Marine geophysical investigations across the submarine canyon (Swatch-of-No-Ground), northern Bay of Bengal
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Date
2008Author
Subrahmanyam, V.
Krishna, K.S.
Ramana, M.V.
Murthy, K.S.R.
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Multibeam swath bathymetry, gravity and magnetic investigations were conducted across the major delta front canyon known as Swatch-of-No-Ground in the northern Bay of Bengal. The study reveals that the canyon is a 300 m deep and 18 km wide depression with step-like micro-terraces running in NNE–SSW direction. The depth to the seafloor topography varies from 900 to 1459 m with 100-150 m thick levee sediments deposited on both the edges of the canyon as seafloor swells spreading over a distance of 10-20 km. In the area north of the 20 degrees 07 minutes N lat., the canyon is characterized by a gentle step-like slope towards the western flank and a steep slope towards the eastern flank, while in the area south of the 20 degrees 07 minutes N lat., the morphology of the canyon is vice versa. The anatomy of the canyon suggests that the turbidity sediments flow in a semi-circular manner within it. When the muddy sediments strike the flank within the canyon, a part gets bounced-off in an orthogonal direction to the semicircular turbidity flow leading to the formation of step like small terraces on the other flank of the canyon. The canyon is associated with a low gravity field of about 15 mGal and weak magnetic field of the order of 30-40 nT. The model study revealed that the submarine canyon is not associated with any structural discontinuities such as faults and folds. Hence, it is surmised that the submarine canyon is a morphological feature formed by major river flow and underwater currents in the northern Bay of Bengal.
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