Mercury Isotopes Track the Causes of Carbon Perturbations in the Early Permian Ocean and Continent

Abstract

The Early Permian witnessed the first icehouse-to-greenhouse turnover of the vegetated Earth, yet its climate dynamics remain enigmatic. Here, we used mercury (Hg) isotopes from pelagic and continental successions at low paleo-latitudes to track the perturbations of the global carbon (C) cycle and the climatic impact. Our results indicate that small-scale volcanism promoted marine organic C burial, and the concomitant extreme cooling triggered the waning of wetland ecosystems in North China block at ∼296.2 Ma. Subsequently, the mass-independent fractionation of odd Hg isotopes (Δ¹⁹⁹Hg) and C isotopes synchronously decline in the deep-marine succession, likely supporting progressive oxidation of terrestrial biomass and airborne release of Hg and C. Lowered C sequestration (as coal swamps) on land and dampened continental weathering limited the drawdown of CO₂ emissions from wildfires, initiating deglaciation. Our findings highlight that the climate forcing on terrestrial ecosystems could activate additional C reservoirs, driving Earth into a warmer state.