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Lilstock Formation

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 Sedimentary features of the Cotham Member of the Lilstock Formation. (a) Plan view of cross-cutting relationships of key features within the Cotham Member, foreshore, St Audrie's Bay; db, deformed bed; cf, crack fill; wr, wave-rippled surface; sob, sandy oolitic bioclastic limestone bed. The deformed bed is overlain by a heterolith bed with small-scale wave-ripples. Both are cut by a sandy oolitic bioclastic limestone infilling the deep mudcracks. Scale bar represents 10 cm. (b) Photomicrograph of sandy oobiosparite from crack fill of major desiccation-cracked horizon, St Audrie's Bay. Scale bar represents 1 mm. (c) Symmetrical, flat-topped ripple marks and desiccation cracks, loose block but unambiguously derived from the upper Cotham Member, Lavernock. Scale bar represents 3 cm.

Sedimentary features of the Cotham Member of the Lilstock Formation. ( a ) ... Available to Purchase

Published: 01 May 2004
Fig. 7.  Sedimentary features of the Cotham Member of the Lilstock Formation. ( a ) Plan view of cross-cutting relationships of key features within the Cotham Member, foreshore, St Audrie's Bay; db, deformed bed; cf, crack fill; wr, wave-rippled surface; sob, sandy oolitic bioclastic limestone
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 Field photograph of the upper Lilstock Formation at St Audrie's Bay, west Somerset, indicating the positions of the main lithostratigraphic boundaries. One-metre stick for scale. The ‘deformed bed’ forms the prominent ledge immediately below the mudcrack horizon.

Field photograph of the upper Lilstock Formation at St Audrie's Bay, west S... Available to Purchase

Published: 01 May 2004
Fig. 6.  Field photograph of the upper Lilstock Formation at St Audrie's Bay, west Somerset, indicating the positions of the main lithostratigraphic boundaries. One-metre stick for scale. The ‘deformed bed’ forms the prominent ledge immediately below the mudcrack horizon.
Journal Article

Palaeoecology of the Late Triassic extinction event in the SW UK Available to Purchase

Luke Mander, Richard J. Twitchett, Michael J. Benton
Published: 01 January 2008
Journal of the Geological Society (2008) 165 (1): 319–332.
DOI: https://doi.org/10.1144/0016-76492007-029
... in the upper Westbury Formation to lower Lilstock Formation (late Rhaetian), but if sample size is taken into account there is little convincing evidence of a catastrophic marine extinction. There is, however, good evidence for significant palaeoecological change in the benthic marine ecosystem at this time...
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View PDF for article title, Palaeoecology of the Late Triassic extinction event in the SW UK
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Journal Article

Palynomorphs from the Penarth Group (Rhaetian, Late Triassic) at outcrop in north-west Lincolnshire, England Available to Purchase

G. Warrington
Published: 01 May 2007
Proceedings of the Yorkshire Geological Society (2007) 56 (3): 209–214.
DOI: https://doi.org/10.1144/pygs.56.3.209
... between Kettlethorpe and Thorney to be from higher levels in the Penarth Group, within the Cotham Member of the Lilstock Formation. The assemblages include spores, pollen and organic-walled microplankton that are indicative of a Rhaetian (late Late Triassic) age. The organic-walled microplankton include...
FIGURES
View PDF for article title, Palynomorphs from the Penarth Group (Rhaetian, Late Triassic) at outcrop in north-west Lincolnshire, England
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Milankovitch-scale palynological turnover across the Triassic–Jurassic transition at St. Audrie's Bay, SW UK Available to Purchase

Nina R. Bonis, Micha Ruhl, Wolfram M. Kürschner
Published: 01 September 2010
Journal of the Geological Society (2010) 167 (5): 877–888.
DOI: https://doi.org/10.1144/0016-76492009-141
...Nina R. Bonis; Micha Ruhl; Wolfram M. Kürschner Abstract: A high-resolution palynological study of the Triassic–Jurassic boundary in the St. Audrie's Bay section revealed a palynofloral transition interval with four pronounced spore peaks in the Lilstock Formation. Regular cyclic increases...
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View PDF for article title, Milankovitch-scale palynological turnover across the Triassic–Jurassic transition at St. Audrie's Bay, SW UK
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Journal Article

Sea-level change and facies development across potential Triassic–Jurassic boundary horizons, SW Britain Available to Purchase

Stephen P. Hesselbo, Stuart A. Robinson, Finn Surlyk
Published: 01 May 2004
Journal of the Geological Society (2004) 161 (3): 365–379.
DOI: https://doi.org/10.1144/0016-764903-033
...Fig. 7.  Sedimentary features of the Cotham Member of the Lilstock Formation. ( a ) Plan view of cross-cutting relationships of key features within the Cotham Member, foreshore, St Audrie's Bay; db, deformed bed; cf, crack fill; wr, wave-rippled surface; sob, sandy oolitic bioclastic limestone...
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View PDF for article title, Sea-level change and facies development across potential Triassic–Jurassic boundary horizons, SW Britain
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Journal Article

An ostracod fauna from the upper Langport Member (Penarth Group: Rhaetian, Upper Triassic) near Watchet, west Somerset (UK), including two new species of Eucytherura and Cytherelloidea praepulchella n. nom. Available to Purchase

ANDREW SWIFT
Published: 01 November 2003
Journal of Micropalaeontology (2003) 22 (2): 127–136.
DOI: https://doi.org/10.1144/jm.22.2.127
...ANDREW SWIFT Abstract An abundant ostracod fauna consisting of just five species is described from the upper part of the Langport Member of the Lilstock Formation of the Penarth Group (Rhaetian, Late Triassic) near Watchet, west Somerset. The fauna is dominated by Ogmoconchella bristolensis...
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View PDF for article title, An ostracod fauna from the upper Langport Member (Penarth Group: Rhaetian, Upper Triassic) near Watchet, west Somerset (UK), including two new species of Eucytherura and Cytherelloidea praepulchella n. nom.
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Add to Citation Manager for An ostracod fauna from the upper Langport Member (Penarth Group: Rhaetian, Upper Triassic) near Watchet, west Somerset (UK), including two new species of Eucytherura and Cytherelloidea praepulchella n. nom.
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Changes in the size–frequency distributions of the body sizes of infaunal, semi-infaunal, and epifaunal bivalves through the Triassic–Jurassic of the United Kingdom. A, Westbury Formation (WF); B, Cotham Member (CM; Lilstock Formation); C, Langport Member (LM; Lilstock Formation); D, pre-Planorbis Zone (PPZ); E, Planorbis Zone (PZ); F, Liasicus Zone (LZ); G, Angulata Zone (AZ). The fitting of each curve is based on a combination of kernel density estimation and smoothed bootstrap resampling using bin sizes of 0.25 on a log2 scale. All distributions are unimodal but with highly variable skewed frequency distributions. H, Changes in the weighted marginal geometric mean values (±SE) for each tier through time.

Changes in the size–frequency distributions of the body sizes of infaunal, ... Available to Purchase

Published: 01 August 2022
Figure 6. Changes in the size–frequency distributions of the body sizes of infaunal, semi-infaunal, and epifaunal bivalves through the Triassic–Jurassic of the United Kingdom. A, Westbury Formation (WF); B, Cotham Member (CM; Lilstock Formation); C, Langport Member (LM; Lilstock Formation); D
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Statistical descriptors of the body size distributions (BSDs) of the bivalv... Available to Purchase

Published: 01 August 2022
. WF, Westbury Formation; CM, Cotham Member (Lilstock Formation); LM, Langport Member (Lilstock Formation); and Blue Lias Formation ammonite zones: PPZ, pre-Planorbis Zone; PZ, Planorbis Zone; LZ, Liasicus Zone; AZ, Angulata Zone. WF CM LM PPZ PZ LZ AZ Number of species 17
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The clay mineral stratigraphy of the Triassic succession in the Stowell Park Borehole (SP084118). The stratigraphical scheme used by Jeans (1978) is shovm. S.S. Grp – Sherwood Sandstone Group; P. Grp – Penarth Group; A.S. Fm. – Arden Sandstone Formation; B.A. Fm. – Blue Anchor Formation; W. Fm. – Westbury Formation; L. Fm. – Lilstock Formation; TOM – Tea Green Marl.

The clay mineral stratigraphy of the Triassic succession in the Stowell Par... Available to Purchase

Published: 01 March 2006
Formation; W. Fm. – Westbury Formation; L. Fm. – Lilstock Formation; TOM – Tea Green Marl.
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Enlargement of the relative terrestrial palynomorph abundances and concentrations in relation to the δ13Corg record and the lithology from the spore peak interval in the Lilstock Formation. The shaded portion of the curves is a 5× exaggeration of the abundances plotted in black. Spore peaks are numbered (see Fig. 2). The height (m) is relative to the base of the Williton Member (0 m).

Enlargement of the relative terrestrial palynomorph abundances and concentr... Available to Purchase

Published: 01 September 2010
Fig. 4. Enlargement of the relative terrestrial palynomorph abundances and concentrations in relation to the δ 13 C org record and the lithology from the spore peak interval in the Lilstock Formation. The shaded portion of the curves is a 5× exaggeration of the abundances plotted in black. Spore
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Composite clay mineral stratigraphy of the Triassic succession in the Leicester and Nottingham region based upon analyses from various boreholes (Jeans, 1978; Bloodworm & Prior, 1993; Kemp, 1999) and surface exposures (Jeans, 1978). The stratigraphical schemes used by those authors are shown, (a) P. Grp – Penarth Group; A.S. Fm. – Arden Sandstone Formation; B.A. Fm. – Blue Anchor Formation; W. Fm. – Westbury Formation; L. Fm. – Lilstock Formation; C.S. Mbr – Cotgrave Skerry Member; H.S. Mbr – Hollygate Skerry Member.

Composite clay mineral stratigraphy of the Triassic succession in the Leice... Available to Purchase

Published: 01 March 2006
authors are shown, (a) P. Grp – Penarth Group; A.S. Fm. – Arden Sandstone Formation; B.A. Fm. – Blue Anchor Formation; W. Fm. – Westbury Formation; L. Fm. – Lilstock Formation; C.S. Mbr – Cotgrave Skerry Member; H.S. Mbr – Hollygate Skerry Member.
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Figure 2.

(a) Synsedimentary tectonics within the base of the Blue Lias Formation at ... Available to Purchase

Published: 26 October 2015
the Cotham Member of the Lilstock Formation on the foreshore of St Audrie's Bay. (c) Soft sediment deformation within the base of the Blue Lias Formation at Pinhay Bay (close to Lyme Regis). Compare figure 3 of Wignall ( 2001 b ). (d) Calcareous
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Geology of the study area. (a) Simplified geological map of the study area with Triassic strata shown in detail. Based on British Geological Survey map data. The diagonal lines show which parts of the study area are not mapped by the onshore geology map used for the study. (b) Late Triassic to earliest Jurassic stratigraphy of the Bristol area based on the British Geological Survey stratigraphic framework. (c) Simplified diagram showing the unconformable relationship between Mesozoic and Paleozoic strata in the study area. The red arrows indicate successive sea levels, from low to high from the top of the Blue Anchor Formation, through Westbury Formation times and into the early Lilstock Formation. DC = Dolomitic Conglomerate, marginal facies of the MMG.

Geology of the study area. ( a ) Simplified geological map of the study are... Available to Purchase

Published: 25 February 2021
to high from the top of the Blue Anchor Formation, through Westbury Formation times and into the early Lilstock Formation. DC = Dolomitic Conglomerate, marginal facies of the MMG.
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Abundances (µg/g sediments; n.d.—not detected) of biomarkers. A: For Chlorobi, which uses H2S for anoxygenic photosynthesis and indicates photic zone euxinia. B, C: For algae. D: For leaf waxes. Unfilled symbols have overmature organic matter based on Rock-Eval pyrolysis data (Table DR1; Fig. DR2; see footnote 1). E: Molecular proxy records: pristane/phytane (Pr/Ph) < 1.0 indicates anoxia; aryl isoprenoid ratio (AIR) < 0.75 reflects persistent photic zone euxinia (Schwark and Frimmel, 2004). (For sample details and stratigraphy, see the Data Repository [see footnote 1].) Lil—Lilstock Formation; C—Cotham Member; L—Langport Member; A—Angulata zone; PPZ—Pre-Planorbis zone; TJB—Triassic-Jurassic boundary; CIE—initial carbon isotope excursion; LTE—Late Triassic extinction.

Abundances (µg/g sediments; n.d.—not detected) of biomarkers. A: For Chloro... Available to Purchase

Published: 01 September 2013
].) Lil—Lilstock Formation; C—Cotham Member; L—Langport Member; A—Angulata zone; PPZ—Pre-Planorbis zone; TJB—Triassic-Jurassic boundary; CIE—initial carbon isotope excursion; LTE—Late Triassic extinction.
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 Graphic log of the Tr–J boundary interval at St Audrie's Bay, Somerset. Magnetostratigraphy from Hounslow et al. 2001; M. W. Hounslow, in press.; boundary definitions according to George et al. (1969), Orbell (1973), Poole (1979, 1980, 1991), Hallam (1990, 1995) and Warrington et al. (1994). Spore and pollen and dinoflagellate zones follow Orbell (1973), Woollam & Riding (1983) and Hesselbo et al. (2002). Conodont data from Swift (1999, pers. comm.). Ammonites from Warrington & Ivimey-Cook (1995) and Bloos & Page (2000). Westbury Formation and Cotham Member bed numbers from Richardson (1911). Lilstock Formation–Blue Lias Formation boundary after Whittaker (1978). Method for geochemical data as given by Hesselbo et al. (2003); most samples collected for geochemical analysis were excavated from the foreshore and all are unweathered. Sequence stratigraphy, this study. RSLC, relative sea-level change; TST, transgressive systems tract; FSST, falling stage systems tract; LST, lowstand systems tract; SB, sequence boundary.

Graphic log of the Tr–J boundary interval at St Audrie's Bay, Somerset. Mag... Available to Purchase

Published: 01 May 2004
and Cotham Member bed numbers from Richardson (1911) . Lilstock Formation–Blue Lias Formation boundary after Whittaker (1978) . Method for geochemical data as given by Hesselbo et al . (2003) ; most samples collected for geochemical analysis were excavated from the foreshore and all are unweathered
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Correlation of Corg isotope records and biotic events between Stenlille (Danish Basin; this paper) and St. Audrie's Bay (UK; Bonis et al., 2010; Mander et al., 2008) and Doniford (UK; Clémence et al., 2010). Ammonite events correlate St. Audrie's Bay and Doniford. First occurrence (FO) of Cerebropollenites thiergartii (marked D) ∼3 m below FO of ammonite Psiloceras planorbis at St. Audrie's Bay (Bonis et al., 2010) probably does not represent its FO datum, as it initially tends to be very rare even in terrestrial sections. FO of C. thiergartii just prior to Neg-II at Stenlille indicates location of Triassic-Jurassic boundary within Langport Member (Lilstock Formation). Rhaetian spore and/or pollen taxa include Limbosporites lundbladiae, Lunatisporites rhaeticus, Rhaetipollis germanicus, and Semiretisporis gothae. LO—last occurrence; LCO—last common or consistent occurrence; FCO—first common or consistent occurrence; MFS—maximum flooding surface; VPDB—Vienna Peedee belemnite; B.A. Fm—Blue Anchor Formation; siltst.—siltstone; clay/siltstone—clay and siltstone.

Correlation of C org isotope records and biotic events between Stenlille (... Available to Purchase

Published: 01 June 2012
at Stenlille indicates location of Triassic-Jurassic boundary within Langport Member (Lilstock Formation). Rhaetian spore and/or pollen taxa include Limbosporites lundbladiae , Lunatisporites rhaeticus , Rhaetipollis germanicus , and Semiretisporis gothae . LO—last occurrence; LCO — last common
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A: Isotopically enriched isorenieratane and aryl isoprenoids δ13C profile. B: Isoprenoid hydrocarbons of algal markers δ13C profile. C: Alkyl hydrocarbons of algal markers δ13C profile. D: Offset (ave—average; pr—pristane; ph—phytane; auto—autotrophs; hetero—heterotrophs). E: Leaf waxes with average of –31‰ in dotted vertical lines. F: Kerogen OM (organic matter) and carbonate. G: Total and pyrite δ34S (‰, relative to VCDT, Vienna Canyon Diablo troilite). H: pCO2 estimates from leaf stomatal studies (McElwain et al., 1999). I: Bulk carbon isotopes of marine (UK) (Hesselbo et al., 2002) and terrestrial (Austria) (Bonis et al., 2010) sections. Lil—Lilstock Formation; C—Cotham Member; L—Langport Member; A—Angulata zone; PPZ—Pre-Planorbis zone; TJB—Triassic-Jurassic boundary; CIE—initial carbon isotope excursion; LTE—Late Triassic extinction.

A: Isotopically enriched isorenieratane and aryl isoprenoids δ 13 C profile... Available to Purchase

Published: 01 September 2013
) ( Hesselbo et al., 2002 ) and terrestrial (Austria) ( Bonis et al., 2010 ) sections. Lil—Lilstock Formation; C—Cotham Member; L—Langport Member; A—Angulata zone; PPZ—Pre-Planorbis zone; TJB—Triassic-Jurassic boundary; CIE—initial carbon isotope excursion; LTE—Late Triassic extinction.
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figs 1–14.Cytherelloidea praepulchella n. nom.: 1, MPK 13049, left valve, lateral view; 2, MPK 13050, left valve, lateral view; 3, MPK 13051, carapace, ventral view; 4, MPK 13052, right valve, lateral view; 5, MPK 13053, right valve, lateral view; 6, MPK 13054, right valve, internal view; 7, MPK 13055, left valve, ventro-lateral view; 8, MPK 13056, left valve, dorso-lateral view; 9, MPK 13057, right valve, internal view; 10, 13, MPK 13058, left valve, lateral and ventro-lateral views; 11, 14, MPK 13059, right valve, lateral and dorso-lateral views; 12, MPK 13060, left valve, internal view. All specimens from the base of the upper Langport Member, Lilstock Formation, Penarth Group (Rhaetian, Late Triassic), near Watchet, Somerset. All ×100. Repository of specimens: collections of the British Geological Survey, Keyworth, Nottingham, UK.

figs 1 – 14. Cytherelloidea praepulchella n. nom.: 1 , MPK 13049, left v... Available to Purchase

Published: 01 November 2003
-lateral views; 12 , MPK 13060, left valve, internal view. All specimens from the base of the upper Langport Member, Lilstock Formation, Penarth Group (Rhaetian, Late Triassic), near Watchet, Somerset. All ×100. Repository of specimens: collections of the British Geological Survey, Keyworth, Nottingham
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figs 1–4. Cytherella plattensis Anderson: 1, MPK 13061, right valve, lateral view; 2, MPK 13062, left valve, lateral view; 3, MPK 13063, right valve, internal view; 4, MPK 13064, left valve, internal view. Figs 5–12.Ogmoconchella bristolensis (Anderson): 5, MPK 13065, carapace, right lateral view; 6, MPK 13066, left valve, lateral view; 7, MPK 13067, left valve, lateral view; 8, MPK 13068, right valve, lateral view, close up of anterior lip; 9, MPK 13069, right valve, lateral view; 10, MPK 13070, right valve, lateral view; 11, MPK 13071, right valve, lateral view showing wrinkled ornament in dorsal area; 12, MPK 13072, left valve, internal view. All specimens from the base of the upper Langport Member, Lilstock Formation, Penarth Group (Rhaetian, Late Triassic), near Watchet, Somerset. All ×100, except fig. 8 ×250. Repository of specimens: collections of the British Geological Survey, Keyworth, Nottingham, UK.

figs 1 – 4 . Cytherella plattensis Anderson: 1 , MPK 13061, right valve,... Available to Purchase

Published: 01 November 2003
, right valve, lateral view showing wrinkled ornament in dorsal area; 12 , MPK 13072, left valve, internal view. All specimens from the base of the upper Langport Member, Lilstock Formation, Penarth Group (Rhaetian, Late Triassic), near Watchet, Somerset. All ×100, except fig. 8 ×250. Repository