The evolutionary process and controlling factors of multi-directional compressional tectonics south of the Weiyuan anticline, SW Sichuan Basin

Objective Under the influence of adjacent contractional orogenesis, multiple groups of structures with varying orientations have developed in the southwestern Sichuan Basin, exhibiting complex superimposed deformation characteristics. Clarifying the active stages and genesis mechanisms of different fault systems is crucial for understanding hydrocarbon migration pathways, trap formation, and reconstruction processes.

Methods Based on 3D seismic reflection data, this investigation selects the region south of the Weiyuan anticline as a case study to conduct detailed structural analysis. The dominant structural styles, evolutionary processes, and controlling factors in this area were then analyzed.

Results The results indicate that NEE– and NW–trending contractional faults and their associated folds are predominantly developed. Among these, the NEE–trending structure is influenced by detachment layers within the Cambrian, Silurian, and Triassic strata, primarily developing thin–skinned structures and displaying stratified deformation characteristics. The NW–trending structure is mainly controlled by detachment layers within the Silurian and Triassic strata. Integrated growth strata analysis and balanced structural restoration indicate that the NE–trending structure underwent four stages of tectonic shortening: Late Caledonian, Hercynian, Indosinian, and Yanshan–Himalayan periods, whereas the NW–trending structure primarily experienced three stages of deformation: Early– and Middle– Indosinian and Yanshan–Himalayan periods. Deformation related to the NEE–trending structures rapidly propagated to the pinch–out of the Lower Cambrian salt detachment layer during the early stage of tectonic deformation, resulting in the formation of the Ziliujing anticline. However, due to the weakening of late–stage compression, NW–directed propagation was significantly restricted. The NW–trending structure initiated later but, driven by continuous and intense tectonic activity, deformation progressively propagated toward the northeast direction.

Conclusions Consequently, the present–day complex superimposed deformation pattern in the study area is primarily governed by the spatial distribution of the detachment layers and the timing and magnitude of structural deformation in each direction.