Kimmeridgian

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Kimmeridgian
154.8 ± 0.8 – 149.2 ± 0.7 Ma
Chronology

In the

Ma and 149.2 ±0.7 Ma (million years ago). The Kimmeridgian follows the Oxfordian and precedes the Tithonian.[2]

Stratigraphic definition

The Kimmeridgian Stage takes its name from the village of

Kimmeridge Clay Formation takes its name from the same type location (although this formation extends from the Kimmeridgian stage of the Upper Jurassic into the Lower Cretaceous). It is the source for about 95% of the petroleum in the North Sea.[citation needed
]

Historically, the term Kimmeridgian has been used in two different ways. The base of the interval is the same but the top was defined by British

Portlandian (sensu anglico) whereas in France the top was defined as the base of the Tithonian (sensu gallico). The differences have not yet been fully resolved; As of 2004 Tithonian is the uppermost stage of the Jurassic in the timescale of the ICS.[4]

The base of the Kimmeridgian is at the first appearance of

ammonite species Pictonia baylei in the stratigraphic column.[5] The Global Boundary Stratotype Section and Point (GSSP) for the base of the Kimmeridgian is the Flodigarry section at Staffin Bay on the Isle of Skye, Scotland,[6] which was ratified in 2021. The boundary is defined by the first appearance of ammonites marking the boreal Bauhini Zone and the subboreal Baylei Zone.[7] The top of the Kimmeridgian (the base of the Tithonian) is at the first appearance of ammonite species Hybonoticeras hybonotum. It also coincides with the top of magnetic anomaly M22An.[5]

Subdivision

The Kimmeridgian is sometimes[

ammonite biozones:[citation needed
]

References

Notes

  1. ^ "International Chronostratigraphic Chart" (PDF). International Commission on Stratigraphy.
  2. ^ a b "Global Boundary Stratotype Section and Point". International Commission of Stratigraphy. Retrieved 25 July 2021.
  3. ISBN 978-0-44-459390-0
    .
  4. ^ INTERNATIONAL SUBCOMMISSION ON JURASSIC STRATIGRAPHY, Newsletter 31, Edited by Nicol Morton and Paul Bown, August 2004
  5. ^ a b "Global Boundary Stratotype Section and Point (GSSP) of the International Commission on Stratigraphy". GSSP Table - All Periods. International Commission on Stratigraphy. Retrieved 5 January 2018.
  6. S2CID 133861564
    .
  7. ^ "International Commission on Stratigraphy-Subcommission on Jurassic Stratigraphy". jurassic.stratigraphy.org. Retrieved 2021-04-09.

Literature

  • Gradstein, F.M.; Ogg, J.G. & Smith, A.G.; 2004: A Geologic Time Scale 2004, Cambridge University Press.
  • Thurmann, J.; 1832: Sur Les Soulèvemens Jurassiques Du Porrentruy: Description Géognostique de la Série Jurassique et Théorie Orographique du Soulèvement, Mémoires de la Société d'histoire naturelle de Strasbourg 1: pp 1–84, F. G. Levrault, Paris.(in French)

External links

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