Habitable marine environments for the first forms of complex life could have been more extensive than previously thought during the Marinoan glaciation, between 654 and 635 million years ago, according to a paper published in the journal Nature Communications.
The findings suggest that habitable conditions in the open ocean may have persisted even at mid-latitudes during “Snowball Earth”, when Earth’s continents and part of the oceans would have been covered in a thick layer of ice.
According to the researchers, this freezing time would have been more like a “Hailball Earth”, so that some organisms managed to survive in certain places.
Some complex organisms may have lived in ocean shelters during the global ice age
How complex life was able to survive during the Marinoan Snowball Earth glaciation has been a hotly debated topic. It is believed that there were ocean refuges that allowed marine organisms to survive during this event. However, the environmental conditions that allowed this survival are still not well known.
The team led by Huyue Song, from the University of Geosciences in Wuhan (China), analyzed the geochemical composition of fossil-rich sediments from the Nantuo Formation, in southern China, dated from 654 to 635 million years ago, at the end of the cryogenic era. . period. Scientists have found fossils similar to photosynthetic algae that lived at the bottom of the sea.
The investigation found possible fossils of algae that would have survived in the Nantuo Formation in China.
Furthermore, the presence of iron indicated to them that the deep water was poorly oxygenated, but the aerobic process of nitrogen was probably taking place in the oxygenated water at the surface. During the last glaciation of Snowball Earth, these sediments were deposited 30 to 40 degrees north, much farther north than would be expected in a thawed ocean.
The authors suggest that these mid-latitude oceanic deposits served as havens for complex organisms that survived periods of near-global freezing, allowing life to persist until conditions became more favorable.
Reference:
Song H. et al. “Mid-latitude habitable environment for marine eukaryotes during the decline stage of the Marinoan snowball glaciation”. Nature Communications (2023)
