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. This study provides new constraints on the dynamic setting of the Sichuan Basin during the Cambrian–Silurian using a fine interpretation of seismic profiles and strata thickness analysis. The facts that the Leshan–Longnvsi palaeo‐uplift was an extensional structure and basement faults were normal faults suggest that the Sichuan Basin was in an extensional setting during the Cambrian–Silurian. Seven basement faults controlled the extensional process during the Cambrian–Silurian in the Sichuan Basin.