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The Marinoan glaciation, considered one of the most severe episodes of global cooling in Earth's history, may have been more complex than previously thought, with periods of glacial advance and retreat that provided conditions for the survival of life in the Late Proterozoic.
The authors of the study, published in the journal Gondwana Research, analyzed sedimentary rocks from the Nantuo Formation in southern China, which formed about 650 million years ago. According to co-author Tina Lüdeke, “lithofacies analysis allows us to trace changes in the nature of sediments, reflecting the dynamics of glaciers under different conditions.” The six lithological facies found indicate that the glaciers pulsated, periodically retreating and returning.
Scientists have described three possible scenarios for the preservation of life during global glaciation. The “slushy Earth” hypothesis suggests the existence of significant thaw gaps in the tropical belt. The Jormungand hypothesis focuses on a narrow equatorial ice hole. The third scenario, “thin ice,” claims that the ice sheet transmitted light, ensuring life under the ice. New data confirm that even in shallow waters, glacier fluctuations occurred, which could have contributed to the preservation of Proterozoic microbes, including photosynthetic ones.
These results complicate our understanding of the "Snowball Earth," pointing to a dynamic climate with numerous cycles of cooling and warming. The discovery helps explain how life was able to adapt to such extreme conditions and continue to evolve, leading to the emergence of large multicellular organisms in the following Ediacaran period.
