Fortune Head GSSP, Newfoundland

Assembled from 32 blocks · 1 evidence · 25 related

1. Story
2. The headland on the Burin Peninsula of Newfoundland whose exposed section carries the golden spike defining the base of the Cambrian, and therefore the base of the Phanerozoic — the largest single division in the geological time scale. The boundary is placed at the first appearance of the trace fossil Treptichnus pedum, a distinctive burrow made by an unknown animal probing sediment in a repeated stepwise pattern. Choosing a burrow rather than a body fossil looks perverse until the requirement is understood: a boundary marker must be recognisable in ordinary marine sediment worldwide, and soft-bodied Cambrian animals are only preserved in rare exceptional deposits. The choice has a real cost. Treptichnus pedum is now known from slightly below the boundary in some sections, so the marker is not quite as sharp as it was believed to be when the GSSP was ratified, and the numerical age attached to the boundary has moved — from 542 to 541 to 538.8 Ma across successive chart editions — while the physical point in the outcrop has not moved at all.
3. Knowledge
4. Global Boundary Stratotype Section and Point
5. Fortune Head GSSP, Newfoundland
6. The Cambrian explosion
7. Connections
8. The Cambrian explosion
9. Global Boundary Stratotype Section and Point
10. The Cambrian explosion
11. The numerical age of the Cambrian base is revised to 538.8 Ma
12. Molecular clock dating
13. Ediacara Hills, Flinders Ranges
14. Fortune Head GSSP, Newfoundland
15. Konservat-Lagerstätte (exceptional preservation)
16. Burgess Shale, Yoho National Park
17. Anomalocaris
18. Chengjiang fossil site, Yunnan
19. The Great Oxidation Event
20. The end-Ordovician mass extinction
21. Fortune Head GSSP, Newfoundland
22. Burgess Shale, Yoho National Park
23. Chengjiang fossil site, Yunnan
24. Anomalocaris
25. Konservat-Lagerstätte (exceptional preservation)
26. Molecular clock dating
27. International Commission on Stratigraphy
28. Fortune Head GSSP, Newfoundland
29. Meishan GSSP, Changxing, Zhejiang
30. The numerical age of the Cambrian base is revised to 538.8 Ma
31. Evidence
32. 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.