Silurian wildfire proxies and atmospheric oxygen

Abstract The earliest evidence of wildfire is documented from two localities: the early mid-Silurian Pen-y-lan Mudstone, Rumney, Wales (UK), and late Silurian Winnica Formation, Winnica, Poland. Nematophytes dominate both charcoal assemblages. Reflectance data indicate low-temperature fires with localized intense conditions. Fire temperatures are greater in older less evolved assemblage. These assemblages others, new previously documented, Devonian compared to box models atmospheric oxygen concentration (pO2). Based on modern charring experiments, these pO2 divergent broad trends predicted by COPSE-revisited GEOCARBSULFOR models. Sustained burns require a minimum threshold 16%, or ~0.75 present level. This was first met and, our indicate, exceeded then, later Silurian, attained again repeatedly.