Detrital zircon U-Pb dating of Suining Formation sandstone from the Daba Mountains, northeastern Sichuan and its stratigraphic implications

The non-marine Jurassic-Cretaceous boundary in the Sichuan Basin in southwestern China has a long and highly controversial history. According to the dominant opinion, the Suining and Penglaizhen Formations are the Upper Jurassic, and the Chengqiangyan Group is the Lower Cretaceous. Based on detrital zircon U-Pb dating of the Suining Formation sandstone from the Daba Mountains, the upper limit of the deposition of the Suining Formation is given by the detrital zircon U-Pb ages. The youngest detrital zircon U-Pb age is ∼120 Ma, which reflects a depositional age of younger than ∼120 Ma. The detrital zircon U-Pb age of the Suining Formation shows that this widespread formation should be assigned to the Cretaceous, not the Jurassic. This study sheds new light on the location of the Suining Formation in the stratigraphic column. Additionally, these ages are very important for the regional stratigraphic correlation and tectonic evolution studies.