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Blue Lias Formation

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Journal Article
Published: 30 January 2017
Geological Magazine (2018) 155 (5): 1117–1149.
...GRAHAM P. WEEDON; HUGH C. JENKYNS; KEVIN N. PAGE Abstract – Lithostratigraphic and magnetic-susceptibility logs for four sections in the Blue Lias Formation are combined with a re-assessment of the ammonite biostratigraphy. A Shaw plot correlating the West Somerset coast with the Devon/Dorset coast...
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Journal Article
Published: 17 December 2018
Geological Magazine (2019) 156 (9): 1469–1509.
...Graham P. Weedon; Kevin N. Page; Hugh C. Jenkyns Abstract The lithostratigraphic characteristics of the iconic Blue Lias Formation of southern Britain are influenced by sedimentation rates and stratigraphic gaps. Evidence for regular sedimentary cycles is reassessed using logs of magnetic...
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Journal Article
Published: 01 November 2007
Proceedings of the Yorkshire Geological Society (2007) 56 (4): 253–260.
...A. S. Smith; J. D. Radley SUMMARY A previously undocumented marine reptile fauna comprising well-preserved ichthyosaur and plesiosaur remains is described from the Early Jurassic Saltford Shale Member within the Blue Lias Formation of central England. Two ichthyosaur genera are recognized, namely...
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Figure 2.
Published: 26 October 2015
Figure 2. (a) Synsedimentary tectonics within the base of the Blue Lias Formation at Pinhay Bay (close to Lyme Regis). Compare figure 3 of Wignall ( 2001 b ). Small polygonal fault sets leading to soft-sediment deformation. (b) Slump folds within
Journal Article
Journal: Geology
Published: 05 January 2022
Geology (2022) 50 (4): 448–453.
... (acidification) driven by Central Atlantic magmatic province (CAMP) activity formed a two-pronged kill mechanism at the end-Triassic mass extinction. In a newly proposed extinction interval for the basal Blue Lias Formation (Bristol Channel Basin, UK), biomarker distributions reveal an episode of persistent...
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Series: Geological Society, London, Special Publications
Published: 12 July 2024
DOI: 10.1144/SP543-2023-42
EISBN: 9781786206404
... Abstract The cliffs and foreshore at Lyme Regis on the Dorset coast expose a sequence of Early Jurassic marine limestones and mudstones of the Blue Lias Formation and the overlying Charmouth Mudstone Formation, the lowest units of the Hettangian–Aalenian Lias Group. Known for its fossils since...
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Journal Article
Published: 01 April 1980
Journal of the Geological Society (1980) 137 (2): 157–170.
...K. A. Morris Abstract The British Jurassic contains 3 major sequences of organic-rich shales: the Jet Rock Formation (Lower Toarcian), the Lower Oxford Clay (Callovian), and the Kimmeridge Clay (Kimmeridgian). In addition minor sequences are found in the Blue Lias Formation and the Shales-with-Beef...
Journal Article
Published: 01 May 1990
Journal of the Geological Society (1990) 147 (3): 421–424.
.... The boundary is placed at the base of the Blue Lias Formation. References Blind W. Die Ammoniten des Lias alpha aus Schwaben, von Fonsjoch und Breitenberg (Alpen) und ihre Entwicklung Palaeontographica 1963 38 131 121A Bown, P. R. & Lord, A. R. 1990. The occurrence of calcareous...
Journal Article
Journal: Geology
Published: 01 July 1986
Geology (1986) 14 (7): 609–612.
... to climatic variations affected by “Milankovitch” orbital cycles. A test is proposed and illustrated mainly with reference to the Blue Lias Formation of Dorset, England, that appears to indicate that many limestones can be produced solely by rhythmic unmixing of CaCO 3 during diagenesis. Unless...
Journal Article
Published: 01 December 1985
Journal of the Geological Society (1985) 142 (6): 995–1006.
...M. W. Hounslow Abstract The magnetic fabric of mudrock samples from the Westbury Member of the Penarth Group (Rhaetian), the Blue Lias Formation (Hettangian to Sinemurian) and the Oxford Clay (Callovian to Oxfordian) has been measured, using a high field torque magnetometer. The magnetic...
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SEM images showing typical features of Lias Group mudstones. (a) Tightly packed, flat-lying, curved clay flakes, typically ~10 μm in diameter and <1 μm thick. Minor framboidal pyrite is present near the bottom of the image (Whitby Mudstone Formation, Cleveland Basin). (b) A cluster of pyrite framboids within a microfracture that cuts an otherwise well-laminated mudstone (Charmouth Mudstone Formation, East Midlands Shelf (north)). (c) Well laminated, tightly packed, flat-lying clay flakes with minor silt-sized grains (Blue Lias Formation, Worcester Basin). (d) Carbonate-rich mudstone containing very abundant, microcrystalline rhombs of calcite (A). A pyrite framboid is engulfed by authigenic clay at (B). (Blue Lias Formation, Wessex Basin).
Published: 01 March 2005
of pyrite framboids within a microfracture that cuts an otherwise well-laminated mudstone (Charmouth Mudstone Formation, East Midlands Shelf (north)). (c) Well laminated, tightly packed, flat-lying clay flakes with minor silt-sized grains (Blue Lias Formation, Worcester Basin). (d) Carbonate-rich mudstone
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Representative XRD traces of <2 μm separates, (a) Redcar Mudstone Formation, Cleveland Basin, (b) Blue Lias Formation, East Midland Shelf.
Published: 01 March 2005
F ig . 6. Representative XRD traces of <2 μm separates, (a) Redcar Mudstone Formation, Cleveland Basin, (b) Blue Lias Formation, East Midland Shelf.
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Outline lithostratigraphy and biostratigraphy of the Lower Jurassic Blue Lias Formation, Warwickshire, England. Chronozones are indicated in the left-hand column. P = Planorbis; L = Liasicus; A = Angulata; B = Bucklandi.
Published: 01 November 2007
Fig. 2. Outline lithostratigraphy and biostratigraphy of the Lower Jurassic Blue Lias Formation, Warwickshire, England. Chronozones are indicated in the left-hand column. P = Planorbis; L = Liasicus; A = Angulata; B = Bucklandi.
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Figure 8. Paleocommunity reconstructions for the Lower Jurassic comparing A) the silicified fauna against B) the typical Blue Lias Formation fauna. Note the complete loss of shallow infaunal bivalves and reduction in epifaunal gastropods, leaving only a few in situ deep-burrowing bivalves with the calcitic-bimineralic large pteriomorph assemblage of B.
Published: 01 November 2009
Figure 8. Paleocommunity reconstructions for the Lower Jurassic comparing A) the silicified fauna against B) the typical Blue Lias Formation fauna. Note the complete loss of shallow infaunal bivalves and reduction in epifaunal gastropods, leaving only a few in situ deep-burrowing bivalves
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(a–c) Shaw plots based on the positions of the biohorizon boundaries on the tuned time scales relative to the local base of the Blue Lias Formation: (a) Lyme Regis versus West Somerset; (b) Lavernock versus Lyme Regis; (c) Lavernock versus West Somerset. Note that for each location the base of the tuned time scale is the base of the Blue Lias Formation (i.e. within the uppermost Rhaetian, Triassic). In (a) and (c) the vertical arrows emerging from the West Somerset axis and projected horizontally onto the Lyme Regis axis show the implied positions of the base of the Tilmanni Zone and the base of the Angulata Zone according to the composite time scale (Section 9.b). The uncertainty in the positions of the biohorizon limits (i.e. tops and bases) is indicated using grey vertical and horizontal bars associated with each plotted point. (d–f) Shaw plots based on the positions of the biohorizon boundaries on the composite time scale relative to the base or inferred base of the Jurassic (base of the Hettangian Stage): (d) Lyme Regis versus West Somerset; (e) Lavernock versus Lyme Regis; (f) Lavernock versus West Somerset. The base of the composite time scale is the base of the Jurassic (base of Hn1). The vertical long grey arrow emerging from the West Somerset axis and projected horizontally to the Lyme Regis axis indicates the inferred location of the base of the Angulata Zone. The uncertainty in the positions of the ‘independent’ biohorizon limits are indicated using black vertical and horizontal bars. All plotted data are listed in Tables 1–3. Ma – million years. Abbreviations for subzones: Plan. – Planorbis; John. – Johnstoni; Port. and P – Portlocki; L. – Laqueus; Ext. and Ex. – Extranodosa; Depr. and Dep. – Depressa; Conyb. and Cony. – Conybeari. Abbreviations for zones: Tilman – Tilmanni; Lias, L – Liasicus; Buckl. – Bucklandi.
Published: 17 December 2018
Fig. 13. (a–c) Shaw plots based on the positions of the biohorizon boundaries on the tuned time scales relative to the local base of the Blue Lias Formation: (a) Lyme Regis versus West Somerset; (b) Lavernock versus Lyme Regis; (c) Lavernock versus West Somerset. Note that for each location
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Compound-specific carbon isotope analysis at St. Audrie's Bay (circles, solid lines) and Lilstock (squares, dashed lines) in the Bristol Channel Basin, UK. Two depositional environments are indicated by green (variable but negative excursions in regular isoprenoids and n-alkanes) and pink (positive excursions and shift to more autotrophy) bars. Biomarkers are below, and ecological indicators are above, each profile. δ13C of biomarkers to the base of the Blue Lias Formation were reported by Fox et al. (2020). Details are provided in the Supplemental Material (see footnote 1). ETE—End-Triassic extinction; TOC—total organic carbon.
Published: 05 January 2022
) and pink (positive excursions and shift to more autotrophy) bars. Biomarkers are below, and ecological indicators are above, each profile. δ 13 C of biomarkers to the base of the Blue Lias Formation were reported by Fox et al. (2020) . Details are provided in the Supplemental Material (see footnote 1
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 (a) Facies relationships in the cliffline between Pant-y-Slade and Temple Bay derived from field sketches and photo-montage interpretation. m, the ‘basal marl’ of Hallam (1960); h, the bored hardground dividing the Sutton Stone at Pant-y-Slade. Letters (A)–(C) refer to the platform divisions of Fletcher (1988). (b) Sequence-stratigraphic architecture recognized from facies relationships in (a). Numbers 1–4 refer to parasequence ‘packages’ as identified between Black Rocks and Dancing Stones; letters [A]–[D] refer to the packages identified in the Trwyn-y-Witch succession. BLS, undifferentiated Blue Lias Formation. Representation is diagrammatic with significant vertical exaggeration, and not to scale.
Published: 01 July 2006
succession. BLS, undifferentiated Blue Lias Formation. Representation is diagrammatic with significant vertical exaggeration, and not to scale.
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Biomarker-inferred redox and photic zone euxinia (PZE) conditions at St. Audrie's Bay (circles, solid lines) and Lilstock (squares, dashed lined) in the Bristol Channel Basin, UK, relative to δ13Corg and total organic carbon (TOC). Two depositional environments are indicated by green (shallow redoxcline) and pink (deeper chemocline) bars. Biomarkers are below, and ecological indicators are above, each profile. Pristane to phytane ratios and gammacerane, okenane (Oke), chlorobactane (Chlo), and isorenieratane (Iso) indices up to the base of the Blue Lias Formation were reported by Fox et al. (2020). Details are provided in the Supplemental Material (see footnote 1). VPDB—Vienna Peedee belemnite; ETE—End-Triassic extinction.
Published: 05 January 2022
by green (shallow redoxcline) and pink (deeper chemocline) bars. Biomarkers are below, and ecological indicators are above, each profile. Pristane to phytane ratios and gammacerane, okenane (Oke), chlorobactane (Chlo), and isorenieratane (Iso) indices up to the base of the Blue Lias Formation were reported
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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 &amp; Riding (1983) and Hesselbo et al. (2002). Conodont data from Swift (1999, pers. comm.). Ammonites from Warrington &amp; Ivimey-Cook (1995) and Bloos &amp; 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.
Published: 01 May 2004
and Cotham Member bed numbers from Richardson (1911) . Lilstock FormationBlue 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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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