The oryctocephalid trilobite zonation across the Cambrian Series 2-Series 3 boundary at Balang, South China: a reappraisal

A systematic revision of the oryctocephalid trilobites provides additional data for the definition of a revised zonation of the Cambrian Series 2-Series 3 boundary at Balang in South China. The zonation offers a new understanding of the biostratigraphical correlation of this debated limit. The biostratigraphical revision was carried out in the Wuliu-Zengjiayan Section and provides the following trilobite zones: (1) Protoryctocephalus arcticus; (2) Bathynotus kueichouensis—Ovatoryctocara sinensis Zone (upper part of Cambrian Series 2); and (3) Oryctocephalus indicus Zone (base of Cambrian Series 3). This suggests that this section is a suitable candidate GSSP for the base of Cambrian Series 3, Stage 5. The correlation in the Wuliu-Zengjiayan Section suggests that the P. arcticus Zone and the B. kueichouensis—O. sinensis Zone can be correlated with the Ovatoryctocara granulata Zone, while the O. indicus Zone is time-equivalent to the Oryctocephalus reticulatus Zone in Siberia. The P. arcticus Zone and the B. kueichouensis—O. sinensis Zone can be correlated with the Eoagnostus roddyi—Arthricocephalus chauveaui Zone and the Bonnia—Pagetides elegans Zone in North Greenland, as well as with the upper part of the Olenellus Zone, Nephrolenellus multinodus Zone in North America.