Milankovitch cycles and high-frequency sequences of the Middle Permian Maokou Formation in Sichuan Basin

The Maokou Formation was formed during the middle to late period of the Middle Permian in the Sichuan Basin. By analysing the outcrop lithology of the Maokou Formation and comparing the changes in the carbon and oxygen isotope levels to the sequence characteristics of the Changjianggou outcrop in Shangsi, Guangyuan area, Sichuan, we divided the Maokou Formation into two 3rd-order type II sequences that can be tracked over the entire basin. The major controlling factors of these two sequences were analysed. To establish the high-frequency sequence division, we employed a digital filtering process to eliminate the effect of minor factors and only retain the information associated with the major controlling factors. The Maokou Formation developed approximately 154th-order sequences within approximately 6.11 Ma. By dividing the high-frequency sequences from the superimposed curve containing tectonic setting and long eccentricity data, we believe that the high-frequency interfaces are much closer to the actual dev