Spatiotemporal evolution of lower-middle Triassic strata, Sichuan Basin, Southwestern China: Insights into the deformation mechanism of the Luzhou paleo-uplift and gas exploration

The Sichuan Basin experienced profound structural changes during the Triassic, generating debate regarding the deformation mechanism of the Luzhou paleo-uplift and complicating future gas exploration efforts. Understanding the spatiotemporal evolution of lower-middle Triassic strata is crucial for resolving these controversies. In this study, we integrated seismic interpretation, detailed stratigraphic contact delineation, and erosion amount calculations to reconstruct the spatiotemporal evolution of the lower-middle Triassic strata. This reconstruction enables a reassessment of the uplift's deformation mechanism and its impacts on gas migration and accumulation. First, the spatiotemporal evolution of the lower-middle Triassic strata indicates that the distribution pattern of its paleo-highs and -lows was established during the late Triassic and subsequently inherited by overlying younger strata. Second, significant structural relief observed in the middle-Triassic Leikoupo Formation indicates the initial development of the Luzhou paleo-uplift during the late Triassic, reflecting a contraction-related origin driven by regional stress transfer, detachment-controlled shortening, and gypsum-related deformation in eastern Sichuan. Finally, gas resources likely migrated vertically via fault systems that acted as conduits between source rocks and reservoirs. Therefore, gas exploration targets should be identified by considering the spatial interplay of gas generation capacity, paleo-high and -low distribution, and fault systems. Particularly, preserved flanks or adjacent highs of inherited paleo-uplifts are likely more favorable than strongly denuded uplift crests.