Permian–Triassic Extinction ('The Great Dying')

Earth's most severe Phanerozoic mass extinction (~251.9 Ma), eliminating ~81% of marine species at the Paleozoic–Mesozoic boundary.

Specifications & Metrics

type: Standard Stratigraphic Chronology
timespan: 251.902 ± 0.024 Ma (main extinction pulse ~60,000 years)
defining boundary: First appearance of conodont Hindeodus parvus at Meishan GSSP, Zhejiang, China
proponents or Body: John Phillips (defined Paleozoic/Mesozoic boundary, 1840); ICS
key evidence: Siberian Traps flood basalts, negative δ¹³C excursion, marine anoxia/euxinia, fungal spike

Dated by high-precision uranium–lead zircon geochronology at Meishan, China, to 251.902 Ma, the Permian–Triassic boundary marks Earth's most severe mass extinction, wiping out ~81% of marine species (including all trilobites and rugose corals) and ~70% of terrestrial vertebrate families.
The extinction coincided with the eruption of the Siberian Traps large igneous province, which extruded 2 to 4 million km³ of flood basalt and intruded coal and evaporite basins, releasing massive volumes of CO₂, methane, sulfur dioxide, and halocarbons.
Global sea-surface temperatures rose by 8–10 °C (exceeding 35–40 °C in the tropics), driving widespread ocean anoxia, hydrogen sulfide euxinia, and a 5- to 10-million-year 'coal gap' before complex reef and forest ecosystems recovered in the Middle Triassic.