| The redox conditions of the oceans evolved considerably during the Precambrian. This is mainly due to the arrival of the oxygen, at first generating oxygen oases, and then accumulating in the atmosphere during the Great Oxidation Event (GOE) ca. 2.45 Ga. However, the earliest traces of free oxygen during these periods, and the mechanisms of their sedimentary expression, remain poorly understood. For over a decade, the isotopic composition of molybdenum (δ98Mo) in sediments has been used as a global marine redox proxy.An elemental and isotopic study of the different phases constituting carbonate rocks was carried out using sequential digestions performed on carbonates of different ages and depositional environments. The results show that Mo is primarily... |
