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 (million years ago). The Bajocian Age succeeds the Aalenian Age and precedes the Bathonian Age.See for a detailed geologic timescale Gradstein et al. (2004)
Stratigraphic definitions The Bajocian Stage takes its name from the Latin name (Bajocae) 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 (a GSSP) for the base is located at Murtinheira, close to Cabo Mondego in Portugal.The GSSP is described by Pavia & Enay (1997) The top of the Bajocian (the base of the Bathonian) 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
References
Notes
Literature Gradstein, F.M.; Ogg, J.G. & Smith, A.G. (2004). A Geologic Time Scale 2004, Cambridge University Press. d'Orbigny, A.C.V.M.D. (1842). Paléontologie française. 1. Terrains oolitiques ou jurassiques, 642 pp., Bertrand, Paris. Pavia, G. & Enay, R. (1997). Definition of the Aalenian-Bajocian Stage boundary, Episodes, 20(1), 16–22. Sepkoski, J. (2002). A compendium of fossil marine animal genera (entry on cephalopoda), Bulletins of American Paleontology 364, 560.
External links
GeoWhen Database – Bajocian Jurassic-Cretaceous and Lower Jurassic (insecure http links!) timescales, 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