The story
Oxygen isotopes in tiny tooth-like fossils called conodonts, studied by Sun Yadong and colleagues in South China and published in 2012, show that equatorial sea surface temperatures climbed to about 40 C around the Permian-Triassic boundary and stayed above 30 C for millions of years. That is hotter than most animals and plants can tolerate. The rock record agrees: for several million years there are no coal swamps, no true reefs, and almost no fossils of land vertebrates in the tropics.
The cause was the Siberian Traps. Their eruptions poured out carbon dioxide and methane and baked coal and carbonate rock into more gas, warming the air and acidifying and deoxygenating the oceans. Animals that survived were often small, and the cooler high latitudes became refuges, which is partly why Lystrosaurus dominated the south. Normal ecosystems returned only in the Middle Triassic, about five million years later, with reefs, forests and large reptiles back in place.
Why it mattered
- The hot spell explains why recovery from the Great Dying took millions of years instead of thousands.
- It shows how rapidly released volcanic carbon can push climate beyond what animals can survive, a lesson used in discussions of modern warming.
- The slow recovery left room for archosaurs to rise, setting the stage for the first dinosaurs.
Sources
- Tropical collapse caused by lethal heat University of Leeds
- Global coal gap between Permian-Triassic extinction and Middle Triassic recovery of peat-forming plants OSTI (Retallack et al.)
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