Anomalies of sulfur compound-specific molecular fossils link terrestrial ecosystem collapse to the end-Triassic crisis

The end-Triassic mass extinction (ETE), one of the “Big Five” in Earth history, was triggered by Central Atlantic Magmatic Province (CAMP) volcanism, releasing voluminous CO2, SO2 and halocarbons, which affected global marine and terrestrial ecosystems through atmospheric circulations. The terrestrial ecosystem collapse is commonly attributed to CO2-driven greenhouse effects changing climates that consequently impacted flora and fauna, but this fails to explain why atmospheric CO2 with long retention time just dominates a range of short-lived crises. Here, we investigate two terrestrial Triassic-Jurassic sections in each high- and low/middle- paleolatitude, finding anomalies of sulfur-associated molecular fossils, biomarker proxies of “high-temperature wildfires” and higher plants burial. These coincide with relatively short CAMP climax (lasting ~ 60,000 years). We propose a novel hypothesis that the high-intensity pulses of acid rains originated from CAMP climax dominated catastrophic defoliation, which oversupply dead moisture-free biomass as fuels in unusual rates, leaving coeval widespread abnormally high-temperature wildfires and spikes of sulfur compound-specific molecules in terrestrial sediments as fingerprints of acid rain deposition.