The effects of salt flow on the cross-section restoration of salt-bearing fold-and-thrust belts: An example from the Kuqa depression

Thrust sequence analysis using cross-section restoration is critical for understanding the evolution involved in folds and thrusts as well as kinematics, the distribution of strain, and hydrocarbon accumulation. However, the application of cross-section restoration is challenging in salt-bearing fold-and-thrust belts. Salt flow causes un-certainty and difficulty in quantifying the geometry because of salt mobility and poorly constrained deformation kinematics. In this paper, we first analyze the role of salt flow in the cross-section restoration of salt-bearing fold-and-thrust belts using a synthetic model. Then an applicable method has been systematically described to quantify the effect of salt flow on the cross-section restoration. The method is efficient in determining the sub-salt thrust sequence, whereas accurate fault throw can be restored when the history of salt flow is known. Two well-constrained seismic profiles in the western Kuqa salt-bearing fold-and-thrust belts are restored sequentially to analyze the evolutionary process of sub-salt faults. The results show that the sub-salt thrust system propagates forward in sequence in the Bozi segment and out of sequence in the Dabei segment. The differential evolution of the sub-salt thrust between the Bozi and Dabei segments forms an oblique transfer zone. This study shows that understanding salt flow is the key point for cross-section restoration in salt-bearing fold-and-thrust belts, and relationships between supra-salt deformations and sub-salt thrust can be built by clarifying the contribution of salt flow.