Formation Mechanisms and Trap-Controlling Effects of Non-Coaxial Structures Governed by Mudstone Detachments in the Zhongqiu–Dongqiu Section, Kuqa Depression: Evidence from Seismic Interpretation and Tectonic Physical Modeling

To address the challenges posed by complex Cretaceous(K) deep structural deformation and the poorly understood decoupling mechanism between deep and shallow structural layers in the foreland thrust belt of the Kuqa depression, Tarim Basin, this study integrates high-precision 3D seismic interpretation with balanced cross-section restoration techniques to systematically elucidate the controlling role of rheological heterogeneity within the Shushanhe Formation (K1s) mudstone on the stress–lithology–structure coupling mechanism. Our findings demonstrate that variations in thickness and rheological properties of the Shushanhe Formation mudstone govern the structural segmentation along the Zhongqiu–Dongqiu transect. In the Dongqiu area, an exceptionally thick and highly ductile mudstone layer induces principal stress deflection and horizontal shearing, effectively absorbing vertical strain transmitted from deep-seated tectonic wedges. This results in pronounced decoupling between deep and shallow strata, giving rise to broad, gentle anticlines and ramp-flat imbricate structures at depth. Conversely, in the Zhongqiu area, the mudstone thins significantly and becomes more brittle, increasing the friction coefficient and impeding vertical stress transmission. Consequently, near-vertical stacking occurs in the proximal compressional segment, leading to the development of high-angle thrust faults and strike-slip-modified fault-bend folds. This study clarifies the genetic mechanism of non-coaxial structures controlled by the mudstone detachment layer and confirms that the plastic flow of this layer not only enhances lateral sealing capacity but also acts as an effective rheological barrier, thereby preserving the deep overpressured hydrocarbon reservoirs in the Yageliemu Formation (K1y). These insights provide a robust theoretical foundation for shifting exploration strategies from shallow structural traps to deep, subtle lithologic–structural composite plays, offering critical guidance for sweet spot prediction in ultra-deep settings.