Some of the investigated sections in the Tarim and Ordos regions in Northwest China represent a mixed biofacies and yield diverse faunas of both graptolites and conodonts. The unusual co-occurrence of biostratigraphically important representatives of these major index fossil groups allows for the recognition of many new ties between standard graptolite and conodont biozones. Hence, the study areas are of world-wide significance for constructing more precise correlations between Darriwilian and Sandbian conodont and graptolite biozones. Comparison with Baltoscandic, North American, and Argentine key sections confirms the biozonal relations shown in the Northwest China study sections.