Ediacaran negative C-isotopic excursions associated with phosphogenic events: Evidence from South China

Three major negative δ13C excursions, two in the Doushantuo Formation and one in the Dengying Formation, are tightly associated with phosphorite deposits. The temporal correlation between the negative δ13C excursions and the phosphorite deposits suggests a potential link between carbon and phosphorus cycling in the Ediacaran oceans. We argue that multiple periods of strong upwelling may have played an important role in C and P cycling in the Ediacaran oceans. Oxidative processes of the 13C-depleted dissolved organic carbon (DOC) transported into oxic near-surface waters by upwelling resulted in the negative δ13C excursions, and contributed to synchronous burial of abundant phosphorites in the inner shelf areas. The different magnitudes of the negative δ13C excursions observed in the Doushantuo and Dengying formations may reflect spatial changes of DOC reservoir and variations of upwelling intensity and mixing processes.