Delineation of geological contact at Chavutapally area Krishna district, A.P., by elelctrical resistivity soundings - An acid ground water exploration-a case study

Delineation of geological structures is a prerequisite in groundwater exploration in areas comprising of different rock formations. In the absence of surface manifestations, geophysical investigations play a significant role. A study was carried out at Chavutapally village, Krishna district, Andhra Pradesh where crystalline rocks are in contact with sedimentaries and both are masked by a soil cover of moderate thickness. Geo-electrical surveys viz., vertical electrical soundings (VES) were carried out to locate, accurately, the contact between Kamthi sandstones of lower gondwanas and metacrystalline rocks of precambrian group. The sharp resistivity contrast on either side of the contact suggests the presence of a pre-depositional fault plane in the area which is a potential water bearing horizon. Delineation of this contact in turn facilitated the selection of sites for borewells to augment rural water supply in the area. Further, these surveys were useful in determining the bedrock position and associated fractures.