Controls of Syntectonic Sedimentation on Vergent Thrust Wedge Development: Insights from the Sichuan Basin

oil and gas engineering

The Sichuan Basin, situated at the eastern margin of the Tibetan Plateau, serves as a key natural laboratory for examining tectonic-sedimentation feedbacks in foreland basins. Despite extensive documentation of its polyphase tectonic evolution and rich hydrocarbon systems, the mechanical influence of syntectonic sedimentation on vergent thrust wedge development remains insufficiently quantified. This study employs scaled sandbox analogue modeling, incorporating dual décollement horizons representative of the basin’s Triassic evaporitic and deeper shale detachments, to simulate unidirectional shortening under varying sediment supply conditions. Results show that syntectonic sedimentation significantly stabilizes the wedge by reducing the critical taper angle by ~54% and promotes frontal thrust propagation by 144% relative to sediment-deficient cases. An optimal sedimentation rate emerges that maximizes thrust advance while preserving wedge stability, also controlling fault spacing and fold wavelength. The experimental models replicate key structural features observed in seismic data, including imbricate thrust stacks, fault-propagation folds, and piggyback basins. These findings demonstrate that sediment loading is an active, first-order control on stress distribution, deformation front migration, and wedge geometry. This validated mechanical framework enhances predictive models for hydrocarbon trap formation and informs seismic hazard assessments in the Sichuan Basin and analogous sediment-rich foreland systems globally.

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