The eastern continental margin of India is aligned NE-SW due to the trend of the Eastern Ghat orographic belt in the northern part and almost north-south in the southern part. It is of passive type, the origin of which can be traced back to its separation from Antarctica around 127 Ma ago. The 2493 km-long shoreline of eastern India is fringed with a continental shelf with a variable width of 35 km off Tamil Nadu to 60 km off north Andhra Pradesh and 120 km around Digha. The shelf has a gentle slope in the northern sector and is moderately steep in the south. Net longshore sediment transport along the east coast is from south to north. The east continental shelf of India is characterized by four major deltas; the Ganges, Mahanadi, Krishna-Godavari and Cauvery. The interdeltaic shelves are generally sediment starved. The inner shelf is silty to clayey silt and sandy, whereas the outer shelf has carbonate sands with coral debris and shell fragments. The outer shelf is characterized by carbonate sands, lime mud and ooids in the north Andhra Pradesh sector off the Kakinada-Kalingapatnam sector. The outer shelf off Chennai-Mahabalipuram, Nagapattinam -Point Calimere is characterized by a thin veneer of authigenic sediment represented by verdine, glaucony and phosphatic sediment. In Tamil Nadu, the region between 108N and 12830 0 N is characterized by two megalineaments and associated tectonics, suggesting that the area is tectonically active.The 14 C dating of relict corals, from water depths of 120 m, off Karaikal indicates an age of 18 390 + 210 years BP, establishing the low sea-level position of the Last Glacial Maximum. The large volume of sediment input from the deltaic system of two major drainages, Krishna and Godavari, has a significant influence on the morphology and sedimentation of the continental shelf. The influence of glacioeustasy is noticeable in outer shelf sediments along almost the entire length of the shelf. † Deceased

The west coast of India, extending from Sir Creek in the north to Kanyakumari in the south, is a trailing passive margin that bears the imprint of generally shore-parallel and less common orthogonal structural elements. The geomorphology of the marginal part of western India, mostly controlled by the three principal structural trends of NNW–SSE Dharwar, NE–SW Aravalli orogenies and west–east Narmada graben, displays a straight coastline. The coastal ocean current operates from April to October and the net sediment transport is from north to south with the longshore current. The continental shelf width varies from 345 km off Daman in the north to 120 km off Goa and tapers to 60 km off Kochi in the south. The western continental shelf of India has an area of about 310 000 km2, and is divided into an inner shelf with modern clayey silt and silty clay sediments with high organic matter and low carbonate content, and an outer shelf having relict carbonate sediments, coarse sands with low organic matter and high carbonates. The mid-shelf is rather uneven topographically, and the outer shelf is commonly interrupted by shore-parallel ridges and reefs with a relief of 2–18 m. Phosphatic limestone micronodules occur in the outer shelf.

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