Polyaromatic Hydrocarbon (PAHs) Concentration and Peak intensities Data

This data set is published as Wildfire, ecosystem, and climate interactions in the Early Triassic in Communication Earth and Enivronment (https://doi.org/10.1038/s43247-025-02789-x). Wildfires are an important component of Earth system dynamics particularly with respect to nutrient- and carbon cycling. The occurrence of wildfires is linked to complex feedbacks between climate, vegetation and landscape structure. It is therefore crucial to understand wildfire activity in the context of (paleo-)climatic and environmental change. In this study, we explore wildfire activity during the Early Triassic (Smithian and Spathian substages, ca. 250 million years ago) – a time interval characterized by large global carbon cycle perturbation, climatic oscillations, prominent terrestrial vegetation succession, along with radiation and extinction pulses – using polyaromatic hydrocarbon (PAH) biomarkers, which serve as a robust indicator of fire in sedimentary geologic archives. PAH abundances in shales from Spitsbergen show a prominent increase after the Smithian-Spathian boundary. Further, diagnostic ratios of PAHs suggest that these compounds were derived from relatively unaltered biomass as opposed to soil erosion and petrogenic carbon inputs or coal combustion vis-à-vis a coincidental Siberian Trap volcanism. Instead, our data indicates that as sea surface temperatures decline during the late Smithian, the hydrological cycle becomes less intense and large-scale changing vegetation successions become amenable to wildfire activity. From our results, we hypothesize that the change in regional wildfire regime would have exerted influence on other regional biogeochemical cycles, especially pyrogenic carbon, which in turn may have impacted long-term carbon sequestration dynamics. The coupled behavior of this water-vegetation-wildfire system amid key perturbations in Earth’s history provides new insights into imminent future consequences of human activities and the related impacts on climate.