Lacustrine methane release on the Tibetan Plateau as an important driver of Early Miocene global warming

Abstract. The Early Miocene was a key period of significant global warming. While previous studies often attributed this warming to the India-Asia collision and associated volcanism, an alternative mechanism may involve large-scale methane release from organic-rich lake sediments. To test the hypothesis that methane emissions from Tibetan Plateau lakes contributed to Early Miocene warming, we analyzed organic carbon, stable isotopes, and elemental concentrations in samples from the organic-rich Dingqinghu Formation in the Lunpola Basin, central Tibetan Plateau. Our results identify an exceptionally strong positive carbonate carbon isotope excursion (δ¹³C_carb up to +13.79 ‰) within the lacustrine deposits. The large carbon isotope difference between carbonate and organic matter (Δ¹³C > 32 ‰) indicates that methanogenesis, specifically via acetate fermentation, was the dominant microbial process. Extremely low sulfur contents likely suppressed sulfate-driven anaerobic oxidation of methane, facilitating direct methane release to the atmosphere. Furthermore, volcanic activity during this interval was limited, suggesting a negligible role in carbon cycle perturbations. The close temporal correspondence between Early Miocene warming, rising atmospheric CO₂, and methane emissions documented on the Tibetan Plateau indicates that methane release from these plateau lakes may have played an important role in driving global warming and increasing contemporary CO₂ levels.