Oxfordian (stage)

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 163.5 ± 4 Ma and 157.3 ± 4 Ma (million years ago). The Oxfordian is preceded by the Callovian and is followed by the Kimmeridgian.[3]

Oxfordian
163.5 ± 1.0 – 157.3 ± 1.0 Ma
Péry-Reuchenette Oxfordian.JPG
Cyclically alternating limestone (light, more competent) and marl/clay layers of Oxfordian age at Péry-Reuchenette, near Tavannes, Jura Mountains, Switzerland.
Chronology
Etymology
Name formalityFormal
Usage information
Celestial bodyEarth
Regional usageGlobal (ICS)
Time scale(s) usedICS Time Scale
Definition
Chronological unitAge
Stratigraphic unitStage
Time span formalityFormal
Lower boundary definitionFAD of ammonite species Brightia thuouxensis
Lower boundary definition candidatesHorizon of the Ammonite Cardioceras redcliffense.
Lower boundary GSSP candidate section(s)
Upper boundary definitionFAD of the Ammonite Pictonia baylei
Upper boundary GSSPFlodigarry, Skye, Scotland, UK
57°39′40″N 6°14′44″W / 57.6610°N 6.2455°W / 57.6610; -6.2455
GSSP ratified2021[2]

Stratigraphic definitionsEdit

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,[4] 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.[5]

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:

ReferencesEdit

NotesEdit

  1. ^ "International Chronostratigraphic Chart" (PDF). International Commission on Stratigraphy.
  2. ^ "Global Boundary Stratotype Section and Point". International Commission of Stratigraphy. Retrieved 25 July 2021.
  3. ^ For a detailed geologic timescale see Gradstein et al. (2004)
  4. ^ Oxfordian is a word meaning "from Oxford" (see wiktionary:Oxfordian).
  5. ^   One or more of the preceding sentences incorporates text from a publication now in the public domainHowe, John Allen (1911). "Oxfordian". In Chisholm, Hugh (ed.). Encyclopædia Britannica. 20 (11th ed.). Cambridge University Press. p. 415.

LiteratureEdit

  • 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 French)
  • Gradstein, F.M.; Ogg, J.G. & Smith, A.G.; 2004: A Geologic Time Scale 2004, Cambridge University Press.

External linksEdit