The Ypresian is additionally marked by another warming event called the Early Eocene Climatic Optimum (EECO). The EECO is the longest sustained warming event in the Cenozoic record, lasting about 2–3 million years between 53 and 50 Ma. The interval is characterized by lowoxygen-18 isotopes,[8][9][10] high levels ofatmospheric pCO2,[11][12] and low meridional thermal gradients.[13]Biodiversity has been reported to have been significantly impacted by the conditions prevalent during the EECO. For instance, there were biotic turnovers amongmarine producers such ascalcareous nannofossils among others etc.[14][15]
The Ypresian Stage was introduced in scientific literature byBelgian geologistAndré Hubert Dumont in 1850. The Ypresian is named after theFlemish city ofYpres in Belgium (spelledIeper in Dutch). The definitions of the original stage were totally different from the modern ones.[16] The Ypresian shares its name with the BelgianIeper Group (French:Groupe d'Ypres), which has an Ypresian age.
The base of the Ypresian Stage is defined at a strong negative anomaly inδ13C values at thePETM. The official reference profile (GSSP) for the base of the Ypresian is the Dababiya profile near theEgyptian city ofLuxor.[17] Its originaltype section was located in the vicinity of Ieper.
The top of the Ypresian (the base of the Lutetian) is identified by the first appearance of theforaminiferagenusHantkenina in the fossil record.
^Greenwood, D.R.; Archibald, S.B.; Mathewes, R.W; Moss, P.T. (2005). "Fossil biotas from the Okanagan Highlands, southern British Columbia and northeastern Washington State: climates and ecosystems across an Eocene landscape".Canadian Journal of Earth Sciences.42 (2):167–185.Bibcode:2005CaJES..42..167G.doi:10.1139/e04-100.
^Archibald, S.; Greenwood, D.; Smith, R.; Mathewes, R.; Basinger, J. (2011). "Great CanadianLagerstätten 1. Early Eocene Lagerstätten of the Okanagan Highlands (British Columbia and Washington State)".Geoscience Canada.38 (4):155–164.
^Lowe, A. J.; Greenwood, D. R.; West, C. K.; Galloway, J. M.; Sudermann, M.; Reichgelt, T. (2018). "Plant community ecology and climate on an upland volcanic landscape during the Early Eocene Climatic Optimum: McAbee Fossil Beds, British Columbia, Canada".Palaeogeography, Palaeoclimatology, Palaeoecology.511:433–448.Bibcode:2018PPP...511..433L.doi:10.1016/j.palaeo.2018.09.010.S2CID134962126.
Dumont, A. H.; 1850:Rapport sur la carte géologique du Royaume, Bulletins de l’Académie Royale des Sciences, des Lettres et des Beaux-Arts de Belgique16 (2), pp. 351–373.(in French)
Dupuis, C.; Aubry, M.; Steurbaut, É; Berggren, W. A.; Ouda, K.; Magioncalda, R.; Cramer, B. S.; Kent, D. V.; Speijer, R. P. & Heilmann-Clausen, C.; 2003:The Dababiya Quarry Section: Lithostratigraphy, clay mineralogy, geochemistry and paleontology, Micropaleontology49 (1), pp. 41–59,ISSN0026-2803.
Gradstein, F. M.; Ogg, J. G. & Smith, A. G.; 2004:A Geologic Time Scale 2004,Cambridge University Press.
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