Ypresian
Earliest Eocene age (56.00–48.07 Ma), originally a Belgian clay-and-glauconitic-sand division.
Language and route: French scientific nomenclature from a bilingual Belgian place-name. French Ypres, Dutch Ieper, Belgium → historical scientific stage-name Ypresian. This is a geographical/eponymic formation, not a Greek life-comparison compound.
Literal gloss: of Ypres / Ieper
The name and its history
André Hubert Dumont · Communicated 1849; published 1850
- What does the word literally mean?
- of Ypres / Ieper
- What did the original author mean?
- Dumont separated marine clays and overlying glauconitic sands of the hills around Ypres from his Landenian succession, contrasting marine and fresh-water influenced units.
- Why was the name needed?
- Belgian lower Tertiary rocks were arranged by variable lithology and depositional setting; a more specific middle unit was needed for mapping and comparison.
- What evidence supported the original concept?
- Large bodies of clay, overlying fine glauconitic sand, marine fossils and their geographic distribution were his evidence; he specified no modern point stratotype.
- How has geology changed the concept?
- Dumont’s local unit is not coextensive with the modern Eocene-opening Ypresian, whose GSSP is at Dababiya, Egypt, defined around the PETM.
Further historical context
Dumont separated marine clays and overlying glauconitic sands of the hills around Ypres from his Landenian succession, contrasting marine and fresh-water influenced units.
Belgian lower Tertiary rocks were arranged by variable lithology and depositional setting; a more specific middle unit was needed for mapping and comparison.
Large bodies of clay, overlying fine glauconitic sand, marine fossils and their geographic distribution were his evidence; he specified no modern point stratotype.
Dumont’s local unit is not coextensive with the modern Eocene-opening Ypresian, whose GSSP is at Dababiya, Egypt, defined around the PETM.
Editorial qualification
Crucial chronology: announcement at the 1849 meeting, minutes published in 1850. Do not write 1849 as an unqualified publication year.
Related names
Paleogene · Eocene · Thanetian · Lutetian · Paleocene · Lithofacies
Sources
- International Commission on Stratigraphy, International Chronostratigraphic Chart v2026/06 — Primary authority for present unit names, hierarchy and boundary ages, not first coinages
- Steurbaut (2006), Ypresian, Geologica Belgica — Checks Dumont’s 1849 presentation/1850 publication, original lithologies and GSSP shift to Egypt
- Speijer et al. (2020), The Paleogene Period, Geologic Time Scale 2020 — Specialist historical narratives, original regional definitions and modern GSSP revisions