Devonian
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| Devonian | |
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| Name | Devonian |
| Caption | Reconstruction of a Devonian landscape |
| Era | Paleozoic |
| Period | Devonian |
| Time start | 419.2 |
| Time end | 358.9 |
| Time uncertainty | 0.3–0.4 Ma |
| Named by | Adam Sedgwick |
| Named for | Devonshire |
Devonian The Devonian was a geologic period of the Paleozoic Era noted for extensive marine radiation and major terrestrial colonization. It is recognized in international stratigraphy by a succession of stage names and type sections that were established through work by geologists and paleontologists across Europe and North America. Major contributors to its study include Adam Sedgwick, Roderick Murchison, Charles Lyell, Louis Agassiz, and William Buckland.
Etymology and historical research
The name derives from the English county of Devon where early 19th‑century stratigraphers such as Adam Sedgwick and Roderick Murchison correlated sedimentary sequences; these investigators published in venues like the Geological Society of London and corresponded with contemporaries including Charles Lyell and William Buckland. Subsequent development of Devonian stratigraphy involved international figures such as Charles Lapworth, who proposed chronostratigraphic schemes that influenced organizations like the International Commission on Stratigraphy and the United States Geological Survey. Key type localities and stratotypes were formalized through work by researchers at institutions like the Natural History Museum, London, the Smithsonian Institution, the Royal Society of London, and the Geological Survey of Canada.
Geologic setting and time scale
The period is positioned between the Silurian and the Carboniferous in the Paleozoic and is subdivided into Early, Middle, and Late epochs with stages such as the Lochkovian, Pragian, Emsian, Eifelian, Givetian, Frasnian, and Fammenian defined by biostratigraphic markers. Global chronostratigraphy for the interval was ratified by panels of the International Commission on Stratigraphy and published in frameworks used by the United States Geological Survey, the British Geological Survey, and the Geological Survey of Canada. Radiometric calibration has employed isotopic systems studied at institutions like the Geological Survey of Finland and laboratories at the University of Cambridge and California Institute of Technology to refine absolute ages. Tectonic settings during the period involved continents such as Laurentia, Baltica, Siberia, and the microcontinent Avalonia interacting in orogenic events linked to the assembly of Euramerica and the formation of the Antler Orogeny and early stages of the Variscan orogeny.
Paleogeography and climate
Paleogeographic reconstructions published by researchers at Paleomap Project, University of Chicago, University of Michigan, and Utrecht University show shallow epicontinental seas across cratons including Laurentia, Baltica, and Siberia, with the supercontinent Gondwana occupying high southern latitudes. Climate proxies developed by teams at ETH Zurich, University of Texas at Austin, University of Oxford, and Lamont–Doherty Earth Observatory indicate generally warm greenhouse conditions punctuated by cooling episodes, and oxygenation events recorded in studies from GEOMAR Helmholtz Centre and the Max Planck Institute for Chemistry. Sea level changes tied to eustatic fluctuations are documented in basin analyses by the Bureau of Economic Geology and the Norwegian Petroleum Directorate, while carbonate platforms and reef systems were prominent in areas mapped by the Geological Survey of Norway and the Australian Geological Survey Organisation.
Major life and evolutionary developments
Marine invertebrate radiations involved faunas studied by paleontologists at the Natural History Museum, London, Royal Ontario Museum, Yale Peabody Museum, and the Smithsonian Institution, including diverse brachiopods, crinoids, bryozoans, ammonoids, and trilobites whose evolutionary patterns were analyzed by researchers such as Elkanah Billings and Alfred Romer. Fish diversification—particularly of jawless forms, placoderms, acanthodians, sarcopterygians, and actinopterygians—was documented in classic finds from localities studied by teams at University of Michigan, Field Museum, Natural History Museum of Los Angeles County, and University of Chicago. The appearance and radiation of early tetrapodomorphs and derived tetrapods were advanced by work of Jenny Clack and Per Ahlberg on fossils from sites correlated with researchers at the Royal Swedish Academy of Sciences. Terrestrialization included expansion of lycophytes, sphenopsids, and early progymnosperms; major plant assemblage studies were conducted by scholars at Royal Botanic Gardens, Kew, University of Göttingen, and University of Birmingham. Development of early forests and soils influenced atmospheric composition as modeled by groups at NASA Goddard, Carnegie Institution for Science, and Institut für Geowissenschaften, Mainz.
Major fossil assemblages and biostratigraphy
Classic Devonian fossil Lagerstätten include sites investigated by teams at the Miguasha National Park (studied by David Robison and Jean-Bernard Caron), the Rhynie chert worked on by Charles Wellman and Jenny Clack, and the Gogo Formation researched by the Western Australian Museum and Curtin University. Ammonoid, conodont, and brachiopod zonations developed by the International Subcommission on Devonian Stratigraphy and researchers at Université Montpellier and University of Alberta provide high‑resolution correlation tools used by the Geological Survey of Canada and the United States Geological Survey. Museum collections at Natural History Museum, London, Smithsonian Institution, Muséum national d'Histoire naturelle, and Royal Ontario Museum preserve key taxa that underpin biostratigraphic frameworks.
Extinction events and boundary transitions
The Late Devonian includes major biodiversity crises, especially the Frasnian–Fammenian extinction investigated by paleobiologists at University of Edinburgh, University of Kansas, University of Cincinnati, and Vrije Universiteit Amsterdam. Proposed drivers examined by interdisciplinary teams at Lamont–Doherty Earth Observatory, Max Planck Institute, University of Chicago, and ETH Zurich include marine anoxia, global cooling, volcanism (e.g., Kola‑Dnieper traps models), and extraterrestrial impact hypotheses considered by researchers at Smithsonian Institution and Planetary Science Institute. Transition into the Carboniferous involved faunal turnovers documented in stratigraphic syntheses by the International Commission on Stratigraphy and regional surveys from the British Geological Survey and Geological Survey of India.
Economic significance and geologic legacy
Devonian strata host significant hydrocarbon reservoirs and mineral deposits documented by the American Association of Petroleum Geologists, the Norwegian Petroleum Directorate, and national surveys like the Geological Survey of Canada and the United States Geological Survey. Major petroleum plays include Devonian reefs and carbonates studied in basins by companies such as ExxonMobil, BP, and Chevron collaborating with universities like University of Calgary and University of Aberdeen. Devonian black shales are source rocks for shale gas assessed by the Energy Information Administration and exploited with techniques developed by Halliburton and Schlumberger. Economic minerals—lead, zinc, and barite—are associated with Devonian dolostones and volcaniclastic sequences mined in regions surveyed by the British Geological Survey and the Australian Bureau of Mineral Resources.
Category:Paleozoic