Stable carbon and oxygen isotopic compositions of carbonates in middle Mesoproterozoic Wumishan Formation and sea-level change

δ¹³ C of dolostones from the Wumishan Formation (1 310–1 207 Ma) in the Ming Tombs area near Beijing ranges from ?1.5 to 1.5‰ (PDB), and generally, the δ¹⁸O ranges from ?4 to ?5‰ (PDB). The secular variation of stable carbon isotopic compositions is cyclic. δ¹³C displays positive shifts from a sequence boundary to 1.5 per mil (PDB), then a negative shifts to ?1.5 per mil (PDB). In some unit, where δ¹³C values of the rocks are negative, they have relatively high δ¹⁸O values close to ?4.0‰ (PDB). These characteristics of the carbon and oxygen isotopic compositions may be associated with sea-level changes.