A geochemical test of the Cryogenian Snowball Earth hypothesis
The Snowball Earth hypothesis predicts that the hydrological cycle was curtailed for millions of years, with ice-cover and low temperatures limiting silicate weathering of the continental crust. In this scenario, the deep ocean should have equilibrated with the mantle through hydrothermal exchange at mid-ocean ridges. Here we report the discovery of mantle-like Sr isotope values in marine carbonate and barite that rest directly above ca. 717-661 Ma Sturtian glacial deposits in Oman. These new data and geochemical modeling support an extreme Snowball Earth scenario with near complete ice-cover and reduced continental weathering for 56 Myr. The duration and extent of the Sturtian glaciation created a major bottleneck for the evolution of eukaryotes, clearing the way for the rise of algae and origin of animals.
Speaker: Francis Macdonald, Stanford University
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Tuesday, 11/19/24
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