Meishan GSSP, Changxing, Zhejiang

Assembled from 25 blocks · 2 evidence · 17 related

1. Story
2. A quarried limestone section in Changxing County, Zhejiang Province, that holds the golden spike defining the base of the Triassic and therefore the top of the Permian — the boundary at the largest extinction in the fossil record. Meishan is the reference section for the most severe biotic crisis known, and it is also where the crisis was converted from a stratigraphic interval into a duration. The section contains several volcanic ash beds interbedded with the fossiliferous limestone within a few metres of the boundary, and those ash beds contain zircons. High-precision uranium–lead dating of them by Burgess, Bowring and Shen in 2014 placed the boundary at 251.902 ± 0.024 million years and constrained the main extinction pulse to roughly sixty thousand years, with an uncertainty of about the same size. That result is what makes the end-Permian arguable as a rate problem rather than a list of casualties: a loss of that magnitude spread over ten million years and one compressed into sixty thousand demand entirely different mechanisms.
3. Knowledge
4. Global Boundary Stratotype Section and Point
5. Meishan GSSP, Changxing, Zhejiang
6. The end-Permian mass extinction
7. Connections
8. The end-Permian mass extinction
9. Global Boundary Stratotype Section and Point
10. The end-Permian mass extinction
11. The end-Permian extinction is resolved to about sixty thousand years
12. Meishan GSSP, Changxing, Zhejiang
13. Siberian Traps large igneous province
14. Mass extinction
15. The end-Triassic mass extinction
16. Meishan GSSP, Changxing, Zhejiang
17. Radiometric dating
18. The Late Devonian crisis
19. International Commission on Stratigraphy
20. Fortune Head GSSP, Newfoundland
21. Meishan GSSP, Changxing, Zhejiang
22. The numerical age of the Cambrian base is revised to 538.8 Ma
23. Evidence
24. Supports the Permian–Triassic boundary age of 251.902 ± 0.024 Ma from Meishan zircons and the constraint of the main extinction pulse to roughly sixty thousand years. V55 verification basis: this session had no network access to any source — WebFetch was egress-blocked and the WebSearch budget was exhausted — so the cited work was not retrieved and its pagination was not re-checked. Volume and page range are quoted from standing knowledge and were not re-checked.
25. Supports the stage and period boundary ages used throughout this pack, including the Cambrian base at 538.8 ± 0.2 Ma on recent editions against 541.0 ± 1.0 Ma on earlier ones. V55 verification basis: this session had no network access to any source — WebFetch was egress-blocked and the WebSearch budget was exhausted — so the cited work was not retrieved and its pagination was not re-checked. No chart edition was opened, so the boundary figures are quoted from standing knowledge of the chart rather than read from it, and the edition in which the Cambrian base changed is not identified.