Sustained and intensified lacustrine methane cycling during Early Permian climate warming.

Lakes are a major emitter of the atmospheric greenhouse gas methane (CH); however, their roles in past climate warming episodes remain poorly understood owing to a scarcity of geological records. Here we report the occurrence of sustained and intensified microbial CH cycling in paleo-Lake Junggar in northwestern China, one of the largest known Phanerozoic lakes, during Early Permian climate warming. High-precision U-Pb geochronology refines the age of the upper Lucaogou Formation to the Artinskian, which marks a major glacial-to-postglacial climate transition. The C-enriched authigenic dolomites indicate active methanogenesis in the anoxic lake sediments, and C-depleted hopanes suggest vigorous methanotrophy in the water column. The intensification of CH cycling coincided with increasing global temperature, as evidenced from elevated continental chemical weathering. Our results suggest that the lacustrine CH emissions acted as a positive feedback to global warming and contributed to the demise of the Late Paleozoic Ice Age.