Evidence that the GOE was a prolonged event with a peak around 1900 Ma

The great oxygenation event (GOE), the first of two major rises in atmospheric oxygen in Earth history, was initially placed near the Archean-Proterozoic boundary (∼2500 Ma).  More recently, the position of the GOE has been moved to between 2500 and 2300 Ma so as to coincide with the loss of the MIF sulfur isotope signal due to the creation of the Earth's ozone layer at that time. Here we present a revised interpretation of the history of atmospheric oxygen in the Archean and Proterozoic, based on a multi-geochemical proxy approach. Integration of a large database of analyses of redox sensitive elements in sedimentary pyrite (Se, Co, Mo), the matrix of black shales (U, Mo), and the temporal evolution of redox sensitive minerals, suggest Earth's first oxygenation was prolonged, reaching a peak between 2000 and 1700 Ma. Rather than a relatively short-lived event from 2500 to 2300 Ma, we suggest an alternative profile for Earth's atmospheric O2, i.e., an unsteady start to the rise in oxygen around 2700 Ma that undulated for approximately a billion years, reaching a peak around 1900 Ma before a plunge in the Proterozoic Eon after 1700 Ma.