Differential salt-related structural deformation in the Eastern segment of the Qiulitage fold and thrust belt, Kuqa Foreland Basin: Evidences from seismic interpretation and numerical simulation analysis

Abstract

The dymatic mechanisms of salt-related structural deformation in the foreland fold-and-thrust belts have been paid more and more attention for significance in hydrocarbon exploration. The Qiulitage Fold-and-Thrust Belt (QFTB) in the frontal Kuqa Foreland Basin(KFB) has been regarded as an important study area for its complicated deformation features and potential oil and gas resources. In the eastern QFTB, sub-salt fault-bend folds show a clear transition from a single row of basement-involved thrust belts in the east to a multi-row caprock detachment thrust belt in the west.This study uses discrete element numerical simulations, based on a geological model derived from seismic data, to validate and improve the model's reliability. This research investigates the factors controlling differential structural deformation in the QFTB. These simulations are mainly explored the impact of Jurassic-Triassic detachment layer thickness, stratal dip angle, and the role of dual salt layers. The results indicate that the detachment layer enhances the décollement thrusting effect, with thicker detachment layers leading to stronger décollement thrusting. If the detachment layer is too thin to support décollement thrusting, basement-involved faults develop instead. When the lower detachment layer is less than 800 m thick, two sets of basement-involved faults form, resulting in shorter thrust distances. Conversely, when this layer exceeds 800 m, only one set of basement-involved faults forms, along with two sets of caprock detachment faults at the frontal thrust belt, resulting in relatively greater thrust distances. Stratal dip angle is equivalent to the ancient topography which can restrain the formation and development of the thrust system, with steeper detachment layer angles reducing thrust distance and causing salt accumulation. In a dual-salt layer environment, the compaction of the overlying strata is weakened, which in turn enhances the décollement thrusting effect. The double salt layers of the Jidike and Kumugelemu Formations promote the development of multiple thrust fault arrays and enlarge the scale of frontal secondary anticlines. Therefore, the segmented differential deformation in the QFTB is influenced by the interplay of deep geological structures, detachment layers, and salt layer development. This study integrates seismic interpretation and numerical simulation to investigate the genetic mechanisms of segmented deformation in the QFTB, providing valuable insights and solid evidence for structural interpretation and hydrocarbon exploration in analogous salt-detachment systems.