The putative stromatolites with microstructures resembling bacteria
from the extensive stromatolitic formations of the 3,430-million-year-old
Strelley Pool Chert within the Warrawoona Group in Western Australia
have been hotly debated ever since their discovery by Lowe (1980,
1983). Others later ascribed conical form genera to abiotic evaporative
precipitation, and found no support for the microfossils as biomarkers.
Whether the microstructures within the Warrawoona Group stromatolites
are the imprints of ancient filamentous and possibly photosynthetic
microbes as argued by Schopf and Awramik became a heated debate
that remains unresolved. A recent and extensive study of seven
distinct stromatolitic form genera by Allwood certainly lends
support to proponents of biogenetic origins of the chert, since
the simultaneous set of forms is more difficult to explain with
known abiogenic processes. However, whether the microstructures
are fossil microbes remains unresolved. If they are microbe fossils,
there would still remain the critical question of whether they
are archaea, cyanobacteria, another type of photosynthetic bacteria,
chemosynthetic bacteria, or some combination of these. While
the debate rages on there are many who ascribe to the biogenic
nature of these deposits.
Javaux, E.J., Palaeontology: Microfossils
from early Earth, Nature Geoscience 4, 663–665 (2011).
Across Geologic Time