Morphological features in the Bay of Bengal
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Bengal Fan is one of the world's largest submarine fans having an area of 2.8-3.0 xl06 sq.km. It extends from Ganges/Brahmaputra delta around 20° N latitude to south of 7° S, with a maximum width of about 1000 km around 15" N latitude. Large volume of continental sediments are being discharged by Ganges and Brahmaputra Rivers into the Bay of Bengal and the finer sediment particles reach even 7° S latitude. The sediments rest on the early Cretaceous ocean floor characterized by the Mesozoic anomalies M11 through M0. Pattern of sediment deposition, tracing the imprints of sediment movement, turbidity current flows. paleo channels, their migration in time and space and sea level fluctuations by facies identification can be used to reconstruct the development history of the Fan. After India's soft collision with the Eurasian plate, these events may have played a critical role in shaping various morphological features since late Eocene in the Bay of Bengal. The present 12 kHz Echo sounder data collected along the NW-SE trending long profiles spaced at 30 nautical miles aided to improve the bathymetry chart of the Bay of Bengal. The echograms show some important geo-morphological features of the seafloor. One such feature is the "Swatch of no ground" which resembles a deep Canyon/Channel/ valley. Several longitudinal channels appear to drain the sediments from the mighty rivers Ganges and Brahmaputra into the Bengal Fan. Levees and abandoned channels are also present on the seafloor. The eastern continental margin is characterized by narrow shelf followed by steep slope. Bathymetry in the adjacent Bengal fan varies from <500 to >4000 m. The echograms along some profiles depict an irregular and rugged topography immediately beyond the shelf break. The seafloor is very stable and smooth except few places beyond shelf break. At some locations in the distal Bengal fan, isolated local highs dominate the seafloor with a positive relief of 500 to 900 m from the mean seabed and these features are associated with positive magnetic anomalies. The newly reported bathymetric high (R) is characterized with three peaks, and associated with a positive magnetic anomaly. This positive topographic high is surrounded by abandoned channels with levees and the fan divisions.
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