UPPER CRUSTAL STRUCTURE IN THE TORNI-PURNAD REGION, CENTRAL INDIA USING MAGNETOTELLURIC STUDIES

Magnetotelluric studies were conducted over a 100 km long NS profile i n the Satpura range and Tapti basin. Data were collected at 18 station s in this region with an interstation spacing of 3-10 km. The geoelect ric substructure was obtained using a two dimensional modelling techni que and has indicated the presence of Deccan traps and Gondwana sedime nts overlying a rather complex granitic basement. Two distinct layers of Deccan basalts were delineated with a total thickness varying from 2000 m in the central part to about 300-1000 m on either sides of this NS trending profile. The thickness of the Gondwana sediments below th e traps was observed to vary rather strongly in the range, 300-2000 m. Two vertical conductive zones were delineated corresponding to the Kh andwa lineament and the Burhanpur tear but the sensitivity studies ind icated a large degree of nonuniquness associated regarding the shape a nd vertical extent of these conductors. An interesting finding of thes e studies is the presence of a prism shaped body in the central part o f the survey profile in the Satpura horst region at depths between 3.5 and 14 km with a resistivity of 20 ohm-m. The body had a lateral exte nt of 8 km at the top and 40 km at the bottom in the NS direction. Thi s observation is discussed along with the other geophysical results in the Satpura and Tapti regions.