The Magnetotelluric (MT) technique is a geophysical tool used to determine the electrical
conductivity distribution in the earth’s interior by using the surface measurements of the
naturally occurring electric and magnetic field variations (Vozoff, 1972). In the conventional
MT method, the time variations of the electric and magnetic fields are measured over a
wide
Magnetotelluric (MT) studies over the northern part of the Deccan flood basalts
have delineated a conductive layer comprising the Deccan basalts and the
pre-Trappean Bagh sediments. This layer is about 2.5 km thick on the western part
of the survey profile, whereas on the east its thickness is about 1.5 km. The individual
thicknesses of these formations could not be determined presumably because both
these layers have similar resistivities. A deep-seated thrust zone is delineated along
which the Bagh sediments are subducting eastwards. This, along with the strong
undulations in the top layer observed in the western part of the study area, is indicative
of the compressional tectonics that this region may have undergone prior to the
Deccan volcanic event. The Bagh sediments are known to have deposited during
the Cretaceous and thus the compressional forces leading to the thrust zone observed
here may have been active during the period between the Cretaceous and the Deccan
volcanism.
The Magnetotelluric (MT) technique is a geophysical tool used to determine the electrical
conductivity distribution in the earth’s interior by using the surface measurements of the
naturally occurring electric and magnetic field variations (Vozoff, 1972). In the conventional
MT method, the time variations of the electric and magnetic fields are measured over a
wide range of frequencies (1000-0.0001 Hz) along the magnetic NS and EW directions and
the frequency variations of the response functions (apparent resistivity and phase of impedance)
are obtained. The depth control comes through the skin depth Thus, the
high frequency waves penetrate only the shallow crust and the depth of penetration increases
with the decrease in the frequency of the incident electromagnetic wave.
The Deccan Volcanic Province (DVP) is one of the most important regions of the
continental flood basalts in the world. The Deccan Trap comprises a sequence of basalt
flows extruded through fissures in the crust from a large magma chamber during 65 Ma,
when the Western India got detached from the continental block of Seychelles (White and
McKenzie, 1989). The lavas occupy more than one million square kilometer in most parts
of Maharashtra, Central India and parts of Gujarat, Rajasthan, Karnataka and
Andhra Pradesh (Pascoe, 1973). The Deccan volcanic activity coincided with the decline
of dinosaurs and it is believed that the Reunion mantle plume was responsible for the lava
flows when Seychelles started breaking away from the Indian shield. The Narmada, Cambay
and the Panvel flexure have originated due to the activity of the Reunion plume.
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