Trap thickness and the subtrappean structures related to mode of eruption in the Deccan Plateau of India : results from magnetotellurics

Deccan trap thickness is an important parameter in understanding the eruption process of flood basalts (65 My). A magnetotelluric study was carried out in Deccan Volcanic Province (DVP) of the Indian Peninsular shield during 1998–1999. Modeling results clearly revealed variations both in the thickness of the Deccan traps and in their resistivity from the west coast to the eastern boundary of DVP. The thickness of the traps in DVP decreases from about 1.8 km in the west to a few hundred meters (approx. 400 m) towards the east. The traps also exhibit considerable variation in resistivity, with higher resistivities (approx. 150–200 ohm-m) in the western half and lower resistivities (approx. 50–100 ohm-m) in the eastern half of DVP. Two significant fissure/fracture zones have been detected in DVP; these may have acted as conduits for the outpouring of Deccan lavas in addition to the primary structures along the west coast and the Narmada-Son lineament (NSL) zones.