The Triassic time scale is poorly constrained due to a paucity of high-precision radiometric ages. We present a 206Pb/238U age of 230.91 0.33 Ma (error includes all known sources) for zircon from an ash bed in the upper Carnian (Upper Triassic) of southern\ud Italy that requires a major revision of the Triassic time scale. For example, the Norian stage is lengthened to more than 20 m.y. The section containing the ash bed is correlated with other Tethyan sections and, indirectly, with the Newark astronomical polarity time scale (APTS). The dating provides also a minimum age for some important climatic and biotic events that occurred during the Carnian. We note a coincidence between these\ud events and the eruption of the large igneous province of Wrangellia, but the possible link between volcanism and climatic and biotic events requires further scrutiny

Paolo Mietto, Stefano Manfrin, Nereo Preto, Manuel Rigo, Guido Roghi, Stefano Furin, Piero Gianolla, Renato Posenato, Giovanni Muttoni, Alda Nicora, Nicoletta Buratti, Simonetta Cirilli, Christoph Spötl, Jahandar Ramezani, and Samuel A. Bowring. Episodes 2012;35:414-30. https://doi.org/10.18814/epiiugs/2012/v35i3/003

The role of ocean anoxia as a cause of the end-Triassic marine mass extinction is widely debated. Here, we present carbonate-associated sulfate δ³⁴S data from sections spanning the Late Triassic–Early Jurassic transition, which document synchronous large positive excursions on a global scale occurring in ~50 thousand years. Biogeochemical modeling demonstrates that this S isotope perturbation is best explained by a fivefold increase in global pyrite burial, consistent with large-scale development of marine anoxia on the Panthalassa margin and northwest European shelf. This pyrite burial event coincides with the loss of Triassic taxa seen in the studied sections. Modeling results also indicate that the pre-event ocean sulfate concentration was low (<1 millimolar), a common feature of many Phanerozoic deoxygenation events. We propose that sulfate scarcity preconditions oceans for the development of anoxia during rapid warming events by increasing the benthic methane flux and the resulting bottom-water oxygen demand.