Delhi-Hardwar Ridge and surrounding basement structure - Some inferences from deep resistivity sounding measurements

Abstract

The hitherto unknown lateral extension of the concealed Delhi-Hardwar Ridge (DHR) towards the east in the Palwal sub-basin of India is inferred from deep resistivity sounding measurements. The resistivity of the ridge is found to be more than 3000 Ohm.m, which is distinct in contrast to the sediment and basement resistivity. The depth of the ridge is estimated to be of the order of 600-800 m below ground level. Analysis of resistivity data across the ridge clearly shows that the basement dips towards the ridge and several depressions within the basement are not uncommon. Further, a significant lateral variation in resistivity of Neogene sediments in and around the DHR indicates post-depositional tectonic activity within the sub-basin. Basement depths estimated compare well with the interpreted depths from aeromagnetic data.