Groundwater Exploration using Ground Magnetic Survey along the Contact of Crystalline and Sedimentary Rocks in Parts of Perambalur District, Tamil Nadu, India

This study delineates groundwater potential zones along the contact between the Tiruchirappalli Cretaceous formations and the Archaean crystalline basement using ground magnetic surveys. Magnetic susceptibility data were collected with a Proton Precession Magnetometer along six NW–SE profiles at 1 km station spacing and 5 km profile intervals, covering key locations in Perambalur district, Tamil Nadu. A total of 60 measurements were obtained, with magnetic intensity values ranging from 967 to 7 gammas and averaging 297 gammas. Higher values were recorded in crystalline rocks (967–300 gammas) and lower values in sedimentary rocks (300–7 gammas), enabling the delineation of the basement–sedimentary litho contacts. Data processing in Geosoft and ArcGIS produced total magnetic intensity, reduction-to-pole, directional filter, regional, and residual maps, which highlighted lithological contacts and fracture systems. NE–SW fractures correspond to lithological contacts, while NW–SE fractures represent neo-tectonic structural elements. Groundwater potential zones were identified using rank and weightage method which shows that the possible potential zones are along the litho contact and the intersection of NW-SE fractures with litho contacts. The findings confirm that magnetic surveys are an effective tool for locating groundwater-bearing structures in basement–sedimentary terrains.