Continental records of organic carbon isotopic composition (δ13Corg), weathering, paleoclimate and wildfire linked to the End-Permian Mass Extinction

Abstract

The late Permian was the acme of Pangea assembly, with collision and subduction of global plates accompanied by major changes in atmospheric composition, paleoclimates and paleoenvironments of the Earth's surface system. These events are extensively recorded in marine successions from the Tethys, but much less are known from continental successions that typically lack high-resolution stratigraphic control. In order to reveal these fluctuations in terrestrial strata and their relationship with the End-Permian Mass Extinction (EPME), we investigate continental δ13Corg, mercury and nickel concentrations, wildfire, and climate change proxies from the late Permian Changhsingian stage to Early Triassic Induan stage in the Yuzhou coalfield in the North China Plate (NCP). Results show two negative organic carbon isotope excursions (CIE) within the Changhsingian aged Sunjiagou Formation, the first (CIEI, 2.2‰) during mid-Changhsingian and a second, larger, excursion (CIE-II, 2.7‰) near the end of the Changhsingian that coincides with the peaks in the Chemical Index of Alteration (CIA) value and extinction of plant species. We infer CIE-II to be the global negative excursion of δ13Corg associated with the EPME. Arid climates prevailed in the study area from the Changhsingian to the early Induan inferred from the low kaolinite contents and weak continental weathering, except for two short-duration episodes with higher humidity that correspond with CIE-I and CIE-II. Extremely high fusinite content (x̄ = 63.1%) and its increasing abundance through the Changhsingian indicates that frequent wildfires may have been a direct cause for both the destruction of terrestrial vegetation ecosystems and the rapid decline of terrestrial biodiversity at the EPME. We consider that terrestrial ecosystems may have played an important role in the extinction of marine communities at the EPME. This represents the first time the EMPE has been demonstrated in the NCP based on combined evidence from negative carbon isotope excursion, concurrent weathering trends, Ni/Al ratio and biotic extinctions, representing an important step in accurately identifying and correlating the EPME in continental settings from the NCP.