Astronomical Forcing of Paleolake-Level Fluctuations in the Eastern Ordos Basin Between the Late Carboniferous and Early Permian

Abstract

A precisely constrained and high-resolution geochronology will enhance our understanding of sedimentary evolution, tectonic influences and climatic variations, all of which contribute to hydrocarbon exploration. According to sedimentary analysis, the North China Craton is believed to have undergone a transition in its sedimentary environment from a marine to a terrestrial lacustrine–fluvial system during the Late Palaeozoic. However, the geochronology and driving forces associated with transgression and regression remain understudied. In this study, we employed a cyclostratigraphic method to analyse the gamma-ray logging data from a Late Palaeozoic sequence in the Y69 well in the eastern Ordos Basin. We established an astronomical time-scale for this sequence, spanning approximately 10.83 million years, from ~299.94 ± 0.32 Ma to ~289.11 ± 0.32 Ma, in order to provide a geochronological framework for the evolution of the Ordos Basin. Subsequently, we reconstructed paleolake-level variations by applying sedimentary noise modelling to the tuned gamma-ray series and conducted periodicity analysis to identify astronomical signals. Our results indicate that water-level fluctuations in the eastern Ordos Basin were modulated by ~1.2-Myr obliquity and ~ 2.4-Myr eccentricity cycles, suggesting long-term astronomical forcing on hydrological circulation. The in-phase correlation between the reconstructed water level and global sea level at ~1.2-Myr intervals suggests that sedimentation was controlled by oceanic systems through transgression/regression events before ~294 Ma. Conversely, the anti-phase correlation between the reconstructed water level and global sea level at the same interval indicates that sedimentation was influenced by terrestrial systems through aquifer depletion and recharge after ~294 Ma. This shift in the correlation between water levels and global sea levels reflects the transition from an oceanic to a terrestrial sedimentary environment. These findings provide a high-resolution geochronological framework for further investigations and offer new insights into hydrological circulation, improving our understanding of the driving mechanisms behind sedimentary evolution in the North China Craton during the Late Palaeozoic Ice Age.