The Oxfordian is, in the
ICS'
geologic timescale
The geologic time scale, or geological time scale, (GTS) is a representation of time based on the rock record of Earth. It is a system of chronological dating that uses chronostratigraphy (the process of relating strata to time) and geochr ...
, the earliest
age of the
Late Jurassic Epoch
In chronology and periodization, an epoch or reference epoch is an instant in time chosen as the origin of a particular calendar era. The "epoch" serves as a reference point from which time is measured.
The moment of epoch is usually decided ...
, or the lowest
stage of the
Upper Jurassic Series. It spans the time between 163.5 ± 1.0
Ma and 157.3 ± 1.0 Ma (million years ago).
The Oxfordian is preceded by the
Callovian and is followed by the
Kimmeridgian.
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, 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.
The base of the Oxfordian Stage is defined as the point in the stratigraphic record where the
ammonite
Ammonoids are a group of extinct marine mollusc animals in the subclass Ammonoidea of the class Cephalopoda. These molluscs, commonly referred to as ammonites, are more closely related to living coleoids (i.e., octopuses, squid and cuttlefis ...
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:
*zone of ''
Epipeltoceras bimammatum''
*zone of ''
Perishinctes bifurcatus''
*zone of ''
Gregoryceras transversarium''
*zone of ''
Perisphinctes plicatilis''
*zone of ''
Cardioceras cordatum''
*zone of ''
Quenstedtoceras mariae''
References
Notes
Literature
*; 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.
*; 2004: ''A Geologic Time Scale 2004'',
Cambridge University Press
Cambridge University Press is the university press of the University of Cambridge. Granted letters patent by King Henry VIII in 1534, it is the oldest university press in the world. It is also the King's Printer.
Cambridge University Pr ...
.
External links
GeoWhen Database - OxfordianJurassic-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
{{Geological history, p, m, state=collapsed
*01
Geological ages
1827 introductions
Culture in Oxford