Objectives：The Beishan Region is located in the southernmost part of the Central Asian Orogenic Belt where the Upper Paleozoic sedimentary sequence plays an important role in the tectonic and sedimentary evolution. However, the age range and distribution of the Ganquan Formation remain uncertain.Methods：Based on sections in the Dushan and Liuyuan areas, southern Beishan region, this study reports LAICPMS zircon UPb ages from the Ganquan Formation and "undifferentiated Carboniferous".Results：The UPb ages of the Ganquan Formation and "undifferentiated Carboniferous" are 293.8 ± 4.8 Ma, 293.9 ± 2.7 Ma, 291.7 ± 2.3 Ma, which indicate the Kasimovian—Sakmarian range to the widely distributed Ganquan Formation with paleontological data. The lag deposits of the Shuangbutang Formation aged 293.4 ± 2.0 Ma and 294.4 ± 2.8 Ma suggest an unconformity between the Ganquan and Shuangbutang formations with a six million years sedimentary gap.Conclusions：The Visean—Capitanian strata in the Beishan Region form a generally continuous sequence, which represents the tectonic translation from several small extensional basins into a large rift basin. The Baishan Formation, Shibanshan Formation and the lower part of the Ganquan Formation are considered as the marginal and shallow marine deposits in the separated small basins. The upper part of the Ganquan Formation represents the early synrift phase (ca. 294 ~ 292 Ma) marked by intensive volcanism, whereas the Shuangbutang and Jushitan formations make up a transgression succession the late synrift phase (ca. 286 ~ 265 Ma).