Did a Snowball Earth event trigger the rise of atmospheric oxygen in 2.2 billion years ago?
Fig. 1: Distribution of the Marquette Range and Huronian Supergroups in North America. The yellow star represents the sampling locality of the Marquette Range Supergroup. The blue and red stars represent sampling localities of the Huronian Supergroup.
The rise of atmospheric oxygen at 2.2 billion years ago (“the Great Oxidation Event”) is of great interest because of its importance for the evolution of life. Given a global-scale severe glaciation (“the Paleoproterozoic Snowball Earth”) occurred immediately before the Great Oxidation Event, scientists have suspected that climate change played a key role in driving the rise of oxygen. The concrete mechanism connecting these events however remains a mystery. Here we report geochemical evidence suggesting a tremendous release of methane, a strong greenhouse gas, and concomitant global warming of climate in the aftermath of the Paleoproterozoic Snowball Earth event. The release of large amounts of methane in turn accelerated nutrient supply, which results in a massive blooming of cycnobacteria, contributing to the rise in atmospheric oxygen. This study provides an important evidence for the “missing link” between an extreme climatic perturbation and the atmospheric transition in Earth's history.
Sekine Y., E. Tajika, N. Ohkouchi, N.O. Ogawa, K. Goto, R. Tada, S. Yamamoto, J.L. Kirschvink “Anomalous negative excursion of carbon isotope in organic carbon after the last Paleoproterozoic glaciation in North America” Geochemistry, Geophysics, Geosystems, in press, 2010.