Terreneuvian small shelly faunas of East Yunnan (South China) and their biostratigraphic implications

摘要

The study discusses the detailed composition of Terreneuvian small shelly fossil (SSF) assemblages of eastern Yunnan Province (Meishucun, Xianfeng and Huize regions). The described sections represent shallow water deposits of the Yangtze Platform that include a number of stratigraphical hiati. The reported SSF assemblages can be assigned to the regional SSF biozones I-III (Anabarites trisulcatus-Protohertzina anabarica Assemblage Zone; Paragloborilus subglobosus-Purella squamulosa Assemblage Zone; Watsonella crosbyi Assemblage Zone). Zones II and III are slightly redefined based on new data. Two subzones of Zone II are proposed here, namely, Annelitellus yangtzensis-Obtusoconus honorabilis Subzone and Maikhanella cambriana-Oelandiella korobkovi Subzone. Claviconchella qianyii gen. et sp. nov. and Bubiites simplex gen. et sp. nov. are reported. Here we also provide a critical revision of the SSF distribution for the well-known Meishucun section. The correlation scheme for East Yunnan documents the extent and duration of stratigraphical hiati. The distribution of SSFs and the lithological characterization indicate three major events of exposure of the carbonate platform resulting in sedimentary breaks and possible karstification. This prompts new consideration of the previously described stable isotope stratigraphy of shallowplatform strata. Considering the complexity of the Terreneuvian Earth history aswell as the uniqueness of SSF, an integration of sedimentology, geochemistry and paleontology is needed for future SSF study.