Silicified floating microbial mats from the Mesoproterozoic Wumishan Formation, North China: preservation and ecological significance

This study focused on microbial mats and associated structures from the early Mesoproterozoic Wumishan Formation in North China. Through detailed paleoecological analysis, we identified a unique layered void structure preserved by rapid silicification, sandwiched between two horizontally layered remains of microbial mat: a benthic mat below and a floating mat above. Within the three-dimensional preserved “mat-layered void-mat” structures, multiple lines of evidence indicate that the void was an aquatic environment before diagenesis: for example, organic aggregates and vertically aligned beaded structures “suspended” within the layered void may represent remnants of microbial colonies suspended in the water. In the microbial mat above the layered void, downward-protruding spherical caps exhibit stable morphology, a consistent V_cap/V ratio, and upper surfaces aligned along a common horizontal line. These features suggest that the caps likely result from balanced forces, possibly influenced by buoyancy.

This research provides a rare glimpse into ancient microbial habitats, revealing the existence of free-floating cyanobacteria during the early Mesoproterozoic and suggesting their ancestors’ exploration of ecological niches, thereby enhancing our understanding of Mesoproterozoic microbial ecosystem evolution.