Snowball Earth in Space and Time

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At least twice during the Cryogenian Period (720-635 million years ago), ice covered the Earth for millions of years in Snowball Earth events. These are the most extreme episodes of climate change in the geological record, but the duration of glaciation and the rate of ice movement remain poorly constrained. The research team will use sediment core of glacial deposits in Antarctica, coupled with drone-based mapping and precise isotopic dating on Snowball Earth deposits in Namibia, to construct a rate-dependent stratigraphic model. They will also develop a research exchange between University of Namibia and UCSB to train students in the field in Namibia and in the lab in California. This training will occur during the course of geological field mapping and sample analysis that is essential context for their research goals of constraining the tempo and nature Snowball Earth, and will prepare students for careers in Geosciences, including critical minerals. The largest uncertainty in the timeline of Cryogenian glaciations is the onset age of the Marinoan glaciation, which is not only important for constraining the rate and nature of glacial processes, but also mechanisms for initiation and deglaciation. Previous studies have suggested that water-lain sediments deposited during Snowball Earth are incompatible with a weak hydrologic cycle. A proposed reconciliation is that during late stages of Snowball Earth with high CO2, ice-sheets could respond to orbital forcing leading to a more active hydrological cycle. However, because these studies have not been able to constrain rate, it is unclear if the apparent cyclicity in these stratigraphic sections is due to Quaternary-like orbital forcing or autogenic processes internal to the ice sheet that have little to do with external forcings. The researcher's preliminary U-Pb zircon geochronology and drone-based mapping data document multiple datable volcanic horizons that can be used to constrain the rate of grounding-line oscillation, and provide the first temporally quantitative facies model for Snowball Earth glacial deposits.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.