Cretaceous wildfires and their impact on the Earth system

A comprehensive compilation of literature on global Cretaceous charcoal occurrences shows that from the Valanginian on throughout the Cretaceous, terrestrial sedimentary systems frequently preserve charcoal in abundance. This observation indicates that fires were widespread and frequent and that the Cretaceous can be considered a "high-fire" world. This increased fire activity has been linked to elevated atmospheric oxygen concentrations, predicted as in excess of 21% throughout this period and 25% during some stages. This extensive wildfire activity would have affected the health, composition, and structure of the vegetation and, through habitat loss, probably the fauna. For these reasons, fire activity should be taken into account in Cretaceous vegetation and climate models. Major changes in vegetation occurred during the Cretaceous. In particular, the angiosperms rose to dominance. Some early angiosperms are interpreted as being of weedy form and as having thrived in disturbed environments. Fires may have promoted angiosperm diversification and spread through their role in environmental perturbation. The significant number of charred angiosperm mesofossil assemblages described from the late Early Cretaceous supports this hypothesis. Additionally, it can be speculated that severe fires during the Cretaceous would have engendered increased levels of runoff and erosion leading to the mobilization of significant amounts of phosphorous into marine settings. This phosphorous runoff would have contributed to oceanic planktonic blooms and their associated anoxic events. Fire activity remained prevalent into the Late Cretaceous. New data on the distribution of charcoal in the Campanian of Dinosaur Provincial Park, Canada indicate extensive charcoal deposits over a 1.7 myr interval and suggest that some catastrophic bone bed accumulations may have been the result of post-fire erosion-depositional systems. (C) 2012 Elsevier Ltd. All rights reserved.