Chapter 16 The continental shelf of eastern India

Abstract

Abstract 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 10°N and 12°30′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 glacio-eustasy is noticeable in outer shelf sediments along almost the entire length of the shelf.