Wren’s Nest Fossil Hunting

1839 – Wren’s Nest enters the Silurian geological record
Roderick Murchison published a geological section through Wren’s Nest in his work defining the Silurian succession. A view from the hill towards Dudley Castle, drawn by his wife, accompanied the account. The section documents the exact hill; the much wider body of fossils labelled “Dudley” should not all be assigned to Wren’s Nest.

1925–1945 – Later surface quarrying changes the exposures
Surface limestone extraction resumed in 1925 and was recorded on both flanks in 1936, with blasting documented in 1937 and final extraction in 1945. This later open-quarry phase is important when interpreting the surviving landscape. General accounts that place the end of working in 1924 or 1925 do not describe the whole subsequent surface-extraction history.

1939 – Butler describes the historical limestone succession
A. J. Butler described a composite succession on the south-western side of Wren’s Nest, around the lime kilns and Seven Sisters. His Basement Beds, Lower Quarried Limestone, Nodular Beds, Upper Quarried Limestone and Passage Beds became central to later descriptions. Several of those exposures subsequently deteriorated, were infilled or became inaccessible, so this is not the same section as the later NCC cutting.

1956 – A National Nature Reserve is declared
Wren’s Nest was declared a National Nature Reserve for its exceptional geological interest. The designation recognised the value of its limestone succession, fossils and structures and established a lasting framework for conservation and geological education.

2 March 1957 – Mons Hill is added to the reserve
The reserve was extended to include Mons Hill. This brought the northern hill and its geological exposures into the protected area, while leaving Mons Hill’s individual scientific sections distinct from measured composites on Wren’s Nest Hill.

1966 – A Wren’s Nest bryozoan is formally described
Kenneth P. Oakley published Favositella anolotichoides, with holotype D33926 and eight paratypes from Wren’s Nest. The local material came from the Upper Middle Nodular Beds near the south-western lime kilns. The year marks formal description; it does not establish when the specimens were collected.

6 November 1967 – The first official geological trail opens
An official geological trail was launched to interpret the reserve’s exposures. It made the folded succession, fossil-rich limestones and quarry landscape more useful for teaching and visitors, building on the site’s scientific protection.

1975 – The overlying muddy succession is reinterpreted
J. M. Hurst proposed the Birmingham Siltstone Formation for the lowest muddy beds above the limestone, using Wren’s Nest as its type locality. Its boundaries and age interpretation were subsequently questioned, and most later accounts retained the Lower Elton Formation. The proposal remains an important episode in the changing interpretation of the Wenlock–Ludlow transition.

January–February 1977 – The NCC excavates a new scientific cutting
The Nature Conservancy Council opened a trench through the Nodular Limestone Member on the eastern side of the hill and improved adjacent exposures. The resulting section became a major teaching and research reference and underlies the later published measured composite. Its creation was a conservation and scientific intervention, not permission for visitors to excavate.

1981 – Petrology explains contrasting limestone fabrics
P. G. Oliver published a detailed study of western-flank rocks, distinguishing six petrographic and lithological classes. The work connected fossil debris, carbonate mud, cement and limestone texture with changing conditions of deposition, helping to explain why superficially similar fossil-bearing rocks preserve different environmental information.

1983 – Three local limestone members are formalised
K. J. Dorning’s stratigraphic work helped establish the Lower Quarried Limestone, Nodular Limestone and Upper Quarried Limestone members used in subsequent West Midlands accounts. The subdivisions retain a local relationship with the historically worked beds and should not be confused with separate member schemes proposed elsewhere.

1990 – A revised trail and conservation account are published
A revised geological trail and handbook were launched on 1 June, developing the interpretation of the reserve’s rocks and geological features. The SSSI citation also records notification under the Wildlife and Countryside Act in 1990, documenting the protected scientific interest. The reserve and SSSI are related designations whose boundaries and legal histories should not be treated as interchangeable.

1992 – Carbon isotopes add an environmental record
R. M. Corfield and colleagues published a carbon-isotope interpretation based on the Wren’s Nest succession. The work added a chemical record to the physical beds and fossils. Later re-examination identified a missing interval in the older composite alignment, showing why a historical isotope curve cannot simply be treated as an uninterrupted measured log.

7 March 2001 – A major collapse affects the Ripple Beds
A substantial collapse at the Ripple Beds changed an important scientific and visitor exposure. The event illustrates the instability of old quarry faces and the need to distinguish a published section from the condition and accessibility of the same feature at a later date.

2001–2002 – Seven Sisters suffers a major roof collapse
A major collapse at Seven Sisters led to stabilisation measures and restrictions around the workings. The event is separate from the earlier Ripple Beds collapse. Accounts differ between October 2001 and 2002 for this major mine collapse, so a broader date is retained here. Subsequent restoration of viewing facilities did not establish unrestricted access to the mine interiors.

21 October 2004 – Mining remains gain scheduled protection
Scheduled monument protection was confirmed for important industrial archaeological remains at Wren’s Nest and its associated mines. This recognised the workings as evidence of limestone extraction and transport, complementing the protection of the geological exposures and fossils.

2007 – Fossil preservation is linked to sedimentary setting
David C. Ray and Alan T. Thomas examined how sedimentary facies and burial processes helped preserve exceptionally complete skeletal fossils. Their work combined field evidence at Wren’s Nest with material from wider Dudley museum collections, distinguishing local sedimentary observations from fossils with less precise historical provenance.

2009–2010 – Repeated shallowing intervals are correlated
David C. Ray and colleagues used upper Wenlock sections to develop a regional sequence-stratigraphic framework, with Wren’s Nest as an important reference. The resulting parasequences describe packages of environmental change rather than new formal rock members. Local logs remain distinct from comparison sections and boreholes elsewhere. The paper appeared online in 2009 and in its journal volume in 2010.

2011 – Volcanic ashes provide correlation tests
A petrographic and geochemical study compared fifteen sampled Wren’s Nest bentonites with seven from Wenlock Edge. The work tested the usefulness of altered ash as marker horizons and showed why similar-looking clay bands are not enough to establish a secure correlation. These are analysed samples, not a census of every ash bed on the reserve.

27 September 2011 – Trails and viewing facilities reopen
The Ripples Through Time improvements opened new or improved routes, interpretation and viewing facilities, including external viewing areas around Seven Sisters. The work increased opportunities to understand the geology while retaining fences, engineering safeguards and restrictions around the mine.

2012 – An ash horizon gains a numerical age tie
Zircon dating of WNH15 from the Lion’s Mouth scientific section provided an age tie subsequently cited as 427.86 ± 0.32 million years. The result constrains a particular ash horizon and regional correlations; it is not a single age for every limestone bed or fossil in the reserve.

2017–2018 – Conodont communities are compared across environmental change
Emilia Jarochowska and colleagues examined conodont palaeocommunities across changing late Wenlock environments, including Wren’s Nest material within a multi-locality study. The analysis highlighted the influence of facies and sampling when interpreting diversity and turnover. Its pooled totals must not be presented as a reserve-only count.

2019–2020 – Isotopes and revised section correlations refine the succession
A high-resolution study by David C. Ray and colleagues combined carbon isotopes with sequence stratigraphy to reassess the late Wenlock record. Separate Wren’s Nest and Mons Hill sample series were distinguished from Castle Hill and other regional localities. The work revised earlier alignments and the placement of the Upper Quarried Limestone boundary relative to the mega-rippled grainstone.

2021–2022 – Stromatoporoid specimens are systematically revised
Stephen Kershaw, Anne-Christine Da Silva and Consuelo Sendino revised British Silurian stromatoporoids, incorporating field and museum specimens from Wren’s Nest. Their local tabulation contains 85 specimens across eleven named species and an unidentified category, while separate reef assemblages preserve differences between particular buildups. The monograph bears a 2021 date and appeared online in January 2022.

2025 – A regional framework retains the local tripartite subdivision
A preliminary geological framework proposed changes to parts of the Welsh Borderland succession while retaining the three established limestone members in the West Midlands. For Wren’s Nest, this is a useful distinction between proposed regional nomenclature and the local unit names used in the current formal lexicon.

Scope and reading order. This account concerns Wren’s Nest National Nature Reserve, including Mons Hill. The succession is assembled from named exposures around the folded inlier: no single face displays the whole sequence. The 1977 NCC cutting and adjacent exposures provide the 30-interval composite described first, from oldest to youngest. Later measured sections, parasequences, ash samples and fossil studies follow as independent accounts; their thicknesses are not added to that composite.

Rock units and geological time. The local bedrock passes upwards from the Coalbrookdale Formation through the Much Wenlock Limestone Formation and into the Lower Elton Formation. The limestone has three formal West Midlands members: Lower Quarried Limestone, Nodular Limestone and Upper Quarried Limestone. Wenlock Series and Homerian Stage are divisions of geological time within the Silurian System; Ludlow Series and Gorstian Stage succeed them. They are not additional rock formations, and a formation boundary need not coincide with a time boundary.

Structure and exposure. The roughly 1.5 km ridge is a pericline, a fold that closes at both ends, with Coalbrookdale mudstones in its core and the younger limestones dipping away on its flanks. The GCR describes dips commonly around 45–60° and locally about 80°, with a north–south fault downthrowing westwards, a north-west–south-east branch across the fold, and a reverse fault affecting the Upper Quarried Limestone and Lower Elton on the south-west side. Quarrying followed the two purer limestone members and left the muddier Nodular Limestone as intervening higher ground. These structures, old excavations, slumping and covered gaps explain why separate sections must be correlated.

What the composite thicknesses mean. Adding the published intervals gives 16.16 m of Lower Quarried Limestone, 31.05 m of Nodular Limestone and 8.60 m of Upper Quarried Limestone, or 55.81 m of Much Wenlock Limestone in this composite. With 0.17 m of Coalbrookdale below and 13.12 m of Lower Elton seen above, the logged total is 69.10 m. NCC01–NCC30 below are editorial identifiers for the 30 published intervals, not bed numbers printed in the original source. The figure gives NCC21 as 2.81 m. These numbers describe the historical composite, not one presently open continuous visitor section.

Coalbrookdale Formation

Uppermost part only. The Coalbrookdale Formation forms the older mudstone core of the inlier. Its upper boundary is transitional; the current BGS definition places the Much Wenlock Limestone base at the lowest regularly bedded limestone. The substantial regional thickness of the Coalbrookdale Formation is not exposed in this log. The BGS Lexicon does not assign it a parent group.

NCC01: basal mudstone, 0.17 m seen. Only 0.17 m of pale greenish-grey mudstone is seen at the foot of the composite, resembling the mudstone immediately above. The GCR regards its assignment to Coalbrookdale as probable.

Much Wenlock Limestone Formation

A changing shallow-marine carbonate platform. Lime mud, broken skeletal material, thin mudstone partings, volcanic ashes and local reefs record changing conditions on the inner Midland Platform. Reef and inter-reef facies vary laterally, while intervals dominated by muddy sediment alternate with coarser, more strongly agitated carbonate deposits. The current BGS Lexicon assigns the formation a Homerian age and no parent group; its type-area thickness is not the thickness at Wren’s Nest. Later high-resolution correlations place the approximate Wenlock–Ludlow boundary within the upper transitional succession, so the time boundary must not simply be drawn at the top of all limestone.

Lower Quarried Limestone Member

Definition and local variation. Grey bioclastic and micritic limestones, shelly fossils, mudstone partings and local reef bodies characterise this member. The lower boundary lies in the transition from Coalbrookdale mudstone; the upper boundary marks the passage into mudstone-rich, nodular beds. BGS gives 12.2–16.2 m for Wren’s Nest, compared with the 16.16 m sum in the following NCC composite. The historical Basement Beds are included in this member in the GCR account, but later study diagrams place that label partly in the upper Coalbrookdale Formation. The two usages describe a transitional interval and must not be counted as two extra units.

NCC02: 1.93 m. Pale greenish-grey mudstone contains limestone nodules. At its base is an 8 cm, medium-grained, coarsely crystalline limestone band; that band is included in the 1.93 m interval.

NCC03: 1.45 m. Shale and flaggy limestone occur in approximately equal proportions, with the limestone forming irregular, nodular sheets.

NCC04: 2.30 m. Bedded limestone is more nodular and has thicker shale partings than the beds above. Drifts of shell debris and a large Favosites colony occur at the base. This was the lowest worked limestone bed in the source section.

NCC05: 2.25 m. Massive, non-nodular, blue-grey limestone forms medium-grained beds up to 20 cm thick. Patchy greenish-grey and yellow-brown shale partings separate them; the base of the interval is indistinct.

NCC06: 2.50 m. Limestone beds reach 20 cm thick and are more irregular and nodular than those above.

NCC07: 0.90 m. Irregularly bedded limestone has a conspicuous bedding surface at its base.

NCC08: 1.19 m. Limestone similar to the adjacent bedded intervals is separated by appreciable shale partings.

NCC09: 1.60 m. Hard, muddy, fine-grained, medium-grey limestone has thin shale partings. Beds thicken upwards, with the highest reaching 24 cm.

NCC10: 0.50 m. A massive fine-grained limestone bed becomes particularly muddy towards its top.

NCC11: 1.28 m. Limestone beds up to 15 cm thick are comparatively even below and irregular or nodular above. The figure records “ballstones” with bryozoans and corals and identifies this as the highest worked bed. The GCR text nevertheless reports no bioherms in the NCC cutting or its immediately adjacent exposures, so the figure’s term alone does not establish an in-place reef geometry here.

NCC12: 0.26 m. A massive limestone bed, 26 cm thick, formed the roof of the quarry workings.

Basal limestone marker. The 8 cm basal marker is the limestone already described within NCC02, not an additional interval.

Graptolite horizon. The GCR cites a specimen identified as Monograptus flemingii from 2.4 m above the Much Wenlock Limestone base. It is a specifically positioned graptolite record; other historical graptolite finds often lack comparable bed control.

Upper stromatoporoid-rich interval. The GCR records abundant stromatoporoid colonies in approximately the upper 1.5 m of the Lower Quarried Limestone. This is an interval within the member, ending at its 26 cm roof bed, rather than a separate thickness to append.

Nodular Limestone Member

Definition and contrasting thickness accounts. Grey to buff nodular limestone alternates with green-grey calcareous mudstone, with occasional bioclastic limestone beds, bentonitic tuffs and reefs. Nodules and lenses become less coarsely crystalline, muddier and more laterally continuous upwards in the NCC description. Its 31.05 m composite sum is distinct from the BGS Wren’s Nest range of 31.1–37.8 m and the 27.8–31.0 m range used in the 2010–2011 research accounts. Different definitions, sections and measurements are retained rather than averaged. “Nodular Beds” and “Nodular Member” are older source names for the current Nodular Limestone Member.

NCC13: 0.95 m. Irregular flaggy limestone with shale partings.

NCC14: 2.33 m. Large ovate/elongate nodules and massive lenticular coarse limestone bands up to 20 cm in pale-grey shale.

NCC15: 3.50 m. Small ovate/elongate coarse crystalline nodules in pale-grey silty shale; a few thicker lenses below.

NCC16: 1.31 m. Ovate elongate coarse crystalline limestone nodules in pale greenish-grey shale.

NCC17: 2.00 m. Pale greenish-grey silty mudstone with coarse crystalline limestone bands and nodules.

NCC18: 1.63 m. Ovate nodules up to 20 cm above; coarse beds up to 7 cm below, within shale.

NCC19: 0.80 m. Massive limestone with crinoid debris below and stromatoporoids above.

NCC20: 1.20 m. Small ovate coarse limestone nodules in shale; central 10 cm limestone band with irregular base.

NCC21: 2.81 m. Medium/dark-grey coarsely crystalline elongate lenses/bands up to 6 cm in pale greenish-grey shale.

NCC22: 2.42 m. Ovate nodules with few elongate lenses in pale greenish-grey silty shale.

NCC23: 2.50 m. Roughly equal shale and limestone; discontinuous lenses/ovate nodules up to 7 cm and shale partings up to 10 cm.

NCC24: 5.10 m. About 75% elongate limestone lenses and 25% grey shale; wider separation and irregular upper/lower surfaces; little crystalline calcite.

NCC25: 4.50 m. About 85% elongate lenses and 15% grey shale; pale muddy fine-grained limestone with recrystallisation and patches of pure calcite.

Lower historical bentonite marker. The GCR identifies a bentonite approximately 6 m above the base of the Nodular Limestone in its local account. No specific WNH sample number is assigned here solely from that height.

Upper historical bentonite marker. A second bentonite lies approximately 9.7 m above the member base in the same account. It remains a source-specific position, independent of the later WNH numbering unless a correlation is demonstrated.

Upper Quarried Limestone Member

Definition and the Ripple Beds boundary problem. This limestone-dominated member overlies the muddier Nodular Limestone and passes upwards into pale-grey silty calcareous mudstone of the Lower Elton succession. BGS gives 8.6–10.4 m at Wren’s Nest; the NCC composite is 8.60 m, while the independently measured 2011 Mons Hill trench contains 9.7 m. Older GCR and trail descriptions assign the Ripple Beds to the upper Nodular interval. Ray and colleagues’ later framework places the Upper Quarried base about 0.5 m below the conspicuous mega-rippled grainstone. The same named feature therefore has differing member assignments in the literature; the boundary schemes are not interchangeable.

NCC26: 1.90 m. Pale/medium-grey medium/coarse lenticular flaggy beds up to 12 cm; pale-grey shale bands up to 10 cm; lowest worked bed in trench.

NCC27: 4.22 m. Coarse massive blue-grey limestone; beds thinner below with shale partings.

NCC28: 1.18 m. Irregular nodular limestone/shale partings; many stromatoporoid balls at top.

NCC29: 1.30 m. Pale-grey silty shale with limestone bands/nodules; former Passage Beds included within member in this source.

Passage Beds. The GCR includes a 1.30 m upper transitional interval within the Upper Quarried Limestone Member, represented by NCC29. Ray and colleagues describe approximately 2.5 m of transitional, mud-rich strata in their 2010 Dudley account and distinguish the Passage Beds as PS12 in later figures. These are different scoped usages of a historical name, not additional formal members or automatically equivalent thickness measurements.

LOWER LUDLOW SHALES GROUP

Scope of this group name. The BGS Lexicon lists Lower Ludlow Shales Group as the parent of the Lower Elton Formation, although the formation entry is marked “Pending Upgrade”. That parent relationship applies here to the overlying Lower Elton, not to the Much Wenlock Limestone or Coalbrookdale formations.

Lower Elton Formation

Mudstone above the limestone. The exposed lower part consists mainly of grey silty mudstone with fewer limestone bands and nodules than the underlying Passage Beds. The current Lexicon places the formation in the Gorstian Stage. Historical proposals for a “Birmingham Siltstone Formation” covering roughly the lowest 10 m above the limestone were questioned on definition and age; they do not justify inserting another formation or another 10 m into this local succession.

NCC30: 13.12 m seen. Pale-grey silty shale with scattered ovate nodules and pale/medium-grey fine/medium-grained limestone bands; 13.12 m seen, not full formation thickness.

Lower Elton ash at 2.12 m. A bentonite occurs 2.12 m above the Lower Elton base in the GCR description. This height belongs to that source’s boundary and section.

Lower Elton ash at 3.82 m. A further bentonite is recorded 3.82 m above the same formation base. Neither this nor the lower ash is assigned a WNH identity from height alone.

Independent measured exposures and facies accounts. The following sections overlap the composite already described. Their measurements document local variation and historical scientific exposures rather than extending its total thickness. Names containing “cavern”, “pillars” or “mine” identify study locations and do not indicate a present public route.

Mons Hill Quarry Trench: 0.8 m of upper Nodular Limestone seen. Quarry Trench (Snake Pit), Mons Hill: 0.8 m seen below Upper Quarried. Alternative exposure-specific measured log; never add to NCC totals.

Mons Hill Quarry Trench: 9.7 m of Upper Quarried Limestone. Complete 9.7 m in this source, including former Passage Beds. Basal thin limestone/mudstone with occasional articulated echinoderms, massive grainstone above, upper stromatoporoid pavement and reworked/overturned colonies, then nodular transitional beds.

Mons Hill Quarry Trench: 1.6 m of Lower Elton seen. Lowest 1.6 m exposed in this log; grey-green silty mudstone with ashes. Not full formation thickness.

Mons Hill log total. These three intervals sum to 12.1 m seen in the 2011 quarry-trench section: 0.8 + 9.7 + 1.6 m. Its partial Nodular and Lower Elton intervals flank the locally complete Upper Quarried Limestone. It is a separate exposure-specific total, not a replacement or extension of the 69.10 m NCC composite.

Seven Sisters: Lower Quarried Limestone. The 2011 account describes an approximately 11 m Lower Quarried member here; the pillar exposure begins about 3 m above its base. A microbial reef is about 3 m thick in the central pillars. Its inferred relief, less than 0.5 m in a comparison-based interpretation, is a different measurement from reef thickness. The strong roofing limestone is associated with the top of PS4, while the PS3 flooding interval pinches out over the reef.

Seven Sisters: lower Nodular succession. About 12 m of nodular limestone and silty mudstone overlie the pillar limestone in the 2011 view. The field guide associates this Nodular account with PS5–PS7 and rapid deepening, whereas Ray’s 2010 scheme places PS5 in the uppermost Lower Quarried Limestone. That difference in interval assignment is retained rather than silently reconciled. WNH2 and WNH3 belong to the Lower Quarried pillars, not this overlying interval; the weaker WNH2 ash has been implicated in pillar instability.

2011 NCC account: Lower Quarried variation. The field guide discusses a 9.8–16.2 m range across its local and regional exposures, whereas the current BGS Wren’s Nest range is 12.2–16.2 m. No single universal thickness is implied. Its oncoid observations show an upward change from large irregular forms, less than 70 mm across, to more rounded forms typically 5–10 mm across.

2011 NCC account: incomplete Nodular exposure. The cutting exposed about 23 m out of a total member thickness given as 27.8–31.0 m in that source. These figures differ from both the current BGS local range and the historical NCC composite sum. They describe an incomplete exposure and a particular source definition, not an arithmetic correction to the 1977 log.

Reef Knoll and Ripple Beds: lateral reef and flank facies. Reefs developed on grainstone or packstone with a firm or hard substrate. Flanking beds are commonly 2–6 cm thick and include five prominent ashes. Halysites dominates the basal third of the described reefs, with a more diverse coral assemblage above. Muddy sediment eventually terminated reef growth; the later progression from wackestone through packstone to crinoidal grainstone records shallowing. WNH10 fills approximately 5 cm of hardground relief. These are lateral facies relationships, not five new members or extra thickness to add to the NCC sequence.

Parasequences and relative sea level. Ray and colleagues use PS labels for shallowing-upward packages bounded by flooding surfaces. Their 2010 framework comprises PS0–PS13 in and around the limestone succession; PS14–PS15 appear in the later Lower Elton composite. These are sequence-stratigraphic interpretations, not additional formations or beds to append to the NCC log. The 2010 work revises parts of the earlier 2007 numbering and boundary placement. Progradation means shallower facies advancing across the area; retrogradation records their retreat as accommodation increases.

PS0: sequence-stratigraphic interval. Only part of PS0 is exposed: fossiliferous silty mudstone and limestone nodules lie below the transitional basal limestone succession.

PS1: sequence-stratigraphic interval. The basal, partly exposed PS1 spans the Coalbrookdale–Lower Quarried transition. In 2010 the sequence boundary was moved upwards relative to the 2007 interpretation and was placed within PS1; it is therefore not simply identical to the mapped formation base.

PS2: sequence-stratigraphic interval. Thick oncoid-bearing wackestone contains occasional grainstone lenses and reefs, with WNH2 and WNH3 as ash markers. The flooding interval above PS2 includes about 0.5 m of silty mudstone and nodular wackestone, locally pinching out against reefs. The source reports no reef continuing through that flooding surface.

PS3: sequence-stratigraphic interval. Thick oncoid-bearing wackestones and packstones with abundant reefs form a progradational interval. Reef growth and local sediment accumulation produce lateral variation, so a regional borehole thickness is not assigned to every Wren’s Nest outcrop.

PS4: sequence-stratigraphic interval. This short retrogradational interval near the top of the Lower Quarried Limestone is associated with stromatoporoid pavements. It is retained separately from the underlying PS3 and overlying PS5 rather than being absorbed into a single upper-limestone bed.

PS5: sequence-stratigraphic interval. The uppermost Lower Quarried package includes grainstone with subordinate wackestone, packstone and silty mudstone. It forms part of the rapid deepening succession, with the surface of maximum sediment starvation above in the study’s interpretation.

PS6: sequence-stratigraphic interval. Nodular carbonate mudstone and wackestone alternate with silty mudstone in the lower Nodular Limestone. This retrogradational package culminates at the interpreted maximum-flooding surface, near WNH6. The Seven Sisters Quarry North section supplies key exposure across this interval where the NCC contact is faulted.

PS7: sequence-stratigraphic interval. Bedded packstone and grainstone, including a reef band, record renewed shallowing. A conspicuous flooding interval caps PS7 and includes the thick WNH7 bentonite.

PS8: sequence-stratigraphic interval. A second reef-bearing packstone–grainstone interval lies above the WNH7 ash, approximately 20 cm thick, and about 0.5 m of nodular limestone and silty mudstone. The paired PS7 and PS8 reef bands are distinct features, not one repeated reef horizon.

PS9: sequence-stratigraphic interval. Nodular carbonate mudstone and wackestone pass upwards into packstone and silty mudstone. The youngest patch reefs occur towards its upper part. The study places a surface of forced regression at the PS9–PS10 transition.

PS10: sequence-stratigraphic interval. The prominent WNH10 ash and underlying hardground mark the base of a strongly progradational package; WNH11–WNH14 occur above. The 2010 regional account describes PS10 as about 9.2 m thick, without making that a universal measurement for each local face. Nodular limestone grades through interbedded limestone and mudstone into thicker crinoidal grainstone. The Clematocrinus and Cyphaspis/Exallaspis intervals belong to this part of the succession; the later member boundary lies below the Ripple Beds.

PS11: sequence-stratigraphic interval. Massive crinoidal grainstone reaches about 4.2 m in the Wren’s Nest account. Mud clasts, small channels, rolled corals and stromatoporoids indicate erosion and sediment reworking. Its disappearance in parts of the Walsall comparison area is a lateral regional change, not evidence that it is missing at Wren’s Nest.

PS12: sequence-stratigraphic interval. The Passage Beds are represented by an approximately 2.5 m mudstone–limestone transition in the 2010 Dudley account, rather than the GCR’s 1.30 m definition. A stromatoporoid pavement marks its base and WNH15 lies higher. Later work considers the PS11–PS12 boundary an approximation to the Wenlock–Ludlow boundary, below the top of the lithostratigraphic limestone succession.

PS13: sequence-stratigraphic interval. The lower part of this mud-rich, retrogradational interval records reduced major carbonate production and passage into the Lower Elton Formation. It does not supply a new thickness independent of the overlapping measured sections.

PS14: sequence-stratigraphic interval. The later Dudley composite shows PS14 above PS13 in the Lower Elton Formation. It is a mud-rich retrogradational interval; the schematic alone does not establish a separate precise thickness or a bed-specific fossil list at Wren’s Nest.

PS15: sequence-stratigraphic interval. PS15 follows PS14 in the later composite. Its plotted position is retained, but no unsupported individual thickness, fossil content or extra interval above the NCC’s 13.12 m of Lower Elton is inferred.

Background mudstones: a separate four-sample comparison. Ray and colleagues also analysed four Wren’s Nest silty mudstones that were not associated with bentonite layers. S1–S4 sample different host-rock settings and are neither additional WNH ash numbers nor extra intervals to add to the NCC composite. The study analysed the clay fraction smaller than 2 µm by X-ray diffraction, using oriented slides in air-dried, 550 °C-heated and ethylene-glycol-treated states. Its 22 bentonite samples include the seven Wenlock Edge samples as well as the fifteen local ashes; the four background mudstones are a separate local set.

S1: upper Coalbrookdale background mudstone. Figure 1 places this sample in the PS0 part of the local section. Chlorite, discrete illite and kaolinite occur, together with corrensite, an ordered mixed-layer chlorite/smectite clay with R1 ordering and a 50:50 layer ratio. The ash-characteristic mixed-layer illite/smectite was not detected. The figure supplies its relative position, not a separately measured bed thickness.

S2: upper Lower Quarried Limestone background mudstone. The plotted sample lies by the stromatoporoid-bearing interval near PS3–PS4. Its reported clay assemblage includes chlorite, discrete illite, kaolinite and R1 corrensite with a 50:50 chlorite/smectite layer ratio; mixed-layer illite/smectite was not detected. This sample position does not establish a new formally named bed.

S3: intra-reef background mudstone. This sample came from a mudstone pocket inside a reef in the Nodular Limestone. Chlorite, discrete illite and kaolinite occur, but both mixed-layer illite/smectite and the corrensite found in the other three background samples are absent. Its X-ray diffraction traces appear in Figure 2.

S4: Nodular Limestone background silty mudstone. Figure 1 places S4 in the upper mudstone interval of the Nodular succession, and Figure 2 compares its diffraction traces with those of S3 and bentonite WNH7. S4 contains chlorite, discrete illite, kaolinite and R1 corrensite with a 50:50 chlorite/smectite layer ratio; mixed-layer illite/smectite was not detected.

What the background-clay comparison establishes. All three Figure 2 samples, WNH7, S4 and S3, are from the Nodular Limestone. The paired diffraction traces are vertically offset by 250 counts per second for clarity, so their plotted baselines are not directly comparable mineral abundances. Illite/smectite distinguishes the sampled ashes from these four background mudstones, suggesting that ash was not a major contributor to background sediment in this particular sample set. Corrensite occurs in S1, S2 and S4 but in none of the sampled bentonites. The authors suggest a land-derived supply, possibly from older igneous rocks east of Birmingham. That proposed source remains an interpretation. Shared chlorite, illite and kaolinite could reflect sediment mixing, bioturbation or later alteration; host sediment, organic matter and diagenesis make the clay assemblage a weak stand-alone tool for correlating ash horizons.

Selected volcanic ashes. The 2011 bentonite study records at least 32 ash layers in the Much Wenlock Limestone at Wren’s Nest and two in the immediately underlying Coalbrookdale. WNH1–WNH15 are the 15 layers selected for mineralogical study, not a complete count of ash beds. The seven WE samples in the same table are from Wenlock Edge and are excluded from the local list. In the entries below, “common”, “present” and “rare” reproduce the table’s bold, plain and parenthesised categories. The percentage is illite within ordered mixed-layer illite/smectite, not a whole-rock illite percentage; R1 and R3 describe ordering. These are qualitative microscope-search categories: common grains were immediately apparent, present grains appeared after roughly one to two minutes, and rare grains required more detailed searching. They are not percentage abundances.

WNH1: sampled bentonite. Coalbrookdale Formation; 6 cm thick. Common: apatite; quartz shards; iron hydroxides. Present: magnetite. Rare: biotite. Mixed-layer illite/smectite: R1, 70% illite; other clays: illite, kaolinite. Apatite was selected for ICP-MS analysis.

WNH2: sampled bentonite. Lower Quarried Limestone; 4 cm thick. Common: apatite; biotite; pyrite; quartz shards; iron hydroxides. Present: magnetite; phosphatic ooids. Rare: gypsum. Mixed-layer illite/smectite: R1, 70% illite; other clays: kaolinite. Apatite was selected for ICP-MS analysis.

WNH3: sampled bentonite. Lower Quarried Limestone; 4 cm thick. Common: magnetite; iron hydroxides. Present: apatite. Rare: phosphatic ooids; quartz shards. Mixed-layer illite/smectite: R3, 95% illite; other clays: illite, kaolinite, chlorite. No ICP-MS apatite-analysis asterisk is attached to this sample in Table 1.

WNH4: sampled bentonite. Nodular Limestone; 4 cm thick. Common: phosphatic ooids; pyrite; quartz shards. Rare: apatite; muscovite. Mixed-layer illite/smectite: R3, 95% illite; other clays: illite, kaolinite, chlorite. No ICP-MS apatite-analysis asterisk is attached to this sample in Table 1.

WNH5: sampled bentonite. Nodular Limestone; 4 cm thick. Common: pyrite; gypsum. Present: apatite; biotite; muscovite; quartz shards. Mixed-layer illite/smectite: R3, 95% illite; other clays: illite, kaolinite, chlorite. Apatite was selected for ICP-MS analysis.

WNH6: sampled bentonite. Nodular Limestone; 9 cm thick. Common: pyrite; quartz shards. Present: muscovite; phosphatic ooids. Rare: apatite. Mixed-layer illite/smectite: R3, 95% illite; other clays: illite, kaolinite, chlorite. No ICP-MS apatite-analysis asterisk is attached to this sample in Table 1.

WNH7: sampled bentonite. Nodular Limestone; 20 cm thick. Common: pyrite; iron hydroxides. Present: apatite; biotite; phosphatic ooids; quartz shards; gypsum. Mixed-layer illite/smectite: R1, 80% illite; other clays: illite, kaolinite. Apatite was selected for ICP-MS analysis.

WNH8: sampled bentonite. Nodular Limestone; 15 cm thick. Common: biotite; pyrite; quartz shards; iron hydroxides. Present: apatite; magnetite. Mixed-layer illite/smectite: R3, 95% illite; other clays: illite, kaolinite, chlorite. No ICP-MS apatite-analysis asterisk is attached to this sample in Table 1.

WNH9: sampled bentonite. Nodular Limestone; 8 cm thick. Common: phosphatic ooids; pyrite. Present: apatite; garnet. Rare: magnetite; quartz shards. Mixed-layer illite/smectite: R3, 95% illite; other clays: illite, kaolinite, chlorite. Apatite was selected for ICP-MS analysis.

WNH10: sampled bentonite. Nodular Limestone; 12 cm thick. Common: pyrite; iron hydroxides. Present: apatite; magnetite; phosphatic ooids. Mixed-layer illite/smectite: R3, 95% illite; other clays: illite, kaolinite, chlorite. Apatite was selected for ICP-MS analysis.

WNH11: sampled bentonite. Nodular Limestone; 7 cm thick. Common: phosphatic ooids; iron hydroxides. Present: gypsum. Rare: apatite; biotite. Mixed-layer illite/smectite: R3, 95% illite; other clays: illite, kaolinite, chlorite. No ICP-MS apatite-analysis asterisk is attached to this sample in Table 1.

WNH12: sampled bentonite. Nodular Limestone; 5 cm thick. Common: pyrite; gypsum. Present: apatite. Rare: quartz shards. Mixed-layer illite/smectite: R3, 95% illite; other clays: illite, kaolinite, chlorite. No ICP-MS apatite-analysis asterisk is attached to this sample in Table 1.

WNH13: sampled bentonite. Nodular Limestone; 5 cm thick. Common: apatite; pyrite; iron hydroxides; gypsum. Mixed-layer illite/smectite: R3, 95% illite; other clays: illite, kaolinite, chlorite. Apatite was selected for ICP-MS analysis.

WNH14: sampled bentonite. Nodular Limestone; 4 cm thick. Common: biotite; pyrite; iron hydroxides. Present: muscovite. Rare: quartz shards. Mixed-layer illite/smectite: R3, 95% illite; other clays: illite, kaolinite, chlorite. No ICP-MS apatite-analysis asterisk is attached to this sample in Table 1.

WNH15: sampled bentonite. Passage Beds in the Upper Quarried Limestone; 5 cm thick. Common: apatite; magnetite; phosphatic ooids; quartz shards; iron hydroxides. Present: biotite. Rare: garnet; zircon. Mixed-layer illite/smectite: R1, 75% illite; other clays: illite, kaolinite. Apatite was selected for ICP-MS analysis.

WNH15 zircon: a directly illustrated local mineral sample. Figure 3b shows selected euhedral zircon grains from WNH15 at Lion’s Mouth Quarry, Wren’s Nest; the scale bar represents 1 mm. This is a mineral-grain illustration of the same sampled ash listed above, where zircon is classed as rare. It is not an additional bed or a separately numbered fossil voucher. Figure 3a illustrates apatite, iron hydroxide and gypsum from WE6 at Coates Quarry, Wenlock Edge, and its grain assemblage is not assigned to Lion’s Mouth.

WNH16: separate field-guide marker. The 2011 Mons Hill field-guide log names WNH16 as the higher of two conspicuous ashes near the Upper Quarried–Lower Elton transition; WNH15 is below, in the former Passage Beds. WNH16 is in the Lower Elton and is reported to contain illite/smectite, illite, kaolinite and chlorite, with apatite, biotite and quartz. It is additional to the WNH1–WNH15 journal table: no Table 1 thickness, abundance typography or analytical result is assigned to it.

Apatite chemistry: the separate Table 2 dataset. Eight of the fifteen Wren’s Nest ash samples were analysed for rare-earth elements (REE) and yttrium in selected apatite grains: WNH1, WNH2, WNH5, WNH7, WNH9, WNH10, WNH13 and WNH15. Each analysis used approximately 200 micrograms, or 50 carefully selected grains, avoiding inclusions, dissolution and evidence of reworking. The ICP-MS results describe apatite separates, not whole-rock ash chemistry. Two additional columns, WE2 and WE6, represent Wenlock Edge comparators. The printed WHN9 header is treated as WNH9 within the article’s sample scheme.

Reading the analytical values. Element concentrations and the reported total REE are in parts per million (ppm). The eight discriminators are the europium anomaly Eu/Eu*, the La+Ce+Pr percentage, La/Nd, chondrite-normalised (Ce/Yb)N, Ce/Y, and the percentages represented by La–Nd, Sm–Ho and Er–Lu. In each comparison pair, the first percentage measures variation between the discriminators and the second variation between normalised REE-plus-yttrium concentrations. Chemical resemblance alone does not prove that two ashes are contemporaneous.

Reported analytical relative standard deviations. The table gives: La ±3.3%; Ce ±2.6%; Pr ±4.4%; Nd ±5.0%; Sm ±3.5%; Eu ±2.8%; Gd ±2.8%; Tb ±3.5%; Dy ±4.8%; Ho ±3.5%; Er ±1.4%; Tm ±2.4%; Yb ±3.8%; Lu ±3.1%; Y ±2.4%. These are the table’s analytical RSD values, not bed-thickness errors or independent dating uncertainties.

WNH1: apatite element concentrations. La 353.5; Ce 839.4; Pr 121.7; Nd 564.1; Sm 147.9; Eu 10.3; Gd 176.4; Tb 21.8; Dy 116.7; Ho 20.0; Er 48.4; Tm 4.0; Yb 24.7; Lu 2.3; Y 261.2 ppm. Reported total REE: 2451.0 ppm.

WNH1: discriminators and comparison pairs. Eu/Eu∗ 0.19; La+Ce+Pr % 53.6%; La/Nd 0.63; (Ce/Yb)N 8.8; Ce/Y 3.2; La–Nd 76.6%; Sm–Ho 20.1%; Er–Lu 3.2%. Comparison pairs, in the order defined above: WE2 1.8/2.5%; WE6 1.0/1.7%; SW10 1.7/9.2%; SW11 5.8/11.8%; SW12 6.2/11.1%. WE samples are from Wenlock Edge and SW samples from Gotland; these labels do not identify additional Wren’s Nest beds.

WNH2: apatite element concentrations. La 142.2; Ce 353.3; Pr 54.3; Nd 260.6; Sm 67.0; Eu 6.5; Gd 78.5; Tb 9.6; Dy 53.5; Ho 9.2; Er 22.3; Tm 1.7; Yb 11.7; Lu 1.0; Y 126.8 ppm. Reported total REE: 1071.4 ppm.

WNH2: discriminators and comparison pairs. Eu/Eu∗ 0.27; La+Ce+Pr % 59.2%; La/Nd 0.55; (Ce/Yb)N 7.8; Ce/Y 2.8; La–Nd 75.6%; Sm–Ho 20.9%; Er–Lu 3.4%. Comparison pairs, in the order defined above: WE2 3.2/1.6%; WE6 4.3/7.4%; SW10 3.7/8.0%; SW11 7.6/13.5%; SW12 8.0/12.7%. WE samples are from Wenlock Edge and SW samples from Gotland; these labels do not identify additional Wren’s Nest beds.

WNH5: apatite element concentrations. La 810.3; Ce 1976.0; Pr 275.4; Nd 1260.4; Sm 282.0; Eu 36.7; Gd 302.8; Tb 35.0; Dy 178.8; Ho 30.0; Er 75.2; Tm 6.6; Yb 41.3; Lu 4.1; Y 395.1 ppm. Reported total REE: 5314.6 ppm.

WNH5: discriminators and comparison pairs. Eu/Eu∗ 0.38; La+Ce+Pr % 57.6%; La/Nd 0.64; (Ce/Yb)N 12.4; Ce/Y 5.0; La–Nd 81.3%; Sm–Ho 16.3%; Er–Lu 2.4%. Comparison pairs, in the order defined above: WE2 5.1/8.9%; WE6 4.3/7.7%; SW10 3.6/13.6%; SW11 3.4/5.4%; SW12 3.8/4.6%. WE samples are from Wenlock Edge and SW samples from Gotland; these labels do not identify additional Wren’s Nest beds.

WNH7: apatite element concentrations. La 214.8; Ce 467.5; Pr 65.8; Nd 291.3; Sm 60.0; Eu 8.9; Gd 62.0; Tb 6.6; Dy 35.2; Ho 5.6; Er 12.6; Tm 0.5; Yb 6.7; Lu 0.3; Y 86.0 ppm. Reported total REE: 1323.7 ppm.

WNH7: discriminators and comparison pairs. Eu/Eu∗ 0.40; La+Ce+Pr % 60.4%; La/Nd 0.70; (Ce/Yb)N 18.0; Ce/Y 5.4; La–Nd 84.0%; Sm–Ho 14.4%; Er–Lu 1.6%. Comparison pairs, in the order defined above: WE2 7.6/11.8%; WE6 6.8/10.6%; SW10 6.4/15.7%; SW11 1.7/4.6%; SW12 1.8/4.0%. WE samples are from Wenlock Edge and SW samples from Gotland; these labels do not identify additional Wren’s Nest beds.

WNH9: apatite element concentrations. La 1036.3; Ce 2657.0; Pr 395.1; Nd 1906.4; Sm 444.3; Eu 75.0; Gd 482.3; Tb 56.9; Dy 275.7; Ho 48.6; Er 120.4; Tm 11.9; Yb 67.9; Lu 7.7; Y 608.3 ppm. Reported total REE: 7585.6 ppm.

WNH9: discriminators and comparison pairs. Eu/Eu∗ 0.50; La+Ce+Pr % 53.9%; La/Nd 0.54; (Ce/Yb)N 10.1; Ce/Y 4.4; La–Nd 79.0%; Sm–Ho 18.2%; Er–Lu 2.7%. Comparison pairs, in the order defined above: WE2 3.4/6.4%; WE6 2.9/6.0%; SW10 2.2/12.5%; SW11 5.4/8.2%; SW12 5.8/7.9%. WE samples are from Wenlock Edge and SW samples from Gotland; these labels do not identify additional Wren’s Nest beds.

WNH10: apatite element concentrations. La 233.5; Ce 613.2; Pr 96.2; Nd 463.7; Sm 121.9; Eu 16.3; Gd 140.1; Tb 17.2; Dy 89.5; Ho 14.4; Er 34.0; Tm 2.6; Yb 17.5; Lu 1.6; Y 192.5 ppm. Reported total REE: 1861.8 ppm.

WNH10: discriminators and comparison pairs. Eu/Eu∗ 0.38; La+Ce+Pr % 50.6%; La/Nd 0.50; (Ce/Yb)N 9.1; Ce/Y 3.2; La–Nd 75.5%; Sm–Ho 21.5%; Er–Lu 3.0%. Comparison pairs, in the order defined above: WE2 1.7/3.2%; WE6 1.7/3.4%; SW10 2.9/9.3%; SW11 6.8/12.6%; SW12 7.2/11.9%. WE samples are from Wenlock Edge and SW samples from Gotland; these labels do not identify additional Wren’s Nest beds.

WNH13: apatite element concentrations. La 284.9; Ce 700.4; Pr 105.6; Nd 496.6; Sm 131.1; Eu 18.4; Gd 163.2; Tb 20.4; Dy 110.0; Ho 18.7; Er 46.1; Tm 4.2; Yb 24.9; Lu 2.6; Y 245.0 ppm. Reported total REE: 2127.1 ppm.

WNH13: discriminators and comparison pairs. Eu/Eu∗ 0.38; La+Ce+Pr % 51.3%; La/Nd 0.57; (Ce/Yb)N 7.3; Ce/Y 2.9; La–Nd 74.6%; Sm–Ho 21.7%; Er–Lu 3.7%. Comparison pairs, in the order defined above: WE2 0.3/0.7%; WE6 0.8/1.8%; SW10 3.0/8.2%; SW11 7.5/14.2%; SW12 7.8/13.4%. WE samples are from Wenlock Edge and SW samples from Gotland; these labels do not identify additional Wren’s Nest beds.

WNH15: apatite element concentrations. La 567.4; Ce 1561.6; Pr 256.5; Nd 1296.2; Sm 411.3; Eu 57.6; Gd 505.6; Tb 62.7; Dy 298.0; Ho 46.1; Er 107.6; Tm 9.7; Yb 55.5; Lu 6.1; Y 538.1 ppm. Reported total REE: 5241.8 ppm.

WNH15: discriminators and comparison pairs. Eu/Eu∗ 0.39; La+Ce+Pr % 45.5%; La/Nd 0.44; (Ce/Yb)N 7.3; Ce/Y 2.9; La–Nd 70.2%; Sm–Ho 26.4%; Er–Lu 3.4%. Comparison pairs, in the order defined above: WE2 4.0/6.4%; WE6 4.3/7.3%; SW10 6.8/12.2%; SW11 10.9/17.4%; SW12 11.2/16.6%. WE samples are from Wenlock Edge and SW samples from Gotland; these labels do not identify additional Wren’s Nest beds.

WNH13 correlated with WE2 and WE6. The study combines stratigraphic position with apatite chemistry to identify WNH13, WE2 at Harley Hill and WE6 at Coates Quarry as the same ash horizon. The comparison pairs are WNH13–WE2 0.3/0.7%, WNH13–WE6 0.8/1.8% and WE2–WE6 0.9/1.4%. All three REE-plus-yttrium comparisons are below 2%, compatible with within-horizon apatite variation. Their position in the PS10 interval supports the tie; small clay and sand-grade mineral differences do not invalidate it because alteration, deposition and reworking can differ. WE2 and WE6 remain geographically separate samples of the correlated horizon.

Why WNH1 is not correlated with WE6. WNH1 and WE6 are also chemically similar, with a 1.0/1.7% comparison pair. The authors reject a same-horizon correlation because WNH1 lies in Coalbrookdale strata assigned to the upper lundgreni Biozone, whereas WE6 belongs to Much Wenlock Limestone assigned to the ludensis Biozone in their framework. The example demonstrates why a chemical match without independent age control can be misleading.

WNH7 and the Gotland comparison. The WNH7–SW11 and WNH7–SW12 pairs are 1.7/4.6% and 1.8/4.0%; the authors do not regard them as analytically indistinguishable. Differences in procedure and instrumentation add uncertainty. WNH7 is a 20 cm ash preserved at a flooding surface and might combine more than one fall, potentially including equivalents of the Gotland ashes, which are separated there by 0.16 m. A shared source region is possible, but neither a single shared eruption nor an exact one-to-one correlation is established. SW10 is a poorer match than the simplified light-versus-heavy REE plot alone suggests.

What the chemistry suggests about ash sources. The authors interpret the apatite REE patterns as volcanic and most compositions as closest to a granodioritic source; WNH5 and WNH7 trend towards gabbroic compositions. The local Eu/Eu* values of 0.19–0.50 indicate negative europium anomalies, interpreted as evidence for substantial earlier plagioclase fractionation. WNH15 is comparatively low in light REE and enriched in middle REE and had no identified equivalent in the 2011 comparison set. These are source-composition interpretations, not identifications of an exposed volcano at Wren’s Nest.

Distance and preservation limits. The study contrasts Midland Platform phenocrysts about 0.5–1.0 mm long with Gotland grains about 0.02–0.2 mm. Its transport-distance estimates favour a more proximal Midland Platform source if the ashes share a source region. The authors nevertheless caution that compaction, bioturbation and depositional energy alter preserved ash thickness. WNH7’s thickness and the much thinner SW11 and SW12 layers are therefore supporting comparisons, not a precise volcanic-distance measurement or proof of one eruption.

Fossil preservation and exceptional burial. Disarticulated skeletal debris, complete colonies and rare rapidly buried assemblages represent different histories. A named fossil-bearing interval is not automatically a formal lithostratigraphic bed, and a published density or articulated specimen occurrence is not an estimate of what a visitor can expect to find. The following descriptions retain the geographic and stratigraphic limits of the published text.

Five interpreted faunal–lithological associations. Ray and Thomas numbered recurring facies, not formal units: 1, agitated oncoidal/crinoidal limestones with stromatoporoids; 2, echinoderm-rich storm deposits on firm substrates; 3, reef-flank to muddy brachiopod/trilobite settings affected by storms; 4, coral–stromatoporoid reefs and microbial mounds; 5, deeper muddy nodular facies with sparse fossils. Their sequence runs broadly from shallower to deeper conditions and does not reconstruct the unseen survey-matrix cells.

The Clematocrinus Bed. The described limestone is approximately 5 cm thick, with a basal shell packstone around 1 cm thick, and is overlain by about 5 cm of mud. A local patch of articulated crinoids reached roughly 16 individuals per square metre. A 0.5 cm ash was observed at one location; that observation does not establish a volcanic cause for every burial event in the interval.

Clematocrinus Bed associates. Outcrop associates include partial Gissocrinus, favositid/heliolitid corals, Platyceras, ramose bryozoans and six brachiopod species including Orbiculoidea. Dalmanites and Placocystites are possible museum-inferred additions, not observed alongside Clematocrinus retiarius on the same slabs.

The Cyphaspis/Exallaspis beds. An approximately 1 m interval begins about 0.5 m above the youngest reefs and contains limestone beds 1–5 cm thick interbedded with mud. It includes the Clematocrinus Bed and preserves a distinctive, generally low-abundance assemblage rather than a uniform fauna in every layer.

Echinoderm Interval 1. In the 2007 framework this includes the uppermost Nodular Limestone and approximately the basal 0.7 m of Upper Quarried Limestone. A separate similar interval, approximately 0.4 m thick, occurs at the top of Association 2, near the transition from bedded to massive crinoidal grainstone. The two occurrences are not one continuous basal interval. Beds are commonly thicker than 7 cm and lack the blue-grey mud caps of Interval 2.

Echinoderm Interval 2. Approximately 0.7–2.6 m above the Upper Quarried base in that framework, limestone beds average around 5 cm thick and alternate with silty mud, commonly capped by blue-grey mud. Favosites and bryozoans occur in the described assemblage. These positions use the source’s member boundary, which should not be silently substituted into a different log.

Interval 1 echinoderms. Recorded: Lepidactis wenlocki; Carpocrinus, Crotalocrinus, Dimerocrinites, Eucalyptocrinites, Gissocrinus, Mariacrinus, Marsupiocrinus, Periechocrinites, Protaxocrinus, Sagenocrinites; and Glansicystis.

Interval 2 echinoderms. The source excludes Protaxocrinus and Glansicystis from the shared Interval 1 fauna and adds Lepidasterella, Botryocrinus, Enallocrinus, Melocrinites, Taxocrinus, Apiocystites, Lepadocrinus, Pseudocrinus and Staurocystites.

Stromatoporoid pavements. Paired horizons contain small hemispherical to subspherical colonies, reported at approximately 50–120 per square metre and 1.5–5 cm across in the study. These local historical observations describe growth surfaces and their preservation, not a reserve-wide abundance or a collecting target.

Oncoid-bearing facies. Oncoids, coated carbonate grains rather than necessarily separate fossil bodies, are commonly 5–10 mm across in the described agitated limestone facies. Lower Quarried studies also document much larger irregular forms low in the succession, so neither one size nor one shape characterises all beds.

Historical museum slabs. The 2007 study discusses 56 museum specimens representing 21 genera correlated across Dudley, alongside 155 specimens representing 38 genera in newer collections. These are study sample counts with uneven historical provenance. They are not a modern exact-reserve species total or independent evidence that each taxon occurs in every named Wren’s Nest horizon.

Documented faunas by exposure and facies. The following source-specific records supplement the measured intervals. Generic names are retained as published, rather than being presented as newly revised identifications. A record in one facies or museum study does not establish an occurrence in every bed, and historical Dudley totals do not form a complete modern reserve checklist.

Lower part of Lower Quarried. Antirhynchonella, Atrypa, Eospirifer, Gypidula, Howellella, Strophonella. The lower limestone horizons contain these published records; no individual voucher or NCC interval number is supplied for each occurrence.

Lower part of Lower Quarried. Paleofavosites, Stelliporella, Ketophyllum. The lower limestone horizons contain these published records; no individual voucher or NCC interval number is supplied for each occurrence. These are scientific occurrence records, not a prediction of loose finds.

Upper Nodular. Favosites, Amphistrophia, Atrypa, Coolinia, Eospirifer, Gypidula, Meristina, Strophonella, Calymene, Dalmanites. The GCR records fossils more commonly in the upper two-thirds of the member. Corals, brachiopods and fragmentary trilobites form a mixed assemblage.

Upper Quarried. Atrypa, Strophonella, Calymene, Acervularia. The GCR describes these fossils as comparatively uncommon in its Upper Quarried account; stromatoporoid-rich surfaces are described separately.

Lower Elton in the 1977 section. Amphistrophia, Atrypa, Eospirifer, Leptaena, Leptostrophia, Meristina, Protochonetes, Strophonella. These brachiopods were recorded from Lower Elton strata exposed during the 1977 excavations. They are exact-local evidence, unlike some graptolites labelled only “Dudley”.

Local reef framework, facies not single bed. Favosites, Heliolites, Syringopora, Halysites, Acervularia, Dokophyllum, Hallopora, Fistulipora, Girvanella, Wetheredella, Rothpletzella, Alveolites, Thecia, Labechia, Fenestella. The GCR distinguishes skeletal framework builders and encrusting or binding organisms. These facies associations are not a list for one bed. Older stromatoporoid names in that account are not silently reassigned to the revised species below.

Wren fauna, no exact bed supplied by GCR. Acroculia, Poleumita, Goniophora, Pteronitella, Dawsonoceras. These molluscs are recorded in the locality account without a defensible assignment here to an individual bed.

Uppermost Coalbrookdale in NCC. Amphistrophia, Atrypa, Dolerorthis, Eoplectodonta, Eospirifer, Howellella, Leptaena, Resserella. The 2011 field guide gives these occurrences for the uppermost Coalbrookdale exposed in the NCC area, rather than importing the fauna of the whole regional formation.

Uppermost Coalbrookdale in NCC. Periechocrinites, Calymene, Ananaspis?, Dalmanites, Encrinurus. The 2011 field guide gives these occurrences for the uppermost Coalbrookdale exposed in the NCC area, rather than importing the fauna of the whole regional formation. The question mark in Ananaspis? preserves the original uncertainty; bryozoans and solitary rugose corals are also reported.

Lower Quarried oncoidal/microbial facies. Atrypa, Rhynchotreta, Girvanella, Rothpletzella, Wetheredella. These organisms accompany relatively low-diversity skeletal assemblages and microbial mounds; other Lower Quarried beds differ.

Lower NCC Nodular quieter-water intervals. Atrypa, Leptaena. The fauna is sparse and predominantly disarticulated, with fragmentary bryozoans, trilobites, solitary rugose corals and favositids also noted.

Higher NCC Nodular intervals. Amphistrophia, Leptaena, Strophonella, Acaste, Calymene, Dalmanites, Proetus, Warburgella. Bivalves, bryozoans, crinoid debris, tentaculitids and reef growth also occur in the higher intervals.

Mons Hill uppermost Nodular/UQL thin beds. Favosites, Halysites, Syringopora, Thamnopora, Anastrophia, Atrypa, Eospirifer, Homoeospira, Leptaena, Microsphaeridiorhynchus, Resserella, Rhynchotreta, Acaste, Calymene, Dalmanites, Warburgella. These are the ordinary, generally sparse occurrences in the thin-bedded interval; the occasional exceptional-burial deposits have a different preservation record.

Mons Hill occasional obrution deposits. Lepidactis wenlocki, Lepidasterella. These records concern occasional rapid-burial deposits at Mons Hill. Articulated echinoderms are exceptional; ordinary loose material is more often disarticulated stems, plates or ossicles.

Mons Hill occasional obrution deposits. Botryocrinus, Carpocrinus, Crotalocrinus, Dimerocrinites, Enallocrinus, Eucalyptocrinites, Gissocrinus, Mariacrinus, Marsupiocrinus, Melocrinites, Periechocrinites, Protaxocrinus, Sagenocrinites, Taxocrinus. These records concern occasional rapid-burial deposits at Mons Hill. Articulated echinoderms are exceptional; ordinary loose material is more often disarticulated stems, plates or ossicles.

Mons Hill occasional obrution deposits. Apiocystites, Glansicystis, Lepadocrinus, Pseudocrinus, Staurocystites. These records concern occasional rapid-burial deposits at Mons Hill. Articulated echinoderms are exceptional; ordinary loose material is more often disarticulated stems, plates or ossicles.

Reef Knoll framework. Halysites, Favosites, Heliolites, Syringopora, Thamnopora, Thecia. The described reefs begin on firm or hard substrate. Halysites dominates their basal third, with a more varied coral assemblage above.

Reef Knoll flank beds. Amphistrophia, Leptaena, Strophonella, Crotalocrinites, Gissocrinus, Herpetocrinus, Sagenocrinites, Temnocrinus. Disarticulated crinoids, ramose and fenestrate bryozoans, and tentaculitids accompany these recorded taxa in reef-flanking strata.

Reef/inter-reef interval. Acaste, Balizoma, Calymene, Cybantyx, Dalmanites, Encrinurus, Proetus, Warburgella, Acidaspis, Ceratocephala, Dudleyaspis, Acanthopyge, Platylichas, Dicranopeltis, Richterarges. The field guide records these trilobites from the reef and inter-reef interval; the odontopleurid and lichid genera in the latter part of its list are rare records.

Reef-flanking carbonate mudstone. Diplocraterion, Thalassinoides, Oikobesalon citrimorion. These are trace fossils, distinct from the body-fossil list. Oikobesalon citrimorion is specifically described as rare.

Mud-rich interval above reefs. Cyphaspis, Clematocrinus retiarius. The low-abundance, low-diversity fauna includes exceptionally preserved trilobites and a crinoid adapted to a soft substrate.

Ripple Beds pockets beneath thin mud in ripple troughs. Carpocrinus, Dimerocrinites, Gissocrinus, Periechocrinites, Glansicystis, Calymene, Warburgella. The field guide records rare articulated specimens in small pockets protected beneath mud in ripple troughs; these observations do not imply abundant complete fossils throughout the Ripple Beds.

Historical exposure names. Cutler, Oliver and Reid’s 1990 geological trail and the GCR map identify the following eleven stops. This historical numbering differs from the later official eleven-geopoint trail and from the four themed walks. The names below provide context for geological observations; they are not current access directions or assurances that a face remains clear.

1990 stop 1: Mons Hill. The Upper Quarried Limestone and Lower Elton transition was described here; the historical stop does not establish the present extent of clearance.

1990 stop 2: NCC cutting. The 1977 cutting traversed the Nodular succession, with adjacent exposures continuing into the Lower Quarried Limestone and Coalbrookdale.

1990 stop 3: West bedding plane. The exposed Nodular Limestone bedding plane is cut by calcite-filled fractures.

1990 stop 4: Quarry Marsh. Patch reefs and inter-reef strata occur with fallen blocks of mixed origins. A loose block is not securely assigned to a particular in-place bed simply by its position on the ground.

1990 stop 5: Fossil Trench/Ripple Beds. The older trail places the Ripple Beds in the upper Nodular succession. Later measured work places the Upper Quarried base approximately 0.5 m below the mega-rippled grainstone, so the source-specific member boundary matters.

1990 stop 6: Meadow Road/Lion’s Mouth/Snake Pit. This historical cluster of names covers channelled Upper Quarried beds and reverse-faulted Lower Elton strata. The individual scientific sections are not interchangeable location labels.

1990 stop 7: Cedar Road southern tip. The southern tip illustrates axial-fault relationships and local reddening of limestone associated with lime burning.

1990 stop 8: Panorama. The panorama gives regional landscape context. Surrounding Carboniferous rocks are not additional beds in the measured Silurian composite.

1990 stop 9: Seven Sisters. Historical observations concern the Lower Quarried pillars, roof limestone and ash layers. The underground workings are not a public collecting route.

1990 stop 10: Quarry top. Nodular strata and the structure of the inlier core were illustrated at the quarry-top stop.

1990 stop 11: Former Caves public house viewpoint. The former public-house viewpoint was used to explain axial-fault relationships. The geological record does not establish the current operation of that business.

Oliver’s western-flank petrography. Oliver examined approximately 300 hand specimens and 200 thin sections from ten sampling points, mainly on the western outcrop. His six lithological classes describe textures and fossil components that recur through the succession; they are not six successive beds or six formal members. The interpretations below are his facies interpretation, with biological disturbance and the nature of the original skeletons also affecting sorting and grain shape.

Petrological class A. Micrite and skeletal micrite are matrix-dominated, with few fragments larger than 0.1 mm and occasional larger whole or broken fossils. Oliver found this class mainly in the Lower Quarried and Nodular limestones and interpreted relatively quiet deposition, with fine debris produced by benthic activity and/or transported from nearby areas.

Petrological class B. Laminated micritic and skeletal limestones include micrite-rich and spar-cemented varieties, with cross-bedding and graded bedding in some examples. This mainly platy Nodular Limestone class was interpreted as reflecting stronger current or wave sorting, transport and subsequent biological disturbance.

Petrological class C. Bioclastic micritic limestone has variable texture and grain size, including a common fragment fraction around 200 micrometres, generally without pronounced lineation or lamination. Most samples came from the Nodular Limestone, with some from the Lower Quarried. Oliver inferred comparatively quiet deposition but sufficient disturbance to break and disarticulate shells.

Petrological class D. Biomicrudite contains larger and more varied fossil fragments than class C, including encrusting forms. It occurs in the Lower Quarried and Nodular limestones and was interpreted as a quiet-water deposit with abundant organic activity.

Petrological class E. Laminated biomicrudite and biosparrudite are relatively cleanly washed compared with muddier classes. Samples mainly came from the upper Nodular and Upper Quarried limestones. Oliver inferred relatively energetic conditions alternating with quieter periods and transport between neighbouring environments.

Petrological class F. Biolithite is dominated by colonial organisms, with variable sediment around the colonies. Most examples came from bioherms in the Lower Quarried and Nodular limestones. The class includes growth in comparatively quiet water as well as more agitated conditions and cannot be reduced to a single water-energy setting.

Western-flank field lithology 1. Lower Quarried bioherms were reported as reaching 10 ft (about 3.05 m) thick in the western-flank study. This is local reef thickness, not a measured NCC interval.

Western-flank field lithology 2. Lower Quarried biostromes were approximately 1 ft (0.30 m) thick in the same account.

Western-flank field lithology 3. Bedded Lower Quarried limestone was commonly 3–6 in thick, occasionally 1 ft, with intervening shale around 1 in. Individual bed thickness varied laterally.

Western-flank field lithology 4. Nodular Limestone bioherms in the sampled exposures were generally smaller than the Lower Quarried examples.

Western-flank field lithology 5. Alternating Nodular Limestone beds were commonly 2–4 in thick, with shale layers generally thinner than the limestone.

Western-flank field lithology 6. Impersistent nodules reached about 6 in thick and ranged from 2 in to 1 ft long, surrounded by shale intervals up to 4 in thick.

Western-flank field lithology 7. Occasional laterally persistent limestone bands in the Nodular succession reached about 2 ft 6 in (0.76 m).

Western-flank field lithology 8. Upper Quarried limestone beds were commonly 2–5 in thick, separated by shale layers up to 2 in.

Western-flank field lithology 9. Thicker Upper Quarried beds reached about 1 ft, with thin shale partings.

Western-flank field lithology 10. The Upper Quarried account also cites bioherms up to 3 ft (about 0.91 m) thick, following Butler’s earlier observations.

Stromatoporoid study: what was actually counted. Kershaw, Da Silva and Sendino’s monograph, dated 2021 and published online in January 2022, separates Wren’s Nest material from its wider British sample. The Wren’s Nest columns contain 85 specimens: 36 in place, 24 loose and 25 museum specimens. There are eleven named species rows and one row of unidentified stromatoporoids. The counts below preserve those three sample categories; neither the regional total nor this selected material measures present reserve abundance. Blank original cells are represented as zero counted in that category, not proof of biological absence.

Labechia conferta. In-place specimens: 0; loose specimens: 2; museum specimens: 3; total: 5.

Ecclimadictyon macrotuberculatum. In-place specimens: 2; loose specimens: 0; museum specimens: 2; total: 4.

Ecclimadictyon astrolaxum. In-place specimens: 0; loose specimens: 0; museum specimens: 1; total: 1.

Petridiostroma simplex. In-place specimens: 1; loose specimens: 0; museum specimens: 10; total: 11.

Actinostromella vaiverensis. In-place specimens: 10; loose specimens: 2; museum specimens: 0; total: 12.

Araneosustroma fistulosum. In-place specimens: 1; loose specimens: 2; museum specimens: 0; total: 3.

Densastroma pexisum. In-place specimens: 7; loose specimens: 5; museum specimens: 2; total: 14.

Plectostroma intertextum. In-place specimens: 1; loose specimens: 0; museum specimens: 1; total: 2.

Eostromatopora impexa. In-place specimens: 0; loose specimens: 0; museum specimens: 1; total: 1.

Syringostromella borealis. In-place specimens: 12; loose specimens: 13; museum specimens: 3; total: 28.

Parallelostroma typicum. In-place specimens: 1; loose specimens: 0; museum specimens: 0; total: 1.

Unidentified stromatoporoids. In-place specimens: 1; loose specimens: 0; museum specimens: 2; total: 3.

Reefs A–C and the upper Lower Quarried pavement. The letters A, B and C refer to photographed Nodular Limestone reefs in the monograph’s figure, not formal beds. Its inset separately identifies the upper of two Lower Quarried stromatoporoid-rich biostromes. Syringostromella borealis is concentrated on a horizon in this pavement, interpreted as settlement during reduced sedimentation. Several other coral-rich reefs yielded no observed stromatoporoids, and no in-place examples were confirmed in the sampled bedded Nodular limestones. Those are sampling observations, not a claim that the organisms are absent everywhere in those facies.

Reef A. Recorded stromatoporoids: Actinostromella vaiverensis, Araneosustroma fistulosum, Densastroma pexisum, Plectostroma intertextum, Syringostromella borealis.

Reef B. Recorded stromatoporoids: Ecclimadictyon macrotuberculatum, Actinostromella vaiverensis, Densastroma pexisum.

Reef C. Recorded stromatoporoids: Ecclimadictyon macrotuberculatum, Actinostromella vaiverensis, Densastroma pexisum, Parallelostroma typicum.

Upper Lower Quarried pavement. Recorded stromatoporoids: Petridiostroma simplex, Densastroma pexisum, Syringostromella borealis.

A caption inconsistency. The introductory wording of the monograph’s Text-figure 10 mentions Upper Quarried Limestone, but its detailed panel caption places A in the upper Lower Quarried Limestone and B–D in the Nodular Member. The panel-specific placements are retained here together with that conflict; the photographs are not used to create an additional Upper Quarried stromatoporoid horizon.

Specimens and type material. The catalogue records below preserve the specimen identifiers and locality limits of the source. A figured or studied specimen is not necessarily a type. Historical names are retained where a modern taxonomic revision has not been established, and prepared sections of one specimen are not counted as extra individuals. The expanded register also includes the separately identified 2018 conodont elements and studied rock samples. These records supplement, rather than exhaust, the locality’s museum holdings.

Zl 1710. Acaste downingiae. The BGS catalogue explicitly gives Wren’s Nest, Dudley, Much Wenlock Limestone and Homerian, but no member or bed. Its type-status field says “Not Designated a Type”. The catalogue name is reproduced without implying an independent modern taxonomic revision.

Zl 1493. Acervularia ananas. The BGS catalogue explicitly gives Wren’s Nest, Dudley, Much Wenlock Limestone and Homerian, but no member or bed. Its type-status field says “Not Designated a Type”. The catalogue name is reproduced without implying an independent modern taxonomic revision.

Zl 1494. Acervularia ananas. The BGS catalogue explicitly gives Wren’s Nest, Dudley, Much Wenlock Limestone and Homerian, but no member or bed. Its type-status field says “Not Designated a Type”. The catalogue name is reproduced without implying an independent modern taxonomic revision.

GSM 36335. Acidaspis brighti. The BGS catalogue explicitly gives Wren’s Nest, Dudley, Much Wenlock Limestone and Homerian, but no member or bed. Its type-status field says “Not Designated a Type”. The catalogue name is reproduced without implying an independent modern taxonomic revision.

Zl 1545. Alveolites grayi. The BGS catalogue explicitly gives Wren’s Nest, Dudley, Much Wenlock Limestone and Homerian, but no member or bed. Its type-status field says “Not Designated a Type”. The catalogue name is reproduced without implying an independent modern taxonomic revision.

GSM 53769. Coenites repens. The BGS catalogue explicitly gives Wren’s Nest, Dudley, with “Wenlock Epoch” and “WENLOCK ROCKS (UNDIFFERENTIATED)”. It does not specify a formation, member, bed or finer stage. Its type-status field says “Not Designated a Type”. The catalogue name is reproduced without implying an independent modern taxonomic revision.

GSM 53770. Coenites repens. The BGS catalogue explicitly gives Wren’s Nest, Dudley, with “Wenlock Epoch” and “WENLOCK ROCKS (UNDIFFERENTIATED)”. It does not specify a formation, member, bed or finer stage. Its type-status field says “Not Designated a Type”. The catalogue name is reproduced without implying an independent modern taxonomic revision.

GSM 53771. Coenites repens. The BGS catalogue explicitly gives Wren’s Nest, Dudley, with “Wenlock Epoch” and “WENLOCK ROCKS (UNDIFFERENTIATED)”. It does not specify a formation, member, bed or finer stage. Its type-status field says “Not Designated a Type”. The catalogue name is reproduced without implying an independent modern taxonomic revision.

Zl 1504. Halysites catenularia. The BGS catalogue explicitly gives Wren’s Nest, Dudley, Much Wenlock Limestone and Homerian, but no member or bed. Its type-status field says “Not Designated a Type”. The catalogue name is reproduced without implying an independent modern taxonomic revision.

CAMSM X.50347.187. Labechia conferta. Wren’s Nest, MWL. Figured/studied material; no type designation established here. Thin sections show stout pillars and curved dissepiments; no reef size from elsewhere transferred.

CAMSM X.50347.225. Ecclimadictyon macrotuberculatum. Wren’s Nest, MWL. Figured/studied material; no type designation established here. Interdigitation of skeleton and sediment, with incorporated brachiopods/tabulates/bryozoans/crinoids.

NMW 93-117. Petridiostroma simplex. Wren’s Nest, MWL. Figured/studied material; no type designation established here. Domical non-enveloping growth with concave base. Fig17D is Wenlock Edge and excluded.

CAMSM X.50347.188. Actinostromella vaiverensis. Wren’s Nest, MWL. Figured/studied material; no type designation established here. Irregular shelly substrate.

CAMSM X.50347.243. Actinostromella vaiverensis. Wren’s Nest, MWL; loose sample. Figured/studied material; no type designation established here. Fractures described by authors; no secure bed.

CAMSM X.50347.208. Densastroma pexisum. Wren’s Nest, LQL stromatoporoid pavement. Figured/studied material; no type designation established here. Grew on orthoconic nautiloid; banding not demonstrably annual.

CAMSM X.50347.193. Syringostromella borealis. Wren’s Nest, MWL. Figured/studied material; no type designation established here. Grew on orthoconic nautiloid; non-enveloping dome.

CAMSM X.50347.204. Syringostromella borealis and Petridiostroma simplex. Wren’s Nest, upper LQL pavement. Figured/studied material; no type designation established here. Favositid substrate, then Petridiostroma simplex, then Syringostromella borealis.

CAMSM X.50347.186. Syringostromella borealis. Wren’s Nest, MWL. Figured/studied material; no type designation established here. Bioclastic micritic substrate; possible earlier partial lithification.

CAMSM X.50347.204.2. Syringostromella borealis and Petridiostroma simplex. Wren’s Nest, upper LQL pavement. Figured/studied material; no type designation established here. Thin-section derivative of specimen 204, not an independent additional specimen. Small spiral symbiont tube confined to lower Syringostromella borealis.

CAMSM X.50347.198. Syringostromella borealis and Petridiostroma simplex. Wren’s Nest, LQL pavement. Figured/studied material; no type designation established here. Competing/intergrown stromatoporoids on bryozoan fragment; spiral tubes in Syringostromella borealis.

BM(NH) D.33926. Favositella anolotichoides. Upper Middle Nodular Beds, exposure by lime-kiln on SW Wren’s Nest. Holotype designated in 1966. D.33926a and D.33926c plate labels are prepared portions; original encrusting colony 40 × 27 mm, 4–5 mm thick on Orthoceras-labelled shell. Original generic name retained; modern synonymy not independently resolved.

Additional views of the Oakley holotype. Plate 5 figures 2 and 5 illustrate tangential sections of BM(NH) D.33926, including the D.33926c prepared portion and granules. Plate 7 figures 3 and 4 show vertical sections of prepared portions D.33926d and D.33926b with characteristic and vesicular mesopores. Plate 9 figure 3 shows the colony’s celluliferous surface. These are further views or prepared parts of the same holotype, not extra types. Other panels labelled only Dudley or Gotland are not assigned to Wren’s Nest.

BM(NH) D.36324. Favositella anolotichoides; a paratype designated by Oakley in 1966, explicitly from the same south-western Wren’s Nest type locality as D.33926. It is one of the eight local paratypes; other specimens with less precise provenance are not transferred to that locality.

BM(NH) D.36326. Favositella anolotichoides; a paratype designated by Oakley in 1966, explicitly from the same south-western Wren’s Nest type locality as D.33926. It is one of the eight local paratypes; other specimens with less precise provenance are not transferred to that locality.

BM(NH) D.36327. Favositella anolotichoides; a paratype designated by Oakley in 1966, explicitly from the same south-western Wren’s Nest type locality as D.33926. It is one of the eight local paratypes; other specimens with less precise provenance are not transferred to that locality.

BM(NH) D.36328. Favositella anolotichoides; a paratype designated by Oakley in 1966, explicitly from the same south-western Wren’s Nest type locality as D.33926. It is one of the eight local paratypes; other specimens with less precise provenance are not transferred to that locality.

BM(NH) D.36329. Favositella anolotichoides; a paratype designated by Oakley in 1966, explicitly from the same south-western Wren’s Nest type locality as D.33926. It is one of the eight local paratypes; other specimens with less precise provenance are not transferred to that locality.

BM(NH) D.36330. Favositella anolotichoides; a paratype designated by Oakley in 1966, explicitly from the same south-western Wren’s Nest type locality as D.33926. It is one of the eight local paratypes; other specimens with less precise provenance are not transferred to that locality.

BM(NH) D.36331. Favositella anolotichoides; a paratype designated by Oakley in 1966, explicitly from the same south-western Wren’s Nest type locality as D.33926. It is one of the eight local paratypes; other specimens with less precise provenance are not transferred to that locality.

BM(NH) D.36332. Favositella anolotichoides; a paratype designated by Oakley in 1966, explicitly from the same south-western Wren’s Nest type locality as D.33926. It is one of the eight local paratypes; other specimens with less precise provenance are not transferred to that locality.

BM(NH) D.36339. Favositella interpuncta forma intermedia. Wren’s Nest, Middle Nodular Beds. Figured/studied material; no type designation established here. Colony encrusting ramose coral. Historical forma name; not a modern species validation.

BU4477. Clematocrinus retiarius. Wren’s Nest where caption states. Figured/studied material; no type designation established here. This is a caption/text-supported occurrence; the actual 2007 illustration has not been independently inspected here. No additional morphological detail is inferred from it.

BU4478. Cyphaspis elachopos. Wren’s Nest where caption states. Figured/studied material; no type designation established here. This is a caption/text-supported occurrence; the actual 2007 illustration has not been independently inspected here. No additional morphological detail is inferred from it.

BU4479. Storm-winnowed, time-averaged bedding-plane assemblage. Upper Nodular Beds, Wren’s Nest; Association 3 in the caption. Figured/studied material; no type designation established here. This is a caption/text-supported occurrence; the actual 2007 illustration has not been independently inspected here. No additional morphological detail is inferred from it.

Type-locality limits. Oakley’s holotype BM(NH) D.33926 and eight explicitly local paratypes support a precise Wren’s Nest type locality for the historical name Favositella anolotichoides. By contrast, the GCR illustration of Calymene blumenbachii SM A3225 is labelled only Dudley, and the monograph gives conflicting Dudley/Wenlock Edge provenance for NHMUK PI P6145, historically the type of Labechia scabiosa. Neither is counted here as a proven exact-Wren type or voucher.

2018 Lion’s Mouth conodont evidence. Jarochowska and colleagues’ paper, published online in September 2017 and in the 2018 volume, explicitly assigns twenty figured conodont vouchers in five named taxa to Lion’s Mouth Cavern at Wren’s Nest. The methods place illustrated specimens in GeoZentrum Nordbayern, Erlangen. The following are caption-supported identifications and specimen/sample links; the actual SEM images have not been independently recovered. They are not type designations, whole-animal counts or a complete local fauna. The caption’s scale bar is 500 micrometres.

Ozarkodina bohemica longa. EJ-17-LMC4-01 (sample LMC4, panel E); EJ-17-LMC4-02 (sample LMC4, panel F); EJ-17-LMC3-01 (sample LMC3, panel G). These exact-local assignments come from the Figure 6 caption; no additional morphological or bed-level inference is made.

Oulodus excavatus. EJ-17-LMC4-03 (sample LMC4, panel J); EJ-17-LMC4-04 (sample LMC4, panel K); EJ-17-LMC4-05 (sample LMC4, panel L); EJ-17-LMC2-01 (sample LMC2, panel N); EJ-17-LMC2-02 (sample LMC2, panel O). These exact-local assignments come from the Figure 6 caption; no additional morphological or bed-level inference is made.

Wurmiella excavata. EJ-17-LMC4-06 (sample LMC4, panel P); EJ-17-LMC4-07 (sample LMC4, panel Q); EJ-17-LMC4-08 (sample LMC4, panel S); EJ-17-LMC1-01 (sample LMC1, panel T); EJ-17-LMC1-02 (sample LMC1, panel U). These exact-local assignments come from the Figure 6 caption; no additional morphological or bed-level inference is made.

Ozarkodina confluens. EJ-17-LMC4-09 (sample LMC4, panel Y). These exact-local assignments come from the Figure 6 caption; no additional morphological or bed-level inference is made.

Panderodus greenlandensis. EJ-17-LMC1-03 (sample LMC1, panel Z); EJ-17-LMC4-10 (sample LMC4, panel AA); EJ-17-LMC4-11 (sample LMC4, panel AB); EJ-17-LMC4-12 (sample LMC4, panel AC); EJ-17-LMC3-02 (sample LMC3, panel AD); EJ-17-LMC3-03 (sample LMC3, panel AE). These exact-local assignments come from the Figure 6 caption; no additional morphological or bed-level inference is made.

LMC3 thin section in the 2018 study. Figure 5K is captioned as crinoidal packstone containing phosphatised crinoid debris from sample LMC3 at Lion’s Mouth Cavern, with a 500 micrometre scale bar. The associated text places this phosphatisation in the Passage Beds (PS12) and interprets it as evidence of reduced sediment accumulation. This caption-supported sample has not been visually re-examined here. LMC3 is not silently equated with the later TS16 thin-section label or a similarly numbered isotope sample.

Other panels and pooled counts. The same paper’s Wren’s Nest Tunnel Portal section is at Castle Mill Basin on Castle Hill and is separate from Lion’s Mouth. Figure 6 also contains Whitman’s Hill and Bruff Business Park specimens, and Figure 7 concerns Whitman’s Hill; those panels are not imported into this local list. The study’s analysed matrix of 42 samples, 1,794 identifiable conodont elements and fifteen taxa is pooled across its sections. Without the raw numerical tables, these totals cannot be reassigned to Wren’s Nest or converted into local bed-by-bed abundances.

Open University Virtual Microscope samples WN1–WN9. These nine educational samples illustrate carbonate texture, alteration and fossil debris. The published locality descriptions are retained below: scree samples have no proven individual source bed, proximity to a reef is not an in-place reef assignment, and a “nodular” rock texture alone does not establish the formal Nodular Limestone Member. Hand-specimen and whole-section previews support the record; the individual annotated microscope coordinates have not all been independently examined.

WN1: altered biomicrite. Brown micrite, bioclasts, iron oxy-hydroxide seams and sparry void fills. Weak fluid alteration with possible dissolution. Crinoid stem/echinoderm plates, brachiopods, bryozoans, corals and a spiral gastropod described. Near fault zone; precise member/bed absent. In-place versus loose not specified.

WN2: altered biomicrite. Small indistinct bioclasts, patchy brown micrite, iron oxy-hydroxide seams, calcite veins and rare sparry voids. Crinoid/echinoderm and brachiopod debris described; possible fluid dissolution. Near fault zone; precise member/bed absent. In-place versus loose not specified.

WN3: unaltered biomicrite. Heterogeneous micrite with clearer crinoid/echinoderm, brachiopod, bryozoan, gastropod and coral fragments. A trilobite section specifically located; micritized shell margins and dissolution seams. Near WN1/2 but farther from fault. In-place versus loose not specified.

WN4: nodular limestone. Bioclast-rich patches and muddy domains; crinoids/echinoderms, brachiopods, gastropods; coral/bryozoan rare. Sparry replacement and randomly oriented partial shell fills suggest reworked shell debris. Exposure near small adit and fault. Exposure mentioned; precise formal member is not supplied. Nodular texture does not by itself assign NOL.

WN5: packed biosparite. Echinoderm/crinoid-dominated shell debris, plus brachiopod/coral/bryozoan, with spar cement and syntaxial echinoderm overgrowths; little micrite. Ripple Beds scree. Explicit loose scree; exact bed not proven.

WN6: packed biomicrite. Bioclasts in brown micrite; echinoderm plates, crinoid stems/spines, brachiopods, coral and bryozoan; spar mainly fills fossil voids. Ripple Beds scree. Explicit loose scree; exact bed not proven.

WN7: poorly washed biosparite. Mixed micrite/spar, bioclast-rich, mosaics/void cement and syntaxial overgrowths, thin calcite veins. Echinoderm/crinoid, brachiopod, coral, bryozoan fragments. Scree around patch reefs. Explicit loose scree; reef adjacency is not in-situ reef assignment.

WN8: packed biomicrite. Bioclasts in micrite, spar mainly void fill/shell replacement. Echinoderm/crinoid, brachiopod, coral, bryozoan and a few gastropods. Around reef mounds. Around reefs; no precise bed or collection mode stated.

WN9: layered biomicrite. Central shell-rich mixed micrite/spar layer between muddier, sparsely fossiliferous layers. Brachiopod, gastropod, echinoderm/crinoid, coral and bryozoan. Geopetal partial fills support bedding orientation; one shell tilted. Near reef mounds. Near reefs; no precise bed or collection mode stated.

Carbon and oxygen isotope record. Ray and colleagues’ study, published online in 2019 and in its journal volume in 2020, uses bulk-carbonate stable isotopes to correlate discontinuous sections. Seven named Wren’s Nest and Mons Hill sections supply 136 observations in the supplementary matrix. The full regional matrix contains 459 rows, including Castle Hill and Hereford–Worcestershire comparisons. All values below are in per mille (‰) relative to V-PDB. Each height is measured from the lowest sample in that individual section, not from one common formation base.

Analytical and correlation limits. Unweathered, vein-free bulk-rock powders were analysed for carbonate carbon and oxygen isotopes. Fossil and sediment components can contribute to a bulk-rock value, and local facies changes influence the detailed curves. Faults, slumping and gaps require overlap between sections; ash beds, the Clematocrinus Bed and a stromatoporoid pavement help establish those ties. Correlated samples in overlapping sections remain separate observations rather than extra rock thickness.

Reef Knoll Stairwell / Steps section (RKS). The 0.68 m sampled interval lies around the basal transition and records a rise from 0.7‰ to 2.1‰ δ¹³C. Comparison with Castle Hill favours correlation with a grainstone lens in the Basement Beds rather than proof that its base is the true Lower Quarried Limestone boundary.

RKS samples RKS001–RKS004. RKS001: height 0.00 m; δ¹³C 0.7‰; δ¹⁸O -7.8‰. RKS002: height 0.04 m; δ¹³C 0.7‰; δ¹⁸O -7.1‰. RKS003: height 0.08 m; δ¹³C -0.2‰; δ¹⁸O -7.5‰. RKS004: height 0.1 m; δ¹³C 0.5‰; δ¹⁸O -6.3‰.

RKS samples RKS005–RKS008. RKS005: height 0.13 m; δ¹³C 0.8‰; δ¹⁸O -6.2‰. RKS006: height 0.19 m; δ¹³C 0.9‰; δ¹⁸O -5.4‰. RKS007: height 0.24 m; δ¹³C 0.9‰; δ¹⁸O -6.2‰. RKS008: height 0.28 m; δ¹³C 1.0‰; δ¹⁸O -7.4‰.

RKS samples RKS009–RKS012. RKS009: height 0.31 m; δ¹³C 1.1‰; δ¹⁸O -5.7‰. RKS010: height 0.36 m; δ¹³C 0.7‰; δ¹⁸O -5.9‰. RKS011: height 0.42 m; δ¹³C 1.7‰; δ¹⁸O -5.4‰. RKS012: height 0.45 m; δ¹³C 1.4‰; δ¹⁸O -7.0‰.

RKS samples RKS013–RKS016. RKS013: height 0.49 m; δ¹³C 1.6‰; δ¹⁸O -5.5‰. RKS014: height 0.56 m; δ¹³C 1.9‰; δ¹⁸O -5.1‰. RKS015: height 0.58 m; δ¹³C 1.8‰; δ¹⁸O -5.6‰. RKS016: height 0.62 m; δ¹³C 1.6‰; δ¹⁸O -6.2‰.

RKS samples RKS017–RKS017. RKS017: height 0.68 m; δ¹³C 2.1‰; δ¹⁸O -4.8‰.

Lower NCC Cutting (LNC). WNH2 and WNH3 constrain the PS2 correlation. Carbon-isotope values reach 5.5‰ around the top of PS2 and then decline through the succeeding Lower Quarried intervals. Minor faulting affects the basal and upper contacts; the study discusses 2.5‰ near the later decline without providing an uninterrupted physical exposure across the member boundary.

LNC samples LNC001–LNC004. LNC001: height 0.00 m; δ¹³C 4.8‰; δ¹⁸O -6.7‰. LNC002: height 0.50 m; δ¹³C 5.2‰; δ¹⁸O -5.3‰. LNC003: height 1.00 m; δ¹³C 5.0‰; δ¹⁸O -6.5‰. LNC004: height 1.50 m; δ¹³C 5.5‰; δ¹⁸O -5.6‰.

LNC samples LNC005–LNC008. LNC005: height 2.00 m; δ¹³C 5.5‰; δ¹⁸O -6.1‰. LNC006: height 3.00 m; δ¹³C 5.5‰; δ¹⁸O -6.7‰. LNC007: height 3.50 m; δ¹³C 3.9‰; δ¹⁸O -8.4‰. LNC008: height 4.00 m; δ¹³C 4.9‰; δ¹⁸O -6.8‰.

LNC samples LNC009–LNC012. LNC009: height 4.50 m; δ¹³C 5.4‰; δ¹⁸O -6.7‰. LNC010: height 5.00 m; δ¹³C 5.1‰; δ¹⁸O -6.7‰. LNC011: height 5.50 m; δ¹³C 2.9‰; δ¹⁸O -8.4‰. LNC012: height 5.75 m; δ¹³C 5.0‰; δ¹⁸O -7.0‰.

LNC samples LNC013–LNC016. LNC013: height 6.25 m; δ¹³C 4.9‰; δ¹⁸O -6.2‰. LNC014: height 6.75 m; δ¹³C 2.5‰; δ¹⁸O -6.1‰. LNC015: height 7.00 m; δ¹³C 4.2‰; δ¹⁸O -6.0‰. LNC016: height 7.25 m; δ¹³C 3.5‰; δ¹⁸O -7.2‰.

LNC samples LNC017–LNC018. LNC017: height 7.50 m; δ¹³C 3.5‰; δ¹⁸O -7.2‰. LNC018: height 7.75 m; δ¹³C 3.0‰; δ¹⁸O -7.8‰.

Seven Sisters Quarry North (SSQ). A pillar supplied the study’s section through PS6 and the base of the Nodular Limestone where the NCC contact is faulted. Minor quarry-related slumping affects its base. δ¹³C declines to 2.2‰ in the nine-sample series. This is the description of a scientific sampling exposure, not permission to enter the workings.

SSQ samples SSQ001–SSQ004. SSQ001: height 0.00 m; δ¹³C 3.3‰; δ¹⁸O -6.1‰. SSQ002: height 0.50 m; δ¹³C 3.1‰; δ¹⁸O -6.8‰. SSQ003: height 1.00 m; δ¹³C 3.5‰; δ¹⁸O -5.5‰. SSQ004: height 1.50 m; δ¹³C 3.1‰; δ¹⁸O -6.8‰.

SSQ samples SSQ005–SSQ008. SSQ005: height 2.00 m; δ¹³C 3.1‰; δ¹⁸O -6.2‰. SSQ006: height 2.50 m; δ¹³C 2.8‰; δ¹⁸O -7.3‰. SSQ007: height 3.00 m; δ¹³C 2.5‰; δ¹⁸O -7.1‰. SSQ008: height 3.50 m; δ¹³C 2.2‰; δ¹⁸O -6.7‰.

SSQ samples SSQ009–SSQ009. SSQ009: height 4.00 m; δ¹³C 2.2‰; δ¹⁸O -6.5‰.

Upper NCC Cutting (UNC). The record spans PS7–PS9 and part of PS10. It includes a δ¹³C trough of −0.6‰ at the local 4.00 m level, a PS8 peak of 2.6‰ and a subsequent low of 1.7‰ at 9.00 m before rising towards 3‰ and above. These heights belong to the UNC datum only.

UNC samples UNC001–UNC004. UNC001: height 0.00 m; δ¹³C 1.1‰; δ¹⁸O -9.5‰. UNC002: height 0.50 m; δ¹³C 1.2‰; δ¹⁸O -5.6‰. UNC003: height 1.00 m; δ¹³C 1.7‰; δ¹⁸O -7.7‰. UNC004: height 1.50 m; δ¹³C 1.2‰; δ¹⁸O -6.4‰.

UNC samples UNC005–UNC008. UNC005: height 2.00 m; δ¹³C 0.5‰; δ¹⁸O -8.7‰. UNC006: height 2.50 m; δ¹³C 0.9‰; δ¹⁸O -6.7‰. UNC007: height 3.00 m; δ¹³C 1.0‰; δ¹⁸O -7.1‰. UNC008: height 3.50 m; δ¹³C 0.7‰; δ¹⁸O -7.6‰.

UNC samples UNC009–UNC012. UNC009: height 4.00 m; δ¹³C -0.6‰; δ¹⁸O -7.7‰. UNC010: height 4.50 m; δ¹³C -0.4‰; δ¹⁸O -9.5‰. UNC011: height 5.00 m; δ¹³C 0.2‰; δ¹⁸O -8.2‰. UNC012: height 5.50 m; δ¹³C 2.0‰; δ¹⁸O -5.9‰.

UNC samples UNC013–UNC016. UNC013: height 5.75 m; δ¹³C 2.0‰; δ¹⁸O -6.9‰. UNC014: height 6.25 m; δ¹³C 2.5‰; δ¹⁸O -6.7‰. UNC015: height 6.75 m; δ¹³C 2.5‰; δ¹⁸O -6.9‰. UNC016: height 7.25 m; δ¹³C 2.4‰; δ¹⁸O -6.9‰.

UNC samples UNC017–UNC020. UNC017: height 7.50 m; δ¹³C 2.6‰; δ¹⁸O -5.7‰. UNC018: height 7.75 m; δ¹³C 2.5‰; δ¹⁸O -5.4‰. UNC019: height 8.00 m; δ¹³C 2.3‰; δ¹⁸O -5.7‰. UNC020: height 8.50 m; δ¹³C 2.4‰; δ¹⁸O -6.0‰.

UNC samples UNC021–UNC024. UNC021: height 9.00 m; δ¹³C 1.7‰; δ¹⁸O -8.0‰. UNC022: height 9.50 m; δ¹³C 2.2‰; δ¹⁸O -6.8‰. UNC023: height 10.00 m; δ¹³C 2.0‰; δ¹⁸O -6.0‰. UNC024: height 10.50 m; δ¹³C 1.8‰; δ¹⁸O -5.1‰.

UNC samples UNC025–UNC028. UNC025: height 11.00 m; δ¹³C 2.2‰; δ¹⁸O -5.3‰. UNC026: height 11.50 m; δ¹³C 2.4‰; δ¹⁸O -5.4‰. UNC027: height 12.00 m; δ¹³C 2.7‰; δ¹⁸O -4.6‰. UNC028: height 12.50 m; δ¹³C 2.5‰; δ¹⁸O -6.4‰.

UNC samples UNC029–UNC032. UNC029: height 13.00 m; δ¹³C 2.8‰; δ¹⁸O -5.8‰. UNC030: height 13.50 m; δ¹³C 3.1‰; δ¹⁸O -5.6‰. UNC031: height 14.00 m; δ¹³C 2.9‰; δ¹⁸O -5.8‰. UNC032: height 14.50 m; δ¹³C 3.0‰; δ¹⁸O -6.1‰.

Reef Knoll Quarry (RKQ). Two quarry sections tied by the Clematocrinus Bed were used to encompass PS10. The second Homerian carbon-isotope peak reaches 3.8‰ within its lower 4 m. The curve is a correlated record rather than one unbroken quarry-face log.

RKQ samples RKQ001–RKQ004. RKQ001: height 0.00 m; δ¹³C 2.8‰; δ¹⁸O -5.3‰. RKQ002: height 0.50 m; δ¹³C 2.9‰; δ¹⁸O -5.9‰. RKQ003: height 1.00 m; δ¹³C 3.0‰; δ¹⁸O -6.5‰. RKQ004: height 1.50 m; δ¹³C 3.6‰; δ¹⁸O -6.4‰.

RKQ samples RKQ005–RKQ008. RKQ005: height 2.00 m; δ¹³C 3.5‰; δ¹⁸O -5.6‰. RKQ006: height 2.50 m; δ¹³C 3.7‰; δ¹⁸O -6.0‰. RKQ007: height 3.00 m; δ¹³C 3.8‰; δ¹⁸O -5.9‰. RKQ008: height 3.50 m; δ¹³C 3.8‰; δ¹⁸O -5.6‰.

RKQ samples RKQ009–RKQ012. RKQ009: height 4.00 m; δ¹³C 3.8‰; δ¹⁸O -5.3‰. RKQ010: height 4.50 m; δ¹³C 3.6‰; δ¹⁸O -5.8‰. RKQ011: height 5.00 m; δ¹³C 3.3‰; δ¹⁸O -7.3‰. RKQ012: height 5.50 m; δ¹³C 3.5‰; δ¹⁸O -6.2‰.

RKQ samples RKQ013–RKQ016. RKQ013: height 6.00 m; δ¹³C 3.4‰; δ¹⁸O -6.0‰. RKQ014: height 6.50 m; δ¹³C 3.3‰; δ¹⁸O -6.1‰. RKQ015: height 7.00 m; δ¹³C 3.4‰; δ¹⁸O -6.3‰. RKQ016: height 7.50 m; δ¹³C 3.2‰; δ¹⁸O -6.1‰.

RKQ samples RKQ017–RKQ020. RKQ017: height 8.00 m; δ¹³C 3.2‰; δ¹⁸O -6.1‰. RKQ018: height 8.50 m; δ¹³C 3.1‰; δ¹⁸O -5.7‰. RKQ019: height 9.00 m; δ¹³C 2.8‰; δ¹⁸O -6.8‰. RKQ020: height 9.50 m; δ¹³C 2.9‰; δ¹⁸O -6.7‰.

RKQ samples RKQ021–RKQ023. RKQ021: height 10.00 m; δ¹³C 2.7‰; δ¹⁸O -6.0‰. RKQ022: height 10.50 m; δ¹³C 1.9‰; δ¹⁸O -6.2‰. RKQ023: height 11.00 m; δ¹³C 2.0‰; δ¹⁸O -6.3‰.

Snake Pit Quarry (SPQ), Mons Hill. The later article places this section on Mons Hill, whereas the 2010 photograph caption uses Wren’s Nest Hill. The named section and mapped position distinguish it. The Ripple Beds provide a correlation with Reef Knoll Quarry, and PS11 values are mostly slightly above 2‰. Faulting affects the upper transition.

SPQ samples SPQ001–SPQ004. SPQ001: height 0.00 m; δ¹³C 2.2‰; δ¹⁸O -6.3‰. SPQ002: height 0.50 m; δ¹³C 1.1‰; δ¹⁸O -9.5‰. SPQ003: height 1.00 m; δ¹³C 2.3‰; δ¹⁸O -6.1‰. SPQ004: height 1.50 m; δ¹³C 2.4‰; δ¹⁸O -6.7‰.

SPQ samples SPQ005–SPQ008. SPQ005: height 2.00 m; δ¹³C 1.1‰; δ¹⁸O -7.8‰. SPQ006: height 2.50 m; δ¹³C 2.3‰; δ¹⁸O -7.6‰. SPQ007: height 3.00 m; δ¹³C 2.3‰; δ¹⁸O -7.7‰. SPQ008: height 3.50 m; δ¹³C 2.2‰; δ¹⁸O -8.2‰.

SPQ samples SPQ009–SPQ012. SPQ009: height 4.00 m; δ¹³C 2.1‰; δ¹⁸O -6.6‰. SPQ010: height 4.50 m; δ¹³C 2.1‰; δ¹⁸O -6.8‰. SPQ011: height 5.00 m; δ¹³C 2.1‰; δ¹⁸O -8.4‰. SPQ012: height 5.50 m; δ¹³C 2.0‰; δ¹⁸O -8.2‰.

SPQ samples SPQ013–SPQ014. SPQ013: height 6.00 m; δ¹³C 1.8‰; δ¹⁸O -9.0‰. SPQ014: height 6.50 m; δ¹³C 1.0‰; δ¹⁸O -7.7‰.

Lion’s Mouth Cavern section (LMC). An overlapping scientific section records upper PS11, PS12 and basal Lower Elton. Carbon values decline from 2.2–1.9‰ over 0.00–1.68 m to 0.6‰ at 2.71 m in the Passage Beds, briefly recover, and reach 0.2‰ higher in the section. The basal PS12 stromatoporoid pavement supplies a correlation tie. The exposure name does not establish public underground access.

LMC samples LMC001–LMC004. LMC001: height 0.00 m; δ¹³C 2.2‰; δ¹⁸O -8.3‰. LMC002: height 0.21 m; δ¹³C 2.0‰; δ¹⁸O -7.4‰. LMC003: height 0.44 m; δ¹³C 2.1‰; δ¹⁸O -7.2‰. LMC004: height 0.68 m; δ¹³C 2.0‰; δ¹⁸O -8.6‰.

LMC samples LMC005–LMC008. LMC005: height 0.95 m; δ¹³C 2.1‰; δ¹⁸O -8.7‰. LMC006: height 1.12 m; δ¹³C 2.2‰; δ¹⁸O -7.6‰. LMC007: height 1.41 m; δ¹³C 2.1‰; δ¹⁸O -7.6‰. LMC008: height 1.68 m; δ¹³C 1.9‰; δ¹⁸O -7.7‰.

LMC samples LMC009–LMC012. LMC009: height 1.95 m; δ¹³C 1.1‰; δ¹⁸O -9.2‰. LMC010: height 2.09 m; δ¹³C 1.3‰; δ¹⁸O -8.9‰. LMC011: height 2.26 m; δ¹³C 0.9‰; δ¹⁸O -6.6‰. LMC012: height 2.44 m; δ¹³C 0.9‰; δ¹⁸O -6.5‰.

LMC samples LMC013–LMC016. LMC013: height 2.71 m; δ¹³C 0.6‰; δ¹⁸O -8.3‰. LMC014: height 2.90 m; δ¹³C 1.0‰; δ¹⁸O -7.6‰. LMC015: height 3.07 m; δ¹³C 1.2‰; δ¹⁸O -9.2‰. LMC016: height 3.30 m; δ¹³C 0.9‰; δ¹⁸O -7.5‰.

LMC samples LMC017–LMC020. LMC017: height 3.50 m; δ¹³C 0.7‰; δ¹⁸O -8.4‰. LMC018: height 3.66 m; δ¹³C 0.5‰; δ¹⁸O -6.3‰. LMC019: height 3.80 m; δ¹³C 0.4‰; δ¹⁸O -7.2‰. LMC020: height 4.00 m; δ¹³C 0.5‰; δ¹⁸O -6.4‰.

LMC samples LMC021–LMC023. LMC021: height 4.21 m; δ¹³C 0.2‰; δ¹⁸O -6.8‰. LMC022: height 4.43 m; δ¹³C 0.3‰; δ¹⁸O -6.5‰. LMC023: height 4.63 m; δ¹³C 0.2‰; δ¹⁸O -6.2‰.

WNH15 dated ash and the upper transition. The Lion’s Mouth figure locates WNH15 within the Passage Beds and reproduces an age of 427.86 ± 0.32 million years from the U–Pb zircon work cited by Ray and colleagues. This is a published date for a specific ash horizon, not a numerical age assigned to every fossil at Wren’s Nest. The same section places a coarse grainstone with shale and limestone rip-up clasts, rolled and in-place stromatoporoids and corals at the base of PS12, followed by thinner crinoidal rudstones, grainstones and finer packstones as conditions changed.

Lion’s Mouth thin-section sample TS16. The study’s Figure 9e–f illustrates a bioturbated crinoidal packstone with phosphatised crinoid ossicles from Lion’s Mouth Cavern. The overview scale is 2.5 mm and the close-up scale 500 micrometres. These two panels show one local sample. Panels 9a–d and samples TS12–TS15 belong to Bruff Business Park and do not establish the same microfacies at Wren’s Nest.

Nomenclature outside the local succession. The 2025 BGS discussion retains the recognisable West Midlands tripartite limestone members. Its proposed Wilderhope Member concerns Wenlock Edge, alongside the Longville Member, and is not a fourth Wren’s Nest member. Proposed Wootton, Pitch Coppice Mudstone and Goggin Road terminology, and the proposed Welsh Borderland Group–Hafren Supergroup hierarchy, are not silently substituted for the current local Lexicon entries. Likewise, Tickwood, Farley, Buildwas and Apedale names in regional comparisons do not by themselves establish extra exposed local units.

Limits of the numerical fossil record. This account does not reproduce a complete genus-by-bed faunal matrix. The numerical cells of Ray and Thomas’s 2007 survey figures 3–6 have not been independently recovered and checked here, and the conodont count, diversity and turnover tables associated with Jarochowska and colleagues’ 2018 study remain unverified at individual Wren’s Nest sample level. Their broader study totals and pooled regional results are not recast as a complete local checklist or local abundance record.

References. The following sources support the measured succession, independent studies and qualified specimen records above. Bibliographic dates and historical terminology are retained where relevant.

British Geological Survey. Lexicon of Named Rock Units, entries CBRD, WEL, LQL, NOL, UQL, LEL. Checked October 2026.

Aldridge, R. J. and colleagues. 2000. British Silurian Stratigraphy. Geological Conservation Review Series 19. Wren’s Nest account, pp. 191–198, especially Figure 4.9. Source.

Cutler, A., Oliver, P. G. and Reid, C. G. R. 1990. Wren’s Nest National Nature Reserve: Geological Handbook and Field Guide. Nature Conservancy Council and Dudley Metropolitan Borough Council. Source.

Ray, D. C. and Thomas, A. T. 2007. Carbonate depositional environments, sequence stratigraphy and exceptional skeletal preservation in the Much Wenlock Limestone Formation (Silurian) of Dudley, England. Palaeontology 50, 197–222. Source.

Ray, D. C., Brett, C. E., Thomas, A. T. and Collings, A. V. J. 2010. Late Wenlock sequence stratigraphy in central England. Geological Magazine 147, 123–144. Source.

Ray, D. C., Collings, A. V. J., Worton, G. J. and Jones, G. 2011. Upper Wenlock bentonites from Wren’s Nest Hill, Dudley: comparisons with prominent bentonites along Wenlock Edge, Shropshire, England. Geological Magazine 148, 670–681. Source.

Ray, D. C. (ed.) 2011. Siluria Revisited: A Field Guide. International Subcommission on Silurian Stratigraphy, Field Meeting 2011. Wren’s Nest and Mons Hill contributions, pp. 121–146, including Figures 38–44. Source.

Oliver, P. G. 1981. Lithological Groups within the Wenlock Limestone (Silurian) at Wren’s Nest, Dudley. Source.

Kershaw, S., Da Silva, A.-C. and Sendino, C. 2021 [published online 2022]. British Silurian stromatoporoids: faunas, palaeobiology, and palaeogeographical significance. Monographs of the Palaeontographical Society 175 (660). Source.

Oakley, K. P. 1966. Some pearl-bearing Ceramoporidae (Polyzoa). Bulletin of the British Museum (Natural History), Geology 14 (1), 1–20, 9 plates. Source.

Ray, D. C., Jarochowska, E., Röstel, P., Worton, G. J., Munnecke, A., Wheeley, J. R. and Boomer, I. 2019 [journal volume 2020]. High resolution correlation of the Homerian carbon isotope excursion (Silurian) across the interior of the Midland Platform (Avalonia), UK. Geological Magazine. Source.

Ray and colleagues. Supplementary carbon and oxygen isotope matrix accompanying the Homerian carbon-isotope study. Source.

Davies, J. R. 2025. A systems-based lithostratigraphy for the Lower Palaeozoic Welsh Basin and adjoining region. British Geological Survey Open Report OR/25/018, 256 pp.

British Geological Survey. Palaeosaurus specimen catalogue: the nine Wren’s Nest records listed above, checked October 2026. Source.

Jarochowska, E., Ray, D. C., Röstel, P., Worton, G. and Munnecke, A. 2018 [published online 11 September 2017]. Harnessing stratigraphic bias at the section scale: conodont diversity in the Homerian (Silurian) of the Midland Platform, England. Palaeontology 61, 57–76. Article. Associated dataset.

Open University. Virtual Microscope, Wren’s Nest samples WN1, WN2, WN3, WN4, WN5, WN6, WN7, WN8, WN9.