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˜3,426–3,350 Ma, Strelley Pool Formation, East Pilbara, Western Australia

Part of the Topics in Geobiology book series (TGBI, volume 31)

The Strelley Pool Formation is the rock unit that I myself have studied in most detail. I will now take this opportunity to summarise the various claims for life from this Formation; some are widely accessible in the literature, whilst others are new discoveries. Beginning at the base of the Formation, the Strelley Pool sandstone contains well rounded detrital grains of pyrite, chromite, rutile, and zircon, occurring as a heavy mineral placer-type deposit within a beach (or plausibly even river) setting. Many of the pyrite grains contain microborings (Fig. B43). These microborings typically comprise meandering cylindrical tunnels (microtubes) or channels, or spherical to elliptical surface pits. They have a near constant diameter of 1–5 μm and can penetrate into the substrate for several tens of microns. They are often concentrated in clumps along one side of a mineral grain. Some microborings show slight constrictions along their margins suggestive of colonisation by individual cells (Fig. B43). The microborings do not extend into adjacent grains nor into the microcrystalline silica cement. Nano-scale geochemical mapping shows enrichments of carbon and nitrogen within and/or along the edges of the microborings, consistent with some preservation of biological material (Wacey et al., 2008c).

Non-biological features which closely resemble microborings include microfractures and physico-chemical erosion and corrosion marks (Fig. B102). Microfracturing could be rejected as a formation mechanism for these microborings because they lack a jigsaw puzzle fit, are not sheet-like, and show a nearly constant diameter. Their origin from erosion and corrosion structures was also rejected because the microtubes penetrate far into the substrate and most are an order of magnitude smaller than co-occurring pit marks. Ambient inclusion trails can also result in microtubular structures but these would be expected to have striations along their length, polygonal cross sections and show evidence for a propelled crystal at their terminations (see Fig. B45).

Keywords

Greenstone Belt Trace Fossil Constant Diameter Geological Context Doushantuo Formation 
These keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.

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Recommended Reading

  1. Allwood, A. C., Walter, M. R., Kamber, B. S., Marshall, C. P., and Burch, I. W., 2006, Stromatolite reef from the Early Archaean era of Australia, Nature 441: 714–718.CrossRefGoogle Scholar
  2. Allwood, A. C., Walter, M. R., Burch, I. W., and Kamber, B. S., 2007, 3.43 billion-year-old stromatolite reef from the Pilbara Craton of Western Australia: ecosystem-scale insights to early life on Earth, Precambrian Research 158: 198–227.CrossRefGoogle Scholar
  3. Ascaso, C., and Wierzchos, J., 2002, New approaches to the study of Antarctic lithobiontic microorganisms and their inorganic traces, and their application in the detection of life in Martian rocks, International Microbiology 5: 215–222.CrossRefGoogle Scholar
  4. Brasier, M. D., McLoughlin, N., and Wacey, D., 2006, A fresh look at the fossil evidence for early Archaean cellular life, Philosophical Transactions of the Royal Society B 361: 887–902.CrossRefGoogle Scholar
  5. Etzel, K, Huber, H., Rachel, R., Schmalz, G., Thomm, M., and Depmeier, W., 2007, Pyrite surface alteration of synthetic single crystals as effect of microbial activity and crystallographic orientation, Advanced Materials Research 20–21: 350–353.CrossRefGoogle Scholar
  6. Friedmann, E. I., and Weed, R., 1987, Microbial trace-fossil formation, biogenous, and abiotic weathering in the Antarctic cold desert, Science 236: 703–705.CrossRefGoogle Scholar
  7. Hofmann, H. J., 2000, Archean stromatolites as microbial archives. In: Riding, R. E., and Awramik, S. M. (Eds.) Microbial Sediments, Springer, Berlin, pp. 315–327.Google Scholar
  8. Hofmann, H. J., Grey, K., Hickman, A. H., and Thorpe, R.I., 1999, Origin of 3.45 Ga Coniform Stromatolites in the Warrawoona Group, Western Australia, Bulletin of the Geological Society of America 111: 1256–1262.CrossRefGoogle Scholar
  9. Lowe, D. R., 1980, Stromatolites 3,400-Myr old from the Archean of Western Australia, Nature 284: 441–443.CrossRefGoogle Scholar
  10. Lowe, D. R., 1983, Restricted shallow-water sedimentation of early Archaean stromatolitic and evaporitic strata of the Strelley Pool chert, Pilbara block, Western Australia, Precambrian Research 19: 239–283.CrossRefGoogle Scholar
  11. Lowe, D. R., 1994, Abiological origin of described stromatolites older than 3.2 Ga, Geology 22: 387–390.CrossRefGoogle Scholar
  12. Perri, E., and Tucker, M., 2007, Bacterial fossils and microbial dolomite in Triassic stromatolites, Geology 35: 207–210.CrossRefGoogle Scholar
  13. Wacey, D., and Kilburn, M. R., 2008, Microbially mediated pyrite from the > 3400 Ma Strelley Pool sandstone, Western Australia, (in prep.).Google Scholar
  14. Wacey, D., Kilburn, M. R., McLoughlin, N., Parnell, J., Stoakes, C. A., and Brasier, M. D., 2008a, Use of NanoSIMS to investigate early life on Earth: ambient inclusion trails in a c. 3400 Ma sandstone, Journal of the Geological Society of London 165: 43–53.CrossRefGoogle Scholar
  15. Wacey, D., Kilburn, M. R., Stoakes, C. A., Aggleton, H., and Brasier, M.D., 2008b, Ambient inclusion trails: their recognition, age range and applicability to early life on earth. In: Dilek, Y. , Furnes, H., and Muehlenbachs, K. (Eds.) Links Between Geological Processes, Microbial Activities and Evolution of Life, Springer, pp. 113–133.Google Scholar
  16. Wacey, D., Kilburn, M., Brasier, M. D., Parnell, J., and Green, O. R., 2008c, Microbial oxidation of > 3400 Ma pyrite grains, (in prep.).Google Scholar

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