Just heard a fantastic talk at GSA annual meeting by Victoria Hudspith, a student of Cynthia Belcher (see previous blog entry), on "Latest Permian chars may derive from wildfires, not coal combustion" (https://gsa.confex.com/gsa/2014AM/webprogram/Paper248275.html). This research is also found in the just published article of the same title (Geology, October 2014, v. 42, p. 879-882, first published on August 28, 2014, doi:10.1130/G35920.1), the volume of which I am told is available in the GSA booth area in the Exhibits hall.
Hudspith and co-authors present evidence that vesiculated chars and other fly-ash-like particles found in end-Permian high-latitude sediments can be produced from burning of peatlands and forests. Fly ash textures are normally associated with the burning of coal. (Fly ash is the uncombusted or partially-combusted residue that 'flies' up the chimney during coal combustion; theoretically, it should all be mineral matter, but if organic combustion is incomplete, there will be carbonaceous particles also.) Earlier authors hypothesized that the presence of vesiculated chars meant explosive burning of Siberian trap intruded coals, releasing methane that contributed to the largest mass extinction in Earth history. Hudspith's research indicates that burning of coal is not required to produce vesiculated chars.
I pondered myself the presence of vesiculated chars among the inertinite maceral population in Triassic Richmond basin and Jurassic Newark basin sediments that I point-counted for my dissertation particulate organic sedimentation study of cyclic rift-basin lacustrine sediments (PhD 2002; study not yet published except in meeting abstracts: my bad). If vesiculated char implied burning coal, how could that be present in basins in which 1) there were no coal beds (Newark), 2) burial, coalification, and exhumation would not have yet happened to syn-rift peat swamps (Richmond), or 3) there was no major geologic ignition process for possibly exhumed Late Paleozoic coals 100 km to the west? The results of Hudspith's experiments burning various uncoalified terrestrial plants and plant debris, and petrographically examining the products, resolves that conundrum.