Pelsonian negative carbon isotope excursion (PENCIE): A Tethys-wide abnormal carbon cycle event in the Middle Triassic

After the highly perturbed, post-crisis environments of the Early Triassic, the Middle Triassic was characterized by stabilization of environmental and climatic conditions, as evidenced by geochemical profiles, including the carbon cycle. Here, we identify an unexpected new episode of global carbon cycle perturbation during the early Middle Triassic (∼244–243 Ma), indicated by the Pelsonian negative carbonate carbon isotope excursions (PENCIE) and mercury anomalies, which occurred widely across Tethys. These perturbations may have been driven by volcanic activity, as indicated by anomalous peaks in the Hg, Hg/TOC and Hg/TS signals. In addition, Sr isotope, gamma ray and other data suggest that the Hg anomalies were driven by increased terrestrial inputs. Environmental change during the Pelsonian was coupled with the emergence of diverse marine faunas that represented a fully recovered ecosystem. Nutrients brought in by volcanism or inputs from terrestrial sources during environmental perturbation may have contributed to biotic recovery.