Obliquity forcing of lake-level changes and organic carbon burial during the Late Paleozoic Ice Age

The linkages between the astronomical forcing of sea-level oscillations, the environment, and climate change during the Late Paleozoic Ice Age (LPIA) add to our understanding of the complicated mechanisms and patterns of current global sea-level change, climate transition, and biological evolution. However, due to the complexity and internal nonlinearity of the Earth's climate system, the million-year-scale oceanic and continental moisture transport patterns and carbon cycle processes during icehouse states are still controversial. Here, we utilize high-resolution gamma ray (GR), density (DEN) logs and total organic carbon (TOC) datasets to conduct a study on the cyclostratigraphy and organic carbon burial processes in the Lucaogou Formation of the Early Permian Junggar Basin in the Northern Hemisphere. An ∼4.2 Myr high-resolution astronomical time scale is developed by astronomical tuning of DEN log and TOC series to the stable 405-kyr long-eccentricity cycles. A comparative study of the sedimentary noise model and the SediRate-Fischer (SR-Fischer) plot finds similar patterns of lake-level changes for the first time, further demonstrating the utility and robustness of the sedimentary noise model and the SR-Fischer plot in tracking water-level variations. The antiphase correlation of sedimentary noise curve with the obliquity modulation and relative sea-level cycles demonstrates that the changes in land-ocean water exchange associated with variations in poleward flux of moisture dominated by s₄-s₃ obliquity amplitude modulation (AM) cycles may be a major driver for regulating inland lake levels in the Northern Hemisphere during the Late Paleozoic Ice Age. Additionally, we find a robust cyclicity of ∼170 kyr in the TOC series, which is modulated by the combined s₄-s₃ and s₃-s₆ astronomical signals and is nonlinearly amplified by internal climate responses of the carbon cycle under varying climate conditions. Our results strengthen knowledge of the connection of Myr-scale sea- and lake-level variations to astronomically induced climate change during the Late Paleozoic Ice Age and further elucidate the nonlinear climate feedback of the carbon cycle under obliquity forcing.