الأكسفوردية (مرحلة)

Oxfordian
Oxfordian
161.5 ± 1.0 – 154.8 ± 0.8 Ma PreЄ Є O S D C P T J K Pg N
	Cyclically alternating limestone (light, more competent) and marl/clay layers of Oxfordian age at Péry-Reuchenette, near Tavannes, Jura Mountains, Switzerland.
Chronology
	أهم الأحداث في العصر الجوراسي This box: view; talk; edit; -205 — – -200 — – -195 — – -190 — – -185 — – -180 — – -175 — – -170 — – -165 — – -160 — – -155 — – -150 — – -145 — – Cretaceous Triassic Jurassic Hettangian Sinemurian Pliensbachian Toarcian Aalenian Bajocian Bathonian Callovian Oxfordian Kimmeridgian Tithonian J; u; r; a; s; s; i; c Mesozoic; An approximate timescale of key Jurassic events.; Axis scale: millions of years ago.;
Etymology
Name formality	Formal
Usage information
Celestial body	Earth
Regional usage	Global (ICS)
Time scale(s) used	ICS Time Scale
Definition
Chronological unit	Age
Stratigraphic unit	Stage
Time span formality	Formal
Lower boundary definition	FAD of ammonite species Brightia thuouxensis
Lower boundary definition candidates	Horizon of the Ammonite Cardioceras redcliffense.
Lower boundary GSSP candidate section(s)	Redcliff Point, Dorset, UK; Savouron, Provence, France;
Upper boundary definition	FAD of the Ammonite Pictonia baylei
Upper boundary GSSP	Flodigarry, Skye, Scotland, UK; 57°39′40″N 6°14′44″W / 57.6610°N 6.2455°W
GSSP ratified	2021

The Oxfordian is, in the ICS' geologic timescale, the earliest age of the Late Jurassic Epoch, or the lowest stage of the Upper Jurassic Series. It spans the time between 161.5 ± 1.0 Ma and 154.8 ± 0.8 Ma (million years ago).^[2] The Oxfordian is preceded by the Callovian and is followed by the Kimmeridgian.

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Stratigraphic definitions

The Oxfordian Stage was called "Clunch Clay and Shale" by William Smith (1815–1816); in 1818 W. Buckland described them under the unwieldy title "Oxford, Forest or Fen Clay". The term Oxfordian was introduced by Alcide d'Orbigny in 1844. The name is derived from the English city of Oxford,^[3] where the beds are well developed, but they crop out almost continuously from Dorset to the coast of Yorkshire, generally forming low, broad valleys. They are well exposed at Weymouth, Oxford, Bedford, Peterborough, and in the cliffs at Scarborough, Red Cliff and Gristhorpe Bay. Rocks of this age are found also in Uig and Skye.^[4]

The base of the Oxfordian Stage is defined as the point in the stratigraphic record where the ammonite species Brightia thuouxensis first appears. A global reference profile for the base (a GSSP) had in 2009 not yet been assigned. The top of the Oxfordian Stage (the base of the Kimmeridgian) is at the first appearance of ammonite species Pictonia baylei.

In the Tethys domain, the Oxfordian contains six ammonite biozones:

References

Notes

^ "Global Boundary Stratotype Section and Point". International Commission of Stratigraphy. Retrieved 25 July 2021.
^ "Stratigraphic Chart 2022" (PDF). International Commission on Stratigraphy. February 2022. Retrieved 22 April 2022.
^ Oxfordian is a word meaning "from Oxford" (see wiktionary:Oxfordian).
^ One or more of the preceding sentences incorporates text from a publication now in the public domain: Howe, John Allen (1911). "Oxfordian" . In Chisholm, Hugh (ed.). دائرة المعارف البريطانية. Vol. 20 (eleventh ed.). Cambridge University Press. p. 415. {{cite encyclopedia}}: Cite has empty unknown parameter: |coauthors= (help)

Literature

Brongniart, A.; 1829: Tableau théorique de la succession et de la disposition la plus générale on Europa, des terrains et roches, qui composent l'écorce de la terre, Paris.(in فرنسية)
Gradstein, F.M.; Ogg, J.G. & Smith, A.G.; 2004: A Geologic Time Scale 2004, Cambridge University Press.

External links

GeoWhen Database - Oxfordian
Jurassic-Cretaceous timescale, at the website of the subcommission for stratigraphic information of the ICS
Stratigraphic chart of the Upper Jurassic, at the website of Norges Network of offshore records of geology and stratigraphy

قالب:Jurassic footer

[GSSP_Web-1] "Global Boundary Stratotype Section and Point". International Commission of Stratigraphy. Retrieved 25 July 2021.

[StratChart_2022-2] "Stratigraphic Chart 2022" (PDF). International Commission on Stratigraphy. February 2022. Retrieved 22 April 2022.

[3] Oxfordian is a word meaning "from Oxford" (see wiktionary:Oxfordian).

[4] One or more of the preceding sentences incorporates text from a publication now in the public domain: Howe, John Allen (1911). "Oxfordian" . In Chisholm, Hugh (ed.). دائرة المعارف البريطانية. Vol. 20 (eleventh ed.). Cambridge University Press. p. 415. {{cite encyclopedia}}: Cite has empty unknown parameter: |coauthors= (help)

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