Frasnian
The Frasnian Age/Stage within the Late Devonian (ICS 2026/06); about 382.31–372.15 Ma.
Language and route: Belgian French locality-name → geological French/English. Belgian French locality-name → geological French/English. Name-source: Frasnes, near Couvin in Belgium.
Literal gloss: named after Frasnes, near Couvin in Belgium
The name and its history
Frequently attributed to J.-J. d’Omalius d’Halloy, 1862, in historical compilations; original printed act not independently checked · Frequently attributed to J.-J. d’Omalius d’Halloy, 1862, in historical compilations; original printed act not independently checked
- What does the word literally mean?
- Named from Frasnes, near Couvin in Belgium.
- What did the original author mean?
- A distinct Late Devonian marine rock/fauna succession recognised in the Frasnes district of the Dinant Synclinorium.
- Why was the name needed?
- Belgian geologists needed to subdivide the Devonian based on changing fossil assemblages and reef/carbonate facies above the middle Devonian.
- What evidence supported the original concept?
- Regional fossil assemblages first; the modern basal boundary at Col du Puech de la Suque, France, uses a conodont first-appearance datum of Ancyrodella rotundiloba.
- How has geology changed the concept?
- The global stage keeps a Belgian locality-name, but its base was established in southern France through internationally correlatable marine fossils.
Further historical context
*Original use.* A distinct Late Devonian marine rock/fauna succession recognised in the Frasnes district of the Dinant Synclinorium.
*Historical problem.* Belgian geologists needed to subdivide the Devonian based on changing fossil assemblages and reef/carbonate facies above the middle Devonian.
*Evolution.* The global stage keeps a Belgian locality-name, but its base was established in southern France through internationally correlatable marine fossils.
Editorial qualification
The original regional lithofacies and global time boundary are not equivalent; the nineteenth-century attribution is cited as secondary.
Related names
Devonian · Late Devonian · Famennian · Fossil · Facies · Lithofacies
Sources
- ICS International Chronostratigraphic Chart, 2026/06 — Current nomenclature, rank and numerical age
- ICS official Frasnian GSSP — International boundary stratotype and correlation evidence
- Belgian National Commission on Stratigraphy, Frasnes origin — Historical naming, original claim or scholarly review; see confidence note
- Published historical stage-attribution table — Historical naming, original claim or scholarly review; see confidence note
- ICS Devonian Subcommission, full sequence — Cross-check order and stage nomenclature