Early to Late Triassic conodont biostratigraphy in the Lhasa Terrane

Abstract

The Coqen area of the Lhasa Terrane, Xizang (Tibet, Southwest China) has provided key evidence for understanding Triassic history in the region. However, the stratigraphic subdivision of the Middle to Upper Triassic remains unclear. Here we present new results on the conodont biostratigraphy at Dibuco, a section in the Lhasa Terrane. Sixteen genera and forty-three species are identified, including one new species: Borinella dibucoensis sp. nov. of the Spathian (Olenekian) age. Eight conodont zones are established from the Late Olenekian to the Early Norian. These are, in ascending order, Triassospathodus homeri - Columbitella jubata Zone, Neogondolella constricta Zone, Paragondolella praeszabόi Zone, Budurovignathus mungoensis Zone, Quadralella polygnathiformis Zone, Quadralella praelindae Zone, Carnepigondolella oertlii - Carnepigondolella nodosa Zone and Ancyrogondolella aff. quadrata Zone. This is a relatively complete conodont succession for eastern part of Tethys region and it shows close relationship with western Tethys and eastern Tethys (South China). Based on the conodont biostratigraphy, the base of Zhulong Formation, previously lacking a precise age assignment, is shown to be of late Anisian age.