Elevated Phosphorus Concentrations in Shallow Oceans as a Trigger for the 1.57‐Ga Oxygenation Event
Baozeng Xie, Zihu Zhang, Chao Li, Matthew S. Dodd, Xiaoying Shi, Qing Shi, Chao Li, Longfei Sun, Lei Xu, Xinqiang Wang, Dongjie Tang
Abstract
Abstract Enhanced continental phosphorus (P) input into the oceans has been proposed as a potential trigger for the 1.57 Ga oxygenation event; however, uncertainty remains due to the absence of direct evidence for seawater P concentrations. Here, we investigate shallow marine carbonate rocks of the Gaoyuzhuang Formation in the North China Platform, using the carbonate‐associated phosphate (CAP) proxy to directly reconstruct seawater P levels at that time. Two significant CAP/(Ca + Mg) increases correspond with rises in I/(Ca + Mg) during the oxygenation event suggesting that elevated seawater P concentrations were important in triggering the oxygenation event. Furthermore, a concurrent positive shift in ε Nd (t) values from −12.3 to −0.9 suggests that a transition in weathering source rocks from intermediate to mafic lithologies significantly contributed to the elevated P fluxes to the oceans during the oxygenation event. This study provides new insights into assessing seawater P levels and their role in the mid‐Proterozoic oxygenation events.