Abstract
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 eNd(t) across this oxygenation
interval in the Gaoyuzhuang Formation of North China. The positive
δ202Hg, eNd(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.