Latest Guadalupian to Lopingian conodonts from western Hubei–eastern Chongqing, South China

Abstract. The Lopingian stratigraphic framework of the western Hubei–eastern Chongqing (WHEC) area, South China, remains insufficiently constrained, particularly regarding the precise age of the organic-rich intervals within the Dalong Formation that are considered to be favorable for shale gas exploration. To address this issue, a refined conodont biostratigraphic framework is established based on systematic sampling of the Longmenba, Huangping, and Tongmuyuan sections. A total of 17 conodont species belonging to four genera (Jinogondolella, Clarkina, Hindeodus, and Iranognathus) are identified, allowing recognition of a near-continuous succession spanning the late Wuchiapingian to the Changhsingian. Integration of biostratigraphic and lithostratigraphic data allows placement of the Wuchiapingian–Changhsingian boundary within the upper part of the Dalong Formation, with minor local variations attributable to facies differences and preservation potential. Importantly, the organic-rich, siliceous-shale interval in the lower Dalong Formation is shown to be temporally restricted to the late Wuchiapingian, mainly corresponding to the upper Clarkina guangyuanensis Zone and extending into the C. orientalis or lowermost C. longicuspidata Zone. The temporal overlap between late Wuchiapingian conodont zones, regional basin deepening, and waning eruptive phases of the Emeishan Large Igneous Province suggests broader tectono-environmental controls on sedimentary and biotic evolution. This study highlights the value of high-resolution conodont biostratigraphy in resolving Lopingian depositional history and in linking micropaleontological records with regional paleoenvironmental change.