FTIR spectroscopy and reflectance of modern charcoals and fungal decayed woods: implications for studies of inertinite in coals

The chemical and physical characteristics of laboratory produced charcoals, natural charcoals, fungal decayed woods and inertinite from a variety of Western Canadian coals have been investigated using FTIR and standard petrologic techniques. Our studies confirm and extend earlier work in showing that almost all inertinite macerals can be attributed to wildfire in peat swamps, and that variation in the petrological characteristics of inertinite are a product of temperature, duration of heating and the nature of the initial plant material. The relationships between reflectance and temperature, as well as heating duration of charcoal formation are established as a reference for the examination of inertinite and the probable temperature of inertinite precursor (fossil charcoal) formation in paleo-wildfire. Fungi do not directly contribute to the formation of charcoal and inertinite apart from the fungal bodies themselves (funginite: sclerotia and hyphae) and perhaps by increasing the extent of shrinkage and cracking (increasing surface area) of the plant materials and thus susceptibility to charring. Evidence of fungal activity progressively decreases with increasing degree of charing in response to duration of heating or increased charing temperature. The reflectance values and FTIR spectral characteristics of inertinites in Western Canadian coal suggest that most inertinite formed by wildfires at temperatures over 400 degrees C. The great abundance of semifusinite in Western Canadian coal may reflect frequent but short duration wildfires in precursor peat swamps. (C) 1998 Elsevier Science B.V. All rights reserved.