Geophysical and Landsat lineament mapping — An approach illustrated from west-central and south India

Abstract

Regional gravity and magnetic-intensity anomaly maps of India show linear anomaly zones well correlated with the tectonic framework of the sub-continent. These linear zones, in general, correspond with those obtained from Landsat data and theoretically computed global shear patterns of Vening Meinesz. Some of them exhibit continuity in time and space, with occasional rejuvenative activity. Such correlations enable picking up geologically more significant lineaments which may originate at great depths. A combined analysis of ground gravity and magnetic data with Landsat linears and surface-cum-satellite gravity data in India has enabled identification of two mega-lineaments, one trending northwesterly, the west-central India mega-lineament, and the other trending east-northeasterly, the Tapi-Narmada-Son mega-lineament. Apart from the linear zones correlated with surface geology, the geophysical- and Landsat data show others also. Three such features extend northwesterly from the east coast (16° N) to the west coast towards Bombay (28° N). In their northwestern parts they fall over the Deccan Traps paralleling major drainage lines of the region — the Godavari, Bhima and Krishna rivers. The discordance of these linear zones with the predominant north-northwesterly structural strike of the Dharwar in south India and the postulate of cymatogenic upwarping of south India is suggestive of a genetic relationship between the linears and the cymatogenic warping, Deccan lava eruption, and density variations in the mantle. Such correlations between geophysical- and Landsat lineaments, tectonics, theoretical shear patterns and geomorphic evolution of landforms can help in testing existing hypotheses of the tectonic evolution of major features of the earth's crust.