Anatomical Evidence in the Detection of the Earliest Wildfires

Abstract

The recognition of fossilized charcoal has revealed a long history of wildfire, although the earliest (pre-Late Devonian) records remain conjectural. A variety of approaches (experimental and natural charring, comparative anatomy of a range of plant tissues following combustion, and preliminary reflectance studies) demonstrates that smoldering surface fires already occurred 405 million years ago (Lochkovian; Early Devonian) in a vegetation of short stature composed mainly of small plants with smooth stems and terminal sporangia. In addition, the textures recorded in pyrite permineralizations are anomalous when compared with those of Lower Devonian and later examples, and indicative of the involvement of different taphonomic processes. From comparison with experimentally pyritized charcoal, they further suggest that the plants were burned before fossilization. The small millimeter-sized fossils (mesofossils) with remarkable, uncompressed cellular preservation indicate the importance of charcoalification in the determination of affinities and functioning of early land plants, and hence the reconstruction of ancient ecosystems.