A Continental Flood Basalt Driver for Neoproterozoic Oxygenation and Snowball Glaciation?
IPGP - Îlot Cuvier
A flurry of new radiometric ages confirms the synchronicity of the onset and demise of two global glaciations in the Neoproterozoic Era (1000–541 million years ago). These data strengthen support for the snowball Earth hypothesis, which posits that the entire Earth froze over for millions of years at a time, only to thaw abruptly in cataclysmic but transient super greenhouse events. These new geochronological data highlight how extraordinary the climatic perturbation must have been to trigger the ice albedo runaway that ushered in snowball glaciation. Here I will present geochemical evidence that supports the “Fire and Ice” hypotheses for the onset of the older (Sturtian) Cryogenian glaciation. New evidence suggests that the rapid weathering of unusually extensive continental flood basalts on a splintering, low-latitude supercontinent at the time was responsible for the initiation of snowball Earth through a combination of enhanced silicate weathering and a linked increase in primary production in the oceans due to elevated phosphorus fluxes. By the same reasoning, weathering of continental flood basalts likely played a direct role in driving the high marine carbon isotope ratios that characterize much of the Neoproterozoic and regulating oxygenation of the surface environment.