Impact of wildfires on Gondwanan flora during the Permian–Triassic transition

The Permian–Triassic (P/T) transition is a critical juncture in Earth’s history. Rock sequences from this interval record a significant loss of biodiversity in marine environments, a reduction of terrestrial vertebrates and the initiation of the Lower Triassic coal gap. Despite these records, little is known about the transition’s impact on floral diversity and its relation to ecological perturbations. Here, we describe the hydrocarbons and charcoals preserved in Upper Permian–Lower Triassic fluviatile sediments from the East Indian Raniganj sub-basin and link them with potential vegetation shifts in Gondwana. Enrichment of pyrogenic polycyclic aromatic hydrocarbons (PAHs) and charcoalified tracheids reveal the presence of chronic wildfires in this floodplain environment. The pattern of vegetation shifts observed corresponds to a reduction of coal-forming Glossopteris Flora, while selective survival and diversification of fire-adapted conifers during the Induan age suggest that wildfires may have exerted an evolutionary pressure. The deficit of coal during the Induan is a clear sign of a decrease in vegetation density. We contend that recolonisation during the Induan occurred in an arid, fire-prone regime which produced charcoal despite scant vegetation cover.