A major fire event recorded in the mesofossils and petrology of the Late Permian, Lower Whybrow coal seam, Sydney Basin, Australia

Abstract

Petrographic and mesofossil analyses of plies from the Late Permian, Lower Whybrow coal, New South Wales, Australia have revealed a significant fire event in both the swamp setting and the hinterland. The fire event is characterised by a change in the maceral composition, the seam during this interval being dominated by inertinite, especially semifusinite. Following the fire event, the mineral matter content of the coal increases. This may be the result of increased run-off and erosion in the hinterland due to destruction of vegetation. This major fire event is also reflected in a change in the vegetation, as represented by the mesofossil content of the seam. Prior to the fire event the seam contains abundant bisaccate taeniate pollen sporangia and seed-like bodies of possible glossopterid affinity. These are lost at the ply in which the fire event is recorded; though seed-like bodies become important again later. The fire event also corresponds to a change in the megaspore content of the coal, a new species appearing, perhaps as a result of hydrological change. Following this major fire event, a mineral rich ply was deposited which contains miospore masses of spores from fern-like plants, possibly representing a re-colonisation event by rhizomorphs after vegetation death. This evidence for a major fire, and its implications for the origin of inertinites, leads to the conclusion that throughout this, and other Permian Gondwana coals, fire was an integral part of the temperate, mid–high latitude, southern hemisphere swamp ecosystem.