Biogeochemists have found new evidence linking "Snowball Earth" glacial events to the rise of early animals. The research was funded by the National Science Foundation (NSF).
Study results appear in this week's issue of the journal Nature.
The controversial Snowball Earth hypothesis posits that, on several occasions, the Earth was covered from pole to pole by a thick sheet of ice lasting for millions of years.
These glaciations, the most severe in Earth history, occurred from 750 to 580 million years ago.
In the aftermath, the researchers discovered, the oceans were rich in phosphorus, a nutrient that controls the abundance of life in the oceans.
The team, led by scientists at the University of California Riverside, tracked phosphorus concentrations through Earth's history by analyzing the composition of iron-rich chemical precipitates. These precipitates accumulated on the seafloor and "scavenged" phosphorus from seawater.
The analyses revealed that there was a pronounced spike in marine phosphorus levels in the mid-Neoproterozoic (from ~750 to ~635 million years ago).
To explain these anomalously high concentrations, the researchers argue that the increase in erosion and chemical weathering on land that accompanied Snowball Earth glacial events led to the high amounts of phosphorus in the ocean.
The abundance of this nutrient, which is essential for life, in turn led to a spike in oxygen production via photosynthesis, according to Enriqueta Barrera, program director in the NSF's Division of Earth Sciences, which funded the research.
The subsequent accumulation of oxygen in the atmosphere led to the emergence of complex life on Earth.
"In the geologic record, we found a signature for high marine phosphorus concentrations appearing in the immediate aftermath of Snowball Earth glacial events," said Noah Planavsky, the first author of the research paper, and a grad
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National Science Foundation