Astronomically calibrated integrated stratigraphy of the Induan Stage (Early Triassic) and significance for the Permian–Triassic mass extinction and aftermath

Accurately estimating the duration of the Induan Stage (Early Triassic) is crucial for understanding biotic recovery and the rate of environmental upheavals following the Permian–Triassic mass extinction. However, there is considerable uncertainty because astrochronological and radiometric dating approaches have given substantially different durations. In this study, we establish a comprehensive chronological framework for the Induan Stage by integrating astrochronology, magnetostratigraphy, radiometric dating, biostratigraphy, and chemostratigraphy. Marine sections in South China, at Xiejiacao, Chaohu, and Daxiakou, preserve continuous Lower Triassic deposits, providing a unique opportunity for integrated stratigraphic studies. By analyzing new gamma ray series from the Xiejiacao section and gamma ray series from the Chaohu and Daxiakou sections, we construct a composite 405 kyr eccentricity cycle-calibrated time scale for the Induan Stage. Our results estimate the Induan duration at 1.57 ± 0.2 Myr. By anchoring this timescale to the Permian–Triassic boundary (251.902 ± 0.024 Ma), we propose an age of 250.33 ± 0.2 Ma for the Induan–Olenekian boundary. The revised timescale reconciles previous discrepancies between astrochronological and radiometric dating, providing a robust foundation for improving global stratigraphic correlations and enhancing our understanding of key phenomena, including carbon cycle perturbations and environmental changes during the Induan. Moreover, it offers a new timeline for biotic recovery following the Permian–Triassic mass extinction and contributes to the ongoing refinement of the Geologic Time Scale.