The use of charcoal to interpret Cretaceous wildfires and volcanic activity

Charcoal is abundant in most post-Silurian sedimentary sequences and even in some volcanic rocks. The study of charcoal can provide important information on not only what plants were being burned but also on how the charcoal residue was formed. Most charcoal encountered in the sedimentary record is a result of lightning-ignited wildfires but volcanic activity may also act as an ignition source. Charcoal preserves exquisite anatomical data that can be studied by a range of microscopical techniques including scanning electron microscopy that allows the identity of the plants to be determined. Fires have a major impact on a range of environments and ecosystems. The elevated oxygen content of the atmosphere indicates that the Cretaceous can be considered a “high-fire” world. Fire activity should be taken into account in Cretaceous vegetation and climate models. The occurrence of charcoal at the Cretaceous-Tertiary Boundary has been highlighted as evidence for a global fire following an asteroid impact, but this interpretation is questionable.
Charcoal may be found within volcanic rocks, especially from deposits of pyroclastic flows and from basaltic lavas. This may provide data on the entombed vegetation but reflectance data may be used to provide interpretations of deposit temperatures. Charcoal is information-rich but yet is an under-utilized resource. Fire is an expression of life on Earth and an index of life’s history and is relevant for geology, biology, human history, physics, and global chemistry.