SUBSURFACE GEOLOGICAL MODELING OF MISSA KESWAL AREA, POTWAR PLATEAU, UPPER INDUS BASIN, PAKISTAN

Salt tectonics have significantly influenced structural geometries in compressive regimes within many global foreland sedimentary fold and thrust belts. Often, surface structures do not accurately represent subsurface formations, complicating hydrocarbon exploration. The Salt Range and Potwar Plateau in Pakistan exemplify the impact of the basal low-density evaporites of the Precambrian Salt Range Formation on the overlying Cambrian to Holocene cover sequence and the compressive tectonics during the Himalayan Orogeny. This interaction has created multiple salt-cored anticlines in the Potwar Plateau, hosting significant hydrocarbon deposits.

2D seismic reflection and well data from the Missa Keswal area of the eastern Potwar Plateau show that Cambrian strata are directly overlain by Paleocene strata, with missing Permian to Cretaceous strata, indicating a major unconformity. Seismic data reveal normal faults in the basement and a northwest-dipping fore-thrust that steepens near the surface. Multiple southeast-dipping back-thrusts connect to the major fore-thrust, forming a subsurface pop-up anticlinal structure above the basement normal faults. The Ordovician to Carboniferous strata are absent across the Salt Range, Potwar Plateau, and the Indus Basin, with ongoing debates about the reasons.

The presence of northwest-dipping normal faults in the basement and the absence of Permian and Mesozoic strata suggest uplift of the eastern Salt Range and eastern Potwar Plateau during the Neo-Tethys opening in an elevated passive margin setting. The late Himalayan Orogeny’s compressive tectonics mobilized the thick, low-density evaporites of the Salt Range Formation, juxtaposing the entire Precambrian to Holocene strata of the Salt Range-Potwar Plateau against the Punjab Plain via a rupture along the Salt Range Thrust. The leading edges of basement normal faults likely facilitated the upward push of the evaporites, forming salt-cored, pop-up anticlines in the Potwar Plateau bounded by steep reverse faults. The presence of both foreland and hinterland verging high-angle reverse faults indicates significant crustal shortening and vertical thickening. So, structural modeling based on seismic reflection and borehole data provides a reliable method to know subsurface structures, helping as a guideline for similar salt tectonics-dominated basins globally.