Identification of the Guadalupian–Lopingian boundary in the Permian in a bedded chert sequence, South China

Abstract

Middle–Upper Permian conodont biostratigraphy was examined in a bedded chert section in Dachongling area of southeastern Guangxi Zhuang Autonomous Region, South China. Four conodont zones were recognized, namely, Jinogondolella granti Zone, Clarkina postbitteri hongshuiensis Zone, Clarkina postbitteri postbitteri Zone, and Clarkina dukouensis Zone, in ascending order. The four conodont zones can be correlated with those recognized previously in bathyal carbonate and lime–chert sequences. On the basis of the correlation, we identified the Guadalupian–Lopingian (G–L) geochronostratigraphic boundary (i.e. the basal boundary of Lopingian Series) in the Permian. Six radiolarian zones were also recognized in the same section, namely, Pseudoalbaillella longtanensis Zone, Pseudoalbaillella globosa Zone, Follicucullus monacanthus Zone, Follicucullus scholasticus Zone, Follicucullus charveti Zone and Albaillella levis Zone, in ascending order. Correlations between radiolarian zones and conodont zones are shown here. The ecological evolutionary process of conodonts and radiolarians changed abruptly through the inferred G–L geochronostratigraphic boundary. Besides these, a geochemical anomalous zone with the higher Ce / Ce* values occurred underlying the G–L geochronostratigraphic boundary and petrological diagnoses around the G–L boundary changed. The abrupt change of ecological evolution in coincidence with the geochemical anomalous zone and change of petrological diagnoses might show the pre-Lopingian catastrophic event of marine faunas. The reason of the event of marine faunas may be that a regression occurred at the end of the Guadalupian.