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北京十三陵地区雾迷山组 ( 1310～ 12 0 7Ma)白云岩的δ13 C数值范围从 - 1.5‰～ 1.5‰(PDB) ,δ18O数值范围一般为 - 4‰～ - 5‰ (PDB) .它们碳同位素组成具有旋回性变化的特征 .δ13 C从地层层序的边界发生正偏移 ,至 1.5‰ (PDB) ,然后发生负偏移至 - 1.5‰ (PDB) .有时 ,在δ13 C为负值的层段δ18O数值较高 ,约为 - 4 .0‰ (PDB) .碳、氧同位素组成的这种特征可能与海平面变化相关
The δ13C values of the dolomites in the Wumishan Formation (1310 ~ 1270 Ma) in the Shisanling area of Beijing range from - 1.5 ‰ to 1.5 ‰ (PDB), and the δ18O values range from -4 ‰ to -5 ‰ (PDB). Their carbon isotopic compositions are cyclically altered δ13 C is positively offset from the boundary of the stratigraphic sequence to 1.5 ‰ (PDB) and then negatively shifts to -1.5 ‰ (PDB). Sometimes δ13 C is The negative δ18O value is high, about -4.0 ‰ (PDB), and this feature of carbon and oxygen isotopic composition may correlate with sea level changes