Contents

Bajocian

D

C

P

T

J

K

Pg

N

–

−180 —

–

−175 —

–

−170 —

–

−165 —

–

−160 —

–

−155 —

–

−150 —

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−145 —

–

Formal

Earth

Global (ICS)

ICS Time Scale

Age

Stage

Formal

FAD of the Ammonites Hyperlioceras mundum, Hyperlioceras furcatum, Braunsina aspera, and Braunsina elegantula

Cabo Mondego, Portugal
40°11′57″N 8°54′15″W / 40.1992°N 8.9042°W / 40.1992; -8.9042

1996^[2]

FAD of the Ammonite Gonolkites convergen

Ravin du Bès, Bas-Auran, Alpes de Haute, France
43°57′38″N 6°18′55″E / 43.9606°N 6.3153°E / 43.9606; 6.3153

July 2008^[3]

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.^[4]

Stratigraphic definitions[edit]

The Bajocian Stage takes its name from the Latin name (Bajocae) of the town of Bayeux, in the region of NormandyinFrance. 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 (aGSSP) for the base is located at Murtinheira, close to Cabo MondegoinPortugal.^[5] The top of the Bajocian (the base of the Bathonian) is at the first appearance of ammonite species Parkinsonia convergens.

Subdivision[edit]

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[edit]

Notes[edit]

Literature[edit]

• Gradstein, F.M.; Ogg, J.G. & Smith, A.G.; 2004: A Geologic Time Scale 2004, Cambridge University Press.
• Alcide d´Orbigny; 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): pp 16–22.
• Sepkoski, J.; 2002: A compendium of fossil marine animal genera (entry on cephalopoda), Bulletins of American Paleontology 364, p 560.
• Rodríguez-de la Rosa, Rubén A.; Velasco-de León, María Patricia; Lozano-Carmona, Diego-Enrique; Arellano-Gil, Javier (2018). "Middle Jurassic ankylosaur tracks from Mexico" (PDF). Boletín de la Sociedad Geológica Mexicana. 70 (2): 379–395. doi:10.18268/BSGM2018v70n2a8. S2CID 187400703.

External links[edit]

Wikisource has the text of the 1911 Encyclopædia Britannica article "Bajocian".

• GeoWhen Database - Bajocian
• Jurassic-Cretaceous and Lower Jurassic 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