A whiff of ancient oxygen supported by selenium isotopes

UWAB Postdoc Eva Stüeken, Professor Roger Buick, and collaborators showed in a new paper that there was a brief interval around 2.5 billion years ago when the flux of selenium into the ocean increased and isotopes were more fractionated. These data support previous indications that this period corresponds to a brief “whiff” of free oxygen, either globally or within microbial mats on land. Hence oxygen production must have started long before the great oxidation event at ~2.3-2.4 billion years ago, which in turn supports the idea that it takes a considerable amount of time to fully oxidize the surface of a planet, which has implications for the evolution of organisms that require oxygen to breathe.