Enhanced organic carbon burial in the Songliao paleo-lake of northeastern China facilitated Late Cretaceous global cooling

Organic carbon (OC) burial represents a major long-term sink in the global carbon cycle; however, the role of continental lakes in regulating the deep-time carbon cycle and climate remains poorly constrained. The Songliao Basin in northeastern China developed into one of the world’s largest lake systems during the Late Cretaceous, coinciding with a pronounced global cooling between ca. 92 Ma and 84 Ma. To evaluate its contribution to the carbon cycle, we compiled 1988 total organic carbon measurements from 120 drill cores and, in combination with high-resolution chronostratigraphy, reconstructed the history of OC burial over an ∼8 m.y. interval. Our results show that burial fluxes increased markedly from ∼3.6 GtC Myr−1 in the Quantou Formation to 124.3−251.5 GtC Myr−1 in the overlying Qingshankou-Nenjiang formations. These fluxes account for ∼33%−68% of the global increase in OC burial during this interval, and corresponding pCO2 sequestration rates peaked at 325.81 ppm Myr−1, indicating that the Songliao paleo-lake functioned as an exceptionally efficient carbon sink. This enhanced burial was facilitated by subsidence-driven lake expansion, nutrient inputs associated with volcanic activity and recurrent marine incursions, which together promoted water-column stratification, bottom-water anoxia, elevated primary productivity, and efficient organic matter preservation. While multiple processes likely contributed to Late Cretaceous cooling, the lack of clear changes in magmatic carbon input and silicate weathering suggests that enhanced OC burial in the Songliao paleo-lake might have been an important additional driver. These findings provide new insights into greenhouse climate cooling and underscore the need to incorporate lacustrine carbon sinks into reconstructions of the deep-time carbon cycle.