Maghemite soil nodules reveal the impact of fire on mineralogical and geochemical differentiation at the Earth's surface

We propose that the elevated Zr/Hf and Y/Ho ratios previously reported for Australian fluvial sediments reflect, at least in part, the long history of palaeo-fires in the catchments of these rivers, with preferential removal, transport and sedimentation of the readily weathered, high Y/Ho and Zr/Hf cortex material that is a product of thermal alteration of Fe nodules. In addition, since magnetic Fe nodules are demonstrably related to fire, they may represent a promising, directly dateable record of severe fires, which can complement the sedimentary charcoal record.