Organic carbon burial in a middle Eocene East Asian paleolake: Response to global and regional climate changes

Organic carbon burial in lakes represents an important natural mechanism for long-term organic carbon sequestration and a critical component of the global carbon cycle. However, the dynamics of lacustrine organic carbon burial are more complex than marine systems, and the mechanisms linking it to global and regional tectonic-climatic factors remain poorly understood. Here, we present an organic carbon burial record from the Dongying paleolake in the Bohai Bay Basin during the middle Eocene, integrated with high-resolution reconstructions of terrestrial paleoclimate and paleolake environments, to elucidate the controls on organic carbon burial in large lacustrine systems. Our findings indicate that middle Eocene terrestrial paleoclimate evolution in the Bohai Bay Basin was modulated by both global and regional forcing, resulting in two climate transitions at ∼43 Ma and ∼42 Ma. The first transition is attributed to the southward migration of subtropical high pressure caused by global cooling, while the second transition is associated with regional factors, including the Tibetan Plateau uplift and Paratethys Sea retreat. Terrestrial paleoclimate profoundly influenced the co-evolution of paleolake environments and organisms, causing significant differences in the source, accumulation, and preservation of organic matter during different phases, along with notable variations in organic carbon burial. We propose that organic carbon burial in the large paleolakes of the Bohai Bay Basin was a response to global and regional climate changes. These findings highlight the climatic sensitivity of lacustrine organic carbon burial, which may in turn play a key role in climate regulation. This study enhances our understanding of lacustrine carbon burial potential, patterns, and mechanisms, as well as the role of lakes in the global carbon cycle.