In the geologic timescale, the Bajocian is an age and stage in the Middle Jurassic. It lasted from approximately 170.3 Ma to around 168.3 Ma (million years ago). The Bajocian Age succeeds the Aalenian Age and precedes the Bathonian Age.[4]

Bajocian
170.3 ± 1.4 – 168.3 ± 1.3 Ma
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 the Ammonites Hyperlioceras mundum, Hyperlioceras furcatum, Braunsina aspera, and Braunsina elegantula
Lower boundary GSSPCabo Mondego, Portugal
40°11′57″N 8°54′15″W / 40.1992°N 8.9042°W / 40.1992; -8.9042
GSSP ratified1996[2]
Upper boundary definitionFAD of the Ammonite Gonolkites convergen
Upper boundary GSSPRavin 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
GSSP ratifiedJuly 2008[3]

Stratigraphic definitionsEdit

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.[5] The top of the Bajocian (the base of the Bathonian) is at the first appearance of ammonite species Parkinsonia convergens.

SubdivisionEdit

The Bajocian is often divided into Lower/Early and Upper/Late subages or substages.

In the Tethys domain, the Bajocian contains seven ammonite biozones:

ReferencesEdit

NotesEdit

  1. ^ "International Chronostratigraphic Chart" (PDF). International Commission on Stratigraphy.
  2. ^ Pavia, G.; Enay, R. (March 1997). "Definition of the Aalenian-Bajocian Stage boundary". Episodes. 20 (1): 16–22. doi:10.18814/epiiugs/1997/v20i1/004. Retrieved 23 December 2020.
  3. ^ Fernández-López, Sixto Rafael; Pavia, Giulio; Erba, Elisabetta; Guiomar, Myette; Maria Helena Henriques; Lanza, Roberto; Mangold, Charles; Morton, Nicol; Olivero, Davide; Daniele Tiraboschi (2009). "The Global Boundary Stratotype Section and Point (GSSP) for base of the Bathonian Stage (Middle Jurassic), Ravin du Bès Section, SE France" (PDF). Episodes. 32 (4): 222–248. doi:10.18814/epiiugs/2009/v32i4/001.
  4. ^ See for a detailed geologic timescale Gradstein et al. (2004)
  5. ^ The GSSP is described by Pavia & Enay (1997)

LiteratureEdit

  • 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.

External linksEdit