Bathonian
Middle Jurassic age recalling the oolitic limestone country near Bath; now defined by fossils in southeast France.
Language and route: International scientific terminology from English town name through Latinised Bathonian. English town name through Latinised Bathonian place-name Bath → international scientific stage-name Bathonian (English); older place-name origin not inferred.
Literal gloss: of/from Bath
The name and its history
Jean-Baptiste d’Omalius d’Halloy (name attribution), later d’Orbigny · 1843 and later mid-century stage codification
- What does the word literally mean?
- ‘of/from Bath’, referring to Bath, Somerset, England.
- What did the original author mean?
- Nineteenth-century geologists used Bath’s widely quarried oolitic limestones as a regional point of comparison. The stage name is often attributed to d’Omalius d’Halloy (1843) and then formalised in d’Orbigny’s later scheme.
- Why was the name needed?
- “Great Oolite” and related British formation names were powerful practical markers but changed facies or proved incomplete when traced into continental sections.
- What evidence supported the original concept?
- Oolitic limestone successions and their marine fossils motivated distinguishing this interval in the emerging Middle Jurassic series.
- How has geology changed the concept?
- The Bathonian now begins at the Ravin du Bès GSSP in southeast France, with fossil markers; it is not defined by deposition of Bath Stone.
Further historical context
The name invokes Bath, Somerset, England. Nineteenth-century geologists used Bath’s widely quarried oolitic limestones as a regional point of comparison. The stage name is often attributed to d’Omalius d’Halloy (1843) and then formalised in d’Orbigny’s later scheme.
“Great Oolite” and related British formation names were powerful practical markers but changed facies or proved incomplete when traced into continental sections. Oolitic limestone successions and their marine fossils motivated distinguishing this interval in the emerging Middle Jurassic series.
The Bathonian now begins at the Ravin du Bès GSSP in southeast France, with fossil markers; it is not defined by deposition of Bath Stone.
Editorial qualification
Separate d’Omalius’s use of the name from d’Orbigny’s formal stage concept; source histories vary on priority.
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