Microbial Fossils from the Kheinjua Formation, Middle Proterozoic Semri Group (lower Vindhyan)~ Son Valley Area, Central India

McMenamin, D.S., Kumar, S. and Awramik, S.M., 1983. Microbial fossils from the Kheinjua Format ion, Middle Proterozoic Semri Group (Lower Vindhyan), Son Valley area, central India. Precambrian Res., 21: 247--271. Abundant coccoid and filamentous microfosslls are found in petrographic thin sections of stratiform stromatoli t ic cherts from the z1200 Ma-old Fawn Limestone of the Kheinjua Format ion, lower Vindhyan Supergroup, central India. The assemblages is dominated by coccoid forms of probable chroococcacean and entophysalidacean affinities; most filaments closely resemble the osciliatoriacean Gunflintia minuta. Unlike other Middle to Late Proterozoic stromatoli t ic microbiotas, the Kheinjua is dominated by microfossils < 10 , m in diameter. Another notable feature of the assemblage is that its microfossiis are found in extensive sheets of amorphous organic matrix, which also contains rare bizarre morphs unique to this formation. Taxonomically, the Kheinjua microbiota most closely resembles Proterozoic microbiotas described from the Belcher Islands (Kasegalik Formation), McArthur Group, Bitter Springs Format ion, and the Yudoma Suite. The following taxa are formally described: C h r o o c o c c a c e a e Myxococcoides minor Schopf, Eosynechococcus isolatus n.sp., Tetraphycus congregatus n.sp., Kheinjuasphaera vulgaris n.gen., n.sp., Glenobotrydion aenigmatis Schopf, Melasmatosphaera media Hotmann; Entophysalidaceae Eoentophysalis belcherends Hofmann, E. magna n. sp.; Oscfllatoriaceae cf. Gunflinta minuta Barghoorn, Eomycetopsis? siberiensis Lo.