Temporal and spatial evolution of wildfires during the Jurassic: From regional to global scale

With ongoing global warming, the frequency of wildfires has increased in many regions worldwide. To fully understand the manifold interactions between warming climates and wildfires it is necessary to study wildfires during Earth's history, preferably during periods characterized by warm climates. The Jurassic was a significant greenhouse period in Earth's history, and although evidence of combustion has been widely reported from deposits of Jurassic age, the spatio-temporal patterns and processes of Jurassic wildfires have not been studied on a global scale. In this study, evidence for wildfires occurring in deposits of the Early Jurassic Sangonghe Formation within the Junggar Basin is reported for the first time. It was found that the range of burning temperatures of these wildfires decreased from the late Early Jurassic to the early Middle Jurassic. Additionally, a comprehensive database, consisting of 196 published records, of Jurassic combustion products, including fossil charcoal, pyrogenic inertinite (fossil charcoal in coal deposits), and pyrogenic polycyclic aromatic hydrocarbons (PAHs), was compiled from the literature and analyzed for this study. Spatially, the database shows a high concentration of published evidence for Jurassic wildfire records in warm temperate climate zones in the mid-latitudes of the Northern Hemisphere. Temporally, trends in the Jurassic wildfires may be related to changes in atmospheric oxygen levels, climate change and fuels. However, like other global compilations on this topic for different periods of Earth's history, these results have to be seen with some care, as various taphonomic biases, including researcher bias and preservation issues, cannot be ruled as complicating factors.