Trilobite faunal successions across the Changshanian–Fengshanian Stage boundary, Chaomidian Formation (Furongian, Cambrian), Shandong Province, China

Abstract

The Changshanian and Fengshanian stages have long been employed as the uppermost Cambrian chronostratigraphic unit in North China. Previous studies largely focused on collecting simply the trilobite occurrences in the selected sections of the Chaomidian Formation and hence the trilobite faunal successions across the Changshanian¬–Fengshanian boundary have been poorly understood. This study attempts to document the bed¬¬–by–bed trilobite occurrences from the interval across the Changshanian–Fengshanian stage boundary in Tangwangzhai section, Shandong Province, China. The base of the Fengshanian Stage has long been recognized by FAD (First Appearance Datum) of Asioptychaspis and Tsinania in the Tangwangzhai section. A total of 29 genera and 41 species were recovered from the interval, which are assigned to the Kaolishania, Asioptychaspis–Tsinania, and Quadraticephalus zones in ascending order. Of these, Pagodia Walcott, 1905, Parakoldinioidia Endo, 1937, Koldinioidia Kobayashi, 1931, and Mansuyia Sun, 1924 of the Kaolishania Zone extended their ranges into the overlying Asioptychaspis–Tsinania Zone. Thus the presumed faunal turnover across the Changshanian–Fengshanian boundary is due to incomplete sampling. This is also consistent with the fact that no appreciable faunal changes across the coeval interval in South China, Australia, and Laurentia have been documented. In conclusion, the trilobite faunal successions across the Changshanian-Fengshanian boundary documented in this study will provide a reference for precise correlation of the Furongian strata in the Sino-Korean craton with those of other parts of the world.