Bajocian
Middle Jurassic age named for Bayeux in Normandy; its original lower part was later reallocated to the Aalenian.
Language and route: International scientific terminology from Latinised place-name from a French locality. French Bayeux, Latinised as Bajocae/Bajocassae → French Bajocien → English Bajocian.
Literal gloss: of/from Bajocae
The name and its history
Alcide d’Orbigny · mid-nineteenth century; c. 1850 (date not independently proved)
- What does the word literally mean?
- ‘of/from Bajocae’, referring to Bayeux (Latinised Bajocae) in Normandy, France.
- What did the original author mean?
- D’Orbigny adopted a locality-based stage for Jurassic faunas associated with the Bayeux district, within his attempt to construct a geographical and fossil-correlated stage scheme.
- Why was the name needed?
- Beds grouped as the Inferior Oolite and adjacent facies shifted character across northwestern Europe; simple lithological labels could not provide a consistent chronology.
- What evidence supported the original concept?
- Ammonite assemblages from Normandy and correlated European successions supported a recognisable stratigraphic unit.
- How has geology changed the concept?
- The ICS base is tied to an ammonite boundary at Cabo Mondego, Portugal; revisions removed part of the former lower Bajocian into the Aalenian.
Further historical context
The name invokes Bayeux (Latinised Bajocae) in Normandy, France. D’Orbigny adopted a locality-based stage for Jurassic faunas associated with the Bayeux district, within his attempt to construct a geographical and fossil-correlated stage scheme.
Beds grouped as the Inferior Oolite and adjacent facies shifted character across northwestern Europe; simple lithological labels could not provide a consistent chronology. Ammonite assemblages from Normandy and correlated European successions supported a recognisable stratigraphic unit.
The ICS base is tied to an ammonite boundary at Cabo Mondego, Portugal; revisions removed part of the former lower Bajocian into the Aalenian.
Editorial qualification
Latinised toponym does not justify an invented Greek gloss; first-use year varies between secondary accounts.
Related names
Sources
- ICS International Chronostratigraphic Chart, 2026/06 — Official current ranks and names; ages are subject to revision
- Middle Jurassic of Britain, Geological Conservation Review introduction — Middle Jurassic naming sequences and classification
- P. Fauré, Le Jurassique: divisions et étages, histoire de la géologie — French historiographical account; some first-year claims conflict with other accounts
- ICS Subcommission on Jurassic Stratigraphy, stage working groups — Individual stage boundary status and GSSP locations