Triassic System

Triassic System
Name	Triassic
Color	#ff7f50
Time start	251.902
Time end	201.36
Time clock	million years ago
Caption	Marine reptile fossils from the Triassic
Before	Permian
After	Jurassic

Triassic System

The Triassic System marks the earliest interval of the Mesozoic Era, spanning the recovery after the Permian–Triassic extinction event and preceding the rise of Jurassic faunas during the Mesozoic Marine Revolution and the early phases of the breakup of Pangaea. It is recognized in global stratigraphy by distinctive fossil assemblages and isotopic signatures used by stratigraphers in bodies such as the International Commission on Stratigraphy and researchers working on the Geologic Time Scale. Key early studies were advanced by geologists affiliated with institutions like the British Geological Survey and the United States Geological Survey.

Definition and Time Span

The Triassic System is defined chronostratigraphically between the end of the Permian and the start of the Jurassic and is globally bounded by markers tied to biostratigraphy and radiometric ages from volcanic ash beds studied by teams at the Swiss Seismological Service and laboratories involved in the Argon–argon dating technique. The Global Boundary Stratotype Section and Point (GSSP) for the base of the Triassic is correlated to sections developed by researchers from the Geological Survey of Norway and comparative work in the Karoo Basin of South Africa and the Zechstein Basin of Germany. Long-term refinement of the start and end dates has engaged scientists from the University of Oxford, Smithsonian Institution, and the Chinese Academy of Sciences.

Stratigraphy and Subdivisions

Formal subdivisions of the System are the Early, Middle, and Late epochs, corresponding to the Induan, Olenekian, Anisian, Ladinian, Carnian, and Norian and Rhaetian stages in regional schemes developed by stratigraphers at the Geological Society of America and the Paleontological Society. Stratigraphic frameworks integrate lithostratigraphic units such as the Chinle Formation in United States, the Werfen Formation in Austria, and the Los Molles Formation in Argentina with biostratigraphic markers like ammonoid zonations used by paleontologists from the Natural History Museum, London and the Muséum national d'Histoire naturelle. Correlation across basins relies on magnetostratigraphy, chemostratigraphy (carbonate δ13C excursions), and sequence stratigraphy practices refined in studies at the University of California, Berkeley and the Max Planck Institute for Chemistry.

Paleogeography and Climate

During the Triassic, continental configurations were dominated by the supercontinent Pangaea with the Tethys Ocean to the east and the Panthalassa ocean to the west; reconstructions were produced by teams at the University of Texas at Austin and Plymouth University. Climate models from researchers at the National Center for Atmospheric Research and NASA indicate strong continental interior aridity, monsoonal belts, and episodic greenhouse conditions influenced by volcanic outpourings associated with the Central Atlantic Magmatic Province and mantle plume activity studied through comparisons with the Deccan Traps and Siberian Traps. Paleoclimatic proxies, including stable isotopes and paleosol analyses by groups at the University of Minnesota and the Geological Survey of Canada, document transitions from harsh early Triassic warmth to more humid intervals in the Carnian Pluvial Episode highlighted by teams affiliated with the University of Milan and Universidad Nacional Autónoma de México.

Paleontology and Major Biotic Events

The Triassic witnessed the diversification of archosaurs, early dinosaurs, synapsids, and marine reptiles; prominent taxa were described by researchers at institutions like the American Museum of Natural History, Field Museum of Natural History, and Museo Argentino de Ciencias Naturales. Key events include ecological recovery after the Permian–Triassic extinction event, the rise of marine ammonoids and conodonts used by biostratigraphers at the Natural History Museum, Vienna, and the Carnian Pluvial Episode associated with turnovers documented in studies from the University of Zurich and the University of Sao Paulo. Fossil Lagerstätten such as the Ischigualasto Formation, the Holzmaden shale (Posidonia Shale), and the Endothyrid Limestone preserve early dinosaurs, rauisuchians, temnospondyl amphibians, and early lepidosauromorphs collected by teams from the University of Buenos Aires, Staatliches Museum für Naturkunde Stuttgart, and the Royal Ontario Museum.

Tectonics and Basin Development

Tectonic evolution during the Triassic includes rift initiation and passive margin development linked to the breakup of Pangaea and formation of the Central Atlantic rift, investigated by geophysicists at the Scripps Institution of Oceanography and the Woods Hole Oceanographic Institution. Major basins—such as the Paris Basin, North Sea Basin, Karoo Basin, and the Tethyan basins—record syn-rift sedimentation, volcanic sequences tied to the Central Atlantic Magmatic Province, and subsidence histories reconstructed by researchers from the Institut de Physique du Globe de Paris and the Norwegian Geological Survey. These tectonic processes controlled sediment supply, paleogeography, and habitat distribution studied in integrated basin models produced by the United States Geological Survey and industry groups like Shell's exploration teams.

Sedimentary Environments and Lithology

Triassic strata include fluvial red beds, aeolian dunes, lacustrine shales, carbonate platforms, and shallow marine sandstones and limestones; classic lithologies are seen in the Bunter Sandstone of United Kingdom, the Keuper sequences in Germany, and the Dolomites in Italy. Sedimentologists at the University of Leeds and the ETH Zurich have documented cyclicity driven by Milankovitch forcing, evaporitic deposits tied to restricted basins like the Zechstein evaporites, and storm-influenced shelf deposits preserved in the Muschelkalk. Diagenetic studies and reservoir characterizations have been advanced by collaborations between the Oil and Gas Authority (United Kingdom) and university research groups.

Economic Resources and Uses

Triassic formations host hydrocarbon reservoirs, evaporite minerals, industrial aggregates, and sources of construction stone; examples include oil and gas in the North Sea Basin, potash and halite in the Zechstein Basin, and widespread use of Triassic sandstones as dimension stone in historic architecture studied by conservation teams at the Victoria and Albert Museum. Reservoir characterization and exploration have involved companies such as BP and Equinor in cooperation with academic partners at the Imperial College London and the University of Aberdeen, while mineral extraction operations are regulated by agencies including the European Commission and national geological surveys.

Category:Geologic periods