Wed 22nd April, 12 – 1 pm, Rm 312.222

Abstract

A flurry of new radiometric ages confirms the synchronicity in 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. A combination of Nd isotopes on mudstones and Sr isotopes on marine carbonates through the Neoproterozoic imply that the weathering of extensive continental flood basalts, which covered large parts of Rodinia, was responsible for the initiation of snowball Earth through a enhanced silicate weathering and primary production in the oceans. 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.

Biography

Galen Halverson is the T.H. Chair in sedimentary geology and petroleum geology at McGill University in Montreal, Canada. Galen is a sedimentary geologist and geochemist whose interests lie in reconstructing and deciphering the stratigraphic record. His research involves a combination of fieldwork, basin analysis, and analytical geochemistry. The ultimate aim of this research is to document, calibrate, and interpret Earth system evolution spanning the great transition from a world that supported only relatively simple, mostly unicellular life to a habitable world that fostered the origin and rapid diversification of animal life. Galen began to study geology as an undergraduate student at the University of Montana and subsequently honed his passion for Proterozoic geology as a PhD student with Paul Hoffman at Harvard University, where he was involved in the early articulation of the snowball Earth hypothesis. He later lived and worked in Namibia, France, and Australia prior to relocating to Montreal in 2010. He is currently a Gledden Fellow at the University of Western Australia working to date mafic igneous events in North America and Australia related to the break-up of the supercontinent Rodinia.