Early Triassic
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| Early Triassic | |
|---|---|
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| Name | Early Triassic |
| Color | #FAD6A5 |
| Time start | 251.902 |
| Time end | 247.2 |
| Caption | Landscapes after the Permian–Triassic extinction |
| Chronological order | Induan, Olenekian |
Early Triassic The Early Triassic marks the first epoch of the Triassic Period and directly follows the Permian and the Permian–Triassic extinction event, initiating recovery intervals documented in geologic time scale studies and stratigraphic sections from formations such as the Sakamena Group, Karoo Supergroup, and Newark Basin. Global records from locations like the Zhongning Basin, Guanling, Spitsbergen, Antarctic Peninsula, and the Tethys Ocean show characteristic lithologies, fossil assemblages, and isotopic excursions that anchor magnetostratigraphy, chemostratigraphy, and biostratigraphy across the Induan and Olenekian ages.
Overview and Chronology
Stratigraphic frameworks developed by the International Commission on Stratigraphy divide the epoch into the Induan and Olenekian ages tied to Global Boundary Stratotype Sections and Points such as sections in the Meishan, Selong, and GSSP candidate sites; magnetostratigraphy and radiometric dates from U-Pb zircon analyses in the Panama Canal Zone, Sierra Nevada, and Nanxiong Basin refine absolute ages. Correlation with regional stages like the Scythian and subdivisions used in the Tethyan Realm integrates paleontological markers such as ammonoid zones, conodont turnovers, and ichnotaxa from the Moenkopi Formation and Buntsandstein Supergroup.
Paleoclimate and Environmental Conditions
Paleoclimate reconstructions using oxygen isotopes from foraminifera, clay mineralogy from the Karoo Basin, and paleosol profiles in the Sydney Basin indicate extreme greenhouse conditions, high atmospheric carbon dioxide levels, and episodes of global warming linked to the Siberian Traps large igneous province and magmatic events in the Wrangellia and Tethyan magmatism provinces. Reconstructed climate gradients, monsoonal intensification inferred from the Chengjiang and Jiangxi basins, and evidence for ocean anoxia from black shales in the Werfen Formation, Vardebukta, and Graphite Peak show repeated carbon cycle perturbations recorded in δ13C excursions and mercury anomalies correlated with volcanic emissions recorded in LIP studies.
Marine Ecosystems and Recovery
Marine recovery patterns documented in faunal assemblages from the Panthalassa margins, Tethys shelves, and epicontinental seas such as the Zealandia and Paraná Basin document low-diversity benthic communities dominated by disaster taxa like the bivalve genus Claraia, opportunistic ammonoids related to Otoceras, and nektonic survivors including early actinopterygian fishes recorded in the Fossil Butte Member. Reef frameworks were replaced by microbialites and sponge-dominated buildups observed in the Wordie Creek Formation and Dienerian facies, while ichthyofaunal recovery involving genera listed in faunal catalogs from Monte San Giorgio, Solnhofen, and Lagerstätten indicates protracted diversification constrained by fluctuating oxygen levels and seawater chemistry.
Terrestrial Flora and Fauna
Plant assemblages preserved in the Karoo Supergroup, Kashmir Basin, and Mesozoic basins show dominance by lycopsids, ferns, and opportunistic pteridosperms with palynological records from the Gondwana and Laurasia margins documenting low-diversity palynofloras and gymnosperm survivors related to Glossopteris-affiliated lineages. Terrestrial vertebrate faunas from localities like the Karoo Basin, Beishan, Lystrosaurus Assemblage Zone, and Russian Platform reveal dicynodonts such as Lystrosaurus, early archosauriforms including Proterosuchus and Erythrosuchus, and temnospondyl amphibians exemplified by Gerrothorax-grade taxa; trace fossils attributed to early archosaur footprints occur in the Moenkopi Formation and Hettangian-correlative strata.
Biotic Recovery and Extinction Patterns
The pattern of biotic recovery is characterized by protracted ecologic upheaval with pulsed extinctions and opportunistic radiations documented in global datasets assembled by institutions including the Natural History Museum, London, Smithsonian Institution, and the Royal Ontario Museum. Diversity curves derived from datasets incorporating occurrences from the Paleobiology Database, regional monographs on the Zeugitana Basin and Svalbard sections, and isotope records from Meishan show asynchronous recovery between marine and terrestrial realms, repeated biodiversity bottlenecks, and evolutionary turnovers that paved the way for the dominance of Archosauria, later radiations recorded in Late Triassic faunas such as those in the Ischigualasto Formation and Chinle Formation.
Tectonics, Paleogeography, and Sea Level
Paleogeographic reconstructions integrating paleomagnetic data from Pangea-adjacent terranes, plate kinematic models by teams at institutions like GFZ Potsdam and USGS, and stratigraphic correlations across the Tethys Ocean and Panthalassa reveal fragmentation dynamics, basin evolution such as the Neuquén Basin and Paris Basin, and sea-level changes tied to thermal subsidence and glacio-eustatic signals debated in syntheses including work from Harvard University and University of California, Berkeley. Continental configurations influenced monsoon systems reconstructed in climate models by groups at NCAR and MPI for Meteorology, which in turn shaped sediment dispersal in deltas recorded in the Chinle Formation and carbonate platforms of the Himalaya margin.
Economic and Paleontological Significance
Early Triassic strata host economically significant resources and scientifically important fossils: coal seams in the Gondwana basins and hydrocarbon source rocks in the Sichuan Basin and North Sea record organic-rich intervals; important vertebrate and invertebrate Lagerstätten such as Chengjiang-like assemblages, Karoo fossil sites, and marine horizons studied by the Geological Society of America and Palaeontological Association provide key evidence for recovery dynamics. Collections in museums including the American Museum of Natural History and research programs at universities such as University of Cambridge underpin ongoing revisions to phylogenies, stratigraphic schemes, and models of biosphere resilience relevant to modern concerns studied by groups at the IPCC and climate research centers.