The Bengal Fan: morphology, geometry, stratigraphy, history and processes

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doi: 10.1016/S0264-8172(03)00035-7
Author(s): Curray, Joseph R.; Emmel, Frans J.; Moore, David G.
Author Affiliation(s): Primary:
Scripps Institution of Oceanography, La Jolla, CA, United States
Volume Title: Marine and Petroleum Geology
Source: Marine and Petroleum Geology, 19(10), p.1191-1223. Publisher: Elsevier, Oxford, United Kingdom. ISSN: 0264-8172
Note: In English. 76 refs.; illus., incl. sects., geol. sketch maps
Summary: The Bengal Fan is the largest submarine fan in the world, with a length of about 3000 km, a width of about 1000 km and a maximum thickness of 16.5 km. It has been formed as a direct result of the India-Asia collision and uplift of the Himalayas and the Tibetan Plateau. It is currently supplied mainly by the confluent Ganges and Brahmaputra rivers, with smaller contributions of sediment from several other large rivers in Bangladesh and India. The sedimentary section of the fan is subdivided by seismic stratigraphy by two unconformities which have been tentatively dated as upper Miocene and lower Eocene by long correlations from DSDP Leg 22 and ODP Legs 116 and 121. The upper Miocene unconformity is the time of onset of the diffuse plate edge or intraplate deformation in the southern or lower fan. The lower Eocene unconformity, a hiatus which increases in duration down the fan, is postulated to be the time of first deposition of the fan, starting at the base of the Bangladesh slope shortly after the initial India-Asia collision. The Quaternary of the upper fan comprises a section of enormous channel-levee complexes which were built on top of the preexisting fan surface during lowered sea level by very large turbidity currents. The Quaternary section of the upper fan can be subdivided by seismic stratigraphy into four subfans, which show lateral shifting as a function of the location of the submarine canyon supplying the turbidity currents and sediments. There was probably more than one active canyon at times during the Quaternary, but each one had only one active fan valley system and subfan at any given time. The fan currently has one submarine canyon source and one active fan valley system which extends the length of the active subfan. Since the Holocene rise in sea level, however, the head of the submarine canyon lies in a mid-shelf location, and the supply of sediment to the canyon and fan valley is greatly reduced from the huge supply which had existed during Pleistocene lowered sea level. Holocene turbidity currents are small and infrequent, and the active channel is partially filled in about the middle of the fan by deposition from these small turbidity currents. Channel migration within the fan valley system occurs by avulsion only in the upper fan and in the upper middle fan in the area of highest rates of deposition. Abandoned fan valleys are filled rapidly in the upper fan, but many open abandoned fan valleys are found on the lower fan. A sequence of time of activity of the important open channels is proposed, culminating with formation of the one currently active channel at about 12,000 years BP. Abstract Copyright (2002) Elsevier, B.V.
Year of Publication: 2002
Research Program: DSDP Deep Sea Drilling Project
ODP Ocean Drilling Program
Key Words: 07 Marine Geology and Oceanography; Bathymetry; Bengal Fan; Cenozoic; DSDP Site 218; Deep Sea Drilling Project; Indian Ocean; Leg 116; Leg 121; Leg 22; Lithostratigraphy; Marine geology; Ocean Drilling Program; Submarine fans
Coordinates: S100000 N300000 E1100000 E0800000
Record ID: 2005002636
Copyright Information: GeoRef, Copyright 2017 American Geosciences Institute. Reference includes data from CAPCAS, Elsevier Scientific Publishers, Amsterdam, Netherlands