Conodont biostratigraphy of a new Permo-Triassic boundary section at Wenbudangsang, north Tibet

Abstract

The Wenbudangsang section is a newly discovered continuous succession of marine carbonates that straddles the Permian–Triassic boundary (PTB), extending from the late Permian to the earliest Triassic (Induan). The section is located in the Wenbudangsang area of Geji County, northern Tibet, and tectonically sits within the northern Gangdise Stratigraphic division. Conodonts are abundant throughout this section, except being comparatively rare and less diverse in the Permian strata below the distinctive PTB Clay Bed.The conodonts are mainly represented by Hindeodus–Isarcicella Pa elements, Neogondolella Pa elements, and ramiform elements, with few Neospathodus Pa elements present at the top of the section. Two conodont zonal successions have thus been determined based on Hindeodus–Isarcicella and Neogondolella species. The Hindeodus–Isarcicella succession includes the uppermost Permian Hindeodus julfensis Zone, Hindeodus praeparvus Zone, and the lowermost Triassic Hindeodus parvus Zone, Isarcicella staeschei Zone, Isarcicella isarcica Zone, and Hindeodus postparvus Zone. The Neogondolella succession consists of the upper Permian Neogondolella changxingensis–Neogondolella deflecta–Neogondolella postwangi Zone, Neogondolella yini–Neogondolella zhangi Zone, Neogondolella meishanensis Zone, the Neogondolella taylorae Zone that crosses the PTB, and the lowermost Triassic Neogondolella krystyni Zone and Neogondolella prediscreta n. sp. Zone. The top of the section is defined by the Neospathodus kummeli Zone and Neospathodus cristagalli Zone. Two new species, Hindeodus microdentatus n. sp. and N. prediscreta n. sp., are established and described in this paper.The PTB conodont successions recognised in the new Wenbudangsang section have been closely correlated herein with other well-known PTB sections: the GSSP Meishan section of South China, sections in Abadeh in Iran, and sections at Spiti in India. Importantly, the conodont faunas from Wenbudangsang now provide an opportunity to effectively correlate the PTB hindeodid and gondolellid zonal schemes given the high abundance of both assemblages, which is unique to this section.