Such
questions are timely, not least because attention is
now turning seriously toward a much more rigorous
analysis of the early terrestrial record, with fresh
insights into biological influences on the early terrestrial
carbonate record (e.g., Brasier 2011) and
emerging debates about bacterial oxygenation of
1,200–1,000 Ma old lake ecosystems (Parnell et al.
2010, Cumming et al. 2013).