Enhanced Weathering Triggered the Transient Oxygenation Event at similar to 1.57 Ga

The mid-Proterozoic (similar to 1.8-0.8 Ga) is characterized by low atmospheric oxygen and pervasive oceanic anoxia, with transient oxygenation events. One of the oxygenation events happened at similar to 1.57 Ga, during which atmospheric O-2 may have reached >= 4% present atmospheric level (PAL) and thus promoted the evolution of multi-cellular eukaryotes. The cause of this oxygenation event, however, remained unknown. Here, we report delta Hg-202, increment Hg-199, P concentration, Rb/Al, and epsilon(Nd)(t) data across the similar to 1.57 Ga oxygenation event in the Gaoyuzhuang Formation of North China. The positive delta Hg-202, epsilon(Nd)(t), and negative Delta Hg-199 shifts, plus the accompanied peaks in Rb/Al, P, and I/(Ca + Mg), suggest that this oxygenation event was likely resulted from enhanced weathering of intermediate to mafic rocks, which may have promoted primary production via increasing P influx to the ocean and led to the rise in oxygen levels. The data indicate that enhanced weathering input could trigger transient oxygenation events during the mid-Proterozoic.