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Birchi Bed

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Journal Article

A note on the Birchi Beds, Lower Jurassic, at Lyme Regis, Dorset

C. P. Palmer
Published: 01 November 1984
Geological Magazine (1984) 121 (6): 645–647.
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Image
Stratigraphic position of the zoned concretions from the Birchi Bed in the Lower Lias of Dorset. Vertical scale in metres.

Stratigraphic position of the zoned concretions from the Birchi Bed in the ...

Published: 01 January 2000
Fig. 1. Stratigraphic position of the zoned concretions from the Birchi Bed in the Lower Lias of Dorset. Vertical scale in metres.
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Sampling of the zoned nodular Birchi Bed concretion. CC1/2/3, DLZ1/2/3, OCR1/2/3 refer to the samples taken from the calcitic core, intermediate dolomitic zone and outer calcitic rim respectively. CIC1–3 and FC1–3 refer to samples from the cone‐in‐cone calcites and fibrous calcites I (Marshall 1982) of the fibrous calcite layer.

Sampling of the zoned nodular Birchi Bed concretion. CC1/2/3, DLZ1/2/3, OCR...

Published: 01 January 2000
Fig. 2. Sampling of the zoned nodular Birchi Bed concretion. CC1/2/3, DLZ1/2/3, OCR1/2/3 refer to the samples taken from the calcitic core, intermediate dolomitic zone and outer calcitic rim respectively. CIC1–3 and FC1–3 refer to samples from the cone‐in‐cone calcites and fibrous calcites I
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(a) Transmitted light micrograph of the calcitic core of the Birchi Bed concretion (horizontal field of view = 2.9 mm). The greyish microspar calcitic cement dominates the field of view. The origin of the mottling is not clear. It may reflect patchy nucleation of the carbonate in very uncompacted sediment. The structureless lens (top‐left) is a spar filled microfossil. The long (&lt;1 cm) string of organic matter at the middle‐right could be a woody fragment, but the majority of organic matter is structureless and is scattered randomly throughout the matrix of the concretion. (b) Backscattered scanning electron photomicrograph of the calcitic core of the Birchi Bed concretion. The core consists almost exclusively of anhedral interlocking diagenetic calcitic crystals (C). Organic matter (OM), detrital quartz grains (Q), clay minerals (cl) and framboidal pyrite (FPy) are scattered within the calcitic body of the concretion. Horizontal field of view is 45 μm.

( a ) Transmitted light micrograph of the calcitic core of the Birchi Bed c...

Published: 01 January 2000
Fig. 3. ( a ) Transmitted light micrograph of the calcitic core of the Birchi Bed concretion (horizontal field of view = 2.9 mm). The greyish microspar calcitic cement dominates the field of view. The origin of the mottling is not clear. It may reflect patchy nucleation of the carbonate in very
Image
(a) Transmitted light micrograph of the calcitic core of the Birchi Bed concretion (horizontal field of view = 2.9 mm). The greyish microspar calcitic cement dominates the field of view. The origin of the mottling is not clear. It may reflect patchy nucleation of the carbonate in very uncompacted sediment. The structureless lens (top‐left) is a spar filled microfossil. The long (&lt;1 cm) string of organic matter at the middle‐right could be a woody fragment, but the majority of organic matter is structureless and is scattered randomly throughout the matrix of the concretion. (b) Backscattered scanning electron photomicrograph of the calcitic core of the Birchi Bed concretion. The core consists almost exclusively of anhedral interlocking diagenetic calcitic crystals (C). Organic matter (OM), detrital quartz grains (Q), clay minerals (cl) and framboidal pyrite (FPy) are scattered within the calcitic body of the concretion. Horizontal field of view is 45 μm.

( a ) Transmitted light micrograph of the calcitic core of the Birchi Bed c...

Published: 01 January 2000
Fig. 3. ( a ) Transmitted light micrograph of the calcitic core of the Birchi Bed concretion (horizontal field of view = 2.9 mm). The greyish microspar calcitic cement dominates the field of view. The origin of the mottling is not clear. It may reflect patchy nucleation of the carbonate in very
Image
A schematic illustrating the revised model for the origin of the Birchi Bed concretionary carbonates.

A schematic illustrating the revised model for the origin of the Birchi Bed...

Published: 01 January 2000
Fig. 16. A schematic illustrating the revised model for the origin of the Birchi Bed concretionary carbonates.
Journal Article

Biomarkers in a Lower Jurassic concretion from Dorset (UK)

K. KIRIAKOULAKIS, J. D. MARSHALL, G. A. WOLFF
Published: 01 January 2000
Journal of the Geological Society (2000) 157 (1): 207–220.
DOI: https://doi.org/10.1144/jgs.157.1.207
...Fig. 1. Stratigraphic position of the zoned concretions from the Birchi Bed in the Lower Lias of Dorset. Vertical scale in metres. ...
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Concentrations of total hydrocarbons and TOC contents (relative to the IR) of the Birchi Bed concretion, the fibrous calcite vein and the shales above and below the concretion.

Concentrations of total hydrocarbons and TOC contents (relative to the IR) ...

Published: 01 January 2000
Fig. 13. Concentrations of total hydrocarbons and TOC contents (relative to the IR) of the Birchi Bed concretion, the fibrous calcite vein and the shales above and below the concretion.
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10‐Methylhexadecanoic acid as a percentage the total alkanoic acids of the Birchi Bed concretion, the fibrous calcite vein and the shales above and below the concretion.

10‐Methylhexadecanoic acid as a percentage the total alkanoic acids of the ...

Published: 01 January 2000
Fig. 15. 10‐Methylhexadecanoic acid as a percentage the total alkanoic acids of the Birchi Bed concretion, the fibrous calcite vein and the shales above and below the concretion.
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Stable isotopic composition (δ13C, δ18O) of the carbonates of the Birchi Bed concretion and the fibrous calcite vein analysed for this study.

Stable isotopic composition (δ 13 C, δ 18 O) of the carbonates of the Birch...

Published: 01 January 2000
Fig. 8. Stable isotopic composition (δ 13 C, δ 18 O) of the carbonates of the Birchi Bed concretion and the fibrous calcite vein analysed for this study.
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Concentrations of total saturated and unsaturated fatty acids (relative to the insoluble residue) of the Birchi Bed concretion, the beef calcites and the shales above and below the concretion.

Concentrations of total saturated and unsaturated fatty acids (relative to ...

Published: 01 January 2000
Fig. 14. Concentrations of total saturated and unsaturated fatty acids (relative to the insoluble residue) of the Birchi Bed concretion, the beef calcites and the shales above and below the concretion.
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Representative total ion current chromatogram (TIC) of fatty acids (as TMS derivatives) of the Birchi Bed concretion. For peak notation refer to Fig. 10. The filled rectangle is 10‐methylhexadecanoic acid.

Representative total ion current chromatogram (TIC) of fatty acids (as TMS ...

Published: 01 January 2000
Fig. 11. Representative total ion current chromatogram (TIC) of fatty acids (as TMS derivatives) of the Birchi Bed concretion. For peak notation refer to Fig. 10. The filled rectangle is 10‐methylhexadecanoic acid.
Image
Transmitted light micrograph of the cone‐in‐cone calcites, which envelop the Birchi Bed concretion. Horizontal field of view is 2.9 mm. The development of the cones is apparent. Some organic matter has been trapped between the crystals.

Transmitted light micrograph of the cone‐in‐cone calcites, which envelop th...

Published: 01 January 2000
Fig. 7. Transmitted light micrograph of the cone‐in‐cone calcites, which envelop the Birchi Bed concretion. Horizontal field of view is 2.9 mm. The development of the cones is apparent. Some organic matter has been trapped between the crystals.
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Relationship between dolomite contents and (a) carbon and (b) oxygen isotopic values of the Birchi Bed concretion respectively. The r2 values indicate strong correlation between the amount of dolomite (non‐displacive sample; see text) and the stable isotopic values of the concretion.

Relationship between dolomite contents and ( a ) carbon and ( b ) oxygen is...

Published: 01 January 2000
Fig. 9. Relationship between dolomite contents and ( a ) carbon and ( b ) oxygen isotopic values of the Birchi Bed concretion respectively. The r 2 values indicate strong correlation between the amount of dolomite (non‐displacive sample; see text) and the stable isotopic values of the concretion.
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(a) Backscattered scanning electron micrograph of the dolomitic zone. Dolomite crystals (D) are subhedral‐to‐rhombohedral and they often have dissolved centres. Lighter grey, anhedral calcite crystals (C) also exist but their temporal relationship with the dolomitic crystals is not clear. In contrast to the calcitic core, there is abundant euhedral (EPy) together with framboidal (FPy) pyrite. Clay minerals (cl) and organic matter are also scattered between the carbonate crystals of the concretion. Horizontal field of view is 45 μm. (b) Backscattered scanning electron micrograph of the outer rim of the Birchi Bed concretion. Dolomite crystals (D) are rhombohedral and they often have dissolved centres (as in the dolomitic zone). Their zonation is apparent and probably reflects fluctuations in the iron content of the pore waters. Some anhedral calcite crystals (C) exist in higher abundance than in the dolomitic zone and in some cases, they seem to envelop the dolomitic rhombs (thick arrow). There is also some framboidal pyrite (FPy) also exists. Clay minerals (cl), organic matter (OM) and some quartz (Q) are also scattered between the carbonate crystals of the concretion. Horizontal field of view is 50 μm.

( a ) Backscattered scanning electron micrograph of the dolomitic zone. Dol...

Published: 01 January 2000
of the outer rim of the Birchi Bed concretion. Dolomite crystals (D) are rhombohedral and they often have dissolved centres (as in the dolomitic zone). Their zonation is apparent and probably reflects fluctuations in the iron content of the pore waters. Some anhedral calcite crystals (C) exist in higher
Image
(a) Backscattered scanning electron micrograph of the dolomitic zone. Dolomite crystals (D) are subhedral‐to‐rhombohedral and they often have dissolved centres. Lighter grey, anhedral calcite crystals (C) also exist but their temporal relationship with the dolomitic crystals is not clear. In contrast to the calcitic core, there is abundant euhedral (EPy) together with framboidal (FPy) pyrite. Clay minerals (cl) and organic matter are also scattered between the carbonate crystals of the concretion. Horizontal field of view is 45 μm. (b) Backscattered scanning electron micrograph of the outer rim of the Birchi Bed concretion. Dolomite crystals (D) are rhombohedral and they often have dissolved centres (as in the dolomitic zone). Their zonation is apparent and probably reflects fluctuations in the iron content of the pore waters. Some anhedral calcite crystals (C) exist in higher abundance than in the dolomitic zone and in some cases, they seem to envelop the dolomitic rhombs (thick arrow). There is also some framboidal pyrite (FPy) also exists. Clay minerals (cl), organic matter (OM) and some quartz (Q) are also scattered between the carbonate crystals of the concretion. Horizontal field of view is 50 μm.

( a ) Backscattered scanning electron micrograph of the dolomitic zone. Dol...

Published: 01 January 2000
of the outer rim of the Birchi Bed concretion. Dolomite crystals (D) are rhombohedral and they often have dissolved centres (as in the dolomitic zone). Their zonation is apparent and probably reflects fluctuations in the iron content of the pore waters. Some anhedral calcite crystals (C) exist in higher
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Simplified stratigraphic column of part of the Charmouth Mudstone Formation to show levels from which bitten ammonites have been collected (asterisks) and Lang's bed numbers, with an expanded insert to show approximate positions of the Yellowstones to Flatstones stone bands. Other named beds are: 76 = Birchi Tabular Bed; 80 = Lower Cement Bed; 82 = Upper Cement Bed or Pavior; 85 = Topstones; 87 = Limestone with Brachiopods; 89 = Coinstone (with Stellare nodules below it) and which represents a significant hiatus in the Dorset succession; 92 = Lymense Bed. Upper S, Upper Sinemurian; Densi, Densinodulatum Subzone; S P M, Stonebarrow Pyritic Member. Based on Lang &amp; Spath (1926, fig. 1), Hesselbo &amp; Jenkyns (1995, figs 9, 10) and Simms (2004, fig. 2.8).

Simplified stratigraphic column of part of the Charmouth Mudstone Formation...

Published: 01 November 2010
beds are: 76 = Birchi Tabular Bed; 80 = Lower Cement Bed; 82 = Upper Cement Bed or Pavior; 85 = Topstones; 87 = Limestone with Brachiopods; 89 = Coinstone (with Stellare nodules below it) and which represents a significant hiatus in the Dorset succession; 92 = Lymense Bed. Upper S, Upper Sinemurian
Journal Article

Does the Birchy Complex of Newfoundland extend into Ireland?

J. A. WINCHESTER, H. WILLIAMS, M. D. MAX, C. R. VAN STAAL
Published: 01 April 1992
Journal of the Geological Society (1992) 149 (2): 159–162.
DOI: https://doi.org/10.1144/gsjgs.149.2.0159
...J. A. WINCHESTER; H. WILLIAMS; M. D. MAX; C. R. VAN STAAL Abstract Metabasalts from the Birchy Complex in Newfoundland are chemically similar to the Kill-Callow suite of metabasalts in Co. Mayo, Ireland. The latter, which are also chemically akin to Cambrian amphibolites of the Highland Border...
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Journal Article

The Caledonian evolution of the Laurentian margin in western Ireland

D. H. M. HARRIS
Published: 01 August 1993
Journal of the Geological Society (1993) 150 (4): 669–672.
DOI: https://doi.org/10.1144/gsjgs.150.4.0669
... the Birchy Complex of Newfoundland extend into Ireland Journal of the Geological Society, London 1992 149 159 163 Yardley B. W. D. An Introduction to Metamorphic Petrology 1990 Longman Earth Science Scries Yardley B. W. D. Barber J. P. Gray J. R. The metamorphism...
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Journal Article

Petrochemical and geochronological constraints on the origin of the Sops Arm group, the most westerly Silurian volcano-sedimentary extensional basin on the western Newfoundland composite Laurentian margin

H.A.I. Sandeman, I.W. Honsberger, C. Peddle, S.L. Kamo, G.R. Dunning
Published: 13 September 2024
Canadian Journal of Earth Sciences (2025) 62 (2): 276–298.
DOI: https://doi.org/10.1139/cjes-2024-0032
... lithogeochemical and Nd isotopic data, provide further insights into the origin, petrogenesis, and age of the SAG. Western White Bay is transected by three major north–south-trending, steeply dipping fault systems termed the Cabot, Birchy Ridge, and Doucers Valley faults ( Figs. 1 and 2 ; Smyth...
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