Eccentricity pacing of the Paleocene-Eocene Thermal Maximum: Multi-section astrochronology and statistical insights in China

The Paleocene-Eocene Thermal Maximum (PETM; ∼56 Ma) is marked by a significant negative carbon isotope excursion (CIE) and represents an intense global warming over a geologically brief time. A high-resolution chronologic framework is essential for understanding the tempo and triggers of carbon releases during the PETM. In this study, we constructed independent astrochronologic frameworks for the PETM using three high-resolution proxy records from the Fushun, Nanyang, and Tarim basins in China. By integrating statistical methods, including TimeOpt and Bayesian statistics, we identified statistically significant orbital signals and assessed age uncertainties. Our results indicate a synchronized marine and terrestrial carbon cycle perturbation during the PETM. The main body of the CIE lasted ∼100 kyr, with the onset ranging from ∼5 to 20 kyr. The spectral power of orbital eccentricity increased near the PETM onset, suggesting that astronomical forcing may have triggered the PETM. Additionally, two smaller carbon isotope excursions were identified before and after the PETM onset in some records, potentially coinciding with ∼100 kyr short eccentricity maxima, further supporting the eccentricity pacing of carbon cycles during this crucial climatic transition.