Boulder, Colorado, USA - In the October issue of GSA Today, Grant Young of the University of Western Ontario discusses the possible causes of the numerous glaciations that characterized the Neoproterozoic and concludes that a dramatic shift in Earth's climate may have occurred during the Ediacaran, in part due to a large marine impact. According to Young, this shift separates Proterozoic glaciations, which were likely triggered by the effect of supercontinent assembly and breakup on atmospheric carbon dioxide levels.
Young notes that this suggests strong seasonality at low latitudes -- best accounted for by strong obliquity of the ecliptic from Phanerozoic glaciations, which developed at high latitudes and often follow episodes of mountain building. Young suggests that the climatic shift could have coincided with the great Shuram negative delta-carbon 13 excursion, which he interprets to be the record of a large marine impact. The impact is postulated to have decreased the obliquity, bringing about Earth's present climatic system and setting the stage for the emergence of complex life.
Evolution of Earth's climatic system: Evidence from ice ages, isotopes, and impacts
Grant M. Young, Dept. of Earth Sciences, University of Western Ontario, London, Ontario, Canada N6A 5B7; doi: 10.1130/GSATG183A.1.
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