Sub-basalt imaging from gravity studies over Deccan volcanic province of Central India

Abstract

Large part of the northwest and central India is covered with Deccan volcanic of Cretaceous origin. Presence of thick sequence of Mesozoic sediments underneath the volcanic cover has opened a new frontier for hydrocarbon exploration in India. Recently, detailed gravity measurements were carried out over the Deccan Syneclise of central India as a part of integrated geophysical studies for the delineation of subtrappen Mesozoic sediments. Bouguer anomaly map of the region depicts number of significant short wavelength anomalies due to shallow sources superposed on long wavelength regional anomalies due to deep-seated sources. Important among them are (i) an E-W trending broad relative gravity high associated with the Satpura mountains belt indicating presence of high density magmatic material at the deeper level (ii) a large wavelength regional gravity low in the southern part bears an inverse correlation with topography of Ajanta hills indicating mass deficiency beneath the excess topography load due to isostatic compensation (iii) short wavelength nearly E-W trending gravity low suggest the presence sediments below the volcanic cover. The residual gravity field obtained using frequency domain filtering reveals number of linear positive anomalies due to basement upwarp apart from short wavelength negative anomalies aligned in E-W direction probably due to sediments. Quantitative modeling of residual gravity field constrained by other geophysical information has brought out prominent subtrappean Mesozoic sub-basins along the Tapti rift. It is observed that thickness of sediments increases towards the east reaching to a maximum of about 2.0 Km. It is therefore inferred that the Deccan Syneclise region of central India has large potential for hydrocarbon exploration.