Lower Cambrian Burgess Shale-type fossil associations of South China

Abstract

Burgess Shale-type preservation has been reported from numerous Qiongzhusian and Canglangpuian sections of southern China during the last few decades. The Early Cambrian Chengjiang-type faunas of East Yunnan were of particular interest due to their excellent preservation and taxonomic diversity. A new definition and revision of the Chengjiang-type faunas is given, which indicates that distinct ecological variations occurred between the Chengjiang and Haikou faunas on a smaller scale, and between the arthropod-dominated faunas of shallow shelf and the sponge-dominated faunas of deeper shelf (e.g. Hunan) on a larger scale. Recent finds from the Yuanshan Formation of Deze, East Yunnan, and the Niutitang Formation of Zhongnan, Zunyi County, Guizhou, indicate a much wider distribution of Burgess Shale-type fauna during this period than was previously known. The present investigations of the latter fauna revealed the presence of Tsunyidiscus niutitangensis, Naraoia spinosa, N. cf. longicaudata, Isoxys curvirostratus, I. paradoxus, Skioldia aldna, Amplectobelua trispinata, cf. Tsunyiella diandongensis, Scenella sp., Cambrorhytium elongatum, Hyalosinica archaica, and Choiaella radiata. The occurrence of Burgess Shale-type preservation on the Yangtze Platform is not restricted to a small area as in the Burgess Shale, but known from a ca. 80 km wide geographic stripe extending for more than 500 km along the rim of Proterozoic platform core. This wide distribution of Burgess Shale-type preservation is interpreted to be triggered by the coincidence of specific palaeoecological conditions, including the rapid sedimentation of finest siliciclastic particles and the partial influence of suboxic water masses.