Banded iron formations

Assembled from 19 blocks · 1 evidence · 22 related

1. Story
2. Laminated chemical sediments alternating iron oxide and silica layers, deposited on a scale nothing on the modern Earth approaches — the Hamersley Basin of Western Australia and the Transvaal Basin of South Africa each contain sequences hundreds of metres thick and hundreds of kilometres across, and they are the source of most of the world's iron ore. They require an ocean that could hold large quantities of dissolved ferrous iron, which is only possible when the deep ocean is anoxic, plus a periodic supply of oxidant to precipitate it. That combination is a signature of a transitional world rather than an oxygenated one. Deposition peaked in the late Archaean and earliest Proterozoic and then largely stopped after about 1.85 billion years ago, with a brief and separate return associated with the Neoproterozoic glaciations. The conventional reading is that the iron ran out because the oceans finally oxidised; a competing reading emphasises deep-ocean sulfide instead. The banding itself — the reason they are called banded — has no agreed explanation.
3. Knowledge
4. Banded iron formations
5. The Great Oxidation Event
6. Connections
7. The Great Oxidation Event
8. The Great Oxidation Event
9. LUCA — the last universal common ancestor
10. Mass-independent fractionation of sulfur isotopes
11. Banded iron formations
12. The origin of life
13. Stromatolites
14. The Cambrian explosion
15. Endosymbiosis and the eukaryotic cell
16. Mass-independent fractionation of sulfur isotopes
17. Banded iron formations
18. Evidence
19. 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.