Abstract
After the end-Permian mass extinction, the Earth system underwent extreme ecological and environmental fluctuations, including high temperatures, recurrent oceanic anoxia, and carbon cycle oscillations as demonstrated by the geochemical isotope proxy records. However, the underlying mechanism behind these oscillations remains poorly understood. Here we propose that they were produced by a coupled oscillation mode of marine phosphorus (P) and atmosphere-ocean carbon (A), driven by nonlinear redox controls on marine phosphorus burial. Our modeling demonstrates that the initial emplacement of the Siberian Traps and the mass extinction (on land and in the ocean) directly led to an early Triassic greenhouse. More importantly, it homogenized the ocean floor redox condition towards anoxia, activating amplifying feedbacks and destabilizing the system. The internal dynamics of an unstable system-rather than recurrent volcanic shocks-triggered the periodic oscillations (limit cycles) of serial excursions in carbonate carbon and uranium isotopes during the early Triassic.