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| Permian–Triassic boundary | |
|---|---|
| Name | Permian–Triassic boundary |
| Type | Boundary |
| Period | Permian–Triassic |
| Location | Global |
Permian–Triassic boundary is the globally recognized turnover horizon marking the transition between the Permian and Triassic periods, associated with the largest known Phanerozoic mass extinction and profound changes recorded in marine, terrestrial, and atmospheric systems. The boundary is identified in stratigraphic sections, paleontological assemblages, geochemical proxies, and radiometric age constraints that connect localities such as Meishan, Karoo Basin, Zigong, Antarctic Peninsula, and Guilin across the Pangea supercontinent and its surrounding basins. Interpretations of the event draw on work from institutions including the Geological Society of America, International Commission on Stratigraphy, and researchers linked to projects at Stanford University, Cambridge University, Chinese Academy of Sciences, and University of California, Berkeley.
Stratigraphic recognition of the boundary relies on type sections like the stratotype at Meishan in Zhejiang province, alongside reference sections in the Karoo Basin of South Africa, the Dolomites in Italy, and the Svalbard archipelago, with lithologies ranging from shallow marine limestones and shales to terrestrial fluvial sandstones and continental coal seams. Correlation uses fossil assemblages such as the conodont Clarkina, ammonoids like Otoceras, and fusulinids documented by paleontologists working in sites tied to institutions like Natural History Museum, London and Smithsonian Institution, while sequence stratigraphy integrates work by stratigraphers linked to the International Geoscience Programme and the Society of Economic Geologists. Taphonomic and sedimentological analyses from researchers affiliated with University of Tokyo, ETH Zurich, and University of Göttingen have detailed facies changes, unconformities, and event beds including ejecta-like layers reported near Siberian Traps-proximal basins.
The end-Permian extinction eliminated an estimated >90% of marine species and ~70% of terrestrial vertebrate genera according to quantitative studies by teams at Harvard University, University of Washington, and Yale University, and disrupted ecosystems studied by paleobiologists from University of Chicago and University of Utah. Key losses include rugose corals, many brachiopod lineages, and trilobites already in decline since work featured by Montreal Paleontology Museum researchers, while terrestrial consequences affected synapsid clades studied by paleontologists connected to American Museum of Natural History and Royal Ontario Museum. Biotic crisis evidence stems from mass die-off horizons, larval calamities recorded in conodont records interpreted by laboratories at University of California, Los Angeles and extinction patterns synthesized in reviews published with contributors from Princeton University and University of Oxford.
Hypotheses proposed by geoscientists at University of Edinburgh, University of Leeds, and Uppsala University implicate multiple interacting drivers: voluminous volcanism from the Siberian Traps flood basalt province, rapid greenhouse forcing involving carbon emissions examined by climate modelers at NASA Goddard Institute for Space Studies and Max Planck Institute for Meteorology, oceanic anoxia studied by geochemists at Woods Hole Oceanographic Institution and Scripps Institution of Oceanography, and methane release from gas hydrate reservoirs researched by teams at Lamont–Doherty Earth Observatory and University of Bergen. Additional mechanisms considered include acidification assessed by experimentalists linked to University of South Florida and hyperthermal-induced euxinia documented by collaborative work involving Institut de Physique du Globe de Paris and GFZ German Research Centre for Geosciences.
Carbon isotope excursions (δ13C) recorded in carbonate and organic fractions from analyses at University of Leeds, Caltech, and Peking University document large negative shifts coincident with extinction horizons, while mercury anomalies tied to large igneous province emplacement have been reported by teams at University of California, Santa Barbara and University of Southampton. Sulfur isotope perturbations studied by researchers at University of Bristol and University of Minnesota indicate widespread marine sulfate reduction, and nitrogen isotope records from work at University of Copenhagen and Ohio State University imply alterations in the nitrogen cycle. Redox proxies such as molybdenum and iron speciation measured at University of Edinburgh and University of Geneva support episodes of widespread oceanic anoxia and euxinia, corroborated by biomarkers analyzed at University of St Andrews and University of Groningen.
High-precision U–Pb zircon geochronology from ash beds in sections prepared and analyzed at Arizona State University, ETH Zurich, and University of Cambridge provides calibrated ages that constrain the boundary to about 252 million years ago, with Argon–argon dating applied by laboratories at Berkeley Geochronology Center and Geological Survey of Japan refining eruption durations for the Siberian Traps. Magnetostratigraphy studies tied to work at Columbia University and cyclostratigraphy approaches developed by researchers at University of Oslo integrate paleomagnetic and orbital signals, while biostratigraphic correlation using conodonts and ammonoids remains coordinated through networks including the International Paleontological Association and regional geological surveys like the Geological Survey of Canada.
Post-boundary recovery trajectories documented by researchers at University of Vienna, Monash University, and University of Sydney show protracted ecosystem restructuring with delayed reef resurgence, opportunistic disaster taxa, and vertebrate radiations such as early archosaurs traced by paleontologists from Field Museum and Staatliches Museum für Naturkunde Stuttgart. Carbonate platform collapse and later microbialite proliferation are studied in contexts investigated by teams at University of Queensland and Chinese Academy of Sciences, while floral turnovers and coal gap phenomena have been analyzed by botanists at Royal Botanic Gardens, Kew and University of Göttingen.
Regional expressions vary: marine anoxia and black shale deposition documented in the Arctic, Tethys, and Panthalassa margins contrast with continental red beds and vertebrate-bearing formations in the Karoo Basin, Zhangjiakou, and Newark Supergroup, synthesized through international collaborations including the International Union of Geological Sciences and basin studies funded by agencies like the National Science Foundation and Natural Environment Research Council. Global correlation employs integrated stratigraphy combining biostratigraphy, chemostratigraphy, magnetostratigraphy, and radiometric ages developed by consortia at International Commission on Stratigraphy and regional geological surveys such as the Chinese Geological Survey and Geological Survey of South Africa.
Category:Mass extinctions Category:Stratigraphy Category:Paleontology