LANDSAT Thematic Mapper Data Applied to Structural Studies of the Eastern Ghat Granulite Terrane in Part of Andhra Pradesh

LANDSAT TM data have been used as an aid to studying the regional geology of the granulite terrane in the southern part of Eastern Ghats. The technique in conjunction with regional traverses proved to be useful in identifying regional structural elements, such as shear zones, fold patterns of different scales and other lineament patterns, in poorly exposed and inaccessible areas. A major crustal scale ductile shear zone, designated as Sileru shear zone, with a dextral sense is highlighted and lies at the western margin of the high grade terrane. The other shear zones within the granulite terrane, characterised by migmatitic gneisses and typical L-S mylonitic fabrics, are associated with transpressional tectonics. Fold patterns varying from tight upright isoclinal folds to refolded large scale recumbent folds, along with complex fold interference structures on mesoscopic to regional scale are described. The interpretation of LANDSAT data, followed by limited ground based traverses from Sileru to Visakhapatnam in Visakhapatnam district and from Chinturu to Eleswaram in East Godavari district are the constraints in precisely defining the regional structures and understanding the tectonic processes that fashioned shear zones and fold patterns in granulite terranes. A fold thrust thin-skinned tectonic model involving two tectonothermal events for the study area is envisaged.