The oldest fossils
Layered microbial mats — and they are still with us
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The stromatolites of the Dresser Formation in the Pilbara are among the oldest widely accepted traces of life. Distinguishing biological structures from purely chemical precipitates in rock this old is difficult, and some earlier claims have been withdrawn — hence the weight placed on the combination of morphology, carbon isotopes and microfossils. Living stromatolites at Shark Bay and in the Bahamas provide a direct analogue. For two billion years, mats like these were the most complex ecosystem on the planet.
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In the Pilbara region of Australia lie rocks with thin, wavy layers, like a stack of pancakes. The layers were built by bacteria trapping sand and silt above themselves, day after day, 3.5 billion years ago. The remarkable thing is that such mats still grow in Shark Bay, a few hundred kilometres away.
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Part of Terra Saga — the story of Earth on a timeline. terrasaga.org