Charmouth (Stonebarrow) Fossil Hunting

1811–1812 – Joseph and Mary Anning’s first major ichthyosaur discovery
Joseph Anning found the skull in 1811, and Mary Anning returned to the same site and excavated the rest of the skeleton in 1812. By early 1813 it had become the first largely complete ichthyosaur to be uncovered and scientifically studied, helping transform understanding of extinction and ancient life.

1814 – Mary Anning’s ichthyosaur entered the scientific literature
After its excavation, the specimen was studied by Sir Everard Home and became one of the fossil discoveries that brought ichthyosaurs to the attention of the scientific world. This was one of the most important early scientific milestones for the Charmouth–Lyme coast.

1820 – the Anning ichthyosaur was recognised as an extinct marine reptile
By 1820 the strange animal found by the Annings had been recognised as an extinct marine reptile rather than a crocodile or fish. This was a major change in interpretation and part of the wider scientific impact of the Charmouth coast discoveries.

1823 – Mary Anning discovered the first complete Plesiosaurus skeleton
In December 1823, Mary Anning discovered the first complete Plesiosaurus skeleton from the Lower Jurassic coast. It became one of the most celebrated fossil finds of the nineteenth century and helped establish the Charmouth–Lyme coast as one of the world’s great marine reptile localities.

1828 – Mary Anning discovered Britain’s first pterosaur
In December 1828, Mary Anning uncovered the remains of the first pterosaur found outside Germany, the fossil later known as Dimorphodon. This added flying reptiles to the already remarkable fossil record of the area.

1829 – coprolites were recognised as fossilised dung
Work by William Buckland on material from the Lyme Regis and Charmouth coast led to the recognition that certain curious stony objects were fossilised dung, or coprolites. This was another major scientific breakthrough linked to the fossil discoveries of this coast.

1858–1859 – Scelidosaurus discovered at Black Ven near Charmouth by James Harrison
Fossils found by James Harrison while working the Black Ven cliffs near Charmouth were sent to Richard Owen, who recognised their importance. This discovery made Charmouth one of the classic British dinosaur localities.

1861 – Scelidosaurus harrisonii formally described by Richard Owen
Owen formally described Scelidosaurus harrisonii in 1861. It became one of the most important early ornithischian dinosaurs ever discovered and remains central to discussions of armoured dinosaur evolution.

June 1955 – the museum acquired J. F. Jackson’s juvenile Scelidosaurus
The British Museum (Natural History) bought a fossil-bearing marlstone nodule found by J. F. Jackson on the beach beneath Black Ven. It contained a small, incomplete articulated skeleton. Its exact source bed is uncertain; Norman’s later study considered the Topstones Bed the likely source.

1968 – preparation of Jackson’s partial Scelidosaurus skeleton published
Arthur Rixon published an account of preparing the juvenile specimen now numbered NHMUK R6704. The work freed its delicate bones from the enclosing nodule and provided material for later anatomical comparisons. The discovery was on the Black Ven shore, within the wider Charmouth–Lyme area covered by this timeline.

1984–1985 – another important Scelidosaurus specimen recovered
Norman records the Bristol specimen, BRSMG Ce12785, as collected from the Topstones Bed by Simon Barnsley and Chris Moore in 1984–1985. It preserves a partial, disarticulated skull and skeleton together with patches of skin impressions and armour, supplementing the earlier discoveries.

December 2000 – David Sole found the most complete Charmouth Scelidosaurus specimen yet discovered
The first parts of this specimen were found in December 2000 by local collector David Sole. Over the following months and years, more pieces were recovered by David and fellow collectors Peter Langham, Jo Anderson, Andrew Sole, Christine Endecott, Rick Taylor and Bernie Abbott. The specimen proved to be over 85% complete, with exceptional preservation including skin and apparent stomach contents.

2000s–2010s – the David Sole Scelidosaurus became recognised as Britain’s most complete and best-preserved dinosaur
The Black Ven Scelidosaurus found by David Sole came to be regarded as Britain’s most complete and best-preserved dinosaur found to date. The specimen also showed that major dinosaur discoveries were still being made on the Charmouth coast in modern times.

2017–2018 – the future Turnersuchus specimen recovered
Paul Turner found the initial block and Lizzie Hingley recovered additional material and prepared the specimen. Its five main blocks emerged between May 2017 and July 2018 from eroded material about one kilometre west of Charmouth Heritage Coast Centre. The fossil comes from the lower Pliensbachian Belemnite Marl Member and includes parts of the skull, jaws, backbone and limbs.

2023 – Turnersuchus hingleyae formally described
The 2017 Charmouth specimen was formally described in 2023 as Turnersuchus hingleyae. The genus name honours Paul Turner, while the species name honours Lizzie Hingley. It is one of the oldest diagnostic thalattosuchians known and one of the most important recent discoveries from the Charmouth coast.

February 2024 – “Gonzo”, the mummified ichthyosaur, found by Chris Moore
In February 2024, local collector Chris Moore found an exceptionally preserved ichthyosaur nicknamed “Gonzo”. Charmouth Heritage Coast Centre reports associated shark teeth interpreted as a possible new hexanchiform species and an exceptionally early record of the group. The proposed shark identification remains provisional pending formal scientific description.

September 2024 – “Enzo”, a complete ichthyosaur, discovered by Chris Moore
Chris Moore discovered and excavated this complete ichthyosaur in September 2024, with special permission from the landowners to remove the specimen. The fossil is thought to represent an undescribed new species, with several unusual skeletal features including a pronounced overbite and an unusual hind paddle.

March–May 2025 – Enzo scanned and publicly presented as a likely new ichthyosaur species
In March 2025 the unusual skull was digitally scanned, and in May 2025 the specimen was publicly named “Enzo” in a Charmouth Heritage Coast Centre competition. Although not yet formally described in the scientific literature, it has been presented as a probable new species-level find from Charmouth.

This is a composite Stonebarrow coastal framework, not a single uninterrupted measured face. Lang’s historical bed names and measurements are distinguished from later BGS member definitions and the Phelps correlation scheme. Individual exposures can be slipped, covered or truncated. The BGS Black Ven Marl Member includes the upper pyritic beds below Hummocky; the proposed Stonebarrow Pyritic subdivision is described within it.

LIAS GROUP

Charmouth Mudstone Formation (Lower Jurassic — Sinemurian to Pliensbachian)

Black Ven Marl Member

Birchi Tabular Boundary And Lower Mudstones (Lang Beds 76–79) — Correlation Context

The formal BGS member begins at the base of Birchi Tabular (76), below the easily recognised local cementstone levels. The shore near Evan’s Cliff exposes higher beds, so the whole basal interval is not implied to be continuously visible beside the access point. The Lower Cement Bed is the boundary bed’s younger marker, Bed 80; intervening mudstones must remain distinct.

Bed 80 — Lower Cement Bed / Lower Cementstone

The Lower Cement Bed (Lang Bed 80) is a laterally variable limestone or dolomitic cementstone, about 0.3 m in the classic coastal account. It is a conspicuous marker near Evan’s Cliff. Callomon’s reassessment identifies an original printing error: the black conchoidal marl with indurated bands belongs to underlying Bed 79 and should not be merged with the cementstone.

Bed 81 — Inter-Cement Mudstones

Dark grey to black mudstones and paper shales between the lower and upper cement beds. These beds are softer and less conspicuous than the cementstones but continue the organic-rich, fissile character typical of the lower Black Ven Marl Member.

Bed 82 — Pavior / Upper Cement Bed

A laterally persistent cementstone horizon above the Lower Cement Bed. It forms a useful field marker at Stonebarrow and has long been used to fix position in the lower part of the Black Ven succession. A harder concretionary band just below it is often referred to informally as the Under-Pavior.

Bed 83 — Obtusus Shales / Stonebarrow Flatstones

Bituminous paper shales about 2.4 m thick in Lang’s account, projecting from the cliff face and often traceable even where the cliff is grassed over. A nodule level within these shales forms the classic Stonebarrow Flatstones horizon. The bed is especially important palaeontologically and has yielded Asteroceras obtusum and insect-bearing concretions; the GCR specifically records important Scelidosaurus material from the younger Topstones (Bed 85), which is kept separate.

Upper Flatstones And Lateral Absence Of Lower Horizons

The upper Flatstones in Bed 83 are the familiar Stonebarrow nodule horizon. The fuller Black Ven reference log distinguishes lower Flatstones, Woodstone, Goldstones and other levels, but they are not all developed here. Callomon records Lower Flatstones absent and Woodstone weak or absent through much of Stonebarrow; this difference is retained rather than copying the western log wholesale.

Yellowstones — Lower Bed 83 Reference Horizon

The GCR Black Ven–Stonebarrow comparative figure identifies Yellowstones as the lowest of this named nodule-horizon series within Bed 83. No distinct mineral composition or thickness is inferred from the traditional name.

Lower Flatstones — Bed 83 Reference Horizon

Callomon’s explicit Black Ven lettered account identifies the Lower Flatstones as Bed 83d, below Woodstone (83f). Lower Flatstones are absent through much of the Stonebarrow section, so this is a retained Black Ven reference horizon rather than a universally exposed local layer.

Woodstones — Bed 83 Reference Horizon

Woodstone is Bed 83f in Callomon’s Black Ven lettered account, above the Lower Flatstones (83d) and below Upper Flatstones (83h). It is weak or absent through much of Stonebarrow and remains a lateral comparison here.

Goldstones — Bed 83 Reference Horizon

Goldstones are independently named in the GCR’s Bed 83 nodule suite. No new precise lettered crosswalk or local thickness is forced from its compressed graphic labels. It is kept distinct from the explicitly correlated Lower Flatstones, Woodstone and Upper Flatstones.

Upper Flatstones — Stonebarrow Flatstone Horizon

Callomon distinguishes Upper Flatstones numbered 83h in the Black Ven log from the correlated Stonebarrow Flatstones numbered 83e. Those western and eastern subdivisions are not interchangeable bed numbers. The GCR describes laminated lenticular limestone nodules with well-preserved fossils. They remain distinct from the lower reference horizons, which are not all developed east of the river.

Fissile Interval Above The Flatstones

The comparative log separately identifies a fissile muddy interval above the upper Flatstones. This preserves the top part of the Bed 83 package instead of treating every named horizon as one nodule bed.

Beds 84–86 — Middle Black Ven Mudstones

The middle part of the Black Ven Marl Member, consisting mainly of dark mudstones and shales with nodular limestone development at some levels. In accessible modern sources these beds are less clearly broken out lithologically than the better-known marker horizons below and above, but they represent the main continuation of the black, ammonite-bearing marl sequence between the Obtusus Shales and the upper stone bands.

Pentacrinite Bed (Lang Bed 84b)

The BGS memoir names the Pentacrinite Bed as Bed 84b. The fuller GCR description makes clear that it is an interval exceeding 2 m of organic-rich mudstone, with scattered groups of Pentacrinites fossilis, often associated with driftwood, rather than one continuous crinoid sheet. Its detailed development and correlatability vary between Black Ven and Stonebarrow.

Topstones (Lang Bed 85)

The GCR comparative section separates the Topstones horizon within the broader Beds 84–86 interval. This useful named level is distinct from both the lower Flatstones and the higher limestone with brachiopods.

The GCR’s provenance discussion specifically assigns important Scelidosaurus specimens to this Topstones interval. The broader history of vertebrate discoveries must not make every Flatstone horizon an identical dinosaur-bearing bed.

Bed 87 — Limestone With Brachiopods

A thin but persistent limestone band higher in the Black Ven Marl Member and an important marker in the Stonebarrow cliff profile. It lies well above the Pavior and helps fix the upper part of the Black Ven succession in the field. As the name suggests, brachiopods are characteristic, though other marine fossils may occur.

Bed 88 — Upper Black Ven Pyritic Marls And Stellare Nodules

Dark mudstones contain the septarian Stellare Nodules (Bed 88f), which sometimes preserve Asteroceras stellare. Pyritised ammonites below the Coinstone are relatively uncommon and may occur as coatings on crushed shells. The more abundant uncrushed pyritic ammonites are associated with the younger beds above the Coinstone, particularly Beds 90–102; these intervals should not be confused.

Bed 89 — Coinstone

An irregular horizon of bored, encrusted and partly pyritised hiatus nodules records a significant non-sequence at Stonebarrow. It marks the top of the lower Black Ven subdivision in the GCR scheme, not the top of the broader BGS Black Ven Marl Member used for this guide’s coloured hierarchy. The latter continues through the upper pyritic Beds 90–102 to the base of Hummocky.

Black Ven Marl Member — Published Coastal Thickness Accounts Differ

Upper Pyritic Interval (Lang Beds 90–102)

The GCR discusses this interval as a proposed Stonebarrow Pyritic Member; it remains within the broader BGS Black Ven Marl definition used here. Dark pyritic mudstones above the Coinstone-area hiatus contain uncrushed pyritised ammonites and fewer large nodules than the lower succession.

Lower Pyritic Mudstones And Lymense Horizon (Beds 90–92)

The characteristic Oxynoticeras lymense fauna lies in this lower interval, below the younger middle mudstones. It should not be assigned to Beds 95–98.

Middle Pyritic Mudstones (Beds 93–98)

The intervening dark mudstones contain pyrite and locally thin beef seams, leading up to the main limestone marker.

Watch Ammonite Stone (Bed 99)

This lenticular limestone is up to about 0.3 m in the published coastal account and contains abundant Echioceras of the aeneum group, with an enriched benthic fauna. Its correct Lang number is 99.

Upper Pyritic Mudstones (Beds 100–102)

These continue above the Watch Ammonite Stone to the Hummocky boundary. The upper part includes a change from laminated to more homogeneous mudstone and a modest increase in benthic diversity.

Belemnite Marl Member

The bed framework below combines directly observed Stonebarrow beds with explicitly identified reference measurements farther east. Hesselbo and Jenkyns (1995) measured Beds 103–109 below Stonebarrow, reconstructed Bed 110 from cliff photographs there, measured Beds 111–115 east of Westhay Water, and measured Beds 116–121 between The Corner and Seatown. The upper dimensions are not transferred to every Stonebarrow or Black Ven exposure. Every main bed is retained, together with subdivisions independently recorded by Bolton (1982); unsupported historical inch values are not presented as modern measurements.

Bed 103 — Hummocky Limestone

The irregular nodular limestone marks the lithostratigraphic base of the member. Its bioclastic fabric includes burrows, reworked limestone fragments and worn skeletal material. Hesselbo and Jenkyns discuss mixing and erosion through this basal interval rather than an undisturbed, instant boundary. BGS gives approximately 0.10–0.15 m for the thin basal and terminal limestones in its coastal summary; the GCR describes local merging of Beds 103–105 into a thicker complex bed below Black Ven.

Bed 104 — Clays Above Hummocky

The thin muddy interval above the basal limestone includes small nodules and reworked clasts. The GCR describes approximately 0.10 m in its coastal account. Published interpretations place the earliest Pliensbachian either at Hummocky or above parts of this mixed interval; the secure lithological order is kept separate from that disputed time boundary.

Bed 105 — Apoderoceras Or Armatus Limestone

A pale bioclastic limestone with distinctive burrowing and large ammonites forms the next resistant marker. The GCR coastal account gives approximately 0.30–0.40 m. It was included in the directly measured Stonebarrow part of the 1995 composite; this range is not inferred from its drawing scale.

Bed 106 — Lower Pale Marl Rhythms

The lower pale interval continues above the Armatus Limestone with alternations of calcareous mud and harder carbonate-rich layers. Bolton’s log retains subdivisions 106a, 106b and 106c. Their identities are retained without assigning unverified individual inch measurements.

Subdivisions 106a–c

These three retained log subdivisions belong within Bed 106. Their separate identification is supported by Bolton’s figure; the old thickness assigned to each is held in the historical comparison rather than inferred anew.

Bed 107 — Lower Pale Indurated Band

A separately numbered thin, harder pale interval lies between Beds 106 and 108 in the published lithological framework. The lower Taylori assemblage includes Apoderoceras and Phricodoceras in the BGS account, but an exact bed-specific faunal name is not imposed here without its original evidence.

Bed 108 — Marl Rhythms With Two Bituminous Horizons

Bolton records two organic-rich shale horizons in this interval: one at the base and a second approximately 0.3 m below Bed 109. The latter yielded documented vertebrate material in that field study. These are useful lithological subdivisions within the marl package, not a reason to promise fossils in every exposure. The particular old faunal bed label is not required for identifying the supported rock succession.

Lower Bituminous Shale In Bed 108

The basal organic-rich horizon is distinguished from the upper shale in Bolton’s direct field description.

Upper Bituminous Shale In Bed 108

Bolton describes this second horizon about 0.3 m below Bed 109; it is not simply another name for all of Bed 108.

Bed 109 — Upper Indurated Band Of The Lower Pale Interval

A harder pale band closes the lower marl package below the thick Bed 110 succession. It remains a separately numbered horizon in the 1995 measured framework; no exact local thickness is assigned from the graphical scale.

Bed 110 — Lower Darker Marl Succession

The thick lower dark interval contains subtle carbonate-rich and carbonate-poor alternations, with organic-rich shale towards its base. The 1995 reconstruction of this bed was made from photographs of Stonebarrow cliff. Bolton distinguishes the principal historical subdivisions 110a and 110b and, separately, five study units I–V based on belemnite assemblages. The latter are research subdivisions, not new formal members.

Hawkfish Ledge — Stonebarrow Foreshore Expression Of Bed 110

Callomon describes Bed 110 forming Hawkfish Ledge and a long low-tide foreshore outcrop east of the basal Belemnite Marl limestones. This is a locality-specific field name, not an additional stratigraphic bed.

Bed 110a

The lower historical division contains faint marl rhythms and basal organic-rich levels. Bolton’s Dorset account describes about 8.5 m, while the 1995 presentation reconstructs the local cycle pattern photographically. The source-specific estimate is not a precision measurement derived from the figure.

Bed 110b

The upper historical division participates with Bed 111 in the more clearly expressed rhythmic succession. Its separate identity is retained, but no independent modern individual thickness is asserted.

Bed 111 — Lower Pale Band

This conspicuous light-coloured package includes three harder pale components separated by softer marls. Bolton retains the five subdivisions 111a, 111b, 111c, 111d and 111e. His discussion associates this interval and Bed 113 with brachiopods including Cincta. The 1995 section for these beds was measured east of Westhay Water, not at the same face used for Bed 110.

Retained Subdivisions 111a, 111b, 111c, 111d, 111e

These lettered subbeds are independently recorded in Bolton’s lithological framework. The description preserves the full subdivision sequence while withholding unverified historical inch-level dimensions; the contrasting marls and harder pale intervals are described at the supported package level above.

Bed 112 — Lower Darker Band

Darker, less carbonate-rich alternations follow the lower pale package; Bolton notes an organic-rich shale towards the top. The six recorded subdivisions, 112a through 112f, are preserved in the framework, without presenting the old individual inch values as newly verified dimensions.

Retained Subdivisions 112a, 112b, 112c, 112d, 112e, 112f

These lettered subbeds are independently recorded in Bolton’s lithological framework. The description preserves the full subdivision sequence while withholding unverified historical inch-level dimensions; the contrasting marls and harder pale intervals are described at the supported package level above.

Bed 113 — Middle Pale Band

The next pale rhythmic package is separately identified in the GCR and 1995 figures. Bolton retains subdivisions 113a, 113b, 113c, 113d and 113e and records ammonites and brachiopods in this part of the succession. Its repeated pale and darker components remain important field detail even where no individual numerical thickness is assigned.

Retained Subdivisions 113a, 113b, 113c, 113d, 113e

These lettered subbeds are independently recorded in Bolton’s lithological framework. The description preserves the full subdivision sequence while withholding unverified historical inch-level dimensions; the contrasting marls and harder pale intervals are described at the supported package level above.

Bed 114 — Middle Dark Band

This darker marl interval separates the middle and upper pale packages. Bolton describes the fauna of Beds 113–114 as chiefly ammonites and brachiopods, with belemnites less prolific than in much of the surrounding member. It is not presented as uniformly rich in all fossil groups.

Bed 115 — Upper Pale Band

Numerous finer pale–dark rhythms make this a distinctive package. Bolton explicitly attributes Lang’s 8 ft (about 2.4 m) to Westhay Water and records thinning to about 1.5 m at Ridgewater. These two named-locality values are retained as variation, not merged into a universal Stonebarrow measurement. The historical narrow taxon “zone” is not used as the modern zonal definition.

Bed 116 — Upper Dark Band

This dark calcareous clay lies above the upper pale package. Bolton reports a marked lack of belemnites in this bed in his study, despite otherwise broadly similar marine fauna. In the 1995 composite, this and higher beds were measured in the low cliffs towards Seatown.

Bed 117 — Upper Paler Marls

The succeeding lighter marl interval restores a more visibly calcareous component. Bolton records belemnites here. Lang’s earlier 1913 account gives 2 ft, but that historical figure is not silently treated as a new 1995 local measurement.

Bed 118 — Upper Darker Marls

The upper dark succession retains four historical subdivisions. Bed 118a is the lower marl interval with relatively abundant belemnites in Bolton’s study. Bed 118b is the thin historical one-inch horizon directly corroborated by Bolton, but he found it lithologically indistinguishable from 118c; its former Coeloceras pettos “zone” is obsolete. Bed 118c and Bed 118d continue the muddy rhythmic succession towards the Belemnite Shales. Modern measured values from different studies are not silently substituted for the old whole-bed dimensions.

Bed 118a

Lower marl subdivision; its fossil abundance is described in the main entry.

Bed 118b

Thin historical horizon, one inch in the account explicitly cited by Bolton; not a separate modern ammonite zone.

Bed 118c

Marl rhythms above the thin historical 118b horizon; the two are not readily separated by lithology in Bolton’s account.

Bed 118d

Upper marl subdivision below the Belemnite Shales, retained separately in the primary log.

Bed 119 — Belemnite Shales And Inferior Belemnite Horizon

The sediment changes from the stronger calcilutite–clay rhythms to alternating more and less calcareous shale. Hesselbo and Jenkyns separately identify an Inferior Belemnite Bed approximately 60 cm below the main Belemnite Bed in their upper Corner–Seatown measured section. That relative position is reported directly, without inventing an exact lettered subbed or transferring its distance to every cliff.

Bed 120 — Upper Pyritic Interval And Belemnite Bed

The historical subdivisions remain distinct. Beds 120a–b comprise dark organic-rich pyritic shale with scattered nodules and a concentration at the top, as independently described by Bolton. Bed 120c is the main condensed belemnite-rich horizon identified by BGS. Beds 120d and 120e have broadly similar muddy lithology but fewer pyrite nodules in Bolton’s account. The highest thin subdivision must not be conflated with the main belemnite concentration.

Beds 120a–b — Pyritic Marls

The lower pyritic package and its upper nodule concentration are retained together as in Bolton’s description; their unverified old one-foot aggregate is not treated as a modern measured value.

Bed 120c — Main Belemnite Bed

Hesselbo and Jenkyns describe the named Belemnite Bed as about 7–8 cm thick and 34 cm below Belemnite Stone in their upper measured section. It is a diffuse dark pyritic, organic-rich mudstone rich in belemnites and bivalves. These are Corner–Seatown source values, not exact dimensions of all Stonebarrow or Black Ven occurrences.

Bed 120d

This intervening upper muddy subdivision is retained separately from the main Belemnite Bed and the highest crumbly horizon. Bolton reports lithology broadly similar to the lower pyritic package, with fewer nodules; no exact thickness is supplied here.

A documented Stonebarrow gastropod. In 1928, L. R. Cox described specimen G26217, which he had collected on Stonebarrow Cliff, from Bed 120d. He referred this unusually broad, weakly ornamented shell to a variety of Pleurotomaria similis, rather than naming a new species. This is a specific historical specimen record from the upper Belemnite Marls; the identification is retained as Cox’s usage, not a modern reassessment of all similar loose shells.

Bed 120e — Uppermost Retained Subdivision

Bolton retains the highest subdivision within the upper muddy interval. Lang’s 1928 detailed sequence describes Bed 120e as the uppermost half-inch of the Crumbly Bed, composed of greyish-black friable marl. That is a historical coastal reference-section value, not a newly measured thickness at this cliff. Lang used Crumbly Bed for subdivisions 120c–e, whereas the GCR Blockley comparison specifically correlates with Dorset Bed 120e. The broader historical name must therefore not be confused with either the single uppermost subdivision or the main belemnite concentration at 120c.

Bed 121 — Belemnite Stone

This terminal pale concretionary limestone is highly condensed and rich in belemnites and other skeletal material. Hesselbo and Jenkyns explicitly record 4–5 cm in their upper Corner–Seatown section. The BGS memoir uses a broader approximately 0.10–0.15 m description for the member’s boundary limestones, and other published local accounts differ. These are attributed source/locality values, not a fabricated single agreed thickness. The stone forms the top of the member below Green Ammonite mudstones.

Belemnite Marl Member Thickness And Exposure Scope

BGS 2011 describes approximately 25 m in the Stonebarrow cliffs. Other sources give approximately 23 m for the coastal framework and 22–25 m at Black Ven. These source-scoped totals are not added together or imposed on a single currently visible face. The thin upper-marker measurements above derive from the specifically stated reference exposures.

Green Ammonite Member

The principal Lower Limestone, Red Band and Upper Limestone framework is documented in the Stonebarrow-to-Golden Cap coastal succession. The detailed Phelps numbering below is a correlation framework: Hesselbo and Jenkyns measured its lower and upper parts around Golden Cap, not as one complete Stonebarrow log. Stonebarrow’s classic member is about 15 m, appreciably thinner than Golden Cap. The numbered packages and marker lithologies are retained for correlation; neither their reference thicknesses nor every individual upper bed is claimed to have been remeasured here.

Phelps Beds 7–13 — Lower Clays

Medium grey mudstones forming the basal part of the Green Ammonite Member above the Belemnite Stone. These beds are ammonite-rich and represent the lowest of the seven classic Green Ammonite subdivisions recognised by Lang. They form the basal clay division below the first principal limestone horizon.

Phelps Bed 14 / Lang Bed 123a — Lower Limestone

A persistent horizon of flattened blue-grey nodules forming the first of the three principal limestone markers in the Green Ammonite Member. This bed is one of the key datums at Stonebarrow and is associated with the lower Green Ammonite fauna.

Phelps Beds 15–20 — Lower Red-Band Clays

Grey mudstones above the Lower Limestone and below the Red Band. These beds represent the second major clay division of the member and continue the ammonite-rich marine mudstone facies. In Lang’s sevenfold scheme they correspond to the Lower Red-band Clays.

Phelps Beds 21–23 / Lang Bed 126 — Red Band

A series of three red-weathering limestones separated by shales. This is the middle principal marker of the Green Ammonite Member and the most visually distinctive bed group in the member. It is a classic datum for the middle Green Ammonite fauna.

Phelps Beds 24–31 — Upper Red-Band Clays

Grey mudstones between the Red Band and the Upper Limestone. These beds form the broad upper clay interval of the member and are the highest thick mudstone division before the uppermost limestone marker.

Phelps Beds 32, 33 And 34 / Lang Bed 129 — Upper Limestone Interval

The Upper Limestone is a composite marker horizon. Phelps Bed 32 is the lower limestone, Bed 33 is the intervening blue-grey clay, and Bed 34 is the upper limestone. Together they form the third principal limestone datum in the Green Ammonite Member and carry the upper Green Ammonite fauna.

Phelps Bed 32 — Lower Upper-Limestone Bed

The lower limestone component of the composite Upper Limestone marker.

Phelps Bed 33 — Intervening Clay

The blue-grey clay between the two limestone components is a separate bed, not part of a single solid limestone.

Phelps Bed 34 — Higher Upper-Limestone Bed

The higher limestone completes the composite marker; the exact local thickness is not inferred from a Golden Cap log.

Phelps Beds 35–41 — Upper Clays In The Coastal Correlation Scheme

Uppermost medium grey mudstones of the Green Ammonite Member above the Upper Limestone. The highest part is especially important: the upper 2 metres, Lang’s beds 132b–c and Phelps’ beds 40–41, are dark and highly pyritic, lithologically unlike the rest of the member and marking the upper Green Ammonite interval in the coastal reference scheme. At Stonebarrow, the preserved succession passes into the basal Dyrham beds in the areas where these survive the Cretaceous overstep.

Typical Green Ammonite Fossils

Ammonites include Androgynoceras and Aegoceras in the main Green Ammonite succession, with Amaltheus characteristic higher in the coastal framework. The name refers to greenish calcite in some ammonite infills, not to uniformly green iron-rich nodules. Assemblages typical of the underlying Belemnite Marl must not be merged indiscriminately into this member.

Green Ammonite Member: Approximately 15 m In The Classic Stonebarrow Account, Compared With Approximately 34 m At Golden Cap

Dyrham Formation

Eype Clay Member — Basal Preserved Interval

Three Tiers And Associated Sandy Mudstones

The GCR records a few metres of Dyrham Formation preserved on the western flank of Stonebarrow beneath the Cretaceous overstep. The Three Tiers sandstone package marks the basal Eype Clay interval. The full Eype Clay log farther east is not imported into this thin preserved remnant.

SELBORNE GROUP

Gault Formation

Basal Cretaceous Unconformity

Cretaceous cover rests across an erosional surface that cuts the Jurassic succession. Historical Stonebarrow accounts distinguish this high, often slipped cover from the lower fossiliferous shore; no complete local Gault measurement is assigned here.

Upper Greensand Formation

Sandy Cover And Derived Hillwash

Upper Greensand higher on Stonebarrow Hill supplies sandy and cherty hillwash to lower slopes. The published Evan’s Cliff account specifically describes this derived cover; transported debris is kept distinct from an undisturbed Upper Greensand section at beach level.

Depositional Environment

The Stonebarrow succession records a long shallow-marine history in which dark organic-rich mudstones, paler calcareous marls and irregular condensed limestone horizons alternate in response to changing sediment supply, carbonate productivity, oxygenation and pauses in deposition. The Black Ven Marl Member is dominated by dark organic-rich mudstones and cementstones, the Belemnite Marl Member by strongly developed pale–dark marl couplets and condensed fossil horizons, and the Green Ammonite Member by medium grey ammonite-rich mudstones divided by three major limestone marker horizons.

Composite Locality: No Summed Total Assigned Across These Separate And Partly Truncated Exposures

References

Lang, W.D. (1914). The geology of the Charmouth cliffs, beach and fore-shore.
Lang, W.D. & Spath, L.F. (1926). The Black Marl of Black Ven and Stonebarrow, in the Lias of the Dorset coast.
Lang, W. D., Spath, L. F., Cox, L. R. and Muir-Wood, H. M. (1928), The Belemnite Marls of Charmouth, a Series in the Lias of the Dorset Coast, stratigraphic and belemnite section, pp. 179–222.
Cox, L. R. (1928), The Gastropod and Lamellibranch Molluscs, pp. 233–245 in the Charmouth study.
Lang, W.D. (1936). The Green Ammonite Beds of the Dorset Lias.
Phelps, M.C. (1985). Refined ammonite biostratigraphy for the Lower Pliensbachian of West Dorset.
British Geological Survey Lexicon: Black Ven Marl Member, Belemnite Marl Member, Green Ammonite Member.

Hesselbo and Jenkyns (1995), measured sections and exact exposure provenance, pp.115–119. Bolton (1982), independently described beds and retained subdivisions, pp.18–22 and Figure 2. BGS (2011), formal member framework and Figures 11–12.

GCR Blockley comparison: explicit historical Dorset Bed 120e correlation.