The Late Devonian crisis

Assembled from 32 blocks · 2 evidence · 18 related

1. Story
2. The least event-like of the Big Five and the one that most tests the definition. Rather than a single horizon it is a prolonged interval of elevated extinction punctuated by two severe pulses: the Kellwasser event near the Frasnian–Famennian boundary around 372 million years ago, and the Hangenberg event at the Devonian–Carboniferous boundary around 359 million years ago. Both are associated with black shales indicating widespread ocean anoxia. The most-discussed hypothesis links the crisis to the spread of the first forests and deep-rooted vascular plants across the continents, which would have accelerated chemical weathering, delivered nutrients to the sea, driven eutrophication and anoxia, and drawn down atmospheric carbon dioxide enough to cool the climate. The Devonian reef systems, built by stromatoporoids and tabulate corals, collapsed and were never rebuilt in the same form. Several analysts argue that the interval is better characterised as a collapse in the rate of new species originating than as a spike in the rate of species dying.
3. Knowledge
4. International Commission on Stratigraphy
5. Mass extinction
6. The end-Permian mass extinction
7. The Late Devonian crisis
8. Connections
9. The end-Ordovician mass extinction
10. Mass extinction
11. The end-Permian mass extinction
12. International Commission on Stratigraphy
13. Radiometric dating
14. The end-Permian mass extinction
15. The Cretaceous–Palaeogene mass extinction
16. The end-Ordovician mass extinction
17. The Late Devonian crisis
18. The end-Triassic mass extinction
19. Meishan GSSP, Changxing, Zhejiang
20. Siberian Traps large igneous province
21. Mass extinction
22. The end-Triassic mass extinction
23. Meishan GSSP, Changxing, Zhejiang
24. Radiometric dating
25. The Late Devonian crisis
26. Global Boundary Stratotype Section and Point
27. The end-Ordovician mass extinction
28. The Late Devonian crisis
29. The numerical age of the Cambrian base is revised to 538.8 Ma
30. Evidence
31. 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.
32. Supports the general Precambrian narrative used here: stromatolite biogenicity reasoning, banded iron formation requirements, endosymbiotic origin of organelles and the framing of mass extinction as a measurement problem. Published in 2003, so it predates the 2016, 2018 and 2024 results also cited in this pack. 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.