Late Mesozoic sedimentary-volcanic filling record in Yungang basin and its tectonic implications

Based on regional stratigraphic correlation and using zircon dating method of tuff layer and andesite rocks in the Late Mesozoic stratigraphic sequence, the authors defined the key time of the sedimentary-fill record. According to the formation contact relationship and the geochemical characteristics of the andesite, the authors also analyzed the tectonic significance of the key geological interface. Some conclusions have been reached:(1) During the Early-Middle Jurassic, the sedimentary sequence was characterized by a suite of lake transgression sequence with the coal-bearing strata of Datong Formation, indicating the tectonic setting of the regional extension; (2) These strata had no sedimentary record from Late Jurassic (160.4±1.1 Ma) to Early Cretaceous (130.1±0.7 Ma), which was dynamically associated with far field effects produced by synchronous convergences toward the east Asia continent of different plates (Siberia, Paleo-Pacific, Tethys); (3) The andesite of Jiugaoshan was developed in the tectonic setting of the continental rift during the Early Cretaceous, which might have been associated with the destruction of the North China Craton. The andesite age of Jiugaoshan was defined in the study. It does not belong to the Tiaojiashan Formation, but corresponds to the Zhangjiakou Formation in Yanshan area.