Continuous extensional uplift controls the Silurian structural evolution of the Sichuan Basin, southwest China

Abstract

The Silurian strata in the Sichuan Basin hold significant exploration potential for shale gas, yet their interrelationships require further investigation. Utilising well data, seismic profiles and existing research, this study examines the structural characteristics of the Sichuan Basin during the Silurian, unconformity distribution characteristics between the Silurian and Permian strata and the extent of Silurian stratum denudation. It then analyses the structural evolution of the basin during the Silurian. The findings of this study include the following: (1) the Leshan–Longnvsi palaeo-uplift expanded from both northwest to southeast and southwest to northeast during the Silurian, whereas the eastern and southern Sichuan depressions migrated south-eastwards. (2) Three angular unconformity areas developed around the Leshan–Longnvsi palaeo-uplift, with the unconformity between the Silurian and Permian strata representing a disconformity. The extent of denudation of the Silurian strata increased from the core of the Leshan–Longnvsi palaeo-uplift to its periphery and decreased around the three angular unconformities. (3) The continuous Leshan–Longnvsi palaeo-uplift controlled the structural evolution of the Sichuan Basin in an extensional dynamic setting during the Silurian. The tensile stress from the passive continental margin at the western edge of the South China Block gradually propagated into the block, affecting Sichuan Basin deposits and Leshan–Longnvsi palaeo-uplift development.