Several rift basins developed in the western part of Xing’an-Mongol orogenic belt during late Paleozoic, in which volcanic-sedimentary series is important to understand the late Paleozoic tectonic evolution, however, there is not a clear space-time distribution of the series. Stratigraphy and geochronology of Xilimiao Formation have been researched to understand the basin filling process and tectonic setting. According to the field sections, Xilimiao Formation can be divided into three segments. Upper and lower segments are composed of crystal tuffs and rhyolitic lithic crystal tuffs, and middle segment are dark sedimentary rocks. The zircon ²⁰⁶Pb/²³⁸U age of 282±2 Ma achieved from the rhyolitic tuff of upper segment represents the forming age. The two peak ages of 304 Ma and 450 Ma represent the upper limit of the sedimentary event, the forming age of early Paleozoic orogenic belt, respectively, and the 870 Ma represents the age of Neoproterozoic basement. The data of middle detrital rocks indicate that the forming age of Xilimiao Formation was between 304?282 Ma, older than Zhesi Formation. Provenance of the detrital zircon from the middle Xilimiao Formation provides sedimentary evidence for transform process from compress of the middle Paleozoic orogenic belt to extension of the late Paleozoic rift basin.

U-Pb dating of detrital zircons from the pebbly siltstone at the top of the Tereeken Formation yielded the youngest zircon ages of 629±8 Ma, representing the maximum depositional age of the Tereekan glaciation. This result indicates that the Tereeken glaciation might be correlated with the Nantuo glaciation in the Yangtze Platform and the global Elatina or Marinoan glaciation. The remaining older zircons fall into three age-groups: 718-887 Ma, 1822-2092 Ma and 2345-2613 Ma, indicating three main Precambrian magmatic events in the Quruqtagh area.