The great oxidation event (GOE), ~2.4 billion years ago, caused fundamental changes to the chemistry of Earth's surface environments. However, the effect of these changes on the biosphere is unknown, due to a worldwide lack of well-preserved fossils from this time. Here, we investigate exceptionally preserved, large spherical aggregate (SA) microfossils permineralised in chert from the c. 2.4 Ga Turee Creek Group in Western Australia. Field and petrographic observations, Raman spectroscopic mapping, and in situ carbon isotopic analyses uncover insights into the morphology, habitat, reproduction and metabolism of this unusual form, whose distinctive, SA morphology has no known counterpart in the fossil record. Comparative analysis with microfossils from before the GOE reveals the large SA microfossils represent a step-up in cellular organisation. Morphological comparison to extant micro-organisms indicates the SAs have more in common with coenobial algae than coccoidal bacteria, emphasising the complexity of this microfossil form. The remarkable preservation here provides a unique window into the biosphere, revealing an increase in the complexity of life coinciding with the GOE.

中文翻译：

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独特的微化石支持早期古元古代复杂细胞组织的兴起

约 24 亿年前的大氧化事件 (GOE) 引起了地球表面环境化学的根本变化。然而，由于全世界范围内缺乏保存完好的这一时期的化石，这些变化对生物圈的影响尚不清楚。在这里，我们研究了保存完好的大型球形聚集体 (SA) 微化石，这些微化石是来自约 100 世纪的燧石中。2.4 西澳大利亚州的 Ga Turee Creek 群。现场和岩相观察、拉曼光谱测绘和原位碳同位素分析揭示了对这种不寻常形式的形态、栖息地、繁殖和代谢的见解，其独特的 SA 形态在化石记录中没有已知的对应物。与 GOE 之前的微化石的比较分析表明，大型 SA 微化石代表了细胞组织的进步。与现存微生物的形态比较表明，SAs 与共生藻类比球状细菌有更多共同点，强调了这种微化石形式的复杂性。这里出色的保护提供了了解生物圈的独特窗口，揭示了与GOE同时发生的生命复杂性的增加。