INERTINITE IN PERMIAN COALS FROM THE KUZNETSK BASIN, RUSSIA: IMPLICATIONS FOR THE INTERPRETATION OF WILDFIRE HISTORY

Late Palaeozoic atmospheric models suggest oxygen contents of the atmosphere could have reached 30% in the Permian Period. This would be expected to have caused prevalent wildfire activity, which in turn would have led to an increased likelihood of fossil charcoal (inertinite) occurrence in coal. Here we test this hypothesis by documenting the variation in inertinite distribution in Late Permian coal seams using petrographic techniques.

Fieldwork has been undertaken on coal seams from two mines in the Kuznetsk Basin, Western Siberia. Petrographic data from crushed coal samples from 13 seams (numbered 68-94) give an overview of the temporal variation in the peat-forming environment throughout the sequence. These indicate a wide variation in the inertinite content of the coals. These data are compared to small-scale variations seen in in situ coal pillars from two seams (coals 78 and 88) that, unlike the crushed samples, have retained the orientation of the original layering and hence document inertinite distribution and allow interpretation of fire type and frequency.

Most, if not all, inertinite macerals represent fossil charcoal and are the result of wildfire activity, either within the peat-forming area or outside the area with the charcoal being blown or washed into the mire. Scattered inertodetrinite may represent wind blown micro-charcoal from wildfires. However, larger fragments of fusinite and semi-fusinite, probably represent meso- and macro-charcoal that may be from local fires or transported into the mire through water transport.

We illustrate the range of inertinite occurrences in the coals and show a wide range of origin from background regional fires to more local fires in the mire system and show how the depositional setting may also influence the record of wildfire.