On the onset of Cryogenian snowball glaciation

Cryogenian projectThe base of the first Cryogenian glaciation marks one of the most profound climate change events in Earth's history—matched only by the contacts markign the end of the Cryogenian snowball glaciations. The Cryogenian Subcommission on Precambrian Stratigraphy is actively working to formalize definition of the base of the Cryogenian period, which has served to focus attention on geological record of the transition from the Tonian period below with the Cryogenian glacial deposits above. While the way in which this boundary will be defined remains unresolved, what is clear is that in many places, this contact is a major unconformity. For example, in Svalbard, it appears that as much as 20 million years of time is missing on this contact. Other places, such as Scotland and northern Namibia, may have more complete records. One major goal in my research is to document these transitions and piece together and calibrate the most complete sedimentary and chemostratigraphic records possible leading into the first Cryogenian glaciation. These records can then be used test models for what perturbation to the climate system triggered the ice albedo runaway that ushered in the first snowball glaciation. For example, were extensive, low-latitude flood basalt provinces the culprit due their effect on drawing down CO2 via silicate weathering and enhanced primary productivity from addition of nutrients to the oceans (Goddéris et al., 2003; Cox et al., 2016)? Perhaps sulfate aerosols released during volcanism related to the massive Franklin LIP were the culprit (Wordsworth and Macdonald, 2017). Or maybe methane played a non-intuitive role (Schrag et al., 2003; Halveron et al, 2003). The jury is still out, but what is clear that better time-resolved records leading into the onset of Cryogenian record are essential if we are to understand this dramatic failure in Earth's climatic thermostat.

This project is supported by the Natural Sciences and Engineering Research Council (NSERC) of Canada