The Cretaceous–Palaeogene mass extinction

Assembled from 37 blocks · 3 evidence · 19 related

1. Story
2. The extinction that removed the non-avian dinosaurs, the ammonites, the large marine reptiles and, on the usual estimate, around three quarters of species. It is the best-understood of the five because it has a physical cause that can be pointed at: a global iridium-rich boundary layer, shocked quartz, impact spherules, and a crater of the right size and age at Chicxulub. High-precision argon-40/argon-39 dating published in 2013 placed the boundary at 66.043 ± 0.043 million years and showed the impact and the extinction horizon to be indistinguishable in time. The kill mechanism is generally attributed less to the impact itself than to what followed — sulfate aerosols and soot causing months to years of darkness and cooling, shutting down photosynthesis on land and in the surface ocean. A serious alternative and complementary hypothesis points to the Deccan Traps in India, erupting across the same interval; the current mainstream position, argued in a large multi-author 2010 review, is that the impact was the proximate cause while accepting that Deccan volcanism was already stressing the biosphere.
3. Knowledge
4. Mass extinction
5. The Cretaceous–Palaeogene iridium anomaly
6. Bottaccione Gorge, Gubbio
7. Chicxulub impact crater, Yucatán
8. The Cretaceous–Palaeogene mass extinction
9. Connections
10. The Cretaceous–Palaeogene iridium anomaly
11. Chicxulub impact crater, Yucatán
12. Mass extinction
13. The Cretaceous–Palaeogene iridium anomaly
14. Bottaccione Gorge, Gubbio
15. The end-Triassic mass extinction
16. The Cretaceous–Palaeogene mass extinction
17. The K–Pg boundary is dated to 66.043 ± 0.043 Ma
18. Chicxulub is identified as the K–Pg impact crater
19. IODP–ICDP Expedition 364 drills the Chicxulub peak ring
20. Radiometric dating
21. The end-Permian mass extinction
22. The Cretaceous–Palaeogene mass extinction
23. The end-Ordovician mass extinction
24. The Late Devonian crisis
25. The end-Triassic mass extinction
26. The Cretaceous–Palaeogene mass extinction
27. Bottaccione Gorge, Gubbio
28. The Cretaceous–Palaeogene mass extinction
29. The Alvarez impact hypothesis is published
30. Chicxulub is identified as the K–Pg impact crater
31. The Cretaceous–Palaeogene iridium anomaly
32. The Cretaceous–Palaeogene mass extinction
33. The Alvarez impact hypothesis is published
34. Evidence
35. Supports the iridium anomaly at Gubbio and Stevns Klint, the siderophile-depletion reasoning and the inference of an impactor about ten kilometres across. 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.
36. Supports the boundary age of 66.043 ± 0.043 Ma and the finding that the Chicxulub impact and the extinction horizon are indistinguishable in time. 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.
37. Supports the multi-author synthesis position that the Chicxulub impact was the proximate cause of the K–Pg extinction, and the global distribution of the boundary layer with its shocked quartz and spherules. The Deccan Traps alternative continued to be argued after this review; that literature is not cited here. 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.