Bajocian


In the geologic timescale, the Bajocian is an age and stage in the Middle Jurassic. It lasted from approximately 170.9 ±0.8 Ma to around 168.2 ±1.2 Ma. The Bajocian Age succeeds the Aalenian Age and precedes the Bathonian Age.

Stratigraphic definitions

The Bajocian Stage takes its name from the Latin name of the town of Bayeux, in the region of Normandy in France. The stage was named and introduced in scientific literature by French palaeontologist Alcide d'Orbigny in 1842.
The base of the Bajocian stage is defined as the place in the stratigraphic column where fossils of the ammonite genus Hyperlioceras first appear. A global reference profile for the base is located at Murtinheira, close to Cabo Mondego in Portugal. The top of the Bajocian is at the first appearance of ammonite species Parkinsonia convergens.

Subdivision

The Bajocian is often divided into Lower/Early and Upper/Late subages or substages.
In the Tethys domain, the Bajocian contains seven ammonite biozones:
  • zone of Parkinsonia parkinsoni
  • zone of Garantiana garantiana
  • zone of Strenoceras niortense
  • zone of Stephanoceras humphriesianum
  • zone of Sonninia propinquans
  • zone of Witchellia laeviuscula
  • zone of ''Hyperlioceras discites''

    Literature

  • ; 2004: A Geologic Time Scale 2004, Cambridge University Press.
  • ; 1842: Paléontologie française. 1. Terrains oolitiques ou jurassiques, 642 pp., Bertrand, Paris.
  • ; 1997: Definition of the Aalenian-Bajocian Stage boundary, Episodes, 20: pp 16–22.
  • ; 2002: , Bulletins of American Paleontology 364, p 560.