Astrochronology of the Paleocene–Eocene Thermal Maximum on the East Tasman Plateau

Abstract

The Paleocene–Eocene Thermal Maximum (PETM) was a dramatic climatic event characterized by substantial perturbation of the carbon cycle and environmental crisis in the Cenozoic. Although astronomical forcing has been proposed as a mechanism of these changes, its precise influence on carbon cycle dynamics and climate feedbacks during the PETM remain insufficiently constrained. To address this gap, developing a high-resolution astronomical time scale is essential for accurately characterizing the climate response. Here, we established an astrochronology for the PETM based on statistical tuning, enhanced by a novel spectral analysis approach, using a sediment core from Ocean Drilling Program (ODP) Leg 189 Site 1172, located on the East Tasman Plateau in the high latitude of the Southern Hemisphere. Time series analysis of high-resolution X-ray fluorescence (XRF) scanning data for Fe and Ca from Hole 1172D reveals prominent eccentricity and obliquity signals, along with ∼170 kyr obliquity amplitude modulation cycles throughout the PETM. Our analysis indicates that the PETM interval spans approximately 8–9 precession cycles, with the onset of the carbon isotope excursion (CIE) occurring within half a precession cycle. Sedimentation rate estimates of ∼0.8–0.9 cm/kyr during the PETM further constrain organic carbon mass accumulation rates, thereby informing interpretations of carbon cycle dynamics during this interval. Overall, the astronomical time scale established at ODP Site 1172 provides critical constraints on orbital forcing, sedimentation rate variations, and carbon cycle feedbacks during the PETM.