Microfossils in 2000 Ma old cherty stromatolites of the Franceville Group, Gabon

A well-preserved microbial assemblage has been found in Paleoproterozoic cherty stromatolites from the 2000 Ma old Franceville Group, Gabon. This assemblage contains coccoids and star-like forms, filaments and budding tubular forms. These various forms are mostly of cyanobacterial affinity, and among them nostocalean akinetes (Archaeoel-lipsoides) are reported, for the first time, from rocks older than the Mesoproterozoic. The most noteworthy discovery in the Franceville biota is the Gunflint-type association Huroniospora-Gunflintia- Archaeorestis, known also - without Archaeorestis - in other Paleoproterozoic assemblages throughout the world. The present assemblage comprises 13 taxa consisting of 8 species belonging to 10 genera and 2 unnamed forms. It is dominated by Gunflintia filaments, regarded as a mat-building community and by Huroniospora coccoids, probably mat-dwellers and/or plankters. The rare and large forms such as akinetes of Archaeoellipsoides were allochthonous and presumably planktonic.