Nano-porous pyrite and organic matter in 3.5-billion-year-old stromatolites record primordial life

Type Article
Date 2019-11
Language English
Author(s) Baumgartner Raphael J.1, Van Kranendonk Martin J.1, Wacey DavidORCID2, Fiorentini Marco L.3, Saunders MartinORCID2, Caruso Stefano3, Pages Anais4, Homann MartinORCID5, Guagliardo PaulORCID3
Affiliation(s) 1 : Univ New South Wales, Sch Biol Earth & Environm Sci, Australian Ctr Astrobiol, Kensington, NSW 2052, Australia.
2 : Univ Western Australia, Ctr Microscopy Characterizat & Anal, Perth, WA 6009, Australia.
3 : Univ Western Australia, Sch Earth Sci, Ctr Explorat Targeting, Perth, WA 6009, Australia.
4 : Commonwealth Sci & Ind Res Org, Mineral Resources, Kensington, WA 6151, Australia.
5 : CNRS, UMR6538, European Inst Marine Studies, Lab Geosci Ocean, Technopole Brest Iroise, F-29280 Plouzane, France.
Source Geology (0091-7613) (Geological Soc Amer, Inc), 2019-11 , Vol. 47 , N. 11 , P. 1039-1043
DOI 10.1130/G46365.1
WOS© Times Cited 52

Stromatolites of the similar to 3.5 billion-year-old Dresser Formation (Pilbara Craton, Western Australia) are considered to be some of Earth's earliest convincing evidence of life. However, uniquely biogenic interpretations based on surface outcrops are precluded by weathering, which has altered primary mineralogy and inhibited the preservation of microbial remains. Here, we report on exceptionally preserved, strongly sulfidized stromatolites obtained by diamond drilling from below the weathering profile. These stromatolites lie within undeformed hydrothermal-sedimentary strata and show textural features that are indicative of biogenic origins, including upward-broadening and/or upward-branching digitate forms, wavy to wrinkly laminae, and finely laminated columns that show a thickening of laminae over flexure crests. High-resolution textural, mineralogical, and chemical analysis reveals that the stromatolites are dominated by petrographically earliest, nano-porous pyrite that contains thermally mature, N-bearing organic matter (OM). This nano-porous pyrite is consistent with a formation via sulfidization of an originally OM-dominated matrix. Evidence for its relationship with microbial communities are entombed OM strands and filaments, whose microtexture and chemistry are consistent with an origin as mineralized biofilm remains, and carbon isotope data of extracted OM (delta C-13(OM) = -29.6 parts per thousand +/- 0.3 parts per thousand VPDB [Vienna Peedee belemnite]), which lie within the range of biological matter. Collectively, our findings provide exceptional evidence for the biogenicity of some of Earth's oldest stromatolites through preservation of OM, including microbial remains, by sulfidization.

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Baumgartner Raphael J., Van Kranendonk Martin J., Wacey David, Fiorentini Marco L., Saunders Martin, Caruso Stefano, Pages Anais, Homann Martin, Guagliardo Paul (2019). Nano-porous pyrite and organic matter in 3.5-billion-year-old stromatolites record primordial life. Geology, 47(11), 1039-1043. Publisher's official version : , Open Access version :