Characteristics and evolution of the main strike-slip fault belts of the central Sichuan Basin, southwestern China, and associated structures

We identify the property and distribution of main strike-slip fault belts of central Sichuan Basin according to the characteristics of associated structures in the gypsum-salt rock layers of the Lower-Middle Triassic Jialingjiang and Leikoupo Formations, as well as the dislocation position, direction and distance of carbonate platform margins in the Upper Sinian Dengying Formation. We find that large amounts of NW-trending en echelon folds and faults with dense distribution and left order arrangement are developed in the gypsum-salt rock layers. These en echelon faults and folds form two types of structural association with the deep (subsalt) strike-slip faults: one type is mainly developed in the Moxi area, where the en echelon structures situate right above the deep strike-slip faults; and the other type, with the en echelon structures distributed between the two strike-slip fault belts, is mainly developed in the slope area north of Moxi. According to the two structural types and the dislocation positions of the carbonate platform margins in the Dengying Formation, six main strike-slip fault belts are recognized in the central Sichuan Basin. Under the constraint of basin evolutionary frame, and based on the quantitative analysis of a representative growth structure between the Moxi and Gaoshiti areas, evolution of strike-slip faults in the central Sichuan Basin is divided into three stages, i.e., stages of (1) right-lateral strike-slip fault activity in the Late Ordovician-Silurian, (2) no fault activity from the Late Paleozoic to Triassic, and (3) left-lateral strike-slip activity since the Middle Jurassic. The carbonate platform margins of the Upper Sinian Dengying Formation in the central Sichuan Basin exhibit a regular step-by-step eastward dislocation with a distance of 20-40 km, which can be used as an indirect evidence for Caledonian right-lateral strike-slip activities. The central Sichuan Basin is located at the stable back-area of frontal uplifts in the northern upper Yangtze and Xuefeng foreland basins in the Late Triassic; however, due to rapid uplifts and differential evolution processes of orogenic belts around the Sichuan Basin, the central Sichuan area undergo compressional transformation and uplift since the Middle Jurassic, which triggers the strike-slip activities in the basement faults and early strike-slip faults. © 2022 Science Frontiers editorial department. All rights reserved.