ABSTRACT
Fire may not only be seen as a destructive force but also as a preservational mechanism. Charcoal, a fire residue, preserves anatomy allowing for the identification of plants, is inert, and may survive transport, burial and diagenesis. Evidence of fires in deep time, before man, comes predominantly from macroscopic charcoal deposits. Our earliest records of wildfire come from the late Silurian and early Devonian (420 to 400 million years ago) but evidence of fire through the Devonian (400 to 350 my) is rare, possibly because of low atmospheric oxygen. Atmospheric oxygen levels are thought to have risen rapidly through the Carboniferous and Permian (350 to 250 my) and this coincides with the spread of fire into a range of environments from lowland tropical mires to floodplains and in to upland regions. Sedimentological evidence suggests that post-fire erosion-depositional systems are more widespread in the fossil record than has been previously thought. Studies of charcoalified plants not only provide data on the evolution of plants but also of fire-prone vegetation. Fire has played an important role in the Earth system processes for over 400 million years impacting on the atmosphere, climate and the evolution of terrestrial ecosystems. It is in this context that we should see the Earth as a ‘fire planet’ (S.J. Pyne).
