Ypresian
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| Ypresian | |
|---|---|
| Name | Ypresian |
| Color | #F6D6C5 |
| Time start | 56.0 |
| Time end | 47.8 |
| Time start uncertainty | 0.2 |
| Time end uncertainty | 0.2 |
| Caption | Early Eocene marine sediments in the London Basin |
| Chronology | Paleogene |
| Period | Eocene |
| Era | Cenozoic |
| Former names | Lower Eocene |
Ypresian is the earliest age or lowest stage of the Eocene Epoch of the Paleogene Period, marking a major interval of Earth's early Cenozoic history characterized by rapid climatic change, widespread biotic turnover, and distinctive stratigraphic successions. It is widely recognized in regional and global stratigraphic schemes and is recorded in marine and terrestrial sequences across multiple continents, serving as a reference for studies in paleoclimatology, paleobiology, and basin analysis.
Definition and stratigraphic context
The formal definition of this stage was ratified using type sections and stratotypes anchored in classic European localities, with links to stratigraphic standards established by organizations such as the International Commission on Stratigraphy and criterial comparisons to boundaries used in regional schemes like the European Mammal Neogene (EMN) correlation and the North American Land Mammal Ages where equivalence to the Wasatchian is discussed. Stratigraphically it overlies the Paleocene–Eocene boundary and underlies the Lutetian, with marker horizons correlated via isotope excursions, magnetostratigraphy including chrons such as C24r and biostratigraphic tie-points employing index taxa used in revisions by researchers associated with institutions like the Royal Society and the Geological Society of London. The Global Boundary Stratotype Section and Point for the base is linked to carbon isotope anomalies and nannofossil events recognized in profiles from continental basins and marine platforms explored by teams from the Natural History Museum, London, Muséum national d'Histoire naturelle, Paris, and the Smithsonian Institution.
Age and chronology
Numerical ages for the stage are constrained by radiometric calibration, with ages derived from methods employed in studies by laboratories at universities such as UCL, ETH Zurich, University of California, Berkeley, and agencies like the US Geological Survey and the British Geological Survey. The interval is commonly placed between about 56.0 and 47.8 million years ago, refined using uranium-lead dating on zircons from volcanic ash beds in sequences studied in regions including the Paris Basin, the Green River Formation, the Fur Formation, and the Williston Basin. High-resolution chronostratigraphy integrates palaeomagnetic records tied to polarity chrons correlated with the Geomagnetic Polarity Time Scale as refined by consortia such as the International Ocean Discovery Program and earlier ocean drilling programs like the Deep Sea Drilling Project.
Paleogeography and climate
During this stage continental configurations and sea-level distributions recorded in reconstructions by researchers at the Paleomap Project and the Geological Survey of Canada show warm climates, reduced polar ice, and expanded shallow epicontinental seas across platforms such as the North Sea Basin, Arctic Ocean, and Tethys Sea. A major transient event, the Paleocene–Eocene Thermal Maximum as characterized in studies from institutions like Lamont–Doherty Earth Observatory, ETH Zurich, and the Max Planck Institute for Chemistry, manifests as a pronounced carbon isotope excursion, amplified greenhouse conditions, and biogeographic shifts documented in sedimentary records from the Atlantic Coastal Plain, Siberian Traps proximities, and the Shatsky Rise. Climate proxies—oxygen isotopes, leaf-margin analyses, and foraminiferal assemblages—have been deployed by teams affiliated with the California Institute of Technology, University of Oxford, CNRS, and the University of Tokyo to reconstruct elevated temperatures, high atmospheric CO2, and altered hydrological cycles that influenced monsoonal patterns studied in Asian basins like the Indian Plate–Eurasian Plate margin.
Biota and paleoecology
Flora and fauna during the stage reveal rapid diversification and dispersal events tracked in paleontological collections at the American Museum of Natural History, Natural History Museum, London, and the Royal Belgian Institute of Natural Sciences. Mammalian groups such as early perissodactyls, primatomorphs, and artiodactyl precursors radiated across landmasses documented in assemblages from the Willwood Formation, Bighorn Basin, Cambay Basin, and Messel Pit, with notable taxa described by researchers linked to the University of Bonn, University of Kansas, and the Institut Català de Paleontologia Miquel Crusafont. Marine microfossils including planktic foraminifera and calcareous nannoplankton, studied via core material from the Equatorial Pacific and the Weddell Sea, show turnover tied to ocean warming; vertebrate faunas including early cetaceans and amphibians appear in sites worked on by teams from the University of Pennsylvania, Universidad Nacional Autónoma de México, and the Natural History Museum of Los Angeles County. Plant fossils—angiosperm-dominated palynofloras, palms, and aquatic macrophytes—are recorded in floras curated by the Smithsonian Institution and regional surveys in the Guyana Shield, Amazon Basin, and Greenland.
Significant formations and sites
Key marine and terrestrial formations yielding stage-level records include the London Clay Formation, the Fur Formation, the Green River Formation, the Willwood Formation, the Messel Formation, the Fangcheng Formation, the Cambay Shale, the Marlborough Formation, and the La Meseta Formation. Fossil Lagerstätten such as the Messel Pit and preservation windows in the London Basin, Fur Island, Geiseltal, and Quercy Phosphorites have produced exquisitely preserved vertebrates, invertebrates, and plants studied by teams from institutions including the University of Münster, University of Copenhagen, Muséum d'histoire naturelle de Toulouse, and ETH Zurich. Marine records from continental margins drilled by the Ocean Drilling Program and the Integrated Ocean Drilling Program link to sequences in the Gulf of Mexico, North Atlantic, and Equatorial Pacific that are critical for global correlation.
Economic and scientific importance
Sedimentary successions deposited during this interval host hydrocarbon source rocks, reservoir units, and coal seams exploited in basins managed by companies and agencies such as BP, Shell, TotalEnergies, Statoil (Equinor), the Norwegian Petroleum Directorate, and national geological surveys of Norway, United Kingdom, Canada, and Australia. Scientific importance spans paleoclimate modeling centers like the Met Office Hadley Centre, NCAR, IPCC-affiliated research, and isotope laboratories at the Scripps Institution of Oceanography and Columbia University that use stage records to understand greenhouse climates, carbon cycle feedbacks, and extinction–radiation dynamics. The stratigraphic and paleontological record of this stage continues to inform biostratigraphic zonation schemes developed by international working groups convened under the International Union of Geological Sciences and is central to educational exhibits at museums such as the Natural History Museum, Paris, Field Museum, and Smithsonian National Museum of Natural History.