Basement fault control on the extensional process of a basin: A case study from the Cambrian-Silurian of the Sichuan Basin, South-west China

The Sichuan Basin, located on the eastern margin of the Tibetan Plateau, is an intracontinental basin that developed in the Yangtze Block. The Cambrian-Silurian strata in this basin have enormous exploration potential in terms of natural gas, but their structural evolution during the Cambrian-Silurian remains controversial. Based on wells, seismic profiles, aeromagnetic data, and previous research results, this study investigated the structures related to the Leshan-Longnvsi palaeo-uplift and the activity of the Cambrian-Silurian basement faults, revealing the activity of the extensional process during the Cambrian-Silurian. The results of this study were as follows: (1) the flattening of the bottom of the Permian strata in seismic profiles located in the Leshan-Longnvsi palaeo-uplift revealed a large number of normal faults, grabens, and horsts in the Cambrian-Silurian strata, indicating that the Leshan-Longnvsi palaeo-uplift was an extensional structure during the Cambrian-Silurian period; (2) balanced cross-sections and strata isopach maps showed that all seven basement faults in the basin were normal faults during the Cambrian-Silurian; (3) Sichuan Basin was in an extensional setting during the Cambrian-Silurian; (4) seven basement faults controlled the extensional process during the Cambrian-Silurian in the Sichuan Basin.