A potential GSSP for the base of the uppermost Cambrian stage, coinciding with the first appearance of Lotagnostus americanus at Wa'ergang, Hunan, China

The first appearance datum (FAD) of the cosmopolitan agnostoid trilobite Lotagnostus americanus is a widely used marker for defining the base of the uppermost stage of the Cambrian System. Detailed field study on the L. americanus-bearing interval of the Wa'ergang section, Hunan, China, reveals the FAD of L. americanus to be 29.65m above the base of the Shengjiawan Formation. This horizon is close to the lowest known occurrences of the intercontinentally distributed polymerid trilobites Hedinaspis regalis and Charchaqia norini. The section has strong potential as a candidate for defining a global standard stratotype-section and point marking the base of provisional Stage 10

Carbon-Isotope Excursions Recorded in the Cambrian System, South China: Implications for Mass Extinctions and Sea-Level Fluctuations

Cambrian carbonates with abundant fossils of agnostoid trilobites deposited on the southern slope (Jiangnan slope belt) of the Yangtze Platform and in the Jiangnan deepwater basin are well exposed in the Wangcun Section of western Hunan, South China, and in the Duibian A Section of western Zhejiang, southeastern China, respectively. To better understand the response of carbon-isotope excursions to depositional environment changes, mass extinctions and eustatic events, we collected 530 carbonate samples in fresh roadcut exposures of the two measured sections for analysis of carbon and oxygen isotopic compositions. Data of δ13C from the Wangcun Section, western Hunan, South China, demonstrate that the Cambrian carbon-isotope profile includes three remarkable positive excursions CPEwc-1, 2, 3 in the Upper Series 2, in the Lower and in the Middle Furongian Series. Three distinctive negative excursions CNEwc-1, 2, 3 were separately tested in the Lower Terreneuvian Series, Lower Series 3 and in the Upper Furongian Series. Similarly, in the corresponding horizons in the Duibian A Section, Zhejiang Province, southeastern China, three positive excursions CPEdb-1, 2, 3 and three negative excursions CNEdb-1, 2, 3 also have been discovered. We interpret these significant carbon-isotope excursions as being associated with enhanced biogenic productivity, mass extinctions and eustatic events