Reconstruction of the Cretaceous tectonic evolution of the eastern margin of the Tibetan Plateau is of great significance to understanding the formation and early evolution of the Tibetan Plateau. The thick late Mesozoic sedimentary sequence in the Western Sichuan Basin may record the evolution of the basin itself and the tectonic uplift history of the eastern margin of the Tibetan Plateau during the Cretaceous period. Here we provide new multi-proxy provenance data from conglomerate clast populations, sandstone petrography, heavy mineral assemblages, U-Pb dating of detrital zircon, paleocurrent data, and detrital garnet geochemistry from the Cretaceous clastic units in the southwest corner of Sichuan Basin. Our analysis reveals two distinct changes in sediment provenance recorded in the Cretaceous strata at the southwest corner of the Sichuan Basin. The first significant change of detrital provenance was identified in the mid-Cretaceous Jiaguan Formation. Metamorphic rocks and volcanic rocks clast, as well as feldspar and mica, increased significantly, a heavy mineral assemblage dominated by hematite–limonite and ilmenite with high ATi and RuZi and low ZTR values, predominantly type Bi garnet and mostly 164 Ma, 207 Ma, 440 Ma, 780 Ma–824 Ma, and 1840 Ma detrital zircon ages, interpreted to be sourced from the Songpan-Ganzi fold belt and Longmenshan orogenic belt. The second shift, in the Guankou Formation, is marked by a low compositional maturity, a distinct increase in fossiliferous carbonate clasts and high GZi index with type Bii garnet, and Triassic zircon ages, indicating the exhumation of Longmenshan orogenic belt during the late Cretaceous. These data collectively indicate that the significant surface uplift and rapid denudation of the eastern margin of the Tibetan Plateau were probably initiated in the mid-Cretaceous (∼120 Ma). In conclusion, a detailed hands-on provenance analysis of the clastic sedimentary sequences in the southwest corner of the Sichuan Basin enabled us to determine catchment areas and shifts hitherto unstudied, thus contributing to the exhumation history of the eastern margin of the Tibetan Plateau.

Deep shale reservoirs in the southern Sichuan Basin have undergone strong tectonic reworking, producing pore structure heterogeneity that affects reservoir quality and hydrocarbon preservation. In this study, shales with different deformation intensities are analyzed using field emission scanning electron microscopy (FE-SEM), low-pressure nitrogen gas adsorption (LP-N₂GA) and fractal analysis to investigate tectonic control on pore–fracture evolution and fractal characteristics. Weakly deformed shales are dominated by intraparticle pores and regular organic matter (OM) pores, whereas strongly deformed shales develop abundant interparticle pores and microfractures along brittle mineral boundaries with irregular, preferentially oriented OM pores. The large-pore fractal dimension (D₂) consistently exceeds the small-pore fractal dimension (D₁) in both wells, indicating greater adsorption-related structural complexity of larger pores. Strongly deformed shales exhibit a higher mean box-counting fractal dimension (D_b), indicating greater geometric complexity of OM pores. Supervised machine-learning image analysis reveals pore-size differentiation associated with deformation intensity. Intense tectonic compression may cause some 80–350 nm pores to contract, whereas localized pressure release and shear-induced dilation may promote pore expansion and fracture propagation, producing pronounced multiscale heterogeneity. Overall, stable overpressure preserves the primary pore system in weakly deformed zones, whereas compressive deformation and localized pressure release drive the coupled evolution of pore structure and fractal characteristics, with potential implications for shale gas storage and preservation.

Faults are critical to the preservation or destruction of shale gas concentration. The Lower Silurian Longmaxi Formation in the southern Sichuan Basin hosts relatively developed faults, which pose a huge challenge to the exploration and exploitation of shale gas. An urgent need to quickly determine the widths of fault damage zones (FDZs) arises in locating horizontal shale gas wells. In this study, FDZs were estimated using the fault likelihood. The results are as follows: (1) It is rational to constrain the FDZ width using a fault likelihood greater than 0.2. The six major NEE-trending faults in the Fuji syncline of the Luzhou block have complex structures and varying FDZ widths from about 240–1220 m. (2) The degree of influence of FDZs is negatively correlated with their distance from the faults. In other words, a greater distance from a fault is associated with a weaker influence and a smaller fault likelihood. (3) Based on the ratio of the fault throw to the FDZ width, we propose that the width of seismic-scale fault damages can be directly constrained using a ratio value of 3.5. This method is fast and accurate and can provide support for the evaluation of the shale gas preservation conditions and well placement in the Longmaxi Formation of the southern Sichuan Basin.