Tertiary
Historical name for much of the Cenozoic succession, now covered by the Paleogene and Neogene periods.
Language and route: English geological term after Latin/French ordinal classification. From Latin tertius, ‘third’; French tertiaire and historical English geological usage.
Literal gloss: third
The name and its history
Ordinal antecedent: Giovanni Arduino; later Paris Basin users · 1759 antecedent; 1810s usage
- What does the word literally mean?
- The name is ordinal, inherited from early European divisions of strata rather than fossil-based era nomenclature.
- What did the original author mean?
- ‘Third’ was part of an ordinal model of successive kinds of strata, later repurposed as a time division.
- Why was the name needed?
- Early geologists needed to place younger fossiliferous strata beyond older ‘Primary’ and ‘Secondary’ units.
- What evidence supported the original concept?
- Superposition, geographic basin mapping and fossils of younger deposits informed later nineteenth-century subdivisions.
- How has geology changed the concept?
- The Tertiary is not a formal ICS period; its historical span was redistributed into Paleogene and Neogene (and, in some older usages, early Quaternary).
Further historical context
Giovanni Arduino described a ‘third order’ in his 1759 regional classification of strata. Later Cuvier and Brongniart (1810) used terrain tertiaire in Paris Basin geology above the Chalk, with fossil-rich deposits that Lyell subsequently subdivided into epochs.
John Phillips’s Cenozoic ‘new life’ label (1841) and Naumann’s Paleogene (1866) and Hörnes’s Neogene (1853) eventually provided a different classification. Tertiary remains widespread in historical literature but is not a formal ICS period on the 2026 chart.
Editorial qualification
Care needed distinguishing an ordinal concept from first attestation of the geological noun.
Related names
Quaternary · Paleogene · Neogene · Cenozoic · Fossil · Superposition
Sources
- ICS International Chronostratigraphic Chart, 2026/06 — Current name, rank and numerical boundaries
- ICS Subcommission: History of Quaternary nomenclature — Primary/Secondary/Tertiary/Quaternary; historical interpretation
- Scottish Geology Trust: historical nomenclature of the Tertiary — Hoernes, Naumann, Lyell and palaeontological divisions
- Berggren et al. (2008), The Neogene: origin, adoption, evolution, and controversy — Historiography of Hörnes and Neogene–Quaternary dispute