A Regional Tectonic Study of the Archaean Chitradurga Greenstone Belt, Karnataka, Based on Landsat Interpretation

The usefulness of LANDSAT images, both photographic and digitally processed, for reconnaissance structural studies is demonstrated. To a certain extent lithological discrimination is possible by these techniques, but stratigraphic interpretation is impossible other than in conjunction with detailed field studies of structure and way-up indications.

The tectonic boundary between the two cratonic sub-blocks of eastern and western Karnataka, identified by deep seismic sounding and recognised in a few places by field studies is delineated, as are other major faults. Major Archaean fold forms in the greenstone and gneisses are traced throughout the belt and interpreted as westward verging lobes of basement separated by synclinal cusps of greenstone belt cover, which have been disrupted and further deformed by smaller NNE-SSW folds and the major fault lineaments. Varying crustal level within this sequence of lobes and cusps is suggested to explain the variable state of deformation and metamorphism of greenstones in the craton, and N-S shear zones in the gneisses are thought to be expressions of shear strains beneath eroded cusps.