Silurian conodonts from the Nyalam region, southern Xizang (Tibet), China, and their biostratigraphical and palaeobiogeographical implications

Abstract

The Silurian conodont biozonation has been well established in many areas of the world, but not yet in China. The Nyalam region of southern Xizang (Tibet) is one of the best locations for studying Silurian conodonts in China. In this paper, we establish five conodont biozonal units from the Pulu Formation: the Ozarkodina sagitta sagitta Biozone, the Kockelella crassa Biozone, the Kockelella variabilis variabilis – Ancoradella ploeckensis Zonal Group, the Polygnathoides siluricus Biozone, and the “ Ozarkodina ” eosteinhornensis s.l. interval Biozone. We assign the Pulu Formation to the Llandovery (upper Telychian) to Pridoli stages based on the conodonts as well as the graptolites from underlying strata. The Silurian conodont species in the Nyalam region are widely distributed in the strata from the Laurussia and Gondwana, which indicates the cosmopolitan characteristic of the conodont fauna from the Wenlock to Pridoli epochs was caused by the circulation of ocean currents. • Five conodont biozonal units from Wenlock to Pridoli were identified in the Nyalam region. • Pulu Formation in the Nyalam region is Telychian to Pridoli in age. • Silurian conodont fauna in the Nyalam region have a cosmopolitan characteristic.