Bengal Fan Explained

The Bengal Fan, also known as the Ganges Fan, is the largest submarine fan on Earth.

Geography

It is located in the Bay of Bengal, being about 3000km (2,000miles) long, 1430km (890miles) wide with a maximum thickness of 16.5km (10.3miles).^[1] The fan resulted from the uplift and erosion of the Himalayas and the Tibetan Plateau produced by the collision between the Indian Plate and the Eurasian Plate. Most of the sediment is supplied by the Ganges and Brahmaputra rivers which supply the Lower Meghna delta in Bangladesh and the Hoogly delta in West Bengal (India). Several other large rivers in Bangladesh and India provide smaller contributions.^[2] Turbidity currents have transported the sediment through a series of submarine canyons, some of which are more than 1,500 miles (2,414 km) in length, to be deposited in the Bay of Bengal up to 30 degrees latitude from where it began. To date, the oldest sediments recovered from the Bengal fan are from Early Miocene age.^[3] Their mineralogical and geochemical characteristics confirm their Himalayan origin and demonstrate that the Himalaya was already a major mountain range 20 million years ago.^[4]

The fan completely covers the floor of the Bay of Bengal. It is bordered to the west by the continental slope of eastern India, to the north by the continental slope of Bangladesh and to east by the northern part of Sunda Trench off Myanmar and the Andaman Islands, the accretionary wedge associated with subduction of the Indo-Australian Plate beneath the Sunda Plate and continues along the west side of the Ninety East Ridge.^[5] The Nicobar Fan, another lobe of the fan, lies east of the Ninety East Ridge.

History

The fan was first identified by bathymetric survey in the sixties by Bruce C. Heezen and Marie Tharp which identified the abyssal cone and canyon structures. It was delineated and named by Joseph Curray and David Moore following a geological and geophysical survey in 1968.^{[6] [7]}

Biodiversity

A deep sea canyon called Swatch of No Ground (SoNG) is located south of Sundarbans National Park and the island of Dublar Char. This area hosts important habitats for cetaceans including endangered species such as various species of dolphins and Bryde's whales (see Swatch of No Ground Marine Protected Area).

Further reading

• Bastia. Rabi. Suman Das. M. Radhakrishna. Pre- and post-collisional depositional history in the upper and middle Bengal fan and evaluation of deepwater reservoir potential along the northeast Continental Margin of India. Marine and Petroleum Geology. October 2010. 27. 10. 2051–2061. 10.1016/j.marpetgeo.2010.04.007.
• Subrahmanyam. V.. K. S. Krishna. M. V. Ramana. K. S. R. Murthy. Marine geophysical investigations across the submarine canyon (Swatch-of-No-Ground), northern Bay of Bengal. Current Science. 2008. 94. 4. 507–513. Indian Academy of Sciences.

Notes and References

1. Shanmugam, G. . Submarine fans: A critical retrospective (1950–2015) . 2016 . Journal of Palaeogeography . 5 . 2 . 110–184 . 10.1016/j.jop.2015.08.011 . 2016JPalG...5..110S . free .
2. Curray. Joseph R.. Frans J. Emmel. David G. Moore. The Bengal Fan: morphology, geometry, stratigraphy, history and processes. Marine and Petroleum Geology. December 2002. 19. 10. 1191–1223. 10.1016/S0264-8172(03)00035-7. Elsevier Science Ltd.
3. Cochran. J.R.. Stow, D.A.V.. 116 Initial Reports Table of Contents. Proc. ODP, Init. Repts.. 1989. 116. 10.2973/odp.proc.ir.116.1989. Ocean Drilling Program College Station, TX . etal. Proceedings of the Ocean Drilling Program. Cochran. J.R. Stow. D.A.V.
4. France-Lanord. Christian. Derry L.. Michard A.. Evolution of the Himalaya since Miocene time: isotopic and sedimentological evidence from the Bengal Fan. Geological Society Special Publication. 1993. 74. 1. 603–621. 10.1144/GSL.SP.1993.074.01.40. 1993GSLSP..74..603F.
5. Book: SEPM Special Publication, No. 92. External Controls on Deep-Water Depositional Systems. 2009. SEPM (Society for Sedimentary Geology). 978-1-56576-136-0. 107–131. Tilmann Schwenk. Volkhard Spiess. Architecture and Stratigraphy of the Bengal Fan as Response to Tectonic and Climate Revealed from High-Resolution Seismic Data.
6. Web site: France-Lanord. Christian. Summary on the Bengal Fan: An introduction to a drilling proposal. Woods Hole Oceanographic Institution. Volkhard Spiess. Peter Molnar. Joseph R. Curray. March 2000. 2011-09-16. 2011-10-05. https://web.archive.org/web/20111005095805/http://www.whoi.edu/pclift/BengalSummary.pdf. dead.
7. Curray. Joseph R.. David G. Moore. Growth of the Bengal Deep-Sea Fan and Denudation in the Himalayas. Geological Society of America Bulletin. March 1971. 82. 3. 563–572. 10.1130/0016-7606(1971)82[563:GOTBDF]2.0.CO;2. 1971GSAB...82..563C.