Press Releases
Jul. 26, 2010

Did a Snowball Earth event trigger the rise of atmospheric oxygen in 2.2 billion years ago?

Presenters
  • Yasuhito Sekine (Dept. Complexity Sci. & Engr., Univ. Tokyo)
  • Eiichi Tajika (Dept. Earth Planet. Sci., Univ. Tokyo)
  • Ryuji Tada (Dept. Earth Planet. Sci., Univ. Tokyo)
  • Naohiko Ohkouchi (Inst. Biogeochem., JAMSTEC)

Abstract

Figure 1

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.

Paper information

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.

Figure 2

Fig. 2: Schematic diagram of carbon isotopic variations in organic carbon in the aftermath of the Paleoproterozoic Snowball Earth. Large-scale dissociation of methane hydrate occurred during the waning, resulting in a marked acceleration in global warming. The extreme greenhouse conditions that developed following the dissociation of methane hydrate may have caused strong chemical weathering and supplied large amounts of phosphorus to the oceans, thereby accelerating the Great Oxidation Event.

Figure 3

Fig. 3: Left; A picture of sampling at the Marquette Range Supergroup. Right; A dropstone in the Gowganda Formation in the Huronian Supergroup.