The coupling mechanism of climatic oscillations, tectonic activities, episodic geological forcings, and lacustrine chemical-physical-biological conditions in modulating organic carbon burial processes

Deep-time lacustrine organic carbon burial (OCB) provides a critical window for understanding global carbon cycling and climate change. However, its detailed processes and driving mechanisms require further exploration. Here, we reconstruct the OCB processes (OCBP) in the Zhanhua Depression—a representative saline rift lake basin in East Asia formed under greenhouse climatic conditions. We find that climatic oscillations, tectonic activities, and episodic geological forcings (e.g., marine transgressions and turbidity currents) significantly influence the lacustrine chemical-physical-biological conditions, which themselves exhibit complex internal interactions. These four factors collectively govern each component (source, production, consumption, burial, and preservation) of OCBP. The impact of a single factor on organic carbon enrichment in each component of OCBP varies—and may even exhibit both beneficial and detrimental effects within a single component. The outcome of OCBP is determined by the coupled effects of the above four factors (including the combination style of the factors, their relative strengths and weaknesses, and their positive and negative effects on organic carbon enrichment). This study identifies four distinct OCB mechanisms: marine transgression driven (42.47−41.72 Ma), lacustrine chemical-physical-biological conditions driven (41.72−41.52 Ma), warm-humid climate and intense tectonism driven (41.52−40.68 Ma), and turbidity current driven (40.68−40.20 Ma). High-frequency coupling variations among influencing factors drove shifts in lacustrine OCB mechanisms of minimal 0.2 m.y. scale.