Analysis and Modelling of Salt-related Deformation in the Western Sichuan Foreland Basin, China

Abstract

The Western Sichuan Foreland Basin (WSFB) in South China, a prolific hydrocarbon province, exhibits complex structural deformation influenced by Triassic salt tectonics. This paper integrates seismic data and well data to elucidate the role of Middle–Lower Triassic evaporite layers in shaping basin structures, focusing on Xinchang Tectonic Zone (XTZ). Salt layers facilitated decoupled deformation between supra- and sub-salt sequences, forming salt pillows and fault-related folds. Three distinct structural trends were identified in XTZ. Key findings reveal that salt thickness variations correlate with deformation styles: thicker salt promoted detachment folding, while thinner salt led to hard-linked fault systems. Sub-salt E–NE trending reverse faults formed horsetail terminations associated with the Pengzhou faults (PzF), deviating from the primary Longmenshan thrust belt (LmsTB) orientation. Structural evolution occurred in three stages: (1) Indosinian salt deposition and foreland basin initiation; (2) Yanshanian eastward propagation of thrust systems with salt-driven detachment folding; (3) Himalayan reactivation overprinting earlier structures with sub-NS trending folds. This work establishes a direct link between salt layers and structural traps, demonstrating how salt acted as a critical detachment layer during multi-stage compression. Results provide insights into the gas exploration of the Late Triassic Xujiahe Formation, emphasizing the importance of salt-influenced deformation in foreland basin systems.

Keywords

salt structure / fault / horsetail terminations / foreland basin / western Sichuan

RIGHTS & PERMISSIONS

2026 Geological Society of China