Enhanced weathering triggered the transient oxygenation event at ~1.57 Ga

The mid-Proterozoic (~1.8–0.8 Ga) is characterized by low atmospheric oxygen and pervasive oceanic anoxia, with transient oxygenations. One of the prominent oxygenation events happened at ~1.57 Ga, during which atmospheric O2 may have reached ≥4% present atmospheric level (PAL) and thus promoted the evolution of multi-cellular eukaryotes. The causes for this oxygenation event, however, remained unknown. Here, we report the result of δ202Hg and ∆199Hg, P concentration, Rb/Al, and Nd(t) across this oxygenation interval in the Gaoyuzhuang Formation of North China. The positive δ202Hg, Nd(t), and negative Δ199Hg shifts, and the accompanied peaks in Rb/Al, P and I/(Ca+Mg) suggest that this oxygenation 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 can trigger transient oxygenation events during the mid-Proterozoic.