Abstract:
The Paleogene-Neogene period constitutes a critical transitional stage in the formation of modern climate and vegetation. Wildfires play a vital role in global ecosystems. Research on global Paleogene-Neogene paleowildfire events and their influencing factors is essential. It holds great significance for revealing the driving mechanisms of wildfires. Inertinite in sediments has been widely used as evidence for the occurrence of wildfires. The distribution patterns and controlling factors of Paleogene-Neogene wildfires remain unclear. To this end,
1269 inertinite data worldwide from the Paleogene-Neogene period have been collected and collated. The research results reveal that records of Paleogene-Neogene wildfire events are mainly concentrated in mid-low latitude regions, with fewer records in high latitudes. Wildfire records are predominantly in the Northern Hemisphere, with fewer in the Southern Hemisphere. The global average volume fraction of inertinite during the Paleogene-Neogene period ranges from 2.62% to 12.4%. The average inertinite volume fraction was relatively high in the Paleocene (12.4%), continuously decreased in the Eocene (4.32%), Oligocene (3.47%) and Miocene (2.62%), and increased in the Pliocene (6.59%). It was less than 5% in most periods, reflecting relatively low wildfire activity during the Paleogene-Neogene period. Based on the statistical volume fraction of inertinite from the Paleogene-Neogene, the estimated range of atmospheric oxygen volume fraction during this period is 20.64%–23.24%. The relatively high inertinite volume fraction in the Paleocene may be related to its relatively high atmospheric oxygen volume fraction. Affected by factors such as the decrease in atmospheric oxygen volume fraction, changes in vegetation types, CO
2 volume fraction and precipitation, the inertinite volume fraction continued to decline from the Eocene to the Miocene. The increase in inertinite volume fraction in the Pliocene may be associated with arid environments and the expansion of grasslands. Comprehensive analysis indicates that the relatively low atmospheric oxygen volume fraction during the Paleogene-Neogene period may be the key factor for the low wildfire activity, and CO
2 volume fraction, temperature, precipitation and vegetation types are important factors affecting the changes in wildfire activity.