Roadian-Wordian (Middle Permian) Conodont Biostratigraphy, Sedimentary Facies and Paleotemperature Evolution at the Shuixiakou Section, Xikou Area, Southeastern Qinling Region, China

Focusing on the Shuixiakou Section (Xikou area, Zhen’an County, Shaanxi Province, southeastern Qinling region, China), the Roadian-Wordian conodonts are investigated. More than 2 000 conodont elements including 6 genera and 14 species have been obtained. Based on these materials, the Guadalupian Jinogondolella nankingensis and J. aserrata zones have been recognized. The Roadian-Wordian boundary is tentatively defined by the first occurrence of J. aserrata in the lower part of Unit III in the Shuixiakou Formation. The sedimentary succession of Xikou area records similar sea-level changes to those observed in Laibin area (South China). The 40 m-thick bioclastic limestone of Unit IV in this section can be correlated with the reefs of Bed 114 in Laibin area. A temperature drop indicated by δ 18 O apatite values suggests this Wordian interval coincides with a period of glaciation and global regression.