In the geologic timescale the Ypresian ( /iːˈprɛsiən/) is the oldest age or lowest stratigraphic stage of the Eocene. It spans the time between , is preceded by the Thanetian age (part of the Paleocene) and is followed by the Eocene Lutetian age.
The Ypresian is consistent with the lower Eocene.
|Subdivision of the Paleogene Period|
according to the ICS, as of 2017.
The Ypresian stage was introduced in scientific literature by Belgian geologist André Hubert Dumont in 1850. The Ypresian is named after Ypres, the French name of the Belgian (Flemish) city of Ieper (Ieper). The definitions of the original stage were totally different from the modern ones. The Ypresian shares its name with the Belgian Ieper Group (French: Groupe d'Ypres), which has an Ypresian age.
The base of the Ypresian stage is defined at a strong negative anomaly in δ13C values at the PETM. The official reference profile (GSSP) for the base of the Ypresian is the Dababiya profile near the Egyptian city of Luxor. Its original type section was located in the vicinity of Ieper.
The Ypresian stage overlaps the upper Neustrian and most of the Grauvian European Land Mammal Mega Zones (it spans the Mammal Paleogene zones 7 through 10.), the Wasatchian and lower and middle Bridgerian North American Land Mammal Ages, the Casamayoran South American Land Mammal Age and the Bumbanian and most of the Arshantan Asian Land Mammal Ages. It is also coeval with the upper Wangerripian and lowest Johannian regional stages of Australia and the Bulitian, Penutian and Ulatisian regional stages of California.