Basement Structure as Inferred from Geophysical Data Around Karaikudi, Tamil Nadu

Rocks of the sedimentary belt in the south-east coast of Peninsular India, popularly known as the Cauvery basin, have been deposited in basin like troughs on the basement. Because of the probable existence of favourable structures for oil and gas accumulations, the interest in this thick sedimentary sequence created among geoscientists has led to the collection of a lot of geological and geophysical data over this area.

This paper discusses the basement structure around Karaikudi, based on the results of electrical soundings taken along an eight kilometre long NW-SE profile nearly perpendicular to the regional geologic and structural trend. The available gravity and magnetic data of ONGC are also interpreted for corroboration. Results obtained from seismic studies of Geological Survey of India are also cited. From a synthesis of all the geophysical results, it appears that the Archaean basement exposed at Kunnakkudi becomes deeper successively through step-wise block faulting as one proceeds southeastwards, and reaches a maximum depth of one kilometre at Karaikudi, and then it rises up again further east in a similar fashion.