The environmental and biogeochemical information extracted from the sediments col- lected from the northern shelf of the South China Sea shows that terrigenous inputs of phosphorus into the sea remained relatively constant, and the variation of phosphorus contents at different depths was caused by climatic and environmental changes. The findings also suggest that the vertical varia- tion of phosphorus content was opposite to those of calcium carbonate and cadmium, and the func- tional correlation between CO2 and PO43? in seawater was given by calculating the chemical equilib- rium, indicating that the accumulation of marine sedimentary phosphorus may have something to do with the variation of atmospheric CO2. The decreased phosphorus accumulation as well as the cor- respondingly-increased calcium carbonate content might be one of key factors causing glacial at- mospheric CO2 decline. The environmental and biogeochemical information extracted from the sediments col- lected from the northern shelf of the South China Sea that that terrigenous inputs of phosphorus into the sea remained relatively constant, and the variation of phosphorus contents at different depths was caused by climatic and environmental changes The findings also suggest that the vertical varia- tion of phosphorus content was opposite to those of calcium carbonate and cadmium, and the func- tional correlation between CO2 and PO43? In seawater was given by calculating the chemical equilibri- rium, indicating that the accumulation of marine sedimentary phosphorus may something to do with the variation of atmospheric CO2. The decreased phosphorus accumulation as well as the cor- respondingly-increased calcium carbonate content might be one of key factors causing glacial at- mospheric CO2 decline.