Triassic Period
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| Triassic Period | |
|---|---|
| Name | Triassic |
| Color | #ffc0cb |
| Time start | 251.902 |
| Time end | 201.36 |
| Caption | Marine reptile fossils from Triassic strata |
| Former domains | Pangaea |
Triassic Period The Triassic Period marks the first period of the Mesozoic Era, following the Permian–Triassic extinction event and preceding the Jurassic Period and Cretaceous Period. It is characterized by the recovery of global ecosystems, the initial diversification of dinosaurs and mammal-line relatives, and major changes in paleogeography associated with the supercontinent Pangaea. Geochronological calibration and stratigraphic correlations have been advanced by institutions such as the International Commission on Stratigraphy and studies from the United States Geological Survey and Geological Survey of Canada.
Overview
The Triassic began after the mass extinction recorded in the Siberian Traps-related collapse at the end of the Permian Period and witnessed biotic radiations that set the stage for Mesozoic faunas dominated later by Theropoda and Sauropodomorpha. Major fossiliferous basins such as the Newark Basin, the Germanic Basin, the Karoo Supergroup, and the Ischigualasto Formation preserve vertebrate and plant assemblages that illuminate shifts toward archosaur dominance, the origin of pterosaurs, and early cynodont evolution. Chronostratigraphic refinement relies on biostratigraphy using index fossils like ammonoids and conodonts, and on radiometric dates from volcanic ash layers studied at universities including University of Oxford and Caltech.
Stratigraphy and subdivisions
Triassic stratigraphy is divided into Early, Middle, and Late epochs with global stages such as the Induan, Olenekian, Anisian, Ladinian, Carnian, Norian, and Rhaetian. The Global Boundary Stratotype Section and Point framework and votes by the International Commission on Stratigraphy formalized many boundaries using sections in places like the GSSP at river sections and marine outcrops. Regional chronostratigraphic schemes—employed in basins like the Tethys Ocean margins, the Western Interior Basin, and the South China Block—use local formations such as the Dockum Group and the Chañares Formation to correlate terrestrial and marine records. Advances in magnetostratigraphy, chemostratigraphy, and isotopic studies by groups at the Smithsonian Institution and Max Planck Society have refined correlations across continents.
Paleogeography and climate
During the Triassic, continental configuration was dominated by Pangaea with the vast Tethys Ocean to the east; paleogeographic reconstructions by teams at the Paleomap Project and University of California, Santa Cruz show extensive interior aridity in regions like the Sahara and seasonal monsoons at margins near the North Atlantic Opening. Climate proxies from stalagmites, loess, and marine carbonate records in the Tethys and Panthalassa suggest overall greenhouse conditions punctuated by transient cooling events linked to volcanism in large igneous provinces such as the Wrangellia and eruptions related to the Central Atlantic Magmatic Province. Sedimentary records in the Karoo Basin, Zechstein Basin, and Molasse Basin record evaporites, red beds, and fluvial systems reflecting fluctuating hydrology.
Major life and evolutionary events
Biotic recovery after the Permian–Triassic extinction event featured adaptive radiations among archosauromorphs, lepidosauromorphs, and synapsid lineages including early mammaliaforms. Notable faunas from the Ischigualasto Formation, the Chinle Formation, and the Yunnan deposits document early dinosauriforms, rhynchosaurs, and phytosaurs coexisting with temnospondyl amphibians and diverse plant assemblages including Czekanowskiales and early corystosperm-dominated floras. Marine realms saw recovery of ammonoid and conodont diversity, the proliferation of bivalves and brachiopods, and the radiation of marine reptiles such as Ichthyosauria and Nothosauria. Microfossil and palynological records used by researchers at institutions like University of Chicago and University of Zurich track changes in terrestrial vegetation and climate-driven turnovers.
Extinction events and recovery
The Triassic interval includes significant biotic crises: the initial recovery phase post-Permian–Triassic extinction event and the notable End-Triassic extinction event near the Triassic–Jurassic boundary, linked to magmatism of the Central Atlantic Magmatic Province and associated carbon cycle perturbations recorded at sections in the Bay of Fundy and Flemish Cap. These events precipitated turnovers that opened ecological space for dinosaur dominance in the Jurassic Period and affected marine groups including reef calcifiers, scleractinian corals, and conodonts. Long-term recovery trajectories are documented in successions studied by teams affiliated with the Natural History Museum, London and the Field Museum of Natural History.
Economic significance and geology
Triassic strata host economically important resources: reservoirs and source rocks for petroleum in basins such as the North Sea, Gulf of Mexico, and Basrah Basin; evaporite deposits exploited as rock salt and potash in the Zechstein and Khorat sequences; and mineral deposits including uranium and copper in zones like the Mount Isa and Athabasca Basin. Engineering geology for Triassic redbed formations influences groundwater and construction projects in regions governed by agencies like the United States Environmental Protection Agency and the Environment Agency (England). Hydrocarbon exploration, paleoclimate reconstructions, and stratigraphic studies are ongoing at universities and national surveys including Imperial College London, the Bureau of Economic Geology, and the Geological Survey of India.