Abstract:Phosphorus is one of the key nutrient elements, which are closely associated with sedimentary environment and evolution of life. Widespread deposits of phosphorites are coeval with skeletonized animals during the Ediacaran- Cambrian transition in South China and elsewhere globally, suggesting a link between phosphorus in sedimentary environment and evolution of life. However, sedimentary environment and formation mechanism of phosphorites remains elusive. In order to explore these challenges, we investigated aggregation form of phosphate, pyrite morphology, and the composition of rare earth elements (REE) of phosphorites in the early Cambrian Meishucun profile, South China. Our results show that phosphorites are mainly composed of crystalline calcium fluorophosphates, cryptocrystalline calcium fluorophosphates, and iron oxides. The distribution of REE belongs to “hat type” mode, similar to that in the pore- water ferruginous- manganous zone, suggesting that REE is significantly affected by early diagenesis. The absence of framboid pyrite and relatively low Ce/Ce* (0. 50~0. 82, average 0. 70), suggest that phosphorites were deposited under oxic/dysoxic conditions. The absence of Eu abnormality (0. 92~1. 08, average 0. 98), indicates that phosphorites were not influenced by hydrothermal activity. High Y/Ho ratios of 55. 3~74. 5 (average 63. 6) similar to those of seawater reflects that phosphate originated from seawater. In combination with widespread oceanic oxygenation, anoxic stratified ocean structure, and intensive upwelling, we infer that phosphorites resulted from high oceanic phosphate concentrations associated with oceanic oxygenation event and the large fluxes of enriched phosphate contents in reducing deep waters to oxic/dysoxic surface waters by intensive upwelling.