Abstract:  Sensitive High Resolution Ion Microprobe (SHRIMP) U-Pb dating was carried out using zircons from tuffs in the Ermaying and Tongchuan formations of Shanxi, China. The results show weighted mean ages of 245.9±3.2 Ma for a sample from Member II of the Ermaying Formation, 243.1±3.9 Ma for a sample from Member I of the Tongchuan Formation, and 238.6±2.6 Ma and 234.6±6.5 Ma for two samples from the upper part of Member II of the Tongchuan Formation. These ages indicate that the lower part of the Ermaying Formation, which contains the Shaanbeikannemeyeriaassemblage, is mostly likely Lower Triassic in age, whereas, the Tongchuan Formation is likely late Anisian to Ladinian, Middle Triassic.

摘要： 采集了山西省二马营组和铜川组共4个层位的火山凝灰岩，在高灵敏度高分辨率二次离子质谱仪上以铀-铅法测定其中锆石的年龄。二马营组上部的样品测年结果为245.9 Ma ± 3.2 Ma, 铜川组一段样品测年结果为243.1 Ma ± 3.9 Ma, 二段上部两个样品年龄为238.6 Ma ±2.6 Ma和234.6 Ma ± 6.5 Ma。结果表明出产陕北肯氏兽动物群的二马营组下部极有可能属于下三叠统，而铜川组时代可能从安尼期晚期到拉丁期。