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ABSTRACT: Evidence of Multiple Stretching and Episodic Subsidence of a Passive Continental Margin: Indian Examples

Abinash Agrawal

The western continental margin of India, south of the Narmada lineament, underwent two major phases of stretching and rapid tectonic subsidence, as seen in more than 30 deep offshore wells.

The initial phase of unloaded basement subsidence took place in the Paleocene, and was probably related to K/T rifting of India along this margin. At this time, the continental crust underwent some stretching leading to the formation of several north-south-trending depressions, namely the Vijayadurg, Surat-Panna, the Kori-Comorin, and on-land

Cambay graben, which provided a site for the rapid accumulation of hydrocarbon source rocks in the depressions.

The second phase of rapid basement subsidence along this margin occurred in the Early Miocene. Further stretching of the already blockfaulted crust caused the complete development of the westernmost Kori-Comorin depression, but the effect was less significant on the main shelf. The possibility of a heating event associated with the stretching, inducing maturation of hydrocarbons in the area, is under investigation.

Similar early Miocene tectonic subsidence also is seen along the peripheries of the Arabian Sea and the Bay of Bengal. This phase of tectonic movements was probably related to the locking of the Owen fracture zone, the 20-Ma plate reorganization in the Indian Ocean, and the renewed uplift of the Himalayas.

AAPG Search and Discovery Article #91003©1990 AAPG Annual Convention, San Francisco, California, June 3-6, 1990