Gravity-Constrained Basin Geometry and Structural Segmentation of the Lampang Basin, Northern Thailand

The Lampang Basin is a Cenozoic rift basin in northern Thailand whose geometry remains poorly constrained because of limited subsurface data. This study applies integrated gravity analysis and 3D gravity inversion to characterize basin geometry, structural segmentation, and subsurface density distributions. Complete Bouguer anomaly data from 1488 gravity stations were analyzed using regional–residual separation, edge-detection filtering, spectral depth estimation, and 2D forward gravity modeling, constrained by geological mapping and available borehole and seismic data. The resulting geological and geophysical constraints were incorporated into 3D geometry and density inversions to construct the first basin-scale 3D gravity inversion model of the Lampang Basin. The results identify four structurally distinct, fault-controlled sub-basins, refining previous gravity-based interpretations of three principal sub-basins. The Western and Central Sub-basins trend predominantly NE–SW, whereas the Eastern Sub-basin is predominantly N–S oriented; the Northeastern Sub-basin has a less well-defined geometry but is bounded by structures supporting a broadly N–S alignment. The 3D inversion indicates a maximum preserved sediment thickness of ~2050 m, with the deepest depocenter within the Central Sub-basin, whereas the broadest depocenter occurs within the Eastern Sub-basin. Gravity anomalies and inversion-derived density distributions further indicate an association between contrasting pre-Cenozoic basement domains on basin segmentation and geometry, including accretionary complexes, volcanic arcs, and forearc basin successions of the Paleo-Tethys subduction margin. Integrated gravity modeling therefore provides regional constraints on the preserved geometry and structural segmentation of Cenozoic intermontane basins where direct subsurface information is spatially limited.