Stromatolites

Assembled from 11 blocks · 1 evidence · 10 related

1. Story
2. Layered sedimentary structures built when a microbial mat traps and binds sediment and precipitates carbonate, growing upward in millimetre laminae over years to centuries. They are the most abundant fossil evidence for the first three billion years of life, and almost all of it is a structure rather than an organism: the mat itself is rarely preserved, so the case for biogenicity usually rests on lamina geometry, on textures inconsistent with pure chemical precipitation, and on the absence of a plausible abiotic mechanism. That is a weaker kind of evidence than a body fossil and it is why several of the oldest claims remain contested. Living stromatolites still form in a small number of settings where grazing animals are excluded, most famously in the hypersaline waters of Hamelin Pool in Shark Bay, Western Australia. Their scarcity today is itself informative: stromatolites declined sharply through the later Proterozoic, and the most economical explanation is that animals learned to eat microbial mats.
3. Knowledge
4. Stromatolites
5. Connections
6. The origin of life
7. The Great Oxidation Event
8. Structures at Isua are reported as 3.7 Ga stromatolites
9. The Isua stromatolite claim is reassessed and rejected
10. Evidence
11. 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.