Previous study suggests that P concentration in Cryogenian seawater was higher than the modern level(Planavsky et al.,2010).To further test the P hypothesis,we measured P/Fe ratio of Fulu banded iron Formation from South China.Assuming seawater is saturated with respect to amorphous silica(2.20 mM),the estimated P concentration in South China is~2.26 μM,lower than the value of North America(~8.70 μM),suggesting heterogeneous P concentration in the Cryogenian seawater.The observed P gradient can be explained by the Cryogenian thermohaline circulation flowing from mid-latitude(South China)towards equatorial area(North America),as more organic matter was remineralized along the trajectory of ocean circulation.This interpretation also implies that primary productivity was high in midto low-latitude regions during the Sturtian glaciation,probably due to intense continental weathering after the breakup of Rodinia.Finally,our study also suggests that P concentration in seawater reflect a balance between organic matter production in surface ocean and remineralization in ocean interior.Therefore,the relationship between seawater P concentration,breakup of Rodinia,global glaciation,and postglacial oxygenation and evolution needs further evaluation.