Orbital- and millennial-scale climate changes in terrestrial Early Cretaceous sedimentary strata from the International Continental Scientific Drilling Program of the Songliao Basin

The International Continental Scientific Drilling Program of the Songliao Basin has obtained continuous cores and abundant well logs from the Lower Cretaceous Shahezi Formation. This provides a valuable archive for understanding terrestrial paleoenvironmental and paleoclimatic changes during the Early Cretaceous. Based on lithological data and well logs, we conducted a study of paleoclimatic cycles within the Shahezi Formation. The results indicate that lithological curves and various well logs from the Shahezi Formation record orbital-scale climatic cycles. Spectral analysis of the tuned lithological curves reveals the millennial-scale cycles in the lower part of the Shahezi Formation. The results of filtering the tuned lithological curves show that the extracted eccentricity and precession curves exhibit good consistency with the amplitude variations of the millennial-scale cycles. This may suggest that millennial-scale climate variability recorded in the Shahezi Formation is driven or modulated by orbital-scale climatic forcing. This study is helpful for understanding the response of terrestrial environment to climate change in Early Cretaceous.