Evolution of Southern Part of Indian East Coast Basins

Abstract

Regional study of subsurface data of sedimentary basins on the East coast of India to the south of 18° North latitude has led to an appreciation of tectonic styles and sedimentation histories of Krishna-Godavari, Pennar Palar, and Cauvery basins. Tectonics and evolutionary history is understood through three distinct episodes of evolution viz. 'lnterier Fracture', 'Pull Apart' and 'Shelf Sag/Tilt'. These episodes being a part of structural development of passive margins are complicated by phase overlap and shear tcetonics associated with differential movements during the long flight of the Indian sub-plate. The block movements along the major planes of weakness has generated different sub-basins separated by ridges both in Krishna-Godavari and Cauvery basins.

These sedimentary basins have 3-8 kms, of sediments. Punctuated with major unconformities they range in age from Proterozoic to Recent. In the outcrops present on the western margin of the basins the stratigraphic record is less complete when compared with subsurface stratigraphic succession. The presence of subsurface Gondwana sediments has been confirmed into Krishna-Godavari basin. The metasediments present above basement both in Krishna-Godavariand the Pennar basins are suggested to be equivalents of Pakhals/Cuddapahs.