Triassic conodont biostratigraphy in the Coqên area, western Gangdise, Tibet, China

Carbonate sediments at the northern margin of the Dibu Co in Gyangrang Township, Coqen County, Tibet, were previously considered to be the Middle Permian Xiala Formation. However, this view was challenged by the latest conodont biostratigraphic study. Four Triassic conodont zones (or assemblage zones) are recognized in the carbonate sediments; they are: the Neogondolella carinata Zone, Neospathodus triangularis-Ns. homeri Assemblage Zone, Chiosella timorensis Zone and Paragondolella inclinata-Pg. polygnathiformis Assemblage Zone. Comparative study of the conodont faunas indicates that: the newly-established Garing Co Formation is Early Triassic Indian to Middle Triassic late Ladinian in age, and the sampled interval of the Zhuglung Formation is Middle Triassic latest Ladinian to Late Triassic early Carnian in age.