Tidmoor Point, on the edge of The Fleet lagoon opposite Chesil Beach, is a small but highly productive Oxford Clay locality. Best known for its pyritised and limonitic ammonites, the low cliffs and foreshore regularly yield a wide range of fossils, including belemnites, crinoids, crustaceans, fish and occasional reptile remains. Despite its modest size, it remains one of the most reliable sites for collectors searching for well-preserved Jurassic fossils.
FIND FREQUENCY: ♦♦♦♦ – This has long been regarded as a highly fossiliferous locality. However, over-collecting in recent years has clearly impacted on the numbers of fossils. The very slow erosion rate of the gentle lapping waters of The Fleet means fresh fossils are most likely to be exposed after winter storms.
CHILDREN: ♦♦♦ – This can be a fair walk for children, so the site is more suitable for older children. Note also that the mudflats are dangerous, so ensure children to not venture onto these.
ACCESS: ♦♦ – The walk is quite long and military-range closures can affect the route. See Access Rights for the reserve’s guidance on shore access and loose fossil collecting.
TYPE: Fossils are found along the foreshore, washed from the small cliffs.
DIRECTIONS
♦ Take the Chickerell Link Road (B3157) from Dorchester and drive to the junction with Chickerell Road. Turn left at the traffic lights onto Chickerell Road (signposted the Jurassic Coast Road), passing the Chickerell Army Training Camp on the right.
♦ At a distance of just under a kilometre, you will see a lay-by opposite Tidmoor Holiday Cottages at DT3 4DG. Park here. If you overshoot, turn left into Putton Lane (there is a small Post Office on the corner, opposite the Art House Cafe)) and park here instead.
♦ Cross over Chickerell Road on foot and walk down the side of Tidmoor Holiday Cottages, along a concrete path that runs past the Army firing ranges to The Fleet. Obey range signs, gates, red flags and closures. Follow any signed public-path diversion; do not use the shore to bypass a closure. Check the current Chickerell range notice before visiting.
♦ Where the signed public path is open, at the bottom of the path bear slightly right and go through a gate, following the narrow path, crossing the wooden planking, until you reach the final metal gate. Bear right and walk more or less parallel to the coast, until you finally reach Tidmoor Point.
♦ The concrete ramp and broken wooden jetty are landmarks at the point. Before leaving the coast path, read the shore-access guidance under Access Rights.
♦ Postcode to Parking: DT3 4DA, Google Maps
♦ Location: What3Words: ///elder.thinker.receiving
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FOSSIL HUNTING
Tidmoor Point is renowned for its pyrite and limonitic casts of small ammonites of the Lamberti Zone of the Oxford Clay Formation and may have supplied the type specimen of Quenstedtoceras lamberti, although the exact origin of some historical Weymouth specimens is uncertain. The cliff here is very low and much slipped, with ammonites, belemnites (including Hibolithes hastatus) and other fossils recorded on, or just above, the beach. These include ammonites (Quenstedtoceras leachii, Quenstedtoceras henrici, Kosmoceras spinosum and Kosmoceras compressum), as well as ossicles and parts of the stems of Pentacrinus crinoids, casts of bivalves (Nucula, Grammatodon, numerous Gryphaea lituola and the dwarfed, Gryphaea dilatata). Most ammonites are small. Also to be found here are parts of lobsters and crabs, the teeth of the shark, Sphenodus, plesiosaurs and marine crocodile teeth, with occasional bones from turtles and fish.
The public coast path offers views of The Fleet and its bird life. Do not dig into the banks or cliffs: the reserve’s guidance prohibits fossil extraction from these soft exposures. Fossils become exposed naturally as water and weather break down the sticky clay. Tidmoor Point also forms part of the UNESCO World Heritage Site of the Jurassic Coast, and is also a Ramsar (wetland) site and a Special Area of Conservation Interest, among other designations.
The most fossiliferous spot is at the northwest extremity of the point. The classic Lamberti-zone fauna is Upper Callovian; younger Lower Oxfordian Oxford Clay crops out farther east towards Furzedown.
Tidmoor Cove lies southeast of the point. Do not attempt to cross to the cove across the mudflats, despite it looking to be a shortcut. This is dangerously deep mud, which must be avoided. Use the public coastal path towards Littlesea Caravan Park to approach the cove; the shore-access guidance under Access Rights applies here too. At Tidmoor Cove, the fossils are similar to Tidmoor Point, but large specimens of Gryphaea dilatata have been recorded from the beach. The Mariae Zone crops out beneath the caravan site, containing the ammonite, Cardioceras mariae (listed historically as Quenstedtoceras mariae), among others.
Some of the main scientific milestones connected with Tidmoor Point include its long-standing reputation as one of England’s classic Oxford Clay ammonite localities and later work on the Callovian–Oxfordian boundary faunas from the site.
1947 – W. J. Arkell described Tidmoor Point as one of the most celebrated fossil localities in England
Tidmoor Point was already recognised by Arkell as a classic Oxford Clay locality because of its prolific pyritic ammonite fauna. This is one of the clearest historic statements of the site’s importance.
1999 – Chapman reviewed the Oxfordian-age clays east of Tidmoor Point
Later geological work treated the Tidmoor Point area as an important Oxfordian coastal exposure within the wider Fleet Lagoon succession, helping place the fossil-bearing clays into a clearer stratigraphic framework.
2003 – Tidmoor Point was included in discussion of classic Oxford Clay sections for the Oxfordian Stage
Work on the search for a global standard for the Oxfordian Stage included the Fleet Lagoon Oxford Clay sections, specifically mentioning Tidmoor Point among the classic localities reviewed for their ammonite faunas and boundary importance.
Modern collecting – Tidmoor Point remains best known for pyritised ammonites such as Quenstedtoceras
Modern field guides continue to highlight Tidmoor Point for pyritised ammonites, especially Quenstedtoceras, together with small belemnites and crinoid ossicles weathering from the Oxford Clay.
GEOLOGY
Tidmoor Point sits on the shoreline of The Fleet—the long, sheltered lagoon behind Chesil Beach. Because this is a lagoon margin rather than an open coast, you’ll typically see low clay edges, mud/silt flats, and slumped foreshore rather than tall, clean cliff faces. The geology is still very informative, but exposure quality depends heavily on recent weather, water levels, and how much the surface has been washed clean.
The bedrock is the Oxford Clay Formation, deposited across the Callovian–Oxfordian transition. At Tidmoor Point itself, slipped grey Stewartby Member clays supplied the classic late Callovian pyritic ammonite fauna. Older, darker Peterborough Member mudstones occur in patches west of the point, while younger Weymouth Member clays crop out to the east. These are separate, incomplete exposures, rather than one continuous section through all three members.
The clay becomes sticky and slippery when wet and is commonly slumped, so original bedding can be difficult to follow. Harder nodules may remain after the surrounding clay has broken down. Many small ammonites are loose, reworked pyritic or limonitic internal moulds: their position on the modern shore is not a reliable bed number.
The Oxford Clay accumulated as marine mud in the Jurassic, long before the modern Fleet lagoon and Chesil barrier formed. Its fine-grained sediment and fossil assemblages record that ancient sea; the sheltered lagoon now controls how slowly the clay is eroded and how fossils become exposed. The present position behind Chesil Beach should not be used to reconstruct the Jurassic depositional environment.
This is a composite stratigraphic breakdown of Tidmoor Point and the immediately adjacent East Fleet shore, where low slipped banks and seaweed-covered foreshore expose only fragments of the Kellaways and Oxford Clay succession on the flank of the Weymouth Anticline. The locality is historically important for its famous pyritized Upper Callovian ammonite fauna, but the section must be treated honestly as faulted, slumped and partly ex situ rather than as a clean continuous cliff log.
TP labels are editorial identifiers for observed or correlated intervals, not formal published bed numbers. The western Butterstreet–East Fleet–Chickerell exposures below are separate reference contexts; the actual Tidmoor banks and eastern Oxfordian shore are distinguished throughout.
Section Note
The cited GCR account supplies no continuous measured bed-by-bed log for the main Tidmoor ammonite-producing ground, because the exposures are low, slipped, intermittently visible and locally repeated or obscured. The numbered units used below are therefore a practical site-use scheme tied to real lithological and stratigraphic packages recognized in the literature: trace Kellaways exposures west of the point, patchy Peterborough Member mudstones in the bay west of the promontory and around Chickerell Hive Point, the slumped Stewartby Member banks of Tidmoor Point itself, and the younger Weymouth Member cropping out east of the point.
ANCHOLME GROUP
Kellaways Formation (Callovian)
Kellaways Clay Member
Bed TP1 — Trace Kellaways Mudstones West Of Tidmoor Point
Farther west, around Butterstreet Cove and the East Fleet stream, intermittent Kellaways exposures provide older regional context; they are not beds measured in the Tidmoor Point banks. Grey, locally silty to muddy sandstone and sandy mudstone contain shell fragments and bivalves including Goniomya literata, Nanogyra, Pholadomya and Pleuromya uniformis, together with Cadoceras and a nautiloid. Farther toward East Fleet, large septarian concretions and large body chambers of Proplanulites have been recorded. These exposures represent Kellaways Clay Member facies; a separate Kellaways Sand Member is either extremely thin or not demonstrable here. Ammonite evidence indicates Koenigi-zone levels in the East Fleet–Butterstreet sector. The loose Enodatum Subzone septarian concretion from Butterstreet Cove was instead discussed by Cox and Page as possible basal Oxford Clay; it should not be assigned securely to the Kellaways Formation. Depositional environment: quiet marine shelf mud with intermittent silt and sand influx, shell concentrations and early-cemented septaria.
Butterstreet Reference: Lower Sandy Clay (Approximately 0.25 m Recorded)
Page’s historically recorded small Kellaways exposure on the south-facing Butterstreet shore included bluish-grey sandy clay with shell debris. This is an adjacent reference observation, not a bed measured at Tidmoor Point.
Butterstreet Reference: Upper Muddy Sandstone (Approximately 0.05 m Recorded)
Thinly bedded grey muddy sandstone with bivalves, an ammonite and a nautiloid overlies the sandy clay in that reported exposure. The two small lithological units remain separate and are not combined into a false full-formation thickness.
East Fleet Reference: Septarian Kellaways Interval
The small headland south of East Fleet yielded traces of a bed with large septarian concretions and Proplanulites body chambers. A possible sandier upper member was historically reported farther along the shore but not confirmed by the later survey; its uncertain rank is preserved.
Oxford Clay Formation (Callovian To Lower Oxfordian At This Locality)
Peterborough Member
Lower Peterborough Reference: Jason-Fauna Clay Near Chickerell
Between East Fleet and Chickerell Hive Point the GCR records approximately 1 m of grey clay with large septarian concretions, sometimes containing Kosmoceras jason. This is an explicitly western reference interval beneath the higher septarian shales, not an additional measured Tidmoor bank.
Bed TP2 — Septarian Bituminous Mudstones Of The Peterborough Member
Patchy outcrops on the north-east side of Chickerell Hive Point expose higher beds than the East Fleet Kellaways and belong to the Peterborough Member of the Oxford Clay. They are dark grey to brown bituminous shale and mudstone with layers of large septarian cementstone concretions, some up to about 0.6 m in diameter. Recorded ammonites include Kosmoceras castor and Kosmoceras grossouvrei, within western Peterborough Member patches that the GCR collectively assigns to the Jason–Athleta interval, below the classic Tidmoor Point Lamberti fauna. Typical fossils are crushed ammonites, belemnites and shell debris preserved in organic-rich shale and septarian concretions. Depositional environment: low-energy offshore mud accumulation under relatively dysoxic bottom-water conditions, with early diagenetic cementation forming the septaria.
Bed TP3 — Higher Peterborough Mudstones West Of Tidmoor Point
In the bay on the west side of Tidmoor Point, shales with Kosmoceras transitionis have been recorded from slightly higher Oxford Clay levels. These beds are still within Peterborough Member facies and represent the upward continuation from the darker bituminous septarian shales toward the upper Callovian mudstones below the slipped banks of the point itself. Lithologically they were probably still dark grey to brown organic-rich clay and shale, but the exposure is too poor and fragmentary for a formal local log. Their importance lies in showing that Peterborough Member strata continue almost to Tidmoor Point, even though the famous pyritic fauna of the point itself is mostly derived from higher beds.
Peterborough Member Note
At Tidmoor Point and its western approach, the Peterborough Member is exposed only in isolated patches, but the recorded faunas show that the locally represented interval spans at least Jason- to Athleta-age Oxford Clay. The continuous measured reference section for these beds in the district is nearby Crookhill Brickpit rather than Tidmoor Point itself.
Stewartby Member
Bed TP4 — Slipped Stewartby Mudstones Of Tidmoor Point
The low banks of Tidmoor Point itself are made of slipped pale- to medium-grey, smooth-textured, variably calcareous mudstones that correspond to Stewartby Member facies. Occasional pale phosphatic and calcareous nodules occur, many of them representing ammonite body chambers. Compared with the darker Peterborough shales below, these clays are less fissile, more blocky and generally less strongly bituminous, but slumping and weathering have blurred bedding and destroyed any continuous section. Ammonites and other macrofossils are usually preserved as pyritized internal moulds. Depositional environment: offshore marine mud deposition, still low-energy and below normal wave base, but in a paler and more calcareous facies than the Peterborough Member below.
Context TP5 — Reworked Pyritic Lamberti-Zone Foreshore Assemblage
On the flat foreshore below the point, mud lumps and thin clay partings yield the classic pyritic and limonitic ammonite nuclei for which Tidmoor Point is famous. This is not a formal published bed, but a practical site-use horizon representing fossiliferous mud derived mainly from the upper Stewartby Member. The assemblage is stratigraphically mixed and largely ex situ, yet it is dominated by Upper Callovian faunas of the Quenstedtoceras lamberti Zone, with evidence of both the Henrici and Lamberti subzones; a late Athleta Zone, Spinosum-subzone component may also be represented.
Typical Fossils And Ammonites
The classic Tidmoor Point fauna includes genera such as Alligaticeras, Distichoceras, Euaspidoceras, Grossouvria, Hecticoceras, Kosmoceras, Pachyceras, Paralcidia, Peltoceras and Quenstedtoceras. More specifically recorded forms include Quenstedtoceras ex gr. lamberti, Q. leachii, ammonites of the Kosmoceras spinosum group, Euaspidoceras hirsutum, Distichoceras bicostatum and Pachyceras lalandeanum. Associated fossils include common belemnites, especially Hibolithes hastatus (the GCR also records ?Lagonibelus), nautiloids such as Paracenoceras, pyritized bivalves including Grammatodon and Nuculana, cerithiid gastropods and pentacrinoid stem fragments. The usual preservation is as small pyritic internal moulds or limonite after pyrite, whereas larger fossils commonly survive only as body-chamber nodules.
Historical And Stratigraphic Caution
Although Tidmoor Point supplied many classic Oxford Clay ammonites and almost certainly yielded some important type material, the exact source of some older museum specimens is uncertain. Some may have come from now-obliterated brickpits, Radipole Backwater or Weymouth Pottery rather than from the modern foreshore. This is one of the main reasons why the historic faunal lists cannot be converted into a spurious precise cliff log: the fauna is real and very important, but the modern exposure is mixed, slipped and only partly in situ.
Bed TP6 — Stewartby–Weymouth Boundary Interval
The Stewartby–Weymouth boundary is difficult to locate at Tidmoor Point. The Lamberti Limestone that marks the top of the Stewartby Member in much of England is absent in Dorset, and the two members cannot be separated reliably by lithology in local field mapping. Ammonite evidence distinguishes late Callovian from early Oxfordian strata, but mixed loose fossils and slipping prevent a precise boundary from being traced through the modern Tidmoor exposures.
Weymouth Member
Bed TP7 — Lower Weymouth Member East Of Tidmoor Point
East of Tidmoor Point, beyond the classic ammonite-producing banks, younger Oxfordian beds of the Weymouth Member crop out on the foreshore but are commonly masked by seaweed and superficial mud. They are pale grey, smooth, blocky, calcareous mudstones, generally less organic-rich than the Peterborough Member and carrying the more typical Weymouth Member fauna of large oysters and pyritized cardioceratid ammonites. At Tidmoor Point itself these beds are not sufficiently exposed to justify a detailed numbered log, but they represent the incoming Lower Oxfordian mudstones above the famous Tidmoor Point Lamberti fauna and are probably equivalent to the basal Weymouth Member that is better exposed eastward in the Weymouth area.
Depositional Environment
The Tidmoor Point succession records offshore marine mud deposition on the south Dorset shelf during Callovian to early Oxfordian time, including the older western reference exposures rather than only the younger beds at the point. The Kellaways traces represent a somewhat sandier muddy shelf with shell beds and septaria; Peterborough Member deposition took place under relatively deeper, quieter and often dysoxic bottom waters that favoured preservation of organic-rich mud and crushed ammonites; Stewartby Member sedimentation brought paler, more calcareous blocky mudstones still deposited offshore but yielding abundant pyritized cephalopods; and the basal Weymouth Member marks the incoming Lower Oxfordian pale calcareous mudstone facies with large oysters and cardioceratid ammonites. Throughout the site, slumping, low relief and foreshore reworking mean that fossils are commonly recovered from derived mud lumps and nodule debris rather than from a single clean in-situ bed.
Total Thickness Note
No reliable total thickness can be measured at Tidmoor Point itself. The chart summarises the Oxford Clay members recorded at and immediately beside the point: Peterborough Member to the west, Stewartby Member in the point’s banks and Weymouth Member to the east. These are incomplete and partly slipped exposures. Kellaways records farther west towards East Fleet village and Butterstreet Cove provide wider context, rather than an additional unit in a measured Tidmoor log.
References
Arkell, W.J. (1947). Geology of the Country around Weymouth, Swanage, Corfe and Lulworth.
Cox, B.M. & Page, K.N. (2002). Shipmoor Point–Butterstreet Cove and Tidmoor Point–East Fleet Coast, Dorset, in British Middle Jurassic Stratigraphy, Geological Conservation Review Series 26.
Page, K.N. (2002). Crookhill Brickpit, Dorset, in British Middle Jurassic Stratigraphy, Geological Conservation Review Series 26.
Chapman, N.D. (1997). Ammonites from the Oxford Clay near Budmouth School and Tidmoor Point, Weymouth, and their bearing on the Callovian/Oxfordian boundary.
Callomon, J.H. & Cope, J.C.W. (1995) on the Callovian–Oxfordian boundary beds and Oxford Clay succession of the Weymouth district.
British Geological Survey Lexicon of Named Rock Units: Kellaways Formation, Kellaways Clay Member, Kellaways Sand Member, Oxford Clay Formation, Peterborough Member and Stewartby Member.
British Geological Survey Stratigraphical Framework Series: Oxford Clay Formation.
British Geological Survey Special Memoir: South Dorset and south-east Devon and its World Heritage Coast.
EQUIPMENT
A specimen bag or box will be useful. All fossils can be picked by hand, without the need for any equipment.
CLEANING AND TREATING
Keep fragile ammonites supported and remove only loose surface sediment with a very soft brush. Do not routinely soak the pyritic specimens or clay-rich matrix: a fixed 24-hour bath is not suitable for every fossil. Salt removal and the drying of unstable material need specimen-specific advice. Avoid radiators and other heat sources, and retain any detached pieces with the specimen.
Paraloid B-72 may be useful for selected fragile areas after testing, but it is not a general moisture seal or a cure for pyrite decay, and complete removal from porous fossils cannot be guaranteed. Keep pyritic finds in dry, stable storage, inspect them for cracking or powdery alteration, and seek conservation advice if deterioration begins. Record any adhesive or consolidant used.
Avoid cosmetic varnishes: they can obscure fine shell detail, complicate later preparation and affect scientific examination. Photograph and label the specimen before treatment, recording the collecting locality and any known matrix or bed information.
SAFETY
Tidmoor Cove lies southeast of the point. Do not attempt to cross to the cove across the mudflats. This is dangerously deep mud, which must be avoided. Check weather and water conditions before visiting: Fleet water levels can lag coastal tide predictions and are affected by weather and atmospheric pressure. Stay on open public paths.
IDENTIFY YOUR FINDS
Need help identifying a fossil? Share clear photos, where you found it and its size with the community.
FURTHER READING
Deposits Magazine – Book review: A Guide to Fossil Collecting on the South Dorset Coast
Geology of the Fleet Lagoon – Ian West’s field guide
Shipmoor Point–Butterstreet Cove and Tidmoor Point–East Fleet Coast – Geological Conservation Review
Fossils along the Fleet Lagoon – Alan Holiday
South Dorset and south-east Devon and its World Heritage Coast – BGS Special Memoir
ACCESS RIGHTS
Collectors continue to visit Tidmoor Point, but visitors should be aware of the reserve’s official guidance. It says that small-scale collection of loose fossils may be permitted in some places, while extraction from the soft cliffs and walking along the Fleet shores are not permitted. It does not identify Tidmoor Point as an exception, so check with the reserve about the intended shore access and loose collecting before visiting. The Fleet lagoon and shores up to mean high water belong to Ilchester Estates; see the access guidance. Always obey military-range closures and avoid the mudflats.
This site is an SSSI and forms part of the UNESCO World Heritage Jurassic Coast. In particular, hammering the bedrock is not permitted. For full information about the reasons for the status of the site and restrictions, download the PDF from Natural England.
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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