Stratigraphy and Tectonics of Sedimentary Basins on East Coast of Peninsular India

Abstract

The stratigraphy and tectonics of the Cauvery, Palar, and Godavari-Krishna basins, on the east coast of India, are considered on the basis of geologic, geophysical, and drilling data. The Cauvery basin was formed during Late Jurassic time by sagging of a part of the Indian shield, mainly along the dominant northeast-southwest basement trends. The basin consists of several depressions separated from each other by subsurface basement ridges aligned parallel or subparallel with the dominant basement trends. The sedimentation in the respective depressions was controlled by movements along these trends from the time of deposition of the Upper Gondwana beds. The depocenters, which were mainly open toward the west during Upper Gondwana deposition, shifted toward the east as a result of general basinal tilt at the beginning of the Tertiary. These movements were responsible for repeated transgressions and regressions, as is evidenced by lithofacies, biofacies, and thickness variations, as well as by sedimentation breaks. Outcrops in the Palar basin include thin Permian boulder beds and shales, a thick paralic Cretaceous sequence, and a thin continental Neogene succession. In the Godavari-Krishna basin the outcropping strata are Middle Jurassic to Lower Cretaceous paralic to shallow-marine sedimentary rocks and thin Trap Volcanics (basalts) overlain by a continental Neogene succession. A synthesis of geologic and geophysical data suggests that the tectonic and sedimentation patterns in the Palar and Godavari-Krishna basins are likely to be analogous to those of the Cauvery basin.