Massive release of predominantly magmatic carbon drove an Early Jurassic hyperthermal

The Toarcian Oceanic Anoxic Event (T-OAE, ~183 Ma) was a major hyperthermal event in the Phanerozoic, characterised by massive carbon release and widespread organic carbon burial. However, the source(s), flux, and sequestration pathways of carbon remain uncertain. Here, we assimilate globally representative carbon isotope and atmospheric CO₂ records into an Earth system model to decipher the carbon cycle during the T-OAE. Our simulations indicate the release of ~18,000 Pg C of predominantly magmatic carbon through the T-OAE, though with an input of carbon from thermogenic and/or biogenic sources at the onset of the event. We show that at least 6800 Pg of organic carbon was buried during the event, which, combined with silicate weathering-driven excess carbon consumption (~6000 Pg C), helped the Earth's climate system to recover from large-scale carbon release. Our results provide quantitative constraints on the tempo, magnitude, and recovery mechanisms of carbon-cycle perturbations during extreme greenhouse intervals.