Priabonian
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| Priabonian | |
|---|---|
| Name | Priabonian |
| Color | #FFDAB9 |
| Time start | 37.71 |
| Time end | 33.9 |
| Unit | Age |
| Era | Cenozoic |
| Period | Paleogene |
| Epoch | Eocene |
Priabonian. The Priabonian is the latest age of the Eocene Epoch, spanning from about 37.71 to 33.9 million years ago. It follows the Bartonian and precedes the Rupelian, and it is recognized in global chronostratigraphic charts used by geologists and paleontologists engaged with the International Commission on Stratigraphy, International Union of Geological Sciences, and regional stratigraphic agencies.
Definition and Chronostratigraphy
The Priabonian was formally ratified by the International Commission on Stratigraphy and characterized using a Global Boundary Stratotype Section and Point (GSSP) approach similar to that employed for the Campanian, Santonian, and Maastrichtian stages. Its lower boundary is correlated with calcareous nannofossil and planktonic foraminiferal events tied to sections such as the type area near Priabona in Vicenza province, Italy, and comparable reference sections in Italy, Austria, France, United Kingdom, Germany, and Spain. Correlation frameworks use magnetostratigraphy correlated to chrons like C19r and isotope stratigraphy including records from the Paleocene–Eocene Thermal Maximum (for context) and later events recorded in deep-sea drill cores from the Ocean Drilling Program and Integrated Ocean Drilling Program. Biostratigraphic zones linking the Priabonian employ standard zonations developed by researchers associated with the International Paleontological Association, European Micropalaeontological Societies, and national surveys such as the British Geological Survey and the United States Geological Survey.
Geological Setting and Paleoenvironments
Depositional settings of Priabonian strata include shelf carbonates, hemipelagic marls, deltaic sandstones, and continental siliciclastics exposed in basins like the Paris Basin, Basin and Range Province, Adriatic Basin, Baltic Basin, Pannonian Basin, and North Sea Basin. Paleoenvironments reconstructed from sites such as the Messel Pit, Walton-on-the-Naze, Bighorn Basin, Wadi Al-Hitan, and Gulf of Mexico margins show coastal lagoons, offshore upwelling systems, reefal buildups, estuarine complexes, and fluvial floodplains. Interactions between tectonic systems—evident in the Alpine orogeny, Pyrenean orogeny, Himalayan orogeny context—and eustatic changes linked to polar ice growth influenced sedimentation recorded in formations like the Bracklesham Group, London Clay Formation, Green River Formation, and Willwood Formation.
Biostratigraphy and Key Fossil Assemblages
The Priabonian yields rich faunas and floras used for biostratigraphic correlation, including planktonic foraminifera such as species recognized by workers from the Palaeontological Association and European Association of Vertebrate Palaeontologists, calcareous nannoplankton exploited by researchers at the Nannoplankton Working Group, and dinoflagellate cyst assemblages documented by the International Nannofossil Working Group. Notable fossil localities include the Messel Pit Fossil Site, Lothagam, Quercy Phosphorites, Fayum Depression, Siwalik Group outcrops, and Chilga Beds. Vertebrate assemblages contain archaeocete cetaceans studied by teams associated with Natural History Museum, London, early primates investigated by specialists linked to American Museum of Natural History and Smithsonian Institution, and perissodactyls and artiodactyls described in monographs from the Paleontological Society. Marine invertebrate faunas include corals compared by researchers from the International Coral Reef Society, bivalves and gastropods catalogued in collections at the Museum für Naturkunde, Berlin and the Muséum national d'Histoire naturelle, and echinoids and brachiopods correlated with work from the Royal Belgian Institute of Natural Sciences.
Major Regional Correlations and Formations
Key formations assigned to the Priabonian or correlated across regions include the London Clay Formation, Bracklesham Group, Headon Hill Formation, Ile de France exposures, Limagne Graben sequences, Kerguelen Plateau sediments, Gabon Basin deposits, Florence Formation analogues, and North American equivalents like the Chadron Formation and Brule Formation. Correlations employ floras comparable to those from the Green River Formation and faunal links to Eocene-Oligocene transitional units such as the Chubut Formation and Sarmiento Formation. Marine correlations use deep-sea cores from the Leg 154 and Leg 208 drilling programs, while continental correlations draw on magnetostratigraphic and isotope datasets from institutions including the Geological Survey of Canada and the National Oceanic and Atmospheric Administration.
Climate and Extinction Events
The Priabonian documents a global cooling trend preceding the Eocene–Oligocene extinction event and the establishment of Antarctic glaciation linked to tectonic gateway changes like the opening of the Tasmanian Gateway and the narrowing of connections at the Tethys Sea. Isotopic records from researchers at Lamont–Doherty Earth Observatory, Scripps Institution of Oceanography, and the Max Planck Institute for Chemistry reveal oxygen and carbon isotope excursions consistent with declining greenhouse conditions. Biotic turnovers documented by paleobotanists at the Royal Botanic Gardens, Kew and vertebrate paleontologists at the Field Museum indicate extirpations and radiations among marine plankton, reef corals, and terrestrial mammals culminating near the Eocene–Oligocene boundary and recognized in stratigraphic syntheses by the International Geoscience Programme.
History of Study and Nomenclature
The name derives from stratigraphic work in northeastern Italy where early descriptions were published by continental geologists associated with the Italian Geological Society and the Università degli Studi di Padova. Subsequent formalization involved committees of the International Commission on Stratigraphy and contributions by scholars affiliated with the University of Vienna, University of Paris, University of Oxford, University of Cambridge, and the University of California, Berkeley. Classic monographs and synthesis volumes appeared in outlets connected to the Geological Society of London, Cambridge University Press, and national geological surveys, while ongoing revisions continue through collaborative projects involving the International Union of Geological Sciences and regional academic consortia.