New microbial fossils from 2 Gyr old rocks in Northern Michigan

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Abstract
A diverse, abundant, apparently procaryotic microflora is here reported from the Tyler Fm., upper Baraga Group, Gogebic County, Michigan. In addition, numerous chains of spheroids and grains of hematite after pyrite from the Baraga Group, Baraga County, suggest a microbial presence. The Tyler microbiota occurs in spheroidal clasts and oncoids comprised of pyritic cherts along the Black River east of Ironwood. It includes nine recognizably different microbial forms, four of filaments, two of spheroids, one umbrellaform, and two stellate. Its nearest affinities are with the stratigraphically lower microbiota of the Gunflint Iron‐formation, with which it shares such distinctive fossils as Gunflintia, Metallogenium (Eoastrion), and Kakabekia cf. K. umbellata Barghoorn. The Baraga assemblage, considered as a single form of “dubiofossil,”; includes strongly curvate chains of hematized pyrite spheroids and grains arranged in configurations suggesting filamentous procaryotes. It is from a black phosphatic layer 1‐ to 9‐mm thick on the Huron River about 6.5 km south of Lake Superior. Both occurrences are from stratigraphically higher in the succession of Baraga, Animikie, and equivalent rocks of the Lake Superior region than are the previously described nannofossils of the Gunflint, Biwabik, and Pokegama strata. They are thus younger but probably not much more recent than 2 × 109years ago.
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