The suggestion in this paper that filamentous microfossils occurring in a 3.3 billion-year-old Archaean microbial mat (Westall et al., 2006*) could be abiogenic in origin or Endolithic contamination was not intentional. Westall et al. (2006*) clearly demonstrate by structural, micro-textural, and compositional analysis of the mat that the filamentous microstructures in question are integral parts of it and that the mat is syngenetic with the formation of the sediments. In situ Raman analyses also show that the mat consists of mature kerogen, as would be expected from a 3.3 billion-year old microbial mat having undergone the same lower greenschist metamorphism as the surrounding country rock. The data are not consistent with the mat (and the filaments it contains) being a younger Cenozoic structure.

The online version of the paper has been amended by Nature Geoscience as follows:

The microstructures are also present in silicified microbial mats in the 3.5-3.3-billion-year-old Josefsdal chert from Barberton greenstone belt, South Africa (Fig. 6f in ref. 4); in other settings similar microstructures may have been produced by Cenozoic endolithic organisms colonizing Archaean rocks (Fig. 2b,e and 3c in ref. 5).

*Westall F, de Ronde C. E. J., Southam G., Grassineau N., Colas M., Cockell C. and Lammer H. (2006b). Implications of a 3.472-3.333 Ga-old subaerial microbial mat from the Barberton greenstone belt, South Africa for the UV environmental conditions on the early Earth. Philosophical Transactions of the Royal Society of London Series B., 361, 1857–1875