Overview
Directions
- Take the A351 into Swanage, heading towards the seafront. Continue along Shore Road, then turn into Institute Road, followed by Seymer Road, and finally onto Durlston Road.
- Park along Belle Vue Road (BH19 2HP), where roadside parking is available.
- From here, take the footpath signposted as the ‘Zig Zag Path’, located between the flats. This path descends steeply down to the foreshore.
- Once at the bottom, you can begin searching immediately. The main fossil-bearing beds are found by heading west towards Durlston Head, following the foreshore.
- Be aware that access along the foreshore involves crossing large boulders and uneven terrain, and conditions vary depending on tide and weather.
- Car Park Postcode: BH19 2HP, Google Maps Link
- What3Words collecting area: ///replayed.dine.overdone
Location photographs
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Video Film
Fossil Hunting
The middle-to-southern part of Durlston Bay exposes a faulted lower-Purbeck succession, including freshwater fossil beds, the oyster-rich Cinder Bed and older evaporitic limestones towards Durlston Head. Its importance is the variety of fossil-bearing horizons and their recorded positions. The classic mammal discoveries do not mean that mammal remains are routine beach finds, or that this entire stretch is more productive than the northern bay.
The Mammal Bed, DB83, is a dark, carbonaceous, shelly clay and shale in the freshwater part of the Lulworth Formation, below the Cinder Bed. Its record includes fish and reptile remains and rare early mammals such as Plagiaulax and Spalacotherium. Most mammal finds are minute teeth or jaw fragments requiring specialist recovery and identification; they should not be expected in every sample of dark shale.
Fish remains are abundant throughout this section, including teeth, vertebrae and scales from species such as Lepidotes, as well as hybodont sharks including Hybodus. Crocodile teeth and scutes are also regularly found, although usually fragmentary.
Freshwater gastropods, including Planorbis and Physa, and abundant ostracods help characterise the Mammal Bed matrix. Its uneven basal contact and shell-rich carbonaceous mud are more useful clues than colour alone. Other dark shale horizons occur in the bay, and loose beach material should be labelled as unprovenanced unless its source bed is securely known.
Towards Durlston Head, the lower Purbeck includes restricted-water limestones and evaporitic breccias rather than a uniform succession of richer vertebrate beds. The traditional Archaeoniscus Bed records the small isopod Archaeoniscus brodiei; the Broken Beds and Caps are especially valuable for their sedimentary and structural features. Keep these lower horizons distinct from the Mammal and Feather beds farther up the succession.
Microfossils are particularly important in this section. In addition to vertebrate remains, the sediments are rich in ostracods and foraminifera, and careful sampling can yield a wide range of material. However, proper recovery requires sieving and often microscope work.
Where collecting is permitted, take only small samples of loose shale from the firm, open foreshore for sieving at home, well clear of cliffs, fresh falls and slipped ground. Many fossils, especially bones, are extremely delicate and can easily be damaged if handled incorrectly in the field.
Fossil photographs
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Discoveries and milestones
Some of the most significant fossil discoveries and scientific milestones from the middle of Durlston Bay to Durlston Head include the classic early work on the Purbeck succession, the recognition of important fish-, turtle-, crocodile- and footprint-bearing beds, the later bed-by-bed revision of the bay, and notable vertebrate finds from the Middle Purbeck section.
19th century – the Durlston Head side of the bay became recognised as one of the finest Purbeck sections in Britain
The stretch from the middle of Durlston Bay to Durlston Head became important early in the history of Purbeck geology because it exposes a superb succession of Middle and Lower Purbeck beds. This helped establish the southern half of the bay as a classic reference section for the transition from lagoonal limestones and shales down into the evaporitic and brecciated lower beds near Durlston Head.
1898 – Strahan sketched the succession in the southern part of Durlston Bay towards Durlston Head
One of the key early milestones for the southern half of the bay was Strahan’s published cliff profile of the section from the Zigzag path southwards. This became an important early guide to the stratigraphy of the middle bay to Durlston Head stretch.
1915–1919 – A. Smith Woodward showed that the Middle Purbeck beds of Durlston Bay were exceptionally important for fossil fishes
Woodward’s work demonstrated that some of the best fish specimens from Durlston Bay come from the Intermarine Member or Upper Building Stones of the Middle Purbeck succession. This helped establish the bay as one of the most important Late Jurassic–earliest Cretaceous fish localities in Britain.
1969 – Torrens brought renewed attention to the Durlston Bay bed succession
Twentieth-century work revived detailed interest in the numbered bed succession of Durlston Bay, helping tie the historic fossils to a more precise modern framework. This was an important step towards the later detailed DB bed-number system used through the bay.
1985 – West and El-Shahat documented dinosaur footprints from the Corbula Beds
The middle to southern part of Durlston Bay became especially important for trace fossils when dinosaur footprints were recorded from the Corbula Member. This confirmed that the bay preserves not only bones, teeth and shells, but also direct evidence of dinosaur activity on the Purbeck lagoon margins.
1987–1988 – Ensom described mammal, fish and microvertebrate material from the Cherty Freshwater Member
Important work in the late 1980s showed that Bed DB102 in the Cherty Freshwater Member had yielded a diverse microvertebrate assemblage, including fish, amphibians, reptiles and mammals. This added major significance to the middle part of the bay, showing that small vertebrate remains were concentrated at specific horizons and not just scattered randomly through the succession.
1991 – Nunn published a detailed geological map of the Purbeck beds in Durlston Bay
Nunn’s mapping was one of the most important modern milestones for the bay because it gave a detailed geological survey of the Purbeck Beds and helped clarify the bed relationships through the central part of the section. This became especially useful for understanding the middle bay succession southwards toward the major faults and Durlston Head.
1991 – Ensom and colleagues described diverse reptile faunas from the bay
Later work on the Durlston reptile fauna helped confirm the site as one of Britain’s richest earliest Cretaceous reptile localities. The middle and southern beds are especially important for turtles, crocodilians and small reptiles.
1993 – Clements published the bed-by-bed reappraisal of the Durlston Bay succession
Clements’ 1993 reappraisal of the stratigraphy provided the standard modern numbered DB bed framework for Durlston Bay. This was one of the most important scientific milestones for the site because it allowed fossils from the middle of the bay to Durlston Head to be placed much more accurately within the succession.
Modern era – Richard Edmonds discovered a fine crocodile skull at the base of the Shed Bed and the junction with the Shingle
One of the most notable later vertebrate finds from the middle bay section was a fine crocodile skull discovered by Richard Edmonds at the base of the Shed Bed and the junction with the Shingle. This is one of the clearer named vertebrate discoveries tied to the central Durlston Bay succession.
Modern understanding – the middle bay to Durlston Head stretch remains one of the key Purbeck reference sections in Britain
Today this part of Durlston Bay is recognised as especially important for the Purbeck bed succession, dinosaur footprints, fish-bearing limestones, turtle and crocodile horizons, and the structurally complex lower beds near Durlston Head. Its importance lies not only in individual fossils, but in the way the fossil horizons can be tied into a detailed bed-by-bed stratigraphic framework.
Geology
From the middle of Durlston Bay southwards to Durlston Head, the geology becomes more complete and significantly more complex, exposing one of the finest sections of the Purbeck Limestone Group in Britain. This area represents the type locality for the group, making it of exceptional scientific importance.
The sequence here spans the boundary between the Late Jurassic and earliest Cretaceous, recording a series of lagoonal, freshwater and occasional marine incursions. The rocks belong to both the Durlston Formation (upper) and the underlying Lulworth Formation, allowing the full transition to be observed.
In this middle-to-southern bay subsection, the Durlston Formation is represented by the basal Stair Hole Member, especially the Cinder Bed, and a small fault-repeated slice of lower building-stone beds. The younger Corbula and Chief Beef successions belong to the northern bay and are described with Peveril Point. The repeated central spur makes this a composite section rather than an uninterrupted downward traverse.
At the base of the Durlston Formation lies the Cinder Bed, a distinctive oyster-rich horizon formed during a marine incursion. This bed is packed with bivalves such as Praeexogyra distorta, Protocardia major and Nanogyra bulla, along with echinoid remains including Hemicidaris purbeckensis.
Beneath this, the Lulworth Formation is exposed, particularly within the central part of the bay. These beds represent predominantly freshwater lagoonal environments and include the Marly Freshwater Beds, which contain abundant molluscs and microfossils. Within this sequence lies the famous Mammal Bed, a dark, organic-rich horizon that has yielded rare early mammals such as Plagiaulax and Spalacotherium, along with crocodiles, turtles and plant material.
Important lower units include the Cherty Freshwater Beds within the Worbarrow Tout Member, the Mammal Bed and evaporite-rich Cockle beds. The Cypris Freestones and the basal Caps and Broken Beds record restricted carbonate lagoons and evaporitic environments. Jurassic–Cretaceous boundary correlations in the lower Purbeck remain scheme-dependent and should not be tied to a single obvious Cypris Freestone marker.
Towards Durlston Head, the sequence becomes increasingly dominated by harder limestones and complex bedding, reflecting continued environmental fluctuations. The beds dip and fold across the bay, bringing different horizons down to foreshore level and allowing them to be studied in detail.
Detailed geology and bed-by-bed succession
This is a detailed composite breakdown of the middle-to-southern Durlston Bay section, from the faulted central bay around the Cinder Bed south to the evaporite-rich basal Purbeck and Purbeck–Portland junction at Durlston Head. It is one of the key reference sections for the lower Purbeck succession, important for the Cinder Bed, Mammal Bed and Feather Bed vertebrate horizons, the gypsum-rich Soft Cockle facies, and the structurally thickened Broken Beds at the headland.
PURBECK GROUP
Only the middle of Durlston Bay southward to Durlston Head is treated here. That means the page focuses on the basal Durlston Formation in the central bay and then the much thicker Lulworth Formation reference section southward to the headland. The younger Peveril Point Member and the main northern Upper Purbeck section nearer Peveril Point are deliberately excluded.
Durlston Formation (Lower Cretaceous, Berriasian)
Within the middle-bay-to-head subsection, the Durlston Formation is represented only by the basal Stair Hole Member and by a small fault-repeated slice of the lower building-stone succession in the central spur. The full Stair Hole Member is much thicker farther north in Durlston Bay, but only its base and a structurally repeated part of its lower shell-beach facies belong to the area covered here.
Stair Hole Member
The expanded DB descriptions below retain Clements’ measured type-section detail as a named-bed reference. His principal traverse lay between Peveril Point and the Zigzag Path, overlapping the central-bay markers; these measurements are not a new continuous log along the southern headland. Southern exposures are correlated by their characteristic beds, with local observations separately identified. Historical exposure gaps, approximate measurements and combined sub-bed totals remain explicit. The chart is an overview of a faulted composite and does not replace these individual descriptions.
Bed DT1 — Cinder Bed (formal DB111; c. 2.95 m)
The Cinder Bed is the key marker at the top of the section covered here and forms the formal base of the Durlston Formation. It is a bluish-grey, massive, oyster-rich shelly limestone and calcareous mudstone, crowded with Praeexogyra distorta and accompanied by Serpula coacervata, the echinoid Hemicidaris purbeckensis and rarer larger bivalves such as “Protocardia” major. In the field it forms the obvious ledge at the centre of Durlston Bay and is repeated again south of the Zigzag Path by faulting. It records a short but important marine incursion across the otherwise mainly lagoonal and freshwater Purbeck succession and is one of the most laterally persistent marker horizons in the whole group.
DB111c (0.51 m; Clements type-section reference)
The upper Cinder subdivision is clay-rich calcareous mudstone and micrite with abundant oyster debris.
DB111b (0.97 m; Clements type-section reference)
The middle Cinder subdivision is the oyster-rich calcareous shale and mudstone portion of the marine-incursion package.
DB111a (1.47 m; Clements type-section reference)
The lower Cinder subdivision is massive oyster-rich limestone. The three source subdivisions together total 2.95 m.
Bed DT2 — Fault-Repeated Lower Stair Hole Building-Stone Slice (includes formal Bed DB118 locally)
Between the two central bay faults, a limestone spur preserves a local repeated slice of the lower Stair Hole Member above the Cinder Bed. These beds belong to the traditional lower Intermarine or Upper Building Stone facies: shell-rich biosparites, biomicrites and mudstones deposited in low-salinity lagoon-margin shell-beach and shallow-water settings rather than in fully marine open shelf conditions. The most important local horizon is DB118, which preserves an in situ dinosaur footprint in the central bay. This repeated spur is structurally important because it proves that the central bay is not a single uninterrupted downward section from the Cinder to Durlston Head, but a faulted composite in which part of the lower Stair Hole Member is reintroduced above the older lower Purbeck beds.
Lulworth Formation (Latest Jurassic To Earliest Cretaceous, Tithonian–Berriasian)
The middle of Durlston Bay to Durlston Head is one of the primary reference sections for the Lulworth Formation. Here the succession descends from the top of the Worbarrow Tout Member through the difficult-to-separate Ridgeway interval into the Mupe Member at the headland. The lower Purbeck succession spans latest Tithonian into Berriasian time. Published correlations place the Jurassic–Cretaceous boundary within its lower part, but no single visible Cypris Freestone bed should be presented as an uncontested chronostratigraphic boundary.
Worbarrow Tout Member
Bed DT3 — Upper Cherty Freshwater Beds (formal beds DB87–110; uppermost Worbarrow Tout Member)
The top of the Lulworth Formation at Durlston Bay consists of thicker-bedded, chert-rich freshwater micrites with interbedded mudstones and shales. Chert remains visible as low as DB87, and the member as a whole carries freshwater gastropods, ostracods and charophytes rather than the more saline faunas of the lower lower-Purbeck units. These beds represent shallow, carbonate-rich low-salinity lakes and ponded marginal-waterbody deposits developed immediately below the marine Cinder Bed transgression. At Durlston they form the cliff-foot limestones directly beneath the Cinder and are among the most important vertebrate-bearing horizons in the lower half of the bay.
DB101 (1.40 m; Clements type-section reference)
Rough-bedded massive freshwater limestone contains chert, Hydrobia and Viviparus, as described in the type-section log.
DB100 (0.057 m; Clements type-section reference)
A thin gypsum-rich shale separates DB101 from the underlying limestone.
DB99 (0.057 m; Clements type-section reference)
Iron-stained muddy shell limestone contains abundant charophyte remains and well-preserved bivalves.
DB98 (0.09–0.20 m; Clements type-section reference)
Dark shale is locally replaced by thicker blocky muddy-limestone lenses filling irregularities in the underlying bed.
DB97 (0.84 m; Clements type-section reference)
The Flint Bed comprises hard pale biomicrite beds separated by softer muddy seams that become more prominent downwards. Irregular chert nodules and abundant selectively silicified gastropods and ostracods are diagnostic; charophytes and sponge spicules also occur. It forms a conspicuous Cherty Freshwater marker.
DB96 (0.61 m; Clements type-section reference)
Firm shale alternates with bivalve biosparite and cream micrite, with distinct ostracod-rich and white-shell-rich horizons.
DB95 (0.28 m; Clements type-section reference)
Hard brittle fossiliferous micrite contains abundant ostracods and scattered gastropods, with little obvious bedding lamination.
DB94 (0.025 m; Clements type-section reference)
A thin rough bivalve limestone grades into muddy biomicrite above and below. Footprints occur on its base.
DB93 (0.38 m; Clements type-section reference)
Grey-green calcareous clay contains decayed pale shells and many poorly preserved ostracods.
DB92 (0.25 m; Clements type-section reference)
Dark shale contains pale-blue fibrous celestite resembling calcite beef, together with altered pyrite, ostracods and molluscan fragments.
DB91 (0.05–0.08 m; Clements type-section reference)
A shaly shell band contains decayed bivalves and dark ostracods; some bivalve shells are silicified.
DB90 (0.56 m; Clements type-section reference)
Laminated calcareous clay is gritty with fine shell fragments, including decayed pale shells and darker shaly seams.
DB89 (0.46 m; Clements type-section reference)
Firm to hard pale calcareous clay and argillaceous micrite include biomicritic patches and fine shell debris.
DB88 (0.38 m; Clements type-section reference)
Soft ostracod-rich calcareous shale includes thin, partly silicified ostracod limestones.
DB87 (0.19–0.23 m; Clements type-section reference)
Hard shell biosparite contains micrite intraclasts, chert nodules, ostracods, bivalves and scattered gastropods.
Bed DT4 — Feather Bed And Associated Cherty Freshwater Vertebrate Horizons (formal beds DB102–108 in part)
The upper Cherty Freshwater succession contains several especially important vertebrate and footprint horizons. Vertebrate-bearing horizons are documented in this interval, but the rich assemblages from inland quarries at correlated levels must be kept separate from demonstrably coastal finds. DB102 here is the local shale horizon described individually below. The Under Feather level (DB106) yielded material named as Iguanodon hoggi in the older literature, while the Feather Bed itself (DB108) produced postcranial remains referred to Nuthetes, granicones and numerous small crocodilian remains including forms historically called Nannosuchus and Theriosuchus. Local footprint surfaces are recorded at the DB93/94 and DB102/103 interfaces. Lithologically these beds are a mix of cherty limestones, carbonaceous shales and freshwater micrites laid down in shallow lake and marginal-mudflat settings where episodic drying and flooding repeatedly created surfaces capable of preserving tracks and concentrating small vertebrate debris.
DB110 (0.41 m; Clements type-section reference)
Calcareous shale contains abundant poorly preserved ostracods and thin ostracod-rich limestone bands immediately below the Cinder Bed.
DB109 (0.038 m; Clements type-section reference)
A thin shale parting separates DB110 from the Feather Bed.
DB108 (0.61 m; Clements type-section reference)
The Feather Bed is pale bivalve biosparite with coarsely fragmented shells and scattered whole bivalves, with subordinate fine shelly biomicrite. Ostracods are common, and Clements records Thalassinoides burrows on the bases of bedding planes.
DB107 (0.14 m; Clements type-section reference)
Laminated cream micrite becomes softer and more argillaceous at its base, with thin ostracod-rich seams.
DB106 (0.08 m; Clements type-section reference)
Thin rough biosparites, biomicrites and micrites contain sand-sized bivalve and ostracod debris: the Under Feather interval.
DB105 (0.24 m; Clements type-section reference)
Evenly laminated grey calcareous mudstone contains fine carbonate fragments and ostracods.
DB104 (0.19 m; Clements type-section reference)
Calcareous clay contains abundant crushed ostracods and scattered decayed white bivalve fragments.
DB103 (0.25 m; Clements type-section reference)
Massive hard grey biomicrite contains lesser biosparite and lens-like chert, with weak lamination.
DB102 (c. 0.46 m; Clements type-section reference)
Grey shale contains decayed bivalve and gastropod shells, partly decalcified ostracods, common charophyte remains, bones and coprolites in Clements’ coastal reference log. Thin sandy ostracod shell limestones at the base contain bivalves and shale wisps and grade into ostracod shale. The local footprint interface is DB102/103; rich inland microvertebrate assemblages at equivalent levels remain separately sourced.
Bed DT5 — Marly Freshwater Beds And Mammal Bed (formal Bed DB83 in part)
Below the cherty unit lies the Marly Freshwater interval, an argillaceous freshwater-lake succession rich in Hydrobia, Viviparus, Planorbis, Physa and charophytes. Its most famous bed is the Mammal Bed, DB83, a dark grey, shelly, carbonaceous calcareous clay and shale resting on an irregular surface and in part grading into the bed below. Despite its old quarry name as a “Dirt Bed”, it is not a rooted palaeosol like the Great Dirt Bed of the basal Purbeck; instead it is a carbonaceous freshwater lake-margin or swamp deposit with abundant freshwater shells and accumulated vertebrate debris. This horizon yielded the classic Beckles mammal assemblage, historically recorded as around 14 genera and 18 species of early mammals, together with lizards, crocodilians, dinosaur remains including Echinodon and the type jaw of Nuthetes, fish, plants and invertebrates. It is one of the most important microvertebrate beds in the British Early Cretaceous.
DB86 (0.25 m; Clements type-section reference)
Laminated calcareous clay and argillaceous micrite contain decayed white shells and thin ostracod-rich concentrations.
DB85b (0.94 m; Clements type-section reference)
Laminated calcareous clay grades down into harder muddy micrite; gastropods are very common and ostracods also occur.
DB85a (0.08 m; Clements type-section reference)
Ostracod-rich micrite contains well-preserved bivalves, gastropods, pellets and micrite nodules.
DB84 (0.11 m; Clements type-section reference)
Laminated argillaceous micrite contains plentiful ostracods and white bivalve and gastropod fragments.
DB83 (0.14–0.48 m; Clements type-section reference)
The Mammal Bed is carbonaceous shelly calcareous clay and shale with an irregular, locally transitional base; freshwater gastropods and other remains are abundant.
DB82b (0.30 m; Clements type-section reference)
Hard fossiliferous micrite contains dark angular shale intraclasts, particularly near its top, and poorly preserved shelly remains.
DB82a (0.05 m; Clements type-section reference)
Hard bivalve limestone contains small irregular pellets and larger, flattened micritic intraclasts.
DB81 (0.91 m; Clements type-section reference)
Laminated pale muddy micrite and calcareous clay contain common ostracods and abundant gastropods.
DB80 (0.28 m; Clements type-section reference)
Massive-looking pale fossiliferous micrites alternate with softer, better-laminated muddy bands; gastropods occur in both facies.
DB79 (0.08 m; Clements type-section reference)
A thin laminated calcareous clay is especially rich in charophytes, gastropods and ostracods.
DB78 (0.43 m; Clements type-section reference)
Hard, slightly argillaceous micrite shows disturbed lamination picked out by ostracod-rich seams.
DB77b (0.10 m; Clements type-section reference)
Fine lamination characterises the upper soft cream-brown calcareous clay of the combined DB77 interval.
DB77a (0.05 m; Clements type-section reference)
The lower DB77 shale contains shell-rich bands and concentrated decayed bivalves; the combined DB77 thickness is 0.15 m.
DB76b (0.08 m; Clements type-section reference)
Hard pellet- and fossil-bearing limestone contains irregular micrite and chert intraclasts and eroded micritic seams.
DB76a (0.05 m; Clements type-section reference)
A softer pellet-rich limestone contains intraclasts and muddy micrite layers with disturbed bedding.
DB75b (0.025 m; Clements type-section reference)
Dark-brown shale forms the upper part of this two-part transition above the Soft Cockle Beds.
DB75a (0.075 m; Clements type-section reference)
Cream-grey laminated calcareous clay contains thin darker shale bands; DB75 totals 0.10 m.
Bed DT6 — Soft Cockle Beds (middle Worbarrow Tout Member)
The Soft Cockle Beds form a long evaporite-rich interval of softer marls, micrites and dolomitic beds with abundant evidence of primary and early diagenetic evaporites. The characteristic bivalve is Protocardia purbeckensis, and Serpula coacervata is common. Particularly important at Durlston are the secondary gypsum beds developed after burial anhydrite and ultimately after primary gypsum, commonly with nodular or chicken-wire textures. Cream-coloured dolomitic beds with halite pseudomorphs, some celestite and minor stromatolitic development also occur. These strata represent restricted saline to hypersaline lagoon and sabkha cycles under semi-arid seasonal conditions, and dissolution of the gypsum contributes significantly to the modern instability of the central and southern Durlston cliffs.
DB74 (0.23 m; Clements type-section reference)
Hard fossiliferous micrite is mottled and has strongly disturbed lamination, with gastropods and ostracods.
DB73 (0.30 m; Clements type-section reference)
Mottled argillaceous micrite and calcareous clay are blocky to weakly laminated and contain ostracods.
DB72b (0.25 m; Clements type-section reference)
Very hard massive micrite preserves only faint disturbed lamination and a small sampled fauna.
DB72a (0.28 m; Clements type-section reference)
Mottled argillaceous micrite is blocky, breaking into rounded lumps, with a diverse sampled ostracod assemblage.
DB71 (0.61 m; Clements type-section reference)
Massive pale bluish-grey marl contains cream mottling and scattered harder bands, with gastropods and ostracods.
DB70b (0.25 m; Clements type-section reference)
Calcareous clay and muddy micrite contain harder pale limestone bands, especially near the base, separated by ostracod-rich clay.
DB70a (c. 0.36 m; Clements type-section reference)
Massive pale micrite has early brecciation, small mineral-lined cavities and an intraclast-bearing surface.
DB69 (0.61 m; estimated; Clements type-section reference)
Clements’ 1963 observation records harder marl passing down into softer marl; the bed was not exposed during his 1964 visit.
DB68 (0.56 m; seen in 1963; Clements type-section reference)
Hard massive micrite contains abundant empty hopper-shaped salt-crystal moulds, some partly mineralised; later exposure was less complete.
DB67 (0.66 m; Clements type-section reference)
The historical description records hard fawn marl with grey shale–marl passing down into shalier material; it was not exposed in 1964.
DB66 (0.91 m; Clements type-section reference)
Very hard pale micrite contains large hopper-halite moulds with growth laminae, decreasing in size towards the base.
DB65 (c. 0.61 m; Clements type-section reference)
Banded micrite and muddy micrite contain well-developed lamination, including pellet-rich seams.
DB64 (c. 0.61 m; Clements type-section reference)
Hard thin micrite beds contain small to medium empty halite moulds and disturbed, poorly developed lamination.
DB63 (0.46 m; Clements type-section reference)
Calcareous shale contains selenite and gypsum sand, with a sparse gastropod and ostracod assemblage.
DB62 (0.36 m; Clements type-section reference)
Laminated calcareous mudstone and argillaceous micrite contain pale fossil-rich seams.
DB61 (0.36 m; Clements type-section reference)
Calcareous clay alternates with thin limestones, which become dominant towards the base.
DB60 (1.07 m; Clements type-section reference)
Laminated calcareous ostracod shale contains decayed white bivalve seams and thin pellet limestones near its base.
DB59 (0.56 m; Clements type-section reference)
Hard massive pale micrite contains common empty salt-crystal moulds, some partly filled by later minerals.
DB58c (0.20 m; Clements type-section reference)
Well-laminated argillaceous micrite and calcareous clay contain poorly preserved ostracods.
DB58b (0.032 m; Clements type-section reference)
A thin hard pellet-rich limestone contains micrite flakes and fragments of algal material, with crystal-lined cavities.
DB58a (0.97 m; Clements type-section reference)
Laminated calcareous clay and muddy micrite contain thin, harder, pellet-rich limestone bands.
DB57 (c. 0.30 m; Clements type-section reference)
Hard pellet limestones alternate with softer calcareous clay and preserve halite pseudomorphs on upper surfaces.
DB56c (0.46 m; Clements type-section reference)
Irregular thin pellet-rich limestones contain fossils and are separated by muddy seams.
DB56b (0.18 m; Clements type-section reference)
Soft marl includes harder marl bands and abundant gypsum sand.
DB56a (up to 0.10 m; Clements type-section reference)
Dark laminated calcareous clay has pale bleached bands and an intervening gypsum-rich marl seam.
DB55e (0.012–0.025 m; Clements type-section reference)
A thin shell-rich limestone grades into pellet limestone, with abundant serpulids and gastropods.
DB55d (0.25 m; Clements type-section reference)
Hard pale micrite is almost structureless and breaks with a flint-like fracture; very fine pellets occur.
DB55c (0.23 m; Clements type-section reference)
Soft gypsum sand forms a distinct evaporitic layer.
DB55b (0.20 m; Clements type-section reference)
Soft laminated calcareous clay and muddy micrite contain harder seams beneath a thin micrite cap.
DB55a (0.23 m; Clements type-section reference)
Hard laminated micrite contains pale seams marked by moulds of lenticular gypsum crystals.
DB54b (0.23 m; Clements type-section reference)
Dark calcareous shale contains secondary selenite and lens-like chert nodules formed from silicified gypsum crystals.
DB54a (0.15 m; Clements type-section reference)
Soft muddy micrite and calcareous clay contain silicified gypsum sand and small chert lenses; thickness varies at the expense of DB54b.
DB53 (0.36 m; Clements type-section reference)
Pale micrite bands alternate with darker, softer muddy material; large secondary selenite crystals occur and the bed grades into DB52.
DB52 (0.10 m; Clements type-section reference)
Laminated calcareous clay contains micrite and pellet-limestone seams, some with moulds of lenticular gypsum; ostracods and other fossils occur.
DB51d (0.23 m; Clements type-section reference)
Thin discontinuous shelly and pellet limestones have softer muddy partings; bivalves and gastropods are abundant in the combined DB51d/b samples.
DB51c (0.025 m; Clements type-section reference)
A laminated calcareous-clay seam separates the two upper DB51 limestone intervals and contains plentiful ostracods.
DB51b (0.20 m; Clements type-section reference)
The lower of those two shelly limestone intervals is rich in bivalves, gastropods and pellets; some shell material is selectively silicified.
DB51a (c. 0.61 m; Clements type-section reference)
Thin muddy limestones grade down into laminated calcareous clay with harder cross-bedded pellet-rich seams, separated from DB51b by brown shale.
DB50b (0.15–0.23 m; Clements type-section reference)
Laminated calcareous clay contains harder seams and abundant silicified lenticular gypsum crystals, with occasional chert.
DB50a (c. 0.10 m; Clements type-section reference)
A firm sandy-looking marl was logged, with the sand tentatively interpreted as gypsum.
DB49 (0.46 m; Clements type-section reference)
Massive hard micrite contains thin bivalve-rich bands and abundant serpulids; Clements noted difficulty establishing a complete local section here.
DB48 (c. 0.76 m; Clements type-section reference)
Calcareous clay and muddy micrite contain gypsum-sand layers, harder limestone laminae and moulds of gypsum and halite.
DB47d (0.13 m; Clements type-section reference)
Hard laminated micrite contains calcitic seams up to 0.018 m thick with moulds of lenticular gypsum crystals. In places the micrite is replaced by sugary-looking marl with crystal pseudomorphs.
DB47c (0.25 m; Clements type-section reference)
Blocky calcareous clay and argillaceous micrite show poor lamination and contain ostracods.
DB47b–a (0.10–0.23 combined m; Clements type-section reference)
Laminated calcareous clay of DB47a is locally replaced by harder micrite of DB47b, with calcitic seams and small halite pseudomorphs.
DB46 (0.25 m; Clements type-section reference)
Soft laminated calcareous clay contains selenite and silicified lenticular gypsum crystals.
DB45 (c. 0.61 m; Clements type-section reference)
Hard and softer blocky micrite–clay bands contain laminated calcareous-clay seams and moulds of small gypsum crystals.
DB44 (0.61 m; estimated; Clements type-section reference)
Grey shaly marl was recorded in the historical field log above the main gypsum-rich interval.
DB43 (c. 5.49 m; Clements type-section reference)
Laminated calcareous clay contains large gypsum masses, chiefly in its lower two-thirds, and much selenite. A yellow marl band estimated at 0.025 m occurs at the top, with gypsum sand at the base; deformation and dissolution complicate the whole-bed thickness.
DB43 upper Yellow Band (estimated 0.025 m)
This thin yellow marl forms the top of DB43 in Clements’ reference log. Its estimated 25 mm thickness is included within the approximately 5.49 m whole-bed figure.
Bed DT7 — Hard Cockle Beds (basal Worbarrow Tout Member at Durlston)
In western Dorset the Hard Cockle Beds are sandy bivalve limestones, but at Durlston Bay they pass into a more basinal facies of marls and marlstones. Protocardia purbeckensis remains common, evaporite pseudomorphs are present, and insect horizons are known, including fossil wasps at DB36c. Restricted saline lagoonal conditions and evaporite development dominate the environmental interpretation. However, Clements recorded gastropods and varied ostracod assemblages in individual Hard Cockle beds, so an absolute claim that freshwater-associated fossils are absent would overstate the evidence. The change from the more obvious bivalve-rich limestones farther west into marly basinal facies at Durlston is one of the important eastward facies changes within the Purbeck Group.
DB42 (0.46 m; Clements type-section reference)
Laminated calcareous clay contains many decayed white bivalves and seams packed with Hydrobia.
DB41 (0.30 m; Clements type-section reference)
Poorly laminated blocky calcareous clay contains scattered decayed bivalves and abundant sampled Valvata and Hydrobia.
DB40 (0.51 m; Clements type-section reference)
Argillaceous micrite has variable lamination, abundant ostracods and decayed bivalves, with occasional gypsum-nodule moulds.
DB39 (0.61–0.76 m; Clements type-section reference)
Laminated calcareous clay and muddy micrite grade down into shale and contain layers packed with decayed white bivalves.
DB38b (0–0.33 m; Clements type-section reference)
A laterally variable hard mottled micrite is blocky and poorly laminated, with poorly preserved shell debris.
DB38a (0.08–0.28 m; Clements type-section reference)
Massive mottled micrite contains numerous calcite-lined rounded cavities left by gypsum nodules.
DB37 (0.10 m; Clements type-section reference)
Laminated calcareous clay contains fine sand-, silt- and pellet-rich seams and gypsum sand.
DB36c (0.46 m; Clements type-section reference)
Hard micrite has sandstone and sandy pellet-rich laminae and locally replaced gypsum features; the historical Hard Cockle insect record includes this bed.
DB36b (0.025 m; Clements type-section reference)
A thin soft laminated calcareous clay contains sandstone seams, gastropods and ostracods.
DB36a (0.18 m; Clements type-section reference)
Hard rough micrite, pellet limestone and biomicrite are partly fractured; shell-rich material fills some cavities. Clements records Archaeoniscus in DB36a, separately from the traditional Archaeoniscus Bed near the headland. Irregular algal structures, calcite-lined cavities left by former gypsum nodules and some silicification also occur.
DB35 (0.48 m; Clements type-section reference)
Laminated calcareous clay contains ostracods and poorly preserved bivalves concentrated in seams.
DB34 (0.30 m; Clements type-section reference)
Hard massive pale micrite has a fractured appearance and scattered poorly preserved bivalves.
Ridgeway Member
Bed DT8 — Ridgeway Transition Interval (poorly distinguished at Durlston Bay)
The Ridgeway Member is difficult to define at Durlston because the mudstone-rich facies seen farther west pass eastward into monotonous micritic limestone little different from parts of the Mupe Member below and the Worbarrow Tout Member above. Where present it represents a quieter, darker, more carbonaceous muddy phase between the thick ostracod-rich limestones of the Mupe Member and the more quartz-detrital lower Worbarrow Tout beds. In the field around middle Durlston Bay this transition is largely masked by facies change, weathering and structural disruption, so it is best treated as an indistinct but real stratigraphical interval rather than forced into an artificial sharp boundary.
Lulworth Formation — Cypris Freestones, member boundary uncertain
Bed DT9 — Cypris Freestones And Archaeoniscus Bed (includes formal DB11; Archaeoniscus Bed c. 1.3 m)
Above the basal evaporitic succession at Durlston Head are ripple-laminated ostracodal and pelletoidal limestones traditionally known as the Cypris Freestones. The modern Mupe–Ridgeway boundary is difficult to fix here; the traditional package is therefore retained without assigning every numbered DB bed to a sharply defined modern member. They formed in shallow carbonate flats and lagoons with salinities commonly around twice that of normal seawater, and desiccation of the lagoon floor left halite crystals that were later dissolved to produce casts in the fine carbonate sediment. A conspicuous marlstone, the Archaeoniscus Bed (DB11), lies above the Broken Beds and is easily seen at Durlston Head; it contains the isopod Archaeoniscus brodiei. Dragonfly larvae are rare. The whole interval is a distinctive restricted-lagoon carbonate facies with seasonal drying and repeated reworking of ostracod-rich sediment.
Clements’ Figure 4 reproduces West’s 1960 measured headland scheme. Its C.F., B.B., C. and P.S. labels below are historical source labels, distinct from the northern DB bed numbers and from modern member ranks. Clements expressly warns that West’s 1960 and 1975 logs use different numbering and are difficult to correlate in detail; no forced one-to-one equivalence is imposed.
Headland C.F.1 — conspicuous basal Cypris limestone (about 1.2 m in the historical description)
A prominent impure laminated limestone marks the basal Cypris Freestone unit in West’s 1960 headland scheme. Clements’ accompanying text gives four feet, approximately 1.2 m; this is a quoted local measurement, not one read from the figure scale or added to the northern DB10–11 log.
Headland C.F.2 — overlying Cypris shales
Shales overlie C.F.1 in the headland log. No independent numerical thickness is assigned here.
DB10–33 below retain the historical Cypris Freestone reference succession. Their placement here is a correlation aid and does not resolve the local Mupe–Ridgeway boundary. In particular, the headland Archaeoniscus Bed estimate above and Clements’ three-part DB11 measurement belong to different observations and must not be added together.
DB33 (0.25 m; Clements type-section reference)
Laminated grey calcareous clay contains abundant poorly preserved ostracods and some selenite.
DB32 (0.11 m; Clements type-section reference)
Hard blocky pale micrite contains thin silty seams and a sparse sampled fauna.
DB31c (0.56 m; Clements type-section reference)
Evenly laminated micrite becomes more massive upwards and contains abundant carbonaceous fragments and selenite-coated fractures.
DB31b (0.025 m; Clements type-section reference)
A distinctive thin intraclast bed contains closely packed micrite and algal flakes with loose micritic cement and iron-stained fractures.
DB31a (0.30 m; Clements type-section reference)
Broken laminated calcareous clay contains quartz grains, selenite and gypsum pseudomorphs.
DB30 (c. 0.61 m; Clements type-section reference)
Hard blocky micrite contains better-laminated portions marked by fine sandstone seams.
DB29 (c. 0.61 m; Clements type-section reference)
Calcareous clay and muddy micrite contain numerous fine sandstone laminae, some preserving halite pseudomorphs.
DB28 (0.51 m; Clements type-section reference)
Thin hard micrite bands alternate with softer, more argillaceous laminated partings.
DB27 (0.25 m; Clements type-section reference)
Blue-grey laminated calcareous clay contains selenite and thin pale silty seams.
DB26 (0.25 m; Clements type-section reference)
Hard blocky micrite contains laminae rich in pellets, plant fragments and fine detrital grains.
DB25 (0.61 m; Clements type-section reference)
Laminated calcareous clay contains silty, sandy, pellet-rich and plant-bearing seams, with much selenite.
DB24 (0.23 m; Clements type-section reference)
Hard massive micrite preserves lamination defined by silty and pellet-rich layers.
DB23 (0.13 m; Clements type-section reference)
Laminated calcareous clay to muddy micrite contains many thin sandstone laminae and selenite.
DB22 (0.13 m; Clements type-section reference)
Hard compact micrite contains sparse silty, pellet-rich and plant-rich seams, with mineral-lined cavities.
DB21 (0.08 m; Clements type-section reference)
Soft grey calcareous clay is weakly laminated and contains abundant selenite, apparently concentrated in layers.
DB20 (0.10 m; Clements type-section reference)
Hard massive micrite contains calcite- and selenite-lined cavities after gypsum nodules.
DB19c (0.18 m; Clements type-section reference)
Broken soft calcareous clay contains abundant selenite and larger gypsum-related features.
DB19b (0.23 m; Clements type-section reference)
Calcareous clay and muddy micrite include grey shale seams and harder fractured limestone bands.
DB19a (0.025 m; Clements type-section reference)
A thin harder marl band forms the lowest DB19 subdivision.
DB18 (0.91 m; Clements type-section reference)
Laminated micrite contains numerous poor bivalve casts and grades down into ostracod-rich calcareous shale.
DB17 (c. 2.44 m; Clements type-section reference)
Hard micrite bands alternate with softer laminated muddy layers; the upper part is comparatively massive and the lower part more finely divided.
DB16b (0.08 m; Clements type-section reference)
Clay-to-micrite facies has a broken appearance and thin sandstone laminae with halite pseudomorphs.
DB16a (0.46 m; Clements type-section reference)
Blocky calcareous clay and muddy micrite contain thin sandstone seams defining their poorly developed lamination.
DB15f (0.13 m; Clements type-section reference)
Soft buff-brown blocky marl weathers yellow and grades into the underlying shalier marl.
DB15e (0.28 m; Clements type-section reference)
Soft dark-grey to brown shaly marl forms the next DB15 subdivision.
DB15d (0.08 m; Clements type-section reference)
Light-grey blocky marl separates the two darker shaly intervals.
DB15c (0.10 m; Clements type-section reference)
Dark-grey to brown shaly marl overlies the harder lower DB15 limestone.
DB15b (0.25 m; Clements type-section reference)
Hard blocky cream micrite contains abundant detrital and pellet-rich laminae.
DB15a (0.30 m; Clements type-section reference)
Soft laminated calcareous clay contains thin harder limestone and sandstone-rich bands.
DB14 (0.51 m; Clements type-section reference)
Thin hard limestones alternate with muddy micrite partings; shell fragments, quartz grains and gastropod-rich laminae occur.
DB13b (0.28 m; Clements type-section reference)
A hard grey-brown shaly marl forms the upper DB13 subdivision.
DB13a (0.18 m; Clements type-section reference)
Blocky to laminated muddy micrite and calcareous clay contain poorly preserved ostracod-rich seams.
DB12 (c. 0.69 m; Clements type-section reference)
Laminated argillaceous micrite contains thin ripple-bedded calcarenite and calcareous-sandstone bands.
DB11c (0.15 m; Clements type-section reference)
Thin, well-laminated ostracod limestone caps DB11 in Clements’ northern reference section.
DB11b (0.05 m; Clements type-section reference)
A thin shale parting separates the two DB11 limestone subdivisions.
DB11a (1.37 m; Clements type-section reference)
Hard, thin, ripple-bedded biomicrites and fossiliferous pellet limestones form the main DB11 interval; the headland’s traditional Archaeoniscus Bed description is a separately scoped observation.
DB10 (2.13 m; Clements type-section reference)
Ripple-bedded ostracod biomicrites and micrites resemble DB11; brecciation and local structural disturbance complicate their basal relationship.
Mupe Member
Bed DT10 — Broken Beds (major evaporitic breccia interval)
The Broken Beds are among the most distinctive strata in the whole Durlston Bay subsection. At Durlston Head they comprise partly calcitized evaporites and evaporitic breccias, commonly very porous, with celestite residues and associated brittle-fracture structures. In the central bay their exposure has been partly obscured by sea-defence works, but at the headland they are well shown just north of the major fault against the Portland Stone. A major structural downbulge thickens the Broken Beds here and shows them to have been squeezed and displaced northward in association with extensional movement. This is an evaporite-rich interval strongly modified by faulting, collapse and plastic flow of former anhydrite or gypsum. West’s petrographic work indicates deformation before calcitisation, but the age of the faulting is not established; an exclusively very early tectonic origin is not demonstrated.
The original headland graphic distinguishes the disturbed interval from the underlying numbered Caps beds. This is an exact southern exposure description, not a substitute measurement from the Peveril–Zigzag traverse.
Headland B.B. — disturbed limestone and breccia
Disturbed limestone layers pass laterally into breccia. Clements distinguishes these evaporite-replacement rocks from the more typically Cypris limestone lithology of northern DB10; older suggested equivalences should not be treated as an established lithological identity.
Bed DT11 — Caps (basal Purbeck strata at Durlston Head)
The Caps form the basal Purbeck beds at Durlston Head. They are mostly evaporitic, but include stromatolitic limestone at the base and the Lower Celestite Bed. Unlike the classic basal Purbeck sections at some other Dorset localities, the Great Dirt Bed is absent here and no in situ tree stumps have been found. These beds therefore represent a very restricted lagoonal to sabkha setting developed immediately above the Portland limestones, but in a more basinal evaporitic facies than the tree-bearing basal Purbeck sequences better known elsewhere in Dorset.
The following six Caps components retain West’s 1960 numbering as reproduced in Clements’ Figure 4, in upward order. Clements quotes about 28 feet, or 8.5 m, between the top of the Portland limestone and the prominent basal Cypris limestone in that older section. The interval is structurally disturbed; its components are not assigned scale-derived thicknesses or summed with northern DB measurements.
Headland C.1 — lower Hard Cap
Tufaceous limestone forms the lower component of the historical Hard Cap.
Headland C.2 — upper Hard Cap
Laminated crystalline limestone overlies the tufaceous C.1 limestone.
Headland C.3 — lower Soft Cap and lower celestine bed
Shaly crystalline limestone contains abundant celestine and chert. Drag folds at its base are directed northwards.
Headland C.4 — upper Soft Cap
Laminated crystalline limestone contains chert and a smaller amount of celestine, becoming crushed towards the north.
Headland C.5 — shaly limestone above the Soft Cap
Shaly limestone contains northward-directed drag folds.
Headland C.6 — upper celestine bed
The upper celestine-rich layer passes northwards into broken blocks forming part of the Broken Beds. Its structural incorporation is distinct from an extra undisturbed layer stacked above the breccia.
PORTLAND GROUP
Portland Stone Formation (Upper Jurassic, Tithonian)
Bed DT12 — Faulted Portland Stone South Of Durlston Head (context below the Purbeck Group)
South of the major fault at Durlston Head, the Purbeck strata rest against the upper Portland limestones. The exposed Portland Stone includes sea-worn cherty limestones of Portland Chert Member type and higher ooidal freestones of Portland Freestone type. These rocks represent shallow fully marine carbonate-shelf deposition before the abrupt environmental change into the restricted lagoonal and evaporitic Purbeck world above. They are included here because the Purbeck–Portland relationship is one of the defining geological features of the Durlston Head end of the section.
West’s historical headland section also records the immediate Portland substrate beneath the Caps.
Headland P.S. — Portland limestone with top Shrimp Bed
The Shrimp Bed lies at the top of the Portland limestone in Clements’ reproduction of West’s 1960 section. It is retained as the basal context for the local Purbeck contact; no thickness or detailed fauna is inferred from the diagram alone.
Structural Style And Composite Nature Of The Section
The middle-to-southern Durlston Bay section is not a single uninterrupted coastwise log. In the middle of the bay two obvious normal faults downthrow southward and repeat part of the section, producing a limestone spur in which Cherty Freshwater, Cinder and a slice of Intermarine beds reappear. Around the old flats and sea-defence works, parts of the lower Purbeck are obscured. At Durlston Head, major extensional faulting, evaporite flow and the Durlston downbulge tectonically thicken and distort the Broken Beds close to the Portland contact. Any realistic website log must therefore be treated as a composite, faulted section rather than a simple continuous cliff profile.
Depositional Environment
This subsection records repeated oscillation between freshwater, brackish, hypersaline and briefly marine conditions on the latest Jurassic to earliest Cretaceous Purbeck coastal plain. The Cinder Bed marks a short normal-marine incursion with oysters, serpulids and echinoids. The fault-repeated lower Stair Hole slice records low-salinity shell-beach and shallow lagoon conditions that preserved dinosaur footprints and vertebrate debris. The Worbarrow Tout Member below passes from freshwater lake and swamp deposits of the Mammal and Cherty Freshwater beds, rich in molluscs, charophytes, mammals, reptiles and tracks, down into the more saline Soft and Hard Cockle lagoon–sabkha facies with evaporites, halite pseudomorphs, gypsum and dolomite. The Mupe Member continues the restricted lagoonal and evaporitic story in an even more basal form, while the Portland Stone beneath represents the preceding open-marine carbonate shelf.
Total Thickness And Stratigraphic Range Covered Here
The middle-bay-to-head subsection includes the base of the Berriasian Durlston Formation at the Cinder Bed, then descends through most of the upper and middle Lulworth Formation to the Purbeck–Portland junction. The Worbarrow Tout Member alone reaches about 39 m at Durlston, and the full Durlston Formation reaches about 57 m in the bay as a whole, though most of its upper part lies outside the present focus. Because the section is repeated and locally thickened by faults, especially in the central bay and at Durlston Head, it is more accurate to say that this page covers most of the lower Purbeck reference section from the Cinder Bed down to the Portland Stone rather than to assign a single simple measured thickness to the subsection.
References
Clements, R.G. (1993). Type section of the Purbeck Limestone Group, Durlston Bay, Swanage. Proceedings of the Dorset Natural History and Archaeological Society, 114, 181–206.
Westhead, R.K. & Mather, A.E. (1996). An updated lithostratigraphy of the Purbeck Limestone Group in the Dorset area. Proceedings of the Geologists’ Association, 107, 117–128.
Arkell, W.J. (1947). The Geology of the Country around Weymouth, Swanage, Corfe and Lulworth. Memoir of the Geological Survey of Great Britain.
Barton, C.M., Woods, M.A., Bristow, C.R. & Newell, A.J. (2011). South Dorset and south-east Devon and its World Heritage Coast. British Geological Survey Special Memoir.
British Geological Survey Lexicon entries: Durlston Formation, Stair Hole Member, Lulworth Formation, Worbarrow Tout Member, Ridgeway Member, Mupe Member, Portland Stone Formation and Portland Chert Member.
Benton, M.J. & Spencer, P.S. (1995). Fossil Reptiles of Great Britain, Geological Conservation Review Series, including the Durlston Bay account.
Dineley, D.L. & Metcalf, S.J. (1999). Fossil Fishes of Great Britain, Geological Conservation Review Series, including the Durlston Bay account.
Jarzembowski, E.A., Siveter, D.J., Palmer, D. & Selden, P.A. (2010). Fossil Arthropods of Great Britain, Geological Conservation Review Series, including the Durlston Bay account.
West, I.M. (1965, 1975) and Salter, M.G. & West, I.M. (1965) on Purbeck gypsum, celestite, Broken Beds and evaporite tectonics at Durlston Head.
Nunn, J.F. (1991). A geological map of Purbeck Beds in the northern part of Durlston Bay. Proceedings of the Dorset Natural History and Archaeological Society, 113, 145–148.
Allen, P. & Wimbledon, W.A. (1992) on integrated Jurassic–Cretaceous boundary correlation in the Purbeck succession; and Ensom, P.C. and co-authors on the Mammal Bed, Feather Bed, microvertebrate horizons and dinosaur footprints of Durlston Bay.
Safety
This section of Durlston Bay is significantly more challenging and should be approached with caution. Tide times are critical, as access is only possible along the foreshore and the sea often reaches the base of the cliffs. The area is affected by complex tidal conditions, and it is very easy to become cut off if not planned carefully. Always begin your return well before the tide turns.
Access from the Zig Zag path involves a difficult and uneven route over large boulders and rock ledges, often for several hundred metres. Many of these rocks are slippery, unstable or covered in seaweed, making footing hazardous.
The cliffs in this section are highly unstable, with frequent rockfall, landslips and overgrown slopes. The ground can give way without warning, particularly on slumped material, so climbing or approaching the cliff base should be avoided.
Durlston Country Park discourages visits to the beach unless accompanied by an expert. Keep to designated footpaths and follow current local warnings; expert accompaniment does not remove the rockfall, tide and unstable-ground hazards.
Equipment
This section is best suited to more experienced collectors, and while tools are still limited by SSSI regulations, a few essential items can significantly improve results.
Hammering of cliffs and bedrock is strictly prohibited, so collecting should focus on loose material and sediment sampling. Where collecting is permitted, take only small samples of loose fossil-bearing shale on the firm, open foreshore for processing at home; do not sample in-situ beds or the cliff base.
A fine mesh sieve (around 0.5mm) is highly recommended, as many of the most important fossils—particularly mammal teeth and microvertebrate remains—are extremely small. A trowel or small hand tool can be useful only for permitted loose sediment on firm foreshore well clear of cliffs and slipped ground.
Because many fossils from this site are extremely delicate, it is essential to bring sample bags, containers and padding materials. Wet sieving at home is often required to reveal the best finds.
Given the more rugged terrain, including ledges, loose rock and uneven ground, sturdy footwear with good grip is essential. A backpack is recommended for carrying equipment safely across the site.
Cleaning And Treating
Start with a soft dry brush on stable loose specimens. Keep delicate bone, shells and shale supported in their matrix; do not routinely soak or scrub them. Hard limestone, soft clay and gypsum-bearing material need different treatment, so there is no universal 24-hour desalination rule. Seek experienced preparation advice before wet processing an unusual vertebrate specimen, and avoid rapid drying or direct heat.
Do not coat sound fossils routinely. Paraloid B-72 can be useful when a specimen genuinely needs consolidation, but treatment should be chosen and documented by someone familiar with the material. Solubility does not guarantee complete removal from porous fossils. A resin coating is not a substitute for dry storage or a cure for pyrite decay.
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 – Fossil insects from the Lower Cretaceous of southern England
Durlston Bay — GCR fossil fishes
Durlston Bay: Central Zigzag area — Ian West
Durlston Bay: Lower Purbeck Group (Lulworth Formation) — Ian West
Durlston Head — Ian West
Access Rights
This site is a site of special scientific interest (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, 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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