Chapter 16 The continental shelf of eastern India

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 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

Structure and tectonics of the continental margins of India and the adjacent deep ocean basins: current status of knowledge and some unresolved problems

“…The eastern continental shelf of India (Figure 2) trends in a NE-SW direction towards north in the regions off West Bengal, Odisha, and Andhra Pradesh, and in an ~N-S direction towards south, off Tamil Nadu. Compared to the western continental margin of India, the shelf in the eastern continental margin of India is found to be irregular and narrower, with a variable width of ~120 km around Digha, ~60 km off north Andhra Pradesh and ~35 km off Tamil Nadu (Faruque et al, 2014). The water depth of the shelf break varies irregularly from ~220 to ~70 meters.…”

Resolved and Redeemed: A New Fleck to the Evolutionary Divergence in the Genus Scomberomorus Lacepède, 1801 (Scombridae) With Cryptic Speciation

“…In contrast, the east coast is an emergent coast (Swathi Lekshmi, 2020) with the Bay of Bengal receiving discharge from many east-flowing rivers, fostering larger estuaries and major deltas. The estuaries on the west coast lie mainly between Gujarat and Karnataka, while the extensive east coast estuarine system is in the stretch from West Bengal to Tamil Nadu (Faruque and Ramachandran, 2014a;Faruque et al, 2014b) (Figure 6). The intensity of the seasonal monsoons and the precipitation patterns show a great difference in the Indian subcontinent, and the latter along with other factors creates fluctuations in salinity by freshwater runoff and determines the hydrography of the aforementioned monsoonal estuaries.…”

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“…In contrast, the east coast is an emergent coast (Swathi Lekshmi, 2020) with the Bay of Bengal receiving discharge from many east-flowing rivers, fostering larger estuaries and major deltas. The estuaries on the west coast lie mainly between Gujarat and Karnataka, while the extensive east coast estuarine system is in the stretch from West Bengal to Tamil Nadu (Faruque and Ramachandran, 2014a;Faruque et al, 2014b) (Figure 6). The intensity of the seasonal monsoons and the precipitation patterns show a great difference in the Indian subcontinent, and the latter along with other factors creates fluctuations in salinity by freshwater runoff and determines the hydrography of the aforementioned monsoonal estuaries.…”