Triple oxygen isotope constraints on atmospheric O and biological productivity during the mid-Proterozoic.

Reconstructing the history of biological productivity and atmospheric oxygen partial pressure (O) is a fundamental goal of geobiology. Recently, the mass-independent fractionation of oxygen isotopes (O-MIF) has been used as a tool for estimating O and productivity during the Proterozoic. O-MIF, reported as Δ'O, is produced during the formation of ozone and destroyed by isotopic exchange with water by biological and chemical processes.