Rise of atmospheric oxygen and the "upside-down" Archean mantle

The establishment of an oxygen-rich atmosphere dramatically altered the evo lution of life on Earth. Most of the recent discussion of the topic has bee n focused on the timing of the event rather than on its mechanism. Here we draw upon recent developments in the understanding of Earth's interior to p ropose that the rise of oxygen followed a geologically abrupt period of man tle overturn and/or intense plume activity near the Archean-Proterozoic tra nsition, 2470-2450 million years ago. The magmatic event has already been l inked to the widespread deposition of oxide-facies banded iron formation, a nd the rise of oxygen has been implicated as the trigger for iron depositio n and Earth's first major glaciation. We argue that these events are all re lated to a change in redox state of volcanic gases brought about by deep-se ated Late Archean and earliest Paleoproterozoic magmatism.