Furongian (late Cambrian) trilobites from the Asioptychaspis subglobosa Zone of the Hwajeol Formation, Korea

Abstract

The Hwajeol Formation of the Taebaek Group, Korea extends from the Jiangshanian Stage to the Cambrian Stage 10 in age. The lowermost part of the formation is known to contain the Asioptychaspis Zone which is closely correlated to the Asioptychaspis-Tsinania Zone of North China. This study documents silicified trilobites from the lowermost part of the Hwajeol Formation in the Sagundari section. Asioptychaspis subglobosa occurs throughout the interval, hence the biozone is renamed as Asioptychaspis subglobosa Zone in this study. The Asioptychaspis subglobosa Zone of the Hwajeol Formation yields xx polymerid species belong to xx genera. Among other species, the occurrence of the genus Caznaia is stratigraphically significant because two biozones were set up in Australia on the basis of the Caznaia species: i.e., the Rhaptagnostus clarki patulus-Caznaia squamosa and Rhaptagnostus clarki prolatus-Caznaia sectatrix zones in ascending order. Due to the lack of globally-occurring trilobites and conodonts, the international correlation of these biozones of Australia has been rather dubious. The occurrence of Caznaia from the Asioptychaspis subglobosa Zone of Korea indicates that the Rhaptagnostus clarki patulus-Caznaia squamosa and Rhaptagnostus clarki prolatus-Caznaia sectatrix zones of Australia are correlated to the Asioptychaspis subglobosa Zone of Korea and the Asioptychapis-Tsinania Zone of North China.