Program > By author > Sun Yucong

Late Devonian to Early Carboniferous strata are well preserved in Tibet Plateau, China, but the fossils were poorly studied. Previous research on conodonts and spores from the Yali and Chaguoluoma sections enabled to approximately locate the Devonian-Carboniferous boundary in Xainza and Nylam regions. At Yali, three spore assemblages, including Retispora lepidophyta–Verrucosisporites nitidus (LN), Vallatisporites verrucosus–Auroraspora incohatus (VI) and Cingulizonates bialatus–Auroraspora macra (BM), and conodonts from the Protognathodus kockeli to Gnathodus pseudosemiglaber zones were reported, and the Devonian-Carboniferous boundary was placed at the base of the Goulongri Member of the Yali Formation. At Chaguoluoma, the occurrence of the conodont Protognathodus fauna was used to locate the DCB, but no photos of any specimen were provided. 

Our recent studies focus in the ostracod faunas from these two sections; 24 and 53 species were recognized at Yali and Chaguoluoma sections, respectively. Ostracods from the Yali section include Bairdiocypris elliptica, Acratinella valida and Bairdiacypris wuxuanensisetc. The Bairdia magna and Paraparchites longmenshanensis, which were firstly reported in Tournaisian, are found in the Goulongri Member of Yali formation. However, our new conodont collections recover both Pr. kockeli and Siphonodella sulcata below the Goulongri Member, lowering the DCB to the upper part of the Yalidonggou Member. Ostracods from the Chaguoluoma section include Acratinella valid, Bairdia cestriensis and Microcheilinella cordata, typically Late Devonian to early Carboniferous in age. Two early Carboniferous representative species, i.e. Necrateria rectagona and Microcheilinella bushminae, were firstly found 10.5 m above the base in the Chaguoluoma section. Moreover, major changes of ostracods abundance occur within the basal 8-10 m of the Chaguoluoma formation, more than 50 species are recorded within the lower 2-7 m while less than 5 species are found in the basal 8-10m. This change may be related to the Hangenberg extinction event in Tibet. In conclusion, the ostracod faunas have great potential to precisely locate the Devonian-Carboniferous boundary in theTibet Plateau.