These tend to be found in sandy pockets together with giant limestone nodules.
GEOLOGY
Blue Anchor Bay (Somerset coast, UK) is a classic place to see the latest Triassic rocks passing up into the earliest Jurassic. Here, the Blue Anchor Fault juxtaposes Jurassic strata against the Triassic marls of the Mercia Mudstone Group, creating an abrupt change in rock type and fossil content along the bay.
The foreshore and low cliffs expose a condensed but highly informative succession spanning the Middle–Upper Rhaetian (Late Triassic) into the Lower Jurassic (Lias Group). The sequence is easiest to understand if you read it from top to bottom (youngest to oldest), noting the repeated alternation of mudstones, shales, and limestone beds that reflect rapid environmental shifts in a shallow sea.
Stratigraphy (top to bottom)
- Blue Lias Formation – the highest beds at Blue Anchor, typically thin limestones interbedded with darker laminated shales. These represent the earliest Jurassic “Lias” seas and often show strong bed-to-bed changes (hard limestone ledges alternating with softer shale). At Blue Anchor, the Blue Lias rests sharply on an irregular surface cut into the Cotham Member mudstones and the pale, fine-grained Langport Member (“White Lias”) limestones below. Together these units mark a key transition interval close to the Triassic–Jurassic boundary.
- Westbury Formation – famous for fossil-rich horizons. At the very top is the Basal Bone Bed. Below, a ~6.4 m interval of dark, fossiliferous shales with thin (often nodular) limestone beds reflects quieter-water conditions with abundant organic material. Occasional sandstones occur in the lowest ~1.2 m. Larger bones can occur but are generally less common. A distinctive mid-section includes the Ceratodus Bone Bed, followed by a gritty bed with fish remains resting on a thin, ripple-marked sandstone—often the most sought-after horizon for collectors.
The upper part of the Westbury Formation transitions into a ~7 m bed that begins with thicker limestones containing common marine fossils such as Rhaetavicula contorta, Chlamys valoniensis, Tutcheria cloacina and Eotrapezium concentricum. Up-section, these beds become more shale-rich, with the final ~1.65 m dominated by shales. This limestone-to-shale shift is a useful visual marker of changing seafloor conditions (from better-oxygenated carbonate deposition to muddier, lower-energy sedimentation).
- Blue Anchor Formation (Mercia Mudstone Group) – mainly grey-green and yellow marls that form much of the cliff exposure. These mudstones record a more restricted, often evaporitic coastal setting compared with the fully marine beds above.
Faulting, features, and what to look for
Toward the eastern end of Blue Anchor, the fossil-bearing succession is abruptly replaced by older Triassic marls that are typically poorly fossiliferous. This sudden change is caused by displacement along the Blue Anchor Fault, which brings contrasting rock packages side-by-side. If you’re walking the shore, you can often spot the difference immediately: richly bedded shales/limestones on one side versus softer, more uniform marls on the other.
One of the most striking visual aspects of the Blue Anchor Formation is the alternating grey and green mudstones, commonly containing nodular gypsum (white to pink; locally “alabaster”). These gypsum nodules formed during evaporation in restricted conditions and are a hallmark of the late Triassic marginal environments preserved here.
This is a detailed stratigraphic breakdown of the Upper Triassic to Lower Jurassic succession at Blue Anchor, Somerset. The section is the type locality of the Blue Anchor Formation and exposes the transition from Mercia Mudstone sabkha deposits upward through the bone-bed-rich Westbury Formation, the White Lias of the Lilstock Formation, and into the basal Blue Lias.
MERCIA MUDSTONE GROUP
Blue Anchor Formation (Upper Triassic — Norian to Rhaetian)
Rydon Member
Bed BA1 — Lower Green And Grey Mudstones And Siltstones (c. 30 m)
Interbedded dark green, greenish-grey and locally pale grey dolomitic mudstones and siltstones, rarely pebbly, forming the lower part of the Blue Anchor Formation at its type locality. The basal boundary is placed at the lowest dark grey mudstone, although the change from the underlying red Mercia Mudstone is gradational over about a metre. These beds represent dominantly terrestrial to marginal-marine sabkha or evaporitic lacustrine conditions, with repeated flooding, evaporation and low-energy sheet sedimentation on a very low-relief coastal plain.
Williton Member
Bed BA2 — Gypsiferous Mudstones And Siltstones (c. 4 m)
Thin beds of greenish-grey and dark grey mudstone with paler shales, gypsum nodules and conspicuous veins. At Blue Anchor these include pink or white alabaster nodules in laminated mudstones, white fibrous gypsum veins parallel to bedding and pink satin-spar veins cutting across the beds. In places the gypsum has been replaced partly by silica. These beds record supratidal to intertidal sabkha conditions with algal-mat development, penecontemporaneous sulphate growth and small-scale syndepositional movement in soft sediment.
Bed BA3 — Upper Sully Beds / Tidal Blue Anchor Beds (top c. 1.8–4.2 m of the formation)
The uppermost Blue Anchor beds become more obviously marine-influenced, with dark green-grey mudstones and siltstones, local burrowed surfaces and horizons yielding body fossils. Trace fossils include Arenicolites, Diplocraterion, Muensteria, Planolites, Rhizocorallium and Siphonites. Body fossils include bivalves and palynomorphs, while fish remains occur from about 3 m below the top and within the highest 1.83 m of the unit. Recorded vertebrates include Saurichthys apicalis, Acrodus minimus, Gyrolepis alberti and Gyrolepis tenuistriatus, with rare indeterminate reptilian bones. These beds represent shallow-water, probably tidally influenced conditions immediately before the main Rhaetian transgression.
Total Thickness Of Blue Anchor Formation At Blue Anchor Point: Approximately 34 Metres Visible In The Generalized Section
PENARTH GROUP
Westbury Formation (Upper Triassic — Rhaetian)
Basal Bone-Bed Interval
Bed BA4 — Basal Bone Bed (c. 0.15 m)
A sandstone bone bed resting sharply on an eroded and bioturbated surface at the top of the Blue Anchor Formation. The bed includes sand-sized quartz grains and pebbles, phosphatic material, coprolites and abundant vertebrate debris. Rip-up cream-coloured clasts derived from the Sully Beds of the underlying Blue Anchor Formation occur in the lag. This is the main transgressive concentration horizon at Blue Anchor and marks the base of the Penarth Group.
Fossil Content
The basal Blue Anchor bone bed is unusual because it is dominated by osteichthyan teeth rather than sharks. Common taxa include Lepidotes, Gyrolepis, Birgeria and Saurichthys, with chondrichthyans such as Lissodus and Rhomphaiodon subordinate. Coprolites, denticles and fish scales are abundant.
Interpretation
This bed represents the initial Rhaetian marine transgression and a high-energy lag concentration formed by reworking on the flooded top of the Blue Anchor Formation.
Bed BA5 — Lower Westbury Black Shales And Shelly Limestones (c. 1.5 m above the basal bed)
Dark grey to black fissile shales, shelly mudstones and thin limestones overlying the basal bone bed. Some limestones contain concentrations of reworked shell debris, channelled lower surfaces and rippled upper surfaces, while fibrous calcite occurs in parts of the limestone facies. These beds record establishment of low-oxygen marine conditions after the main flooding surface, interrupted by brief higher-energy shell and silt events.
Bed BA6 — Intermediate Bone-Bearing Horizon / Sandstone Lens
Older generalized accounts of the Blue Anchor Point section record a second bone-bearing horizon about 1.5 m above the basal bed. This horizon is not always easy to trace in modern exposures, but where recognised it consists of sandy or calcareous bone-bearing material within the lower black shale succession, with quartz grains, abraded bone fragments and scattered vertebrate remains.
Bed BA7 — Upper Bone Bed Beneath The Pleurophorus Bed (c. 0.28 m composite bed, about 5–6 m above the basal bed)
The upper bone bed occurs immediately below the Pleurophorus Bed and is the second principal fossil bone bed sampled in recent work. It is a composite unit of hard grey calcareous sandstone and black shale, finer and more clay-rich at the base and coarsening upwards. It includes thin layers of calcareous bone-bed sandstone, black shale laminae, fibrous calcite and a calcareous sandy bone-bed cap. Quartz grains from the base show solution pits, whereas higher in the bed euhedral quartz overgrowths reflect later cementation in more porous sediment. Pyrite and marcasite are characteristic, showing more strongly anoxic conditions than in the basal bone bed.
Fossil Content
The upper bone bed is dominated by hybodont chondrichthyans, especially Lissodus and Rhomphaiodon, with rarer Parascylloides turnerae, Synechodus and Pseudodalatias. Osteichthyans are much less common than in the basal bed. The bed has also yielded rare and notable finds including an Eomesodon tooth, possible crocodile material, the semi-aquatic choristodere Pachystropheus and the controversial mammal or mammal-like tooth once named Hypsiprymnopsis rhaeticus.
Upper Westbury Shell Beds
Above the upper bone bed are medium-grey shell-bearing limestones and black fissile shales, including the Pleurophorus Bed, which makes the upper bone bed easy to recognise in the field. These beds contain abundant bivalves and fibrous calcite and record fully marine but still shallow and fluctuating shelf conditions.
Total Thickness Of Westbury Formation At Blue Anchor: Approximately 6–8 Metres
Lilstock Formation (Upper Triassic — Rhaetian)
Cotham Member
Bed BA8 — Cotham Member Limestones, Shales And Seismite Bed (c. 4 m)
Grey and grey-green shales, mudstones and limestones resting unconformably on the Westbury Formation. At Blue Anchor the Cotham beds commonly show ripple marks, desiccation cracks and rarer septarian-type nodules, indicating repeated emergence and very shallow-water or lagoonal conditions. A deformed bed attributed to seismic activity is well exposed here and is one of the classic sedimentary structures of the section.
Langport Member (White Lias)
Bed BA9 — Lower White Lias / Porcellanous Limestone
Pale cream to very light grey, hard, fine-grained micritic limestone forming the classic White Lias facies. These resistant porcellanous limestones record a widespread shallow-marine carbonate phase at the very top of the Triassic and form some of the most recognisable pale beds in the succession.
Bed BA10 — Upper Langport Calcareous Mudstones
Calcareous mudstones above the porcellanous limestones, representing the muddier upper part of the Langport Member. At Blue Anchor the contact with the overlying Blue Lias is sharp, and the lowest Jurassic shales locally rest on an irregular surface cut into the Cotham and White Lias beds.
Total Thickness Of Lilstock Formation At Blue Anchor: Approximately 5–6 Metres
LIAS GROUP
Blue Lias Formation (Lower Jurassic — Hettangian)
Basal Blue Lias
Bed BA11 — Basal Paper Shales
Dark, well-laminated mudstones forming the lowest Blue Lias beds visible at Blue Anchor Point. These shales mark the onset of the classic Jurassic limestone–shale cyclicity and represent low-oxygen marine conditions following final drowning of the White Lias platform.
Bed BA12 — Lowest Blue Lias Limestone–Shale Couplets
Thin tabular limestones interbedded with darker laminated shales forming the first true Blue Lias cycles at the top of the section. These beds represent the earliest Jurassic “Lias seas” at Blue Anchor, with repeated switches between muddier and more carbonate-rich shelf deposition. In the wider west Somerset basal Blue Lias framework, early Psiloceras faunas occur in these lowest Hettangian beds.
Fossil Content
Early Jurassic bivalves, shell debris and basal Hettangian ammonites of the Psiloceras group in the wider Blue Anchor–Watchet coast succession.
Total Thickness Of Basal Blue Lias Visible At Blue Anchor Point: Approximately 1–3 Metres
Depositional Environment
The Blue Anchor section records a full environmental progression from supratidal sabkha and evaporitic coastal plain deposits in the upper Mercia Mudstone, into shallow tidally influenced marine conditions at the top of the Blue Anchor Formation, then fully marine Rhaetian black shales and bone beds of the Westbury Formation, followed by very shallow lagoonal and carbonate-platform conditions in the Cotham and White Lias, and finally the open marine Jurassic limestone–shale cycles of the basal Blue Lias.
Total Thickness Covered Here: Approximately 46–51 Metres Visible In The Main Blue Anchor Point Section, Though Faulting Locally Repeats Parts Of The Succession
References
Warrington, G. & Whittaker, A. (1984). The Blue Anchor Formation and Rhaetian succession of west Somerset.
Hamilton, F.W. & Whittaker, A. (1977). Blue Anchor Point and the Penarth Group / basal Lias succession.
Korneisel, D. et al. (2024). Microvertebrates from the Rhaetian bone beds at Blue Anchor Bay, Somerset.
British Geological Survey Lexicon: Blue Anchor Formation, Westbury Formation and Lilstock Formation.
Blue Anchor Point GCR account and west Somerset field guides.
ACID PREP
The Blue Anchor bone bed (often referred to as part of the Rhaetian bone-bed horizon within the Westbury Formation) is typically a thin, locally patchy layer formed as a high-energy lag deposit when the sea advanced over older Triassic mudstones. Rather than preserving fossils neatly “in place,” it commonly concentrates tough, durable material: vertebrate teeth and bone fragments, fish debris (scales, denticles), phosphatic pebbles, small clasts ripped up from underlying mudstones, and occasional shell or limestone fragments.
That mix is exactly why acid-based preparation can be useful for this bed: the cement and matrix are often carbonate-rich, while many of the collectible microfossils (especially the smaller vertebrate elements) are more phosphate-rich and can survive careful, controlled chemical prep better than the surrounding carbonate.
What acid prep is best for (and what it isn’t)
Acid prep is usually most effective here when your aim is bulk recovery—freeing lots of small, isolated fossils for sorting—rather than producing a single “display specimen.” Bone-bed material is commonly reworked and fragmentary, so the payoff is often in the microfossils you can’t easily extract by hand.
A practical, non-technical workflow overview
It helps to frame acid prep as “lab-style processing” rather than a quick trick.
- Start by understanding your matrix. A small test on non-valuable matrix can tell you whether the rock is likely to respond (carbonate-rich material reacts readily; clay-rich material may not).
- Work in controlled cycles. Short exposures with long rinses between them are generally safer than prolonged soaking, because they reduce the chance of softening or etching fossil surfaces.
- Rinsing matters as much as the acid. Bone-bed residues can trap dissolved salts; if those salts crystallise during drying they can crack or flake delicate pieces. Thorough rinsing and patience reduces this risk.
- Expect a lot of “non-fossil” residue. Because the bed is a lag deposit, you’ll often process plenty of pebbles and mudstone clasts along with the fossils. The real results come from sieving and careful picking under magnification.
- Fragile pieces may need stabilising. Small bones and teeth can be porous or fractured; some collectors use suitable consolidants (applied sparingly) to help pieces survive handling and drying.
Common pitfalls with Blue Anchor bone-bed material
- Over-prepping: Rushing the process can leave fossils chalky, etched, or weakened—even if they don’t fully dissolve.
- Hidden weak spots: Some fossils look solid until they dry, then split along old cracks. Gentle handling and slow drying help.
- Iron sulphides (pyrite): Dark, organic-rich horizons can contain minerals that cause long-term deterioration if stored damp or sealed without care. Keeping material dry and well-ventilated after proper rinsing is important.
Safety note
Even “mild” acids are hazardous. If you choose to do chemical preparation, treat it like proper chemical handling: use appropriate eye/skin protection, good ventilation, acid-safe containers, and follow local rules for neutralisation and disposal. If you’re not set up for safe chemical work, stick to mechanical preparation and selective collecting.
SAFETY
Common sense when collecting at all locations should always be used and tide times should always checked before visiting. You can easily be cut off by the tide at Blue Anchor, as the sea reaches the cliff, especially round the first headland. You can walk to Watchet from here, but you should ensure you have left enough time for your return or to reach your destination. Care must be taken when splitting, hitting and breaking these rocks, as rock splinters can penetrate the body, especially the eyes. Therefore, you should always wear safety goggles. When using chisels, care must be taken to prevent breaking fingers or damaging hands.
EQUIPMENT
Many fossils can simply be collected from the fragments of bone bed along the foreshore, especially along the tide line. However, any large boulders from the bone bed will require strong tools to break them. The bed is so hard that splitting it is almost impossible unless a natural fault line or crack can be found. You will need a heavy hammer, chisels and safety goggles.
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.
ARTICLES
- Giant file clams: A common fossil as an exciting document of Earth history
- Bryozoans in the English Chalk
ACCESS RIGHTS
This site is an SSSI. 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
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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