Roadian
The age of the Guadalupian interval (Permian), approximately 274.4–266.9 Ma according to the ICS June 2026 chart.
Language and route: English North American place-name. English North American place-name → stratigraphic English. Named after Road Canyon Member / Road Canyon, Glass Mountains, Texas.
Literal gloss: from Road Canyon
The name and its history
Stage use by Furnish and Glenister, late 1960s (sources differ between 1966 and 1968–70) · See attributed dates and cited original / standardisation works; first-use priority qualified where noted
- What does the word literally mean?
- From road canyon. Immediate scientific language-route: English North American place-name → stratigraphic English. This is a locality-based or geographical term, not a description of a universal geological event.
- What did the original author mean?
- The post-Artinskian, pre-Wordian faunal interval named for a Road Canyon limestone succession in West Texas.
- Why was the name needed?
- Workers needed an interval between the Artinskian–Kungurian sequence and established middle Permian units; a Texas canyon-associated limestone supplied the name.
- What evidence supported the original concept?
- The Road Canyon fossil assemblages, especially ammonoids, could be compared internationally and justified a discrete early Guadalupian stage.
- How has geology changed the concept?
- Today it begins the Guadalupian series, although global conodont-based correlations and the historical stage definition have required reassessment.
Further historical context
*Naming and context.* Workers needed an interval between the Artinskian–Kungurian sequence and established middle Permian units; a Texas canyon-associated limestone supplied the name.
*Evidence and later scope.* The Road Canyon fossil assemblages, especially ammonoids, could be compared internationally and justified a discrete early Guadalupian stage. Today it begins the Guadalupian series, although global conodont-based correlations and the historical stage definition have required reassessment.
Editorial qualification
Bibliographies differ on 1966 vs 1968 earliest stage use; do not collapse those dates into a fictitious certainty.
Related names
Permian · Guadalupian · Wordian · Capitanian · Fossil · Conodont · Ammonoid · Stratigraphy
Sources
- ICS International Chronostratigraphic Chart (June 2026) — Current formal unit, order, rank and numerical age
- Glenister et al. (1999), Proposal for Roadian–Capitanian standards — Near-contemporaneous evidence for priority, naming routes and correlation
- Jin et al. (1997), Permian chronostratigraphic subdivisions, Episodes — International decision to adopt Urals, Texas and South China tripartition