A Flourishing Planktonic Microbial Community in an Interglacial Offshore Environment: Silicified Microfossils From the Cryogenian Datangpo Formation, South China

The Cryogenian global glaciations profoundly shaped the evolution of Earth's ecosystem. An active Cryogenian biosphere accompanied by key evolutionary innovations has been indicated by geochemical and phylogenetic studies, although fossil records from Cryogenian strata are limited. In this study, we report a silicified microfossil assemblage from the Cryogenian Datangpo Formation in an interglacial offshore setting of the Yangtze block, South China. The Datangpo assemblage majorly comprises coccoidal microfossils classified into three morphological types, with minor components of fragmented filamentous forms. Morphological and structural observations combined with Raman spectroscopic analysis indicate that this microfossil assemblage may represent a planktonic microbial community dominated by cyanobacteria. The exceptionally silicified taphonomic window in the Datangpo microfossil assemblage provides a snapshot of primary producers in an offshore environment between the two Cryogenian global glaciations.