Mass occurrence of benthic coccoid cyanobacteria and their role in the production of Neoarchean carbonates of South Africa |
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| Authors: | Jzef Kazmierczak Wladyslaw Altermann Barbara Kremer Stephan Kempe Patrick G Eriksson |
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| Institution: | aInstitute of Paleobiology, Polish Academy of Sciences, Twarda 51/55, PL-00818 Warszawa, Poland;bDepartment of Geology, University of Pretoria, 0002 Pretoria, South Africa;cDept. Earth and Environmental Sciences and GeoBioCenterLMU, Ludwig-Maximilians University, Luisenstr. 37, D-80333 München, Germany;dInstitute for Applied Geosciences TU Darmstadt, Schnittspahnstrasse 9, D-64287 Darmstadt, Germany |
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| Abstract: | The sparse Archean fossil record is based almost entirely on carbonaceous remnants of microorganisms cellularly preserved due to their early post-mortem silicification. Hitherto as an exception, sedimentary carbonate rocks from the Neoarchean Nauga Formation of South Africa contain calcified microbial mats composed of microbiota closely resembling modern benthic colonial cyanobacteria (Chroococcales and Pleurocapsales). Their remains, visible under the scanning electron microscope (SEM) after etching of polished rock samples, comprise capsular envelopes, mucilage sheaths, and groups of cells mineralized by calcium carbonate with an admixture of Al–K–Mg–Fe silicates. The capsular organization of the mucilaginous sheaths surrounding individual cells and cell clusters forming colonies and the mode of mineralization are the characteristic common features of the Neoarchean microbiota described and their modern analogues. The new findings indicate massive production of calcium carbonates by benthic coccoid cyanobacteria in the Neoarchean, and offer a solution to the problem of the origin of Archean carbonate platforms, stromatolites and microbial reefs. |
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| Keywords: | Neoarchean carbonate rocks Benthic coccoid cyanobacteria Campbellrand Subgroup Transvaal Supergroup South Africa |
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