Wildfires in the Late Palaeozoic of Central Europe-an overview of the Rotliegend (Upper Carboniferous–Lower Permian) of the Saar–Nahe Basin (SW-Germany)

摘要

Fossil charcoal from a number of different sedimentary settings (e.g., lakes, floodplains, tuffs/tuffites) is reported from the Rotliegend (Late Carboniferous–Early Permian) of the Saar–Nahe Basin in SW–Germany. It is one of the largest Carboniferous–Permian basins, which developed during the late Variscan in Europe. The sedimentary deposits encompass the Carboniferous–Permian boundary, thus enabling us to examine the development of fire regimes parallel to the reconstructed drop in atmospheric O_2 across this boundary. The majority of the identified macroscopical charcoal remains belongs to the conifers or other gymnosperms, maybe pointing to a more fire-prone vegetation in the drier hinterland, preferentially inhabited by these plants. Most wildfires, especially those which took place during the deposition of the Lower Rotliegend (～Late Carboniferous), have probably been ignited by lightning, whereas in the Upper Rotliegend (～Early Permian), an intense volcanism may have also acted as an important additional source of ignition. In the Lower Rotliegend, charcoals occur in nearly all sedimentary facies types, whereas in the Upper Rotliegend, charcoal has, so far, only been found in some volcanically influenced deposits. The absence of charcoal in most sediments from the Upper Rotliegend may be explained by: (i) low atmospheric oxygen levels, leading to reduced fire–frequencies; (ii) a generally sparse vegetation cover; (iii) the mechanical breakdown of macroscopic charcoal under the prevailing semiarid conditions.