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Science 30 January 1981:
Vol. 211. no. 4481, pp. 478 - 480
DOI: 10.1126/science.211.4481.478
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Articles

Early Proterozoic Microfossils and Penecontemporaneous Quartz Cementation in the Sokoman Iron Formation, Canada

ANDREW H. KNOLL 1 and BRUCE SIMONSON 1

1 Department of Geology, Oberlin College, Oberlin, Ohio 44074

Early Proterozoic microfossils from the Sokoman Iron Formation, northeastern Canada, are indistinguishable from those of the Gunflint Formation in both morphology and inferred community structure. The contemporaneity of the Sokoman assemblage with the Bitter Springs-like cyanobacteria of the Belcher Supergroup indicates that differences between the two major types of early Proterozoic microbiotas are primarily ecological and not temporal (evolutionary) in nature. In arenaceous iron formations, microfossils are restricted to peloids and are absent from pore-filling silica interpreted as cement. Cemented arenaceous intraclasts indicate that some of the silica was penecontemporaneous, and the abundance of minus-cement porosity in arenaceous iron formations demonstrates that early (pre-compaction) cementation was common.

Submitted on October 15, 1980


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Science. ISSN 0036-8075 (print), 1095-9203 (online)