Lower-Middle Triassic conodont biostratigraphy of the Mingtang section, Nanpanjiang Basin, South China

Abstract

The well-exposed stratigraphic sequences on the Great Bank of Guizhou (GBG) in South China provide important information for the understanding of various environmental settings during the Permian-Triassic mass extinction and the subsequent recovery, including one of the oldest Triassic marginal reef complexes, which is viewed as an important indicator of biotic recovery following the end-Permian mass extinction. Here we report a systematic conodont study on a newly exposed Lower-Middle Triassic section, the Mingtang section, at the margin of the GBG to provide more data for the time scale of the post-extinction recovery. Twenty-four species in 11 conodont genera are identified and assigned to Hindeodus parvus, Neoclarkina discreta, Neospathodus dieneri, Novispathodus waageni, Neospathodus triangularis-Triassospathodus homeri, Chiosella timorensis, Nicoraella germanica, and Nicoraella kockeli zones in ascending order. These zones correlate well with the conodont successions in South China and over the world. The Induan-Olenekian boundary can be well defined by the first occurrence of Novispathodus waageni in the lower-middle part of the Luolou Formation, while the Early-Middle Triassic boundary was placed at 0.2m below the top of the Luolou Formation according to the first occurrence of Chiosella timorensis. These conodont data suggest that the Tubiphytes-reef began to recover in the Bithynian (early Middle Triassic), later than benthonic organisms such as foraminifers and calcareous algae.