Record of Cenozoic climatic events from a paleolake in eastern China: Astrochronology and isotopic stratigraphy perspectives

The terrestrial sedimentary response to Cenozoic climate transitions has been extensively documented. However, challenges persist in constructing high-precision astronomical time scales for lacustrine basins, reconstructing long-term hydrological fluctuations, and continuously identifying climate events. Here, we analyze natural gamma-ray series from Well QC2 in the Dongpu Depression, Bohai Bay Basin, eastern China, to construct a long-term astronomical time scale spanning 52.29−22.37 Ma (±0.57 m.y.). Combined with δ13Corg and total organic carbon datasets, as well as sedimentary noise modeling (dynamic noise tomography, DYNOT, and the ρ1 red-noise parameter), we decode orbital-scale climatic perturbations and their driving mechanisms on lake-level dynamics. Our results document key Cenozoic climatic events, including the Early Eocene Climatic Optimum (ca. 50−49 Ma), the Late Lutetian Thermal Maximum (ca. 41.52 Ma), the Middle Eocene Climatic Optimum (ca. 40 Ma), the Priabonian Oxygen Isotope Maximum (ca. 37 Ma), and the Eocene−Oligocene Transition (ca. 33.9 Ma). The δ13Corg excursions, gamma-ray series variations, and total organic carbon fluctuations exhibit synchronicity with global marine δ13C and δ18O variations, underscoring the sensitivity of lake systems to global carbon cycle perturbations. Sedimentary noise analysis further identifies 2.4 m.y. and 1.2 m.y. astronomical cycles as dominant controls on lake-level oscillations. The 2.4 m.y. eccentricity cycle, acting in concert with global cryosphere evolution, drove abrupt lake-level declines during the Eocene−Oligocene Transition and Oligocene-2 events, whereas the 1.2 m.y. obliquity cycle primarily governed organic carbon burial efficiency by modulating regional precipitation-evaporation budgets. This work establishes a high-resolution chronostratigraphic framework for terrestrial responses to global climate transitions and elucidates how astronomical forcing regulates regional carbon cycling via hydrological pathways. Furthermore, it bridges a critical resolution gap in terrestrial−marine climate coupling studies.