A structural interpretation model of the Kekeya segment in the piedmont thrust belt of the West Kunlun Mountains and its petroleum geological implications

Résumé fourni par la source

The southwestern margin of the transition zone between the Southwestern Tarim Depression and West Kunlun Mountains, known as the West Kunlun Piedmont Thrust Belt, exhibits intense compressional deformation. As a critical oil and gas exploration area in the Southwestern Tarim Depression, the internal architecture and structural styles of this piedmont thrust belt have long been key geological challenges hindering exploration progress. This study establishes a structural interpretation model for the Kekeya segment of this belt on the basis of integrated analysis of surface geological outcrop observations, seismic data, and continuous electromagnetic profile (CEMP) data, and analyzes its structural evolution process and petroleum geological significance. It is proposed that the Kekeya segment can be interpreted as a piedmont thrust wedge structure bounded by a basin–mountain boundary fault (rear-edge fault) and a low-angle detachment fault in the middle-upper crust (basal fault). The internal thrust wedge is composed of 4–5 major reverse faults and the wedge-shaped fault blocks they divide, superimposed in varying configurations, with additional faults of different scales and characteristics developed within. Most major faults exhibit multiphase activity of different natures, and the superposition of multiple structural deformations results in complex structural styles and layered, zonal, and segmented variations within the thrust wedge. From the Tiekelik Uplift in the northern edge of the West Kunlun Mountains to the axial part of the Southwestern Tarim Depression, the thrust belt sequentially manifests as a basin-margin thrust uplift zone, basement-involved thrust zone, and cover detachment thrust-fold zone, reflecting a gradual weakening of compressional deformation intensity and shallowing of deformation-involved strata. This study further suggests that the thrust wedge underwent multiple “opening–closing” structural evolution cycles from the Nanhua period–Early Paleozoic (Caledonian), late Paleozoic–Triassic (Hercynian–Indosinian), and Jurassic onward (Yanshanian–Himalayan), with the superposition of multiphase deformation leading to complex internal structural styles. Notably, major faults within the basement-involved thrust zone often exhibit multiphase kinematic characteristics, serving as boundary faults for both Carboniferous–Permian rifted basins and later thrust anticlines and fault blocks. These fault zones are favorable for the formation of self-sourced Carboniferous–Permian hydrocarbon reservoirs, representing a significant target for current oil and gas exploration.

Ce résumé expose les affirmations des auteurs. BNTIC ne l’interprète pas comme une validation indépendante des résultats.