Conodonts from the Global Stratotype section for the base of the Guzhangian Stage (Cambrian) at Luoyixi, Hunan, South China

Abstract

The base of the Guzhangian Stage (Cambrian) has been ratified recently at the lowest occurrence of the cosmopolitan agnostoid trilobite Lejopyge laevigata (base of the Lejopyge laevigata Zone) in the Huaqiao Formation in the Luoyixi section, Guzhang County, Hunan Province, China. Sampling of the Luoyixi section in the boundary interval reveals 16 protoconodont and paraconodont taxa. The conodont succession can be correlated with the Gapparodus bisulcatus- Westergaardodina brevidens and the Shandongodus priscus- Hunanognathus tricuspidatus zones of South China and with the Laiwugnathus laiwuensis and the Shandongodus priscus zones of North China. Laiwugnathus laiwuensis occurs immediately below the lowest occurrence of Lejopyge laevigata. The first occurrence of Shandongodus priscus is 14.95 m above the base of the Lejopyge laevigata Zone. A significant change in the conodont associations occurs in the interval corresponding to the uppermost Lejopyge armata trilobite Zone. This interval is characterized by an increase in diversity with the appearance of the paracondont genera Furnishina and Laiwugnathus. Laiwugnathus laiwuensis, which occurs immediately below the lowest occurrence of Lejopyge laevigata, has a short stratigraphic record and allows confident correlation with North China.