The Permian-Triassic mass extinction was one of the worst crises for life on earth, killing >90% of marine species, which induced the carbon cycle perturbation during the entire Early Triassic. Previous studies indicated the global CO 2 concentration dropped sharply from 2,800 ppmv to a level of approximately 450 ppmv (comparable to the present) at the Early–Middle Triassic boundary. This optimal CO 2 level, a stabilized recor...