摘要
The Ordovician Yingshan Formation in the Tarim Basin has been interpreted as Early Ordovician, Early-Middle Ordovician, or Middle Ordovician deposits. Based on the geological range of the conodont Serratognathoides chuxianensis and the Lower/Middle Ordovician boundary stratotype, the Yingshan Formation is regarded as Early Lower Ordovician in age (Tremadocian-Floian). There is stratigraphic break between the Yingshan Formation and the overlying strata based on paleontological and biostratigraphical data.