TY - JOUR
T1 - Microbial life and biogeochemical cycling on land 3,220 million years ago
AU - Homann, Martin
AU - Sansjofre, Pierre
AU - Van Zuilen, Mark
AU - Heubeck, Christoph
AU - Gong, Jian
AU - Killingsworth, Bryan
AU - Foster, Ian S.
AU - Airo, Alessandro
AU - Van Kranendonk, Martin J.
AU - Ader, Magali
AU - Lalonde, Stefan V.
N1 - Funding Information:
This work was greatly supported by LabexMER ANR-10-LABX-19 and Prestige COFUND-GA-2013-609102 to M.H., and Deutsche Forschungsgemeinschaft (DFG) grant He2418/13–1 to C.H. S.V.L. and M.V.Z. acknowledge support from the European Research Council (ERC) under the European Union’s Horizon 2020 research and innovation programme (grant agreement n° 716515 for S.V.L. and grant agreement n° 646894 for M.V.Z.). We thank N. and D. Oosthuizen for access to the private Mountainlands nature reserve, S. Bläsing and M. Grund for assistance with sample collection, J.-P. Oldra for thin section preparation, and O. Lebeau, C. Tanvet, C. Liorzou, M.-L. Rouget and B. Gueguen for assistance with isotopic and elemental analysis.
Publisher Copyright:
© 2018, The Author(s).
PY - 2018/9/1
Y1 - 2018/9/1
N2 - The colonization of emergent continental landmass by microbial life was an evolutionary step of paramount importance in Earth history. Here we report direct fossil evidence for life on land 3,220 million years ago (Ma) in the form of terrestrial microbial mats draping fluvial conglomerates and gravelly sandstones of the Moodies Group, South Africa. Combined field, petrographic, carbon isotope and Raman spectroscopic analyses confirm the synsedimentary origin and biogenicity of these unique fossil mats as well as their fluvial habitat. The carbon isotope compositions of organic matter (δ13Corg) from these mats define a narrow range centred on −21‰, in contrast to fossil mats of marine origin from nearby tidal deposits that show δ13Corg values as low as −34‰. Bulk nitrogen isotope compositions (2 < δ15N < 5‰) are also significantly different from their marine counterparts (0 < δ15N < 3‰), which we interpret as reflecting denitrification in the terrestrial habitat, possibly of an atmospheric source of nitrate. Our results support the antiquity of a thriving terrestrial biosphere during the Palaeoarchaean and suggest that a complex and microbially driven redox landscape existed during the deposition of the Moodies Group, with distinct biogeochemical cycling occurring on land by 3,220 Ma.
AB - The colonization of emergent continental landmass by microbial life was an evolutionary step of paramount importance in Earth history. Here we report direct fossil evidence for life on land 3,220 million years ago (Ma) in the form of terrestrial microbial mats draping fluvial conglomerates and gravelly sandstones of the Moodies Group, South Africa. Combined field, petrographic, carbon isotope and Raman spectroscopic analyses confirm the synsedimentary origin and biogenicity of these unique fossil mats as well as their fluvial habitat. The carbon isotope compositions of organic matter (δ13Corg) from these mats define a narrow range centred on −21‰, in contrast to fossil mats of marine origin from nearby tidal deposits that show δ13Corg values as low as −34‰. Bulk nitrogen isotope compositions (2 < δ15N < 5‰) are also significantly different from their marine counterparts (0 < δ15N < 3‰), which we interpret as reflecting denitrification in the terrestrial habitat, possibly of an atmospheric source of nitrate. Our results support the antiquity of a thriving terrestrial biosphere during the Palaeoarchaean and suggest that a complex and microbially driven redox landscape existed during the deposition of the Moodies Group, with distinct biogeochemical cycling occurring on land by 3,220 Ma.
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U2 - 10.1038/s41561-018-0190-9
DO - 10.1038/s41561-018-0190-9
M3 - Article
AN - SCOPUS:85050553735
SN - 1752-0894
VL - 11
SP - 665
EP - 671
JO - Nature Geoscience
JF - Nature Geoscience
IS - 9
ER -
