We measured both mass-dependent isotope fractionation of δ 88 Sr ( 88 Sr/ 86 Sr) and radiogenic isotopic variation of Sr ( 87 Sr/ 86 Sr) for the Neoproterozoic Doushantuo Formation that deposited as a cap carbonate immediately above the Marinoan-related Nantuo Tillite. The δ 88 Sr and 87 Sr/ 86 Sr compositions showed three remarkable characteristics: (1) high radiogenic 87 Sr/ 86 Sr values and gradual decrease in the 87 Sr/ 86 Sr ratios, (2) anomalously low δ 88 Sr values at the lower part cap carbonate, and (3) a clear correlation between 87 Sr/ 86 Sr and δ 88 Sr values. These isotopic signatures can be explained by assuming an extreme greenhouse condition after the Marinoan glaciation. Surface seawater, mixed with a large amount of freshwater from continental crusts with high 87 Sr/ 86 Sr and lighter δ 88 Sr ratios, was formed during the extreme global warming after the glacial event. High atmospheric CO 2 content caused sudden precipitation of cap carbonate from the surface seawater with high 87 Sr/ 86 Sr and lighter δ 88 Sr ratios. Subsequently, the mixing of the underlying seawater, with unradiogenic Sr isotope compositions and normal δ 88 Sr ratios, probably caused gradual decrease of the 87 Sr/ 86 Sr ratios of the seawater and deposition of carbonate with normal δ 88 Sr ratios. The combination of 87 Sr/ 86 Sr and δ 88 Sr isotope systematics gives us new insights on the surface evolution after the Snowball Earth.