Robinswood Hill Fossil Hunting

1928 – Quarry fauna and environment described
Watts’s excursion account described the quarry fossils and their environmental significance, providing an early scientific account of the site.

1955 – Lithological succession and ammonite zones assessed
D. V. Ager described the sequence and estimated its ammonite-zone ranges, advancing the quarry’s use in understanding the inland Lower Jurassic.

1966 – Geological site notified
Robin’s Wood Hill Quarry was notified as a Site of Special Scientific Interest, recognising its important Early Jurassic section.

1971 – Detailed stratigraphy established
C. P. Palmer logged the succession and placed ammonite zonal and subzonal boundaries within it. Comparison with Stonehouse and the Stowell Park Borehole made the quarry important for regional correlation.

1972–1974 – Microfossils illuminate the Jurassic seaway
A. R. Lord investigated the ostracod fauna. Its composition helped distinguish the relatively shallow conditions at Robin’s Wood Hill and connections with the Dorset marine basin.

1973 – Bivalve fauna and two new morphospecies published
Palmer documented the distribution and ecology of invertebrates and described Hippopodium tuffleyensis and Hettangia aperta in a study of the Tuffley and Stonehouse pits. The names record that published taxonomic work; the two localities should not be treated as one specimen source.

Mid-1970s – Articulated sea lilies and brittle stars recovered
A thin siltstone yielded articulated Balanocrinus gracilis, large Palaeocoma milleri and two intact Hemieuryale lunaris, previously known only from separate skeletal pieces. Their association records rapid burial of a seabed community.

1975 – Tuffley supplies the type of a new bivalve
Palmer named Cardinia tuffleyensis from a right valve, BM(NH) LL31275, from his Bed 14 at Tuffley. One left-valve paratype came from the same bed; four other paratypes came from Stonehouse. The original plate assigns the Tuffley type horizon to the Subnodosus Subzone.

1985 – Lower Pliensbachian ammonite succession refined
Phelps used additional ammonite evidence to revise the local subzonal interpretation. The work showed why correlations based mainly on rock appearance needed testing against fossils.

1987 – Quarry sequence logged in greater detail
N. Chidlaw recorded a more finely divided section, forming the basis of the later 37-bed quarry account. Some equivalences with Palmer’s older numbering remained uncertain.

1989 – Crinoid material studied systematically
M. J. Simms figured well-preserved crinoids from the quarry. His description of Balanocrinus solenotis was based partly on fragmentary material from the upper Dyrham Formation here.

1990 – Upper beds and basin development reinterpreted
Simms’s study of Severn Basin sedimentation revised parts of the quarry’s ammonite chronology. Records of Amaltheus subnodosus above the pebble bed helped reassess the age of strata formerly included in the Marlstone.

1999 – Dyrham Formation type section recognised
The modern Lower Jurassic formational framework identified the Tuffley quarry as the type section of the Dyrham Formation, giving the exposure a central role in the definition of that unit.

2000 – Conservation excavation improved exposure
Excavation re-exposed part of the Dyrham Formation that had become obscured, improving the section available for geological study.

2001 – Pliensbachian–Toarcian transition recorded nearby
In October, Chidlaw logged the separate trackside exposure of the Marlstone Rock Formation and basal Whitby Mudstone. Its four units complement the quarry record without forming part of the same measured face.

The following account distinguishes the main two-level quarry, an older record of its now-obscured floor, and the separate trackside section at SO 8367 1468. Measurements describe the published sections; vegetation, scree and management can change what is visible. Bed numbers from different logs are not interchangeable. The quarry description follows Chidlaw’s log as synthesised in the 2004 Geological Conservation Review, with Palmer’s 1971 equivalents in parentheses.

LIAS GROUP

The principal quarry succession is Pliensbachian. Its numbered beds are presented from youngest to oldest below. The Dyrham Formation is the dominant unit. “Capricornus Sandstone” is an informal marker interval, not an additional formal member introduced here. At the basal transition, published authors have placed the Dyrham–Charmouth boundary at different levels; this account follows the GCR’s first substantial silts and retains the distinction from the older basal mudstone record.

Main quarry section: younger beds to older beds

Marlstone Rock Formation

Spinatum Zone

Bed 37 (= 16c) (0.33 m)
Limestone, massive, rubbly weathering, brownish-grey, bioclastic, with abundant ferruginous ooids. Scattered shelly fauna including belemnites, rhynchonellids and bivalves. Pleuroceras spinatum and Amaltheus cf. subnodosus recorded by Palmer (1971).

Dyrham Formation

Margaritatus Zone, Subnodosus To ?Gibbosus Subzones

Bed 36 (= 16b) (4.87 m)
Sandstone, yellow-buff weathering, ferruginous, friable, micaceous, fine, silty. Locally between 1.8 m and 3.3 m above the base of the unit are hard, calcite-cemented, irregular ‘doggers’ up to about 1.5 m thick and 3 m across, with smaller ellipsoidal calcite concretions below the dogger horizon and more laterally extensive, though discontinuous, bands of calcite-cemented sand above the doggers. Abundant bioturbation, although trough cross-lamination and dish structures locally present. Fossils scattered and only well-preserved in cemented units, but including belemnites, bivalves and debris of the crinoid Balanocrinus solenotis. Simms (1990a) recorded Amaltheus subnodosus up to 2.6 m above the base of the unit.

Bed 35 (= 16a) (0.18 m)
Conglomerate, irregular, pebble-to cobble-grade. Clasts mostly flat-lying discoidal or ellipsoidal, of pale-grey siltstone. Matrix of yellow-brown mudstone within abundant fine bioclastic debris. Ager (1954) recorded Gibbirhynchia micra from the clasts.

Bed 34 (= 15 part) (0.20 m)
Siltstone, yellow-brown, sandy, micaceous. Local indistinct and bioturbated planar laminations.

Bed 33 (= 15 part) (1.80 m)
Silt, pale greenish-grey, sandy, micaceous. Mostly planar laminated with some cross-laminations near base.

Bed 32 (= 15 part) (3.33 m)
Silt, pale greenish-grey, micaceous. Planar laminated. Grades up into Bed 33 above.

Bed 31 (= 15 part) (3.00 m)
Mudstone, dark blue-grey, clayey, micaceous, silty. Grades up into Bed 32 above.

Bed 30 (= 14 part) (0.12 m)
Conglomerate, flat pebble- to cobble-grade, with siltstone clasts set in a green-grey, sandy micaceous silt matrix.

Bed 29 (= 14 part) (0.24 m)
Limestone, hard, pale-grey, bioclastic, with occasional ferruginous ooids in top 0.02 m. Undulating base and top.

Bed 28 (= 14 part) (0.22 m)
Conglomerate, pebble- to cobble-grade. Discoidal clasts of hard blue-grey siltstone with ferruginous rind in a matrix of green-grey mudstone with abundant bioclastic debris. Irregular base.

Stokesi Subzone

Bed 27 (= 13 part) (0.36 m)
Silt, pale greenish-grey, locally cemented, sandy, micaceous. Bioturbated in top 0.25 m; cross-laminated below.

Bed 26 (= 13 part) (1.64 m)
Silt, pale greenish-grey, sandy, micaceous. Cross-laminated in top 0.04 m; planar laminated below.

Bed 25 (= 13 part) (4.33 m)
Silt, greenish-grey, clayey, micaceous, planar laminated in parts. Grades up into Bed 26 above.

Bed 24 (= 12) (0.56 m)
Siltstone, hard, shelly, micaceous. Amaltheus stokesi and Lytoceras fimbriatum recorded by Palmer (1971).

Bed 23 (= 11) (3.27 m)
Clay, blue-grey, silty, passing up into dark greenish-grey, planar-laminated, clayey micaceous silt. Floor of upper quarry lies 0.2 m above the base of this unit on the south side of the quarry

Bed 22 (= 10) (0.35 m)
Conglomerate, pebble-grade, with hard, discoidal/ellipsoidal, blue-grey siltstone clasts in a matrix of grey-green mudstone with abundant coarse bioclastic debris and large thick-ribbed bivalves. The upper 0.15 m is deeply weathered, with friable clasts and a 0.05 m-thick reddish-orange layer at the top. Erosion surface contact with Bed 21. Amaltheus wertheri and Tragophylloceras recorded by Phelps (1985).

Bed 21 (= 9g part) (0.25 m)
Silt, blue-grey, sandy, micaceous. Planar laminated but streaked with fine yellow sand in places. Occasional scattered siderite nodules up to 0.25 m across and 0.06 m thick.

Bed 20 (= 9g part) (0.04 m)
Siltstone, blue-grey, sandy, micaceous, massive, with pea-sized siderite nodules. Broken thin-shelled bivalves.

Bed 19 (= 9g part) (3.52 m)
Silt, pale blue-grey, sandy, micaceous, with planar laminations locally disturbed by horizontal burrows. Occasional pea-sized siderite nodules and discontinuous row of larger siderite nodules at 1.7 m above the base. Small limonitic casts of amaltheid ammonites are common. Amaltheus stokesi and A. sp. recorded by Phelps (1985) from about this level.

Bed 18 (= 9f part) (0–0.08 m)
Siltstone, discontinuous, pale grey, commonly with abundant remains of Balanocrinus gracilis. Bivalves common and specimens of Amaltheus bifurcus and A. wertheri.

Lower Pliensbachian Substage

Davoei Zone, Figulinum Subzone

Bed 17 (= 9f part) (0.66 m)
Silt, green-grey, sandy, micaceous. Mostly planar laminated but cross-laminated towards base.

Bed 16 (= 9e) (0.10 m)
Siltstone, pale blue-grey, indurated, planar- and cross-laminated, micaceous, with broken shell debris and small siderite concretions. Oistoceras? angulatum recorded by Phelps (1985).

Bed 15 (= 9d) (5.49 m)
Silt, blue-grey, micaceous, planar laminated and locally bioturbated.

Bed 14 (= 9c) (0.08 m)
Siltstone, blue-grey, indurated, wavy laminated, micaceous, with burrow mottling.

Capricornus Subzone

Bed 13 (= 9b part) (6.62 m)
Silt, blue-grey, planar laminated, micaceous.

Bed 12 (= 9b part) (1.14 m)
Silt, dark blue-grey, indistinctly laminated, muddy, micaceous. Aegoceras crescens transitional to Oistoceras angulatum recorded by Phelps (1985).

Bed 11 (= ?) (0.08 m)
Iron-stained pebble conglomerate, with siltstone clasts in a siltstone matrix.

Bed 10 (= ?) (0.80 m)
Silt, blue-grey, indistinctly laminated, sandy, micaceous.

Bed 9 (= ?) (0.04 m)
Iron-stained pebble-grade conglomerate, with siltstone clasts in a siltstone matrix.

Bed 8 (= ?7) (0.80 m)
Silt, blue-grey, indistinctly laminated, sandy, micaceous, with bivalve moulds.

Bed 7 (= ?) (0.05 m)
Pebble conglomerate, with siltstone clasts in a siltstone matrix. Aegoceras capricornus recorded by Phelps (1985).

Bed 6 (= 6) (1.65 m)
Siltstone, pale grey, indurated, clayey, micaceous, forming prominent hard band. Together with beds 7 and 8 this represents the ‘Capricornus Sandstone’ of Palmer (1971).

Maculatum Subzone

Bed 5 (= 5 part) (1.14 m)
Siltstone, pale grey, indistinctly laminated, clayey, micaceous.

Bed 4 (= 5 part) (5.37 m)
Silt, pale grey, planar laminated, clayey, micaceous. Moulds of small thin-ribbed bivalves near base.

Bed 3 (= 4) (0.19 m)
Siltstone, pale grey, planar laminated, clayey, micaceous.

Bed 2 (= 3c part) (10.5 m)
Silt, pale grey, planar laminated, clayey, micaceous. Siderite nodule bands at 8 m and 9.2 m above base.

Bed 1 (= 3c part) (1 (seen) m)
Silt, blue-grey, planar laminated, micaceous, with moulds of small thin-ribbed bivalves. Strata below this level were recorded by Palmer (1971, 1973) but are no longer visible (bed numbers are those of Palmer, 1971).

Charmouth Mudstone Formation

Bed 3c (c. 2 m)
(part): Shales, grey, silty, with ferruginous nodules.

Bed 3b (1.82 m)
Clay, blue, sticky, with ironstone nodules. Androgynoceras sparsicosta recorded by Phelps (1985) and Aegoceras maculatum recorded by Palmer (1971).

Ibex Zone, Luridum Subzone

Bed 3a (1.23 m)
Shales, grey, silty, grading up to dark-grey clay.

Bed 2 (0.30 m)
Shales, hard, grey, sandy ?Beaniceras luridum recorded by Phelps (1985) and Palmer (1971).

Bed 1 (c. 3 m)
Shales, grey, with nodules.

How the older floor record relates to the face
The final five entries above, labelled 3c (part), 3b, 3a, 2 and 1 under Charmouth Mudstone, use Palmer’s numbering alone and describe beds recorded below the numbered 37–1 face succession. Those older floor exposures were already rarely visible when the GCR account was prepared. They must not be confused with Chidlaw’s face beds 1–3, which lie in the overlying silty succession.

Separate trackside section, recorded October 2001
This small exposure at SO 8367 1468 is a different measured section. Its letters A–D distinguish it from the numbered quarry beds. It records the weathered top of the Marlstone and the basal Whitby Mudstone; the presumed ammonite zones are not direct ammonite determinations for these clays.

Toarcian Stage

Whitby Mudstone Formation

Tenuicostatum Zone (Presumed)

Unit D (0.90 (seen) m)
Clay, fawn-brown, soft, sticky.

Unit C (0.30 m)
Clay, mottled, pale-grey/orange, soft, sticky. This has a diffuse contact with Unit D above and infills, and overlies by a few cm, the irregular top of Unit B below.

Upper Pliensbachian Substage

Marlstone Rock Formation

Spinatum Zone (Presumed)

Unit B (0.45 m)
Clay, mottled, pale-grey/orange/red-brown, soft, sticky, containing weathered clasts of Unit A; some are up to 0.35 m across, angular and only slightly iron-stained; others are reddish-brown and friable, 3–4 cm across, subangular and of high sphericity. The contact with units above and below is irregular, with mammilated limonite nodules 2–5 cm across locally present on the upper surface.

Unit A (1.50 (seen) m)
Limestone, massive, well jointed, greenish-grey, bioclastic, with abundant ferruginous ooids. Belemnites and bivalves common, with some rhynchonellid brachiopods. This bed is lithologically identical to Bed 37 (= 16c of Palmer, 1971) of the main quarry section described above.

Boundaries and correlations
Ammonites place the Lower–Upper Pliensbachian boundary below Bed 18, where Amaltheus bifurcus occurs. The exact equivalence of Palmer’s beds 7–9a with the later beds 7–11 could not be reconciled confidently. Older assignments of beds 12–14 to the Figulinum Subzone were revised after additional ammonites were found. These uncertainties should remain visible rather than being resolved by a simple renumbering.

The upper sandstone and Marlstone
Palmer included beds now numbered 35–37 in the Marlstone. The modern account places the conglomerate and dogger-bearing sandstone, beds 35 and 36, in the Dyrham Formation and restricts the main-quarry Marlstone to Bed 37. Amaltheus subnodosus in the sandstone demonstrates that much of it predates the Spinatum Zone. The Gibbosus Subzone has not been proved here; its uncertain presence is reflected in the zonal heading. The Subnodosus Sandstone correlation proposed for other Severn Basin sections is also disputed at this quarry and is not treated as an independently established local member.

Depositional setting and exceptional preservation
The general upward increase in silt and sand reflects shallowing of the marine basin, but individual beds also record erosion, changing sediment supply and uneven subsidence. Pebble conglomerates contain reworked fragments of earlier siltstone. Iron-rich weathered surfaces at the top of Bed 22 and trackside Unit B have been interpreted as possible soil-like alteration during brief emergence, rather than proven land surfaces in every detail. Articulated sea lilies and brittle stars in Bed 18 are interpreted as an obrution assemblage, buried rapidly, possibly by storm-stirred sediment.

Wider-hill context
The GCR locality map shows Whitby Mudstone on the higher hill and a small Inferior Oolite summit cap. The 1910 Geologists’ Association account described Cotteswold Sands on the upper slopes. That historical name is commonly associated with the Bridport Sand Formation, but a measured local Bridport section and its precise modern boundary are not established by the quarry logs reproduced here. The higher hillside must therefore remain a separate part of the geological story; neither its full thickness nor a bed-by-bed summit-trail log is inferred from the quarry measurements.

A 2014 study also listed 16 Gresslya abducta and 19 Pleuromya uniformis from “Scissums Beds” at Robin’s Wood Hill. Those broader-hill records use the study’s historical unit name; no exact exposure or numbered quarry bed was specified.

Additional fossil markers in Palmer’s numbered succession
Thin shell-rich layers in Palmer’s floor Bed 2 yielded Beaniceras cf. luridum. His Bed 8 yielded the brachiopod Tetrarhynchia dunrobinensis, extending its previously known geographical range in Yorkshire and Scotland southwards. These occurrences belong to Palmer’s original numbering; the latter is not silently assigned to Chidlaw’s Bed 8. They supplement, rather than replace, the fossil lists in the measured records above.

Revised range of the basal-pebble-bed brachiopod
The occurrence of Gibbirhynchia micra in quarry Bed 35 was formerly used to infer the Spinatum Zone. Records of Amaltheus subnodosus from the overlying sandstone show that the brachiopod extends below its formerly recognised range in the uppermost Gibbosus Subzone and lower Spinatum Zone. Its presence alone therefore cannot date the pebble bed to the Spinatum Zone. The sandstone ammonites also leave the Gibbosus Subzone unproved locally.

Ostracods: Lord’s 1974 local sample results
Only three of 24 Robin’s Wood Hill samples yielded ostracods. Lord considered weathering of the face a probable contributor, while not excluding naturally low diversity. The account supplies no local sample identifiers.

Upper Davoei Zone
The recorded ostracods were Wicherella semiora semiora and Ogmoconcha sp. B.

Stokesi Subzone
Lord recorded Wicherella semiora semiora, Ogmoconcha sp. B, Gramannella apostolescui, Trachycythere tubulosa ?seratina, and two unnamed new cytherurid species. The question mark and unnamed status are retained. Gloucester’s Toarcian beds were not sampled; these results do not describe the higher hill’s entire microfauna.

Historical thicknesses in the ammonite-zone correlation
Palmer assigned 7.7 m of his beds 9b–c to the Figulinum Subzone. After finding additional ammonites, Phelps placed Palmer’s nodule beds 9c and 9e, with a reported 2.74 m of intervening silty mudstones, in that subzone. The later quarry table records 5.49 m for its Bed 15 between the corresponding nodule horizons. These are distinct published measurements and correlation schemes; the differences are not resolved by substituting one number for another.

Palmer’s 1971 Tuffley section: original imperial measurements
The following is the Tuffley-only log at SO 836149, published on pages 60–61. The immediately preceding Stonehouse table is a different locality and is not imported here. These measurements and identifications are historical, separate from Chidlaw’s later 37-bed face log. In particular, Palmer’s beds 7–9a cannot be equated confidently with individual later beds. Imperial units are retained to make the source differences visible.

LIAS GROUP

Palmer Bed 16c (4 ft)
Flaggy, fossil-rich sandstone with ferruginous ooids; Pleuroceras spinatum and Amaltheus aff. subnodosus.

Palmer Bed 16b (14 ft)
Massive sandstone, locally weathering into large rounded doggers.

Palmer Bed 16a (0–6 in)
Hard iron-rich sandy nodules, with occasional Gibbirhynchia micra.

Erosion surface and abrupt lithological change
Palmer placed this below his Bed 16a. His broad Marlstone division included beds that are now assigned to Dyrham; the modern formation boundary is explained above.

Palmer Bed 15 (17 ft)
Grey silty shale.

Palmer Bed 14 (1 ft 6 in)
Iron-rich ooidal limestone, nodular below; Amaltheus species.

Palmer Bed 13 (21 ft)
Grey silty shale.

Palmer Bed 12 (1 ft 10 in)
Iron-rich limestone with nodular base; Amaltheus stokesi, Lytoceras, bivalves and belemnites.

Palmer Bed 11 (12 ft)
Grey silty shale; the upper-working floor was about 2 ft above its base.

Palmer Bed 10 (1 ft)
Iron-rich micaceous limestone with a lower part weathering white.

Palmer’s Bed 9 package: 53 ft 6 in
The seven subdivisions below are individually recorded within this aggregate.

Palmer Bed 9g (6 ft)
Grey shale with scattered iron-rich nodules.

Palmer Bed 9f (9 ft)
Grey silty shale.

Palmer Bed 9e (3 in)
Iron-rich nodules.

Palmer Bed 9d (9 ft)
Grey silty shale.

Palmer Bed 9c (3 in)
Iron-rich nodules.

Palmer Bed 9b (25 ft)
Grey silty shale.

Palmer Bed 9a (4 ft)
Scattered iron-rich nodules; Androgynoceras capricornus, as identified in the source.

Palmer Bed 8 (4 in)
Fossil-rich ironstone nodules forming box-like structures around yellow sand; Androgynoceras.

Palmer Bed 7 (2 ft)
Sandy grey shale.

Palmer Bed 6 (apparently 2 ft 4 in–4 ft 6 in)
Prominent hard sandy shale. The printed thickness range occupies two awkwardly aligned lines; its reading remains qualified.

Palmer Bed 5 (16 ft)
Grey silty shale.

Palmer Bed 4 (6 in)
Prominent iron-rich nodule band.

Palmer’s Bed 3 package
The source describes 4–6 ft of stiff blue clay at the base and prints a total of 49 ft 6 in. Its individual listed figures below instead sum to 55 ft. This inconsistency is preserved without choosing an unsupported correction. The later GCR floor record includes only part of Bed 3c, not its full historical thickness.

Palmer Bed 3c (45 ft)
Grey silty shale, with ironstone nodules especially below.

Palmer Bed 3b (6 ft)
Sticky dark-blue clay with ironstone; Androgynoceras maculatum and abundant foraminifera and ostracods.

Palmer Bed 3a (4 ft)
Dark-grey clay passing down into silty shale.

Palmer Bed 2 (1 ft)
Hard sandy shale with crushed bivalves and Beaniceras cf. luridum.

Palmer Bed 1 (10 ft)
Grey shale with nodules, following Ager’s record; poorly exposed by Palmer’s visit.

Earlier ostracod records: Lord 1972
Lord’s earlier study gave Wicherella semiora semiora a qualified ?Davoei–Margaritatus occurrence at Gloucester, based on six carapaces and 35 valves with relatively weak ornament. He recorded a single Robin’s Wood Hill specimen of Gramannella apostolescui, with a queried Margaritatus assignment. These earlier, less precise records remain separate from the 1974 sample results. Neither genus has its holotype from this quarry.

Approximate quarry descriptions versus measured beds
The GCR narrative describes about 0.5 m of Marlstone at the top of the quarry, whereas its detailed Bed 37 measures 0.33 m. The approximate narrative figure is not an additional bed. Its roughly 29 m thickness refers to the Upper Pliensbachian Dyrham-plus-Marlstone interval under discussion, not to the full Dyrham Formation.

Palmer’s additional Tuffley bed observations
Bed 9a contained two forms of Pleuromya in life position. Bed 12 had a mauve fresh colour and pyrite, while Bed 14 displayed solution cavities with tufa coatings along joints. These are details of Palmer’s older packages, not newly resolved matches to the later log.

Capricornus interval in the 1971 interpretation
Palmer jointly described Androgynoceras lataecosta and A. artigyrus as dominant in Tuffley beds 6–8 and Stonehouse Bed 4. Tuffley Bed 9a yielded A. capricornus fragments with forward-projecting ventral ribs. He estimated the local Capricornus package at about 8 ft. These old identifications and correlations precede the revisions discussed above.

Older Marlstone fauna and zonal caution
In his joint Tuffley–Stonehouse comparison, Palmer recorded crinoid ossicles without ooids in the lower sandy material, and Lobothyris punctata, Pleuroceras spinatum and ferruginous ooids in the upper flaggy rock. He stressed that P. spinatum alone does not demonstrate the Hawskerense Subzone. These observations are not extended to the unrelated Leicestershire material discussed in the same paper.

Cardinia tuffleyensis: type material and exact historical horizon
Palmer’s 1975 revision designated the right valve BM(NH) LL31275 from his Bed 14 at Tuffley Clay Pit as holotype. The left-valve paratype LL31276 came from the same bed and locality; four further single-valve paratypes came from the equivalent Bed 10 at Stonehouse. Plate 4 identifies the Tuffley horizon as the Subnodosus Subzone of the Margaritatus Zone. “Bed 14” here means Palmer’s numbering, not Bed 14 in the later GCR table. The collection numbers follow the original publication.

Environmental interpretations from the fauna
Palmer interpreted the large filter-feeding bivalves of the coarser beds as evidence of oxygenated water and a plentiful suspended food supply. From the trochid gastropods he suggested water shallower than 100 m. The later GCR discussion used storm burial and the character of the ostracods to suggest substantially shallower conditions, possibly around 20 m or less at the time of the crinoid assemblage. These are palaeoenvironmental interpretations of particular intervals, not direct measurements or a single fixed water depth for the whole succession.

Another historical Cardinia record
Palmer’s 1975 account also lists Tuffley for Cardinia concinna, within a discussion combining many localities and horizons. It gives no exact Tuffley bed for that occurrence. This record establishes neither a local Transition Bed nor a Tuffley type specimen.

References
Simms, M. J. and Chidlaw, N. (2004), “Robin’s Wood Hill Quarry”, in Simms, Chidlaw, Morton and Page, British Lower Jurassic Stratigraphy, Geological Conservation Review 30. The measured-bed descriptions above are adapted from this JNCC account, available through GeoGuide under the Open Government Licence v3.0.
Cox, B. M., Sumbler, M. G. and Ivimey-Cook, H. C. (1999), A Formational Framework for the Lower Jurassic of England and Wales (Onshore Area), BGS Research Report RR/99/01; current BGS Lexicon entry for the Dyrham Formation.
Richardson, L. (1910), “The Neozoic rocks of Gloucestershire and Somerset”, in Geology in the Field, Geologists’ Association Jubilee Volume, pp. 329–364.
Palmer, C. P. (1971), “The stratigraphy of the Stonehouse and Tuffley clay pits, Gloucestershire”, Proceedings of the Bristol Naturalists’ Society 32, 58–68.
Palmer, C. P. (1975), The British Lower Jurassic species of the bivalve genus Cardinia, Bulletin of the British Museum (Natural History), Geology 26(1), 1–44, five plates.
Lord, A. R. (1972), “Wicherella and Gramannella, two new genera of Lower Jurassic Ostracoda from England”, Palaeontology 15, 187–196.
Lord, A. R. (1974), “Ostracods from the Domerian and Toarcian of England”, Palaeontology 17, 599–622, especially p. 603.
Palmer, C. P. (1973), “The palaeontology of the Liassic (Lower Jurassic) clay pits at Stonehouse and Tuffley in Gloucestershire”, Geological Magazine 110, 249–263.
Full GCR site account and references
BGS Dyrham Formation definition