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 low oxygen 18 isotopes,[8][9][10] high levels of atmospheric 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 among marine producers such as calcerous nannofossil among others etc.[14][15]
Stratigraphic definition
The Ypresian Stage was introduced in scientific literature by
Belgian geologist
André Hubert Dumont in 1850. The Ypresian is named after the
Flemish city of
Ypres in Belgium (spelled Ieper in Dutch). The definitions of the original stage were totally different from the modern ones.[16] 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.[17] Its original
type 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 the
foraminiferagenusHantkenina 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 Canadian Lagerstätten 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 Belgique 16 (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, Micropaleontology 49 (1), pp. 41–59,
ISSN0026-2803.
Gradstein, F. M.; Ogg, J. G. & Smith, A. G.; 2004: A Geologic Time Scale 2004,
Cambridge University Press.