Nature of continental crust along the Narmada—Son Lineament inferred from gravity and deep seismic sounding data

Abstract

The Narmada-Son Lineament (NSL) is a very prominent feature on the tectonic map of India and divides the Indian peninsula into two parts, the northern part characterised by lower elevations and more positive Bouguer gravity anomalies as compared to the southern part. The lineament is characterised by a gravity high practically all along its length. Four published deep seismic sounding (DSS) profiles across the NSL give vital information concerning its origin. An analysis of the Bouguer gravity field along these profiles has been carried out using all available geological and velocity/density information. The analysis reveals that the areas immediately south of the NSL are characterised by higher-density crust in comparison to the areas north of it. This increase in density could have taken place during Mesozoic to Tertiary times when major tectonic/volcanic activity took place over peninsular India. The presence of deep seated faults, sediments and anomalous crust shows that the lineament has some characteristics of a rift valley.